Clinical analysis of selected complement-derived molecules in human adipose tissue

BACKGROUND: It has been suggested that action of complement cascade [CC]-derived anaphylatoxins/molecules may represent a missing link between obesity and metabolic disorders. However, to date, the direct biochemical/immunomodulatory composition of the human AT environment remains poorly understood. In this study, we examined plasma and AT (subcutaneous and visceral/omental) levels of selected CC-derived anaphylatoxins/molecules, and adipsin as well as verified their associations with immune and stem cells chemoattractant - stromal-derived factor-1 (SDF-1). METHODS: A total of 70 (35 subcutaneous and 35 omental) AT samples were obtained from patients undergoing elective surgery. Plasma and AT-derived interstitial fluid levels of C3a, C5a, C5b-9/membrane attack complex (MAC), complement factor D (adipsin) were measured using ELISA. RESULTS: AT levels of all examined substances were significantly lower than the corresponding levels in the plasma (in all cases P < 0.0000001). Moreover, in subcutaneous AT, robust C3a and adipsin concentrations were observed, whereas high levels of C5b-9/MAC were detected in the visceral depots. In addition, we established the correlations between analyzed molecular substances and body composition, BMI and/or the adiposity index of the examined patients. CONCLUSIONS: Our study demonstrated for the first time that significantly reduced levels of complement-derived molecules were present in human AT than in the peripheral blood, and that these factors are associated with the metabolic status of examined individuals. Moreover, in human AT, various associations between complement-derived molecules and SDF-1 levels exist.