Simiao Wan alleviates obesity-associated insulin resistance via PKCε/IRS-1/PI3K/Akt signaling pathway based on network pharmacology analysis and experimental validation

Background:The purpose of the study was to investigatethe active ingredients and potential biochemicalmechanisms of Simiao Wan(SMW)in obesity-associated insulin resistance.Methods:An integrated network pharmacology method to screen the active compoundsand candidate targets,construct the protein-protein-interaction network,and ingredients-targets-pathways network was constructed for topological analysis to identify core targets and main ingredients.To find the possible signaling pathways,enrichment analysis was performed.Further,a model of insulin resistance in HL-7702 cells was established to verify the impact of SMW and the regulatory processes.Results:An overall of 63 active components and 151 candidate targets were obtained,in which flavonoids were the main ingredients.Enrichment analysis indicated that the PI3K-Akt signaling pathway was the potential pathway regulated by SMW in obesity-associated insulin resistance treatment.The result showed that SMW could significantly ameliorate insulin sensitivity,increase glucose synthesis and glucose utilization and reduce intracellular lipids accumulation in hepatocytes.Also,SMW inhibited diacylglycerols accumulation-induced PKCεactivity and decreased its translocation to the membrane.Conclusion:SMW ameliorated obesity-associated insulin resistance through PKCε/IRS-1/PI3K/Akt signaling axis in hepatocytes,providing a new strategy for metabolic disease treatment.

Bitter gourd extract improves glucose homeostasis and lipid profile via enhancing insulin signaling in the liver and skeletal muscles of diabetic rats

Objective:To investigate the modulatory effects of bitter gourd extract on the insulin signaling pathway in the liver and skeletal muscle tissues of diabetic rats.Methods:The ethanolic extract of bitter gourd was prepared and its contents of total polyphenols and flavonoids were assayed.A neonatal streptozotocin-induced diabetic rat model was established and the diabetic rats were assigned into different groups and were treated with different doses of bitter gourd extract(100,200,400,or 600 mg/kg)or with glibenclamide(0.1 mg/kg)for 30 d.Fasting blood glucose,insulin,and lipid profile were evaluated and the insulin signaling pathway in the liver and skeletal muscle of rats was investigated.The correlations between homeostasis model assessment(HOMA)and the components of insulin signaling pathway were also evaluated.Results:Different doses of bitter gourd extract significantly ameliorated fasting blood glucose level and HOMA index for insulin resistance.Moreover,bitter gourd extract increased serum insulin and improved disrupted serum lipid profile.The levels of insulin receptor substrate-1(IRS-1),p-insulin receptorβ(p-IR-β),protein kinase C(PKC),GLUT2,and GLUT4 were improved by treatment with bitter gourd extract.The best results were obtained with 400 mg/kg dose of the extract,the effect of which was equivalent to that of glibenclamide.HOMA in the bitter gourd treated rats was negatively correlated with p-IR-β,IRS-1 and PKC in hepatic and skeletal muscle.HOMA was also negatively correlated with skeletal muscle GLUT4.Conclusions:Bitter gourd extract improves glucose homeostasis and lipid profile in diabetic rats via enhancement of insulin secretion and sensitivity.Therefore,bitter gourd can be used as a potential pharmacological agent for the treatment of type 2 diabetes mellitus.

S-Allylmercaptocysteine improves alcoholic liver disease partly through a direct modulation of insulin receptor signaling

Alcoholic liver disease(ALD) causes insulin resistance, lipid metabolism dysfunction, and inflammation. We investigated the protective effects and direct regulating target of S-allylmercaptocysteine(SAMC) from aged garlic on liver cell injury. A chronic ethanol-fed ALD in vivo model(the NIAAA model) was used to test the protective functions of SAMC. It was observed that SAMC(300 mg/kg, by gavage method) effectively ameliorated ALD-induced body weight reduction, steatosis,insulin resistance, and inflammation without affecting the health status of the control mice, as demonstrated by histological, biochemical, and molecular biology assays. By using biophysical assays and molecular docking, we demonstrated that SAMC directly targeted insulin receptor(INSR) protein on the cell membrane and then restored downstream IRS-1/AKT/GSK3 b signaling. Liver-specific knock-down in mice and siRNA-mediated knock-down in AML-12 cells of Insr significantly impaired SAMC(250 mmol/L in cells)-mediated protection. Restoration of the IRS-1/AKT signaling partly recovered hepatic injury and further contributed to SAMC’s beneficial effects. Continuous administration of AKT agonist and recombinant IGF-1 in combination with SAMC showed hepato-protection in the mice model.Long-term(90-day) administration of SAMC had no obvious adverse effect on healthy mice. We conclude that SAMC is an effective and safe hepato-protective complimentary agent against ALD partly through the direct binding of INSR and partial regulation of the IRS-1/AKT/GSK3 b pathway.