The total alkaloids of Berberidis Cortex alleviate type 2 diabetes mellitus by regulating gut microbiota, inflammation and liver gluconeogenesis

Type 2 diabetes mellitus (T2DM) has become a public health problem worldwide. There is growing interest in finding drugs to treat T2DM from herbal medicine. Berberidis Cortex is a traditional Tibetan herb commonly used in the treatment of T2DM, and alkaloids are its main active components. However, the anti-diabetic mechanisms of the total alkaloids of Berberidis Cortex (TBC) remain unclear. The aim of this study was to evaluate the anti-T2DM efficacy of TBC and reveal the mechanisms behind its effects. UPLC-Q-Exactive Orbitrap MS technology was employed to qualitatively identify alkaloid components in TBC. T2DM rat models were induced by high-fat diet combined with streptozotocin, and then treated with different doses of TBC (43.5, 87, 174 mg/kg/d) for 40 days. Biochemical parameters, such as fasting blood glucose (FBG), oral glucose tolerance test (OGTT), glycated serum protein (GSP), homeostatic model assessment of insulin resistance (HOMA-IR), total cholesterol (TC), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C), alongside H&E and PAS staining were used to evaluate the anti-diabetic activity of TBC. More importantly, metagenomics, transcriptomics, targeted metabolomics, and Western blot analysis were integrated to reveal the underlying mechanisms of TBC for T2DM treatment. TBC significantly reduced the levels of FBG, OGTT, GSP, HOMA-IR, TC, TG, and LDL-C, and improved the histopathological alterations of pancreatic and liver tissues in T2D rats. It also reduced serum levels of lipopolysaccharide (LPS) and several pro-inflammatory cytokines (IL-6, IL-1β and TNF-α). Gut microbiome analysis by metagenomics proved that TBC could improve gut microbiota dysbiosis, including an increase in some beneficial bacteria (e.g., Bifidobacterium pseudolongum and Lactobacillus acidophilus ) and a decrease in some harmful bacteria (e.g., Marvinbryantia and Parabacteroides ). Western blot analysis found that TBC significantly up-regulated the expression of three intestinal barrier related tight junction proteins (ZO-1, occludin, and claudin-1), and effectively suppressed several key proteins in the TLR4/MyD88/NF-κB inflammatory cascade, including TLR4, MyD88 and p-NF-κB p65. Moreover, hepatic transcriptomics analysis further revealed the regulatory role of TBC on gluconeogenesis related genes, such as Pgc, and Creb1. Targeted metabolomics and Western blot analysis showed that TBC improved BAs dysregulation in T2DM rats, specifically increasing TCDCA and CA levels, thereby activating several proteins in the FXR/FGF15 signaling axis (i.e., FXR, FGF15 and FGFR4), and then decreased the expression of p-CREB1 and PGC-1α to inhibit liver gluconeogenesis. TBC can significantly improve hyperglycemia, insulin resistance, hyperlipidemia, and inflammation in T2DM rats. The mechanism is related to the regulation of multiple links, including improving gut microbiota dysbiosis, protecting the intestinal barrier by up-regulating the expression of three tight junction proteins, reducing inflammation by inhibiting the LPS/TLR4/MyD88/NF-κB pathway, and inhibiting liver gluconeogenesis by regulating BAs/FXR/FGF15 and CREB1/PGC-1α signaling pathways.