Low antioxidant levels contribute to increased blood pressure during exercise for people with peripheral arterial disease, according to researchers at Penn State Hershey Heart and Vascular Institute.
Peripheral arterial disease, or PAD, affects an estimated 10 million Americans and increases the chance of death from a cardiovascular event. Reduced blood flow causes pain in the legs and increases blood pressure in people who have PAD. However, the causes of the disease are unknown.
"Past studies have shown that having low antioxidant levels and increased reactive oxygen species—chemical products that bind to body cells and cause damage—is related to more severe PAD," said Matthew Muller, postdoctoral fellow in Dr. Larry Sinoway's lab at Penn State College of Medicine, and lead author of the study.
Antioxidants prevent the reactive oxygen species from damaging cells.
"This study shows that blood pressure increases more with exercise in more severe PAD cases. By infusing the antioxidant vitamin C into the blood, we were able to lessen the increase in blood pressure during exercise," said Muller.
Vitamin C does not lessen the increase in blood pressure of PAD patients to that of healthy people. As the intensity of exercise increases, the effects of vitamin C decrease but are still seen. The researchers report their findings in the Journal of Physiology.
Penn State Hershey researchers looked at three groups of PAD patients to study the blood pressure increase. A group of 13 PAD patients was compared to people without PAD to see the effects of doing low-intensity exercise on blood pressure. From that group, a second group of nine patients was used to measure the effects of vitamin C. A third group of five PAD patients and five without PAD had their leg muscles electrically stimulated to remove the brain's role in raising blood pressure during muscle contraction in this disease.
Increased blood pressure during exercise occurs in both legs, before pain begins, and relates to the severity of the disease. By using electrical stimulation, the scientists show that the blood pressure increase comes from the muscle itself, since the brain is not telling the leg to contract and the pressure still increases.
"This indicates that during normal, everyday activities such as walking, an impaired antioxidant system—as well as other factors—plays a role in the increased blood pressure response to exercise," Muller said. "Therefore, supplementing the diet with antioxidants may help these patients, but more studies are needed to confirm this concept."
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