RBP4 and Insulin resistance: In comparison to adropin and irisin, RBP4 is involved in the pathogenesis of insulin resistance by exerting numerous deleterious metabolic actions in adipose tissue, skeletal muscle, and the liver (Figure 1) (Yang et al., 2005; Ost et al., 2007; Norseen et al., 2012; Lee et al., 2016).