Effect of amylomaize starch on cholesterol and bile acid metabolisms in germfree (axenic) and conventional (holoxenic) rats

Abstract

Summary. Germfree and conventional rats were given a semi-synthetic diet containing either normal cornstarch or an amylomaize starch. The experimental groups thus formed were compared to assess the effects of these two types of starch and to determine if digestive tract microflora was involved in these effects.The presence of amylomaize starch decreased body growth in germfree and conventional rats, increasing food intake in the former and decreasing it in the latter. In conventionals, amylomaize starch decreased the apparent digestibility of the ration only slightly, while in germfrees it diminished apparent digestibility considerably. The cecal weight of germfree animals was not modified by amylomaize starch but that of conventional rats was increased fourfold.In both types of rat, amylomaize starch largely decreased the plasma concentration of cholesterol, largely increased the total amount of bile acids in the small intestine but slightly modified the fecal elimination of cholesterol and bile acids. It augmented the cholesterol concentration in the liver of germfrees and decreased it in conventionals while, on the contrary, it diminished the total amount of bile acids in the hind gut in the former and augmented it in the latter. This starch did not change bile acid deconjugation in conventional rats but considerably decreased other bacterial transformations of cholesterol and bile acids.Digestive tract microflora was undoubtedly involved in the action of amylomaize starch on cecal weight, ration digestibility, food intake, hepatic cholesterol concentration, the amount of bile acid in the hind gut and obviously in the transformation of cholesterol and bile acids. It did not play a role in the other effects of this starch : the strong decrease in the concentration of plasma cholesterol was the direct effect of amylomaize starch on rat metabolism.Introduction.

Effect of Amylomaize Starch on Plasma Lipoproteins of Lean and Obese Zucker Rats.

“…In addition, liver cholesteryl ester concentrations were also decreased (Table 1). These effects of amylomaize diet in Zucker rats were similar to those previously reported in conventional or germ-free rats of the Fisher strain [6].…”

“…Hypocholesterolemic effects of starch feeding have been previously observed in rats and rabbits fed potato starch [5] . Recently it was reported that a diet containing an amylomaize starch decreased plasma cholesterol levels by about 40% in conventional or in germ-free rats [6]. However, this study did not examine the precise effects of this starch on the different plasma lipoproteins.…”

“…Among the several biological modifications within the gut reported in rats and hamster fed this starch [6,20,21], the increased biliary secretion of bile acid would agree with an accelerated catabolism of lipoproteins by the liver. Another hypothesis to explain the effects of this starch on plasma lipids concerns its effect on insulin and glucagon levels, since the intestinal hydrolysis of amylose-rich starch and therefore the glucose release are slow.…”

Intestinal mucosal morphometry and ileal epithelial renewal in conventional and germ-free rats fed an amylomaize starch diet

“…Similar observations have also been reported for various other poorly digestible carbohydrates and have been related to the decrease in caecal pH in CV rats fed these carbohydrates and to a modification of the bacterial population in the large intestine (Andrieux et al, 1989). It was also noted that, with amylomaize starch compared with normal starch, caecal size increased 4-fold in CV rats (Sacquet et al, 1983).…”

“…As reported in a previous experiment with lactose (Meslin et al, 1981 there was no relation between bile acid pool and epithelial renewal because a similar increase in bile acid pool was observed in CV and GF rats fed amylomaize starch (Sacquet et al, 1983;Andrieux et al, 1989) whereas epithelium renewal was modified only in CV rats.…”