Elevated Plasma Concentrations of Bacterial ClpB Protein in Patients with Eating Disorders

Objective: Caseinolytic protease B (ClpB) produced by Enterobacteria, such as Escherichia coli, has been identified as a conformational mimetic of alpha-melanocyte-stimulating hormone (alpha-MSH), an anorexigenic and anxiogenic neuropeptide. In mice, ClpB induces alpha-MSH cross-reactive antibodies and activates anorexigenic brain neurons. In patients with eating disorders (ED), anti-ClpB and anti-alpha-MSH antibodies correlate with psychopathological traits. However, it is not known if ClpB is present in human plasma including ED patients. Methods: Plasma concentrations of ClpB were measured using a recently developed ClpB immunoassay in female patients with anorexia nervosa, bulimia nervosa, and binge-eating disorder and compared with healthy participants, all characterized by the Eating Disorder Inventory-2 (EDI-2) scale. Results: We found that ClpB was readably detectable in plasma of healthy participants and ED patients and that its concentrations were elevated in ED patients, without significant differences in patient's subgroups. Plasma ClpB concentrations correlated with the EDI-2 scores, with alpha-MSH as well as with plasma levels of anti-ClpB and anti-alpha-MSH antibodies. Discussion: These data revealed that bacterial ClpB is naturally present in human plasma and that its concentrations can be elevated in ED patients and associated with ED-related psychopathological traits. These results support a link between bacterial ClpB and the ED pathophysiology. (C) 2016 Wiley Periodicals, Inc.