LCAT facilitates the removal of excess cholesterol from peripheral tissues to the liver. A lack of LCAT activity would be expected to lead to accumulation of free cholesterol in the tissues. The gene encoding LCAT on chromosome 16 is the site of the mutation in both lecithin-cholesterol acyltransferase deficiency (LCATD) (Norum disease) and fish-eye disease(FED). Two phenotypic forms are found: familial LCAT deficiency and fish-eye disease. Familial LCAT deficiency is associated with a complete absence of alpha and beta LCAT activities and results in esterification anomalies involving both HDL (alpha-LCAT activity) and LDL (beta-LCAT activity). It causes a typical triad of diffuse corneal opacities, target cell hemolytic anemia, and proteinuria with renal failure. In fish-eye disease, there is only a partial LCAT deficiency that affects only alpha-LCAT activity. It is characterized by low plasma HDL and corneal opacities due to accumulation of cholesterol deposits in the cornea ('fish-eye').there is a specific inability of LCAT to esterify cholesterol in HDL, a deficiency of alpha-LCAT function. See LCAT Mutation database
BACKGROUND: Fish-eye disease (FED) is due to a partial deficiency in LCAT activity. Nevertheless, Familial lecithin-cholesterol acyltransferase deficiency (FLD), also called Norum disease, appears when the deficiency is complete. They are both rare genetic disorders inherited in an autosomal recessive manner. Clinical signs include decreased circulating HDL cholesterol and dense corneal opacity. Kidney injuries also affect patients suffering from FLD. The diagnosis of FLD is based on the presence of characteristic signs and symptoms and confirmed by genetic testing. CASE PRESENTATION: We present a case of a 63-year-old man showing an altered lipid profile with low HDL cholesterol, chronic kidney disease (CKD) and corneal disorders. He was referred to genetic counseling in order to discard genetic LCAT deficiency due to decreased visual acuity caused by corneal opacity. A massive DNA sequencing was conducted using a multigene panel associated with lipid metabolism disturbances. RESULTS AND GENETIC FINDINGS: Two likely pathogenic variants in LCAT were identified and later confirmed by Sanger sequencing. Both (c.491sGs>sA and c.496sGs>sA) were missense variants that originated an amino acid substitution (164Arginine for Histidine and 166Alanine for Threonine, respectively) modifying the protein sequence and its 3D structure. CONCLUSIONS: FLD and FED sharing common biochemical features, and the existence of other diseases with similar clinical profiles underline the need for a timely differential diagnosis aiming to address patients to preventive programs and future available therapies. This case, added to the reduced number of publications previously reported regarding FLD and FED, contributes to better understanding the genetic characteristics, clinical features, and diagnosis of these syndromes.
The aim of this study was to evaluate the vasoprotective effects of HDL isolated from carriers of LCAT deficiency, which are characterized by a selective depletion of LpA-I:A-II particles and predominance of prebeta migrating HDL. HDLs were isolated from LCAT-deficient carriers and tested in vitro for their capacity to promote NO production and to inhibit vascular cell adhesion molecule-1 (VCAM-1) expression in cultured endothelial cells. HDLs from carriers were more effective than control HDLs in promoting eNOS activation with a gene-dose-dependent effect (PTrend = 0.048). As a consequence, NO production induced by HDL from carriers was significantly higher than that promoted by control HDL (1.63 +/- 0.24-fold vs. 1.34 +/- 0.07-fold, P = 0.031). HDLs from carriers were also more effective than control HDLs in inhibiting the expression of VCAM-1 (homozygotes, 65.0 +/- 8.6%; heterozygotes, 53.1 +/- 7.2%; controls, 44.4 +/- 4.1%; PTrend = 0.0003). The increased efficiency of carrier HDL was likely due to the depletion in LpA-I:A-II particles. The in vitro findings might explain why carriers of LCAT deficiency showed flow-mediated vasodilation and plasma-soluble cell adhesion molecule concentrations comparable to controls, despite low HDL-cholesterol levels. These results indicate that selective depletion of apoA-II-containing HDL, as observed in carriers of LCAT deficiency, leads to an increased capacity of HDL to stimulate endothelial NO production, suggesting that changes in HDL apolipoprotein composition may be the target of therapeutic interventions designed to improve HDL functionality.
Title: A novel homozygous mutation causing lecithin-cholesterol acyltransferase deficiency in a proband of Romanian origin with a record of extreme gestational hyperlipidemia Rial-Crestelo D, Santos-Recuero I, Julve J, Blanco-Vaca F, Torralba M Ref: J Clin Lipidol, 11:1475, 2017 : PubMed
A patient from Romania with extraordinarily high total cholesterol levels and clinical and biochemical features consistent with familial lecithin-cholesterol acyltransferase deficiency is reported. The genetic analysis performed on our proband showed a novel homozygous mutation on codon 119 of lecithin-cholesterol acyltransferase gene that causes the substitution of glycine by aspartate. The same mutation, also in homozygosis, was observed in her older sister, whereas his brother presented it in heterozygosis.
Familial lecithin:cholesterol acyltransferase (LCAT) deficiency is a rare inherited disorder that causes an extremely low high-density lipoprotein cholesterol concentration in serum. Recently, acquired LCAT deficiency caused by IgG antibodies to LCAT, without any LCAT gene mutation, was reported. Here we describe a case of acquired LCAT deficiency occurring in association with sarcoidosis. The patient was a Japanese female aged 70 years, had no mutation in the LCAT gene exon sequence, but had an LCAT inhibitor factor in her serum, detected using lipoprotein-deficient serum. She was diagnosed with acquired LCAT deficiency. Her abnormalities of serum lipoproteins improved spontaneously during three and a half years. Because they require different treatment strategies, distinction between familial lecithin:cholesterol acyltransferase deficiency (FLD) and acquired LCAT deficiency by gene sequencing is warranted, especially in cases without corneal clouding.
Familial lecithin-cholesterol acyltransferase (LCAT) deficiency is a rare autosomal recessive (AR) disease caused by mutation in the LCAT gene. LCAT enzyme esterifies cholesterol molecules in high-density lipoprotein(HDL) and low density-lipoprotein (LDL) particles. This enzyme deficiency is characterised by progressive corneal opacification, glomerulopathy, mild - moderate haemolytic anaemia and very low plasma levels of HDL. We here report a 34 year-old lady who presented with hypertension, nephrotic proteinuria, renal failure, corneal ring opacities, anemia and dyslipidemia. The diagnosis of familial LCAT deficiency was confirmed by clinical examination, characteristic dyslipidemia, undetectable LCAT levels in plasma and positive family history.
LCAT synthesizes most of the plasma cholesteryl esters, and plays a major role in HDL metabolism. Mutations in the LCAT gene cause two syndromes, familial LCAT deficiency (FLD) and fish-eye disease (FED), both characterized by severe alterations in plasma lipoprotein profile. Renal disease is the major cause of morbidity and mortality in FLD cases, but an established therapy is not currently available. The present therapy of LCAT deficiency is mainly aimed at correcting the dyslipidemia associated with the disease and at delaying evolution of chronic nephropathy. LCAT deficiency represents a candidate disease for enzyme replacement therapy. In vitro and in vivo studies proved the efficacy of recombinant human LCAT (rhLCAT) in correcting dyslipidemia, and rhLCAT is presently under development.
Human familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is characterized by low HDL, accumulation of an abnormal cholesterol-rich multilamellar particle called lipoprotein-X (LpX) in plasma, and renal disease. The aim of our study was to determine if LpX is nephrotoxic and to gain insight into the pathogenesis of FLD renal disease. We administered a synthetic LpX, nearly identical to endogenous LpX in its physical, chemical and biologic characteristics, to wild-type and Lcat-/- mice. Our in vitro and in vivo studies demonstrated an apoA-I and LCAT-dependent pathway for LpX conversion to HDL-like particles, which likely mediates normal plasma clearance of LpX. Plasma clearance of exogenous LpX was markedly delayed in Lcat-/- mice, which have low HDL, but only minimal amounts of endogenous LpX and do not spontaneously develop renal disease. Chronically administered exogenous LpX deposited in all renal glomerular cellular and matrical compartments of Lcat-/- mice, and induced proteinuria and nephrotoxic gene changes, as well as all of the hallmarks of FLD renal disease as assessed by histological, TEM, and SEM analyses. Extensive in vivo EM studies revealed LpX uptake by macropinocytosis into mouse glomerular endothelial cells, podocytes, and mesangial cells and delivery to lysosomes where it was degraded. Endocytosed LpX appeared to be degraded by both human podocyte and mesangial cell lysosomal PLA2 and induced podocyte secretion of pro-inflammatory IL-6 in vitro and renal Cxl10 expression in Lcat-/- mice. In conclusion, LpX is a nephrotoxic particle that in the absence of Lcat induces all of the histological and functional hallmarks of FLD and hence may serve as a biomarker for monitoring recombinant LCAT therapy. In addition, our studies suggest that LpX-induced loss of endothelial barrier function and release of cytokines by renal glomerular cells likely plays a role in the initiation and progression of FLD nephrosis.
BACKGROUND: Humans with familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) have extremely low or undetectable high-density lipoprotein cholesterol (HDL-C) levels and by early adulthood develop many manifestations of the disorder, including corneal opacities, anemia, and renal disease. OBJECTIVE: To determine if infusions of recombinant human LCAT (rhLCAT) could reverse the anemia, halt progression of renal disease, and normalize HDL in FLD. METHODS: rhLCAT (ACP-501) was infused intravenously over 1 hour on 3 occasions in a dose optimization phase (0.3, 3.0, and 9.0 mg/kg), then 3.0 or 9.0 mg/kg every 1 to 2 weeks for 7 months in a maintenance phase. Plasma lipoproteins, lipids, LCAT levels, and several measures of renal function and other clinical labs were monitored. RESULTS: LCAT concentration peaked at the end of each infusion and decreased to near baseline over 7 days. Renal function generally stabilized or improved and the anemia improved. After infusion, HDL-C rapidly increased, peaking near normal in 8 to 12 hours; analysis of HDL particles by various methods all revealed rapid sequential disappearance of prebeta-HDL and small alpha-4 HDL and appearance of normal alpha-HDL. Low-density lipoprotein cholesterol increased more slowly than HDL-C. Of note, triglyceride routinely decreased after meals after infusion, in contrast to the usual postprandial increase in the absence of rhLCAT infusion. CONCLUSIONS: rhLCAT infusions were well tolerated in this first-in-human study in FLD; the anemia improved, as did most parameters related to renal function in spite of advanced disease. Plasma lipids transiently normalized, and there was rapid sequential conversion of small prebeta-HDL particles to mature spherical alpha-HDL particles.
RATIONALE: Low high-density lipoprotein-cholesterol (HDL-C) in patients with coronary heart disease (CHD) may be caused by rate-limiting amounts of lecithin:cholesterol acyltransferase (LCAT). Raising LCAT may be beneficial for CHD, as well as for familial LCAT deficiency, a rare disorder of low HDL-C. OBJECTIVE: To determine safety and tolerability of recombinant human LCAT infusion in subjects with stable CHD and low HDL-C and its effect on plasma lipoproteins. METHODS AND RESULTS: A phase 1b, open-label, single-dose escalation study was conducted to evaluate safety, tolerability, pharmacokinetics, and pharmacodynamics of recombinant human LCAT (ACP-501). Four cohorts with stable CHD and low HDL-C were dosed (0.9, 3.0, 9.0, and 13.5 mg/kg, single 1-hour infusions) and followed up for 28 days. ACP-501 was well tolerated, and there were no serious adverse events. Plasma LCAT concentrations were dose-proportional, increased rapidly, and declined with an apparent terminal half-life of 42 hours. The 0.9-mg/kg dose did not significantly change HDL-C; however, 6 hours after doses of 3.0, 9.0, and 13.5 mg/kg, HDL-C was elevated by 6%, 36%, and 42%, respectively, and remained above baseline <=4 days. Plasma cholesteryl esters followed a similar time course as HDL-C. ACP-501 infusion rapidly decreased small- and intermediate-sized HDL, whereas large HDL increased. Pre-beta-HDL also rapidly decreased and was undetectable <=12 hours post ACP-501 infusion. CONCLUSIONS: ACP-501 has an acceptable safety profile after a single intravenous infusion. Lipid and lipoprotein changes indicate that recombinant human LCAT favorably alters HDL metabolism and support recombinant human LCAT use in future clinical trials in CHD and familial LCAT deficiency patients. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01554800.
