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New research published in the journal Aging Cell provided insights into how exercise may help to prevent or slow cognitive decline during aging. Aging induces progressive physiological changes to multiple body systems over time. In humans, aging is associated with a decline in both general physical well-being and cognitive abilities. Observational studies in aged individuals consistently suggest that exercise can alleviate age-related deficits in multiple physiological systems, including the brain. Exercise can reverse grey matter loss in the hippocampus, an area important for learning and memory. While the mechanisms underlying these benefits remain poorly defined, exercise in general is known to increase neurotrophin expression, enhance synaptic plasticity, and modulate the expression of various immune factors in the aged brain. It also modulates the heightened aging-associated response of microglia to immune challenges. For the study, investigators assessed the expression of genes in individual cells in the brains of mice. The team found that exercise has a significant impact on gene expression in microglia, the immune cells of the central nervous system that support brain function. Specifically, the group found that exercise reverts the gene expression patterns of aged microglia to patterns seen in young microglia. Treatments that depleted microglia revealed that these cells are required for the stimulatory effects of exercise on the formation of new neurons in the brain's hippocampus, a region involved in memory, learning, and emotion. The scientists also found that allowing mice access to a running wheel prevented and reduced the presence of T cells in the hippocampus during aging. These immune cells are not typically found in the brain during youth, but they increase with age. "We were both surprised and excited about the extent to which physical activity rejuvenates and transforms the composition of immune cells within the brain, in particular how it was able to reverse the negative impacts of aging. It highlights the importance of normalizing and facilitating access to tailored exercise programs. Our findings should help different industries to design interventions for elderly individuals who are looking to maintain or improve both their physical and mental capabilities," said co-corresponding author Jana Vukovic of The University of Queensland, in Australia. Reference: Solal Chauquet, Emily F. Willis, Laura Grice, Samuel B. R. Harley, Joseph E. Powell, Naomi R. Wray, Quan Nguyen, Marc J. Ruitenberg, Sonia Shah, Jana Vukovic; Exercise rejuvenates microglia and reverses T cell accumulation in the aged female mouse brain; Aging Cell; https://doi.org/10.1111/acel.14172