After receiving a 7-day oral supplementation with citrulline, each subject will be admitted to the Clinical Investigation Unit for a half day, after an overnight fast,and will receive a 5-h intravenous infusion of L-[1-13C]leucine (i.e.; leucine labeled with 13C, a stable isotope of carbon) from 8 am to 1 pm. At regular intervals throughout the isotope infusion, blood will be obtained to measure 13C-enrichment in plasma a-keto-isocaproate, the keto acid of leucine, using gas chromatography-mas spectrometry. Simultaneously, 13C-enrichment will be measured in aliquots of expired air CO2 using isotope ratio mass spectrometry, and total CO2 production (VCO2) will be measured using direct calorimetry, respectively. The subject will then leave the hospital, take no treatment for13 days (wash-out period). The study will then be repeated a second time in an identical fashion, after a second 7-day period of oral supplementation with placebo, as a cross-over study design will be used.

After receiving a 7-day oral supplementation with placebo, each subject will be admitted to the Clinical Investigation Unit for a half day, after an overnight fast,and will receive a 5-h intravenous infusion of L-[1-13C]leucine (i.e.; leucine labeled with 13C, a stable isotope of carbon) from 8 am to 1 pm. At regular intervals throughout the isotope infusion, blood will be obtained to measure 13C-enrichment in plasma a-keto-isocaproate, the keto acid of leucine, using gas chromatography-mas spectrometry. Simultaneously, 13C-enrichment will be measured in aliquots of expired air CO2 using isotope ratio mass spectrometry, and total CO2 production (VCO2) will be measured using direct calorimetry, respectively. The subject will then leave the hospital, take no treatment for13 days (wash-out period). The study will then be repeated a second time in an identical fashion, after a second 7-day period of oral supplementation with citrulline, as a cross-over study design will be used.

0.06 G/kg three times/day during 7 days