The effect of treadmill exercise on memory function and gut microbiota composition in old rats.

Aging is associated with declines in memory function and significant change in gut microbiota. In this study, we investigated how exercise affects age-related memory decline and inflammation, and gut microbiota diversity. Bl6 mice were divided into control, control and exercise, old, and old and exercise groups. Treadmill exercise was performed once a day, 5 days a week for 8 consecutive weeks. Short-term memory was assessed using step-through test and spatial learning memory was assessed using Morris water maze task. Enzyme-linked immunosorbent assay was performed for the proinflammatory cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-6, in the hippocampus. Western blot analysis was conducted for the neurotrophic factors, brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB), in the hippocampus. In addition, fecal samples were collected for sequencing and metagenomic analysis. Old rats showed decline in short-term memory and spatial learning memory. Increment of TNF-α and IL-6 concentration with decrement of BDNF and TrkB expression were observed in the old rats. Decreased diversity of gut microbiota composition and decreased beneficial gut microbiota were found in the old rats. However, treadmill exercise improved short-term memory, decreased TNF-α and IL-6 concentration, and increased BDNF and TrkB expression in the old rats. Treadmill exercise also increased the diversity of gut microbiota composition and affected the increase of beneficial gut microbiota in the old rats. In conclusion, treadmill exercise reduced age-related inflammatory markers and effectively improved memory decline while enhancing the diversity and abundance of beneficial gut microbiota.