Plasma concentrations of tumor necrosis factor-alpha (TNF-alpha) and soluble TNF receptors in patients with bulimia nervosa

BACKGROUND: Tumor necrosis factor-alpha (TNF-alpha) is a cytokine with numerous immunological and metabolic activities. In addition, TNF-alpha can stimulate a variety of physiological, neuroendocrine and behavioural responses of the central nervous system. In experimental animals, TNF-alpha induces changes in physiological and behavioural parameters which have also been observed in eating disorders. The biological activities of TNF-alpha are mediated by two structurally related, but functionally distinct receptors, TNF-RI and TNF-RII. Since injection of TNF-alpha results in increased shedding of TNF-alpha receptors, it is likely that TNF-alpha release is reflected by soluble TNF-receptors (sTNF-Rs) levels. AIMS: We studied plasma concentrations of TNF-alpha and two sTNF-Rs (sTNF-RI and sTNF-RII) in female patients with bulimia nervosa. DESIGN AND PATIENTS: Twenty female patients with bulimia nervosa (BN) and 20 age-matched normal women (N) were studied. MEASUREMENTS: Plasma TNF-alpha concentrations were measured by enzyme immunoassay kit and plasma concentrations of sTNF-RI and sTNF-RII were measured by enzyme-linked immunosorbent assay. RESULTS: Plasma TNF-alpha concentrations in BN were significantly higher than those in N (4.7+/- 0.5 ng/l vs. 1.6+/-0.1 ng/l; P<0.01). Although no significant difference was observed in plasma sTNF-RI concentrations between the two groups, plasma sTNF-RII concentrations in BN were significantly higher than those in N (2080.0+/-107.5 ng/l vs. 1569.5 +/-84.0 ng/l; P<0.01). Plasma TNF-alpha concentrations were significantly related to plasma sTNF-RI concentrations (r = 0.511, P<0.05) and to plasma sTNF-RII concentrations (r = 0.532, P<0.05) in bulimic patients. However, plasma TNF-alpha concentrations were not related to body fat mass or to bulimic behaviours in these patients. CONCLUSIONS: Our present findings suggest that the adipose tissue may not be the immediate source of TNF-alpha in bulimic patients but the increase in plasma TNF-alpha in these patients may be derived from the central nervous system sources. The elevated sTNF-RII may reflect different shedding kinetics compared with sTNF-RI in bulimic patients.