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Abstract
Equol, a gut bacterial metabolite of isoflavone daidzein, may improve health through
changes in vascular function and in estrogen metabolism. Tibolone, a synthetic steroid
alternative for the treatment of postmenopausal symptoms, causes a different estrogenic
milieu than estrogen and may affect vascular health. We studied the effects of equol
production and soy supplementation on vascular function in postmenopausal women under
long-term tibolone use.
We screened 110 women using tibolone for 3-60 months for high equol production capacity
with a one-week soy challenge. Twenty women with high equol production capacity (4-fold
elevation in equol level) and 20 comparable control women without this capacity were
treated in a randomized placebo-controlled cross-over trial with a soy drink (52 g
of soy protein containing 112 mg of isoflavones) or placebo for 8 weeks. Arterial
stiffness and endothelial function were assessed before and after soy and placebo
supplementation with pulse-wave analysis.
Prior to soy supplementation arterial stiffness, expressed as augmentation index,
was lower (p=0.01) in equol producers (25.9+/-1.1%) than non-equol producers (29.6+/-0.9%).
Similarly, endothelial function index was better at baseline (p=0.009) in these women
(72.3+/-5.3%) compared to women lacking equol production capacity (55.2+/-3.8%). Soy
supplementation had no effect on arterial stiffness or endothelial function in either
group.
In postmenopausal tibolone users, endogenous equol production capability is associated
with favorable vascular function. This phenomenon was not affected by soy and thus,
equol producing capacity may be an independent vascular health marker, at least in
postmenopausal women using tibolone.