Society for Neuroscience - Contrary to an earlier report, exercising alone appears to be as beneficial for brain health as exercising with others, and that the natural mood-enhancing chemical beta-endorphin may be a key player in the ability of exercise to protect the aging brain.

“Everybody knows that exercise is good for your heart, but in recent years we’ve gathered compelling evidence that exercise is also good for your brain,” says Fred Gage, PhD, of the Salk Institute for Biological Studies. “We now know that exercise helps generate new brain cells, even in the aging brain.”

New research from Brian Christie, PhD, and his colleagues at the University of British Columbia suggests that, contrary to the findings of a study reported earlier this year, exercising alone has the same positive effect on the brain as exercising with others.

“Over the past several years, research has consistently shown that voluntary exercise can markedly enhance the capacity of the hippocampus to create new neurons,” says Christie. “These new cells in the hippocampus appear to be linked to particular types of learning and memory, and it may be that this region of the brain uses new neurons to help ‘time stamp’ the creation of memories.”

Another research group reported last spring that the benefit of exercise on the creation of new neurons did not occur when animals were socially isolated-unless the animals exercised for a much longer period than their non-isolated peers. To further investigate that finding, Christie and his colleagues assigned mice to either single housing or group housing environments. Some of the animals were quasi-randomly given exercise wheels. After 11 days, the brains of all the animals were examined for signs of enhanced cell proliferation.

“Both individually housed and group housed animals that had access to a running wheel showed significantly more cell proliferation than the animals that didn’t exercise,” says Christie. “In fact, they showed about double the amount of new neurons as the sedentary animals. These findings indicate that voluntary exercise has benefits for the brain in both socially isolated and group housed conditions.”

These findings indicate that exercise can have beneficial effects for the brain, irrespective of whether the activity is performed individually or in groups. Current studies are investigating the possible benefits of exercise for helping ameliorate the structural and functional deficits incurred in the hippocampus in an animal model of fetal alcohol syndrome.

An international team of researchers has found that beta-endorphin, a mood-elevating chemical produced by the hypothalamus and the pituitary gland, may be a key factor in the beneficial effects of exercise on the brain.

“We know that exercise creates new neurons in the hippocampus, a brain region involved in learning and memory. This may explain the increased learning and memory performances observed in people who exercise,” says Muriel Koehl, PhD, of the French National Institute for Health and Medical Research (INSERM) at the University of Bordeaux. “But we have a limited understanding of the underlying mechanisms that cause exercise to create those new cells.”

Suspecting that beta-endorphin may play a role in the stimulatory effect of exercise on the creation of new brain cells (a process known as neurogenesis), Koehl and colleagues at Northwestern University and at the University of Groningen in Haren, the Netherlands, set up an experiment that analyzed the consequences of exercise on different components of neurogenesis (cell proliferation, survival, death, and differentiation) in both adult wild-type (normal) mice and beta-endorphin deficient mice (genetically modified mice that are unable to synthesize beta-endorphin).

The researchers found that in wild-type mice, exercise led to a net induction of adult neurogenesis in the hippocampus by increasing the number (proliferation) of newborn cells and the rate at which those cells survived. No surprise there. What did surprise the researchers were the findings from the beta-endorphin deficient mice.

“In those animals that were sedentary, the lack of beta-endorphin had no effect on neurogenesis,” says Koehl. “In those that exercised, however, we saw that the number of newly born cells was not increased. This strongly suggests a role for beta-endorphin in exercise-induced cell proliferation.” “Our study indicates that beta-endorphin released during exercise may be a key factor in promoting the activity’s proliferative-stimulating effect on the brain,” says Koehl.

Other work shows evidence that chronic exercise reduces stroke damage in an animal model.

There is burgeoning evidence that exercise provides a neuroprotective benefit in human brain disease, says Michael Davis, PhD, at the University of Texas Health Science Center. However, the mechanisms and biological underpinnings of this phenomenon remain unclear.

Davis’s hypothesis is that long-term exercise promotes new blood vessel growth. This increase in the brain’s capillary bed elevates cerebral blood flow (CBF) which, in turn, serves to help protect against the extensive damage that normally occurs following stroke.

Davis evaluated the influence of treadmill-exercise and stroke on dynamic changes in rat CBF by imaging the same animal before and after exercise and before, during and after transient or permanent ischemia.

In the unexercised, “couch-potato”, rats the 2-hour stroke produced a 51 percent decrease in CBF. In the exercise group, however, stroke produced only a 16 percent decline in CBF. “This was evidence that exercise provided an approximate 35 percent improvement in brain blood flow subsequent to stroke over that of the control animals,” says Davis. “Our findings support a significant role of exercise in protecting the brain against stroke and perhaps other neurodegenerative disorders, such as Alzheimer’s and Parkinson’s Disease,” he says.

Though these results demonstrate the potential benefit of exercise undertaken before a stroke occurs, adds Davis, no such protection has yet been evidenced for a similar brain benefit of exercise undertaken after a stroke.

This post forms part of a longer story on our iHealthBulletin News page about exercise and the health of the aging brain.