Cholesterol-gallstone formation: more than a biliary lipid defect?

BILIARY AND PANCREATIC DISEASE IN PREGNANCY

Pregnancy is a physiological condition that affects all organs. Diseases unrelated to pregnancy may present coincidentally during pregnancy or may be exacerbated by pregnancy, and may increase maternal and/or fetal morbidity or mortality. Compared with many other systems, the changes within the biliary tree and pancreas are relatively minimal. However, pregnancy is associated with an increased likelihood of cholelithiasis, which can have significant implications for the parturient.

Targeted deletion of Gpbar1 protects mice from cholesterol gallstone formation

The Gpbar1 [G-protein-coupled BA (bile acid) receptor 1] is a recently identified cell-surface receptor that can bind and is activated by BAs, but its physiological role is unclear. Using targeted deletion of the Gpbar1 gene in mice, we show that the gene plays a critical role in the maintenance of bile lipid homoeostasis. Mice lacking Gpbar1 expression were viable, developed normally and did not show significant difference in the levels of cholesterol, BAs or any other bile constituents. However, they did not form cholesterol gallstones when fed a cholic acid-containing high-fat diet, and liver-specific gene expression indicated that Gpbar1-deficient mice have altered feedback regulation of BA synthesis. These results suggest that Gpbar1 plays a critical role in the formation of gallstones, possibly via a regulatory mechanism involving the cholesterol 7alpha-hydroxylase pathway.