Large-leaf yellow tea attenuates high glucose-induced vascular endothelial cell injury by up-regulating autophagy and down-regulating oxidative stress.

Vascular endothelial cell injury induced by high glucose (HG) plays an important role in the occurrence and development of diabetic vascular complications. Yellow tea has a protective effect on vascular endothelial cells. However, the molecular mechanisms underlying this effect are unclear. In this study, the effects of the n-butanol fraction of Huoshan large-leaf yellow tea extract (HLYTBE) on vascular endothelial injury were investigated using human umbilical vein endothelial cells (HUVECs) and diabetic mice. In HUVECs, HLYTBE significantly reduced the production of reactive oxygen species, increased the activity of anti-oxidases (superoxide dismutase and glutathione peroxidase), enhanced the production of reduced glutathione, and decreased the level of oxidized glutathione, thereby improving cell viability. HLYTBE also promoted autophagosome formation, increased the LC3-II/LC3-I ratio, increased the expressions of Beclin1 and Atg 5, and decreased the expression of p62. HLYTBE up-regulated p-AMPK and down regulated p-mTOR, and these effects were reversed by compound C, an AMPK inhibitor. HLYTBE reduced apoptosis and cytochrome C expression, and these effects were attenuated by the autophagy inhibitor 3-methyladenine. In vivo studies showed that HLYTBE improved the impaired pyruvate tolerance, glucose tolerance, and insulin resistance; reduced the concentrations of blood glucose, glycated serum protein, lipids, and 8-isomeric prostaglandin 2α; increased the anti-oxidase activity in serum; and alleviated pathological damage in the thoracic aorta of diabetic mice induced by high sucrose-high fat diet along with streptozotocin. The results suggest that HLYTBE protects the vascular endothelium by up-regulating autophagy via the AMPK/mTOR pathway and inhibiting oxidative stress.

Scutellarin ameliorates high glucose-induced vascular endothelial cells injury by activating PINK1/Parkin-mediated mitophagy.

ETHNOPHARMACOLOGICAL RELEVANCE: Scutellarin (Scu) is one of the main active ingredients of Erigeron breviscapus (Vant.) Hand.-Mazz which has been used to treat cardiovascular disease including vascular dysfunction caused by diabetes. Scu also has a protective effect on vascular endothelial cells against hyperglycemia. However, molecular mechanisms underlying this effect are not clear. AIM OF THE STUDY: This aim of this study was to investigate the effect of Scu on human umbilical vein endothelial cells (HUVECs) injury induced by high glucose (HG), especially the regulation of PTEN-induced kinase 1 (PINK1)/Parkin-mediated mitophagy. MATERIALS AND METHODS: HUVECs were exposed to HG to induce vascular endothelial cells injury in vitro. Cell viability was assessed by MTT assay. The extent of cell apoptosis was measured by Hoechst staining and flow cytometry. Mitophagy was assayed by fluorescent immunostaining, transmission electron microscope and immunoblot. Besides, virtual docking was conducted to validate the interaction of PINK1 protein and Scu. RESULTS: We found that Scu significantly increased cell viability in HG-treated HUVECs. Scu reduces the expression of Bcl-2, Bax and cytochrome C (Cyt.c) to inhibit apoptosis through a mitochondria-dependent pathway. Meanwhile, Scu improved the overload of reactive oxygen species (ROS), superoxide dismutase (SOD) activity and SOD2 protein expression, and reversed the collapse of mitochondrial membrane potential. Besides, Scu increased autophagic flux, improved the expression of microtubule-associated protein 1 light chain 3 Ⅱ (LC3 II), Beclin 1 and autophagy-related gene 5 (Atg 5) and decreased the expression of Sequestosome1/P62 in HG-treated HUVECs. Furthermore, Scu improved the expressions of PINK1, Parkin, and Mitofusin2, which revealed the enhancement of mitophagy. Moreover, the beneficial effects of Scu on HG-induced low expression of Parkin, overproduction of ROS, and over expressions of P62, Cyt.c and Cleaved caspase-3 were weakened by PINK1 gene knockdown. Molecular docking suggested good interaction of Scu and PINK1 protein. CONCLUSION: These results suggest that Scu may protect vascular endothelial cells against hyperglycemia-induced injury by up-regulating mitophagy via PINK1/Parkin signal pathway.

Scutellarin, a modulator of mTOR, attenuates hepatic insulin resistance by regulating hepatocyte lipid metabolism via SREBP-1c suppression.

High levels of consumption of saturated lipids have been largely associated with the increasing prevalence of metabolic diseases. In particular, saturated fatty acids such as palmitic acid (PA) have been implicated in the development of insulin resistance (IR). Scutellarin (Scu) is one of the effective traditional Chinese medicines considered beneficial for liver diseases and diabetes. In this study, we investigated the effect of Scu on IR and lipid metabolism disorders in vitro and in high fat diet (HFD)-fed mice. In vitro, we found that Scu decreased insulin-dependent lipid accumulation and the mRNA expression of CD36, Fasn, and ACC in PA-treated HepG2 cells. Additionally, Scu upregulated Akt phosphorylation and improved the insulin signalling pathway. Moreover, Scu downregulated mammalian target of rapamycin (mTOR) phosphorylation and the n-SREBP-1c protein level and also reduced lipid accumulation via the mTOR-dependent pathway, as confirmed by the molecular docking of Scu to mTOR. In HFD-fed C57BL/6 mice, Scu improved oral glucose tolerance, pyruvate tolerance and the IR index and also increased the Akt phosphorylation level. Moreover, Scu reduced hepatocyte steatosis, decreased lipid accumulation and triglyceride levels, inhibited mTOR phosphorylation, and decreased the SREBP-1c level in the liver. Taken together, these findings suggest that Scu ameliorates hepatic IR by regulating hepatocyte lipid metabolism via the mTOR-dependent pathway through SREBP-1c suppression.