Exercise: A Neurostructural Remodeling Perspective

Abstract

Exercise is accepted as a positive health behaviour. However, the mechanisms that underlie the beneficial effects of exercise are still being elucidated, particularly with respect to cognitive health. Chronic exercise can decrease neuroinflammation and increase neuroplasticity. However, exercise is also a metabolic stressor that can transiently upregulate systemic inflammation, while less is known about neuroinflammatory changes with acute exercise. Some forms of neuroinflammation may be beneficial in promoting neurostructural remodeling. Accordingly, the purpose of this study was to elucidate the inflammatory and neuroplastic, and behavioural changes (open field, novel object recognition, novel object location) from acute and chronic exercise in young healthy male and female mice. In the first phase of the study, mice were placed on a treadmill for two-hours at a speed of 15 m/min and a 5% incline, followed by euthanasia 2-hours post exercise. In the second phase of the study, a separate cohort of mice underwent the same exercise paradigm and underwent behavioural testing 2-hours post exercise. In the third phase of the study, another cohort of mice underwent an 8-week treadmill exercise paradigm followed by behavioural testing. Biological endpoints included cytokine measurement and western blot analysis of aggrecan and matrix metalloprotinase-9. In males, acute exercise decreased time spent in the centre of the open field, consistent with increased anxiety-like behaviour. However, this effect was not observed in the exercised females. Regardless of sex, chronic exercise increased the number of entries made into the centre of the open field, consistent with decreased anxiety-like behaviour. There were no exercise or sex dependent differences in object location or object recognition memory. Acute exercise increased IL-6 and decreased TNF in the serum and had minimal effects on various regions of the brain. Conversely, chronic exercise increased IL-6 in the prefrontal cortex and decreased TNF in the dorsal hippocampus and had minimal effects on cytokine levels in the blood. Chronic exercise reduced aggrecan in the dorsal hippocampus and acute exercise produced a similar near significant trend. These results demonstrate the differential effects of acute and chronic exercise on anxiety and inflammation despite similar effects on neuroplasticity.