Inhibition of Ceramide Decreased the Expression of ATP-Binding Cassette Transporter G5/8 mRNA in an Animal Model of Cholesterol Gallstone

Background: The increased risk of gallstone has been reported in patients with ATP-binding cassette (ABC) transporter polymorphism. The half-transporters ABCG5 and ABCG8 mediate the efflux of cholesterol in hepatocytes and the intestine. We investigated whether ceramide plays a role in cholesterol efflux through the ABC transporters. Methods: Six-week-old C57BL/6J mice were assigned to 3 groups. The normal group (n = 5) was fed a normal chow diet, the cholesterol group (n = 10) was fed a lithogenic diet, and the myriocin group (n = 15) was fed the lithogenic diet and myriocin, a specific inhibitor of serine-palmitoyl transferase. After 6 weeks, the ABCG5 and ABCG8 transporters were analyzed. Results: The rate of cholesterol gallstone formation in cholesterol group was also higher than that in normal and myriocin groups (0, 70, and 40%, respectively). ABCG5 and ABCG8 mRNA levels were significantly increased in cholesterol group and less increased in myriocin group, relative to that in normal group (p < 0.05). Conclusions: The inhibition of ceramide biosynthesis by myriocin suppressed gallstone formation and ABCG5/8 mRNA expression. We expect that ceramide's role as a regulator of the ABCG5/8 transporter might be linked to cholesterol gallstone formation.