A combination of oral L-citrulline and L-arginine improved 10-min full-power cycling test performance in male collegiate soccer players: a randomized crossover trial.

PURPOSE: Oral L-citrulline (Cit) increases plasma L-arginine (Arg) concentration and the production of nitric oxide (NO). NO dilates blood vessels and potentially improves sports performance. The combination of oral Arg and Cit (Arg + Cit) immediately and synergistically increases plasma Arg and nitrite/nitrate (NOx) concentrations more than either Cit or Arg alone. This prompted us to assess the effects of oral Arg + Cit on 10-min cycling performance in a double-blind, randomized, placebo-controlled crossover trial. METHODS: Twenty-four male soccer players ingested either Cit + Arg or placebo (both 1.2 g/day each) for 6 days. On day 7, they ingested Cit + Arg 1 h before performing a 10-min full-power pedaling test on a bicycle ergometer. Plasma NOx and amino acid levels were measured before and after the test, as well as the participants' subjective perception of physical exertion. RESULTS: Power output was significantly greater with Cit + Arg than in the placebo group (242 ± 24 vs. 231 ± 21 W; p < 0.05). Plasma concentrations of post-exercise NOx (p < 0.05), Cit (p < 0.01) and Arg (p < 0.01) were significantly higher in the Cit + Arg than in the placebo group, whereas exercise upregulated plasma NOx concentrations in both groups (p < 0.05). Cit + Arg also gave improved post-exercise subjective perception of "leg muscle soreness" and "ease of pedaling" (both p < 0.05). CONCLUSION: Seven days of oral Citrulline (1.2 g/d) and Arginine (1.2 g/d) ingestion improved 10-min cycling performance and the perception of physical exertion in male collegiate soccer players.

In vitro recapitulation of the urea cycle using murine embryonic stem cell-derived in vitro liver model.

Ammonia, a toxic metabolite, is converted to urea in hepatocytes via the urea cycle, a process necessary for cell/organismal survival. In liver, hepatocytes, polygonal and multipolar structures, have a few sides which face hepatic sinusoids and adjacent hepatocytes to form intercellular bile canaliculi connecting to the ductules. The critical nature of this three-dimensional environment should be related to the maintenance of hepatocyte function such as urea synthesis. Recently, we established an in vitro liver model derived from murine embryonic stem cells, IVL(mES), which included the hepatocyte layer and a surrounding sinusoid vascular-like network. The IVL(mES) culture, where the hepatocyte is polarized in a similar fashion to its in vivo counterpart, could successfully recapitulate in vivo results. L-Ornithine is an intermediate of the urea cycle, but supplemental L-ornithine does not activate the urea cycle in the apolar primary hepatocyte of monolayer culture. In the IVL(mES), supplemental L-ornithine could activate the urea cycle, and also protect against ammonium/alcohol-induced hepatocyte death. While the IVL(mES) displays architectural and functional properties similar to the liver, primary hepatocyte of monolayer culture fail to model critical functional aspects of liver physiology. We propose that the IVL(mES) will represent a useful, humane alternative to animal studies for drug toxicity and mechanistic studies of liver injury.

Ornithine ingestion improved sleep disturbances but was not associated with correction of blood tryptophan ratio in Japanese Antarctica expedition members during summer.

Members of expeditions to Antarctica may show changes in biological and physiological parameters involved in lipid, glucose, and thyroid hormone metabolism as they adapt to the environment; however, alterations in amino acid (AA) levels and sleep among expedition members in Antarctica have yet to be fully elucidated. We hypothesized that there would be alterations of blood AA levels, and ornithine (Orn) ingestion would affect biological parameters and sleep in Japanese expedition members during the summer in Antarctica. Japanese Antarctica Research Expedition members (22 people) who stayed in Antarctica for 3 months from December 2010 were examined, and a randomized double-blind study of Orn ingestion (400 mg/d) for 4 weeks was performed. Sleep conditions were evaluated subjectively by the Oguri-Shirakawa-Azumi (brief version) questionnaire. The blood of Japanese Antarctica Research Expedition members in Antarctica showed higher creatine kinase, lactate dehydrogenase, and ammonia levels than that in Japan. On blood AA analysis, aspartate, Orn, and serine were significantly higher, and alanine and tryptophan (Trp) were significantly lower in Antarctica than in Japan. The Trp ratio, the value of Trp divided by the sum of phenylalanine, tyrosine, and branched-chain AAs, was significantly lower in Antarctica than in Japan. Although sleep deteriorated during the stay in Antarctica, Orn ingestion, to some extent, improved sleep compared with the placebo group in Antarctica, suggesting that Orn is effective for people with heavy physical workloads in places such as Antarctica.