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Atrophie et récupération musculaire chez le rat âgé Immobilisé : Rôle de la nutrition

Abstract : Sarcopenia, the age-related muscle mass loss, might be partially explained by an impaired muscle mass recovery of skeletal muscle mass after a catabolic state. Thus, immobilization periods which increase with aging could induce a muscle atrophy followed by a lack of muscle mass recovery. An imbalance of protein and cellular metabolisms are certainly involved in this absence of recovery. The aim on this Ph.D thesis was to explore the mechanisms involved in muscle mass atrophy during immobilization and their possible alteration during the recovery period in old rats. Old rats were immobilized for 8 days by unilateral hind limb casting and then allowed to recover for 40 days. Our results showed that animals fed a 13% casein diet wasted muscle mass in immobilized muscles but, contrarily to adult animals, they never recovered the muscle mass loss. Muscle atrophy was due to 1/ an increase of apoptotic and ubiquitine-proteasome-dependent proteolytic pathways, 2/ a decrease of muscle regeneration processes and 3/ a decrease of muscle protein synthesis at the fed state. These changes paralleled an increase of intracellular inflammation and oxidative stress. As these parameters were only normalized during the recovery period, the resultant nitrogen balance was then not enough positive as required for the muscle protein gain, hence contributing to the age-related incomplete muscle mass recovery. We tested free leucine supplementation (an amino acid known for its stimulatory effect on protein metabolism) during there covery period to improve muscle mass gain. This supplementation induced a greater muscle protein synthesis in supplemented animals, but without any muscle mass gain. However, we demonstrated here for the first time that muscle protein accretion after immobilization-induced atrophy could be achieved with whey protein or high protein diets. In conclusion, we demonstrated that immobilization in old rats induced a muscle mass atrophy followed by an incomplete recovery, hence contributing to the development of sarcopenia. We also demonstrated that this lack of recovery cannot be overcome by a dietary free leucine supplementation, despite a positive effect on protein metabolism, contrarily to high protein and whey protein diets.
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  • HAL Id : tel-02811469, version 1
  • PRODINRA : 181166



Hugues Magne. Atrophie et récupération musculaire chez le rat âgé Immobilisé : Rôle de la nutrition. Alimentation et Nutrition. Université Blaise Pascal (Clermont Ferrand 2), 2011. Français. ⟨tel-02811469⟩



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