INTRODUCTION: Fetuin-A is a novel hepatokine and there is preliminary evidence that it may contribute to the pathogenesis of type 2 diabetes. Exercise reduces fetuin-A, but the specific metabolic effects particularly as they relate to the regulation of insulin resistance are unknown. This led us to examine the effect of exercise training on circulating fetuin-A in relation to skeletal muscle and/or hepatic insulin resistance in obese adults.
METHODS: Twenty older (66.3+/-0.9 yr, BMI 34.1+/-1.2 kg/m2) adults participated in this prospective, 12-week study and underwent supervised exercise training (5 d/wk, 60 min/d at ~85% HRmax). Insulin resistance was assessed using the euglycemic hyperinsulinemic (40 mU/m2[middle dot]min-1) clamp with isotope dilution ([6,6-2H2]-glucose). Skeletal muscle insulin sensitivity (rate of glucose disposal), hepatic insulin resistance (rate of glucose appearance x fasting insulin), metabolic flexibility (RQClamp - RQFasting), fetuin-A, HMW-adiponectin, hs-CRP, leptin and body fat (iDXA) were measured before and after the intervention.
RESULTS: Exercise reduced body fat, hs-CRP, leptin and hepatic as well as skeletal muscle insulin resistance (each P<0.05). Fetuin-A was decreased by ~8% (Pre: 1.01+/-0.08 vs. Post: 0.89+/-0.06 g/L, P<0.05) following the intervention, and lower fetuin-A after exercise correlated with lower hepatic insulin resistance (r=-0.46, P<0.01), increased metabolic flexibility (r=-0.70, P<0.01) and HMW-adiponectin (r=-0.57, P<0.01).
CONCLUSION: Fetuin-A may contribute to exercise training-induced improvements in hepatic insulin resistance, carbohydrate utilization, and inflammation in older obese adults. Further work is required to determine the cellular mechanism(s) of action for fetuin-A, as this hepatokine is related to type 2 diabetes risk.
(C) 2014 American College of Sports Medicine