P11: Higher levels of endogenous nitrite are associated with superior vascular function and lactate anaerobic threshold in athletes

Abstract

Background Nitrate and nitrite as oxidative derivates of nitric oxide have been suggested to both modulate and reflect exercise capacity in humans. The failure to increase endogenous nitrite has been related to decreased maximum exercise capacity, while a diet rich in nitrate improved exercise performance. The modulation of nitrate/nitrite levels has furthermore been related to an improvement of vascular functions. It remains unresolved to date whether baseline endogenous levels are associated with a superior vascular function and if this is also related to an improved exercise capacity. Objective To determine whether higher baseline nitrite levels are associated with a superior vascular function and whether this also relates to an advantage in exercise capacity as measured by lactate anaerobic threshold (LAT). Methods 12 male athletes with an average age of 25 ± 2 years, a body weight of 79 ± 4 kg, a height of 185 ± 5 cm and trained 5 ± 1 times per week (means ± SD) were enrolled in this study. Each participant reported twice to the testing facility ( n = 22 observations). Blood was drawn from the left cubital vein and the resulting plasma was used to determine the circulating levels of nitrate and nitrite via HPLC (ENO-20). 15 min later, vascular function was assessed on the contralateral arm (brachial artery) by measuring flow-mediated vasodilation (FMD) using a 12 MHz ultrasound probe. Participants were hereafter asked to complete a stepwise ergometric test starting at 100 W with increasing workloads (+50 W) every 5 min on a stationary bicycle ergometer (Lode Excalibur Sport). Blood was drawn from the ear lope and used to determine the levels of lactate at the end of each incremental steP Heart rate was measured continuously and the LAT (4 mM) in relation to heart rate was calculated using non-linear regression models. Results Baseline plasma nitrite levels correlated with LATs ( r = 0.65; p = 0.001, n = 22) and with endothelial function as assessed by FMD ( r = 0.71; p = 0.0002). Cor-relation coefficients from both testing days did not differ. Multiple linear regressions showed that base-line plasma nitrite level but not endothelial function was an independent predictor of exercise capacity. No such correlations were determined for plasma nitrate levels. Conclusion Higher baseline levels of nitrite are associated with a superior vascular function and lactate anerobic threshold. Disclosure M.T. was supported by a scholarship from the Deutsche Herzstiftung (German Heart Foundation), M.K. and T.R. were supported by grants from the German Research Foundation (DFG).