Protein Structure Based Studies On The Target And Mechanism Of Anti-diabetic Natural Products

This dissertation is composed of two chapters. Chapter Ⅰ was aimed to evaluate the inhibitory effects of compound 6, a derivative of kinsenoside, on VEGFR1 in vitro and evulate the hypoglycemic effects on type 2 diabetes db/db mice in vivo. Chapter Ⅱ was sought to apply virtual screening-based docking method to identify 11β-HSD1 inhibitors from natural-product chemical libraries and our research group.Chapter ⅠOriginally, six derivatives of kinsenoside were synthesized by a two-step chemical approach. In STZ induced rat diabetic model, C6 could significantly control the blood sugar level and the therapeutic activity was much better than the other derivatives. In the present study, a virtual screening approach had been used to determine the potential target of C6, vascular endothelial growth factor receptor 1 (VEGFR1) was observed to be occupied the active site with significant score of ICM docking grade.In order to confirm this hypothesis, the binding domains of VEGFb and VEGFR1 were expressed and purified by recombinant methods. In microscale thermophoresis test, VEGFb could closely combine with VEGFR1 with a dissociation constant value of 757±67.5 nM, while C6 remarkably inhibited the binding capacity with IC50 of 5.37±0.79μM which was much lower than that of other derivatives.In addition, at the end of animal experiment, treatment with C6 can reduce blood sugar level, ameliorate hyperlipmia, relieve peripheral insulin resistance and improved glucose toleranc. Histomorphological observation demonstrated that the damage on livers and kidneys were remarkable decreased and the pancreatic islet hyperplasi was inhibited with a dose-dependent manner. Furthermore, C6 treatment of diabetic mice reduced targeting VEGFb-regulated FATPs expression in cardiac muscles, and significantly decreased lipid deposition in skeletal muscle.VEGFb-VEGFR1 signal controls endothelial uptake and transport of fatty acids into muscles, impairing the insulin sensitivity and glucose uptake of peripheral tissues, thus, antagonism of VEGFb-VEGFR1 pathway was recognized as a novel pharmacological approach for the therapy of type 2 diabetes. The results indicate that C6 is a novel inhibitor of VEGFb-VEGFR1 signal pathway to prevent development of insulin resistance and type 2 diabetes. We propose that C6 represents a potential and promising treatment option for type 2 diabete.ChapterⅡGlucocorticoids influence a wide variety of physiologic processes, including lipid and glucose metabolism, immune modulation, cell growth, and anti-inflammatory responses. Excessive activation of glucocorticoid hormones (GCs) can result in metabolic syndromes with multiple clinical features, including insulin resistant diabetes, obesity, dyslipidemia, and hypertension.11β-hydroxysteroid dehydrogenase type 1(11β-HSD1), which converts inactive glucocorticoid into active glucocorticoid, can amplify the local levels and activities of GCs. The inhibition of 11P-HSD1 offers the ability to restore the metabolic action of insulin in these tissues. Consequently, the developments of 11β-HSD1 inhibitor drugs are urgently demanded. Natural products (NPs) have represented a cornerstone of pharmaceutical research, as they offer a diverse range of bioactive substructures, chemical scaffolds, and potentially lower toxicity profiles.Encouraged by this, over 150.000 compounds from a chemical library of natural-products and 324 compounds from our research group were screened in silico. 20 highest-scoring compounds of our research group were tested in microscale thermophoresis to assess their ability to bind with 11β-HSD1. Moreover, HPLC-MS/MS quantification was selected to evaluat the inhibition of 11β-HSDl in vitro. In which, compound 38 exhibited significant inhibition activities against 11β-HSD1 with a IC50 of 1.86μM and showed resonable binding affinity to protein (Kd=256±11μM). Furthermore, the molecular docking demonstrated that compound 38 coordinated in the active site of 11β-HSD1 is essential for the ability of diminishing the enzyme activity. This research is meaningful for the discovery of novel 11β-HSD1 inhibitors, provides the lead compound for structure improvements and also provide the fundamental research of 11β-HSD1 inhibition.