Oral Citrulline Hypothesized to Boost Whole-Body Protein Synthesis by Reducing Leucine Oxidation

Maintaining optimal protein metabolism is crucial for muscle health, recovery, and overall physiological function, particularly in states like aging or recovery from injury. Protein synthesis and breakdown are tightly regulated processes, with amino acids like leucine playing a key role as both a substrate and a signaling molecule. Current strategies to enhance protein synthesis often involve dietary protein intake, but specific amino acid supplementation offers a targeted approach. Citrulline, an amino acid involved in the urea cycle and nitric oxide production, is being investigated for its potential to modulate protein metabolism, offering a novel avenue to support muscle anabolism and reduce catabolism.

This prospective, randomized, double-blind, cross-over study, named 'Citrugrêle', aimed to evaluate the impact of oral citrulline administration on whole-body protein synthesis in healthy human participants. The study design involved assessing protein metabolism in the postabsorptive state. To precisely quantify protein kinetics, an intravenous infusion of stable isotope labeled leucine was utilized. The primary endpoints included changes in leucine oxidation, proteolysis, and overall protein synthesis. The abstract does not specify the exact dose of citrulline administered, the duration of the intervention, or the total number of participants (n).

The abstract for this study, titled 'Citrugrêle', outlines the study's hypothesis and methodology but does not present any specific results or data points from the completed trial. The investigators hypothesize that citrulline supplementation will decrease leucine oxidation without altering proteolysis, and consequently stimulate protein synthesis. This suggests a potential mechanism where citrulline could improve the efficiency of amino acid utilization, leading to a net anabolic effect. No numerical data, statistical significance, or specific findings regarding changes in protein synthesis rates or leucine metabolism are reported in this abstract.