Discovery Of Active Small Molecules Against Metabolic Diseases And Related Mechanism Research

Due to diet and lifestyle changes, more and more people are suffering from metabolic disorders. Currently, the anti-diabetes targets contain modulators of carbohydrate and lipid metabolism, insulin sensitivity and inflammation. Nuclear receptors as the modulators of carbohydrate and lipid metabolism are always hot issues in anti-diabetes research, such as retinoic acid X receptor, peroxisome proliferator-activated receptor gamma, liver X receptor, farnesoid X receptor and glucocorticoid receptor. However, anti-diabetic drugs based on the known targets can not meet the needs owing to various deficiencies, it is thus urgently needed to develop more effective drugs.In addition to current anti-diabetic molecular target, growing evidences demonstrated that mineralocorticoid receptor (MR) involved in insulin resistance via pro-inflammatory process. In previous work, we have found a potent MR antagonist DOM (des-O-methyllasiodiplodin), extracted from Cerbera manghas, played a role in reversing Aldosterone’s effect. Our current study further revealed DOM’s effects on glucose homeostasis and insulin sensitivity. We found the natural product DOM played a role in regulating blood glucose level in db/db mice. In addition, DOM could ameliorate insulin resistance in vivo. Since MR has not yet been found a direct regulation on glucose and lipid metabolism related genes, we supposed that DOM, like other MR antagonists, achieved its anti-diabetic effect though attenuating chronic inflammation. In fact, there was reduced expression of pro-inflammatory factors (monocyte chemotactic protein-1, tumor necrosis factor a and Interleukin-6) in DOM-administrated mice adipose and liver tissues, similar to the results in cultured cell lines. This process was mediated by ROS (Reactive oxygen species)-related signaling. DOM exhibited its anti-inflammatory effect via modulating MR, which has been identified by MR si-RNA interference assay. As reported, MR blockade decreased glucose and lipid metabolism related genes expression in high-fat and high-fructose diet mice. We detected the corresponding gene expression in db/db mice, and found decreased PEPCK (phosphoenolpyruvate carboxykinase), G6Pase (glucose6-phosphate dehydrogenase) and PGCla (PPARgamma coactivator1-a) mRNA levels in liver. This suggests that DOM may involve in the regulation of glucose and lipid metabolism. Based on DOM’s chemical structure, we designed and synthesized several DOM derivatives, and found some compounds with more potent activity and selectivity than DOM. Our work provided evidence for the effect of DOM on metabolic disorder regulation, as the MR antagonist. As a novel marine natural product, DOM provided new clues in anti-diabetic lead compounds discovery.In the second section, we investigated the β-cell protection and proliferation effect of PR (progesterone receptor) antagonist. Firstly, we found a novel non-steroid ligand AA29, with potent antagonism against PR and good selectivity against other nuclear receptors. AA29improved the P-cell survive and ameliorated the cell morphology under damage stimulus, decresed the apoptosis ratio. However, AA29does not obviously promote normal β-cell proliferation. Considering the antagonism of AA29against progesterone in Min-6cells with or without pro-inflammatory factors stimulation, we discovered the anti-apoptosis mechanism of AA29mainly via inhibiting p-Erkl/2/p53pathway, protecting p-NF-κB, TRAF2and p-AKT proteins. In addition, AA29slightly increased the insulin secretion induced by glucose. All of these suggested a possibility that AA29protected β-cell from injury and dysfunction, as well as insulin secretion improvement without risk of hyperinsulinemia. Our work provided new evidence of PR blockade in treatment of metabolic disease.Furthermore, RXRα modulators were still of great interest in anti-diabetes research. Our group has previously found a novel RXRα antagonist named Danthron. In this work we further inverstigated its effects and mechanisms of insulin sensitivity. Danthron could effciantly improve insulin tolerance in high-fat diet induced obese (DIO) mice. In addition, Danthron increased the IRS1gene transcription and protein levels, enhanced the phosphorylation of IRS1and IR in HepG2and C2C12cells. At the same time, with Danthron treatment, Glut4protein level was increased in both cells, and Glut4translocation was promoted in CHO-K1-Glut4stable cell line. Our work has evaluated the improvement of Danthron upon insulin sensitivity in vitro and in vivo.Meanwhile, we studied the effect of the active molecule on metabolic disease by regulating ER Stress (endoplasmic reticulum stress). We found a natural product YY3regulated blood glucose level via attenuating ER Stress response in diabetic mice. Improved insulin sensitivity and decreased lipid levels were detected after YY3treatment in vivo. The detailed mechanism needs to be revealed in the future, and further understanding will be established in ER Stress signaling pathway regulating diabetes.Overall, we found several active small molecules including nuclear receptors ligands and ER Stress modulator, investigated their anti-diabetic functions and related mechanism. These results provided new clues in anti-diabetes drug discovery.