Aerobic Exercise Increases Meteorin-Like Protein in Muscle and Adipose Tissue of Chronic High-Fat Diet-Induced Obese Mice

Upregulated meteorin-like (Metrnl) protein in peripheral tissues because of exercise-induced increases in intramuscular Metrnl may effectively alleviate obesity by improving metabolism in whole-body tissues. The objective was to analyse the effects of regular treadmill exercise on Metrnl levels in muscle and peripheral tissues of chronic high-fat diet- (HFD-) induced obese mice. Forty-eight-week-old male C57BL/6 mice were first divided equally into normal-diet (CO) and high-fat diet (HF) groups. Following 16 weeks of a HFD, each group was again split equally into control (CO, HF) and training groups (COT, HFT). The HFT group expressed significantly higher phospho-AMP-activated protein kinase (AMPK), AMPK activity, and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) in muscle tissue than the HF group (p < 0.05). Similar to muscle energy sensing network protein levels, the HFT group also expressed significantly higher muscle, plasma, and adipose tissue Metrnl (p < 0.05). Moreover, regular exercise increased acyl-CoA oxidase 1 (ACOX-1) and monoglyceride lipase (MGL) expression in adipose tissue (p < 0.05) and significantly decreased abdominal fat mass (p < 0.05). This study suggests that exercise-induced muscle Metrnl effectively reduces fat accumulation through the increase of Metrnl in adipose tissue, which may be a therapeutic target for chronic obesity.