背景

在过去几十年中，全球糖尿病肾病（diabetic kidney disease，DKD）的患病率急剧增加，这在很大程度上归因于2型糖尿病（type 2 diabetes mellitus，T2DM）患病率的日益增长。除高血糖外，肥胖、高血压、动脉粥样硬化、血脂异常和胰岛素抵抗等合并症也会导致肾脏损伤，使DKD成为一种异质性疾病。在过去的30年里，肾素-血管紧张素系统（renin-angiotensin system，RAS）抑制剂始终是DKD降蛋白尿治疗的基石。然而，接受RAS抑制剂治疗的患者进展到终末期肾脏病（end-stage renal disease，ESRD）的残余风险仍然很高。根据临床及病理特征早期准确识别高风险患者从而进行早期干预是有效遏制DKD进展的基础。近年来，据文献报道前列腺素E1（prostaglandin E1，PGE1）可以降低蛋白尿并改善肾功能，但其临床证据质量等级较低且作用机制有待深入阐明。

目的

（1）探究影响DKD肾损伤相关的临床及病理因素；

（2） 对目前PGE1治疗DKD的临床试验进行系统评价和荟萃分析，评估PGE1在DKD患者中的临床益处；

（3）明确PGE1对DKD患者肾脏复合结局的干预效果，为优化DKD临床管理策略提供新的循证依据；

（4）从临床肾活检组织、动物模型和细胞实验三个层面系统、深入地阐释PGE1延缓DKD进展的作用机制。

方法

（1）研究对象为中日友好医院肾病科2010年11月至2023年5月收治的经肾活检病理诊断为DKD的患者。收集DKD患者的临床数据和实验室检查结果，将患者分为进展组和稳定组，分析影响DKD进展的临床及病理相关因素，并根据Cox回归结果建立DKD疾病进展的风险预测模型。同时使用免疫组织化学染色方法检测DKD肾活检组织中E型前列腺素受体各亚型蛋白的情况，并分析其与临床指标的相关性。

（2）检索2000年1月1日至2024年12月31日MEDLINE、Cochrane图书馆、Embase和中国生物医学数据库的文献，纳入符合要求且无语言限制的PGE1治疗DKD的随机对照试验（randomized controlled trial，RCT）。干预组包含PGE1单药应用或者与其他药物联合应用的患者，对照组包含仅日常治疗、安慰剂或其他药物治疗的患者。该分析的主要结局为肾脏结局，包括DKD患者ESRD发生率、尿白蛋白排泄率（urinary albumin excretion rates，UAER）、白蛋白尿、蛋白尿、肾功能的变化。

（3）试验于2020年12月至2023年12月进行。按照纳入排除标准对在中日友好医院住院的2型DKD患者进行筛选。DKD患者在糖尿病标准治疗的基础上接受前列地尔静脉输注或仅接受标准治疗。在时间-事件分析中评估的主要结局是由估算肾小球滤过率（estimated glomerular filtration rate，eGFR）较基线持续下降至少40%或进展为ESRD组成的复合终点事件。ESRD被定义为eGFR ＜15 ml/min/1.73m²、需要维持透析或肾移植。

（4）收集DKD患者肾活检组织与肾肿瘤切除术后远端正常肾组织，采用免疫组织化学染色方法检测肾小球中足细胞标志物、EP1-4、SNCA及细胞凋亡标志物的表达；构建DKD小鼠模型，干预组给予尾静脉注射PGE1，对照组给予等量的生理盐水注射，连续给药8周后取材；建立高糖培养的人肾小球足细胞模型，加入适宜浓度的PGE1及EP1-4受体选择性拮抗剂等药物进行干预。使用生物信息学及WB、qRT-PCR等各种分子生物学技术初步探讨PGE1延缓DKD进展的潜在机制。

结果

（1）共有142例DKD患者符合条件纳入最终分析。单因素分析显示，eGFR、24小时尿蛋白定量、K-W结节、节段硬化、新月体样改变、毛细血管瘤样扩张和C1q沉积等临床病理因素与DKD进展相关。在完全调整的多因素Cox比例风险回归模型中，调整临床协变量和病理参数后，eGFR（HR，0.83；95% CI，0.74-0.94；P = 0.004）、24小时尿蛋白定量（HR，1.07；95% CI，1.02-1.12；P = 0.007）、新月体样改变（HR，1.72；95% CI，1.07-2.76；P = 0.024）和毛细血管瘤样扩张（HR，2.02；95% CI，1.28-3.20；P = 0.003）是仍然与DKD进展保持显著相关的临床病理因素。Spearman相关分析结果显示，肾小球EP2受体的表达与基线eGFR水平呈正相关（r = 0.315，P ＜0.001），与基线24小时尿蛋白定量水平呈负相关（r = -0.489，P ＜0.001）。基于Cox回归分析建立的预测模型C-index为0.73（95% CI，0.68-0.79）。

