In addition to liver and muscle, it has been suggested that FGF21 is inducible and secreted into the circulation in other tissues and organs under stress conditions. Brown adipose tissue (BAT) may be a source of FGF21 in response to cold stress and fetal-to-neonatal transition (28, 29). White adipose tissue (WAT) has been reported to secrete FGF21 under some conditions (30). However, a physiological contribution of stress-induced adipocyte FGF21 to systemic FGF21, or an autocrine activity of FGF21 within WAT, BAT, and adipocytes in the local microenvironment, remains to be validated. Since stressed pancreas has been reported to be a beneficiary of external FGF21 (31, 32), it is also a candidate for induction of FGF21 as a signal for aid from adipose tissue.
