Professor Equine Internal Medicine University College Dublin Dublin, Dublin, Ireland
Abstract:
Background: Exercise positively impacts on brain health. Exercise-induced peripheral humoral factors (exerkines) are believed to mediate some of the effects due to ‘muscle-brain crosstalk’. Cathepsin B (CTSB) is a muscle-derived exerkine capable of crossing the blood-brain barrier. In humans peripheral CTSB is associated with improved cognitive function. Most report CTSB to increase after exercise and training, although some found no change or a decrease in CTSB after training. This has not been investigated in horses. Hypothesis: Peripheral CTSB increases following exercise and training in horses. Animals: Privately-owned 2-year-old Thoroughbred racehorses (n=17) from one yard.
Methods: A prospective cohort study was performed. Horses were instrumented with an ECG-GPS device. Venous blood was collected before (T0), 5 (T1) and 30 minutes (T2) after high intensity ridden exercise on an all-weather gallop; 10/17 horses had repeat samples taken after 6-8 weeks of training. Plasma samples were measured neat in triplicate using a Horse CTSB quantitative sandwich ELISA.
Results: Peak heart rate, velocity and distance were not different during the tests before and after training. Intra- and inter-assay coefficient of variations were 10% and 15%. Pre-training T1 (3.99±2.1pg/ml) and T2 (3.5±1.6pg/ml) CTSB concentrations were greater than T0 (3.1±1.4pg/ml; p=0.03, repeated measures ANOVA). After training, CTSB concentrations at T0 (2.8±1.1pg/ml), T1 (3.2±1.5pg/ml) and T2 (3.0±1.5pg/ml) were significantly lower than pre-training values (p=0.05, repeated measures ANOVA). Conclusions and Clinical Importance: Plasma CTSB concentrations increase following exercise in horses but decrease following training. Additional research is required to understand how CTSB may interact with other neurotrophic factors.
