Baicalein, a dietary flavonoid, enhances the insulin‐sensitizing effect of metformin to prevent type 2 diabetes via the regulation of lipid metabolism and gut microenvironment

Abstract

AbstractBaicalein is a natural flavonoid abundant in various foods and dietary plants, including Tuber aestivum and Oroxylum indicum. In this study, we investigated the role of baicalein in enhancing the insulin‐sensitizing effect of metformin in mice with prediabetes. Baicalein, when combined with 25% of normal‐dose metformin, achieved a diabetes‐reversion rate of 80%, which was 1.86‐fold that of normal‐dose metformin. Mechanistically, baicalein enhanced the insulin‐sensitizing effect of metformin on lipid metabolism by inhibiting de novo lipogenesis through the AMP‐activated protein kinase/SREBP‐1c/FASN pathway and by inducing fatty‐acid β‐oxidation through the upregulation of ACSL1, CPT1A, EHHADH, and acyl‐CoA dehydrogenases (ACADL/ACADM/ACADS). Meanwhile, baicalein enhanced the insulin‐sensitizing effect of metformin via the modulation of the gut microenvironment by enriching probiotics, especially Akkermansia by 53.4‐fold, depleting opportunistic pathogens, and strengthening the intestinal barrier. The improved gut microenvironment led to the alleviation of chronic endotoxemia, as evidenced by decreased levels of lipopolysaccharide and proinflammatory cytokines. Furthermore, baicalein enhanced the effect of metformin on decreasing the circulating level of branched‐chain amino acids (BCAAs), which further improved insulin sensitivity by normalizing the mTORC1/p70S6K/IRS1 signaling pathway and de novo lipogenesis. Moreover, the role of baicalein in enhancing the insulin‐sensitizing effect of metformin was verified by an oleic acid‐induced steatosis model and a BCAA‐induced insulin resistance model in hepatocytes. Our study laid a theoretical foundation for developing baicalein into a dietary supplement for diabetes prevention. The diverse mechanisms of food‐derived flavonoids can be applied in the development of dietary supplements to enhance the efficacy of oral hyperglycemic agents currently used in clinics.