（2）最终纳入24项符合条件的、包含1735名受试者的RCT试验。所有试验均在中国进行。与仅日常治疗组的患者相比，接受PGE1治疗的患者UAER显著降低（MD -1.31 μg/min；95% CI，-1.98至-0.65；P ＜0.001）。同样，与单独应用其他药物（ACEI/ARB、血栓通）治疗的患者相比，接受PGE1联合其他药物治疗的患者UAER也显著降低（MD -1.06 μg/min；95% CI，-1.59至-0.52；P ＜0.001）。同时，与仅日常治疗组相比，PGE1治疗对其他肾脏结局也有显著改善（白蛋白尿：MD -2.81 mg/24h；95% CI -5.29至-0.33；P ＜0.001；血清肌酐：MD -0.49 μmol/L；95% CI -0.77至0.21；P ＜0.001）。而与单独应用其他药物相比，PGE1联合其他药物仅对蛋白尿具有积极影响（MD -1.78 g/24h；95% CI -2.86至-0.70；P = 0.001）。

（3）共有218例DKD患者符合条件并纳入最终分析。在试验结束时，经过中位12.3个月的随访，218例患者中有46例（21.1%）发生了主要复合结局事件。与对照组相比，PGE1治疗显著延缓了肾功能指标eGFR的下降（P = 0.002）。两组患者的24小时尿蛋白尿蛋白定量均降低，但PGE1干预组的下降幅度显著大于对照组（P ＜0.001）。此外，PGE1干预组和对照组在治疗期间不良事件的发生率没有显著的统计学差异（P = 0.113）。

（4）DKD患者肾活检组织肾小球局部SNCA的表达明显增多。对转录组学数据进行的基因差异分析表明，DKD小鼠肾组织中使用PGE1干预后SNCA发生显著差异表达。进一步实验证实DKD小鼠肾组织中SNCA表达增多，PGE1干预可以改善DKD小鼠肾损伤并显著降低SNCA的表达。体外实验证实PGE1可以减轻糖尿病环境下足细胞中SNCA的异常积累及足细胞凋亡，这种作用可以被EP2受体选择性拮抗剂特异性阻断。EP2受体是人肾小球足细胞中表达的最主要的E型前列腺素受体，PGE1和EP2受体结合促进cAMP的产生，而cAMP信号传导负调控SNCA的表达。

结论

（1）在T2DM患者中，蛋白尿、eGFR、肾小球新月体样改变及毛细血管瘤样扩张等临床病理特征与DKD肾损伤进展具有显著的相关性，肾小球新月体样改变及毛细血管瘤样扩张的存在可以加快DKD患者的疾病进展。EP2受体主要在肾小球足细胞中表达，且其表达水平降低与DKD患者的肾损伤相关。

（2）PGE1治疗可显著改善UAER、白蛋白尿、蛋白尿等多项肾脏预后指标。但PGE1对DKD患者血清肌酐水平的效应尚未形成明确结论，其疗效异质性可能与药物剂量和疗程存在显著差异导致的药物暴露量波动相关。

（3）PGE1具有显著的肾脏保护效应，可降低患者蛋白尿水平，减缓eGFR的下降，有效降低DKD的进展风险；PGE1治疗相关不良事件发生率与对照组无明显统计学差异，安全性较高，具有良好的临床应用潜力。

（4）PGE1结合EP2受体激活AC促进cAMP的产生，cAMP水平升高有助于抑制肾小球足细胞内SNCA异常积累导致的细胞凋亡。

Background

Over the past few decades, the global prevalence of diabetic kidney disease (DKD) has increased dramatically. This is largely attributed to the rising prevalence of type 2 diabetes mellitus (T2DM) driven by sedentary lifestyles and obesity. In addition to hyperglycemia, comorbidities such as obesity, hypertension, atherosclerosis, dyslipidemia, and insulin resistance contribute to kidney injury, making DKD a heterogeneous disease. For the past 30 years, renin-angiotensin system (RAS) inhibitors have served as the cornerstone of antiproteinuric therapy for DKD. However, the residual risk of DKD progression to end-stage renal disease (ESRD) remains considerable. Early and accurate identification of high-risk patients based on clinical and pathological characteristics, followed by prompt intervention, serves as the cornerstone for effectively delaying the progression of DKD. In recent years, studies have reported that prostaglandin E1 (PGE1) may reduce proteinuria and improve renal function, but the quality of clinical evidence is poor, and its underlying mechanisms remain incompletely understood.

