Thapa Dharendra, Nichols Cody E, Lewis Sara E, Shepherd Danielle L, Jagannathan Rajaganapathi, Croston Tara L, Tveter Kevin J, Holden Anthony A, Baseler Walter A, Hollander John M
West Virginia University School of Medicine, Division of Exercise Physiology, Center for Cardiovascular and Respiratory Sciences, Morgantown, WV 26506, USA.
West Virginia University School of Medicine, Department of Surgery, Morgantown, WV 26506, USA.
J Mol Cell Cardiol. 2015 Feb;79:212-23. doi: 10.1016/j.yjmcc.2014.11.008. Epub 2014 Nov 22.
Mitofilin, also known as heart muscle protein, is an inner mitochondrial membrane structural protein that plays a central role in maintaining cristae morphology and structure. It is a critical component of the mitochondrial contact site and cristae organizing system (MICOS) complex which is important for mitochondrial architecture and cristae morphology. Our laboratory has previously reported alterations in mitochondrial morphology and proteomic make-up during type 1 diabetes mellitus, with mitofilin being significantly down-regulated in interfibrillar mitochondria (IFM). The goal of this study was to investigate whether overexpression of mitofilin can limit mitochondrial disruption associated with the diabetic heart through restoration of mitochondrial morphology and function. A transgenic mouse line overexpressing mitofilin was generated and mice injected intraperitoneally with streptozotocin using a multi low-dose approach. Five weeks following diabetes mellitus onset, cardiac contractile function was assessed. Restoration of ejection fraction and fractional shortening was observed in mitofilin diabetic mice as compared to wild-type controls (P<0.05 for both). Decrements observed in electron transport chain (ETC) complex I, III, IV and V activities, state 3 respiration, lipid peroxidation as well as mitochondria membrane potential in type 1 diabetic IFM were restored in mitofilin diabetic mice (P<0.05 for all). Qualitative analyses of electron micrographs revealed restoration of mitochondrial cristae structure in mitofilin diabetic mice as compared to wild-type controls. Furthermore, measurement of mitochondrial internal complexity using flow cytometry displayed significant reduction in internal complexity in diabetic IFM which was restored in mitofilin diabetic IFM (P<0.05). Taken together these results suggest that transgenic overexpression of mitofilin preserves mitochondrial structure, leading to restoration of mitochondrial function and attenuation of cardiac contractile dysfunction in the diabetic heart.
线粒体肌动蛋白，也被称为心肌蛋白，是一种线粒体内膜结构蛋白，在维持嵴的形态和结构方面发挥着核心作用。它是线粒体接触位点和嵴组织系统（MICOS）复合物的关键组成部分，对线粒体结构和嵴形态很重要。我们实验室之前报道过1型糖尿病期间线粒体形态和蛋白质组构成的改变，线粒体内肌间线粒体（IFM）中的线粒体肌动蛋白显著下调。本研究的目的是调查线粒体肌动蛋白的过表达是否能通过恢复线粒体形态和功能来限制与糖尿病心脏相关的线粒体破坏。构建了一种过表达线粒体肌动蛋白的转基因小鼠品系，并使用多次低剂量方法给小鼠腹腔注射链脲佐菌素。糖尿病发病五周后，评估心脏收缩功能。与野生型对照组相比，在过表达线粒体肌动蛋白的糖尿病小鼠中观察到射血分数和缩短分数恢复（两者P<0.05）。在过表达线粒体肌动蛋白的糖尿病小鼠中，1型糖尿病IFM中观察到的电子传递链（ETC）复合物I、III、IV和V活性、状态3呼吸、脂质过氧化以及线粒体膜电位的降低均得到恢复（所有P<0.05）。电子显微镜照片的定性分析显示，与野生型对照组相比，过表达线粒体肌动蛋白的糖尿病小鼠中线粒体嵴结构得以恢复。此外，使用流式细胞术测量线粒体内部复杂性显示，糖尿病IFM中的内部复杂性显著降低，而过表达线粒体肌动蛋白的糖尿病IFM中则恢复（P<0.05）。综上所述，这些结果表明线粒体肌动蛋白的转基因过表达可保留线粒体结构，从而恢复线粒体功能并减轻糖尿病心脏的心脏收缩功能障碍。
