Dietary fiber and cholesterol and bile acid metabolisms in axenic (germfree) and holoxenic (conventional) rats. I. -- Effect of wheat bran.

Axenic (GF) and holoxenic (CV) rats were given a semi-synthetic diet containing no fiber (0) or 10 p. 100 bran (B). The GFO, GFB, CVO and CVB groups were compared to assess the action of the flora and the bran. The bran diet did not change body growth, food intake or cecal water content. It caused only a slight decrease in the digestive utilization of the diet in the holoxenic rats and a decline in cecal weight in the axenic rats. The bran diet modified unabsorbed cholesterol transit in both types of rats, and slightly altered dietary cholesterol absorption which was a little lower in axenics than in holoxenics. In the former (GF), the bran-containing diet dit not change either the plasma or the hepatic cholesterol concentration. In the latter (CV), it increased plasma cholesterol which was lower in CVO rats than in the other three groups and decreased hepatic cholesterol which was thus lower in the CVB lot than in the others. The bran diet reduced fecal cholesterol elimination in axenic and holoxenic rats. This decrease was a little higher in the latter. The digestive tract microbial flora was thus implicated in the effect of bran on those characteristics of cholesterol metabolism. The bran did not change fecal bile acid composition in the axenics. In the holoxenics, it contributed to make this composition uniform because without bran, individual compositions varied. The microbial flora thus changed many aspects of bran action on cholesterol and bile acid metabolisms. But total cholesterol and bile acid elimination was only slightly affected by those two factors.