Long-term, progressive, aerobic training increases adiponectin in middle-aged, overweight, untrained males and females

Abstract

Adipose tissue secretes the adipokine, adiponectin (ADPN), which increases insulin sensitivity. Because some of the metabolic effects of exercise and ADPN are similar, exercise has been proposed to increase ADPN. However, most short-term (≤3 mos) and constant-effort exercise protocols have not produced increases in ADPN. Furthermore, no direct comparisons of male and female subjects on the effect of exercise on ADPN levels have been reported. We hypothesized that long-term (6 mos), progressive training would increase ADPN levels in both males and females. We recruited middle-aged, untrained males and females to participate in an interventional study employing a marathon training regimen progressing from 9.7 to 88.5 km (6 to 55 miles) per week over 6 mos. At baseline, we matched the mean ages of the male and female groups. We collected and stored fasting plasma samples and recorded body measurements at 0 (baseline) and 6 mos. Stored samples were analysed for insulin, glucose, and ADPN. ADPN increased significantly among both males (from 5.89 ± 2.46 (mean ± SD) to 7.65 ± 3.18 μg/ml; p < 0.05) and females (from 8.48 ± 3.22 to 10.56 ± 4.05 μg/ml; p < 0.05). The extent of the increase in ADPN was similar in the male (40.7 ± 50%; median, 12.1%) and female (27.0 ± 31.1%; median, 22.3%) groups. However, there was no significant reduction in insulin resistance as measured by the HOMA-IR scores in either group. We conclude that long-term, progressive aerobic training increases circulating ADPN levels in middle-aged, untrained males and females.

Key Words::

• Exercise
• intervention studies
• human
• adiponectin
• sex differences

Acknowledgements

We thank: Bobby Thomas, MBBS, for supervising the blood draw sessions; Grenith Zimmerman, PhD, and Khaled Bahjri, MD, MPH, for statistical advice; Stuart Seheult for developing the database; Glyne U. Thorington, PhD, for processing blood samples; the Board of Directors of the Lopers Club for permitting us to recruit subjects for the study; and the members of the Lopers Club for serving as subjects. Parts of this study were presented at The Obesity Society Annual Scientific Meeting, Phoenix, Arizona, 3–7 October 2008.

Funding: This research was supported by intramural grants 0316–6720 and 0316–6987 from Loma Linda University School of Medicine.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.