Tangeretin ameliorates abnormal irisin secretion in high-fat diet-induced obese mice via SESN2/AMPK/PGC-1α pathway

Irisin, a newly discovered myokine, plays an important role in maintaining energy balance and improving metabolic diseases. Tangeretin (TAN) is a natural active substance mainly found in the peel of citrus fruits, which has been reported to affect skeletal muscle function and prevent obesity-related metabolic diseases. However, the potential impact of TAN on the control of fibronectin type Ⅲ domain-containing protein 5 (FNDC5)/irisin expression remains poorly understood. C2C12 cells, C57BL/6J mice, and HFD-induced obese mouse models were used in this study. Following treatment with TAN, the metabolic activity of mice was evaluated by metabolic cages, glucose tolerance test (GTT), and insulin tolerance test (ITT). Changes in relevant serum indices were detected by biochemical kits. The expression of FNDC5 in vivo and in vitro was examined by Q-PCR, Western blot, and immunostaining, and the binding effect of TAN and Sestrin2 (SESN2) was analyzed by molecular dynamics. We found that TAN treatment promoted irisin production and secretion in both C2C12 myotubular cells and C57BL/6J mice. The rise in irisin levels was found to be associated with the upregulation of FNDC5 expression, which was mediated via the SESN2/AMPK/PGC-1α signaling pathway. Moreover, this positive action by TAN was further verified in an obese mouse model induced by a high-fat diet (HFD). We found that TAN supplementation effectively resisted the decrease in circulating irisin levels and activated the SESN2 signaling axis expression in skeletal muscle, which may result in significantly improving metabolic parameters in HFD-fed mice. Our findings revealed that TAN counteracts the HFD-induced decrease in irisin secretion and improves glucose and lipid metabolism in obese mice by activating the SESN2/AMPK/PGC1-α/FNDC5 signaling axis. These findings present a novel opportunity for TAN to ameliorate irisin deficiency and other metabolic disorders.