Objectives

(1) To investigate the clinical and pathological factors associated with DKD progression. (2) To evaluate the clinical benefits of PGE1 in DKD patients by conducting a systematic review and meta-analysis of current clinical trials on PGE1 treatment for DKD.

(3) To determine the interventional effects of PGE1 on the renal composite outcomes in DKD patients and to provide a new evidence-based basis for optimizing the clinical management strategy of DKD.

(4) To elucidate the underlying mechanisms of PGE1 in delaying the progression of DKD through human renal biopsy tissues, animal models, and cellular experiments.

Methods

(1) Patients with DKD who underwent renal biopsy at China-Japan Friendship Hospital from November 2010 to May 2023 were included in this study. Clinical data and laboratory examination results of DKD patients were collected. The patients were divided into a DKD progression group and a stable group to analyze the clinical and pathological factors associated with DKD progression. A risk prognostic nomogram was developed to predict DKD progression using clinicopathologic parameters based on Cox regression analysis. Immunohistochemical staining was employed to detect the expression of E type prostanoid receptors in renal biopsy tissues from DKD patients, and their correlations with clinical parameters were analyzed.

(2) We searched MEDLINE, the Cochrane Library, Embase, and Chinese biomedical literature database (CBM) from January 1, 2000, to December 31, 2024 to identify all eligible trials. Studies published in any language were included. The search was restricted in randomized controlled trials (RCT) on PGE1 treatment for DKD. The intervention measures can include monotherapy with PGE1 or combination therapy with other drugs, while the control group may receive no treatment, placebo, or other medications. The primary efficacy outcome of this analysis was changes in renal function measures, including urinary albumin excretion rate (UAER), microalbuminuria, proteinuria, and serum creatinine at the end of the treatment and follow-up.

(3) The trial was conducted from December 2020 to December 2023. Patients with DKD hospitalized in China-Japan Friendship Hospital were screened according to inclusion and exclusion criteria. Patients with DKD receive an intravenous infusion of alprostadil in addition to standard-of-care treatment or receive only standard-of-care treatment. The primary outcome, assessed in a time-to-event analysis, was a composite of a sustained decline of at least 40% in the estimated glomerular filtration rate (eGFR) from baseline, or ESRD.

(4) Collect renal biopsy tissues from DKD patients and distal normal kidney tissues from a nephrectomy specimen with a renal tumor served as a control. Detect the expression of podocyte markers, EP1-4, α-synuclein (SNCA), and apoptosis markers in glomeruli using immunohistochemical staining methods. Establish a murine DKD model in db/db mice, then mice were randomly assigned to receive either equivalent volumes of vehicle (0.9% saline) or PGE1 by daily intravenous injection for 8 consecutive weeks, and all mice were euthanized after 8 weeks. Construct a high-glucose cultured human glomerular podocyte model and intervene with appropriate concentrations of the test compounds, including PGE1 and EP1-4 selective antagonists. Employ bioinformatics analysis combined with molecular biological techniques, including western blotting and qRT-PCR, to preliminarily investigate the underlying mechanisms through which PGE1 delays DKD progression.

