FGF21 and obesity due to melanocortin 4 receptor deficiency: Previous studies demonstrated that A2AAR agonist treatment has anti-obesity effects partly via the activation of BAT thermogenesis and energy expenditure [8] and protected against hypertensive cardiac remodeling by facilitating the secretion of BAT-derived fibroblast growth factor 21, so-called “batokine” [21]; however, its crosstalk or synergistic effects with the activation of other adenosine receptors on adipocyte metabolism have not been fully investigated.