Cholesterol metabolism in gnotobiotic gerbils.

Germfree gerbils were associated with a murine-derived hexaflora which produced only minor changes in the primary bile acid pattern of rats. These hexaflora-associated gerbils had relatively small ceca (4% of body weight) and reproduced well. Although serum cholesterol levels of both conventional and hexaflora-associated gerbils increased in response to dietary cholesterol, the hexaflora-associated gerbil showed a greater elevation in serum cholesterol than the conventional gerbil when maintained on a diet containing 0.1% cholesterol. This increase in serum cholesterol manifested itself almost totally in the very low density lipoprotein and low density lipoprotein fractions. The fecal bile acids of the hexaflora-associated gerbil were largely deconjugated, but very little further modification of either cholic or chenodeoxycholic acid had taken place. The data suggest that in the absence of elements of the intestinal microflora that can express a bile acid-modifying potential, and particularly a 7-alpha-dehydroxylating capacity, catabolism of cholesterol to bile acids is reduced, and cholesterol accumulates in the very low density and low density serum lipoprotein fractions.