Cardiovascular Medicine (R.C., D.D., K.Z., A.R., S.R., J.N.S., S.M., R.A., E.R., S.C., C.A.L., K.M.C., B.C.), University of Oxford, Oxford United Kingdom.
Physiology, Anatomy and Genetics (D.T.), University of Oxford, Oxford United Kingdom.
Circ Res. 2021 Mar 5;128(5):585-601. doi: 10.1161/CIRCRESAHA.120.316656. Epub 2021 Jan 26.
In diabetic patients, heart failure with predominant left ventricular (LV) diastolic dysfunction is a common complication for which there is no effective treatment. Oxidation of the NOS (nitric oxide synthase) cofactor tetrahydrobiopterin (BH4) and dysfunctional NOS activity have been implicated in the pathogenesis of the diabetic vascular and cardiomyopathic phenotype.
Using mice models and human myocardial samples, we evaluated whether and by which mechanism increasing myocardial BH4 availability prevented or reversed LV dysfunction induced by diabetes.
In contrast to the vascular endothelium, BH4 levels, superoxide production, and NOS activity (by liquid chromatography) did not differ in the LV myocardium of diabetic mice or in atrial tissue from diabetic patients. Nevertheless, the impairment in both cardiomyocyte relaxation and [Ca]i (intracellular calcium) decay and in vivo LV function (echocardiography and tissue Doppler) that developed in wild-type mice 12 weeks post-diabetes induction (streptozotocin, 42-45 mg/kg) was prevented in mGCH1-Tg (mice with elevated myocardial BH4 content secondary to trangenic overexpression of GTP-cyclohydrolase 1) and reversed in wild-type mice receiving oral BH4 supplementation from the 12th to the 18th week after diabetes induction. The protective effect of BH4 was abolished by CRISPR/Cas9-mediated knockout of nNOS (the neuronal NOS isoform) in mGCH1-Tg. In HEK (human embryonic kidney) cells, S-nitrosoglutathione led to a PKG (protein kinase G)-dependent increase in plasmalemmal density of the insulin-independent glucose transporter GLUT-1 (glucose transporter-1). In cardiomyocytes, mGCH1 overexpression induced a NO/sGC (soluble guanylate cyclase)/PKG-dependent increase in glucose uptake via GLUT-1, which was instrumental in preserving mitochondrial creatine kinase activity, oxygen consumption rate, LV energetics (by phosphorous magnetic resonance spectroscopy), and myocardial function.
We uncovered a novel mechanism whereby myocardial BH4 prevents and reverses LV diastolic and systolic dysfunction associated with diabetes via an nNOS-mediated increase in insulin-independent myocardial glucose uptake and utilization. These findings highlight the potential of GCH1/BH4-based therapeutics in human diabetic cardiomyopathy. Graphic Abstract: A graphic abstract is available for this article.
在糖尿病患者中，以左心室（LV）舒张功能障碍为主的心力衰竭是一种常见的并发症，目前尚无有效的治疗方法。一氧化氮合酶（NOS）辅因子四氢生物蝶呤（BH4）的氧化和NOS 活性障碍与糖尿病血管和心肌病表型的发病机制有关。
本研究使用小鼠模型和人类心肌样本，评估增加心肌 BH4 含量是否以及通过何种机制预防或逆转糖尿病引起的 LV 功能障碍。
与血管内皮细胞不同，糖尿病小鼠的 LV 心肌或糖尿病患者的心房组织中，BH4 水平、超氧化物产生和 NOS 活性（通过液相色谱法测定）没有差异。然而，在野生型小鼠中，12 周后糖尿病诱导（链脲佐菌素，42-45mg/kg），心肌松弛和[Ca]i（细胞内钙）衰减以及体内 LV 功能（超声心动图和组织多普勒）受损，但在 mGCH1-Tg（由于 GTP 环化水解酶 1 的转基因过表达导致心肌 BH4 含量升高的小鼠）中得到预防，并在糖尿病诱导后第 12 至 18 周接受口服 BH4 补充的野生型小鼠中得到逆转。CRISPR/Cas9 介导的 nNOS（神经元 NOS 同工型）敲除消除了 BH4 的保护作用。在 HEK（人胚肾）细胞中，S-亚硝基谷胱甘肽导致胰岛素非依赖性葡萄糖转运蛋白 GLUT-1（葡萄糖转运蛋白-1）的质膜密度增加，依赖于蛋白激酶 G（PKG）。在心肌细胞中，mGCH1 过表达通过 NO/sGC（可溶性鸟苷酸环化酶）/PKG 依赖性增加 GLUT-1 来诱导葡萄糖摄取，这对于维持线粒体肌酸激酶活性、耗氧量、LV 能量学（通过磷磁共振波谱）和心肌功能至关重要。
本研究揭示了一种新的机制，即心肌 BH4 通过 nNOS 介导的增加胰岛素非依赖性心肌葡萄糖摄取和利用，预防和逆转与糖尿病相关的 LV 舒张和收缩功能障碍。这些发现强调了基于 GCH1/BH4 的治疗方法在人类糖尿病性心肌病中的潜力。
