Abstract: The present study examined the contents and glucose lowering capacities of soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) from tartary buckwheat bran, and it comparatively evaluated the effect of supplementation with the two types of dietary fiber on glucose and lipid metabolism in high-fat diet/streptozotocin-induced diabetic mice. The content of IDF in tartary buckwheat bran was (19.52 ± 0.21)%, approximately 5 times as high as that of SDF ((4.02 ± 0.19)%). SDF was more effective than IDF in lowering blood glucose at the same dose. However, when administered at a dose five times higher than SDF dose, IDF was more effective in lowering serum total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) than SDF; and promoted insulin secretion, improved glucose tolerance, lowered hepatic total cholesterol (TC) and stimulated the production of short-chain fatty acids (SCFAs) as effectively as did SDF. Therefore, both SDF and IDF could improve glucose tolerance and lower lipid accumulation in serum and liver, which were closely associated with the increase in the production of SCFAs in the cecum content. The results from this study may provide a scientific basis for understanding the regulatory effect of different types of dietary fiber from cereals on glucose and lipid metabolism.

Key words: tartary buckwheat; dietary fiber; glucose metabolism; lipid metabolism