Xiong Yan, Hai Chun-Xia, Fang Wei-Jin, Lei Yan-Ping, Li Xiao-Mei, Zhou Xin-Ke
Department of Central Laboratory, The Fifth Affiliated Hospital of Guangzhou Medical University, Guangzhou, 510700 Guangdong China.
Guangzhou Institute of Snake Venom Research, Guangzhou Medical University, Guangzhou, 511436 Guangdong China.
Nutr Metab (Lond). 2020 Aug 24;17:72. doi: 10.1186/s12986-020-00486-4. eCollection 2020.
Suppressed mitochondrial biosynthesis has been reported to be the early signal of mitochondrial dysfunction which contributes to diabetic cardiomyopathy, but the mechanism of mitochondrial biosynthesis suppression is unclear. Nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) is closely related to diabetic cardiovascular complications. This study was to determine whether endogenous ADMA accumulation was involved in the suppression of myocardial mitochondrial biogenesis in diabetic rats and to elucidate the potential mechanism in rat cardiomyocytes.
Type 2 diabetic rat model was induced by high-fat feeding plus single intraperitoneal injection of small dose streptozotocin (35 mg/kg). The copy number ratio of mitochondrial gene to nuclear gene was measured to reflect mitochondrial biogenesis. The promoter activity of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) and its post-translational modifications were detected by dual-luciferase reporter assay and immunoprecipitation.
Myocardial ADMA content was enhanced and associated with suppressions of myocardial mitochondrial biogenesis and cardiac function in parallel with PGC-1α downregulation and uncoupling protein 2 (UCP2) upregulation in the myocardium of diabetic rats compared with control rats. Similarly, ADMA and its homolog could inhibit myocardial mitochondrial biogenesis and PGC-1α expression, increase UCP2 expression and oxidative stress in vitro and in vivo. Moreover, ADMA also suppressed the promoter activity and PGC-1α expression but boosting its protein acetylation and phosphorylation in rat cardiomyocytes.
These results indicate that endogenous ADMA accumulation contributes to suppression of myocardial mitochondrial biogenesis in type 2 diabetic rats. The underlying mechanisms may be associated with reducing PGC-1α promoter activity and expression but boosting its protein acetylation and phosphorylation.
据报道，线粒体生物合成受抑制是线粒体功能障碍的早期信号，而线粒体功能障碍会导致糖尿病性心肌病，但线粒体生物合成受抑制的机制尚不清楚。一氧化氮合酶抑制剂不对称二甲基精氨酸（ADMA）与糖尿病心血管并发症密切相关。本研究旨在确定内源性ADMA蓄积是否参与糖尿病大鼠心肌线粒体生物发生的抑制，并阐明大鼠心肌细胞中的潜在机制。
通过高脂喂养加单次腹腔注射小剂量链脲佐菌素（35mg/kg）诱导2型糖尿病大鼠模型。测量线粒体基因与核基因的拷贝数比以反映线粒体生物发生。通过双荧光素酶报告基因检测和免疫沉淀检测过氧化物酶体增殖物激活受体γ共激活因子1α（PGC-1α）的启动子活性及其翻译后修饰。
与对照大鼠相比，糖尿病大鼠心肌中ADMA含量增加，且与心肌线粒体生物发生抑制和心脏功能障碍相关，同时伴有心肌中PGC-1α下调和解偶联蛋白2（UCP2）上调。同样，ADMA及其同系物在体内外均可抑制心肌线粒体生物发生和PGC-1α表达，增加UCP2表达和氧化应激。此外，ADMA还抑制大鼠心肌细胞中PGC-1α的启动子活性和表达，但增强其蛋白乙酰化和磷酸化。
这些结果表明，内源性ADMA蓄积导致2型糖尿病大鼠心肌线粒体生物发生受抑制。潜在机制可能与降低PGC-1α启动子活性和表达，但增强其蛋白乙酰化和磷酸化有关。
