Naringin inhibits autophagy mediated by PI3K-Akt-mTOR pathway to ameliorate endothelial cell dysfunction induced by high glucose/high fat stress

As a flavonoid, naringin (Nar) has been shown to have multiple pharmacological effects including lowering blood cholesterol, reducing thrombus formation and improving microcirculation. However, effects of Nar on function and autophagy of vascular endothelial cells under high glucose and high fat (HG/HF) stress are largely unclear. This study was designed to investigate such effects of Nar in human umbilical vein endothelial cells (HUVECs) and to determine whether such effects are related to autophagy. Our present results show that 86 μM of Nar inhibits the autophagy levels and protects the cells against the dysfunction induced by HG/HF stress. Moreover, Nar increases the phosphorylation levels of phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt) and mammalian rapamycin target protein (mTOR). However, pretreatment with rapamycin (RAPA, 5 μM, autophagy inducer), LY294002(10 μM, PI3K inhibitor) and Akt inhibitor Ⅳ (0.5 μM, Akt inhibitor) partially abrogates the protective effects of Nar, suggesting that the protective effects of Nar are achieved by activating the PI3K-Akt-mTOR pathway to inhibit autophagy. In conclusion, Nar improves the function of HUVECs under HG/HF stress through activating the PI3K-Akt-mTOR pathway to inhibit autophagy. The findings offer an insight into HG/HF stress-induced autophagy and indicate that Nar might have potential to prevent and treat the diabetic angiopathy.