<![CDATA[Fountain of youth? Look no farther than your feet]]>

“We have previously demonstrated that regular aerobic exercise improves the ability of arteries to dilate in older adults,” said Christopher A. DeSouza, Ph.D., an associate professor in the department of integrative physiology at the University of Colorado in Boulder.

In this study, researchers investigated if exercise improves blood vessels’ responsiveness to a naturally occurring chemical released from cells that line the blood vessel, which causes them to constrict. Vasodilatation (vessel expansion) and vasoconstriction play a crucial role in the body’s ability to regulate blood pressure.

“Interestingly, the older subjects’ forearm blood flow responses were similar to those of our younger subjects after only three months of exercise,” said lead author Gary P. Van Guilder, M.S., presenter of the study, and a doctoral student and research assistant at the university.

Advancing age is associated with an increased risk of cardiovascular disease. Dysfunctions in the way the blood vessels dilate and constrict contribute to the development of atherosclerosis.

Researchers focused on the subjects’ reaction to a peptide called endothelin-1 (ET-1) released by cells that line the blood vessels. Changes in the activity of ET-1 have been linked to the development of many of the cardiovascular complications associated with age, including high blood pressure, arterial spasm, heart attack and heart failure.

Young blood vessels are compliant, easily dilating and constricting in response to various chemicals released by cells in the blood vessel walls. Aging vessels behave differently, sometimes showing a blunted response to experimental injections of ET-1, Van Guilder said.

DeSouza said earlier studies found greater ET-1 activity and more ET_A receptors (ET-1 binds to ET_A) in atherosclerotic plaques. An overabundance of receptors has also been found in diseased coronary arteries that are prone to vasospasm (constriction resulting in reduced blood flow to the heart) and in failed vein grafts used in bypass surgery, he said.

The study involved 28 healthy sedentary men: 14 younger subjects, average age 27, and 14 older subjects, average age 62. The researchers measured the participants’ forearm blood flow when they gave the men injections of two substances, the peptide ET-1 and a drug that blocks the action of the ET-1 at its receptor ET_A. The second drug is called BQ-123.

The older sedentary subjects’ response to the extra ET-1 was markedly lower than the reaction of younger sedentary subjects, suggesting an age-related increase in ET-1 production within the body, DeSouza said.

When researchers gave the subjects the ET_A receptor blocker BQ-123, the younger sedentary men showed no significant change in their vessels. However, the older men showed about a 30 percent increase in forearm blood flow in response to the BQ-123_.

After establishing the differing reactions between older and younger sedentary men, the researchers put eight of the 14 older men on an exercise program consisting of about 55 minutes of walking a day for about five days per week for three months. The exercise was not strenuous enough to cause changes in body weight or percentage of body fat, but the men who exercised displayed increased stamina and spent about 25 percent more time on a treadmill test used to measure their fitness level. After exercise training, the older men were able to exercise 25 percent longer on an exercise test compared with before exercise.

After three months on the exercise program, BQ-123 infusions resulted in modest vasoconstriction in the older formerly sedentary men, compared to marked vasodilatation before the exercise program. Moreover, the vessel constriction in response to ET-1 was greater than before they followed the exercise program. These two findings indicate that the vessels of the older men who exercised were behaving more like those of the younger subjects, researchers said.

“It’s never too late to start exercising,” DeSouza said. “It’s important to emphasize that these improvements resulted from a moderate amount of aerobic exercise that most, if not all, middle-aged and older people can perform. Simply go for a moderately brisk walk every day.”

Co-authors are Christian M. Westby, M.S.; Greta L. Hoetzer, Ph.D.; Jared J. Greiner, M.S.; Yoli G. Casas, M.S.; and Brian L. Stauffer, M.D.

Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.