Alleviating effects of polyphenol extract from rapeseed meal on type 2 diabetes in mice via modulation of gut microbiota and AMPK/mTOR signaling pathways.

Type 2 diabetes mellitus (T2DM) is a a complex metabolic disorder that poses a serious threat to human health. Although polyphenol extract from rapeseed meal (RMP) has demonstrated inhibitory activity against α-glucosidase, the alleviating effects on T2DM and the underlying molecular mechanisms remain largely unexplored in T2DM. In this study, the antidiabetic effects of RMP were investigated using a T2DM mouse model induced by a high-fat diet (HFD) combined with streptozotocin (STZ) administration. RMP remarkably relieved weight loss, lowered blood glucose levels (7.2 ± 0.9 mmol/L), reduced hyperglycemia, and improved insulin tolerance, while ameliorating hepatic oxidative stress. Notably, RMP regulated the gut microbiota composition by increasing the abundance of Alistipes, Bacteroidales, Allobaculum, Parabacteroides and reducing the abundance of Desulfovibrio and Oscillibacter. Metabolomic analysis identified 150 different metabolites between DN and RMP groups, of which 85 were up-regulated and 65 were down-regulated, including folate biosynthesis, pyrimidine metabolism, arginine biosynthesis, tyrosine metabolism, lipoic acid metabolism, and mTOR signaling pathway as a potential target. In addition, western blotting revealed that RMP activated the AMPK/mTOR signaling pathway, thereby contributing to improved glucolipid metabolism and reduced insulin resistance. These findings offer new insights into the antidiabetic potential of RMP, providing promising support for its application as a natural hypoglycemic functional ingredient.