EFFECTS OF DIETARY-CHOLESTEROL AND TRIGLYCERIDES ON LIPID CONCENTRATIONS IN LIVER, PLASMA, AND BILE

Dietary cholesterol (CHL) and triglycerides (TC) can influence plasma, hepatic, and biliary lipid composition, but effects on lipids in thes e three compartments during the early stages of CHL gallstone formatio n have not been studied in parallel. We fed prairie dogs diets contain ing one of four test oils (safflower, coconut, olive, or menhaden) at either 5 or 40% of calories, in the presence of 0 or 0.34% CHL, for 3 wk. In the absence of dietary CHL, increases in dietary TG produced 50 -200% increases in the concentrations of biliary CHL and hepatic chole steryl ester (CE), while the concentrations of hepatic free CHL (FC) a s well as plasma FC and CE remained relatively unchanged. Increasing d ietary CHL to 0.34% resulted in increases in hepatic FC of approximate ly 50% for all four fats regardless of whether they were supplied at 5 or 40% of calories. CHL supplementation caused more pronounced increa ses in biliary CHL (200-400%), hepatic CE (50-200%), plasma FC (up to 100%), and plasma CE (up to 150%), and these increases were exacerbate d by concurrent supplementation of dietary fat and CHL (biliary CHL: 3 00-700%; hepatic CE: 100-250%; plasma FC: up to 165%; plasma CE: 100-3 50%). These results indicate that enhanced secretion of biliary CHL an d, to a lesser extent, increased synthesis of hepatic CE, may be prima ry mechanisms for maintaining the hepatic FC pool. Furthermore, dietar y CHL and high levels of fat intake are independent risk factors for i ncreasing biliary CHL concentrations, and adverse effects on lipid con centrations in plasma and bile tend to be ex acerbated by ingestion of diets rich in both fat and CHL.