Ciliary Neurotrophic Factor in Skeletal Muscle of Older Adults and the Effects of Weight Loss and Aerobic Training.

Background/Objectives: Ciliary neurotrophic factor (CNTF), a pleiotropic cytokine with central and peripheral actions, has been implicated in obesity, insulin resistance, and aging, yet its role in skeletal muscle and cardiometabolic health remains unclear. This study examined skeletal muscle CNTF mRNA expression in relation to adiposity and glucose tolerance in older adults and assessed the effects of six-month weight loss (WL) and aerobic exercise training (AEX) interventions on its expression. Methods: Sixty-seven adults (age, 60.75 ± 7.58) underwent a vastus lateralis muscle biopsy, VO2max testing, dual-energy X-ray absorptiometry (DXA) scan, a resting metabolic rate (RMR) and substrate oxidation assessment, and a 3-h oral glucose tolerance test with glucose and insulin area under the curve (AUC) calculation. A subset completed 6 months of either a WL program (n = 21) or a supervised 3 times per week AEX intervention (n = 20). Results: At baseline, skeletal muscle CNTF expression was inversely associated with RMR, fat oxidation, 3-h glucose AUC, and insulin AUC, but not with BMI, percent body fat, or VO2max. WL reduced body weight, fat mass, glucose AUC, insulin AUC, and basal muscle CNTF expression, whereas AEX increased VO2max and reduced fat mass without altering body weight, glucose AUC, insulin AUC, or basal CNTF. Insulin-stimulated CNTF expression increased after both WL and AEX, and the intervention-induced change in glucose disposal (M) was positively associated with the change in insulin-stimulated CNTF. Conclusions: In older adults, skeletal muscle CNTF is associated with glucose intolerance but is not associated with body composition or aerobic fitness. Improvements in insulin sensitivity are associated with increases in muscle CNTF during hyperinsulinemia. Further work is needed to determine the mechanism for muscle CNTF change during hyperinsulinemia after weight loss and exercise training, and its role in glucose metabolism and obesity in older adults.