Increased availability of leucine with leucine-rich whey proteins improves postprandial muscle protein synthesis in aging rats

Isabelle Rieu (1, 2) , Michelle M. Balage (1, 2) , Claire Sornet (1, 2) , Elisabeth Debras (1, 2) , Sandrine Ripes (1, 2) , Cécile Rochon-Bonhomme (3) , Corinne Pouyet (1, 2) , Jean Grizard (1, 2) , Dominique Dardevet (1, 2)

1 UNH - Unité de Nutrition Humaine
2 Centre de Recherche en Nutrition Humaine
3 Groupe Lactalis

OBJECTIVE: We previously found that aging was characterized by a decreased sensitivity of muscle protein synthesis to leucine and that a free leucine-supplemented diet corrected this defect in old rats and elderly humans. The present experiment was undertaken to evaluate the efficiency of selected leucine-rich proteins to stimulate postprandial muscle protein synthesis in old rats to optimize nutritional protein support in the elderly. METHODS: Sixty rats (22 mo old) received an experimental meal for the first hour of feeding and a standard diet for the rest of the day for 30 d. Experimental meals contained milk proteins that differed in leucine content: beta-lactoglobulin (14.5% leucine), Prolacta (13.4%), alpha-lactalbumin (10.9%), and casein (10%). As a control, a fifth group was added that received herring flour protein (7.3% leucine). Muscle protein synthesis was determined in vivo in the postprandial state at the end of the 30-d nutritional period using the flooding dose method (1-(13)C phenylalanine). RESULTS: Leucine intake and plasma leucine concentrations were significantly increased in rats fed meals containing the leucine-rich proteins (i.e., beta-lactoglobulin and Prolacta). As previously observed with free leucine-supplemented meals, postprandial muscle protein synthesis was significantly improved in rats fed the meals containing the leucine-rich proteins. Interestingly, the beneficial effect was maintained after the 30-d supplementation. CONCLUSION: The results indicated that leucine-rich proteins were efficient in improving muscle protein synthesis in old rats. Thus, nutritional supplements containing such proteins may be efficient in preventing sarcopenia in the elderly and would represent a safe and optimized nutritional strategy. However, further experiments are necessary to determine the duration of such nutritional support to obtain a significant protein gain in muscle.

Mots clés: AGING; WHEY PROTEIN; RAT

Mots clés: MUSCLE PROTEIN SYNTHESIS; LEUCINE-RICH PROTEIN

Domaines: Sciences du Vivant [q-bio]

Isabelle Rieu, Michelle M. Balage, Claire Sornet, Elisabeth Debras, Sandrine Ripes, et al.. Increased availability of leucine with leucine-rich whey proteins improves postprandial muscle protein synthesis in aging rats. Nutrition, 2007, 23 (4), pp.323-331. ⟨10.1016/j.nut.2006.12.013⟩. ⟨hal-02666502⟩