Biliary lipids in New World monkeys: dietary cholesterol, fat, and species interactions.

The separate effects contributed by dietary cholesterol and dietary fat on several parameters of biliary lipid metabolism thought to be important in the genesis of cholesterol gallstones were examined in squirrel and cebus monkeys fed diets containing either corn or coconut oil from birth. Half the monkeys were also fed cholesterol. In gallstone-susceptible squirrel monkeys, corn oil tended to decrease the bile acid pool size and decrease the percentage of taurochenodeoxycholic acid. Dietary cholesterol effected major changes in gallbladder bile molar percent lipid composition with significantly increased cholesterol saturation indices that exceeded the metastable-labile limits. The supersaturated biles notwithstanding, none of the monkeys developed gallstones and only one had cholesterol crystals in its bile. By contrast, the gallstone-resistant cebus monkeys experienced less remarkable shifts in biliary lipid composition during dietary challenges of cholesterol and fat. The data are consistent with the hypothesis that neither a diminished bile acid pool size nor bile supersaturated with cholesterol are sufficient in themselves to result in gallstone formation in immature monkeys.