Effect of apolipoprotein E polymorphism on bile lipid composition and the formation of cholesterol gallstone

It remains a matter of controversy whether possession of the apolipoprotein E4 (apoE4) allele is a genetic risk factor for the formation of cholesterol gallstones. The aim of the present study was to test this hypothesis by investigating the effect of apoE4 on bile lipid composition in normal subjects and in patients with cholesterol gallstones and to evaluate the distributions of apoE alleles in these two groups.

The study population consisted of 79 patients who underwent open or laparoscopic cholecystectomy for symptomatic cholesterol gallstone disease. The control group (n = 53) included 11 patients with benign gallbladder polyps and 42 normal subjects acting as donors in living donor liver transplantation. The apoE genotypes were assessed by dot blot hybridization with digoxigenin-labeled probes. Bile lipid composition was determined by enzymatic assays and high performance liquid chromatography.

Bile lipid composition and cholesterol saturation index (CSI) were similar in the control subjects harboring the apoE4 allele and those without apoE4 (mean CSI, 85.9% and 72.2%, respectively, p = 0.69). Likewise, in the cholesterol gallstone patients, bile lipid composition and CSI were similar in the patients with and without apoE4 allele (mean CSI, 134.9% vs 152.2%, p = 0.6). Furthermore, the prevalence of the apoE4 allele was similar in the patients with cholesterol gallstones and in the control group (8.5% vs 7.6%, p = 0.46, OR = 0.88; 95% CI = 0.64-1.22).

The apoE4 allele is not a contributory factor to cholesterol gallstone formation, at least in the Japanese population.