Young Healthy Men and Women Have Similar Arterial Stiffness at Rest and Post‐Acute Inflammation

Abstract

The cardioprotective effects of estrogen on arterial function and inflammation are well‐documented; however, it is unclear whether arterial stiffness and compliance vary between healthy premenopausal women and age‐matched men following an acute inflammation. The objective of the current study was to evaluate central and local arterial stiffness and compliance at rest and in response to an acute inflammatory stimulus, specifically, when estrogen levels are thought to be similar between young healthy women and men. It was hypothesized that sustained effects of estrogen throughout the lower‐hormone phase of a natural menstrual or oral contraceptive pill cycle would induce lower central and local stiffness and higher compliance in women as compared to men at rest and in response to an acute inflammatory stimulus. Concentrations of interleukin‐6 (IL‐6) and assessments of central and local arterial stiffness and compliance were obtained from 29 young healthy adults (21±3 y; female, n=15) at baseline (BL), and 24‐ (24H) and 48‐hours (48H) following administration of a seasonal influenza vaccine. To capture the lower‐hormone phases of female participants, women were assessed within the early follicular phase if naturally menstruating or the placebo pill phase if using oral contraceptives. Central stiffness was assessed via carotid‐to‐femoral pulse wave velocity (cfPWV) and local stiffness was measured using ultrasonography at the carotid artery to obtain β‐stiffness, elastic modulus (Ep) and arterial compliance (AC). IL‐6 concentrations were expressed as change‐values from BL and were compared between sexes and timepoints (24H‐BL vs. 48H‐BL). Indices of central and local stiffness and AC were compared between sexes and individual timepoints (BL vs. 24H vs. 48H). Men and women exhibited similar changes in concentrations of IL‐6 (effect of sex: P=0.60), with significant elevations at 24H‐BL as compared to 48H‐BL (effect of time: P=0.0002), indicating that the influenza vaccine successfully induced an acute inflammatory response in both groups. However, there were no effects of sex or time on cfPWV, β‐stiffness or Ep (P>0.05 for all). While men displayed greater AC as compared to women at BL (1.09±0.25 vs. 0.88±0.17 mm2/kPa, P=0.01), there were no sex‐differences at 24H and 48H (P=0.10 and 0.70, respectfully), suggesting that the women were able to compensate for their lower resting AC values when exposed to an acute inflammatory stimulus. In conclusion, when estrogen levels are similar between young healthy women and men, there are no sex‐differences in central or local arterial stiffness at rest nor in response to an acute inflammatory stimulus.