Dietary polyphenols as antidiabetic agents: Advances and opportunities

Dietary polyphenols have been widely investigated as antidiabetic agents in cell, animals, human study, and clinical trial. The number of publication (Indexed by Web of Science) on “polyphenols and diabetes” significantly increased since 2010. This review highlightstheadvancesandopportunitiesofdietarypolyphenolsasantidiabeticagents. Dietary polyphenols prevent and manage Type 2 diabetes mellitus via the insulin-dependent approaches, for instance, protection of insulin-independent approaches including inhibition of glucose absorption, inhibition of digestive enzymes, regulation of intestinal microbiota, modification of inflammation response, and inhibition of the formation of advanced glycation end products. More-over, dietary polyphenols ameliorate diabetic complications, such as vascular dysfunction, nephropathy, retinopathy, neuropathy, cardiomyopathy, coronary diseases, renal failure, and so on. The structure–activity relationship of polyphenols as antidiabetic agents is still not clear. The individual flavonoid or isoflavone has no therapeutic effect on diabetic patients, although the clinical data are very limited. Resveratrol, curcumin, and anthocyanins showed antidiabetic activity in human study. How hyperglycemia influences the bioavailability and bioactivity of dietary polyphenols is not well under-stood. An understanding of how diabetes alters the bioavailability and bioactivity of dietary polyphenols will lead to an improvement in their benefits and clinical outcomes. Cinnamon extracts were given to mice with fat-rich diet and low-dose STZ induced diabetes for 14 days. Blood glucose concentrations decreased significantly in all cinnamon extract groups compared to the control group. These results suggest that both procyanidinic type A and type Bacteroidetes and a reduced amount of the phylum Firmicutes Lachnospiraceae NK4A136 group and Alisties , affecting the release of intestinal hormones for regulating insulin release. The antidiabetic activity of brown seaweed Lessonia nigrescens ethanolic extract (LNE), including phenolics and flavonoids, was investigated in type 2 diabetic mice fed with a high-sucrose/high-fat diet by (Zhao et al., 2018). They showed that the of LNE increased the growth of Barnesiella , Helicobacter and Turicibacter , whichwere able tostimulate the host’s antidiabetic effect, accompanied with the modification in the gene and protein expression of hepatic phosphatidylinositol 3-kinase and c-Jun N-terminal kinase.