BACKGROUND: Proteolyse is one of the causes of loss of lean body mass, and depend of insulin. Proteintyrosine phosphatase 1B (PTP1B) and intestinal permeability (evaluated by zonulin) contribute of insulin metabolism. The objectives were to explore the relationship between PTP1B, Zonulin level and body composition during septic shock in humans. MATERIAL AND METHODS: Prospective study including patients admitted to intensive care unit (ICU) for septic shock. Blood samples were collected on days 1 (D1) and 4 (D4) for study expression of PTPT1b (PCR) and zonulin. Muscle mass was evaluated by Fat-Free Mass (FFM) (by Bioelectrical impedance analysis) and rectum femoris cross-sectional area by ultrasound. RESULTS: We included 52 patients with a mean IGSII 53 [39-65], and a mortality in ICU of 32%. Between D1 and D4, aera of right quadriceps muscle (ARQ) and average of quadriceps muscles (AAQ) decreased (p = 0.002 and 0.009 respectively). We observed no modification in FFM. Median of PTP1b at D1 was 5.03 [2.36-10.96]. Median of plasmatic zonulin at D1 was 156.6 ng/ml [56.3-277.9]. We did not find any correlation between PTP1b, zonulin expression and muscle composition. The mortality rate was more important in patients with a low average quadriceps thickness (QT) or quadriceps area (QA) (p <
0.01), and tendency for patients who had an elevated zonulin in admission. By contrast, we did not observe significant associations between fat-free mass and PTP1B and mortality at D28. CONCLUSION: We observed a trend of correlation between the whole blood PTPN1 gene expression at D1 and D4/D1 TLQ, because this is the only data which has a potential to address the relationship body mass change and proteolysis.Keys words: Body composition, malnutrition, PTB1B, septic shock, Zonulin.