242
Effect of Weight Loss on Markers of Oxidant Status in the Mature Horse
Obesity causes an increase in inflammation and the production of reactive oxygen species (ROS) in human and rodent models but this has not been assessed in the horse. Weight loss is considered to improve oxidant status but a stepwise evaluation of the effect of weight loss has yet to be completed. We hypothesized that horses transitioning from an obese (7-8) to a moderate (5) body condition score (BCS) would show improvements in oxidant status. An obese BCS was maintained for a period of two weeks in eight light-type horses of mature age (5-19 years) and mixed sex for baseline sampling, then placed on a weight loss plan of a 30% caloric restriction and light exercise, with sampling every other week. The oxidant status of each horse was determined by analysis of erythrocyte lysate for total glutathione (GSH) concentration and glutathione peroxidase (GPx) activity, which work together to scavenge ROS. Nitric oxide (NO), a readily degrading free radical linked to oxidative damage due to interactions with superoxide radicals, was also evaluated in plasma via measurement of nitrate, an inert end product of NO degradation. Data were analyzed by ANOVA with repeated measures, testing for the effect of change in BCS and percent weight loss, with gender and age as covariate s. GSH concentrations tended to be increased by change in BCS (p=0.07) but not percent weight loss. GPx activity, however, was not altered. GSH concentration was negatively correlated (r=-0.23, p=0.05) with GPx activity. Plasma nitrate tended to be decreased in response to both change in BCS (p=0.06) and percent weight loss (p=0.08). Therefore, we did observe improvements in oxidant status (ie. increased GSH and decreased nitrate) as horses lost weight but the small magnitude of the changes indicated that, while obese, the horses may not have been experiencing increased inflammation and ROS production.
Keywords: Obesity, oxidant status, horse