Exercise-induced alterations in plasma concentrations of ghrelin, adiponectin, leptin, glucose, insulin, and cortisol in horses.

Six Standardbred (STB) mares (11+/-2 years, 521+/-77 kg; means+/-SD) performed an exercise trial (EX) where they underwent an incremental exercise test (GXT) as well as a parallel control trial (CON) to test the hypothesis that short-term, high intensity exercise would alter plasma concentrations of glucose, leptin, adiponectin, ghrelin, insulin and cortisol. Plasma samples were taken before (0 min), during (last 10s at 6, 8m/s, and the velocity eliciting VO(2max)), and after exercise (2, 10, 30, 60 min; 12 and 24h post-GXT). A second set of blood samples was collected before and after an afternoon meal given at 1515 h (at 1500, 1514, 1530, and 1545 h). Data were analyzed using ANOVA for repeated measures and Tukey's test. During the GXT, there were no changes (P>0.05) in the plasma concentrations of glucose, leptin, adiponectin or ghrelin. However, there was a 29% increase (P<0.05) in mean plasma cortisol concentration and a 35% decrease (P<0.05) in mean plasma insulin concentration. Substantial increases (P<0.05) in the mean plasma concentrations of glucose and cortisol of 36% and 102%, respectively, were seen in the EX trial during the first 60 min post-GXT. Plasma leptin concentration, measured at the 24h post-GXT time point, was 20% lower (P<0.05) during the EX trial compared with the parallel time point in the standing control (CON) trial. Plasma ghrelin concentration was 37% lower (P<0.05) in the EX trial compared with CON before and after the afternoon meal, but was 43% higher (P<0.05) 12h post-GXT. There were no differences between EX and CON for plasma concentrations of insulin or adiponectin during recovery. It was concluded that short-term high intensity exercise alters plasma leptin and ghrelin concentrations in STB mares post-exercise, which may signal the exercised animals to alter energy intake.

Plasma leptin, ghrelin and adiponectin concentrations in young fit racehorses versus mature unfit standardbreds.

Concentrations of hormones related to energy homeostasis may differ between populations with varied body compositions, acting as signals to increase or decrease energy intake and/or expenditure. How these parameters correlate with body composition in horses and how they vary in fit (F) versus unfit (UF) Standardbred racehorses is unclear. The purpose of this study was to test the hypothesis that plasma concentrations of glucose (GLU), insulin (INS), cortisol (CORT), ghrelin (GHRL), adiponectin (ADIP) and leptin (LEP) would be correlated with body composition and differ in fit (F) versus unfit (UF) horses. Fasting plasma samples were taken from 12 unfit (11 +/- 2 years, 521 +/- 77 kg; mean +/- SD) and 34 fit (4 +/- 2 years, 475 +/- 83 kg) Standardbred horses. GHRL, LEP, ADIP, INS and CORT concentrations were measured using radioimmunoassay. GLU concentration was measured using colorometric kits. Body composition data included body weight, body condition score (BCS), and percent fat (%fat) calculated using rump fat thickness measured ultrasonically and the Westervelt equation. Data were analyzed using Pearson Product moment and Student's t tests. There were no differences (P>0.05) between F and UF horses for the plasma concentrations of CORT (69 +/- 14 versus 76 +/- 23 microg/dL), INS (7.2 +/- 3.5 versus 7.1 +/- 1.8 microIU/mL) or GLU (90 +/- 6 versus 86 +/- 7 mg/dL). Plasma GHRL and ADIP concentrations were greater (P<0.05) in F versus UF horses (54 +/- 27 versus 33 +/- 17 pg/mL and 1820 +/- 276 versus 1333 +/- 249 ng/mL, respectively), while plasma LEP was lower in F versus UF (1.0 +/- 0.6 versus 4.4 +/- 2.4 ng/mL, P<0.001). BCS and %fat were lower in F versus UF horses (4.8 +/- 0.3 versus 6.7 +/- 0.5 and 11.9 +/- 1.6 versus 15.4 +/- 2.5%, respectively), with no correlation between %fat and GHRL (-0.12, P>0.05), although there was a positive correlation between %fat and LEP (+0.72, P<0.05), and a negative correlation between %fat and ADIP (-0.40, P<0.05). The data show that in comparing fit and unfit horses, there are variations in body composition as well as concurrent and substantial differences in the concentrations of hormones, cytokines, and other parameters related to the control of appetite and feed intake.