Hypoglycemic Effects and Mechanisms of Polyphenols From Myrica rubra Pomace in Type 2 Diabetes (db/db) Mice

The Myrica rubra pomace polyphenols (MRPP) were used to study their hypoglycemic effects and mechanisms using Type 2 diabetes (T2D) (db/db) mice as the model. The results showed that the oral administration of MRPP (low-dose myricitrin, 50 mg/kg BW by gavage; high-dose myricitrin, 250 mg/kg BW by gavage; and Myrica rubra pomace, 500 mg/kg BW by gavage) for 4 weeks significantly reduced fasting blood glucose, glycated serum protein, serum insulin, and insulin resistance index in mice, as well as the dyslipidemia in mice was improved. MRPP was able to improve the structural morphology of hepatocytes and pancreatic β-cells in diabetic mice. Its hypoglycemic mechanism may involve the upregulation of GLUT-4 and IRS-1 genes expression in the PI3K and AMPK signaling pathways, downregulation of GSK-3β, AMPK, PI3K, and AKT genes expression, and enhancement of the activity of enzymes related to glycogen synthesis and glucose metabolism. Research findings on 16S rRNA suggest that MRPP has the ability to alter the composition of the gut microbiota, impede the growth of harmful bacteria, and foster the growth of beneficial bacteria. Therefore, MRPP was capable of reshaping the specific gut microbial community and supporting its application as a novel supplement in functional foods for the treatment of T2D.