BACKGROUND: Lecithin cholesterol acyltransferase (LCAT) is an important enzyme in cholesterol metabolism that is involved in the esterification of cholesterol. A lack of this enzyme results in deranged metabolic pathways that are not completely understood, resulting in abnormal deposition of lipids in several organs. Clinically, it manifests with proteinuria, dyslipidemia and corneal opacity with progressive chronic kidney disease resulting in end-stage renal disease. CASE PRESENTATION: We herein present a case of a 30-year-old male with proteinuria that was not responsive to empiric management with angiotensin-converting enzyme (ACE) inhibitors and oral steroids. Physical examination revealed corneal ring opacity involving both eyes. Urinalysis revealed an active sediment. The 24-h proteinuria was 3.55 grams. Family history was positive for renal disease and dyslipidemia. Viral serology for human immunodeficiency virus (HIV), hepatitis C virus (HCV) and hepatitis B virus (HBV) were negative. Serum complements were normal and anti-nuclear antibody (ANA) was negative. We elected for a renal biopsy that revealed characteristic features of LCAT deficiency. The diagnosis of LCAT deficiency was established with a combination of clinical and pathological findings. CONCLUSIONS: Currently renal prognosis is poor but conservative management with ACE inhibitors and lipid lowering therapy in addition to steroids has been shown to retard progression to end-stage renal disease. However newer therapies such as gene replacement and recombinant LCAT replacement are being studied with promising preliminary results.
Title: Co-existence of classic familial lecithin-cholesterol acyl transferase deficiency and fish eye disease in the same family Mahapatra HS, Ramanarayanan S, Gupta A, Bhardwaj M Ref: Indian J Nephrol, 25:362, 2015 : PubMed
We report a family with a rare genetic disorder arising out of mutation in the gene that encodes for the enzyme lecithin-cholesterol acyltransferase (LCAT). The proband presented with nephrotic syndrome, hemolytic anemia, cloudy cornea, and dyslipidemia. Kidney biopsy showed certain characteristic features to suggest LCAT deficiency, and the enzyme activity in the serum was undetectable. Mother and younger sister showed corneal opacity and dyslipidemia but no renal or hematological involvement. These two members had a milder manifestation of the disease called fish eye disease. This case is presented to emphasize the importance of taking family history and doing a good clinical examination in patients with nephrotic syndrome and carefully analyze the lipid fractions in these subset of patients.
BACKGROUND: Lecitin cholesterol acyltransferase (LCAT) deficiency comprises a group of rare disorders related to HDL metabolism. These disorders are characterized by ophthalmologic, hematologic, and renal findings. Case diagnosis/treatment: A 15-year-old female who presented with nephrotic syndrome and hypertension was diagnosed with LCAT deficiency by renal biopsy and LCAT enzyme activity. Her edema and hypertension improved with diuretic and antihypertensive therapies. Continued care of her LCAT deficiency is ongoing. CONCLUSION: Although rare, LCAT deficiency should be in the differential diagnosis of nephrotic syndrome in the setting of abnormally low HDL cholesterol levels.
Title: Amelioration of circulating lipoprotein profile and proteinuria in a patient with LCAT deficiency due to a novel mutation (Cys74Tyr) in the lid region of LCAT under a fat-restricted diet and ARB treatment Naito S, Kamata M, Furuya M, Hayashi M, Kuroda M, Bujo H, Kamata K Ref: Atherosclerosis, 228:193, 2013 : PubMed
Familial lecithin-cholesterol acyltransferase (LCAT) deficiency is a hereditary disease characterized by an abnormal lipid profile, corneal opacity, anemia and progressive renal disease. We report a patient with complete loss of LCAT activity due to a novel lcat gene mutation of Cys74Tyr in the lid region of LCAT protein. Esterification of cholesterol in this patient was disturbed by disruption of a substrate binding loop of Cys50-Cys74 in LCAT protein. She had progressive renal dysfunction, proteinuria, corneal opacity, anemia and an abnormal lipid profile. Her serum lipids showed a significant increase in abnormal lipoproteins at the original position in agarose gel electrophoresis and VLDL-cholesterol, and a severe decrease in serum HDL-cholesterol. Lipoprotein analyzes also revealed the presence of an abnormal midband lipoprotein, and a maturation disturbance of HDL particles. Renal function and proteinuria improved following the adoption of a fat-restricted diet and administration of an angiotensin II receptor blocker. The abnormal lipoproteins also decreased after this treatment.
Lecithin:cholesterol acyltransferase (LCAT) is the enzyme responsible for cholesterol esterification in plasma. Mutations in the LCAT gene leads to two rare disorders, familial LCAT deficiency and fish-eye disease, both characterized by severe hypoalphalipoproteinemia associated with several lipoprotein abnormalities. No specific treatment is presently available for genetic LCAT deficiency. In the present study, recombinant human LCAT was expressed and tested for its ability to correct the lipoprotein profile in LCAT deficient plasma. The results show that rhLCAT efficiently reduces the amount of unesterified cholesterol (-30%) and promotes the production of plasma cholesteryl esters (+210%) in LCAT deficient plasma. rhLCAT induces a marked increase in HDL-C levels (+89%) and induces the maturation of small prebeta-HDL into alpha-migrating particles. Moreover, the abnormal phospholipid-rich particles migrating in the LDL region were converted in normally sized LDL.
Familial LCAT deficiency (FLD) is a recessive lipid disorder ultimately leading to end-stage renal disease (ESRD). We present two brothers with considerable variation in the age at which they developed ESRD. Kidney biopsies revealed both tubular and glomerular pathology. To date, no causal therapy is available, yet enzyme replacement therapy is in development.
Lecithin-cholesterol acyltransferase (LCAT) is an enzyme involved in maintaining cholesterol homeostasis. In familial LCAT deficiency (FLD), abnormal lipid deposition causes renal injury and nephrotic syndrome, frequently progressing to ESRD. Here, we describe a 63-year-old Japanese woman with no family history of renal disease who presented with nephrotic syndrome. The laboratory data revealed an extremely low level of serum HDL and undetectable serum LCAT activity. Renal biopsy showed glomerular lipid deposition with prominent accumulation of foam cells, similar to the histologic findings of FLD. In addition, she had subepithelial electron-dense deposits compatible with membranous nephropathy, which are not typical of FLD. A mixing test and coimmunoprecipitation study demonstrated the presence of an inhibitory anti-LCAT antibody in the patient's serum. Immunohistochemistry and immunofluorescence detected LCAT along parts of the glomerular capillary walls, suggesting that LCAT was an antigen responsible for the membranous nephropathy. Treatment with steroids resulted in complete remission of the nephrotic syndrome, normalization of serum LCAT activity and HDL level, and disappearance of foam cell accumulation in renal tissue. In summary, inhibitory anti-LCAT antibody can lead to glomerular lesions similar to those observed in FLD.
The lecithin:cholesterol acyltransferase (LCAT) enzyme is responsible for the synthesis of cholesteryl esters in human plasma and plays a critical role in high density lipoprotein (HDL) metabolism. Genetic LCAT deficiency is a rare metabolic disorder characterized by low HDL cholesterol levels. This paper reviews the genetic and biochemical features of LCAT deficiency, highlighting the absence of enhanced preclinical atherosclerosis in carriers, despite the remarkably low HDL cholesterol.
BACKGROUND: Lecithin:cholesterol acyltransferase (LCAT) is responsible for cholesterol esterification in plasma. Mutations of LCAT gene cause familial LCAT deficiency, a metabolic disorder characterized by hypoalphalipoproteinemia. Apolipoprotein B (apoB) is the main protein component of very-low-density lipoproteins and low-density lipoprotein (LDL). Mutations of APOB gene cause familial hypobetalipoproteinemia, a codominant disorder characterized by low plasma levels of LDL cholesterol and apoB. OBJECTIVE: This was a genetic and biochemical analysis of an Italian kindred with hypobetalipoproteinemia whose proband presented with hypoalphalipoproteinemia and severe chronic kidney disease. METHODS: Plasma lipids and apolipoproteins, cholesterol esterification, and high-density lipoprotein (HDL) subclass distribution were analyzed. LCAT and APOB genes were sequenced. RESULTS: The proband had severe impairment of plasma cholesterol esterification and high prebeta-HDL content. He was heterozygote for the novel LCAT P406L variant, as were two other family members. The proband's wife and children presented with familial hypobetalipoproteinemia and were heterozygotes for the novel apoB H1401R variant. Cholesterol esterification rate of apoB H1401R carriers was reduced, likely attributable to the low amount of circulating LDL. After renal transplantation, proband's lipid profile, HDL subclass distribution, and plasma cholesterol esterification were almost at normal levels, suggesting a mild contribution of the LCAT P406L variant to his pretransplantation severe hypoalphalipoproteinemia and impairment of plasma cholesterol esterification. CONCLUSION: LCAT P406L variant had a mild effect on lipid profile, HDL subclass distribution, and plasma cholesterol esterification. ApoB H1401R variant was identified as possible cause of familial hypobetalipoproteinemia and resulted in a reduction of cholesterol esterification rate.
We recently reported that lecithin:cholesterol acyltransferase (LCAT) knock-out mice, particularly in the LDL receptor knock-out background, are hypersensitive to insulin and resistant to high fat diet-induced insulin resistance (IR) and obesity. We demonstrated that chow-fed Ldlr-/-xLcat+/+ mice have elevated hepatic endoplasmic reticulum (ER) stress, which promotes IR, compared with wild-type controls, and this effect is normalized in Ldlr-/-xLcat-/- mice. In the present study, we tested the hypothesis that hepatic ER cholesterol metabolism differentially regulates ER stress using these models. We observed that the Ldlr-/-xLcat+/+ mice accumulate excess hepatic total and ER cholesterol primarily attributed to increased reuptake of biliary cholesterol as we observed reduced biliary cholesterol in conjunction with decreased hepatic Abcg5/g8 mRNA, increased Npc1l1 mRNA, and decreased Hmgr mRNA and nuclear SREBP2 protein. Intestinal NPC1L1 protein was induced. Expression of these genes was reversed in the Ldlr-/-xLcat-/- mice, accounting for the normalization of total and ER cholesterol and ER stress. Upon feeding a 2% high cholesterol diet (HCD), Ldlr-/-xLcat-/- mice accumulated a similar amount of total hepatic cholesterol compared with the Ldlr-/-xLcat+/+ mice, but the hepatic ER cholesterol levels remained low in conjunction with being protected from HCD-induced ER stress and IR. Hepatic ER stress correlates strongly with hepatic ER free cholesterol but poorly with hepatic tissue free cholesterol. The unexpectedly low ER cholesterol seen in HCD-fed Ldlr-/-xLcat-/- mice was attributable to a coordinated marked up-regulation of ACAT2 and suppressed SREBP2 processing. Thus, factors influencing the accumulation of ER cholesterol may be important for the development of hepatic insulin resistance.
A number of epidemiological and clinical studies have demonstrated that plasma high-density lipoprotein (HDL) level is a strong inverse predictor of cardiovascular events. HDL is believed to retard the formation of atherosclerotic lesions by removing excess cholesterol from cells and preventing endothelial dysfunction. Lecithin cholesterol acyltransferase (LCAT) plays a central role in the formation and maturation of HDL, and in the intravascular stage of reverse cholesterol transport: a major mechanism by which HDL modulates the development and progression of atherosclerosis. A defect in LCAT function would be expected to enhance atherosclerosis, by interfering with the reverse cholesterol transport step. As such, one would expect to find more atherosclerosis and cardiovascular events in LCAT-deficient patients. But this relationship is not always evident. In this review, we describe contradictory reports in the literature about cardiovascular risks in this patient population. We discuss the paradoxical finding of severe HDL deficiency and an absence of subclinical atherosclerosis in LCAT-deficient patients, which has been used to reject the hypothesis that HDL level is important in the protection against atherosclerosis. Furthermore, to illustrate this paradoxical finding, we present a case study of one patient, referred for evaluation of global cardiovascular risk in the presence of a low HDL cholesterol level, who was diagnosed with LCAT gene mutations.
A genetic mendelian autosomal recessive condition of deficiency of lecithin- cholesterol acyltransferase (LCAT) can produce two different diseases: one highly interesting nephrologic picture of complete enzymatic deficiency (lecithin:cholesterol acyltransferase deficiency; OMIM ID #245900; FLD), characterized by the association of dyslipidemia, corneal opacities, anemia and progressive nephropathy; and a partial form (fish eye disease; OMIM ID #136120; FED) with dyslipidemia and progressive corneal opacities only. The diagnosis of FLD falls first of all under the competence of nephrologists, because end-stage renal disease appears to be its most severe outcome. The diagnostic suspicion is based on clinical signs (corneal opacities, more severe anemia than expected for the degree of chronic renal failure, progressive proteinuric nephropathy) combined with histology obtained by kidney biopsy (glomerulopathy evolving toward sclerosis with distinctive lipid deposition). However, the final diagnosis, starting with a finding of extremely low levels of HDL-cholesterol, requires collaboration with lipidology Centers that can perform sophisticated investigations unavailable in common laboratories. To be heterozygous for a mutation of the LCAT gene is one of the monogenic conditions underlying primary hypoalphalipoproteinemia (OMIM ID #604091). This disease, which is characterized by levels of HDL-cholesterol below the 5th percentile of those of the examined population (<28 mg/dL for Italians), has heritability estimates between 40% and 60% and is considered to be a predisposing condition for coronary artery disease. Nevertheless, some monogenic forms, and especially those associated with LCAT deficiency, seem to break the rule, confirming once more the value of a proper diagnosis before drawing prognostic conclusions from a laboratory marker. As in many other rare illnesses, trying to discover all the existing cases will contribute to allow studies broad enough to pave the way for further therapies, in this case also fostering the production by industries of the lacking enzyme by genetic engineering. Epidemiological studies, although done on selected populations such as hypoalphalipoproteinemia patients on dialysis and with the effective genetic tools of today, have been disappointing in elucidating the disease. Spreading the clinical knowledge of the disease and its diagnostic course among nephrologists seems to be the best choice, and this is the aim of our work.
