Itís known that ageing sensitizes (i.e. causes to become more reactive) microglia (a type of glial cells that reside on the central nervous system and are involved in immunological protection of the brain; though in abnormal situations, are known to contribute to the development of autoimmune disorders such as Alzheimerís and Parkinsonís diseases). The result of this is that when a bacterial infection strikes, microglia of the aged subject overreact by signalling exaggerated inflammatory responses. This can result in a reduction of brain-derived neurotrophic factor (BDNF, a growth factor essential for the survival of certain neurons in the brain).
Ruth Barrientos and her colleges from the Department of Psychology and Neuroscience, University of Colorado at Boulder, had conducted a study based on the findings of previous experiments which had shown that physical exercise can cause an increase in brain-derived neurotrophic factor (BDNF) mRNA (mRNA is an intermediate molecule between DNA, which is the genetic code, and the expression of proteins; so increased mRNA usually means increased protein) in the hippocampus (a region of the brain involved in many cognitive functions and in many diseases). They hypothesised that since exercise increases BDFN levels, it could also be functioning at an earlier stage of the chain to prevent the exaggerated neuroinflammatory responses seen in aged subjects.
They run an experiment with aged rats, infected with E. Coli, which were allowed to voluntarily exercise. The results showed that indeed exercise protected them against infection-induced sensitization of microglia, exaggerated neuroinflammatory responses, and decreases of BDNF levels. As a result, exercising rats showed less infection-induced long-term memory impairments than sedentary controls.
Their findings add further evidence that exercise can exert a neuroprotective effect in ageing subjects, and can prevent age-related, infection-induced memory loss.
Their findings were published in The Journal of Neuroscience, 10 August 2011.