13 Tumor necrosis factor-α gene expression before and after exercise in middle-aged and older horses

Abstract

s / Journal of Equine Veterinary Science 35 (2015) 383e391 388 13 Tumor necrosis factor-a gene expression before and after exercise in middle-aged and older horses M.M. Darby*, S.R. Malone , D.W. Horohov , and D.E. Chappell 1 Morehead State University, Morehead, KY, USA; University of Kentucky, Lexington, KY, USA Tumor necrosis factor-a (TNF-a) is a pro-inflammatory cytokine that is expressed at different levels depending on the age of the horse. Age influences the animal's ability to launch an appropriate immune response and as horses age they exhibit a lower inflammatory response. Twenty-six adult horses (n 1⁄4 8 mares; n 1⁄4 18 geldings) were used to test the hypothesis that older horses would have higher pre-exercise TNF-a values and lower postexercise values than middle-aged horses. Horses were used in a University riding program andwere ridden for approximately one hour undergoing exercise of varying intensity. Blood samples (~4 mL) were collected via venipuncture into PAXgene tubes before exercise (pre) and 3 h after exercise (post). Blood samples were analyzed using real-time polymerase chain reaction (PCR) with equine-specific primers. Statistical significance was set at P < 0.05 and analysis was done using an ANOVA. Horses were split into age groups, middle-aged (<15 years; n 1⁄4 13; mean age 10 years; range 7e14 years) and older (1⁄4 15 years; n 1⁄4 13; mean age 17.6 years; range 15e21 years). The results are displayed as the mean ± SEM. Older horses had similar (P 1⁄4 0.24) pre-exercise TNF-a mRNA expression as middle-aged horses (middle-aged 0.075 ± 0.06; older 0.18 ± 0.07). Post-exercise there was no significant difference (P 1⁄4 0.119) between groups for TNF-a mRNA expression (middle aged 0.32 ± 0.08; older 0.14 ± 0.07). The magnitude of the response to exercise was similar in both groups of horses. Older horses had slightly, but not significantly, higher TNF-a mRNA expression pre-exercise and this could be expected due to chronic inflammation or underlying conditions. Future studies may focus on a more diverse age population with a wider gap betweenmiddle-aged and older horses andmore control over underlying medical conditions.