INTRODUCTION: Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare recessive disorder of cholesterol metabolism characterized by the absence of high density lipoprotein (HDL) and the triad of corneal opacification, hemolytic anemia and glomerulopathy. PATIENTS: We here report on FLD in three siblings of a kindred of Moroccan descent with HDL deficiency. In all cases (17, 12 and 3 years of age) corneal opacification and proteinuria were observed. In the 17-year-old female proband, anemia with target cells was observed. RESULTS: Homozygosity for a mutation in LCAT resulted in the exchange of cysteine to tyrosine at position 337, disrupting the second disulfide bond in LCAT. LCAT protein and activity were undetectable in the patients' plasma and in media of COS7 cells transfected with an expression vector with mutant LCAT cDNA. Upon treatment with an ACE inhibitor and a thiazide diuretic, proteinuria in the proband decreased from 6g to 2g/24h. CONCLUSION: This is the first report that FLD can cause nephropathy at a very early age.
Familial lecithin:cholesterol acyltransferase deficiency (FLD) is an autosomal recessive disorder characterized by corneal opacity, hemolytic anemia, low high-density lipoprotein cholesterol (HDL-C) and proteinuria. Two novel lecithin:cholesterol acyltransferase (LCAT) mutations[c.278 C>T (p.Pro69Leu); c.950 T>C (p.Met293Thr)] were identified in a 27-year-old man and in a 30-year-old woman, respectively. Both patients manifested corneal opacity, hemolytic anemia, low low-density lipoprotein cholesterol and HDL-C and proteinuria. Lipid deposits with vacuolar lucent appearance in glomerular basement membranes were observed in both cases. APOE genotype was also investigated: the first case results 4/3, the second 2/2; however, they shared a similar phenotype characterized by the presence of intermediate-density lipoproteins (IDL) remnant and the absence of lipoprotein-X. In conclusion, our findings suggest that APOE 2/2 may not be the major determinant gene for the appearance of IDL in FLD patients.
Familial lecithin-cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare genetic disorder of lipid metabolism, characterised by low plasma HDL cholesterol, proteinuria, haemolytic anaemia and corneal opacities. Usually renal disease progresses during the third decade of life to renal failure; however the pathogenesis of renal disease is not well understood. In this study we describe treatment of renal disease in two siblings with FLD. The proband WX at the age of 31 years presented proteinuria and ankle oedema during her third pregnancy. Diagnosis of FLD was based on a renal biopsy with characteristic serpiginous fibrillar deposits under electron microscopy, markedly decreased HDL cholesterol, esterified cholesterol levels and LCAT activity, confirmed by molecular analysis. After 3 years her proteinuria increased and she received an ACE inhibitor to which she responded well. During further increases of proteinuria she additionally received methylprednisolone and her proteinuria decreased. This long-term observation indicates the efficacy of corticosteroids and renin-angiotensin-aldosterone system blockers in the treatment of proteinuria in patients with FLD. The results suggest the role of inflammatory processes as well as dyslipidemia in the pathogenesis of glomerular disorders in LCAT-deficient patients.
BACKGROUND: A case of homozygous familial lecithin:cholesterol acyltransferase (LCAT) deficiency with a novel homozygous LCAT missense mutation (replacement of methionine by arginine at position 293 in the amino acid sequence of the LCAT protein) is reported. METHODS AND RESULTS: The probable diagnosis was suggested by findings of marked high density lipoprotein (HDL) deficiency, corneal opacification, anemia, and renal insufficiency. The diagnosis was confirmed by two dimensional gel electrophoresis of HDL, the measurement of free and esterified cholesterol, and sequencing of the LCAT gene. CONCLUSIONS: In our view the most important aspects of therapy to prevent the kidney disease that these patients develop is careful control of blood pressure and lifestyle measures to optimize non HDL lipoproteins. In the future replacement therapy by gene transfer or other methods may become available.
Familial lecithin-cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare genetic disease characterized by corneal opacities, normocytic anemia, dyslipidemia, and proteinuria progressing to chronic renal failure. In all FLD cases, a mutation has been found in the coding sequence of the LCAT gene. FLD is clinically distinguished from an acquired form of LCAT deficiency by the presence of corneal opacities. Here we describe a 36-year-old woman presenting with clinical, pathological, and laboratory data compatible with FLD. Her mother and elder sister had corneal opacities. However, genetic analysis revealed there were no mutations in the LCAT coding sequences and no alterations in LCAT mRNA expression. Furthermore, we were unable to find any underlying conditions that may lead to LCAT deficiency. The present case therefore demonstrates that LCAT deficiency may be caused by factors other than mutations in the coding sequence and we suggest that a translational or posttranslational mechanism may be involved.
Title: Lecithin: Cholesterol Acyltransferase (LCAT) Deficiency: renal lesions with early graft recurrence Strom EH, Sund S, Reier-Nilsen M, Dorje C, Leren TP Ref: Ultrastruct Pathol, 35:139, 2011 : PubMed
Familial lecithin:cholesterol acyltransferase (LCAT) deficiency is a rare metabolic disease with lipid deposition in several organs. The authors report a man with hypertension and proteinuria. Renal biopsy revealed glomerular changes, including peculiar thrombus-like deposits, consistent with LCAT deficiency. He was found to be compound heterozygous for two mutations of the LCAT gene. He received a kidney graft from his father. The authors also describe LCAT deficiency-related lesions in the explanted native kidneys and in biopsies at 2 days, 6 weeks, and 1 year after transplantation. The morphology of this disease is characteristic, and the diagnosis should be suspected from the ultrastructural findings.
We trace the 34-year history of a member of the first Japanese family in which lecithin-cholesterol acyltransferase (LCAT) deficiency was diagnosed. Marriage between cousins with low LCAT activity was responsible for familial LCAT deficiency (FLD). In 1976, a 27-year-old Japanese man was noted to have FLD based on proteinuria, hematuria, grayish corneal opacity and low LCAT activity (9.83%). Genetic analysis showed insertion of G-G-C coding glycine at codon 141. Total cholesterol (C) was low at 108 mg/dl and the ratio of C-ester to total C was very low (12%), while the lecithin (phosphatidylcholine) level was very high (97.3%). When his serum creatinine reached 2.6 mg/dl at the age of 41 years (in 1991), renal biopsy was performed. This showed expansion of the mesangial matrix and irregularly thickened capillary walls with a bubble-like appearance because of lipid deposits consisting of two components (partly lucent vacuolated areas and partly deeply osmiophilic areas). Magnification of the latter deposits showed curvilinear and serpiginous striated membranous structure. Hemodialysis was started in 1990 and has been continued for over 20 years until August 2010. Clinical problems have included AV shunt failure requiring 4 operations and 13 percutaneous transcatheter angioplasty procedures, as well as episodes of hemolytic anemia that subsided after infusion of fresh frozen plasma. Cardiovascular events have not yet occurred, although severe calcification of abdominal aorta has been detected by computed tomography.
Lecithin-cholesterol acyltransferase (LCAT) is an important enzyme involved in the esterification of cholesterol. Here, we report a novel point mutation in the LCAT gene of a 63-year-old female with characteristics of classic familial LCAT deficiency. The patient's clinical manifestations included corneal opacity, mild anemia, mild proteinuria and normal renal function. She had no sign of coronary heart disease. Her LCAT activity was extremely low. DNA sequencing revealed a point mutation in exon 5 of the LCAT gene: a G to C substitution converting Gly(179) to an Arg, located in one of the catalytic triads of the enzyme. In vitro expression of recombinant LCAT proteins in HEK293 cells showed that the mutant G179R protein was present in the cell lysate, but not the culture medium. LCAT activity was barely detectable in the cell lysate or medium of the cells expressing the G179R mutant. This novel missense mutation seems to cause a complete loss of catalytic activity of LCAT, which is also defective in secretion.
Familial lecithin: cholesterol acyltransferase (LCAT) deficiency is an autosomal recessive disorder characterized by corneal opacity, hemolytic anemia, proteinuria, and a low serum level of high-density lipoprotein cholesterol (HDL-C). Also, LCAT activity is remarkably decreased or absent. A 57-year-old Japanese man presented with corneal opacity, proteinuria, and a very low serum level of HDL-C. His LCAT activity was too low to measure. From clinical observations and results of examinations, we suspected LCAT deficiency. We performed a kidney biopsy and gene analysis. Light microscopy revealed the vacuolation of glomerular capillary tufts. Electron microscopy revealed small deposits in the glomerular basement membrane (GBM), extracellular matrix, and vascular endothelial cells. We identified a homozygous C to T point mutation at nucleotide 501 (g.501 C>T) of exon 4 at codon 140, resulting in an arginine (Arg) to cysteine (Cys) amino acid substitution (R140C) in the patient. These findings were characteristic of LCAT deficiency, which was confirmed to be due to a mutation that has only been reported in Japan.
Title: Characterization of a new LCAT mutation causing familial LCAT deficiency (FLD) and the role of APOE as a modifier gene of the FLD phenotype Baass A, Wassef H, Tremblay M, Bernier L, Dufour R, Davignon J Ref: Atherosclerosis, 207:452, 2009 : PubMed
Familial LCAT deficiency (FLD) is a disease characterized by a defect in the enzyme lecithin:cholesterol acyltransferase (LCAT) resulting in low HDL-C, premature corneal opacities, anemia as well as proteinuria and renal failure. We have identified the first French Canadian kindred with familial LCAT deficiency. Two brothers, presenting classical signs of FLD, were shown to be homozygous for a novel LCAT mutation. This c.102delG mutation occurs at the codon for His35 and causes a frameshift that stops transcription at codon 61 abolishing LCAT enzymatic activity both in vivo and in vitro. It has a dramatic effect on the lipoprotein profile, with an important reduction of HDL-C in both heterozygotes (22%) and homozygotes (88%) and a significant decrease in LDL-C in heterozygotes (35%) as well as homozygotes (58%). Furthermore, the lipoprotein profile differs markedly between the two affected brothers who had different APOE genotypes. We propose that APOE could be an important modifier gene explaining heterogeneity in lipoprotein profiles observed among FLD patients. Our results suggest that a LCAT-/- genotype associated with an APOE epsilon2 allele could be a novel mechanism leading to dysbetalipoproteinemia.
Title: Two novel frame shift mutations in lecithin:cholesterol acyltransferase (LCAT) gene associated with a familial LCAT deficiency phenotype Park CW, Lim MH, Youn DY, Jung SE, Chung S, Ahn YS, Chang YS, Lee JH Ref: Atherosclerosis, 206:346, 2009 : PubMed
BACKGROUND: The lecithin:cholesterol acyltransferase (LCAT) gene is located on the long arm of chromosome 16 and encodes a highly conserved enzyme that catalyzes the formation of most plasma lipoprotein cholesteryl esters. Two autosomal recessive disorders, familial LCAT deficiency (FLD) and fish eye disease, are associated with germline LCAT mutations. Patients with FLD and fish-eye disease frequently present with corneal opacity, anemia and renal failure with proteinuria. METHODS: We clinically and biochemically characterized a German patient with classical FLD and used molecular genetic analysis to identify a novel homozygous LCAT mutation within codon 178. RESULTS: The insertion of adenine identified is located in one of the two motifs that resemble sequences found in several lipases, and results in a frameshift with a stop codon at residue 214. Therefore, the mutation alters a large portion of the LCAT enzyme, including both protein regions with putative lipase activity. Clinically, the female patient presented with corneal opacity, mild anemia and a slow deterioration in kidney function that led to a requirement for hemodialysis until she received a renal transplant. CONCLUSIONS: The present data provide additional insights into the genotype/phenotype correlations of FLD and thus may improve the genetic diagnosis of this interesting inborn error of metabolism.
Title: Stability of lipids on peritoneal dialysis in a patient with familial LCAT deficiency Weber CL, Frohlich J, Wang J, Hegele RA, Chan-Yan C Ref: Nephrol Dial Transplant, 22:2084, 2007 : PubMed
OBJECTIVE: To better understand the role of lecithin:cholesterol acyltransferase (LCAT) in lipoprotein metabolism through the genetic and biochemical characterization of families carrying mutations in the LCAT gene. METHODS AND RESULTS: Thirteen families carrying 17 different mutations in the LCAT gene were identified by Lipid Clinics and Departments of Nephrology throughout Italy. DNA analysis of 82 family members identified 15 carriers of 2 mutant LCAT alleles, 11 with familial LCAT deficiency (FLD) and 4 with fish-eye disease (FED). Forty-four individuals carried 1 mutant LCAT allele, and 23 had a normal genotype. Plasma unesterified cholesterol, unesterified/total cholesterol ratio, triglycerides, very-low-density lipoprotein cholesterol, and pre-beta high-density lipoprotein (LDL) were elevated, and high-density lipoprotein (HDL) cholesterol, apolipoprotein A-I, apolipoprotein A-II, apolipoprotein B, LpA-I, LpA-I:A-II, cholesterol esterification rate, LCAT activity and concentration, and LDL and HDL3 particle size were reduced in a gene-dose-dependent manner in carriers of mutant LCAT alleles. No differences were found in the lipid/lipoprotein profile of FLD and FED cases, except for higher plasma unesterified cholesterol and unesterified/total cholesterol ratio in the former. CONCLUSIONS: In a large series of subjects carrying mutations in the LCAT gene, the inheritance of a mutated LCAT genotype causes a gene-dose-dependent alteration in the plasma lipid/lipoprotein profile, which is remarkably similar between subjects classified as FLD or FED.
