Apolipoprotein B gene mutations and fatty liver in Japanese hypobetalipoproteinemia

Abstract

Background Familial hypobetalipoproteinemia (FHBL) is a hereditary disorder characterized by decreased plasma concentrations of low-density lipoprotein cholesterol. The best-characterized causes of FHBL are apolipoprotein B (apoB) gene mutations, which produce truncated apoB proteins. Fatty liver is thought to be frequent in FHBL, owing to impaired secretion of very-low-density lipoprotein from the liver. Homozygotes for FHBL present with extremely low concentrations of plasma lipids, and may suffer from deficiencies of fat-soluble vitamins. The objectives of this study were to identify apoB-defective FHBL subjects and investigate fatty liver in Japanese population. Methods We screened 14 hypocholesterolemic subjects for apoB gene mutations by PCR-SSCP and performed liver ultrasonography in a Japanese population. Results We identified an apoB-82 homozygote in one subject and an apoB-13.7 heterozygote in another subject. Four of 6 individuals with FHBL presented with fatty liver in those 2 FHBL families. Liver biopsy of the apoB-13.7 heterozygote, which had obesity and insulin resistance, showed severe fatty liver. The apoB-82 homozygote was asymptomatic with fat-soluble vitamin concentrations being normal, possibly due to spared secretion of apoB-48 from the intestine and increased plasma concentrations of high-density lipoprotein cholesterol. Conclusion ApoB gene mutations might not be rare and that fatty liver might be frequent in Japanese FHBL.