Abstract
Reactive oxygen species are normal by-products of cellular metabolism but may have detrimental effects on cellular matrices and excite inflammatory pathways when overproduced. To test the hypothesis that supplementation of an herbal extract combination would: 1) improve antioxidant status; 2) increase anti-inflammatory cytokines; and 3) decrease pro-inflammatory cytokines, 40 mature, sedentary stock-type horses (32 mares, 8 geldings, mean±SD; 15.7 ± 4.9 yr, 519 ± 46 kg) were stratified by age, sex, and body weight and randomly assigned to one of four dietary treatment groups for 56 d: 1) 0 mg (CON); 2) 675 mg (Pro1); 3) 2,025 mg (Pro3); or 4) 4,050 mg (Pro6) Protandim Nrf2 Synergizer (LifeVantage Corporation) per day (n = 10/group). Horses were group housed and received a basal diet of mixed warm-season grass pasture and hay ad libitum and a custom-formulated concentrate grain. Blood collected prior to the morning feeding on day 0, 28, and 56 was analyzed for hydrogen peroxide (H2O2) production and concentration, superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activities, concentrations of malondialdehyde (MDA), cytokines [interleukin (IL)-4, IL -6, IL -8, IL -10 and tumor necrosis factor α], and caffeine, and mRNA expression of IL -1β, Nrf2, and HMOX1. Activities of GPx and SOD were also quantified in gluteus medius samples collected at day 0 and 56. Data were analyzed using linear models in SAS v9.4; sex, time, treatment, and time×treatment were fixed effects and time was a repeated effect with horse(treatment) as the subject. Plasma caffeine concentrations increased from day 0 to 56 in supplemented horses (P ≤ 0.05) in a dose-dependent fashion but did not change in CON horses, resulting in Pro6 horses having the greatest concentration of caffeine at day 56, followed by Pro3, Pro1, then CON horses. No other measure was impacted by treatment though whole blood H2O2 production, SOD activity, and IL -1β mRNA, and plasma IL -8 and MDA concentrations decreased by day 28 (P ≤0.006), whole blood Nrf2 mRNA and IL -10 concentrations decreased by day 56 (P≤0.04), and skeletal muscle GPx activity increased by day 56 (P = 0.05) in all horses. Dietary supplementation of up to 4,050 mg/d Protandim Nrf2 Synergizer did not impact antioxidant status or plasma cytokines in mature, sedentary horses. Effects of supplementation on these variables should be investigated in horses subjected to elevated oxidative and/or inflammatory insult, such as during exercise or aging.