Heritable variation in complex traits is generally considered to be conferred by common DNA sequence polymorphisms. We tested whether rare DNA sequence variants collectively contribute to variation in plasma levels of high density lipoprotein cholesterol (HDL-C). We sequenced three candidate genes (ABCA1, APOA1, and LCAT) that cause Mendelian forms of low HDL-C levels in individuals from a population-based study. Nonsynonymous sequence variants were significantly more common (16% versus 2%) in individuals with low HDL-C (95th percentile). Similar findings were obtained in an independent population, and biochemical studies indicated that most sequence variants in the low HDL-C group were functionally important. Thus, rare alleles with major phenotypic effects contribute significantly to low plasma HDL-C levels in the general population.
Primary hyperlipidemia is caused by various molecular defects in lipid metabolism. The Research Committee on Primary Hyperlipidemia organized by the Ministry of Health and Welfare of Japan (present: the Ministry of Health, Labour and Welfare) has investigated reported mutations in Japanese patients with primary hyperlipidemia and related disorders (including hypolipidemia), and has created a database based on the questionnaire sent to the members of council board of the Japan Atherosclerosis Society. Mutations in the following genes were investigated: low density lipoprotein receptor, lecithin: cholesteryl acyltransferase, lipoprotein lipase (LPL), hepatic lipase, apolipoproteins A-I, A-II, A-IV, B, C-II, C-III and E, microsomal triglyceride transfer protein, and cholesterol ester transfer protein (CETP). Until 1998, 922 patients with primary hyperlipidemia and related disorders has been registered with the Research Committee, and 190 mutations in 15 genes had been reported, showing a marked variation in Japanese patients with primary hyperlipidemia and related disorders. So-called "common mutations" have been described in Japanese patients with familial hypercholesterolemia, LPL deficiency and CETP deficiency. The genetic defect of familial combined hyperlipidemia (FCHL) is still unknown although FCHL is speculated to be the most prevalent genetic hyperlipidemia, and further investigations should be performed to elucidate the molecular mechanisms of FCHL
We studied a four-generation family (17 subjects) with familial lecithin:cholesterol acyltransferase (LCAT) deficiency. A 30-year-old Caucasian male with corneal clouding and HDL cholesterol <0.1 mmol/l was a compound heterozygote for a novel mutation (Phe(382)-->Val), a previously reported mutation (Thr321-->Met) and a common variant (Thr208-->Ser) of the gene. Immunoreactive LCAT concentration (1.2 microg/ml), alpha-LCAT activity (13 nmol/ml per h) and cholesterol esterification rate (CER) (14 nmol/ml per h) in his plasma were, respectively, 14, 8 and 14% of the mean values in healthy subjects. The proband and 13 of his relatives also had familial defective apo B (FDB, Arg3500-->Gln). Six subjects had LCAT Phe382-->Val in combination with FDB. Plasma lipoprotein(a) (Lp(a)) was 24 nmol/l in the proband and 46-211 nmol/l in his father and siblings, consistent with expression of the 16 kringle 4 isoform. The proband had no signs of coronary heart disease (CHD), but his father, a paternal uncle and a female cousin had CHD before age 38 years.
Hypoalphalipoproteinemia (HALP) is a dyslipidemia characterized by low HDL-cholesterol (HDL-C) levels with important genetic contribution. However, no common genetic mutations have been found to be associated with this disorder. We screened the promoter and coding sequence of apolipoprotein (apo) A-I and lecithin:cholesterol acyltransferase (LCAT) genes and the 5' apo C-III region by SSCP and heteroduplex analysis, and DNA sequencing in 66 unrelated subjects with recurrent low HDL-C levels. We also analyzed the N370S and L444P variants, in the glucocerebrosidase (GBA) gene by restriction fragment analysis. Three mutations in the apo A-I gene (L144R, W108R, g.1833C>T) and 3 mutations in the LCAT gene (S208T, I178T, IVS3-23C>A) were detected, in six heterozygous subjects. In addition, a novel polymorphic site in LCAT gene (g.4886C>T) has been identified. Allelic frequencies of polymorphisms g.(-636)C>A, g.(-625)G>A, g.(-620)T>del, g.(-479C>T and g.(-452)T>C, located upstream of the apo C-III gene, were in normal range, and no other mutation was found in this region. Two HALP subjects were found to carry the N370S mutation at GBA locus. In conclusion, 12% of HALP subjects were found to carry mutations in apo A-I, LCAT, or GBA genes, which could explain this phenotype. Our results confirm the molecular, genetic and phenotypic heterogeneity of HALP.
Title: Genetic and environmental determinants of plasma high density lipoprotein cholesterol and apolipoprotein AI concentrations in healthy middle-aged men Talmud PJ, Hawe E, Robertson K, Miller GJ, Miller NE, Humphries SE Ref: Ann Hum Genet, 66:111, 2002 : PubMed
The effects of common variants of cholesteryl ester transfer protein (CETP) (TaqIB), hepatic lipase (HL) (-514C>T), lipoprotein lipase (LPL) (S447X) and lecithin cholesterol acyl transferase (LCAT) (S208T) on the determination of high density lipoprotein cholesterol (HDL-C) and apolipoprotein AI (apoAI) levels were examined in 2773 healthy middle-aged men participating in the second Northwick Park Heart Study. The extent of gene:gene, gene:smoking and gene:alcohol interactions were determined. For HDL-C levels, only CETP genotype was associated with significant effects (p&0.0001), with the B2 allele being associated with higher levels in both smokers and non-smokers. This interaction was significant at the lowest tertile of TG, suggesting that TG levels were rate limiting. As previously reported, CETP, LPL and HL genotypes were all associated with significant effects on apoAI levels (all p&0.01), with carriers of the rare alleles having higher levels and with no evidence of heterogeneity of effects in smokers and non-smokers. LCAT genotype was not associated with significant effects on either trait. There was no significant interaction between any of the genotypes and alcohol consumption on either HDL-C or apoAI levels. All genotypic effects were additive for HDL-C and apoAI. Environmental and TG levels explained more than 20% and 5.5% of the variance in HDL-C and apoAI, respectively. The novel aspect of this finding is that genetic variation at these loci explained in total only 2.5% of the variance in HDL-C and 1.89% of the variance in apoAI levels. Thus despite the key roles played by these enzymes in HDL metabolism, variation at these loci, at least as detected by these common genotypes, contributes minimally to the variance in HDL-C and apoAI levels in healthy men, highlighting the polygenic and multifactorial control of HDL-C.
Title: A novel TC deletion resulting in Pro(260)-->Stop in the human LCAT gene is associated with a dominant effect on HDL-cholesterol Kasid A, Rhyne J, Zeller K, Pritchard H, Miller M Ref: Atherosclerosis, 156:127, 2001 : PubMed
Human lecithin:cholesterol acyltransferase (LCAT) plays a key role in the biogenesis of circulating high-density lipoprotein-cholesterol (HDL-C) and reverse cholesterol efflux. We investigated the molecular defect in the LCAT gene in a family with low levels of HDL-C. The proband, a 53-year-old woman from Oklahoma City, had a HDL-C level of 0.21 mmol/l. The LCAT activity in the proband was 5 nmol/ml/h and cholesterol esterification rate was 54.2 nmol/ml/h, consistent with LCAT deficiency. Analysis of polymerase chain reaction (PCR) amplified subgenomic fragments of LCAT DNA on polyacrylamide gels revealed heteroduplex bands in the proband and three other affected individuals in exon 6. DNA sequence analyses of the proband's LCAT gene identified a 2 base pair deletion (TC) (base pairs 4544-4545, corresponding to amino acid 255) in the heteroduplex allele, thereby converting Pro(260) to a premature stop codon and a predicted truncated protein of 260 amino acids. This is approximately 60% of the length of the normal translated protein. The heterozygous individuals also revealed significant reduction in apolipoprotein A-1 levels compared with the unaffected family members (n=4). The marked reduction in HDL-C in the proband and sibling suggests a dominant effect of this mutation on HDL-C levels. Furthermore, because the deletion results in a heterozygous allele that can be detected by a simple PCR reaction and polyacrylamide gel-size fractionation, it may be possible to rapidly screen susceptible individuals for the presence of this mutation.
Patients with familial lecithin-cholesterol acyltransferase (LCAT) deficiency very often show progressive glomerulosclerosis with evolution to end-stage disease. High levels of an abnormal lipoprotein (lipoprotein X) cause glomerular capillary endothelial damage. The ultrastructural study of renal biopsy specimens shows characteristic glomerular deposits of membrane-like, cross-striated structures and vacuole structures. The gene encoding for LCAT has been mapped to chromosome 16q22.1, and several mutations of this gene cause LCAT deficiency which is inherited as an autosomal recessive trait and which is characterized by corneal opacities, normochromic normocytic anemia, and renal dysfunction. Herein we report clinical features and renal histological findings concerning a 24-year-old male patient with classical familial LCAT deficiency due to two different allelic mutations: a nonsense mutation inherited from the father and a missense mutation inherited from the mother. Moreover, the patient showed glomerular histological lesions and an immunofluorescent glomerular pattern typical of hypocomplementemic membranoproliferative type II glomerulonephritis (dense-deposit disease). The nature of electron-dense material that characterizes dense-deposit disease is still unknown, but there are suggestions that some chemical modifications might occur in the renal basement membranes. Therefore, this clinical case might induce to consider possible relations between disorders of the lipoprotein metabolism and renal dense-deposit disease.
Title: A common lecithin: cholesterol acyltransferase gene variant (Ser208-->Thr) Stocks J, Cooke CJ, Miller NE Ref: Atherosclerosis, 149:219, 2000 : PubMed
A molecular model was built for human lecithin:cholesterol acyltransferase (LCAT) based upon the structural homology between this enzyme and lipases (Peelman et al. 1998. Prot. Sci. 7: 585-597). We proposed that LCAT belongs to the alpha/beta hydrolase fold family, and that the central domain of LCAT consists of a mixed seven-stranded beta-pleated sheet with four alpha-helices and loops linking the beta-strands. The catalytic triad of LCAT was identified as Asp345 and His377, as well as Ser181. This model is used here for the interpretation of the structural defects linked to the point mutations identified in LCAT, which cause either familial LCAT deficiency (FLD) or fish-eye disease (FED). We show that these mutations occur in separate domains of the 3D structure of the enzyme. Most mutations causing familial LCAT deficiency are either clustered in the vicinity of the catalytic triad or affect conserved structural elements in LCAT. Most mutations causing fish-eye disease are localized on the outer hydrophilic surface of the amphipathic helical segments. These mutations affect only minimally the overall structure of the enzyme, but are likely to impair the interaction of the enzyme with its co-factor and/or substrate.
Title: Classical LCAT deficiency resulting from a novel homozygous dinucleotide deletion in exon 4 of the human lecithin: cholesterol acyltransferase gene causing a frameshift and stop codon at residue 144 Teh EM, Chisholm JW, Dolphin PJ, Pouliquen Y, Savoldelli M, De Gennes JL, Benlian P Ref: Atherosclerosis, 146:141, 1999 : PubMed
Lecithin: cholesterolacyltransferase (LCAT) transacylates the fatty acid at the sn-2 position of lecithin to the 3beta-OH group of cholesterol forming lysolecithin and the majority of cholesteryl ester found in plasma. LCAT participates in the reverse cholesterol transport pathway in man where it esterifies tissue-derived cholesterol following efflux from peripheral cells into HDL. Only 38 unique mutations in the human LCAT gene have been reported worldwide. Our French female proband presented with corneal opacity and no detectable plasma LCAT activity using either endogenous or exogenous assays. Her total plasma cholesterol and HDL cholesterol were low (2.34 mmol/l and 0.184 mmol/l, respectively) with a very high cholesterol/cholesteryl ester molar ratio (10.9:1). Plasma triglycerides were 0.470 mmol/l with low apo B (40.5 mg/dl), apo A-I (14.7 mg/dl), apo A-II (6.8 mg/dl) and apo E (2.1 mg/dl) levels. Plasma lipoprotein analysis by ultracentrifugation showed very low HDL concentrations and a characteristic shift of the lipoprotein profile towards larger, less dense particles. No proteinuria, renal dysfunction or signs of atherosclerosis were noted at age 45. Sequence analysis of her LCAT gene showed a novel homozygous TG-deletion at residues 138-139 that resulted in a frameshift causing the generation of a stop codon and premature termination of the LCAT protein at amino acid residue 144. Western blotting of the patient's plasma using a polyclonal IgY primary antibody against human LCAT failed to demonstrate the presence of a truncated LCAT protein. A 53 bp mismatched PCR primer was designed to generate an Fsp 1 restriction site in the wild type sequence of exon 4 where the mutation occurred. The 155 bp PCR product from the wild type allele produced a 103 bp and 52 bp fragment with Fsp 1 and no cleavage products with the mutant allele thus permitting rapid screening for this novel mutation.
