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The same system that regulates blood pressure may also play a role in aging, according to studies presented November 22 at the annual meeting of the Gerontological Society of America in Washington D.C.
Researchers at Wake Forest University Baptist Medical Center conducted separate studies regarding the renin-angiotensin system, which helps regulate blood pressure, and found that it is important in body composition and how the body responds to exercise.
Researcher Stephen Kritchevsky, Ph.D., professor of gerontology, said the findings suggest that a whole new mechanism might be involved in aging. “It offers new opportunities to explore treatments to help older adults maintain their function,” he added.
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 slow high blood pressure.
“It’s becoming apparent that this system is involved in more than just blood pressure,” said Kritchevsky.
In a study on mobility and ACE, researchers found that a common variant of the gene that controls ACE production can be inherited in three different combinations. The researchers investigated how the variant affects response to exercise in more than 3,000 well-functioning adults between the ages of 70 to 79. Half of the group was active, burning more than 1,000 calories a week in exercise; the other half was inactive.
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.
In another study on strength and ACE, the physical function of 211 obese, sedentary adults who were 60 years and older was assessed before and after 18 months of exercise. Before exercise began, no association was found between the particular combination of the ACE gene variant and participants’ knee strength, ability to walk 6 minutes or level of body fat.
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.
In a study on ACE and body composition, researchers tested a previous finding that ACE inhibition might improve body composition and physical performance. Using older rats, Christy Carter, Ph.D., assistant professor of gerontology, treated half of the animals with a blood pressure drug that inhibits ACE production. The other half got an inactive treatment. After six months, the animals that got the inactive treatment had greater declines in strength and physical performance. The animals treated with ACE inhibitors had lower body weight, despite the fact that the two groups had equal food intake.
“ACE inhibition may prevent age-related decline in physical performance, perhaps through a reduction in total fat mass,” said Carter.
Source:
Medical Week staff,
week of November 27, 2004
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