Liu Shuge, Sun Yunmei, Zhao Rui, Wang Yingqian, Zhang Wanrong, Pang Weijun
Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, Laboratory of Animal Fat Deposition and Muscle Development, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.
Food Funct. 2021 Jan 7;12(1):144-153. doi: 10.1039/d0fo02156c. Epub 2020 Dec 8.
Isoleucine (Ile), as a branched-chain amino acid (BCAA), has a vital role in regulating body weight and muscle protein synthesis. However, the regulatory effect of Ile on muscle mass under high-fat diet (HFD) conditions and intramyocellular lipid deposition remains largely unclear. In this study, a feeding experiment with HFD with or without 25 g L Ile was performed using 32 wild male C57BL/6J mice randomly divided into two groups. The results showed that Ile significantly increased both muscle and fat mass, as well as causing insulin resistance and meanwhile upregulating the levels of key adipogenic and myogenic proteins. More importantly, Ile damaged the mitochondrial function by vacuolation, swelling and cristae fracture in the gastrocnemius (GAS) and tibialis anterior (TA) with downregulation of mitochondrial function-related genes. Furthermore, Ile promoted myogenesis and more lipid droplet accumulation in myotubes. Compared with the control, the protein levels of myosin heavy chain (MyHC), myoblast determination protein 1 (MyoD), myogenin (MyoG), peroxisome proliferator-activated receptor gamma (PPARg) and fatty acid synthase (FAS) were upregulated in the Ile group, whereas the protein levels of adipose triglyceride lipase (ATGL) and lipoprotein lipase (LPL) were downregulated. Collectively, Ile increased muscle mass through myogenesis and intramyocellular lipid deposition. Our findings provide a new perspective for not only improving the lean juiciness of farm animals by increasing intramyocellular lipid accumulation, but also modulating myopathies under obesity.
异亮氨酸（Ile）作为一种支链氨基酸（BCAA），在调节体重和肌肉蛋白质合成方面起着至关重要的作用。然而，在高脂饮食（HFD）条件下，异亮氨酸对肌肉质量和肌细胞内脂质沉积的调节作用仍不清楚。在本研究中，我们使用32只野生雄性C57BL/6J小鼠进行了一项喂食实验，将其随机分为两组，分别喂食含或不含25 g/L异亮氨酸的高脂饮食。结果表明，异亮氨酸显著增加了肌肉和脂肪量，同时导致胰岛素抵抗，并上调了关键的脂肪生成和肌生成蛋白水平。更重要的是，异亮氨酸通过腓肠肌（GAS）和胫骨前肌（TA）中的空泡化、肿胀和嵴断裂破坏了线粒体功能，并下调了线粒体功能相关基因。此外，异亮氨酸促进了肌管中的肌生成和更多脂滴积累。与对照组相比，异亮氨酸组中肌球蛋白重链（MyHC）、成肌细胞决定蛋白1（MyoD）、肌细胞生成素（MyoG）、过氧化物酶体增殖物激活受体γ（PPARg）和脂肪酸合酶（FAS）的蛋白水平上调，而脂肪甘油三酯脂肪酶（ATGL）和脂蛋白脂肪酶（LPL）的蛋白水平下调。总的来说，异亮氨酸通过肌生成和肌细胞内脂质沉积增加了肌肉质量。我们的研究结果不仅为通过增加肌细胞内脂质积累来改善农场动物的瘦肉多汁性，也为调节肥胖症下的肌病提供了新的视角。
