The impact of menstrual phase on brachial artery flow-mediated dilation during handgrip exercise in healthy premenopausal women

Abstract

Flow-mediated dilation (FMD) in response to a sustained shear stress stimulus (e.g. via handgrip exercise; HGEX) is emerging as a useful tool for assessing endothelial function; however, the impact of menstrual phase on HGEX-FMD is unknown. The purpose of this study was to determine whether HGEX-FMD fluctuates with cyclical changes in estrogen levels over two discrete phases (low and high estrogen) of the menstrual cycle. Brachial artery (BA) diameter and blood velocity were assessed with 2D and Doppler ultrasound, respectively. Shear stress was estimated using shear rate (SR = BA blood velocity/BA diameter). Participants (12 healthy, regularly cycling women 21 ± 2 yrs) completed two experimental visits: (1) low estrogen (early follicular, EF) and (2) high estrogen (late follicular, LF). Reactive hyperemia stimulated FMD (RH-FMD) and HGEX-FMD (6-minutes of handgrip exercise) were assessed each visit. Results are mean ± SD. Estrogen increased from the EF to LF phase (EF: 33 ± 9 pg mL⁻¹; LF: 161 ± 113 pg mL⁻¹, P = 0.003). However, neither the SR stimuli (HGEX P = 0.501; RH P = 0.173), nor the FMD responses differed between phases (EF vs. LF: HGEX-FMD: 4.8 ± 2.8% vs. 4.6 ± 2.2%, P = 0.601; RH-FMD: 7.9 ± 4.3% vs. 6.4 ± 3.1%, P = 0.071). These results extend existing RH-FMD findings indicating that not all women experience fluctuations in FMD with the menstrual cycle. Further research is needed to investigate the mechanisms that underlie variability in the impact of menstrual phase on FMD.

This article is protected by copyright. All rights reserved

from Physiology via xlomafota13 on Inoreader http://ift.tt/2ifBHgE
via IFTTT