LAUSR

BACKGROUND Chronic under perfusion of the skeletal muscle tissues is a contributor to decreased exercise capacity in patients with heart failure reduced ejection fraction (HFrEF. This under perfusion is due, at least in part, to impaired nitric oxide (NO) bioavailability. Oral inorganic nitrate supplementation increases NO bioavailability and may be used to improve exercise capacity, vascular function and mitochondrial respiration. METHODS Sixteen patients with HFrEF (15 men, 63 +/- 4 y, BMI: 31.8 +/- 2.1 kg∙m-2) participated in a randomised, double-blind, crossover design study. Following consumption of either nitrate rich beetroot juice (16 mmol nitrate/day), or a nitrate-depleted placebo for five days participants completed separate visits for assessment of exercise capacity, endothelial function and muscle mitochondrial respiration. Participants then had a two week washout prior to completion of the same protocol with the other intervention. Statistical significance was set a priori at p<0.05 and between treatment differences were analysed via paired- t-test analysis. RESULTS Following nitrate supplementation both plasma nitrate and nitrite increased (933%, p<0.001 and 94%, p< 0.05, respectively). No differences were observed for VO2peak (nitrate 18.5 +/- 5.7ml∙kg-1∙min-1, placebo: 19.3 +/- 1.4ml∙kg-1∙min-1; p=0.13) or time to exhaustion (nitrate: 1165 +/- 92sec, placebo: 1207 +/- 96sec, p=0.16) following supplementation. There were no differences between interventions for measures of vascular function, mitochondrial respiratory function or protein expression (all p>0.05). CONCLUSIONS Inorganic nitrate supplementation did not improve exercise capacity and skeletal muscle mitochondrial respiratory function in HFrEF. Future studies should explore alternative interventions to improve peripheral muscle tissue function in HFrEF.