Fecal Losses of Sterols and Bile Acids Induced by Feeding Rats Guar Gum Are Due to Greater Pool Size and Liver Bile Acid Secretion

Abstract

The effect of dietary guar gum (GG, 7.5%) on lipid metabolism and on bile acid secretion and reabsorption was investigated in rats adapted to cholesterol-free or 0.3% cholesterol diets. Compared with controls (fiber-free/cholesterol-free), rats fed cholesterol had significantly elevated plasma and liver cholesterol and triglyceride. In these rats, GG had a potent plasma cholesterol-lowering effect and also counteracted the liver accumulation of triglyceride and cholesterol esters. Fecal excretion of sterols, the major route of cholesterol elimination, was markedly enhanced by GG, especially in rats fed the cholesterol-containing diet (P < 0.001). The biliary bile acid flux into the small intestine was enhanced by dietary cholesterol (+30%) or GG (+52%) or both (P < 0.001). The fecal excretion of bile acids was significantly elevated by GG alone (+74%) and by dietary cholesterol (+190%). Small intestine reabsorption of bile acids appears to be significantly enhanced by GG, which also enhanced the transfer of bile acids into the large intestine, hence a greater fecal loss of steroids, although bile acid reabsorption was very effective in the cecum. GG feeding induced liver hydroxymethyl-glutaryl coenzyme A (HMG CoA) reductase, even in cholesterol-fed rats, as well as cholesterol 7 alpha-hydroxylase (P < 0.001). The cholesterol-lowering effect of GG thus appears to be mediated by an accelerated fecal excretion of steroids and a rise in the intestinal pool and biliary production of bile acids. Although liver HMG CoA reductase and cholesterol 7 alpha-hydroxylase are induced in parallel, this is not sufficient to compensate for fecal steroid losses.

Comparative gastrointestinal and plasma cholesterol responses of rats fed on cholesterol-free diets supplemented with guar gum and sodium alginate

“…The increased faecal excretion of total bile acids observed in rats fed GG and SA ( Fig. 2(b)) is consistent with studies in laboratory rats fed cholesterol-free diets supplemented with a range of soluble NSP including GG at similar inclusion rates to those used in the present study (Gallaher et al 1992;Overton et al 1994;Moundras et al 1997;Buhman et al 1998). Studies in animals fed cholesterol-containing diets (for example, see Trautwein et al 1998Trautwein et al , 1999, and in human subjects fed normal diets (Jenkins et al 1980;Bosaeus et al 1986), have also reported increased faecal bile acid excretion following consumption of soluble NSP.…”

“…Studies in animals fed cholesterol-containing diets (for example, see Trautwein et al 1998Trautwein et al , 1999, and in human subjects fed normal diets (Jenkins et al 1980;Bosaeus et al 1986), have also reported increased faecal bile acid excretion following consumption of soluble NSP. Approximately a twofold increase in neutral sterol output (not determined in the present experiment) has been observed in rats fed cholesterol-free diets containing 75 g GG/kg (Moundras et al 1997) and 50 g psyllium husk/kg (Buhman et al 1998), and a similar increase in endogenous sterol loss may also contribute to the cholesterol-lowering effect of both GG and SA observed in the present experiment. There are variable responses to different NSP sources (Story et al 1997), with some NSP (e.g.…”

Dietary acetic acid reduces serum cholesterol and triacylglycerols in rats fed a cholesterol-rich diet

“…Faecal neutral steroids and acid steroids were extracted from collected faeces as described previously (Moundras et al 1997) …”

Hypolipidemic Effect of the Autoclaved Extract Prepared from Pea (<i>Pisum sativum</i> L.) Pods In Vivo and In Vitro

“…In particular, SDF has stimulatory effects on fecal lipid excretion, including fecal triglyceride and cholesterol (3,4). Fecal lipid excretion was stimulated in the intestine by soluble fibers, such as guar gum or pectin, and soluble fibers also induced 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and cholesterol 7alpha-hydroxylase (CYP7A) (5,6). IDF adsorbs moisture from food residue and increases the amount of feces (7).…”