Two novel mutations were identified in a compound heterozygous male with lecithin:cholesterol acyltransferase (LCAT) deficiency. Exon sequence determination of the LCAT gene of the proband revealed two novel heterozygous mutations in exons one (C110T) and six (C991T) that predict non-conservative amino acid substitutions (Thr13Met and Pro307Ser, respectively). To assess the distinct functional impact of the separate mutant alleles, studies were conducted in the proband's 3-generation pedigree. The compound heterozygous proband had negligible HDL and severely reduced apolipoprotein A-I, LCAT mass, LCAT activity, and cholesterol esterification rate (CER). The proband's mother and two sisters were heterozygous for the Pro307Ser mutation and had low HDL, markedly reduced LCAT activity and CER, and the propensity for significant reductions in LCAT protein mass. The proband's father and two daughters were heterozygous for the Thr13Met mutation and also displayed low HDL, reduced LCAT activity and CER, and more modest decrements in LCAT mass. Mean LCAT specific activity was severely impaired in the compound heterozygous proband and was reduced by 50% in individuals heterozygous for either mutation, compared to wild type family members. It is also shown that the two mutations impair both catalytic activity and expression of the circulating protein.
We report the molecular diagnosis of a lecithin : cholesterol acyltransferase deficiency in a 12-year old proband with a high-density lipoprotein deficiency. The increased percentage of free cholesterol in plasma and high-density lipoprotein indicated an inherited lecithin : cholesterol acyltransferase deficiency as the underlying cause. This diagnosis was confirmed by a low plasma lecithin : cholesterol acyltransferase activity and a combination of genetic analyses which demonstrated compound heterozygosity for two mutations in the lecithin : cholesterol acyltransferase gene of the proband. One was a previously unreported 2 bp deletion leading to a stop signal in codon 77 and the other a point mutation causing Arg 135-->Gln transition. To our knowledge, this is the first diagnosis of lecithin : cholesterol acyltransferase deficiency in a pre-symptomatic patient. Whether the proband will develop signs of complete lecithin : cholesterol acyltransferase deficiency or the milder form (Fish Eye Disease) is uncertain, although the former possibility is more likely. The risk of premature atherosclerosis conferred by lecithin : cholesterol acyltransferase deficiency is not well established. The proband will need to be carefully monitored in the future.
Title: Molecular genetic study of Finns with hypoalphalipoproteinemia and hyperalphalipoproteinemia: a novel Gly230 Arg mutation (LCAT[Fin]) of lecithin:cholesterol acyltransferase (LCAT) accounts for 5% of cases with very low serum HDL cholesterol levels Miettinen HE, Gylling H, Tenhunen J, Virtamo J, Jauhiainen M, Huttunen JK, Kantola I, Miettinen TA, Kontula K Ref: Arterioscler Thromb Vasc Biol, 18:591, 1998 : PubMed
In an attempt to identify genetic factors underlying extreme alterations of serum HDL cholesterol (HDL-C) concentrations, we examined two probands with HDL-C levels <0.2 mmol/L and subsequently screened two large cohorts of smoking men, one with very low (0.2 to 0.7 mmol/L, n=156) and the other with elevated (1.9 to 3.6 mmol/L, n=160) HDL-C levels, for the newly detected mutations as well as some other mutations proposed to affect HDL-C levels. One of the probands had corneal opacities, microalbuminuria, hypertriglyceridemia, and reduced LDL apoprotein B concentration; the other had anemia and presented with stomatocytosis in his peripheral blood. The first proband was found to be homozygous for a novel LCAT Gly230Arg (LCAT[Fin]) mutation, and the second was homozygous for an Arg399Cys mutation we described previously. Transient expression of the mutant LCAT(Fin) cDNA in COS cells disclosed markedly diminished LCAT enzyme activity. In the low-HDL-C group of men (n=156), 8 carriers of LCAT(Fin) and 1 carrier of the LCAT Arg399Cys were identified. In addition, the frequency of the lipoprotein lipase (LPL) Asn291Ser mutation was significantly (P<.05) higher in the low-HDL-C group (4.8%) than in the high-HDL-C group (1.6%). In addition, we identified 1 carrier of the intron 14G-->A mutation of cholesterol ester transfer protein (CETP) in the high-HDL-C group and subsequently demonstrated cosegregation of the mutant allele with elevated HDL-C levels in the proband's family. In conclusion, we have identified a novel LCAT gene Gly230Arg mutation (LCAT[Fin]), which, together with the LPL Asn291Ser mutation, represents a relatively common genetic cause of diminishing HDL-C levels, at least among Finns. This article also reports occurrence of a CETP mutation in subjects having non-Japanese roots.
The genetic and biochemical basis of fish-eye disease (FED) was investigated in a 63-year-old female proband with low plasma HDL cholesterol. Analyses of corneal and plasma lipids of the proband were consistent with impaired lecithin:cholesterol acyltransferase (LCAT) activity. Free cholesterol and phospholipid levels were elevated relative to control values, whereas cholesteryl ester levels were greatly reduced. Fatty acid compositions of corneal lipids from the proband and control subjects differ from the respective fatty acid compositions of their plasma lipids. This suggests that the metabolic pathways and acyl chain specificities for phospholipid, cholesteryl ester, and triglyceride metabolism within the cornea are distinct from those of plasma. Sequencing of the LCAT gene from the proband revealed a novel mutation at nucleotide 399, corresponding to an Arg99-->Cys substitution. Secretion of LCAT (Arg99-->Cys) by transfected COS-6 cells was approximately 50% of that of the wild type, but its specific activity against reassembled HDL was 93% lower than that of wild-type LCAT. The specific activities of wild-type and LCAT (Arg99-->Cys) against LDL were reduced similarly, suggesting that the appearance of the FED phenotype does not require enhanced activity against LDL. Our data support the hypothesis that FED is a partial LCAT deficiency in which poor esterification in specific types of HDL particles may contribute to the appearance of the corneal opacities.
Title: Familial lecithin:cholesterol acyltransferase deficiency: molecular analysis of a compound heterozygote: LCAT (Arg147 --> Trp) and LCAT (Tyr171 --> Stop) Guerin M, Dachet C, Goulinet S, Chevet D, Dolphin PJ, Chapman MJ, Rouis M Ref: Atherosclerosis, 131:85, 1997 : PubMed
Lecithin:cholesterol acyltransferase (LCAT) is responsible for the formation of the majority of plasma cholesteryl esters. Familial LCAT deficiency is associated with corneal opacity, anemia and proteinurea and typically results in renal failure in the 4-5th decade; this syndrome is equally characterized by the quasi-absence of plasma LCAT activity with variable enzyme mass and very low levels of plasma cholesteryl esters. In this study, we report detailed analyses of plasma lipids and lipoprotein profile in two sisters (CM and ML) presenting classical homozygous LCAT-deficiency; the younger sibling (CM) had proteinurea from an early age whereas the older sister (ML) has never exhibited renal dysfunction. We investigated the molecular defect in the 45 year-old woman (proband CM) exhibiting all clinical and biochemical features of familial LCAT deficiency: a plasma cholesterol level of 105 mg/dl, of which 95% was unesterified, an HDL-cholesterol of 6.5 mg/dl and an apo A-I level of 52 mg/dl. The proband (CM) displayed a plasma cholesterol esterification rate which corresponded to 2% of normal LCAT activity; plasma LCAT protein concentration was 0.56 microg/ml and equivalent to approximately 10% of normal LCAT mass. Analysis by single strand conformation polymorphism (SSCP) of the PCR products corresponding to exons 4 and 5 of the LCAT gene revealed a visible band shift. Sequence analyses of exons 4 + 5 revealed two separate single point mutations: a C --> T transition replacing Arg147 by Trp and a T --> G transition converting Tyr171 to a stop codon. The presence of these two point mutations was confirmed by restriction enzyme analyses: the C --> T transition abolished a MwoI site whereas the T --> G transition created an AvrII site. The Arg147 mutation was associated with a non-secreted protein. The Tyr171 mutation resulted in formation of a truncated protein lacking the catalytic site. In summary, we have identified an LCAT deficient patient corresponding to a compound heterozygote for the Arg147 --> Trp mutation and a new molecular defect involving a Tyr171 --> Stop mutation in the LCAT gene.
Title: A new molecular defect in the lecithin: cholesterol acyltransferase (LCAT) gene associated with fish eye disease Contacos C, Sullivan DR, Rye KA, Funke H, Assmann G Ref: J Lipid Res, 37:35, 1996 : PubMed
We report a new genetic defect in the lecithin:cholesterol acyltransferase (LCAT) gene associated with classical clinical and biochemical features of fish eye disease. The 63-year-old Australian female proband also suffers from non-insulin-dependent (type II) diabetes mellitus. She presented with corneal opacities, markedly reduced HDL-cholesterol (0.1 mmol/L; < 10% of normal controls), and elevated plasma triglycerides. The presence of diabetes did not explain the lipoprotein profile, which differed markedly in comparison to two female hypertriglyceridemic diabetic subjects. Cholesterol esterification in HDL-like particles was minimal but plasma cholesterol esterification was maintained due to LCAT activity in non-HDL-containing lipoprotein fractions. DNA sequence analysis of the proband's LCAT gene showed two C to T transitions resulting in the substitution of Thr123 with Ile and Tyr144 with Cys. Allele-specific PCR amplification procedures were used to confirm the presence of the mutations in this proband and to screen for additional carriers in her family. Three first degree relatives (mother, brother, son) were heterozygous for the Thr123 --> Ile mutation and her daughter had the Tyr144 --> Cys mutation. Apart from a reduction in HDL-cholesterol levels to half the normal concentration and a 20% reduction in apoA-I levels, their plasma lipids were unremarkable. The proband's son and daughter were further investigated. Both had normal cholesterol esterification rates in plasma and VLDL/LDL-depleted plasma, but reduced LCAT activity (50% that of normal). Thus, the biochemical and phenotypic expression for fish eye disease in the heterozygote subjects was similar, irrespective of the underlying LCAT mutation.
The first step in the splicing of an intron from nuclear precursors of mRNA results in the formation of a lariat structure. A distinct intronic nucleotide sequence, known as the branchpoint region, plays a central role in this process. We here describe a point mutation in such a sequence. Three sisters were shown to suffer from fish-eye disease (FED), a disorder which is caused by mutations in the gene coding for lecithin:cholesterol acyltransferase (LCAT). Sequencing of the LCAT gene of all three probands revealed compound heterozygosity for a missense mutation in exon 4 which is reported to underlie the FED phenotype, and a point mutation located in intron 4 (IVS4:T-22C). By performing in vitro expression of LCAT minigenes and reverse transcriptase PCR on mRNA isolated from leukocytes of the patient, this gene defect was shown to cause a null allele as the result of complete intron retention. In conclusion, we demonstrated that a point mutation in a lariat branchpoint consensus sequence causes a null allele in a patient with FED. In addition, our finding illustrates the importance of this sequence for normal human mRNA processing. Finally, this report provides a widely applicable strategy which ensures fast and effective screening for intronic defects that underlie differential gene expression.
Title: A novel missense mutation (Asn5-->Ile) in lecithin: cholesterol acyltransferase (LCAT) gene in a Japanese patient with LCAT deficiency Okubo M, Aoyama Y, Shio H, Albers JJ, Murase T Ref: Int J Clin Lab Res, 26:250, 1996 : PubMed
We identified a novel missense mutation in the lecithin:cholesterol acyltransferase gene in a new case of lecithin:cholesterol acyltransferase (LCAT) deficiency. The patient was a 64-year-old diabetic Japanese male who showed an extremely low level of serum high-density lipoprotein-cholesterol, corneal opacities, anemia, and proteinuria. Both the patient's LCAT activity and mass were markedly low. DNA sequence analysis of the LCAT gene showed an A-to-T transition at base 97 in exon 1, and predicted a change in asparagine to isoleucine at the 5th amino acid of the protein. Restriction analysis of polymerase chain reaction-amplified DNA using Ase I showed that the patient was homozygous for this mutation. Our results suggested that asparagine 5 was an important amino acid and substitution with isoleucine caused marked reduction of LCAT activity and mass, resulting in LCAT deficiency.
