Aerobic exercise and Orexin A: role of sympathetic activity and redox system

Aerobic exercise is associated with the sympathetic activation evoking adaptive responses to sustain muscle engagement. Physical exercise can cause alterations in the cardiovascular activity and cellular stress may occur which could be marked by either heart rate (HR), or galvanic skin response (GSR). Moderate plasma levels of reactive oxygen species (ROS) are considered as health markers, absolving to important roles such as adaptive cellular responses to exercise. Orexin A, a hypothalamic peptide, causes a widespread stimulation of the sympathetic nervous system, playing a role in many physiological functions. The aim of this study was to analyze the effects of aerobic exercise on Orexin A plasma levels, evaluating the possible association with physical exercise and oxidative stress, both involved in the sympathetic and thermogenic reactivities. Three blood samples were collected at various periods of time from all participants (25 males with mean age of 23.4±2.1 years): resting time (0 min), exercise time (at the start and at end of exercise) and recovery time (30-45 min after training). At the same interval times, heart rate (HR), galvanic skin response (GSR), rectal temperature, and d-ROMs test were monitored. Exercise induced a significant increase in the following parameters: HR (p < 0.01); GSR (p < 0.05); rectal temperature (p < 0.01); and plasma Orexin A (p < 0.01). No significant increase of the d-ROMs values were found. The results of this study confirmed that physical activity is associated with the sympathetic activation, as demonstrated by HR and GSR increases after training. Changes in the Orexin A plasma levels reveal the presence of hormonal adaptations in response to exercise, indicating that this peptide might be involved in cardiovascular regulation. Further studies could confirm the multitasking role of this neuropeptide