Prevalence of cholesteryl ester storage disease among hypercholesterolemic subjects and functional characterization of mutations in the lysosomal acid lipase gene

• Published in: Molecular genetics and metabolism Vol. 123; no. 2; pp. 169 - 176
• Main Authors: Vinje, Terje, Wierød, Lene, Leren, Trond P., Strøm, Thea Bismo
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.2018
• Subjects: Adult; Cholesterol Ester Storage Disease - enzymology; Cholesterol Ester Storage Disease - epidemiology; Cholesterol Ester Storage Disease - genetics; Enzymatic analysis; Female; HeLa Cells; Homozygote; Humans; Hypercholesterolemia; Hypercholesterolemia - physiopathology; Lysosomal acid lipase; Male; Middle Aged; Mutation; Norway - epidemiology; Phenotype; Prevalence; Sterol Esterase - genetics; Transfection; Western blot; Norway; Western blot; Hypercholesterolemia; Lysosomal acid lipase; Transfection; Mutation; Enzymatic analysis
• DOI: 10.1016/j.ymgme.2017.11.008
• ISSN: 1096-7192; 1096-7206

Lysosomal acid lipase hydrolyzes cholesteryl esters and triglycerides contained in low density lipoprotein. Patients who are homozygous or compound heterozygous for mutations in the lysosomal acid lipase gene (LIPA), and have some residual enzymatic activity, have cholesteryl ester storage disease. One of the clinical features of this disease is hypercholesterolemia. Thus, patients with hypercholesterolemia who do not carry a mutation as a cause of autosomal dominant hypercholesterolemia, may actually have cholesteryl ester storage disease. In this study we have performed DNA sequencing of LIPA in 3027 hypercholesterolemic patients who did not carry a mutation as a cause of autosomal dominant hypercholesterolemia. Functional analyses of possibly pathogenic mutations and of all mutations in LIPA listed in The Human Genome Mutation Database were performed to determine the pathogenicity of these mutations. For these studies, HeLa T-REx cells were transiently transfected with mutant LIPA plasmids and Western blot analysis of cell lysates was performed to determine if the mutants were synthesized in a normal fashion. The enzymatic activity of the mutants was determined in lysates of the transfected cells using 4-methylumbelliferone-palmitate as the substrate. A total of 41 mutations in LIPA were studied, of which 32 mutations were considered pathogenic by having an enzymatic activity <10% of normal. However, none of the 3027 hypercholesterolemic patients were homozygous or compound heterozygous for a pathogenic mutation. Thus, cholesteryl ester storage disease must be a very rare cause of hypercholesterolemia in Norway. •3027 hypercholesterolemic patients have been screened for mutations in the lysosomal acid lipase gene (LIPA).•Mutations considered possibly pathogenic were subjected to functional analysis in order to assess their pathogenicity.•None of the 3027 patients were homozygous or compound heterozygous for pathogenic mutations in LIPA.•None of the patients had CESD, and this disease is estimated to have a prevalence of only approximately 1/300.000 in Norway.