Herbal Research Laboratory, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhawan, 31, M.G Marg, Lucknow, 226001, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, 201002, India; Department of Pharmacology and Nutritional Sciences, University of Kentucky, USA.
Herbal Research Laboratory, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhawan, 31, M.G Marg, Lucknow, 226001, India.
Eur J Pharmacol. 2022 Jul 5;926:175012. doi: 10.1016/j.ejphar.2022.175012. Epub 2022 May 11.
Hyperglycemia induced reactive oxygen species oxidize macromolecules including cellular proteins leading to their accumulation in Endoplasmic Reticulum (ER) lumen which in turn activates unfolded protein response (UPR) sensors including, PERK (Protein Kinase RNA-Like ER Kinase). Activated PERK induces ER associated degradation of misfolded proteins to lower the ER stress. In the present study, we hypothesized that ER stress leads to the degradation of glucose transporter proteins resulting in complex glucose metabolism. In vivo studies were carried out in the experimental model of hyperglycemia using streptozotocin/nicotinamide induced diabetic male Wistar rats. High glucose (30 mM) treated HepG2 cells were used to perform the mechanistic study at different time points. PERK gene knockdown (siRNA transfection) and inhibition by ISRIB (Integrated Stress Response Inhibitor, a potent inhibitor of PERK signaling) confirmed the involvement of PERK axis in regulating the expression and translocation of hepatic glucose transporters. Co-immunoprecipitation and dual immunostaining studies further demonstrated increased degradation of GLUT proteins under high glucose conditions. Moreover, Morin (3,5,7,2',4' pentahydroxyflavone) treatment prevented PERK-eIF2α-ATF4 mediated degradation of glucose transporters and enhanced glucose uptake in both, HepG2 cells and diabetic rats. Targeting aberrant regulation of the expression and translocation of facilitative glucose transporter proteins (GLUT proteins) may provide novel therapeutic strategies for the better management of diabetes.
高血糖诱导的活性氧氧化包括细胞蛋白在内的大分子，导致其在内质网（ER）腔中积累，进而激活未折叠蛋白反应（UPR）传感器，包括 PERK（蛋白激酶 RNA 样内质网激酶）。激活的 PERK 诱导内质网相关降解错误折叠的蛋白质，以降低内质网应激。在本研究中，我们假设内质网应激导致葡萄糖转运蛋白的降解，从而导致复杂的葡萄糖代谢。在使用链脲佐菌素/烟酰胺诱导的糖尿病雄性 Wistar 大鼠的高血糖实验模型中进行了体内研究。使用高葡萄糖（30mM）处理的 HepG2 细胞在不同时间点进行机制研究。PERK 基因敲低（siRNA 转染）和 ISRIB（综合应激反应抑制剂，PERK 信号的有效抑制剂）抑制证实了 PERK 轴在调节肝葡萄糖转运蛋白的表达和易位中的作用。共免疫沉淀和双重免疫染色研究进一步表明，在高葡萄糖条件下 GLUT 蛋白的降解增加。此外，杨梅素（3,5,7,2',4'-五羟基黄酮）处理可防止 PERK-eIF2α-ATF4 介导的葡萄糖转运蛋白的降解，并增强 HepG2 细胞和糖尿病大鼠的葡萄糖摄取。针对易位的葡萄糖转运蛋白（GLUT 蛋白）的表达和调节可能为更好地管理糖尿病提供新的治疗策略。
