Study on the Mechanism of the Leaves of Dimocarpus longan Lour. in the Management of Type 2 Diabetes based on Metabolomics

Background: Diabetes mellitus (DM) is a chronic metabolic disease. The leaves of Dimocarpus longan Lour. (LYY), a well-known traditional Chinese medicine (TCM) with Guangxi national characteristics often used in simple recipes to treat DM has attracted increasing attention. In this study, we investigated the therapeutic effects of LYY in diabetic rats from a metabolomic perspective. Methods: The type 2 diabetes (T2DM) rat model was induced by a high-sugar and high-fat diet (HSFD) combined with 40 mg/kg streptozotocin (STZ). After oral administration of LYY (10.7 g/kg) for 28 d, their weight, fasted blood glucose (FBG), blood lipid levels, and inflammatory factors were assessed. The feces, urine, and serum samples of the rats were collected, and proton nuclear magnetic resonance (1H-NMR) technology was used to explore the changes in the sample's metabolism spectrum and analyze the relevant targeted metabolic pathways. Results: Compared with the diabetes group, LYY rats significantly delayed the reduction of body weight and decreased the FBG level (P <0.01); the levels of total cholesterol (TC), triglycerides (TG), and low-density lipoprotein-cholesterol (LDL-C), IL-6, and TNF-α in serum significantly reduced (P < 0.05, 0.01), and the level of high-density lipoprotein-cholesterol (HDL-C) significantly increased (P < 0.01). 2 candidate biomarkers were identified from feces samples, and 4 associated metabolic pathways were discovered. 13 potential biomarkers were screened from urine samples, leading to the identification of 16 related metabolic pathways. Similarly, 5 potential biomarkers were screened from serum samples, and 11 related metabolic pathways were found. Conclusion: LYY can regulate the metabolic disorder caused by T2DM by regulating amino acid metabolism, amino acid synthesis, and tricarboxylic acid cycle, which provides a specific reference for the clinical treatment of T2DM.