Muscle mass results from a balance between the pathway of proteolysis and that of protein synthesis, depending on many factors, not one of the most important are insulin. The protein PTP1B (Protein Tyrosine Phosphatase 1B), by the dephosphorylation of its numerous substrates, constitutes an endogenous regulator of numerous intracellular signaling pathways, including that of insulin. PTP1B could play a role in the protein synthesis abnormalities observed during sepsis leading clinically to impaired body composition including muscle body mass. Therefore, we propose to study the association between PTP1B and loss of muscle mass in patients in sepsis in resuscitation.