Effect of short‐term 17B‐estradiol on low‐flow‐mediated constriction in young women

Abstract

Low‐flow mediated constriction (L‐FMC) examines vascular responses during a reduction in blood flow and provides a measure of resting shear‐stress dependent vascular tone. L‐FMC is a complementary measure to flow‐mediated dilation (FMD), and is blunted in patients with cardiovascular disease. 17β‐estradiol (E2) exerts positive effects on vascular endothelial health and can improve FMD. However, it is unknown whether E2 impacts L‐FMC.PURPOSEThe purpose of this study was to test the hypothesis that E2 administration would augment L‐FMC in young women.METHODSEleven young women (24±1 years, 24±1 kg/m2) have completed the study. To isolate the impact of E2, endogenous ovarian hormone production was suppressed with daily subcutaneous injections of a gonadotropin releasing hormone antagonist (GnRHant, 0.25 mg/day) for 10 days. E2 (0.1mg/day patch) was administered during the last 7 days of GnRHant. We measured changes in brachial artery diameter via ultrasound on day 3 of GnRHant and day 7 of E2 add‐back. A blood pressure cuff was placed just distal to the olecranon process and inflated to 200mmHg for five minutes. Images were recorded continuously at baseline (1‐minute), during occlusion (5‐minutes), and after cuff deflation (2‐minutes). L‐FMC was determined from the last 30 seconds of cuff inflation using the lowest average value and was reported as percent change from baseline diameter. FMD was calculated as a percent change from baseline to peak diameter after cuff deflation. Total vessel reactivity was calculated as the absolute value of L‐FMC and FMD. Results are reported as mean ± standard error.RESULTSBaseline diameter was similar between GnRHant (3.14 ± 0.12 mm) and E2 (3.08 ± 0.11 mm; p=0.3). L‐FMC tended to be greater during E2 administration (GnRHant −2.5 ± 0.5% vs. E2 −3.8 ± 0.5%; p=0.11). However, FMD (GnRHant 7.5 ± 0.7% vs. E2 7.6 ± 1.1%; p=0.92) and total vessel reactivity (GnRHant 10.0 ± 0.7% vs. E2 11.5 ± 1.2%; p=0.26) were not altered by E2.CONCLUSIONThese preliminary findings suggest that short term E2 administration may augment L‐FMC in young women. Additional data are needed to understand the impact of ovarian hormones on L‐FMC and its role in regulating vascular health.Support or Funding InformationNIH Grant P20 GM 103446, P20 GM 113125, U54 GM 104941, The University of Delaware Research Foundation, and AHA Award 16SDG30700015This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.