Department of Nephrology, Binhaiwan Central Hospital of Dongguan, Dongguan, China.
Department of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China,
Kidney Blood Press Res. 2023;48(1):314-325. doi: 10.1159/000530403. Epub 2023 Apr 13.
Restoration of podocyte autophagy is considered as a feasible strategy for the treatment of diabetic kidney disease (DKD). This study aimed at investigating the protective effect and potential mechanism of vitamin D on podocyte injury of DKD.
Type 2 diabetic db/db mice received intraperitoneal injections of vitamin D analog paricalcitol 400 ng/kg per day for 16 weeks. Immortalized mouse podocytes were cultured in high glucose (HG) medium with active vitamin D3 calcitriol or autophagy inhibitor 3-methyladenine. Renal function and urine albumin creatinine ratio were assessed at week 24. HE, PAS staining, and electron microscopy were used to evaluate renal histopathology and morphological changes. Immunohistochemistry, immunofluorescence, and Western blot were used to evaluate protein expression of nephrin and podocin in kidney tissue and podocytes. The expression of autophagy-related proteins (LC3, Beclin-1, Vps34) and apoptosis-related proteins (cleaved caspase-3, Bax) was determined by Western blotting. Podocyte apoptosis was further evaluated by using flow cytometer.
Albuminuria in a db/db mouse model was markedly attenuated after treatment with paricalcitol. This was accompanied by alleviation of mesangial matrix expansion and podocyte injury. Besides, the impaired autophagy in podocytes under diabetic conditions was also markedly enhanced after paricalcitol or calcitriol treatment, accompanied by restored decreased podocyte slit diaphragm proteins podocin and nephrin. Furthermore, the protective effect of calcitriol against HG-induced podocyte apoptosis could be abated by autophagy inhibitor 3-methyladenine.
Vitamin D ameliorates podocyte injury of DKD by enhancing podocyte autophagy activity, which may become a potential candidate autophagy activator for the therapeutic interventions for DKD.
恢复足细胞自噬被认为是治疗糖尿病肾病（DKD）的一种可行策略。本研究旨在探讨维生素 D 对 DKD 足细胞损伤的保护作用及潜在机制。
2 型糖尿病 db/db 小鼠接受维生素 D 类似物帕立骨化醇 400ng/kg/天腹腔注射 16 周。高糖（HG）培养基中培养永生化的小鼠足细胞，并用活性维生素 D3 骨化三醇或自噬抑制剂 3-甲基腺嘌呤处理。第 24 周评估肾功能和尿白蛋白/肌酐比值。HE、PAS 染色和电子显微镜用于评估肾脏组织学和形态变化。免疫组化、免疫荧光和 Western blot 用于评估肾脏组织和足细胞中nephrin 和 podocin 蛋白的表达。Western blot 用于检测自噬相关蛋白（LC3、Beclin-1、Vps34）和凋亡相关蛋白（cleaved caspase-3、Bax）的表达。采用流式细胞术进一步评估足细胞凋亡。
帕立骨化醇治疗可明显减轻 db/db 小鼠模型的蛋白尿。这伴随着系膜基质扩张和足细胞损伤的缓解。此外，在糖尿病条件下，足细胞中的自噬受损也明显增强，同时恢复了降低的足细胞裂孔隔膜蛋白 podocin 和 nephrin。此外，自噬抑制剂 3-甲基腺嘌呤可减弱骨化三醇对 HG 诱导的足细胞凋亡的保护作用。
维生素 D 通过增强足细胞自噬活性改善 DKD 中的足细胞损伤，这可能成为 DKD 治疗干预的潜在候选自噬激活剂。
