- Objectives: Nitrate, found abundantly in green leafy vegetables, may improve exercise performance by increasing the availability and utilization of metabolic fuels that require less oxygen for energy production. However, it is not known if this performance effect occurs at the peak exercise intensity. We hypothesize that supplemental nitrate treatment will promote the metabolism of specific fuels (carbohydrates versus fatty acids) during exercise that require less oxygen to produce ATP. Metabolic analysis will quantify if a net change in these fuels are linked to an improvement in exercise performance with nitrate treatment during submaximal exercise conditions.
Methods: Adult zebrafish were exposed to sodium nitrate (606.9 mg NaNO3/L water) or control water for 21 days (n= 54). Fish were sampled at three conditions during a graded exercise test: 1) rest, 2) peak speed, and 3) post-exercise. Whole fish tissue was homogenized and analyzed using high-pressure liquid chromatography Triple Q-ToF mass spectrometry based untargeted metabolomics.
Results: Metabolomics analysis resulted in the annotation of 232 unique monoisotopic features. The results of a 2-way ANOVA yielded 79 metabolites that were significantly altered by nitrate treatment, exercise, or an interaction effect. Additionally, each treatment condition was compared to other relevant conditions by t-tests. We did not observe nitrate-induced differences in glycolytic intermediates. However, specific TCA intermediates, acylcarnitines, proline protein derivatives, and a vasodilatory metabolite demonstrate significant metabolic changes with nitrate treatment at rest as well as peak exercise as compared to controls at the same exercise condition.
Conclusions: Observations made in this study concerning the means by which (how) nitrate reduces the cost of oxygen during exercise was not as consistent with previous studies. However, our observations suggest other potential mechanisms by which supplemental nitrate can alter the abundance and utilization of different fuel sources, and hemodynamics at rest and during submaximal exercise.