研究目的：糖尿病肾病（diabetic kidney disease，DKD）是糖尿病最具破坏性的微血管并发症，其发病机制复杂，涉及多重因素的协同作用。目前的治疗方案虽能降低蛋白尿和延缓肾功能下降，但仍无法完全阻止其向终末期肾病进展。血管生成素样蛋白4（angiopoietin-like protein 4，ANGPTL4）与DKD纤维化之间存在关联；然而，这种关联尚未得到充分研究。本研究旨在明确肾脏局部ANGPTL4表达模式和DKD的临床相关性及潜在的病理生理机制，挖掘白藜芦醇在抑制ANGPTL4表达并保护DKD肾脏免受纤维化损害的潜力。特别针对足细胞损伤这一核心病理环节，深入阐明白藜芦醇通过逆转ANGPTL4介导的自噬障碍，抑制足细胞上皮-间充质转化（epithelial-mesenchymal transition，EMT），恢复足细胞功能的分子机制。本研究旨在为DKD的临床评估、治疗及药物研发提供理论依据和新的思路。

研究内容：研究采用三阶段设计：1.通过Meta分析系统评价白藜芦醇在DKD动物模型中的疗效。2.分析DKD患者肾脏ANGPTL4表达特征及其临床预后关联。3.建立体外足细胞损伤模型阐明白藜芦醇抑制ANGPTL4表达，改善自噬受阻，恢复足细胞功能的分子机制。

研究方法：1.在荟萃分析部分，按照《系统评价和荟萃分析报告的优选项目》标准，对2010年1月至2024年12月间发布的相关啮齿类动物研究进行系统评价和荟萃分析。2.在临床研究部分，回顾性纳入30例2006年1月至2023年12月中日友好医院经临床病理诊断为DKD并随访满1年的患者及5例瘤旁肾组织作为正常对照，采用免疫荧光染色及免疫组化技术检测ANGPTL4在肾组织中的表达特征，分析其与蛋白尿程度及肾功能进展的关联。进一步通过ROC曲线分析确定ANGPTL4高表达临界值，评估其与转分化标志物（α-SMA、Collagen I、Collagen III、Fibronectin）的相关性。3.在机制研究部分，通过基因集富集分析（gene set enrichment analysis，GSEA）分析DKD患者肾小球组织转录组数据，探究ANGPTL4在DKD自噬调控中的作用。利用晚期糖基化终末产物（advanced glycation end-products，AGEs）刺激肾小球足细胞系，体外构建足细胞损伤模型。并通过Western Blot、免疫荧光染色及转盘共聚焦显微镜观察等技术，明确白藜芦醇调控损伤足细胞ANGPTL4表达、恢复自噬功能、抑制EMT的分子网络机制。

研究结果：1.荟萃分析纳入42项研究，涉及793只动物。结果表明白藜芦醇的摄入可以显著减少系膜指数、肾小球基底膜厚度、肾小球肥大、肾小球硬化指数、血清肌酐、尿素氮、24 h UTP、血糖、肾脏指数、总胆固醇、甘油三酯和低密度脂蛋白胆固醇水平，但未能显著增加白蛋白和高密度脂蛋白胆固醇水平，未能显著降低肌酐清除率和糖化血红蛋白水平。剂量-反应分析显示，在低剂量（2-15 mg/kg/day）或高剂量（100-200 mg/kg/day）时，白藜芦醇对改善肾功能和减轻蛋白尿最为有效，中等剂量效果变异较大。

2.DKD患者肾小球及肾小管间质ANGPTL4表达均强于正常对照。亚组分析表明大量蛋白尿患者肾小球和肾小管间质的ANGPTL4表达显著高于未达到大量蛋白尿组。相关性分析显示，肾小球和肾小管间质的ANGPTL4表达水平与24 h UTP呈正相关，且肾小管间质的ANGPTL4表达与1年估算的肾小球滤过率（estimated glomerular filtration rate，eGFR）下降率显著相关。ANGPTL4高表达组足细胞转分化标志物显著上调，Collagen I及α-SMA表达分别较对照组升高3.5倍和2倍。

3.GSEA显示ANGPTL4在DKD自噬障碍中具有重要作用。体外AGEs诱导足细胞损伤模型中，足细胞表现出ANGPTL4表达上调、自噬功能障碍和EMT。而白藜芦醇可呈浓度依赖性抑制ANGPTL4、改善自噬功能障碍，减轻转分化表型，其中10 μM白藜芦醇效果最佳。足细胞ANGPTL4过表达模型提示ANGPTL4可能通过下调自噬相关蛋白ATG5和Beclin 1的基因表达以及促进GSK-3β磷酸化抑制自噬通量并促进EMT。

研究结论：1.白藜芦醇在DKD动物模型中表现出显著的肾脏保护作用并在低剂量效果显著且异质性较小。白藜芦醇能够显著改善肾功能指标，降低DKD的生化损伤标志物，机制可能涉及抗炎、抗氧化、代谢调节和促进自噬等多条途径。

2.ANGPTL4在DKD患者肾脏中特异性高表达，其表达水平与蛋白尿严重程度及肾功能恶化显著相关，且可能通过介导纤维化参与疾病进展。肾小管间质ANGPTL4表达对eGFR下降的预测价值尤为突出，提示其作为预后评估生物标志物的潜力。

