As a first responder to the SOS message carried by FGF21, how do adipocytes through FGF21-mediated activation of FGFR1-KLB aid stressed tissues and in particular liver and muscle? In addition to as a reservoir of energy, adipose tissue is an endocrine organ capable of systemic signaling through its lipid metabolites and adipokines (47, 48). A number of effects of FGF21 on adipose tissue adipocytes have been reported. These include the induction of expression of nuclear receptors and coactivators, diverse enzymes and their cytoplasmic regulators involved in pathways for glucose, lipid, and energy metabolism, and the broad changes in systemic and local tissue metabolic substrates and control pathways (1, 2, 4, 9, 40, 43).
