How exercise may protect against Alzheimer's
Previous research uncovered a hormone called irisin that is released into the circulation during physical activity, and appeared to play a role in energy metabolism. Mice studies have now found that irisin protected memory and synapses in the brain — disabling irisin in the hippocampus resulted in synapses and memory weakening; boosting brain levels of irisin improved synapses and memory.
Mice who swam nearly every day for five weeks didn’t develop memory impairment despite getting infusions of beta amyloid — however, blocking irisin completely eliminated the benefits of swimming.
Samples from brain banks have confirmed that irisin is present in the human hippocampus and that hippocampal levels of the hormone are reduced in those with Alzheimer's.
Short bouts of exercise prime the brain for learning
A mouse study found that short-term bursts of exercise (equivalent to a game of pickup basketball, or 4,000 steps) activated a gene (Mtss1L) that promotes an increase in synapses in the hippocampus — which primes the brain for learning.
Lourenco, M. V., Frozza, R. L., de Freitas, G. B., Zhang, H., Kincheski, G. C., Ribeiro, F. C., … De Felice, F. G. (2019). Exercise-linked FNDC5/irisin rescues synaptic plasticity and memory defects in Alzheimer’s models. Nature Medicine, 25(1), 165–175. https://doi.org/10.1038/s41591-018-0275-4
Chatzi, C., Zhang, Y., Hendricks, W. D., Chen, Y., Schnell, E., Goodman, R. H., & Westbrook, G. L. (2019). Exercise-induced enhancement of synaptic function triggered by the inverse BAR protein, Mtss1L. ELife, 8, e45920. https://doi.org/10.7554/eLife.45920