Dietary plant sterols prevented cholesterol gallstone formation in mice.

Cholesterol gallstone disease is a common global condition. This study investigated the role of plant sterols (PS) in the prevention of gallstone formation and the underlying mechanisms. Adult male mice were fed a lithogenic diet (LD) alone or supplemented with PS (LD-ps), phospholipids (LD-pl) or both PS and phospholipids (LD-ps/pl) for 8 weeks. Incidences of gallstone formation were compared among the groups. Lipids in the bile, liver and serum were analyzed. The expression of genes involved in cholesterol absorption, transport and metabolism in the liver and small intestine was determined. The incidences of gallstone formation were 100% (10/10), 20% (2/10), 100% (10/10) and 40% (4/10) in the LD, LD-ps, LD-pl and LD-ps/pl groups, respectively. Serum cholesterol and intestinal cholesterol absorption were decreased in PS-supplemented mice. The expression of genes related to cholesterol transport and metabolism in the liver was down-regulated by dietary PS. PS supplementation decreased Niemann-Pick C1-like 1 expression in the small intestine and reduced intestinal cholesterol absorption. Our results demonstrated that PS could inhibit intestinal cholesterol absorption and thus prevent cholesterol gallstone formation.

FMO3 and its metabolite TMAO contribute to the formation of gallstones.

Trimethylamine-N-oxide (TMAO) is a metabolite derived from trimethylamine (TMA), which is first produced by gut microbiota and then oxidized by flavin-containing monooxygenase 3 (FMO3) in the liver. TMAO may contribute to the development of diseases such as atherosclerosis because of its role in regulating lipid metabolism. In this study, we found that high plasma TMAO levels were positively associated with the presence of gallstone disease in humans. We further found increased hepatic FMO3 expression and elevated plasma TMAO level in a gallstone-susceptible strain of mice C57BL/6J fed a lithogenic diet (LD), but not in a gallstone-resistant strain of mice AKR/J. Dietary supplementation of TMAO or its precursor choline increased hepatic FMO3 expression and plasma TMAO levels and induced hepatic canalicular cholesterol transporters ATP binding cassette (Abc) g5 and g8 expression in mice. Up-regulation of ABCG5 and ABCG8 expression was observed in hepatocytes incubated with TMAO in vitro. Additionally, in AKR/J mice fed a LD supplemented with 0.3% TMAO, the incidence of gallstones rose up to 70% compared with 0% in AKR/J mice fed only a LD. This was associated with increased hepatic Abcg5 and g8 expression induced by TMAO. Our study demonstrated TMAO could be associated with increased hepatic Abcg5/g8 expression, biliary cholesterol hypersecretion and gallstone formation.