Department of Nephrology, The Third Xiangya Hospital, Central South University, Changsha, Hunan, China.
Department of Nephrology, The Second Xiangya Hospital, Institute of Kidney Disease, Central South University, Changsha, Hunan, China.
Cell Death Dis. 2021 Oct 9;12(10):925. doi: 10.1038/s41419-021-04184-8.
Renal tubulointerstitial fibrosis was a crucial pathological feature of diabetic nephropathy (DN), and renal tubular injury might associate with abnormal mitophagy. In this study, we investigated the effects and molecular mechanisms of AMPK agonist metformin on mitophagy and cellular injury in renal tubular cell under diabetic condition. The high fat diet (HFD) and streptozotocin (STZ)-induced type 2 diabetic mice model and HK-2 cells were used in this study. Metformin was administered in the drinking water (200 mg/kg/d) for 24 weeks. Renal tubulointerstitial lesions, oxidative stress and some indicators of mitophagy (e.g., LC3II, Pink1, and Parkin) were examined both in renal tissue and HK-2 cells. Additionally, compound C (an AMPK inhibitor) and Pink1 siRNA were applied to explore the molecular regulation mechanism of metformin on mitophagy. We found that the expression of p-AMPK, Pink1, Parkin, LC3II, and Atg5 in renal tissue of diabetic mice was decreased obviously. Metformin reduced the levels of serum creatinine, urine protein, and attenuated renal oxidative injury and fibrosis in HFD/STZ induced diabetic mice. In addition, Metformin reversed mitophagy dysfunction and the over-expression of NLRP3. In vitro pretreatment of HK-2 cells with AMPK inhibitor compound C or Pink1 siRNA negated the beneficial effects of metformin. Furthermore, we noted that metformin activated p-AMPK and promoted the translocation of Pink1 from the cytoplasm to mitochondria, then promoted the occurrence of mitophagy in HK-2 cells under HG/HFA ambience. Our results suggested for the first time that AMPK agonist metformin ameliorated renal oxidative stress and tubulointerstitial fibrosis in HFD/STZ-induced diabetic mice via activating mitophagy through a p-AMPK-Pink1-Parkin pathway.
肾间质纤维化是糖尿病肾病（DN）的一个关键病理特征，肾小管损伤可能与异常的线粒体自噬有关。在这项研究中，我们研究了 AMPK 激动剂二甲双胍在糖尿病状态下对肾小管细胞中线粒体自噬和细胞损伤的影响及其分子机制。该研究使用了高脂肪饮食（HFD）和链脲佐菌素（STZ）诱导的 2 型糖尿病小鼠模型和 HK-2 细胞。二甲双胍通过饮用水给药（200mg/kg/d），持续 24 周。在肾组织和 HK-2 细胞中检测了肾间质病变、氧化应激和一些线粒体自噬指标（如 LC3II、Pink1 和 Parkin）。此外，还应用了化合物 C（一种 AMPK 抑制剂）和 Pink1 siRNA 来探讨二甲双胍对线粒体自噬的分子调控机制。我们发现，糖尿病小鼠肾组织中 p-AMPK、Pink1、Parkin、LC3II 和 Atg5 的表达明显降低。二甲双胍降低了血清肌酐、尿蛋白水平，并减轻了 HFD/STZ 诱导的糖尿病小鼠的肾氧化损伤和纤维化。此外，二甲双胍逆转了线粒体自噬功能障碍和 NLRP3 的过度表达。HK-2 细胞预先用 AMPK 抑制剂化合物 C 或 Pink1 siRNA 处理，否定了二甲双胍的有益作用。此外，我们注意到，二甲双胍在高糖/高游离脂肪酸环境下激活 p-AMPK，促进 Pink1 从细胞质易位到线粒体，从而促进 HK-2 细胞中线粒体自噬的发生。我们的研究结果首次表明，AMPK 激动剂二甲双胍通过激活 Pink1-Parkin 通路促进线粒体自噬，从而改善 HFD/STZ 诱导的糖尿病小鼠的肾氧化应激和肾小管间质纤维化。
