Leaf Ethanol Extract of Dimocarpus longan Lour. Ameliorates Type 2 Diabetes Mellitus in Rats by Regulating Metabolic Pathways and Gut Microbiota.

Abstract

Background: The leaves of Dimocarpus longan Lour. are used unilaterally as Chinese herbal medicines to treat diabetes in Chongzuo and Hezhou, Guangxi, but the mechanism of its treatment of diabetes is not yet clear, and further research is needed.

Methods: This study examined the effects of leaf ethanol extract of D.s longan Lour. on metabolic pathways and gut microbiota in rats with type 2 diabetes mellitus (T2DM). The rats were randomly divided into four groups: HG + HFD (T2DM model, fed with high-sugar and high-fat diet), control (regular diet), MET (positive metformin), and LYY (leaf ethanol extract of D. longan Lour). Metabolite profiles and gut microbiota composition were analyzed using liquid chromatography_mass spectrometry and 16S rDNA sequencing.

Results: Metabolomics analysis revealed 61 distinct metabolites in the LYY group, such as Leu-Pro and taurolithocholic acid 3-sulfate, which influence valine, leucine, and isoleucine metabolism, unsaturated fatty acid biosynthesis, fatty acid metabolism, bile secretion, and pyruvate and propanoate metabolism. Additionally, 16S rDNA sequencing showed that LYY significantly altered the abundance of gut microbiota such as Ligilactobacillus and Desulfobacterota (vs. HG + HFD group, p < 0.05).

Conclusion: LYY improved T2DM in rats may be associated with modulating metabolite levels and indirectly regulating glucose metabolism balance through changes in gut microbiota abundance. The efficacy of LYY in treating T2DM in rats may be related to the regulation of six metabolic pathways; it increased the abundance of Ligilactobacillus and Christensenellaceae _ R-7 _ group and decreased the abundance of Desulfobacterota, Colidextribacter, and Oscillibacter, thereby promoting impaired glucose tolerance and indirectly regulating the balance of glucose metabolism.