Study on the mechanism on Yi-guan-jian decoction alleviating cognitive dysfunction in type 2 diabetes mellitus

Ethnopharmacological relevance: Yi-guan-jian decoction (YGJ) is a traditional Chinese medicine prescription commonly used for treating syndromes associated with Yin deficiency in the liver and kidney, as well as Qiobstructed in liver. Aim of the study: YGJ has shown potential alleviating cognitive dysfunction in type 2 diabetes mellitus (T2DM). However, the precise mechanisms are not yet fully understood. This study aims to reveal the mechanism by which YGJ alleviates cognitive dysfunction in T2DM. Materials and methods: Various doses of YGJ were administered to T2DM rats with cognitive dysfunction for 8 weeks. The positive control group received a combination of metformin and memantine. Cognitive function was assessed in T2DM rats using the Morris water maze test during treatment. Changes in gut microbiota and bile acids in the intestine were evaluated, and their interactions analyzed. Additionally, this study also evaluated the expressions of inflammatory markers (IL-1 beta,TNF-alpha, IL-16, IL-18 and CRP protein), Tau protein, neurotransmitter (5-HT and GABA), and bile acid receptor (FXR, PXR, VDR, and TGR5). Results: YGJ significantly alleviated insulin resistance and hyperlipidemia, reduce the levels of inflammatory factors in serum and hippocampus, and decreased mortality in T2DM rats. The Morris water maze test indicated that YGJ reduced the escape latency and increased platform crossing frequency, thereby improving cognitive function in T2DM rats. Furthermore, YGJ regulated the abundance of microorganisms associated with bile acid metabolism, including Romboutsia, Bacteroides, Turicibacter, Blautia, and Ruminococcus, thus regulating bile acid metabolism in T2DM rats. Additionally, YGJ also regulated bile acid metabolism by regulating intestinal FXR, PXR, VDR and TRG5 receptors. Conclusion: YGJ can alleviate glucose homeostasis, insulin sensitivity, lipid metabolism, neuroinflammation, cognitive function, as well as remodel intestinal flora and BA composition in CDT2DM rats, which is a potential complementary and alternative therapy for the prevention and treatment of CDT2DM. These effects may be associated that YGJ regulates the structure of intestinal flora and BA metabolism, and inhibits intestinal BA receptors FXR, PXR, TGR5, and VDR.