Title: Complete deficiency of plasma lecithin-cholesterol acyltransferase (LCAT) activity due to a novel homozygous mutation (Gly-30-Ser) in the LCAT gene Owen JS, Wiebusch H, Cullen P, Watts GF, Lima VL, Funke H, Assmann G Ref: Hum Mutat, 8:79, 1996 : PubMed
This paper describes a novel genetic defect which causes fish-eye disease in four homozygous probands and its biochemical presentation in 34 heterozygous siblings. The male index patient presented with premature coronary artery disease, corneal opacification, HDL deficiency, and a near total loss of plasma lecithin:cholesterol acyltransferase (LCAT) activity. Sequencing of the LCAT gene revealed homozygosity for a novel missense mutation resulting in an Asp131 - Asn (N131D) substitution. Heterozygotes showed a highly significant reduction of HDL-cholesterol and apolipoprotein A-I levels as compared with controls which was associated with a specific decrease of LpA-I:A-II particles. Functional assessment of this mutation revealed loss of specific activity of recombinant LCAT(N131D) against proteoliposomes. Unlike other mutations causing fish-eye disease, recombinant LCAT(N131D) also showed a 75% reduction in specific activity against LDL. These unique biochemical characteristics reveal the heterogeneity of phenotypic expression of LCAT gene defects within a range specified by complete loss of LCAT activity and the specific loss of activity against HDL. The impact of this mutation on HDL levels and HDL subclass distribution may be related to the premature coronary artery disease observed in the male probands.
Title: Two different allelic mutations in a Finnish family with lecithin:cholesterol acyltransferase deficiency Miettinen H, Gylling H, Ulmanen I, Miettinen TA, Kontula K Ref: Arterioscler Thromb Vasc Biol, 15:460, 1995 : PubMed
Lecithin:cholesterol acyltransferase (LCAT) deficiency is a genetic disorder associated with low levels of serum HDL cholesterol. The proband of the Finnish LCAT-deficient family had corneal opacities, proteinuria, anemia with stomatocytosis, low serum HDL cholesterol (0.27 mmol/L), and low LCAT activity. Sequence analysis of his LCAT gene revealed compound heterozygosity for two different mutations: a C insertion in exon 1 between nucleotides 932 and 937 and a C-to-T point mutation in exon 6 at position 4976. The C insertion in exon 1 is predicted to result in premature termination and a truncated polypeptide containing only 16 amino acids. The C-to-T point mutation in exon 6 substitutes cysteine for arginine at residue 399. The functional significance of the Arg399-->Cys mutation was examined by expressing the mutated and wild-type LCAT cDNAs in COS cells. COS cells transfected with mutated and wild-type cDNAs showed comparable levels of mature LCAT mRNA. However, LCAT activity in the cell media of COS cells transfected with the mutant LCAT cDNA was significantly lower than that of COS cells transfected with the wild-type cDNA (1.4% versus 12.0% cholesterol esterified, respectively). A polymerase chain reaction-based duplex assay, in which both mutations can be detected simultaneously, was used for preliminary screening of Finnish subjects with serum HDL levels below 0.9 mmol/L; two additional individuals heterozygous for the Arg399-->Cys mutation were identified.
Previous mutations associated with lecithin:cholesterol acyltransferase (LCAT) deficiency have been identified using genomic DNA. To facilitate mutation analysis, we used cDNA from cultured fibroblasts which were shown to express LCAT mRNA. Using reverse-transcriptase PCR, LCAT cDNA was obtained from a 13-year-old boy with complete LCAT deficiency, characterized by low HDL-C (3 mg/dl), nondetectable initial cholesterol esterification rate, LCAT activity, and minimal LCAT mass (0.16 vs. 5-7.5 micrograms/ml). Sequencing of LCAT cDNA clones identified two mutations. A novel frameshift mutations caused by deletion of cytosine at the third nucleotide position of amino acid 168 (exon 5) predicts a disrupted protein catalytic site by converting Ser181-->Ala and creates a Pvu-II restriction site prior to premature truncation at amino acid 238. A C-->T transition results in a substitution of methionine for threonine at amino acid position 321 and creates an Nla-III restriction site on the maternal allele. Expression studies of mutant LCAT cDNA confirmed the virtual absence of LCAT activity in transfected COS-1 cells. The molecular defect in a young male with complete LCAT deficiency has been identified using fibroblast cDNA.
We investigated the genetic defects in two patients with familial lecithin:cholesterol acyltransferase (LCAT) deficiency. Their clinical manifestations including corneal opacities, anemia, proteinuria, and hypoalphalipoproteinemia were identical for familial LCAT deficiency. Their LCAT activities and the cholesterol esterification rate (CER) were nearly zero, and their LCAT masses were below 10% of normal control values. Sequence analysis of the amplified DNA of case 1 revealed one base deletion of G at base 873 (first position of Val264) in exon 6, leading to a premature termination by frameshift. Sequence analysis of amplified DNA of case 2 revealed a single G to A converting Gly (GGT) to Ser (AGT) substitution at residue 344. When COS-1 cells were transfected with these mutants, LCAT activity in the medium was nearly zero, and the LCAT mass was undetectable (< 0.01 microgram/ml). In contrast, LCAT activity in the medium of COS-1 cells, transfected with wild-type LCAT, was 1.7 nmol/h per ml and the LCAT mass was 0.09 micrograms/ml. The LCAT mass in the cell lysates of the mutants was less than 12% of control for case 1 and 18% of control for case 2. Northern blot analysis of the mRNA of COS-1 cells transfected with the mutants showed the same amounts of LCAT mRNA as compared with wild-type LCAT. Biosynthesis of mutant LCATs was analyzed by pulse-chase and immunocytochemistry in transfected baby hamster kidney cells. SDS-PAGE/fluorography demonstrated that wild-type LCAT was synthesized as a high-mannose type of 56 kDa, which was very slowly converted to a mature form of 67 kDa and was secreted into the media. In contrast to the wild-type LCAT, the mutant precursors were not processed into the mature form but slowly degraded along with chase times. On steady and continuous labeling in the case of wild-type LCAT, the mature 67 kDa form was observed in both the cell lysate and media, whereas no mature form was detected in the cell lysates and media which were transfected mutant LCATs. These data suggest that the mutant LCATs are actually synthesized in an amount comparable to that of wild-type, but they are slowly degraded without being processed into the mature form. The immunocytochemistry revealed that mutant LCATs were mainly retained in the endoplasmic reticulum. These data suggest that these two mutations may disrupt the mutant LCATs' transport from the endoplasmic reticulum into Golgi apparatus, resulting in LCAT deficiency.
Title: A single G to A nucleotide transition in exon IV of the lecithin: cholesterol acyltransferase (LCAT) gene results in an Arg140 to His substitution and causes LCAT-deficiency Steyrer E, Haubenwallner S, Horl G, Giessauf W, Kostner GM, Zechner R Ref: Hum Genet, 96:105, 1995 : PubMed
We have characterized the molecular defect causing lecithin:cholesterol acyltransferase (LCAT)-deficiency (LCAT-D) in the LCAT gene in three siblings of Austrian descent. The patients presented with typical symptoms including corneal opacity, hemolytic anemia, and kidney dysfunction. LCAT activities in the plasma of these three patients were undetectable. DNA sequence analysis of polymerase chain reaction (PCR)-amplified DNA of all six LCAT exons revealed a new point mutation in exon IV of the LCAT gene, i.e., a G to A substitution in codon 140 converting Arg to His. This mutation caused the loss of a cutting site for the restriction endonuclease HhaI within exon IV: Upon digestion of a 629-bp exon IV PCR product with HhaI, the patients were found to be homozygous for the mutation. Eight of 11 family members were identified as heterozygotes. Transfection studies of COS-7 cells with plasmids containing a wild-type or a mutant LCAT cDNA revealed that, in contrast to the cell medium containing wild-type enzyme, no enzyme activity was detectable upon expression of the mutant protein. This represents strong evidence for the causative nature of the observed mutation for LCAT deficiency in affected individuals and supports the conclusion that Arg140 is crucial for the structure of an enzymatically active LCAT protein.
Title: Deficiency of lecithin:cholesterol acyltransferase due to compound heterozygosity of two novel mutations (Gly33Arg and 30 bp ins) in the LCAT gene Wiebusch H, Cullen P, Owen JS, Collins D, Sharp PS, Funke H, Assmann G Ref: Hum Mol Genet, 4:143, 1995 : PubMed
Familial plasma lecithine: cholesterol acyltransferase (LCAT) deficiency is a disease that is inherited as an autosomal recessing trait. The main clinical abnormalities are corneal opacities, anemia and frequently, though not invariably, proteinuria. These abnormalities result from a failure of LCAT to esterify cholesterol in plasma. Renal failure can be a life-threatening complication. In plasma, all lipoprotein classes show abnormalities including lipid composition, shape, distribution and concentration. Fish eye disease, which is characterized by corneal opacities and plasma lipoprotein abnormalities, is also a result from deficiency of LCAT activity. As LCAT gene has been cloned, molecular defects of both familial LCAT deficiency and fish eye disease have been reported recently.
Classic (complete) lecithin:cholesterol acyltransferase (LCAT) deficiency and Fish-eye disease (partial LCAT deficiency) are genetic syndromes associated with markedly decreased plasma levels of high density lipoprotein (HDL) cholesterol but not with an increased risk of atherosclerotic cardiovascular disease. We investigated the metabolism of the HDL apolipoproteins (apo) apoA-I and apoA-II in a total of five patients with LCAT deficiency, one with classic LCAT deficiency and four with Fish-eye disease. Plasma levels of apoA-II were decreased to a proportionately greater extent (23% of normal) than apoA-I (30% of normal). In addition, plasma concentrations of HDL particles containing both apoA-I and apoA-II (LpA-I:A-II) were much lower (18% of normal) than those of particles containing only apoA-I (LpA-I) (51% of normal). The metabolic basis for the low levels of apoA-II and LpA-I:A-II was investigated in all five patients using both exogenous radiotracer and endogenous stable isotope labeling techniques. The mean plasma residence time of apoA-I was decreased at 2.08 +/- 0.27 d (controls 4.74 +/- 0.65 days); however, the residence time of apoA-II was even shorter at 1.66 +/- 0.24 d (controls 5.25 +/- 0.61 d). In addition, the catabolism of apoA-I in LpA-I:A-II was substantially faster than that of apoA-I in LpA-I. In summary, genetic syndromes of either complete or partial LCAT deficiency result in low levels of HDL through preferential hypercatabolism of apoA-II and HDL particles containing apoA-II. Because LpA-I has been proposed to be more protective than LpA-I:A-II against atherosclerosis, this selective effect on the metabolism of LpA-I:A-II may provide a potential explanation why patients with classic LCAT deficiency and Fish-eye disease are not at increased risk for premature atherosclerosis despite markedly decreased levels of HDL cholesterol and apoA-I.
The presence of lecithin:cholesterol acyltransferase (LCAT) deficiency in six probands from five families originating from four different countries was confirmed by the absence or near absence of LCAT activity. Also, other invariate symptoms of LCAT deficiency, a significant increase of unesterified cholesterol in plasma lipoproteins and the reduction of plasma HDL-cholesterol to levels below one-tenth of normal, were present in all probands. In the probands from two families, no mass was detectable, while in others reduced amounts of LCAT mass indicated the presence of a functionally inactive protein. Sequence analysis identified homozygous missense or nonsense mutations in four probands. Two probands from one family both were found to be compound heterozygotes for a missense mutation and for a single base insertion causing a reading frame-shift. Subsequent family analyses were carried out using mutagenic primers for carrier identification. LCAT activity and LCAT mass in 23 genotypic heterozygotes were approximately half normal and clearly distinct from those of 20 unaffected family members. In the homozygous patients no obvious relationship between residual LCAT activity and the clinical phenotype was seen. The observation that the molecular defects in LCAT deficiency are dispersed in different regions of the enzyme suggests the existence of several functionally important structural domains in this enzyme.
We have identified the molecular defect in two siblings presenting with classical clinical and biochemical features of Fish Eye disease (FED), including corneal opacities, HDL cholesterol < 10 mg/dl, normal plasma cholesteryl esters, and elevated triglycerides. In contrast to previously reported patients with FED who are unable to esterify HDL-associated cholesterol, our patients' plasma lecithin-cholesterol acetyltransferase (alpha-LCAT)-specific activities assayed using an HDL-like proteoliposome substrate were 12.7-25.7 nmol/micrograms (19.5 +/- 1.8 in controls). In addition, significant residual cholesterol esterification was present in VLDL/LDL-depleted plasma, confirming the presence of HDL-associated alpha-LCAT activity. DNA sequence analysis of the proband's LCAT gene identified deletion of the triplet coding for leu300, which resulted in the loss of a restriction site for MlnI. Digestion of PCR-amplified DNA using MlnI established that both siblings are homozygous for this defect. Expression of LCAT300-del. in human embryonic kidney-293 cells revealed normal mRNA and intracellular LCAT concentrations. However, reduced amounts of LCAT300-del., which had a normal specific alpha-LCAT activity, were present in the media. In summary, we report the first case of FED associated with a mutant enzyme that has a normal alpha-LCAT-specific activity. The functional significance of this LCAT gene defect has been established in an in vitro expression system, which demonstrates that very small amounts of this functional LCAT mutant enzyme accumulate in the media. Characterization of LCAT300-del. established that selective alpha-LCAT deficiency is not a prerequisite for the development of FED. On the basis of our combined results, we propose that the residual amounts of total plasma LCAT activity and not its distribution on lipoproteins primarily determines the heterogeneity in phenotypic expression observed in familial LCAT deficiency syndromes.