Results

(1) In total, 142 patients that were eligible for inclusion were included in the final analysis. Results from univariate Cox proportional hazards model analysis revealed that clinical and pathological factors including eGFR, 24-hour urinary protein, Kimmelstiel-Wilson (K-W) nodules, segmental sclerosis, crescent-shaped changes, capillary microaneurysms, and C1q deposition were associated with the progression of DKD. However, results from multivariable Cox proportional hazards model analysis of DKD progression as a competing risk were shown that eGFR (hazard ratio [HR], 0.83; 95% confidence interval [95% CI], 0.74-0.94; P = 0.004) and 24-hour urinary protein (HR, 1.07; 95% CI, 1.02-1.12; P = 0.007) at presentation, as well as the presence of crescents (HR, 1.72; 95% CI, 1.07-2.76; P = 0.024) and capillary microaneurysms (HR, 2.02; 95% CI, 1.28-3.20; P = 0.003) in kidney biopsy, were the only clinicopathological factors to remain significant in the fully adjusted model. The Spearman correlation analysis results showed that the expression of glomerular EP2 receptor demonstrated a positive correlation with baseline eGFR levels (r = 0.315, P ＜0.001) and a negative correlation with baseline 24-hour urinary protein levels (r = -0.489, P ＜0.001). The C-index of the predictive model established based on Cox regression analysis was 0.73 (95% CI, 0.68-0.79).

(2) In total, 24 studies and 1,735 patients were recruited to investigate PGE1 with or without other drugs (ACEI, ARB, Chinese herbal medicines) versus other drugs or no treatment in the final analysis. All the studies were conducted in China. There was a significant decrease in UAER in patients treated with PGE1 versus no treatment (MD -1.31 µg/min; 95% CI, -1.98 to -0.65; P ＜0.001) or other drugs (MD -1.06 µg/min; 95% CI, -1.59 to -0.52; P ＜0.001). Meanwhile, compared with no treatment group, other outcomes also showed a significant decrease in the patients with PGE1 (albuminuria: MD -2.81 mg/24h; 95% CI -5.29 to -0.33; P ＜0.001; serum creatinine: MD -0.49 µmol/L; 95% CI -0.77 to -0.21; P ＜0.001). PGE1 combined with other drugs only had a positive effect on proteinuria (MD -1.78 g/24h; 95% CI -2.86 to -0.70; P = 0.001) in DKD patients compared with other drugs.

(3) In total, 218 patients that were eligible for inclusion were included in the final analysis. During a median follow-up of 12.3 months, a primary composite outcome event occurred in 46 of 218 patients (21.1%). Compared to the control group, treatment with alprostadil significantly delays the reduction of eGFR (P = 0.002) in patients with DKD. 24-hour urinary protein were reduced in both groups, but the decline of 24-hour urinary protein was more in alprostadil group than that in control group (P ＜0.001). In addition, the occurrence of adverse events was rare and did not significantly differ between the two groups (P = 0.113).

(4) Renal biopsy samples from patients with DKD revealed significantly increased expression of SNCA in glomeruli. Transcriptomics analysis allowed identification of SNCA as one of the significantly differentially expressed genes following the PGE1 intervention in DKD mouse model. Further experiments confirmed increased SNCA expression in the renal tissues of DKD mice, and that PGE1 intervention ameliorated renal injury while significantly reducing SNCA expression. Notably, PGE1 alleviated the high glucose-induced pathological aggregation of SNCA in podocytes and attenuated podocyte apoptosis. Importantly, the relieving effects of PGE1 on SNCA accumulation and podocyte apoptosis could be specifically abolished by EP2 receptor-selective antagonists. The EP2 receptor is the predominant E type prostanoid receptor expressed in human glomerular podocytes. PGE1 binding to the EP2 receptor stimulates cAMP production, which is a negative regulator of SNCA.

Conclusions

(1) In T2DM patients, proteinuria, eGFR, crescent-shaped changes and capillary microaneurysms serve as valuable predictors for DKD progression and renal prognosis in DKD. The presence of crescent-shaped changes and capillary microaneurysms accelerates disease progression in patients with DKD. The EP2 receptor is predominantly expressed in glomerular podocytes, and its decreased expression is associated with renal injury in patients with DKD.

(2) PGE1 treatment significantly improves renal prognostic indicators, including UAER, albuminuria, and proteinuria, in patients with DKD. However, the effect of PGE1 on serum creatinine levels in DKD patients remains inconclusive, and the heterogeneity in its therapeutic efficacy may be associated with fluctuations in drug exposure resulting from significant variations in dosage and treatment duration.

(3) In patients with DKD, when added to standard care, alprostadil resulted in marked reductions in proteinuria, deceleration of eGFR decline, and a lower risk of DKD progression with no obvious serious adverse events.

(4) Mechanistically, the renoprotective effects of PGE1 may involve EP2 receptor-mediated activation of AC, which stimulates cAMP production, thereby suppressing pathological SNCA aggregation-induced podocyte apoptosis in DKD.