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 numer ous immunological and metabolic activities. In addition, TNF-alpha can stim ulate a variety of physiological, neuroendocrine and behavioural responses of the central nervous system. In experimental animals, TNF-alpha induces c hanges in physiological and behavioural parameters which have also been obs erved in eating disorders. The biological activities of TNF-alpha are media ted by two structurally related, but functionally distinct receptors, TNF-R I and TNF-RH. Since injection of TNF-alpha results in increased shedding of TNF-alpha receptors, it is likely that TNF-alpha release is reflected by s oluble 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 immuno assay kit and plasma concentrations of sTNF-RI and sTNF-RII were measured b y enzyme-linked immunosorbent assay. RESULTS Plasma TNF-alpha concentration s 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 conc entrations 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 w ere 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 patien ts. However, plasma TNF-alpha concentrations were not related to body fat m ass 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 kineti cs compared with sTNF-RI in bulimic patients.