Four separate studies point to the renin-angiotensin system, which helps regulate blood pressure, as also being important in body composition, mental function and how the body responds to exercise. The work, presented today in Washington, D.C., at the 57th Annual Scientific Meeting of the Gerontological Society of America.
"This is exciting because it suggests that a whole new mechanism might be involved in aging," said Stephen Kritchevsky, Ph.D., professor of gerontology. "It offers new opportunities to explore treatments to help older adults maintain their function."
A primary component of the renin-angiotensin system is ACE, or angiotensin converting enzyme, which converts angiotensin I, an inactive protein in the blood, to angiotensin II, a protein that constricts blood vessels. Angiotensin II is balanced by another hormone that is believed to "brake" high blood pressure.
"It's becoming apparent that this system is involved in more than just blood pressure," said Kritchevsky.
The Wake Forest Baptist research is the first to show that the system may be associated with physical function in older adults. The projects are:
All exercisers had better mobility than non-exercisers, but exercisers who had the gene combination associated with the lowest ACE production were 47 percent more likely to become limited in their mobility than exercisers with the combination associated with the highest ACE production. Kritchevsky, who led the study, said ACE production was associated with how well activity helped preserve function.
At the end of the program, however, participants with the combination associated with highest ACE production showed a 75 percent improvement in knee strength - compared to a 23 percent improvement in participants who had the combination associated with lowest ACE production. There were no differences in walking distance between the two groups.
"Changes in muscle strength with exercise training in older individuals may be dependent on ACE genotype," said Barbara Nicklas, Ph.D., associate professor of gerontology, who led the study.
Kritchevsky said researchers don't yet understand how ACE levels affect physical and mental function. He said knowing more about the biochemical pathways of ACE may help explain two additional studies - in animals - with seemingly contradictory results.
"The results pose a bit of a puzzle, but underscore the need to learn more about how this system influences human health," he said. The animal studies were:
"ACE inhibition may prevent age-related decline in physical performance, perhaps through a reduction in total fat mass," said Carter.
In rats, Robbins tested a blood pressure medication that blocks the effects of angiotensin II. Early results show that the drug has the potential to combat oxidative stress - and reduce cognitive impairment.
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