Effects of Acute Nocturnal Inorganic Nitrate Supplementation on Early Morning Vascular Function: A Pilot Study

INTRODUCTION: The increased likelihood of adverse cardiovascular events (CVE) shortly after awakening has been partially attributed to low nitric oxide (NO) production in the early morning. Thus, increasing early morning NO levels to improve vascular function could reduce adverse CVE incidence, especially among older adults as total NO production declines with aging. The increased adverse CVE among post-menopausal women (PMW) are likely due to a steeper decline in their vascular function. As inorganic nitrate increases circulating NO levels for up to 12hrs, our primary hypothesis was to determine if nocturnal inorganic nitrate supplementation improves early morning vascular function relative to a placebo in eight generally healthy adults (6F, 37±5yrs, 26.9±1.8kg/m 2 ). Our secondary hypothesis was that PMW (n=3, 27.1±4.3kg/m 2 ), identified by their age (71±2yrs) and follicle-stimulating hormone levels (72.3±8.0mIU/mL), would show greater improvements in their vascular function compared to younger participants (n=5, 3F, 28±2yrs, 26.8±2.0kg/m 2 ). METHODS: Written informed consent was obtained from all participants before data collection. Participants completed three overnight study visits: Visit 1 was for acclimation with vascular function assessments occurring during Visits 2 and 3. During the latter visits, participants consumed beetroot juice with (6.45mmol) or devoid of (0mmol) inorganic nitrate at 2200 in randomized, cross-over fashion followed by vascular function assessments post-awakening (0630-0800) while participants were supine. Vascular assessments consisted of brachial blood pressure, aortic augmentation index (AIx), carotid-femoral pulse wave velocity (cfPWV), and endothelial function (FMD). Data were compared using a paired-samples t-test (α<0.05). RESULTS: Systolic (125±4 vs. 126±6mmHg, p=0.35) and diastolic (71±2 vs. 72±2mmHg, p=0.32) blood pressure were similar the morning after nitrate and placebo. Additionally, AIx (31±5 vs. 33±6%, p=0.29) and FMD (n=7, 8.8±2.0 vs. 7.6±1.7%, p=0.25) were not different the morning after nitrate and placebo consumption. However, cfPWV was lower the morning following nitrate consumption relative to the placebo (6.3±0.5 vs. 6.9±0.6m/s, p=0.01). A sub-group analysis of PMW showed that both systolic (132±6 vs. 139±9mmHg, p=0.18) and diastolic (70±3 vs. 75±2mmHg, p=0.09) blood pressure tended to be lower following nitrate relative to the placebo whereas AIx (46±1 vs. 50±5%, p=0.31) and FMD (n=2, 8.5±2.7 vs. 6.9±1.6%, p=0.78) did not differ; however, cfPWV was lower the morning after nitrate consumption (7.4±0.9 vs. 8.4±1.1m/s, p=0.02) in PMW but not in the younger participants (5.6±0.4 vs. 6.0±0.3m/s, p=0.23). CONCLUSION: Acute nocturnal inorganic nitrate supplementation lowers aortic stiffness in the early morning, especially among PMW. Although the differences in systolic (7mmHg) and diastolic blood pressure (5mmHg) were not statistically significant, they remain clinically meaningful due to their magnitude. This may suggest a role for nocturnal nitrate supplementation in reducing early-morning adverse CVE among PMW. AHA 24POST1241616 (IMG), NIH K12 AR084222 (JMB), Sleep Research Society 038-JP-23 (JMB), and a grant from Sleep Number Corporation to Mayo Clinic for studies in Aging. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.