FNDC5 and metabolic disease: Experimental studies have shown that, in addition to its metabolic effects, irisin exerts anti-inflammatory, antioxidant, and anti-apoptotic activities, suggesting that it may be a potent immunometabolic regulator with a protective role not only in chronic subclinical inflammatory conditions such as obesity and related metabolic disorders but also in acute inflammatory states such as sepsis [13,16,46].