Horses have one of the highest skeletal muscle oxidative capacities amongst mammals, which, combined with a high glycolytic capacity, could perturb redox status during maximal exercise. We determined the effect of 30 d of oral coenzyme Q10 and N-acetyl-cysteine supplementation (NACQ) on muscle glutathione (GSH), cysteine, ROS, and coenzyme Q10 concentrations, and the muscle proteome, in seven maximally exercising Thoroughbred horses using a placebo and randomized cross-over design. Gluteal muscle biopsies were obtained the day before and 1 h after maximal exercise. Concentrations of GSH, cysteine, coenzyme Q10, and ROS were measured, and citrate synthase, glutathione peroxidase, and superoxide dismutase activities analyzed. GSH increased significantly 1 h post-exercise in the NACQ group (p = 0.022), whereas other antioxidant concentrations/activities were unchanged. TMT proteomic analysis revealed 40 differentially expressed proteins with NACQ out of 387 identified, including upregulation of 13 mitochondrial proteins (TCA cycle and NADPH production), 4 Z-disc proteins, and down regulation of 9 glycolytic proteins. NACQ supplementation significantly impacted muscle redox capacity after intense exercise by enhancing muscle glutathione concentrations and increasing expression of proteins involved in the uptake of glutathione into mitochondria and the NAPDH-associated reduction of oxidized glutathione, without any evident detrimental effects on performance.

Horses have a slow rate of muscle glycogen repletion relative to other species for unknown reasons. Our aim was to determine the expression of glucose transporters (GLUT) and genes impacting GLUT4 expression and translocation in the gluteal muscle. Five fit Thoroughbred horses performed glycogen-depleting exercises on high-starch (HS, 2869 g starch/day) and low-starch, high-fat diets (LS-HF, 358 g starch/d) with gluteal muscle biopsies obtained before and after depletion and during repletion. Muscle glycogen declined by ≈30% on both diets with little increase during repletion on LS-HF. Transcriptomic analysis identified differential expression (DE) of only 2/12 genes impacting GLUT4 translocation (two subunits of AMP protein kinase) and only at depletion on LS-HF. Only 1/13 genes encoding proteins that promote GLUT4 transcription had increased DE (PPARGC1A at depletion LS-HF). GLUT4 comprised ≈30% of total GLUT mRNA expression at rest. Remarkably, by 72 h of repletion expression of GLUT3, GLUT6 and GLUT10 increased to ≈25% of total GLUT mRNA. Expression of GLUT6 and GLUT10 lagged from 24 h of repletion on HS to 72 h on LS-HF. Lacking an increase in GLUT4 gene expression in response to glycogen-depleting exercise, equine muscle increases GLUT3, GLUT6 and GLUT10 expression potentially to enhance glucose transport, resembling responses observed in resistance trained GLUT4-null mice.

OBJECTIVE: To assess the relationship between plasma and RBC fatty acid composition and incidence and severity of squamous gastric ulcers when altered by short-chain (SC) or long-chain (LC) polyunsaturated fatty acid (PUFA) supplementation. ANIMALS: 13 fit Thoroughbred horses in training. PROCEDURES: Horses were evaluated by gastroscopy for squamous ulcer score, gastric pH, and blood fatty acid composition prior to supplementation (UNSUPP) and after 3 months of supplementation with a corn-flax oil blend of alpha-linolenic acid and linoleic acid (SC-PUFA) or a gamma-linolenic acid (GLA)-fish oil blend of GLA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA; LC-PUFA) in a crossover design. Prior to gastroscopy and blood collection, horses performed a 4,600-m standardized exercise test on the racetrack as a stressor. RESULTS: Three months of supplementation with LC-PUFAs increased RBC levels of GLA, dihomo-gamma-linolenic acid (DGLA), arachidonic acid (AA), EPA, and DHA, and reduced severe ulcer prevalence (38% UNSUPP vs 8% LC-PUFA with a severe ulcer score of grade 3 to 4). Short-chain PUFA supplementation did not effectively elevate RBC GLA, DGLA, AA, EPA, or DHA and severe ulcer incidence was not different (38% UNSUPP vs 23% SC-PUFA with a severe ulcer score of grade 3 to 4). Lower levels of RBC GLA, DGLA, AA, and EPA correlated with severe squamous gastric ulceration (grade 3 to 4). CLINICAL RELEVANCE: Equine gastric ulcer syndrome is prevalent in high-performance horses and is a concern to owners and trainers. Long-chain PUFA supplementation increased levels of GLA, DGLA, AA, EPA, and DHA, unlike SC-PUFA supplementation, and was associated positively with prevention or resolution of severe squamous gastric ulceration. Further studies are needed to evaluate different management styles and exercise intensities.

Coenzyme Q10 (CoQ10) is an essential component of the mitochondrial electron transfer system and a potent antioxidant. The impact of CoQ10 supplementation on mitochondrial capacities and the muscle proteome is largely unknown. This study determined the effect of CoQ10 supplementation on muscle CoQ10 concentrations, antioxidant balance, the proteome, and mitochondrial respiratory capacities. In a randomized cross-over design, six Thoroughbred horses received 1600 mg/d CoQ10 or no supplement (control) for 30-d periods separated by a 60-d washout. Muscle samples were taken at the end of each period. Muscle CoQ10 and glutathione (GSH) concentrations were determined using mass spectrometry, antioxidant activities by fluorometry, mitochondrial enzyme activities and oxidative stress by colorimetry, and mitochondrial respiratory capacities by high-resolution respirometry. Data were analyzed using mixed linear models with period, supplementation, and period × supplementation as fixed effects and horse as a repeated effect. Proteomics was performed by tandem mass tag 11-plex analysis and permutation testing with FDR < 0.05. Concentrations of muscle CoQ10 (p = 0.07), GSH (p = 0.75), and malondialdehyde (p = 0.47), as well as activities of superoxide dismutase (p = 0.16) and catalase (p = 0.66), did not differ, whereas glutathione peroxidase activity (p = 0.003) was lower when horses received CoQ10 compared to no supplement. Intrinsic (relative to citrate synthase activity) electron transfer capacity with complex II (E_CII) was greater, and the contribution of complex I to maximal electron transfer capacity (FCR_PCI and FCR_PCIG) was lower when horses received CoQ10 with no impact of CoQ10 on mitochondrial volume density. Decreased expression of subunits in complexes I, III, and IV, as well as tricarboxylic acid cycle (TCA) enzymes, was noted in proteomics when horses received CoQ10. We conclude that with CoQ10 supplementation, decreased expression of TCA cycle enzymes that produce NADH and complex I subunits, which utilize NADH together with enhanced electron transfer capacity via complex II, supports an enhanced reliance on substrates supplying complex II during mitochondrial respiration.