The molecular defects in the lecithin:cholesterol acyltransferase (LCAT) gene have been identified in a 52-year-old patient with classic LCAT deficiency, presenting with corneal clouding and proteinuria. Plasma total cholesterol was normal, triglycerides were elevated, whereas high density lipoprotein (HDL) cholesterol (8 mg/dl) and plasma cholesteryl esters (6% of total cholesterol) were markedly reduced. Plasma cholesterol esterification rate (pCER) was zero, alpha-LCAT activity, assayed using an HDL-like proteoliposome substrate was reduced to 1.6% of control, and LCAT mass was 3.7% of normal plasma levels. DNA sequence analysis of the proband's LCAT gene identified a C to A substitution, converting tyr83 to a stop codon, and a T to A transition, replacing tyr156 by asn. Restriction analysis of PCR-amplified DNA from the proband, a control and his four children using the enzymes Acc I and Rsa I established that the patient is a compound heterozygote for both mutations. The two children, heterozygous for the stop codon defect, were phenotypically indistinguishable from the two with the tyr156 defect. In vitro expression of LCAT (tyr156-->asn) in human embryonic kidney-293 cells established the functional significance of this mutation. The secreted translation product had only 6% of control mass and no detectable CER; however, the residual LCAT mass of the in vitro expressed LCAT (tyr156-->asn) demonstrated a specific alpha-LCAT activity of 30% of control, suggesting that this amino acid substitution results in a mutant enzyme that retains some enzymic activity, but may be rapidly catabolized. In summary, we have identified two unique defects in the LCAT gene that lead to the expression of classic LCAT deficiency in this kindred.
Fish eye disease (FED) is an extremely rare familial disorder characterized by severe HDL deficiency and extensive corneal opacities. This disorder appears to be a variant of familial lecithin: cholesterol acyltransferase (LCAT) deficiency in which the enzyme remains partly active yet the ability of the enzyme to esterify cholesterol in high-density lipoprotein (HDL) has been lost. The rarity of this disorder has limited advances in our understanding of the pathophysiology of the HDL deficiency. However, we here describe the clinical and biochemical presentation of a family with FED who are of Dutch descent. The proposition presented with HDL deficiency and corneal opacity. Subsequently, they were diagnosed as having FED by the absence of LCAT activity against a small proteoliposome substrate despite the presence of half-normal LCAT mass and a near-normal ratio of unesterified to total cholesterol in plasma. Heterozygotes presented with half-normal LCAT activity, but not with decreased HDL. With the identification of this three-generation family, renewed investigation of this intriguing disorder of HDL is now possible.
Title: Two different allelic mutations in the lecithin-cholesterol acyltransferase gene associated with the fish eye syndrome. Lecithin-cholesterol acyltransferase (Thr123----Ile) and lecithin-cholesterol acyltransferase (Thr347----Met) Klein HG, Lohse P, Pritchard PH, Bojanovski D, Schmidt H, Brewer HB, Jr. Ref: J Clinical Investigation, 89:499, 1992 : PubMed
We have elucidated the genetic defect in a 66-yr-old patient with fish eye syndrome (FES) presenting with severe corneal opacities and hypoalphalipoproteinemia. The patient's plasma concentration of high density lipoprotein (HDL) cholesterol was reduced at 7.7 mg/dl (35.1-65.3 mg/dl in controls) and the HDL cholesteryl ester content was 31% (60-80% in controls); however, total plasma cholesteryl esters were similar to normal (60% of total cholesterol vs. a mean of 66% in controls). The patient's plasma cholesterol esterification rate was slightly reduced at 51 nmol/ml per h (control subjects: 61-106 nmol/ml per h), whereas lecithin-cholesterol acyltransferase (LCAT) activity, assayed using a HDL-like exogenous proteoliposome substrate, was virtually absent (0.9 nmol/ml per h vs. 25.1-27.9 nmol/ml per h in control subjects). DNA sequence analysis of the proband's LCAT gene revealed two separate C to T transitions resulting in the substitution of Thr123 with Ile and Thr347 with Met. The mutation at codon 347 created a new restriction site for the enzyme Nla III. Analysis of the patient's polymerase chain reaction-amplified DNA containing the region of the Thr347 mutation by digestion with Nla III confirmed that the proband is a compound heterozygote for both defects. The patient's daughter, who is asymptomatic despite a 50% reduction of LCAT activity, is heterozygous for the Thr123----Ile mutation. Our data indicate that the regions adjacent to Thr123 and Thr347 of LCAT may play an important role in HDL cholesterol esterification, suggesting that these regions may contain a portion of the LCAT binding domain(s) for HDL.
Title: The genetic defect of the original Norwegian lecithin:cholesterol acyltransferase deficiency families. Skretting G, Blomhoff JP, Solheim J, Prydz H Ref: FEBS Letters, 309:307, 1992 : PubMed
Three of the original Norwegian lecithin:cholesterol acyltransferase (LCAT) deficiency families have been investigated for mutations in the gene for lecithin:cholesterol acyltransferase by DNA sequencing of the exons amplified by the polymerase chain reaction. A single T----A transversion in codon 252 in exon 6 converting Met(ATG) to Lys(AAG) was observed in all homozygotes. In spite of the identical mutation, the disease phenotypes differed in severity. This was not reflected in the expression of LCAT in the heterozygotes.
Title: An amino acid exchange in exon I of the human lecithin: cholesterol acyltransferase (LCAT) gene is associated with fish eye disease Skretting G, Prydz H Ref: Biochemical & Biophysical Research Communications, 182:583, 1992 : PubMed
The exons of the lecithin:cholesterol acyltransferase (LCAT) gene in DNA samples from two of the original Swedish Fish Eye Disease patients have been amplified by polymerase chain reactions and sequenced by the dideoxy method. The two patients apparently were unrelated. In both patients a mutation in codon 10 of the first exon was found, altering proline10 to leucine. We note that the mutations causing Fish Eye Disease as well as those causing classical LCAT deficiency are spread over most of the translated gene. Why these various mutations in the same gene give rise to two different disease phenotypes remains unexplained.
Title: Molecular defect in familial lecithin:cholesterol acyltransferase (LCAT) deficiency: a single nucleotide insertion in LCAT gene causes a complete deficient type of the disease Bujo H, Kusunoki J, Ogasawara M, Yamamoto T, Ohta Y, Shimada T, Saito Y, Yoshida S Ref: Biochemical & Biophysical Research Communications, 181:933, 1991 : PubMed
Familial lecithin:cholesterol acyltransferase (LCAT) deficiency is a hereditary disorder with clinical manifestations including corneal opacity, premature atherosclerosis and renal failure. In this study, we analyzed the molecular base underlying a case of Japanese LCAT deficiency, in which both LCAT mass and activity of the proband were nearly absent. DNA blot hybridization analysis showed no gross rearrangement in the LCAT gene of the proband. The nucleotide sequence analysis of the cloned LCAT gene demonstrated only an extra nucleotide "C" insertion at the first exon, when compared to the sequence of wild type. This single base insertion caused a shift of the following reading frame, probably resulting in a truncated abnormal LCAT polypeptide that consist of only 16 amino acids. The direct sequence analysis of PCR-amplified DNA showed only the same insertion, indicating that the LCAT-deficient proband is a homozygote for the mutant allele. These results indicate that the clinical and biochemical feature of the patient is mainly caused by a complete deficiency of the enzyme based on a homozygous abnormality of LCAT gene.
Title: A 'Fish-eye disease' familial condition with massive corneal opacities and hypoalphalipoproteinaemia: clinical, biochemical and genetic features Clerc M, Dumon MF, Sess D, Freneix-Clerc M, Mackness M, Conri C Ref: European Journal of Clinical Investigation, 21:616, 1991 : PubMed
A Caucasian family of mediterranean origin comprising a patient whose parents were first cousins, his wife and their three children, and his two sisters have been studied. The patient and his two daughters were afflicted with the same corneal opacities and hypoalphalipoproteinaemia. The disease was shown to be transmitted as a non-sex-linked recessive trait. The corneal opacities develop at the end of the second decade of life and consist of numerous minute greyish dots in the entire corneal stroma that give the cornea a misty appearance. Vision slowly deteriorated from 40 years of age. At about 50 years of age, except in one of the two daughters who showed Marfanoid syndrome, the three patients had good general health and no symptoms of atherosclerosis. Biochemical investigations showed hypoalphalipoproteinaemia (with a faint fast-moving HDL band on polyacrylamide gel gradient electrophoresis and small arcs of HDL2 and HDL3 of low mobility determined by agarose gel immunoelectrophoresis), low total cholesterol (3.5-4.9 mmol l-1), slightly decreased cholesteryl ester/total cholesterol ratio (0.52-0.63), extremely low HDL cholesterol (0.20-0.21 mmol l-1), mild hypertriglyceridaemia (1.94-3.80 mmol l-1), and striking deficiency in apo A-I and apo A-II (0.45-0.72, 0.08-0.16 g l-1, respectively). The esterification of HDL cholesterol was low while that of LDL and VLDL was nearly normal. Other laboratory values were normal. The HDL subspecies and major apolipoprotein isoforms have been studied to differentiate FED from Tangier disease, LCAT deficiency, as Apo A-I, A-II, C-II, C-III deficiencies and variants.(ABSTRACT TRUNCATED AT 250 WORDS)
Epidemiological as well as biochemical evidence of recent years has established that a low plasma level of high density lipoprotein-cholesterol is a predictor for the risk of coronary artery disease. However, there is a heterogeneous group of rare familial disorders, characterized by severe high density lipoprotein deficiency, in which the predicted increased risk is not clearly apparent. One such disorder has been called fish eye disease to reflect the massive corneal opacification seen in these patients. In this report, we describe the biochemical and genetic presentation of two German fish eye disease homozygotes and their family members. Vertical transmission of a decrease in the specific activity of lecithin-cholesterol acyltransferase (EC 2.3.1.43) indicated that this enzyme was a candidate gene for harboring the defect responsible for this disorder. Direct sequencing of DNA segments amplified by the polymerase chain reaction (PCR) that encode the exons of the lecithin-cholesterol acyltransferase gene led to the identification of a homozygous mutation resulting in the substitution of threonine at codon 123 for an isoleucine residue in both individuals. Family analysis in an extended pedigree was used to establish a causal relationship between this mutation and the biochemical phenotype for fish eye disease. The homozygous presence of this mutation in two phenotypically homozygous members of an unrelated Dutch family with fish eye disease further supports this finding.
Familial deficiency of lecithin:cholesterol acyltransferase (LCAT) is an autosomal recessive disorder characterised by abnormalities of all plasma lipoprotein classes and by abnormal deposition of unesterified cholesterol in tissues. To elucidate the molecular basis of the disease, the LCAT genes of three unrelated Japanese patients were amplified by means of the polymerase chain reaction. Direct sequencing of the amplified fragments covering all exons and junctions showed that the patients are homozygotes for separate gene mutations. In one patient a 3 bp insertion, which should cause a substantial change in the enzyme structure, was found in exon 4; he had near absence of LCAT mass and activity. Two separate missense mutations were identified in exon 6 of the other two patients, who produced functionally defective enzymes that differed widely in specific activity. The replacement of asparagine228 with positively charged lysine completely abolished enzyme activity, whereas the other, conservative, aminoacid substitution (methionine293----isoleucine) gave rise to a partially defective enzyme. These results show that distinct mutations cause differences in plasma LCAT activity and LCAT mass, ultimately leading to differential phenotypic expression of familial LCAT deficiency.
Title: Lecithin-cholesterol acyltransferase (LCAT) deficiency with a missense mutation in exon 6 of the LCAT gene Maeda E, Naka Y, Matozaki T, Sakuma M, Akanuma Y, Yoshino G, Kasuga M Ref: Biochemical & Biophysical Research Communications, 178:460, 1991 : PubMed
The plasma enzyme, human lecithin-cholesterol acyltransferase (LCAT) is responsible for the majority of cholesterol ester formation in human plasma and is a key enzyme of the reverse transport of cholesterol from peripheral tissue to the liver. We sequenced genomic DNA of the LCAT gene from a Japanese male patient who was clinically and biochemically diagnosed as a familial LCAT deficiency. Analysis of all exons and exon-intron boundaries revealed only a single G to A transition within the sixth exon of both allele of the gene, leading to the substitution of methionine for isoleucinle at residue 293 of the mature enzyme. This mutation creates a new hexanucleotide recognition site for the restriction endonuclease Ndel. Familial study of Ndel digestion of the genomic DNA and determination of plasma LCAT activity established that the patient and his sister whose plasma LCAT activity were extremely reduced were homozygous and his children whose plasma LCAT activity were about half of normal controls were heterozygous for this mutation.
