M. E. Gordon

Effect of orange peel and black tea extracts on markers of performance and cytokine markers of inflammation in horses

This study tested the hypothesis that orange peel (O) and decaffeinated black tea (T) extracts would alter markers of exercise performance as well as exercise-induced mRNA expression for the inflammatory cytokines IL-6, TNFalpha and IFN-gamma. Nine healthy, unfit Standardbred mares (age: 10 ^ 4years, ,450kg) were assigned to three treatment groups in a randomized crossover design where each horse was administered one of the following; placebo (O; 2l water), black tea extract in water (T; 2l) or orange peel extract in water (W; 2l), via a nasogastric tube. One hour later the horses completed an incremental graded exercise test (GXT) on a treadmill at a fixed 6% grade with measurements and blood samples obtained at rest, at the end of each 1min step of the GXT and at 2 and 5min post-GXT. An additional set of blood samples for Polymerase Chain Reaction (PCR) measurements of mRNA was obtained before exercise and at 5 and 30min and 1, 2, 4 and 24h post-GXT. The GXTs were conducted between 0700 and 1200h not less than 7days apart. There were no differences (P . 0.05) in VO2max, respiratory exchange ratio, run time, velocity at VO2max, core body temperature, haematocrit, creatine kinase (CK), plasma lactate concentrations, HR, right ventricular pressure (RVP) or pulmonary artery pressure (PAP) across treatments. A major finding was that orange peel extract significantly reduced post-exercise VO2 recovery time (W ¼ 112 ^ 7, O ¼ 86 ^ 6, and T ¼ 120 ^ 11s). There was a significant difference in plasma total protein concentration (TP) in the O runs compared with water and T. TNF-alpha mRNA expression was lower in the T runs compared with water and O trials. IFN-gamma mRNA expression levels appeared to be lower in both the Tand O extract runs compared with the water trials. The mRNA expression of IL-6 was unaltered across treatment groups. These data suggest that orange peel and black tea extracts may modulate the cytokine responses to intense exercise. Orange peel extract reduced post-exercise recovery time and may potentially enhance the ability of horses to perform subsequent bouts of high-intensity exercise.

Developmental changes in the concentrations of glutamine and other amino acids in plasma and skeletal muscle of the Standardbred foal

Glutamine is concentrated within skeletal muscle, where it has been proposed to play a regulatory role in maintaining protein homeostasis. The work presented here addressed the hypothesis that glutamine would be the most abundant free alpha-AA in plasma and skeletal muscle in the foal during the first year of life. Glycine, however, was the most abundant free alpha-AA in plasma at birth and between 3 and 12 mo of age. The concentration of glutamine, the second most abundant AA at birth, increased through the first 7 d (P < 0.05) and then returned to values similar to those at birth. This resulted in glutamine being the most abundant free alpha-AA in plasma from 1 d through 1 mo of age. The most abundant free alpha-AA in skeletal muscle at birth was glutamine, but the concentration fell by more than 50% by d 15 and continued to decrease, reaching about one-third of the original values by 1 yr of age (P < 0.05). Glutamine synthetase was barely detectable in skeletal muscle at birth, but the abundance increased rapidly within 15 d of birth. The concentration of glycine, the second most abundant alpha AA in muscle at birth, decreased by about 40% by d 15 (P < 0.05) and then stabilized at this value throughout the year. In contrast, glutamate, alanine, and serine concentrations, the third, fourth, and fifth most abundant free alpha-AA in muscle at birth, respectively, increased to new stable concentrations between 3 and 6 mo of age (P < 0.05). This resulted in alanine being the most abundant free alpha-AA in skeletal muscle at 12 mo of age, followed by glutamate, glutamine, and glycine. The decrease in intramuscular glutamine content, particularly during the first 2 wk after birth, is not compatible with a regulatory role for glutamine in muscle protein synthesis because it occurred at the time of maximum growth in these animals. The findings that, at certain times of development, glutamine was not the most abundant free alpha-AA in the foal is novel and signifies that intramuscular glutamine may have functions specific to muscle type and mammalian species.

Exercise training, Glut-4 protein abundance and glutamine in skeletal muscle of mature and very old horses

Two groups of unfit Standardbred mares (adult: 9-14 years, 540 kg, n=7) and old (20-25 years, 530 kg, n=5) were used to test two hypotheses, first, that aging and training would alter plasma and muscle glutamine [Gln] and glutamate [Glu] and second, that aging and training would alter Glut-4 expression in skeletal muscle. All animals were housed on pasture with free access to grass and all received hay and supplementation with a commercially prepared supplement (15% crude protein and 3.00 Mcal/kg dry matter) in individual stalls. Mares were fed to meet or exceed NRC (2007) nutrient recommendations for moderate to heavy exercise. The mares were exercise trained in a free-stall motorised circular exercise machine for 30 min/d, 5 d/week, for 8 weeks. Work intensity during training was set at a relative intensity of ~60% of the maximum heart rate, previously determined during an incremental exercise test (GXT). Blood samples and muscle biopsies (gluteus) obtained before and after 8 weeks of training were used...

Effects of exogenous ghrelin infusion on feed intake and metabolic parameters of energy homeostasis in Standardbred mares

Six Standardbred mares (age 12±2 years, body weight 502±63 kg; mean ± standard deviation) were given 1.6 µg/kg acylated human ghrelin or vehicle treatment as an intravenous bolus in a randomised, cross-over design to test the hypothesis that exogenous ghrelin infusion would increase feed intake and alter metabolic parameters of energy homeostasis, leptin, glucose, insulin and cortisol. After the horses had initial access to hay cubes for 1.5 h, doses were given and hay cubes were available once again. Leftover feed was weighed 6 times over each of the 24 h testing periods. Blood samples for measurement of active ghrelin, growth hormone, leptin, glucose, insulin and cortisol were taken at time 0 (immediately before infusion) and 20, 40, 60, 80, 100, 120, 240, 480, and 720 min post-infusion. Every 10 min, the horses’ behaviour was recorded for eating, drinking, resting, and other behaviours. Ghrelin infusion did not increase (P≯0.05) feed intake in the mares as a group, but did increase feed intake (P<0.04)...