Author(s): OCHIAI, A., MATSUDAIRA, H., YAMADA, K., TAKEHARA, K., IWATA, Y., ITO, R., SATO, T., HAGINO, Y., MIYAZAKI, M., TSUDA, T., ITOH, H., Institution: NAGOYA INSTITUTE OF TECHNOLOGY, Country: JAPAN, Abstract-ID: 339

INTRODUCTION:
The combination of oral L-arginine and L-citrulline immediately and synergistically increases plasma arginine and nitrite/nitrate (NOx) concentrations more than either citrulline or arginine alone (1,2). Nitric oxide (NO) is the most important endothelium-derived relaxing factor, which plays a pivotal role in modulating smooth muscle tone (3). During exercise, increasing NO production facilitate blood flow in muscle tissues, muscle energy metabolism, and mitochondrial respiration, therefore previous human study has reported that oral arginine-citrulline supplement improved exercise performance due to increase NO bioavailability (1). However, there is little data concerning the effect of arginine-citrulline supplement on skin-gas NO concentration during exercise. The present study examined to confirm the effect of arginine-citrulline supplement on blood flow of active muscles and skin-gas NO concentrations following maximal running exercise.
METHODS:
A double-blind randomized placebo-controlled 2-way crossover study was employed. Ten healthy male students (23.0 ± 0.5 years; mean ± SD) consumed arginine-citrulline supplement (VELOX Charge: Kyowa Kirin Co., Ltd., Japan) or placebo orally 1 h before incremental maximal running exercise exhausting within 30 min. The skin-gas samples were obtained from the dominant hand by covering with a polyethylene bag in which pure nitrogen gas (250mL) was introduced for 100 sec and collected in a sampling bag at rest and 0, 5, 10, 15, 30 min recovery of the exercise. The skin-gas NO concentration was measured by a chemiluminescence analyzer (Pico-Device Co., Ltd., Japan). Blood flow measured using a laser tissue blood flow meter from non-dominant hand skin surface (Omegaflo, Omega Wave, Japan).
RESULTS:
The arginine-citrulline supplement significantly (p<0.05) increased running time and distance compared to the placebo. Maximal exercise in this study significantly increased skin-gas NO concentration (p<0.05) and blood flow (p<0.001) after the exercise compared to the resting values. Significant higher levels were observed in skin-gas NO concentration (p<0.001) and blood flow (p<0.001) in the supplemental condition compared to the placebo. Moreover, there were significant relationships between skin-gas NO concentration and blood flow both in supplemental (r = 0.5676, p<0.001) and placebo (r = 0.6050, p<0.001) conditions.
CONCLUSION:
Significantly higher levels of skin-gas NO concentration has indicated that the arginine-citrulline supplement increased NO production and NO bioavailability in the whole body during the maximal exercise. As a result, blood flow, energy metabolism, and mitochondrial respiration in active quadriceps muscle during the maximal running exercise facilitated by the arginine-citrulline supplement, consequently improved exercise performance (1).
1 Suzuki I et al. (2019) Eur J Appl Physiol., 119(5):1075-1084.
2 Morita M et al. (2014) Biochem Biophys Res Commun., 7;454(1):53-7.
3 Moncada S and Higgs E (2006) Br J Pharmacol