The effect was examined of dietary sericin on the lipid and carbohydrate metabolism in rats fed with a high-fat diet. The rats were fed with a 20% beef tallow diet with or without sericin at the level of 4% for 5 weeks. The final body weight and white adipose tissue weight were unaffected by dietary manipulation. The consumption of sericin significantly reduced the serum levels of triglyceride, cholesterol, phospholipids and free fatty acids. Serum very-low-density lipoprotein (VLDL)-triglyceride, VLDL-cholesterol, low-density lipoprotein (LDL)-cholesterol and LDL-phospholipids were also significantly reduced by the sericin intake. Liver triglyceride and the activities of glucose 6-phosphate dehydrogenase and malic enzyme, the lipogenic enzymes, were also reduced by the sericin intake. Dietary sericin caused a marked elevation in serum adiponectin. The consumption of sericin suppressed the increases in plasma glucose and insulin levels after an intraperitoneal glucose injection. These results imply the usefulness of sericin for improving the lipid and carbohydrate metabolism in rats fed on a high-fat diet.

We previously reported that consumption of a resistant protein, sericin, reduces colon tumorigenesis, constipation, and serum TG in rodents. The pres

This study was conducted to elucidate the effects of dietary polyphenols on intestinal immunoglobulin A (IgA) response and mucin levels in rats fed a high-fat diet. In experiment 1, rats were fed a high-fat diet with or without several polyphenols including curcumin, rutin, D(+)-catechin, ellagic acid and quercetin at the level of 0.5%. Among the polyphenols examined, consumption of curcumin markedly elevated the level of IgA in feces and colon contents. In experiment 2, rats were fed a high-fat diet or a low-fat diet with or without 0.5% curcumin. Fecal level of IgA was higher in the high-fat diet group than in the low-fat diet group. In the rats fed the high-fat diet, dietary curcumin elevated fecal IgA, but not in those fed the low-fat diet. These results imply a novel effect of curcumin on intestinal IgA in animals fed a high-fat diet.

We have recently reported that soluble dietary fibre, glucomannan, increased colonic alkaline phosphatase (ALP) activity and the gene expression without affecting the small-intestinal activity and that colonic ALP was correlated with gut mucins (index of intestinal barrier function). We speculated that dietary fermentable carbohydrates including oligosaccharides commonly elevate colonic ALP and gene expression as well as increase mucin secretion and microbial fermentation. To test this hypothesis, male Sprague–Dawley rats were fed a diet containing 30 % lard with or without 4 % fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), raffinose (RAF) and lactulose (LAC), which are non-digestible oligosaccharides or isomalto-oligosaccharides (IMOS; some digestible oligosaccharides) for 2 weeks. Colon ALP activity, the gene expression and gut luminal variables including mucins, organic acids and microbiota were measured. Colonic ALP was significantly elevated in the FOS, RAF and LAC groups, and a similar trend was observed in the GOS group. Colonic expression of intestinal alkaline phosphatase (IAP-I), an ALP gene, was significantly elevated in the FOS, GOS and RAF groups and tended to be increased in the LAC group. Dietary FOS, GOS, RAF and LAC significantly elevated faecal mucins, caecaln-butyrate and faecal ratio ofBifidobacteriumspp. Dietary IMOS had no effect on colonic ALP, mucins, organic acids and microbiota. Colon ALP was correlated with mucins, caecaln-butyrate and faecalBifidobacteriumspp. This study demonstrated that non-digestible and fermentable oligosaccharides commonly elevate colonic ALP activity and the expression ofIAP-I, with increasing mucins and microbial fermentation, which might be important for protection of gut epithelial homoeostasis.