Coronary microvascular dysfunction is prevalent among people with diabetes and is correlated with cardiac mortality. Compromised endothelial-dependent dilation (EDD) is an early event in the progression of diabetes, but its mechanisms remain incompletely understood. Nitric oxide (NO) is the major endothelium-dependent vasodilatory metabolite in the healthy coronary circulation, but this switches to hydrogen peroxide (H₂O₂) in coronary artery disease (CAD) patients. Because diabetes is a significant risk factor for CAD, we hypothesized that a similar NO-to-H₂O₂ switch would occur in diabetes. Vasodilation was measured ex vivo in isolated coronary arteries from wild type (WT) and microRNA-21 (miR-21) null mice on a chow or high-fat/high-sugar diet, and B6.BKS(D)-Lepr^db/J (db/db) mice using myography. Myocardial blood flow (MBF), blood pressure, and heart rate were measured in vivo using contrast echocardiography and a solid-state pressure sensor catheter. RNA from coronary arteries, endothelial cells, and cardiac tissues was analyzed via quantitative real-time PCR for gene expression, and cardiac protein expression was assessed via western blot analyses. Superoxide was detected via electron paramagnetic resonance. (1) Ex vivo coronary EDD and in vivo MBF were impaired in diabetic mice. (2) Nω-Nitro-L-arginine methyl ester, an NO synthase inhibitor (L-NAME), inhibited ex vivo coronary EDD and in vivo MBF in WT. In contrast, polyethylene glycol-catalase, an H₂O₂ scavenger (Peg-Cat), inhibited diabetic mouse EDD ex vivo and MBF in vivo. (3) miR-21 was upregulated in diabetic mouse endothelial cells, and the deficiency of miR-21 prevented the NO-to-H₂O₂ switch and ameliorated diabetic mouse vasodilation impairments. (4) Diabetic mice displayed increased serum NO and H₂O₂, upregulated mRNA expression of Sod1, Sod2, iNos, and Cav1, and downregulated Pgc-1α in coronary arteries, but the deficiency of miR-21 reversed these changes. (5) miR-21-deficient mice exhibited increased cardiac PGC-1α, PPARα and eNOS protein and reduced endothelial superoxide. (6) Inhibition of PGC-1α changed the mRNA expression of genes regulated by miR-21, and overexpression of PGC-1α decreased the expression of miR-21 in high (25.5 mM) glucose treated coronary endothelial cells. Diabetic mice exhibit a NO-to-H₂O₂ switch in the mediator of coronary EDD, which contributes to microvascular dysfunction and is mediated by miR-21. This study represents the first mouse model recapitulating the NO-to-H₂O₂ switch seen in CAD patients in diabetes.

冠状动脉微血管功能障碍在糖尿病患者中很普遍，并且与心脏死亡率相关。受损的内皮依赖性扩张 (EDD) 是糖尿病进展的早期事件，但其机制仍未完全了解。一氧化氮 (NO) 是健康冠状动脉循环中主要的内皮依赖性血管舒张代谢物，但在冠状动脉疾病 (CAD) 患者中会转变为过氧化氢 (H ₂ O _{2 )。}由于糖尿病是 CAD 的重要危险因素，我们假设类似的 NO-to-H ₂ O ₂转换会发生在糖尿病中。在来自野生型 (WT) 和 microRNA-21 (miR-21) 缺失小鼠的离体冠状动脉中测量血管舒张，这些小鼠采用食物或高脂肪/高糖饮食，以及 B6.BKS(D)-Lepr ^db / J (分贝/分贝) 小鼠使用 myography。使用造影超声心动图和固态压力传感器导管在体内测量心肌血流量 (MBF)、血压和心率。通过定量实时 PCR 分析来自冠状动脉、内皮细胞和心脏组织的 RNA 的基因表达，并通过蛋白质印迹分析评估心脏蛋白表达。通过电子顺磁共振检测超氧化物。(1) 离体冠状动脉 EDD 和体内 MBF 在糖尿病小鼠中受损。(2) Nω-硝基-L-精氨酸甲酯，一种 NO 合酶抑制剂 (L-NAME)，在 WT 中抑制离体冠状动脉 EDD 和体内 MBF。相反，聚乙二醇过氧化氢酶，一种 H ₂ O ₂清道夫 (Peg-Cat)，体外抑制糖尿病小鼠 EDD 和体内 MBF。(3) miR-21在糖尿病小鼠内皮细胞中表达上调，miR-21的缺乏阻止了NO-to-H ₂ O ₂的转换，改善了糖尿病小鼠血管舒张功能障碍。(4)糖尿病小鼠血清NO和H ₂ O ₂升高，Sod1、Sod2、iNos和Cav1 mRNA表达上调，冠状动脉Pgc-1α下调，但miR-21缺乏可逆转这些变化。(5)和平号空间站 21- 缺陷小鼠表现出心脏 PGC-1α、PPARα 和 eNOS 蛋白增加，内皮超氧化物减少。(6) PGC-1α的抑制改变了miR-21调控基因的mRNA表达，PGC-1α的过表达降低了高(25.5 mM)葡萄糖处理的冠状动脉内皮细胞中miR-21的表达。糖尿病小鼠在冠状动脉 EDD 的介质中表现出从 NO 到 H ₂ O ₂的转换，这会导致微血管功能障碍并由 miR-21 介导。这项研究代表了第一个小鼠模型，它概括了在糖尿病 CAD 患者中观察到的 NO-to-H ₂ O _2转换。