Wild Bitter Melon Extract Assists IGF-1 in Promoting Mouse Skeletal Muscle Cell Proliferation Through PI3K/Akt Pathway

• Main Authors: Yii-Tzu Huang, 黄苡慈
• Other Authors: 黃青真
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/g8p667

碩士 === 國立臺灣大學 === 生化科技學系 === 106 === Sarcopenia is a gradual loss of skeletal muscle mass, function and strength associated with ageing. The main causes of sarcopenia include loss of motor neurons, physical inactivity or a decline in anabolic hormones such as testosterone and insulin-like growth factor-1 (IGF-1), which lead to reduction in regenerative capacity or increased protein degradation in skeletal muscle. Currently, the validated strategies are exercise and nutritional supplementation. On the other hand, the pathways which stimulate muscle hypertrophy have been actively investigated. Wild bitter gourd (WBG) has been shown to ameliorate metabolic disorders such as hyperglycemia and hyperlipidemia. However, little research was focussed on muscle growth. Hence, the aim of this study is to examine the effect of WBG on skeletal muscle growth and function as an initial approach. In the cell model, C2C12 myoblasts were treared with WBG extracts for 48 hours to determine the proliferation ability of WBG. The results showed that the WBG cultivar 1758 ethyl acetate extract (EAE) enchanced the activity of citrate synthase, a marker of mitochondria, and, in the presence of IGF-I, promoted myoblasts proliferation. The effect of 1758 EAE on IGF-1-mediated proliferation was diminished in the presence of PI3K inhibitor LY294002. Western blot analysis further showed that 1758 EAE increased Akt phosphorylation of C2C12 myoblasts in the presence of IGF-I after 1 hour of treatment. In the short-term animal study, C57/BL/6J male mice were fed a high-fat diet supplemented without or with 4% various cultivars of WBG for 4 weeks. WBG reduced total body weight, white adipose mass, insulin resistance, and increased relative gastrocnemius muscle mass. 1758 WBG specifically enhanced mRNA expression levels of IGF-1, Igf1r, Akt2, Hk2 in gastrocnemius muscle. These results indicate that 1758 WBG may enhance the proliferation effect of IGF-1 in myoblasts, and might regulate IGF-1 signaling pathway in skeletal muscle.