Racial Differences in Vascular Function in Response to Mental Stress: Role of Acute Dietary Nitrate Supplementation
Authors: Campbell Jeremiah C. , Akins John D. , Olvera Guillermo , Curtis Bryon M. , Keller David M. , Brothers R. Matthew 
Published: June 2021

Black individuals (BL) have a higher prevalence of hypertension and cardiovascular disease (CVD) relative to other populations. The reason for this elevated risk is multifactorial, with impaired vascular function being a primary factor. Mental stress, induced by mental arithmetic, elicits an increase in forearm blood flow (FBF) that is attributed in large part to the release and vasodilatory effect of nitric oxide (NO). Previous reports demonstrate that BL have attenuated vasodilatory capacity in part due to reduced NO bioavailability and the increase in FBF during mental stress is blunted in middle‐aged BL relative to whites (WH). Recently we have extended these findings to a younger cohort of BL (i.e., ~21 yr). Emerging evidence indicates that dietary nitrate supplementation improves a variety of physiological variables including improvements in vascular function as indexed by augmented vasodilatory capacity. Accordingly, the present study tested the hypothesis that acute nitrate supplementation would augment the blunted FBF hyperemic response to mental stress previously observed in BL. Eight young, healthy BL men (22±2 yr) participated in this double‐blind, placebo‐controlled, crossover, randomized study. Measurements were obtained in the morning following an overnight fast. On each study visit, brachial artery diameter and blood velocity were assessed using high resolution duplex Doppler ultrasound and were used for subsequent calculation of FBF. Mental stress was induced by having subjects subtract either 9or 13 continuously from a 3‐digit number while attempting to report answers at a pace set by a 60 bpm metronome. FBF was measured during a 2 min baseline followed by 3 min of mental stress and 2 min of recovery. These procedures were conducted during 2 visits to the laboratory separated by ~1 wk. During each visit, data was collected before and 2 hr post consumption of a beverage either high in nitrate content (Beet‐It‐Sport; BJ: 140ml, ~12.8 mmol of nitrate; James White Drinks Ltd., Ipswich, UK) or nitrate depleted (PL: 140ml, ~0.0055 mmol of nitrate). Vascular function was assessed as the absolute peak FBF (ml/min) and absolute peak conductance (FVC: ml/min/mmHg) response during each bout of mental stress. Pre‐beverage peak FBF was similar between visits (PL: 205±46, BJ: 180±40 ml/min; P=0.37) and this response was unaffected by beverage consumption (PL: 136±17, BJ: 135±24 ml/min; main effect of time P=0.07; main effect of condition P=0.32, interaction P=0.50). Likewise, pre‐beverage peak FVC was similar between visits (PL: 2.3±0.4, BJ: 2.0±0.4 ml/min/mmHg; P=0.27). Although there was a trend for a reduction in peak FVC following beverage consumption (PL: 1.5±0.2, BJ: 1.5±0.2 ml/min/mmHg; main effect of time P=0.05) the response was similar between conditions (main effect of condition P=0.34) such that there was not an interaction (P=0.31). Contrary to our hypothesis, these findings suggest that acute dietary nitrate supplementation does not augment the FBF hyperemic response to mental stress in BL that has been previously reported to be blunted relative to WH.

Support or Funding Information

UTA Start‐up funds to R. Matthew Brothers

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.