Tupaias (tree shrews) -- a new animal model for gallstone research. III. Cholesterol metabolism under different diets and CDCA

Aspirin does not inhibit cholesterol cholelithiasis in two established animal models

The effect of aspirin on cholesterol cholelithiasis was examined in the hamster and the prairie dog. In the prairie dog, diets were composed of semipurified components of chow, plus cholesterol (1.2%), with and without aspirin. Animals were studied for either 2 weeks or 4 weeks. Cholesterol gallstones were present in all groups at the end of each period; aspirin did not alter the incidence of cholelithiasis. All animals studied had cholesterol crystals in the bile when they were killed. Liver cholesterol levels in prairie dogs with and without aspirin tended to be lower in animals fed chow than in animals fed semipurified diets. There were no significant differences in cholesterol levels in the plasma or bile. The cholesterol saturation index of all biles approached unity when animals were fed chow with aspirin; animals fed the semipurified diets had cholesterol saturation indices of less than 1.0. The prairie dogs fed aspirin plus cholesterol in the semipurified diet showed increased levels of biliary chenodeoxycholic acid amidates and concomitant decreased levels of cholic acid amidates compared with animals fed the same diet without aspirin. Hamsters fed aspirin plus cholesterol in a semipurified diet tended to have a greater incidence of gallstones than animals given no aspirin (80% vs. 55%). Liver and bile cholesterol levels were similar with and without aspirin; plasma cholesterol levels increased significantly with aspirin [14.20 vs. 7.80 mmol/L (549 vs. 301 mg/dL)]. Lithogenic indices in all hamsters were above unity; biliary lipids, total lipid concentration, and biliary bile acid composition were similar. These results show that the addition of aspirin to a lithogenic diet does not reduce the incidence of cholelithiasis.

The effect of alfalfa-corn diets on cholesterol metabolism and gallstones in prairie dogs

Cholesterol gallstones were present in prairie dogs fed alfalfa plus corn with and without exogenous cholesterol (0.4%). The diets fed to the animals for eight weeks contained alfalfa plus corn in fixed proportions of 50:50, 85:15 and 15:85 (w/w). At sacrifice, all animals were healthy but had not gained weight; no deaths occurred during the experiment. Cholesterol gallstones were present in all groups. In the absence of exogenous cholesterol, the highest stone incidence was found in the animals which received the lowest fiber (highest corn) diets (alfalfa plus corn, 50:50, 67%; alfalfa plus corn, 15:85, 83%). Cholesterol gallstone incidence was 100% when exogenous cholesterol was added to the alfalfa plus corn diets (50:50 and 15:85). No pigment gallstones were detected in any animal. Liver and plasma cholesterol concentrations were highest in the animals receiving alfalfa plus corn (15:85) plus 0.4% cholesterol (4.29 mg/g, and 356 mg/dl, respectively). These values were lowest in animals receiving 85% alfalfa plus 15% corn without cholesterol (2.19 mg/g and 88 mg/dl, respectively). Lithogenic indices were below 1.00 in all groups. Biliary bile acids were mainly amidates of cholic acid and chenodeoxycholic acid, with the former predominating. Thus, gallstones can be formed in prairie dogs in the absence of exogenous cholesterol; gallstone incidence is reduced by dietary fiber.