The enzyme, lecithin cholesterol acyltransferase (LCAT), is responsible for the esterification of plasma cholesterol mediating the transfer of an acyl group from lecithin to the 3-hydroxy group of cholesterol. Deficiency of the enzyme is a well-known syndrome with a widespread geographic occurrence. We have cloned an allele from a patient homozygous for the LCAT deficiency. The only change that we could detect is a C to T transition in the fourth exon of the gene; this causes a substitution of Arg for Trp at position 147 of the mature protein. The functional significance of such a substitution with respect to the enzyme defect was demonstrated by transfecting the mutated LCAT gene in the cell line COS-1.
Title: A new case of familial lecithin: cholesterol acyltransferase (LCAT) deficiency--paradoxical findings regarding LCAT mass and activity in 23 members of a family Takata K, Kajiyama G, Horiuchi I, Watanabe T, Tokumo H, Hirata Y Ref: Jpn J Med, 28:765, 1989 : PubMed
LCAT activity and mass were assayed simultaneously in 23 members of a new family case, revealing two homozygotes with a markedly low HDL--cholesterol level and ester cholesterol ratio. The LCAT mass in these patients was only 0.8 and 0.9 micrograms/ml, respectively (normal range 4.4-8.1) and their LCAT activity was 4 and 6 nM/ml/h 37 degrees C (normal range 60-120). Apolipoprotein (Apo) A-I and II levels were significantly low; however, apolipoprotein E tended to be high. In two-dimensional electrophoresis, apo A-I isoform visualized the increase of immature apo A-I; that is, A-I2. One subject showed the clinical characteristics of classic LCAT deficiency; however, the other, who was a vegetarian, showed corneal opacities and red cell deformity, but not proteinuria. This suggests that a low fat diet which decreases the level of atherogenic large LDL, may lead to a more favourable prognosis with a reduced risk for renal insufficiency. There were two different types of LCAT abnormality in this family series. Among the 10 examined paternal kindred of the proband who was one of two homozygotes, seven had a low LCAT mass but normal LCAT activity with the exception of one kindred who had a low mass and low activity. In contrast, among his seven maternal kindred examined, two had a low LCAT activity but normal mass.
Title: Different substrate specificities of plasma lecithin: cholesterol acyl transferase in fish eye disease and Tangier disease Carlson LA, Holmquist L, Assmann G Ref: Acta Med Scand, 222:345, 1987 : PubMed
Esterification of plasma free cholesterol is mediated by lecithin:cholesterol acyl transferase (LCAT). The free cholesterol of plasma high density lipoproteins (HDL) is considered to be the preferred substrate for LCAT. It therefore appeared as a paradox that plasma cholesterol esterification, both in vivo and in vitro, is normal in fish eye disease and Tangier disease, two familial conditions with extremely low plasma HDL levels. Fish eye disease plasma, however, was shown to have LCAT activity primarily acting on combined very low (VLDL) and low (LDL) density lipoproteins, denominated beta-LCAT, while it lacked LCAT activity esterifying HDL cholesterol (alpha-LCAT). Here we show that Tangier plasma, in contrast, has both alpha- and beta-LCAT. Thus, in both fish eye and Tangier diseases it is beta-LCAT that explains the apparent normal plasma cholesterol esterification. We also show that Tangier plasma, having alpha-LCAT activity, normalizes the low cholesteryl ester content as well as the abnormally small size of fish eye disease HDL particles during incubation.
A 16-year-old boy presented with bilateral arcus cornealis and markedly decreased plasma high density lipoprotein cholesterol. The plasma lipoprotein abnormalities, as well as decreased mass and activity of lecithin:cholesterol acyltransferase (LCAT), were similar to those described in patients with fish eye disease. Increased number of target cells and decreased osmotic fragility of the proband's erythrocytes were noted. The proband's father and one of his brothers showed intermediate plasma lipoprotein and LCAT alterations. The father's erythrocytes also showed abnormal osmotic fragility. The mother of the propositus had normal plasma lipoproteins and erythrocyte osmotic fragility, but her LCAT activity was also low. Many of these features suggest a disorder similar to fish eye disease which is clinically and biochemically distinct from other hypoalphalipoproteinemias.
Title: Alpha-lecithin:cholesterol acyltransferase deficiency. Lack of both phospholipase A2 and acyltransferase activities characteristic of high density lipoprotein lecithin:cholesterol acyltransferase in fish eye disease Holmquist L, Carlson LA Ref: Acta Med Scand, 222:23, 1987 : PubMed
The phospholipase A2 and acyltransferase activities characteristic of human plasma lecithin: cholesterol acyltransferase have been evaluated in incubation mixtures of lipoprotein depleted plasma of fish eye disease patients and autologous HDL or homologous normal HDL3. Both enzyme activities were strongly reduced as compared to those of normal controls. These findings further support the claim that fish eye disease plasma has a specific lack of high density lipoprotein lecithin:cholesterol acyltransferase (alpha-LCAT deficiency), although the cholesterol esterification of combined VLDL and LDL in such plasma proceeds at a normal rate.
Title: Inhibitory effect of normal high density lipoproteins on lecithin:cholesterol acyltransferase activity in fish eye disease plasma Holmquist L, Carlson LA Ref: Acta Med Scand, 222:15, 1987 : PubMed
The lecithin:cholesterol acyltransferase (LCAT) activity of lipoprotein depleted normal and fish eye disease (FED) plasma was assayed in a modified Glomset-Wright incubation system where the enzyme was allowed to act on three different normal lipoprotein substrates consisting of an authentic mixture of very low (VLDL), low (LDL) and high (HDL) density lipoproteins to assay total LCAT activity, HDL to assay alpha-LCAT activity and combined VLDL and LDL to assay beta-LCAT activity, respectively. However, using normal plasma depleted of HDL, leaving its combined VLDL and LDL as enzyme substrate, resulted in a more than twofold increase in the LCAT activity of FED plasma from the two patients compared to the activity obtained with HDL present in the incubation mixture, indicating an inhibitory effect of HDL on the beta-LCAT activity present in FED plasma. This inhibitory effect of normal HDL could also be demonstrated by autoincubation of FED plasma mixed with isolated HDL2 or HDL3. Both these HDL subfractions had a pronounced inhibitory effect on the cholesteryl ester formation in FED plasma. The present study thus clearly demonstrates that normal HDL inhibits the beta-LCAT activity present in FED plasma, esterifying the free cholesterol of combined VLDL and LDL, derived from controls as well as from the two FED patients.
Title: Evidence for the presence in human plasma of lecithin: cholesterol acyltransferase activity (beta-LCAT) specifically esterifying free cholesterol of combined pre-beta- and beta-lipoproteins. Studies of fish eye disease patients and control subjects Carlson LA, Holmquist L Ref: Acta Med Scand, 218:197, 1985 : PubMed
The present study was undertaken to test our hypothesis that two different lecithin: cholesterol acyltransferase (LCAT) activities exist in normal human plasma, one denoted alpha-LCAT esterifying the free cholesterol of high density lipoproteins (HDL) and the other denoted beta-LCAT acting on the free cholesterol of very low (VLDL) and low (LDL) density lipoproteins. Plasmas depleted of HDL were obtained by means of preparative ultracentrifugation. Incubation at 37 degrees C of these plasma fractions from control subjects and patients with fish eye disease resulted in esterification of the remaining free cholesterol of combined VLDL and LDL (pre-beta- and beta-lipoproteins) in the HDL depleted plasmas. The shapes of the cholesterol esterification rate curves were similar for whole and HDL depleted plasmas from both control subjects and fish eye disease patients. In crosswise mixed incubation experiments with isolated combined VLD and LDL and total lipoprotein depleted plasma from a control subject and a patient with fish eye disease, respectively, esterification of free cholesterol occurred. Incubation of isolated total lipoproteins in plasma from a patient with LCAT deficiency mixed with total lipoprotein depleted plasma from a fish eye disease patient as a source of LCAT caused cholesterol esterification but did not result in normalization of the LCAT deficiency HDL particles, while the amount of normal-sized LDL particles increased. The present results support the hypothesis that a beta-LCAT exists in normal human plasma.
Title: Evidence for deficiency of high density lipoprotein lecithin: cholesterol acyltransferase activity (alpha-LCAT) in fish eye disease Carlson LA, Holmquist L Ref: Acta Med Scand, 218:189, 1985 : PubMed
In a rare familial condition, fish eye disease, there is a low relative content of cholesteryl esters in the plasma high density lipoproteins (HDL) but a normal content of these lipids in the very low (VLDL) and low (LDL) density lipoproteins. Lecithin: cholesterol acyltransferase (LCAT) is the enzyme which mediates the esterification of free cholesterol in the plasma lipoproteins. In the present investigation, isolated HDL from our two fish eye disease patients were found to be excellent substrates during in vitro incubations with normal LCAT as present in lipoprotein depleted plasma from control subjects. Almost all free cholesterol of these HDL fractions became esterified and concomitantly the abnormally small fish eye disease HDL particles increased to a size in the range of that of normal HDL particles. Lipoprotein depleted plasma from fish eye disease, however, lacked the property of normal plasma to esterify the free cholesterol of HDL isolated from plasma of fish eye disease patients or control subjects. These results have led to the formulation of a new concept implying that two different LCAT activities exist in normal plasma. One of these activities, denoted alpha-LCAT, is specific for HDL (alpha-lipoproteins) and the other, beta-LCAT, is specific for VLDL-LDL (pre beta- and beta-lipoproteins). Fish eye disease according to this notion is classified as an alpha-LCAT deficiency in contrast to the classical LCAT deficiency which probably lacks both alpha- and beta-LCAT activities.
Twenty-eight patients with familial lecithin:cholesterol acyltransferase deficiency have been reported to date. We report a new Italian case who presents the clinical and biochemical characteristics of the disease. Typical disc-shaped high density lipoproteins (d = 1.063-1.21 g/ml) were detected by electron microscopy. An abnormal distribution of apolipoproteins in the different lipoprotein fractions was found by sodium dodecyl sulphate polyacrylamide electrophoresis.
Familial lecithin cholesterol acyltransferase (LCAT) deficiency is a rare inherited enzyme deficiency characterized by widespread disturbance of lipid metabolism and infiltration of many organs, including kidneys by lipids; usually it results in death from renal failure in the fourth or fifth decades. We have described a new family with LCAT deficiency and have studied three sisters with characteristic corneal opacities and no detectable plasma LCAT activity, together with eight obligate heterozygotes who have reduced LCAT activity but are phenotypically normal. All three sisters had the typical lipid abnormalities including large molecular weight particles in the low density lipoprotein (LDL) fraction of plasma previously described only in LCAT deficient patients with renal disease. However, only the youngest sister had proteinuria and renal failure. Renal biopsies from two of the sisters were infiltrated with lipid but the biopsy from the youngest contained electron dense deposits indistinguishable from those seen in immune complex disease. These findings cast doubt on the concept that large molecular weight LDL particles are the sole determinants of renal failure in LCAT deficiency.
Title: Detection of heterozygotes for familial lecithin: cholesterol acyltransferase (LCAT) deficiency Frohlich J, Hon K, McLeod R Ref: American Journal of Human Genetics, 34:65, 1982 : PubMed
"Rocket" immunoelectrophoresis using specific anti-lecithin: cholesterol acyltransferase (LCAT) antiserum showed no immunoreactive protein in two patients with familial LCAT deficiency. Subnormal quantity of plasma LCAT was found in the maternal grandmother, the parents, and in two of four siblings of the patients (3.3-3.4 mg/l vs. 5.4 +/- 0.5 mg/l in 12 controls). The immunochemical quantitation of the enzyme correlated well (r = .93) with LCAT activity in an artificial substrate assay. These two methods allow detection of heterozygotes for LCAT deficiency.
Title: Fish-eye disease. A new familial condition with massive corneal opacities and dyslipoproteinaemia Carlson LA, Philipson B Ref: Lancet, 2:922, 1979 : PubMed
A man and his three daughters had massive corneal opacities called in their home village "fish-eye disease" because of the resemblance of the eyes to those of boiled fish. The two living daughters had the same dyslipoproteinaemia, characterised by normal serum cholesterol but raised serum triglycerides, raised very-low-density lipoproteins, strikingly high levels of low-density lipoprotein (LDL) triglycerides. LDL contained normal sized as well as abnormally large particles and a 90% reduction in the level of high-density lipoprotein (HDL) cholesterol. Lecithin:cholesterol acyltransferase (LCAT) activity and the percentage of plasma cholesterol esters were normal, with excluded LCAT-deficiency. Normal electrophoretic mobility of HDL as well as other lipoprotein findings excluded Tangier disease. The clinical and laboratory abnormalities in fish-eye disease are atherosclerosis at old age, visual impairment, and dense corneal opacification. Fish-eye disease thus differs both clinically and in its lipoprotein abnormalities from LCAT-deficiency and Tangier disease.
Title: Familial serum-cholesterol esterification failure. A new inborn error of metabolism Norum KR, Gjone E Ref: Biochimica & Biophysica Acta, 144:698, 1967 : PubMed
