November 21 (HealthDay News) -- In experiments in mice, exercise appears to reverse the decline in the production of brain stem cells usually seen with aging, Taiwanese researchers report.

This remarkable restoration of the brain's ability to stave off aging appears to be due to exercise's ability to restore a neurochemical that is essential for the production of new brain cells.

"As we age, the ability of producing new neurons is decreasing. However, moderate running can improve the production, survival and maturation of new neurons in the brain," said lead researcher Yu-Min Kuo, an associate professor in the Department of Cell Biology and Anatomy at the National Cheng Kung University Medical College in Tainan. "The younger one starts to run, the better."

The report is published in the November issue of the Journal of Applied Physiology.

For the study, Kuo's team trained young, adult, middle-aged and old mice to run on a treadmill for up to an hour a day. The researchers then looked at the ability of the brain to continue to produce neural cells.

In middle-aged mice, the number of neural progenitor and mitotic cells in the hippocampus, a brain region intimately associated with learning and memory, decreased dramatically, Kuo explained.

"Compared to the sedentary middle-aged mice, moderate treadmill running not only doubled the production of neural stem cells but also enhanced the survival and growth of the newborn neurons," Kuo said. "Running had a more pronounced effect on younger animals than older counterparts."

The researchers found that this phenomenon could not be explained by an increase in a hormone called corticosterone, as they had speculated.

Rather, moderate running increased the concentrations of brain-derived neuron growth factor and its receptor, TrkB, in the hippocampus, while the level of corticosterone in mice stayed constant, Kuo said.

"The production of neural stem cells in the hippocampus decreases dramatically by middle age, and moderate running exercise can slow this trend," Kuo said. "Chronic moderate running enhances the production of neurotrophic factor, which promotes neurogenesis, and the differentiation and survival of newborn neurons."

Paul Sanberg, director of the University of South Florida Center for Aging and Brain Repair, concurs that exercise could promote the growth of new brain stem cells in people.

"This provides more understanding of its potential in humans," Sanberg said. "That there is a significant effect in middle-aged animals suggests that in middle-aged people that this would also occur."

There needs to be more data in humans to see if the growth of new brain cells has an effect on cognitive ability, Sanberg noted. "But it's encouraging the continued use of exercise to maintain health and proper health of our brain," he said.

SOURCES: Yu-Min Kuo, Ph.D., associate professor, department of cell biology and anatomy, National Cheng Kung University Medical College, Tainan, Taiwan; Paul Sanberg, Ph.D., D.Sc., professor, neurosurgery, and director, University of South Florida Center for Aging and Brain Repair, Tampa; November 2008 Journal of Applied Physiology