Fibroblast Growth Factor 21 Mediates the Associations between Exercise, Aging, and Glucose Regulation

Introduction Aging increases the prevalence of glucose intolerance, but exercise improves glucose homeostasis. The fibroblast growth factor 21 (FGF21)-adiponectin axis helps regulate glucose metabolism. However, the role of FGF21 in mediating glucose metabolism with aging and exercise remains unknown. Purpose This study examined whether FGF21 responses to a glucose challenge are associated with habitual exercise, aging and glucose regulation. Methods Eighty age- A nd sex-matched healthy individuals were assigned to young sedentary and active (≤36 yr, n = 20 each group) and older sedentary and active (≥45 yr, n = 20 each group) groups. Fasted and postprandial blood glucose concentration and plasma concentration of insulin, FGF21, and adiponectin were determined during an oral glucose tolerance test (OGTT). Results During the OGTT, glucose concentrations were 9% higher (P = 0.008) and FGF21 concentrations were 58% higher (P = 0.014) in the older than the younger group, independent of activity status. Active participants had 40% lower insulin concentration and 53% lower FGF21 concentration than sedentary participants, independent of age (all P < 0.001). Adiponectin concentration during the OGTT did not differ by age (P = 0.448) or activity status (P = 0.611). Within the younger group, postprandial glucose, insulin and FGF21 concentrations during the OGTT were lower in active than in sedentary participants. In the older group, only postprandial insulin and FGF21 concentrations were lower in active participants. Conclusions FGF21, but not adiponectin, response during the OGTT is higher in older than younger adults and lower in active than sedentary individuals. Exercise-associated reduction in OGTT glucose concentrations was observed in younger but not older adults.