3.体外实验结果显示，ANGPTL4抑制自噬过程参与足细胞损伤的发生发展。白藜芦醇处理可下调ANGPTL4表达，并改善足细胞自噬功能、减轻EMT指标。这些结果为探讨DKD足细胞损伤的分子机制提供了新的实验线索，提示ANGPTL4上调促进足细胞损伤。

Objective: Diabetic kidney disease (DKD) is the most devastating microvascular complication of diabetes, with a complex pathogenesis involving synergistic effects of multiple factors. Although current treatments can reduce proteinuria and delay renal function decline, they cannot completely prevent progression to end-stage renal disease. Angiopoietin-like protein 4 (ANGPTL4) has been implicated in DKD-related fibrosis, but this association remains understudied. This study aimed to elucidate the renal expression pattern of ANGPTL4, its clinical relevance in DKD, and its pathophysiological mechanisms, while exploring the potential of resveratrol to inhibit ANGPTL4 expression and protect against renal fibrosis in DKD. Focusing on podocyte injury—a central pathological feature—we further investigated the molecular mechanism by which resveratrol reverses ANGPTL4-mediated autophagy impairment, suppresses podocyte epithelial-mesenchymal transition (EMT), and restores podocyte function. This study provides theoretical foundations and novel insights for the clinical assessment, treatment, and drug development of DKD.

Methods: The study employs a three-phase design. 1. Systematic evaluation of resveratrol's efficacy in DKD animal models following PRISMA guidelines, incorporating rodent studies published between January 2010 and December 2024. 2. Clinical investigation: Retrospective analysis of 30 DKD patients (diagnosed via clinicopathology at China-Japan Friendship Hospital, January 2006–December 2023) with ≥1-year follow-up, alongside 5 normal controls (adjacent non-tumor renal tissues). ANGPTL4 expression in renal tissues was assessed using immunofluorescence and immunohistochemistry, with correlations analyzed between ANGPTL4 levels, proteinuria severity, renal function decline (eGFR slope), and pathological grading. ROC curve analysis defined high ANGPTL4 expression thresholds, and associations with fibrosis markers (Collagen I, III, α-SMA, Fibronectin) were evaluated. 3. Gene Set Enrichment Analysis (GSEA) of glomerular transcriptomic data from DKD patients to identify ANGPTL4-linked pathways (autophagy, lipid metabolism). In vitro studies using immortalized human podocytes assessed advanced glycation end-products (AGEs)-induced autophagy dysfunction, ANGPTL4 upregulation, and epithelial-mesenchymal transition (EMT). Resveratrol's effects were evaluated via western blot and immunofluorescence.

Results: 1. Meta-analysis incorporating 42 studies involving 793 animals demonstrated that resveratrol supplementation significantly reduced mesangial index, glomerular basement membrane thickness, glomerular hypertrophy, glomerulosclerosis index, serum creatinine, blood urea nitrogen (BUN), 24-hour urinary total protein (24 h UTP), blood glucose, kidney index, total cholesterol (TC), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C) levels. However, it did not significantly increase albumin or high-density lipoprotein cholesterol (HDL-C) levels, nor did it significantly reduce creatinine clearance rate or glycated hemoglobin (HbA1c) levels. Dose-response analysis revealed optimal efficacy at low (≤ 15 mg/kg/day) and high doses (100–200 mg/kg/day), mediated by anti-inflammatory, antioxidant, metabolic regulatory, and pro-autophagy mechanisms. 2. ANGPTL4 expression in DKD patients was elevated in both glomeruli and tubulointerstitial regions compared to controls. Subgroup analysis showed significantly higher ANGPTL4 levels in nephrotic-range proteinuria patients. Glomerular and tubulointerstitial ANGPTL4 correlated positively with 24-hour urinary protein (r = 0.478 and r = 0.414, respectively), while tubulointerstitial ANGPTL4 predicted 1-year eGFR decline (r = 0.593, P = 0.003). High ANGPTL4 expression groups exhibited marked upregulation of fibrosis markers (Collagen I: 3.5-fold, α-SMA: 2-fold vs. controls). 3. GSEA linked ANGPTL4 to autophagy suppression and lipid oxidation activation in DKD. In vitro, AGEs induced podocyte autophagy impairment, ANGPTL4 upregulation, and fibrosis, while resveratrol (10 μM) concentration-dependently restored autophagy and attenuated fibrotic phenotypes. ANGPTL4 overexpression exacerbated EMT via GSK-3β signaling, effects reversed by resveratrol.

Conclusions: 1. Resveratrol demonstrated significant renoprotective effects in DKD animal models, with pronounced efficacy at low and high doses but attenuated effects at intermediate doses. It effectively improved renal function parameters and reduced biochemical injury markers in DKD, potentially through anti-inflammatory, antioxidant, metabolic regulatory, and pro-autophagy pathways.

2. ANGPTL4 was specifically overexpressed in the kidneys of DKD patients, and its expression levels correlated strongly with proteinuria severity and renal function deterioration. ANGPTL4 likely contributes to disease progression by mediating fibrosis. Notably, tubulointerstitial ANGPTL4 expression showed prominent predictive value for eGFR decline, suggesting its potential as a prognostic biomarker.

3. In vitro experiments revealed that ANGPTL4 participates in podocyte injury by suppressing autophagy. Resveratrol treatment downregulated ANGPTL4 expression, restored podocyte autophagy function, and mitigated fibrotic indicators. These findings provide novel experimental insights into the molecular mechanisms of podocyte injury in DKD and identify ANGPTL4 as a pivotal mediator of podocyte damage.