Many physiopathological situations (aging, obesity and other chronic diseases) are associated with muscle alterations. Depending on the circumstances, they affect both muscle mass and function and result in a reduction in mobility, which can affect people's quality of life and health. Thus, identifying the factors responsible for these muscle alterations is necessary in order to define ways to preserve muscle mass and function, thus ensuring the maintenance of health and quality of life in elderly people or those with chronic diseases. Among the mechanisms involved in the loss of muscle mass and function, postprandial anabolic resistance of muscle protein metabolism has been well demonstrated in elderly animals and humans, linked in particular to the development of insulin resistance during aging. In a more general concept, insulin resistance, observed in many clinical contexts, could be considered as a contributor to muscle wasting.

Research Activities

Evolution of muscle mass and muscle protein metabolism during obesity: effect of exercise and lipid restriction.
The onset of obesity in rats fed a high-fat, high-calorie diet occurs in two phases: a dynamic phase of weight gain during the first 16 weeks of the diet, during which muscle mass increases, followed by a static phase, from 16 to 24 weeks of the diet, during which weight stabilizes and muscle mass decreases. During the weight gain phase, the rate of muscle protein synthesis increases in muscles with glycolytic metabolism. Conversely, during the weight stability phase, the rate of muscle protein synthesis decreases in these same muscles. The changes observed in glycolytic muscles during the static phase of obesity are associated with a significant accumulation of intramuscular lipids. The second part of this study demonstrated that, after a period of obesity, endurance exercise combined with a balanced-fat diet is associated with greater weight loss than exercise or diet alone. Furthermore, this strategy also appears to be beneficial for muscles, as it improves obesity-induced changes in muscle mass and protein metabolism.
Skeletal muscle mass and quality are affected differently during the onset of obesity and during weight loss. The biochemical and molecular mechanisms governing these variations remain to be demonstrated in order to define effective nutritional or therapeutic strategies to limit the quantitative and qualitative loss of muscle, particularly during highly restrictive diets and/or surgical treatments for obesity.

Most notable publications

• Guillet C, Masgrau A, Walrand S, Boirie Y. Impaired protein metabolism: interlinks between obesity, insulin resistance and inflammation. Obes Rev. 2012 Dec;13 Suppl 2:51-7.
• Masgrau A, Mishellany-Dutour A, Murakami H, Beaufrère AM, Walrand S, Giraudet C, Migné C, Gerbaix M, Metz L, Courteix D, Guillet C, Boirie Y. Time-course changes of muscle protein synthesis associated with obesity-induced lipotoxicity. J Physiol. 2012 Oct 15;590(Pt 20):5199-210.
• Guillet C, Delcourt I, Rance M, Giraudet C, Walrand S, Bedu M, Duche P, Boirie Y. Changes in basal and insulin and amino acid response of whole body and skeletal muscle proteins in obese men. 2009. J Clin Endocrinol Metab. 94(8):3044-50.
• Guillet C, Zangarelli A, Gachon P, Morio B, Giraudet C, Rousset P, Boirie Y. Whole body protein breakdown is less inhibited by insulin, but still responsive to amino acid, in nondiabetic elderly subjects. 2004. J Clin Endocrinol Metab. 89(12):6017-24.
• Guillet C, Prod'homme M, Balage M, Gachon P, Giraudet C, Morin L, Grizard J, Boirie Y. Impaired anabolic response of muscle protein synthesis is associated with S6K1 dysregulation in elderly humans. 2004. FASEB J. 18(13):1586-7.
   

Other links

ASMS

https://www.linkedin.com/in/christelle-guillet-2813874/