Song Zhixia, Xiao Chao, Jia Xiaoli, Luo Chunhua, Shi Lang, Xia Rong, Zhu Jiefu, Zhang Shizhong
Department of Nephrology, The First Clinical Medical College of Three Gorges University, Center People's Hospital of Yichang, Yichang, 443000, People's Republic of China.
Three Gorges University College of Medical Science, Yichang, 443000, People's Republic of China.
Diabetes Metab Syndr Obes. 2021 Apr 16;14:1681-1693. doi: 10.2147/DMSO.S303018. eCollection 2021.
The present study is to investigate the effect of vitamin D/Vitamin D Receptor (VDR) signaling on podocyte autophagy in diabetic nephropathy.
Kidney tissue sections from patients with diabetic nephropathy and nontumor kidney were checked under electronic microscope and VDR immunohistochemistry. Diabetic rat models were induced by intraperitoneal injection of streptozotocin (STZ) (60 mg/kg). Calcitriol treatment was achieved by gavage at dose of 0.1μg/kg/d. Blood, urine and kidney tissue specimens were used for serum, urine biochemistry, histopathology and molecular biology testing. Podocyte cell line MPC-5 was cultured under hyperglycaemic conditions in the absence or presence of 100 nmol/L calcitriol to investigate podocyte injury and autophagy.
VDR and autophagosomes in podocytes were significantly decreased in renal biopsy from patients with diabetic nephropathy, compared to healthy kidney tissue. Rats with STZ treatment developed typical diabetic kidney disease with low VDR expression. Calcitriol, the active form of vitamin D, could activate VDR and attenuate diabetic nephropathy including proteinuria and glomerular sclerosis. Calcitriol treatment also alleviated the podocyte foot process fusion, reduced podocyte injury marker desmin and preserved slit diaphragms proteins in diabetic nephropathy. Reduced LC3II/I, Beclin-1 and elevated p62 in renal homogenate and reduced autophagosomes and LC3II in podocytes indicated podocytes autophagy impairment in diabetic nephropathy. Whereas calcitriol treatment restored podocyte autophagy activities. In cultured podocytes, the protective effect of calcitriol against high glucose induced podocyte injury could be abated by autophagy inhibitor chloroquine.
Our study delivered the evidence that calcitriol/VDR signaling attenuated diabetic nephropathy and podocytes injury by restoring podocytes autophagy. This finding may have potential implication for exploring protective mechanisms of calcitriol/VDR in diabetic nephropathy.
本研究旨在探讨维生素D/维生素D受体（VDR）信号通路对糖尿病肾病足细胞自噬的影响。
对糖尿病肾病患者和非肿瘤性肾脏患者的肾组织切片进行电子显微镜检查和VDR免疫组织化学检测。通过腹腔注射链脲佐菌素（STZ）（60mg/kg）诱导糖尿病大鼠模型。以0.1μg/kg/d的剂量灌胃给予骨化三醇进行治疗。采集血液、尿液和肾脏组织标本进行血清、尿液生化、组织病理学和分子生物学检测。在有无100nmol/L骨化三醇的情况下，在高糖条件下培养足细胞系MPC-5，以研究足细胞损伤和自噬。
与健康肾脏组织相比，糖尿病肾病患者肾活检中足细胞的VDR和自噬体显著减少。接受STZ治疗的大鼠出现典型的糖尿病肾病，VDR表达降低。维生素D的活性形式骨化三醇可激活VDR并减轻糖尿病肾病，包括蛋白尿和肾小球硬化。骨化三醇治疗还可减轻糖尿病肾病中足细胞足突融合，减少足细胞损伤标志物结蛋白，并保留裂孔隔膜蛋白。肾匀浆中LC3II/I、Beclin-1降低，p62升高，足细胞中自噬体和LC3II减少，表明糖尿病肾病中足细胞自噬受损。而骨化三醇治疗可恢复足细胞自噬活性。在培养的足细胞中，自噬抑制剂氯喹可减弱骨化三醇对高糖诱导的足细胞损伤的保护作用。
我们的研究提供了证据，表明骨化三醇/VDR信号通路通过恢复足细胞自噬减轻糖尿病肾病和足细胞损伤。这一发现可能对探索骨化三醇/VDR在糖尿病肾病中的保护机制具有潜在意义。
