From the Pauley Heart Center, Division of Cardiology, Virginia Commonwealth University, Richmond, Virginia 23298.
J Biol Chem. 2014 Feb 14;289(7):4145-60. doi: 10.1074/jbc.M113.521062. Epub 2013 Dec 26.
Elevated mammalian target of rapamycin (mTOR) signaling contributes to the pathogenesis of diabetes, with increased morbidity and mortality, mainly because of cardiovascular complications. Because mTOR inhibition with rapamycin protects against ischemia/reperfusion injury, we hypothesized that rapamycin would prevent cardiac dysfunction associated with type 2 diabetes (T2D). We also investigated the possible mechanisms and novel protein targets involved in rapamycin-induced preservation of cardiac function in T2D mice. Adult male leptin receptor null, homozygous db/db, or wild type mice were treated daily for 28 days with vehicle (5% DMSO) or rapamycin (0.25 mg/kg, intraperitoneally). Cardiac function was monitored by echocardiography, and protein targets were identified by proteomics analysis. Rapamycin treatment significantly reduced body weight, heart weight, plasma glucose, triglyceride, and insulin levels in db/db mice. Fractional shortening was improved by rapamycin treatment in db/db mice. Oxidative stress as measured by glutathione levels and lipid peroxidation was significantly reduced in rapamycin-treated db/db hearts. Rapamycin blocked the enhanced phosphorylation of mTOR and S6, but not AKT in db/db hearts. Proteomic (by two-dimensional gel and mass spectrometry) and Western blot analyses identified significant changes in several cytoskeletal/contractile proteins (myosin light chain MLY2, myosin heavy chain 6, myosin-binding protein C), glucose metabolism proteins (pyruvate dehydrogenase E1, PYGB, Pgm2), and antioxidant proteins (peroxiredoxin 5, ferritin heavy chain 1) following rapamycin treatment in db/db heart. These results show that chronic rapamycin treatment prevents cardiac dysfunction in T2D mice, possibly through attenuation of oxidative stress and alteration of antioxidants and contractile as well as glucose metabolic protein expression.
哺乳动物雷帕霉素靶蛋白（mTOR）信号的升高导致糖尿病的发病机制，发病率和死亡率增加，主要是因为心血管并发症。由于雷帕霉素抑制 mTOR 可防止缺血/再灌注损伤，我们假设雷帕霉素可预防 2 型糖尿病（T2D）相关的心脏功能障碍。我们还研究了雷帕霉素诱导 T2D 小鼠心脏功能的可能机制和涉及的新型蛋白靶点。成年雄性瘦素受体缺失、纯合子 db/db 或野生型小鼠每天用载体（5% DMSO）或雷帕霉素（0.25mg/kg，腹腔内注射）处理 28 天。通过超声心动图监测心脏功能，并通过蛋白质组学分析鉴定蛋白靶点。雷帕霉素治疗可显著降低 db/db 小鼠的体重、心脏重量、血浆葡萄糖、甘油三酯和胰岛素水平。雷帕霉素治疗可改善 db/db 小鼠的短轴缩短率。雷帕霉素处理可显著降低 db/db 心脏中的氧化应激（通过谷胱甘肽水平和脂质过氧化来衡量）。雷帕霉素可阻断 db/db 心脏中 mTOR 和 S6 的磷酸化增强，但不能阻断 AKT 的磷酸化增强。通过二维凝胶电泳和质谱的蛋白质组学（proteomics）和 Western blot 分析鉴定出，雷帕霉素处理后 db/db 心脏中的几种细胞骨架/收缩蛋白（肌球蛋白轻链 MLY2、肌球蛋白重链 6、肌球蛋白结合蛋白 C）、葡萄糖代谢蛋白（丙酮酸脱氢酶 E1、PYGB、Pgm2）和抗氧化蛋白（过氧化物还原酶 5、铁蛋白重链 1）的表达发生显著变化。这些结果表明，慢性雷帕霉素治疗可预防 T2D 小鼠的心脏功能障碍，可能是通过减轻氧化应激和改变抗氧化剂以及收缩和葡萄糖代谢蛋白的表达来实现的。
