Long-term, Aerobic Training Increases Adiponectin Levels in Trained, Middle-aged Females more than in Comparable Males

Both aerobic training and the adipokine, adiponectin (ADPN), increase insulin sensitivity.  Because the metabolic effects of aerobic training and ADPN are similar, aerobic training has been proposed to increase ADPN, which has been generally confirmed.  However, in separate studies physically active adolescent females showed higher ADPN levels than sedentary controls, but trained young males showed no increase in ADPN levels.  Because no direct comparison of males and females have been provided and because physically fit middle-aged adults have been largely neglected from studies on the effects of exercise on ADPN levels, we hypothesized that long-term (6 months), progressive long-distance training would increase ADPN levels more in trained, middle-aged females than in comparably trained, middle-aged males.  We recruited aerobically trained, normal-weight, middle-aged females (n=8) and males (n=10) to participate in a prescribed marathon training protocol progressing from 10 to 90 km (6 to 55 miles) per week over 6 mos.  We collected and stored fasting plasma samples and recorded body measurements at 0 (baseline) and 6 mos.  Stored samples were analyzed for insulin, glucose, and ADPN.  ADPN increased significantly among females [from 18.37 ± 10.39 (mean ± SD) to 22.50 ± 9.87 µg/ml; P<0.05], but non-significantly among males (from 6.69 ± 4.47 to 8.10 ± 5.57 µg/ml; P=0.2).  No significant reduction in insulin resistance or anthropometric measurements occurred in either group.  Our findings suggest that long-term, progressive aerobic training produces greater increases in circulating ADPN levels in trained, middle-aged, normal-weight females than in comparably trained males.