Similar inflammatory response and conduit artery vascular function between sexes following induced inflammation

Abstract

What is the central question of this study? Are there sex differences in vascular function following induced inflammation when oestrogen is typically similar between sexes? What is the main finding and its importance? The present study suggests no sex differences in conduit artery vascular responses to acutely induced inflammation during the low-oestrogen phase of the menstrual cycle in premenopausal women. However, women exhibit lower microvascular function than men. Overall, the results underpin the role of oestrogen in previously observed sex differences and the importance of reporting the phase in the hormonal cycle when women are studied. Sex differences in cardiovascular disease incidence in premenopausal women and age-matched men have been attributed to the cardioprotective influence of oestrogen. However, limited knowledge exists regarding sex differences following acute inflammation when oestrogen concentrations are lower in women. We evaluated sex differences in vascular responses to induced inflammation when oestrogen concentrations are typically lower in women (early follicular phase or placebo phase of hormonal contraception). In 15 women and 14 men, interleukin-6 (IL-6) concentrations and vascular function [via brachial artery flow-mediated dilatation (FMD)] were assessed at baseline (BL) and 24 (24H) and 48hours (48H) after administration of influenza vaccine. After induction of inflammation, both sexes exhibited an increase in IL-6 concentrations at 24H [mean (SD) BL vs. 24H: women, 0.563 (0.50) vs. 1.141 (0.65) pg/ml; men, 0.385 (0.17) vs. 1.113 (0.69) pg/ml; P<0.05] that returned to near-baseline concentrations by 48H (BL vs. 48H, P>0.05). There were no sex differences in FMD, allometrically scaled FMD or IL-6 concentrations at any time point (P>0.05). Notably, women exhibited significantly lower microvascular function than men at every time point [P<0.05; reactive hyperaemic area under the curve (in arbitrary units): women, BL 35,512 (14,916), 24H 34,428 (14,292) and 48H 39,467 (13,936); men, BL 61,748 (27,324), 24H 75,028 (29,051) and 48H 59,532 (13,960)]. When oestrogen concentrations are typically lower in women, women exhibit a similar inflammatory response and conduit artery function, but lower microvascular response to reactive hyperaemia, in comparison to age-matched men.