Effect of Dietary Nitrate on Blood Pressure and Vascular Control in Post‐Menopausal Hypertensive Women

Abstract

Individuals with hypertension exhibit abnormal pressor responses during rest‐to‐exercise transitions, significantly increasing the likelihood of sudden cardiac events. Dietary nitrate supplementation can lower resting blood pressure in patients with hypertension and improve bulk muscle blood flow in older healthy adults. However, investigations using dietary nitrate as a non‐pharmacological intervention in post‐menopausal women diagnosed with hypertension are lacking. Therefore, the purpose of the current investigation was to determine if acute dietary nitrate supplementation would improve the pressor response to exercise and increase forearm blood flow during steady‐state hand‐grip exercise in post‐menopausal hypertensive women. It was hypothesized that the pressor response to exercise would be attenuated and muscle blood flow would be improved in the nitrate‐rich (NR) versus nitrate‐poor (NP) treatment.METHODSTen hypertensive post‐menopausal women [age 56 ± 3 years (mean±SD); height 165 ± 2 cm; mass 84 ± 13 kg; body mass index 31 ± 5 kg/m2] agreed to participate in the current study. Patients underwent a randomized double‐blind placebo‐controlled trial with a NR or NP beet root juice supplement. Blood samples were taken at the beginning of each testing session (~2 h post ingestion) to determine plasma nitrite levels. Forearm blood flow (FBF) was measured via ultrasonography at the brachial artery of the exercising limb. Beat‐by‐beat blood pressure and heart rate were recorded throughout the trial on the non‐exercising limb. After resting measurements were completed, patients performed hand‐grip exercise at 20% maximal voluntary contraction (MVC) for five minutes to obtain steady‐state blood flow and blood pressure response to exercise.RESULTSPlasma nitrite levels were significantly higher during the NR (809 ± 146 nM) than the NP (79 ± 19 nM) condition. No differences were found between conditions for resting blood flow (NR: 64±2; NP: 62 ± 4 ml min−1; P > 0.05), systolic (NR: 144 ± 2; NP: 145 ± 2 mmHg−1; P > 0.05) or diastolic blood pressure (NR: 78 ± 1; NP: 80 ± 1 mmHg−1; P > 0.05). In addition, there were no significant differences across 10‐second bins (e.g., 0–10, 11–20 seconds) during the first minute pressor response to hand‐grip exercise in either condition (systolic: P > 0.05; diastolic: P > 0.05). As such, the rate pressure product was not significantly different during steady‐state between conditions (NR: 11,562 ± 437; NP: 11,728 ± 437 bpm · mmHg−1; P > 0.05). During steady‐state exercise, FBF (NR: 189 ± 8; NP: 218 ± 8 ml min−1; P = 0.03) and forearm vascular conductance (FVC) (NR: 157 ± 4; NP: 183 ± 4 ml min−1; P = 0.04) were significantly lower during the steady‐state NR condition.CONCLUSIONAcute dietary nitrate supplementation did not improve the pressor response to hand‐grip exercise in hypertensive post‐menopausal women. However, it is important to note that steady‐state FBF (~30 ml min−1) and FVC (~27 ml min mmHg−1) were significantly reduced during the nitrate‐rich condition, which suggests a reduced O2 cost for a given workload because blood flow typically matches metabolic rate.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.