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INRA
24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

Menu Logo Principal logo Université Clermont Auvergne & associés

Human Nutrition Unit

Zone de texte éditable et éditée et rééditée

Lydie COMBARET

Lydie Combaret

 

ORCID: 0000-0001-6550-8700

Tel: +(33)4 73 62 48 24

email: lydie.combaret@inra.fr

 

Understand mechanisms responsible for muscle atrophy during catabolic situations towards efficient prevention/therapeutic strategies

Skeletal muscle is the main reservoir of amino acids that the body can mobilize during catabolic situations to ensure some functions (e.g. immune and inflammatory responses, energy production, and protein synthesis of vital organs ...). However, when this mobilization of amino acids by the muscle is maintained, there is a muscle atrophy, i.e. a loss of muscle mass and strength. The consequences include a weakening of the individuals, which can lead ultimately to bed rest, a lower efficiency of treatments, an increase of the risks of falls and fractures, and consequently a deterioration of the autonomy and the quality of life. In addition, the muscle wasting-associated decrease in physical activity (or even physical inactivity) contributes per se to worsen the muscle atrophy induced by the initial catabolic situation.

Despite this context, there is no strategy for preventive or therapeutic intervention to prevent or counteract muscle atrophy associated with catabolic situations. It is therefore essential to better understand the mechanisms involved in muscle atrophy to propose effective strategies to limit muscle wasting on one hand and to speed-up recovery on the other hand.

Mechanisms invovled in skeletal muscle atrophy during physical inactivity

For several years, we have been focusing our research on the role of the ubiquitin-proteasome and autophagic-lysosomal proteolytic systems mainly involved in the degradation of major contractile proteins and in the control of muscle mass respectively. Our work has contributed to demonstrate their importance in physical inactivity-induced atrophy using immobilization and hindlimb suspension models to simulate microgravity in mice or rats (Refs 1, 4).

Our work also emphasizes the importance of studying muscle adaptations during physical inactivity in different muscle types, as well as taking into consideration the position in which they are immobilized (Refs 2,3,5).

Mechanisms for the maintenance of mitochondrial homeostasis in response to a catabolic situation are currently being investigated, particularly with regard to targeting systems that drive abnormal / damaged mitochondrias to autophagy for their elimination.

Strategies for preserving muscle mass during catabolic situations

Identification of strategies to prevent or counteract muscle protein loss during catabolic situations lies on the identification of mechanisms leading to muscle atrophy. Catabolic situations of physiological (e.g. aging) or pathological (e.g. cancers, sepsis or cast immobilization) origin are often associated with oxidative stress and / or inflammation. This causes an imbalance between proteolysis and protein synthesis and thus contribute to muscle atrophy. We have already shown that antioxidant supplementation speeds up muscle recovery after immobilization (Ref 6, 7).

Our objectives are also to define preventive strategies to allow a better skeletal muscle adaptation when the catabolic situation occurs. For example, the use of n-3 polyunsaturated fatty acid supplementations has increased the intramuscular energy reserves that were then efficiently mobilized by the muscle during an induced catabolic situation, and accordingly preserved muscle mass (Ref 8). Finally, our work is also moving towards preventive multimodal strategies integrating particularly the physical activity component prior to an induced catabolic situation.

 References

  1. Polge et al. Int J Biochem Cell Biol. 2016, 79:488-493.
  2. Slimani et al. J Cachexia Sarcopenia Muscle. 2015, 6:73-83.
  3. Slimani et al. Am J Physiol Endocrinol Metab. 2012, 303:E1335-47.
  4. Magne et al. J Physiol. 2011, 589:511-24.
  5. Vazeille et al. Am J Physiol Endocrinol Metab. 2008, 295:E1181-90. 
  6. Vazeille et al. J Nutr Biochem. 2012, 23:245-51.
  7. Savary-Auzeloux I et al. PLoS One. 2013 8:e81495.
  8. Deval et al. J Cachexia Sarcopenia Muscle. 2016, 7:587-603.

Biography & CV

Pubmed references