Polysaccharides in Berberis dasystachya improve intestinal flora depending on the molecular weight and ameliorate type 2 diabetes in rats

Abstract

This study investigated the effects of ultra-filtered polysaccharides from Berberis dasystachya Maxim. (UBDP) on the gut microbiota and glucose metabolism in high-fat diet/streptozotocin -induced diabetic rats, and clarified the possible action mechanisms of UBDP in the treatment of type 2 diabetes mellitus (T2DM). The results showed that UBDP administration for 4 weeks significantly ameliorated glucose tolerance, improved organ function, reduced fasting blood glucose and HbA1c levels, decreased the glycosylated hemoglobin index, improved insulin sensitivity of the pancreas, and reduced colon morphogen and oxidative stress in the diabetic rats (P < 0.05). Furthermore, the antihyperglycemic effect of 200 mg/kg UBDP was the most significant. 16S rDNA sequencing evaluated the changes in the gut microbiota of T2DM rats, and metabolites were analyzed through metabolomic profiling. Four weeks of UBDP supplementation significantly increased the relative abundance of Firmicutes and the levels of short-chain fatty acids, and the phenotypes of the gut microbiome also changed accordingly. This suggested that the gut microbiota might partially mediate the hypoglycemic effects of UBDP supplementation. Moreover, 200 mg/kg UBDP treatment significantly improved the metabolic disorder in the diabetic rats; 27 possible biomarkers were identified, mainly involved in lysine degradation; phenylalanine, tyrosine, and tryptophan biosynthesis; tyrosine metabolism; bile secretion; and nicotinate and nicotinamide metabolism. To a certain extent, the levels of these biomarkers of UBDP supplementation returned to normal levels, which was related to the gut microbiota. These findings provide a theoretical foundation for the development and application of polysaccharides from Berberi dasystachya.