The expanding waistline and increasing cholesterol levels many women face after menopause may be a factor in the stiffening of their arteries, increasing their risk of cardiovascular disease, researchers report in Hypertension: Journal of the American Heart Association.
Age and menopause are associated with an increase in arterial stiffness. Kerrie L. Moreau, Ph.D., assistant research professor at the University of Colorado at Boulder, and colleagues attempted to define whether the development of oxidative stress, which is higher after estrogen production ceases at menopause, plays a role in artery stiffening.
Oxidative stress can occur as a result of too many oxygen free radicals that attack cells such as those lining arteries or low levels of the body?s antioxidants and contributes to cardiovascular disease and other health conditions.
In this study of 31 healthy, but sedentary women, researchers found that carotid arteries in postmenopausal women were 56 percent less elastic compared to those of premenopausal women.
They assessed whether oxidative stress was at least partially to blame by measuring the effect of ascorbic acid (vitamin C) on the women?s arteries. Ascorbic acid is a potent antioxidant and has other healthy properties.
Ten of the women were premenopausal (average age 23) and 21 were postmenopausal (average age 55). Researchers measured their levels of blood cholesterol, glucose, insulin and the stress hormone norepinephrine after a 12-hour fast. They also determined their total fat mass and abdominal fat and calculated their waist-to-hip ratios. Then researchers used ultrasound to measure the elasticity of the carotid arteries, which are the arteries in the neck that are the main blood supply to the brain. Initial carotid measurements were taken while the women were receiving intravenous infusions of saline and then again with infusions of ascorbic acid, which reduces oxidative stress.
When the postmenopausal women were infused with ascorbic acid, elasticity in their carotid arteries improved by about 26 percent, which was statistically significant. However, there was no effect among the premenopausal women.
Researchers also noted that the improvement in carotid artery compliance with the ascorbic acid infusion was positively correlated with baseline waist-to-hip ratio, LDL-cholesterol, and plasma norepinephrine, leading the authors to believe that increased body fat storage in the abdominal region, sympathetic nervous system activity and circulating LDL-cholesterol may be factors involved in the oxidative stress associated reduction in carotid artery compliance.
Moreau explained that after menopause many women undergo a shift in body fat so that there is more fat in the abdomen area. This increase in abdominal body fat can cause the sympathetic nervous system to become elevated, which could cause arterial compliance to be reduced. Additionally, LDL or bad cholesterol levels increase after menopause. All of these factors can contribute to the development of oxidative stress, which is compounded in postmenopausal women because they are no longer producing estrogen, a natural antioxidant.
Taken together, all these factors – increased abdominal fat, elevated sympathetic nervous system activity, higher LDL cholesterol and loss of estrogen – produce oxidative stress which, in turn, contributes to a loss of elasticity in arteries, she said.
Weight gain and cholesterol increases, while common during the transition from menopause to postmenopause, are exacerbated by lifestyle – sedentary women are likely to gain more weight and experience even greater increases in cholesterol than women who exercise regularly, Moreau said. Moreau and colleagues have shown previously that postmenopausal women who exercise regularly have healthier arteries; however, whether this is due to reduced oxidative stress in unknown.
She emphasized that the aim of the study was not to determine the efficacy of vitamin C supplementation as a potential intervention. Recent clinical trials have demonstrated no effect on vitamin C on cardiovascular disease outcomes, and this may be because oral vitamin C supplementation cannot maintain blood ascorbic acid concentration at levels needed to counterattack oxidative stress. Another limitation is that the two groups of women were not comparable in age.
The findings here suggest the role of oxidative stress in the reduced artery elasticity observed in postmenopausal women – a group at increased risk of cardiovascular disease. Furthermore, the study reinforces that women should maintain healthy blood cholesterol levels and a healthy weight.