Citrulline: stimulates muscle protein synthesis
Rationale:
Amino acid (AA) availability is a key factor that determines protein balance and therefore when protein intake is low, muscle protein synthesis is reduced. Citrulline (CIT) is a non-protein AA which was considered solely as a metabolic product of arginine and therefore was greatly underestimated. Recent experimental studies demonstrated that CIT is a key stimulant of muscle protein synthesis in malnourished rats. The current study was designed to determine whether citrulline stimulates whole body and muscle protein synthesis in healthy adults submitted to a low-protein diet
Methods:
10 healthy participants were recruited in this cross-over study. After 3-days of low-protein intakes, either a CIT or an isonitrogenous non-essential AA mixture (NEAA, control group) was given orally as small boluses every 30 min from T0 to T480 min. A primed continuous intravenous infusion of [ring-13C6] phenylalanine and of [N15] tyrosine was administered as tracers. Muscle biopsies were taken at T180 and T480 min. Blood samples were taken every hour to measure tracer enrichment, insulin and AA levels
Results :
Conclusion:
We show for the first time that, in healthy subjects on low protein intake, citrulline ingestion stimulates muscle protein synthesis without affecting whole-body protein turnover. This anabolic action of citrulline appears to be independant of insulin action and may be of potential value in treating conditions associated with low protein absorption.
Scientific publication : Jourdan M, Nair KS, Ford C, Shimke J, Ali B, Will B, et al. Citrulline stimulates muscle protein synthésis at the post-absorptive state in healthy subjects fed a low protein diet. Clinical Nutrition 2008; 3 Supplement 1: 11-2
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