Abstract 15640: Long Term Moderate, but Not Intense, Exercise Improves Cognitive Brain Health. Study in a Rat Model

Introduction: A U-shaped relationship between exercise load and cardiovascular risk has been demonstrated. In the brain, moderate exercise improves cognitive performance but the consequences of intense exercise remain unknown. We aimed to describe the effects of moderate and intensive exercise load on brain structure and function. Methods: Male Wistar rats were subjected to moderate (MOD, 35 cm/s for 45 min, n=8) or intense (INT, 60 cm/s for 60 min, n=8) exercise for 16 weeks, 5 days/week; sedentary rats (SED, n=10) were used as controls. At 16 weeks, learning and motivation tests, and brain magnetic resonance (MR) were obtained. In MR, structural brain networks were analyzed using fractional anisotropy normalized connectomes, and cerebral blood flow (CBF) was assessed using pulsed arterial spin labelling. BDNF levels were analysed in plasma, hippocampus and frontal cortex samples with ELISA. Results: MOD rats showed a greater motivation than SED rats and enhanced learning capacity than INT rats. In the MR, only moderate exercise increased global and local efficiency and average clustering coefficient. Global CBF was increased by moderate but not intensive exercise (Fig A). CBF was subsequently assessed at specific brain regions. In comparison to SED, MOD rats presented a higher CBF in the right and left cortex, and in the left hippocampus; in INT rats, CBF was higher only in the left cortex compared to SED (Fig B). MOD training induced a significant decrease in BDNF protein levels in the hippocampus compared to both SED and INT groups. No significant differences were found on BDNF levels in plasma and frontal cortex samples among groups. Conclusions: In a rat model, moderate exercise induces brain structural and functional improvements that are not perpetuated with intensive exercise, supporting the existence of a U-shaped relationship between exercise load and brain function.