OBJECTIVE-Fibroblast growth factor (FGF)-21 is an endocrine factor with potentmetabolic effects. Its day-night patterns of secretion and/or its physiological response to energy deprivation and relationship to free fatty acids (FFAs) and/or leptin remain to be fully elucidated.We aim to elucidate day-night pattern of FGF-21 levels and its relationship to FFA, to assesswhether energy deprivation alters its circulating patterns, and to examine whether leptin may mediate these changes. RESEARCH DESIGN AND METHODS-Six healthy lean females were studied for 72 h in a cross-over interventional study under three different conditions: on isocaloric diet and in a fasting state with administration of either placebo or metreleptin in physiological replacement doses. Blood samples were obtained hourly from 8:00 A.M. on day 4 until 8:00 A.M. on day 5. RESULTS-FGF-21 exhibited day-night variation pattern during the isocaloric fed state. Fasting significantly increased FGF-21 levels (P < 0.01) via a leptin-independent pathway. Day-night variation pattern in the fed state was lost on fasting. Leptin replacement in the hypoleptinemic state restored approximate entropy of FGF-21 time series but did not alter circulating levels. FGF-21 levels were closely cross-correlated with FFA levels in all three states. CONCLUSIONS-A day-night variation in the levels of FGF-21 exists in young lean females in the fed state. Energy deprivation increases FGF-21 levels via a leptin-independent pathway. The interaction between FGF-21 and starvation-induced lipolysis, as indicated by its close crosscorrelations with FFA in both fed state and energy deprivation, needs to be studied further.
ASJC Scopus subject areas
- Internal Medicine
- Endocrinology, Diabetes and Metabolism
- Advanced and Specialised Nursing