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Last update: May 2021

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Human Nutrition Unit

Zone de texte éditable et éditée et rééditée

Séphane WALRAND, PhD

Activities

Email: contact
Tél: +33(0)4 73 60 82 76

Stéphane Walrand

Sarcopenia is defined as the decline of skeletal muscle mass and function with age. Muscle loss is accompanied by a reduction in muscle strength and, therefore, contributes to the loss of mobility and independence and the elevated risk of falls in the elderly. Muscle is a pool of amino acids mobilized in pathological conditions. Hence, sarcopenia reduces the capacity to accommodate with environmental stress (bacterial infection, inflammation, denutrition...). Muscle loss related to age also contributes to the reduction of physical activity and thus to the development of obesity, insulin resistance and osteoporosis as we age.

Sarcopenia results from a net protein loss, i.e. an imbalanced rate of synthesis and degradation of muscle proteins. A well-known resistance to anabolic factors appears, in particular a resistance to the postprandial stimulation of muscle protein synthesis. Physiologically, during the postabsorptive periods, the balance between protein synthesis and degradation is negative and causes a net protein loss which is normally compensated by a net protein gain in response to food intake, i.e. anabolic period characterized by a positive balance between protein synthesis and degradation. The alternation between periods of protein catabolism and protein anabolism allows to maintain protein homeostasis. However, in older people, the reduced muscle protein mass results from an imbalance between protein synthesis and degradation that appears during the postprandial period. The protein gain after meal intake no longer compensates the losses of the fasting period and the resulting permanent imbalance ultimately contribute to a quantitative and qualitative progressive loss of proteins.

Research Activities

The global aim is to study the effects of diet on protein-energy metabolism and functional capacity (contractile and metabolic) of skeletal muscle during aging. In addition to dietary proteins, a central postprandial regulator of protein metabolism, we are interested in the effect of the food matrix, i.e. the potential permissive or inhibitive of nutrients accompanying proteins in food. Until very recently, it was stated that postprandial protein anabolism was mainly regulated by amino acids. New clinical and pre-clinical studies have shown, however, that apart from dietary proteins, other nutrients are involved, specifically or in conjunction with amino acids, to positively (vitamin D, oleate, polyunsaturated fatty acids) or negatively (palmitate) regulate muscle anabolism. It should be noted that advancing age is characterized by a deregulation of muscle capacity to adapt to these nutrient signals, partly contributing to the development of sarcopenia. My current and future research topics are therefore concerned with the quality of dietary protein together with the action of nutrients known as key controllers of protein metabolism, with a specific focus on food matrices conducive to muscle protein anabolism. In this context, although animal products are recognized as valuable protein sources for sarcopenic subjects, a new role have to be set for plant foods considering their nutritional characteristics and durability. Therefore, the interest of plant products containing a large amount of proteins (legumes, cereals, grains) and of specific processing methods (inclusion in pasta, in dairy products...) for maintaining muscle mass and contractile function in older poeple is being evaluated.

Publications

  • Walrand S, Gryson C, Salles J, Giraudet C, Migné C, Bonhomme C, Le Ruyet P, Boirie Y. Fast-digestive protein supplement for ten days overcomes muscle anabolic resistance in healthy elderly men. Clin Nutr. 2015 May 8. In press.
  • Gryson C, Ratel S, Rance M, Penando S, Bonhomme C, Le Ruyet P, Duclos M, Boirie Y, Walrand S. Four-month course of soluble milk proteins interacts with exercise to improve muscle strength and delay fatigue in elderly subjects. J Am Med Dir Assoc. 2014 Dec;15(12):958.e1-9.
  • Tardif N, Salles J, Guillet C, Tordjman J, Reggio S, Landrier JF, Giraudet C, Patrac V, Bertrand-Michel J, Migne C, Collin ML, Chardigny JM, Boirie Y, Walrand S. Muscle ectopic fat deposition contributes to anabolic resistance in obese sarcopenic old rats through eIF2α activation. Aging Cell. 2014 Dec;13(6):1001-11.
  • Walrand S, Short KR, Heemstra LA, Novak CM, Levine JA, Coenen-Schimke JM, Nair KS. Altered regulation of energy homeostasis in older rats in response to thyroid hormone administration. FASEB J. 2014 Mar;28(3):1499-510.
  • Salles J, Chanet A, Giraudet C, Patrac V, Pierre P, Jourdan M, Luiking YC, Verlaan S, Migné C, Boirie Y, Walrand S. 1,25(OH)2-vitamin D3 enhances the stimulating effect of leucine and insulin on protein synthesis rate through Akt/PKB and mTOR mediated pathways in murine C2C12 skeletal myotubes. Mol Nutr Food Res. 2013 Dec;57(12):2137-46.
  • Salles J, Tardif N, Landrier JF, Mothe-Satney I, Guillet C, Boue-Vaysse C, Combaret L, Giraudet C, Patrac V, Bertrand-Michel J, Denis P, Chardigny JM, Boirie Y, Walrand S. TNFα gene knockout differentially affects lipid deposition in liver and skeletal muscle of high-fat-diet mice. J Nutr Biochem. 2012 Dec;23(12):1685-93.

Curriculum Vitae

Degrees:
-PhD in Applied Biology (2000) - specialization in Human Nutrition and Aging
-Post doctoral position: Laboratory of Molecular Endocrinology, Bratislava, Slovak Republic (2002)
-Post doctoral position: Endocrine Research Unit, Mayo Clinic and Foundation, Rochester, MN, USA (2004-2005)
-Certified to perform procedures (2002) and surgery (2008) on live animals
-Certified to supervise Research in Nutrition and Food Science (2004)
Activity of expertise:
-Member of the Scientific Committee of French Society for Clinical Nutrition (since 2011)
-Scientific Expert for the French Agency for Food, Environmental and Occupational Health & Safety (ANSES, since 2012)
-Reviewing experience:
125 articles since 2000
Publications:     
-Author and co-author of over 70 original articles, 15 invited reviews, 10 book chapters, 2 patents, 125 communications  in national and international congresses
-30 invited lectures
Teaching experience and student supervision:    
-Courses on Human Nutrition Sciences and Metabolism (Master Degree, 20h/y since 2000)
-Supervision of 16 graduate students (Master Degree and PhD students)
Coordination of contracts:
Coordinator or co-coordinator of research programs supported by the National Research Agency (ANR), INSERM, Europe or private companies (Danone, Sanofi, Nutricia, Lactalis, Cosucra, Lesieur).
 fonds privés (Danone, Sanofi, Nutricia, Lactalis, Cosucra, Lesieur).