Introduction: Adipose tissue plays complex role(s) in metabolic and endocrine control. To date, little work has been done in the horse regarding adipocytokines.
Purpose: This study was conducted to determine whether therapeutic levels of chronic β-agonist administration, exercise, or both could alter their concentrations.
Methods: A total of 23 standard-bred mares were divided into four experimental groups: clenbuterol (2.4 μg·kg−1 bw twice daily for 8 wk) plus exercise (8 wk, 20 min·d−1 at 50% V̇O2max; CLENEX; N = 6), clenbuterol only (CLEN; N = 6), exercise only (EX; N = 5), and control (CON; N = 6). Rump fat thickness was measured using B-mode ultrasound and percent body fat (%fat) was calculated. Plasma adiponectin and leptin concentrations were measured using radioimmunoassay (RIA). In the absence of purified equine adiponectin or leptin, results were expressed as human equivalents of immunoreactive adipocytokines.
Results: The change in plasma immunoreactive (ir)-adiponectin HE concentration was negatively correlated (r = −0.520; P = 0.01) to the change in fat mass and positively correlated (r = 0.446; P = 0.03) to the change in fat-free mass. The change in plasma ir-leptin HE concentration was positively correlated (r = 0.550; P = 0.02) to the change in fat mass and negatively correlated (r = −0.473; P < 0.05) to the change in fat-free mass.
Conclusion: These data demonstrate that a chronic clenbuterol administration alters the concentrations of the adipocytokines adiponectin and leptin in horses. These changes may play a role in previously reported repartitioning effects of clenbuterol.
1Equine Science Center, Department of Animal Science, Rutgers the State University of New Jersey, New Brunswick, NJ; and 2Schering-Plough Research Institute, Kenilworth, NJ
Address for correspondence: Kenneth H. McKeever, Ph.D., FACSM, Department of Animal Sciences, 84 Lipman Drive, New Brunswick, NJ 08901-8525; E-mail: firstname.lastname@example.org.
Submitted for publication January 2005.
Accepted for publication July 2005.