Author(s): YAMADA, K., MATSUDAIRA, H.1, IDE, D.1, IWATA, Y.1, TAKEHARA, K.1, HAGINO, Y.1, SATO, T.1, ITO, R.1, MIYAZAKI, M.2, TSUDA, T.1, ITOH, H.1, Institution: NAGOYA INSTITUTE OF TECHNOLOGY, Country: JAPAN, Abstract-ID: 779

INTRODUCTION:
Oral L-arginine and L-citrulline supplementation immediately and synergistically increases plasma arginine and nitrite/nitrate (NOx) concentrations, therefore, during exercise arginine-citrulline increase blood flow in muscle tissues, muscle energy metabolism, mitochondrial respiration due to increased nitric oxide (NO) bioavailability (1). On the other hand, it is known that ketones (β-hydroxybutyrate, acetoacetate and acetone) are generated in mitochondria of the liver, mainly from the oxidation of fatty acids, and are exported to peripheral tissues, such as the brain, heart, kidney, and skeletal muscle for use as energy fuels (2). Therefore, previously studies demonstrated that exercise increased ketone levels in plasma (3), expired air (4) and skin-gas acetone concentration (4, 5). However, no one has reported whether arginine-citrulline supplementation would incresse blood ketone bodies and skin-gas acetone concentration during exercise or not. The present study demonstrated the effect of arginine-citrulline supplementation on blood ketone bodies and skin-gas acetone concentration following maximal running exercise.

METHODS:
A double-blind randomized placebo-controlled 2-way crossover study was employed. Ten healthy male students (23.0 ± 1.5 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. Acetone concentration was analyzed by gas chromatography. Blood flow measured using a laser tissue blood flow meter (Omegaflo, Omega Wave, Japan). Blood samples were obtained from fingertip to measure β-hydroxybutyrate and glucose using Stat strips XP3 (NIPRO, Co., Ltd., Japan).

RESULTS:
The arginine-citrulline supplement significantly (p<0.01) increased running time and distance compared to the placebo. Significant higher levels were observed in blood flow (p<0.001), blood β-hydroxybutyrate (p<0.05) and skin-gas acetone concentrations (p<0.001) following the maximal exercise.

CONCLUSION:
Significantly higher levels of ketone bodies in blood and skin-gas acetone concentration have indicated that the arginine-citrulline supplement increased acetone production in mitochondria of the liver during the maximal exercise. These results suggest that increased NO bioavailability by the arginine-citrulline supplement improved not only blood flow in muscle tissues, muscle energy metabolism, and mitochondrial respiration, but also ketone production in the liver.