Long‐term effect of citrulline supplementation in healthy aged rats: effect on body composition

Rationale Aging is associated with a decrease in muscle mass. Citrulline (CIT) increases muscle protein synthesis. The aim of this work was to evaluate the long‐term effect of CIT supplementation on body composition in healthy aged rats. Methods 20‐month‐old male Sprague‐Dawley rats (n=20) were randomized to be fed with chow diet or CIT‐enriched diet (1 g.kg‐1.d‐1) for 12 weeks. At sacrifice, rats were dissected and we weighed lean body mass, intra‐abdominal fat mass and cutaneous fat mass. Muscles were removed and weighed; muscle protein content was measured. Statistics Student t‐test. Results The mortality over 12 weeks was 20% (4/20) in the NEAA group whereas no mortality was observed in the CIT group (p=0.05). CIT did not affect body weight, but increased muscle weight (tibialis p=0.04 and plantaris p=0.02) and muscle protein content in the tibialis (195±4 vs 183±5 mg/g of muscle for CIT and NEAA; p=0.04). CIT induced a change in body composition with a decrease in cutaneous fat mass (24.7±0.5 vs 28.6±0.7 % of total body weight for CIT and NEAA, p=0.002) and intra‐abdominal fat mass (3.6±0.2 vs 5.1±0.3 %, p=0.0001) and an increase in lean body mass (54.8±0.6 vs 50.2±0.8 %, p<0.0001). Conclusion CIT supplementation is safe and is able to increase lean body mass and decrease fat mass in healthy aged rats. This is the first time that a nutritional manipulation induces such a change in body composition in aged rats.