The effect of dietary fibre on bile acid metabolism in rats

Abstract

1. Forty-eight male rats were fed sequentially for 14 d periods on diets containing different fibre contents. 2. One of the high-fibre diets was a commercial pelleted diet. The other was a low-fibre diet supplemented 3. At the end of each feeding period eight rats were killed. Liver microsomal cholesterol 7a-hydroxylase 4. The different diets did not significantly alter the total intestinal bile acids, but affected the distribution 5. On the high-fibre diets deoxycholate, and hyodeoxycholate tended to be increased. 6. On the low-fibre diets the a-, /3-and o-muricholic acids tended to be increased. 7. Liver microsomal cholesterol 7a-hydroxylase activity was lower in rats fed on the low-fibre and branwith zoo g wheat bran/kg.(EC 1.14.1.-) activity and bile acid content of small intestine and colon were determined. and qualitative pattern in the colon and small intestine.supplemented low-fibre diets compared with that in rats fed on the commercial pelleted diet.The effect of dietary fibre on rat bile acid metabolism has been investigated by several groups. The addition of bran to a semi-synthetic diet resulted in an increase in total bile acids in the small intestine of the rat (Eastwood & Boyd, 1967). Gustaffson & Norman (1969) using labelled cholate added to a semi-synthetic, commercial pelleted diet, and a semisynthetic diet supplemented with 200 g cellulose/kg, fed to rats showed that cholate and certain bile acid metabolites were increased in the small intestine on the commercial pelleted diet, but the addition of cellulose to the semi-synthetic diet had no effect on the small intestinal cholate pool. The total intestinal bile acid pool has been measured in Wistar rats fed on commercial pelleted and semi-synthetic diets (Fisher et ul. 1976). These authors showed that the total bile acid pool was increased on the commercial pelleted diet, but over-all there was no qualitative change in bile acid pattern. Sacquet et al. (1977) demonstrated that re-infecting the colon of germ free rats with heat-resistant bacteria isolated fromfaecesled to w-muricholic acid emerging as the major colonic bile acid. The metabolism of bile acids in the rat is as follows : W. G. BRYDON A N D O T H E R SIn this study we supplemented a semi-synthetic, low-fibre diet with 200 g wheat bran/kg and compared the pool size and pattern of bile acids in the small intestine and colon separately, with rats fed on a commercial pelleted or semi-synthetic diet alone.The rate limiting enzyme in the conversion of cholesterol to bile acids in the liver is the microsomal cholesterol 7a-hydroxylase (EC I . 14. I .-) (Danielsson et al. 1967). This oxygenase is located in the endoplasmic reticulum and is sensitive to changes in the enterohepatic circulation of bile acids. Liver microsomal cholesterol 7a-hydroxylase activity was measured during the different feeding regimens. MATERIALS A N D METHODSForty-eight mature male rats of Wistar strain were used in this study. The animals weighed approximately 200 g at the start of the experiment, and received ...

Fecal bile acid excretion and composition in response to changes in dietary wheat bran, fat and calcium in the rat

“…Bile acids have been shown to express cancer~pmmoting pr~ perties which are modified by dietary factors (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). In particular, fiber, fat and calcium have received increased attention for their ability to induce changes in the metabolism of bile acids which affect their potential for promoting the development of experimental colon cancer (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). Whereas both dietary fiber and calcium can suppress the experimental induction of colon cancer by carcinogens (10,12,(14)(15)(16)18), increased ingestion of fat has the opposite effect (7,13,19).…”

Nutritional Regulation of Pancreatic and Biliary Secretions

“…Accordingly, there is agreement about the lowering effect of dietary fibre on the bile acid pool in the hind gut, and this is much more important with bran (Brydon et al 1980; Sacquet et al 1 9 8 2~) than with pectin (Sacquet et al 19826). However, the bile acid pool was either unchanged (Sheard & Schneeman, 1980; Sacquet et al 1982~1, b), or enlarged (Brydon et al 1980) in the small intestine, by dietary fibre supplementation.…”

“…1980) or decreased (Sacquet et al 1982a). In the former case (Brydon et al 1980), wheat brain supplementation caused an increase in the small intestinal pool and an equivalent decrease in the colonic pool. In the latter study (Sacquet et al I982a), wheat bran had no effect on the small intestinal pool but strongly decreased that of the caecum and large intestine.…”

“…However, the bile acid pool was either unchanged (Sheard & Schneeman, 1980; Sacquet et al 1982~1, b), or enlarged (Brydon et al 1980) in the small intestine, by dietary fibre supplementation.…”

“…It has been suggested that an increase in colonic transit time with a low-fibre diet may, in part, account for the larger pool of bile acids in the colon (Brydon et al 1980). This was supported by Sacquet et al (1982~) until a relationship between the decreased transit time in the hind gut and the lowered bile acid pool in this part of the gut was clearly demonstrated after consumption of wheat bran (Riottot et al 1984).…”