Found: Missing link to postmenopause vascular health?

A specific chemical cofactor called BH₄ (tetrahydrobiopterin) may be the missing link to understanding and potentially reversing the decline in vascular health that occurs after menopause, according to a small study published January 13 in the American Journal of Physiology - Heart and Circulatory Physiology.

“These results provide novel insight into a potential mechanism by which oxidative stress contributes to the large elastic artery stiffening in estrogen-deficient postmenopausal women,” the authors write. BH₄ is critical to the body’s process of producing nitric oxide. Nitric oxide increases arterial dilation and tone and decreases arterial stiffness.

BH₄ was given to 24 postmenopausal and 9 premenopausal women. Three hours later. BH₄ increased carotid artery compliance by 24±5% in the postmenopausal women (versus baseline, P<0.0001) but had no effect in the younger women (P=0.10) or on brachial artery compliance in either group (P=0.52).  Similarly, it increased brachial artery flow-mediated dilation (FMD) 64±11% in the postmenopausal women (P<0.001) but did not have a significant effect in the premenopausal group (P=0.01).

In the second part of the study, half of the postmenopausal women were given placebo; the other half received transdermal estradiol. Two days later, women given estradiol had effects similar to the women who had received BH₄, while those given placebo experienced no changes, even after adjusting for potential confounders. Further, coadministered BH₄ and estradiol provided no further benefit on vascular function, suggesting that estrogen helps to maintain adequate BH₄ levels.

“Our results suggest that the beneficial effects of estrogen on arterial stiffening in previously estrogen-deficient postmenopausal women may be mediated by improved endothelial vasodilatory tone, secondary to increasing BH₄ bioavailability,” the authors write.

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