Purpose: Abnormal feeding has been linked to disruptions in brain dopaminergic activity and recent studies have assessed the role of catechol-O-methyltransferase (COMT) in eating disorders. This is the first study to quantify the soluble catechol-O-methyltransferase (S-COMT) activity in erythrocytes from patients with anorexia nervosa (AN), bulimia nervosa (BN) and binge-eating disorder (BED) and the first study at all to evaluate the COMT on patients with BED.
Methods: Forty blood samples from patients with AN, BN and BED and healthy controls were drawn to evaluate S-COMT activity in erythrocytes by high-performance liquid chromatography and mass spectrometry. Since several patients were being treated with fluoxetine 20 mg, they were included in a different group (BN MED and BED MED). Liver homogenates from rats were used to evaluate baseline S-COMT activity in the presence of fluoxetine by the same in vitro procedures and assays.
Results: Erythrocyte S-COMT activity (pmol/mg prt/h) was significantly increased in patients with BN and BED (41.3 ± 6.8 and 41.4 ± 14, respectively) compared to control group (25.3 ± 9.7). In fluoxetine-treated patients with BN, S-COMT activity (15.9 ± 8.8) was decreased compared to the other BN group; however, in BED group, the difference between BED MED and BED was not observed. In patients with AN, no significant difference was found compared to controls.
Conclusion: Patients with BN and BED presented higher S-COMT activity in erythrocytes, which is in agreement with previous studies on the literature addressing the high-activity COMT allele, Val158, as risk factor for eating disorders. Although in fluoxetine-treated patients with BN the activity of S-COMT was similar to the controls, this is not explained by a direct interaction between fluoxetine and S-COMT as verified in in vitro assays.
Keywords: Anorexia nervosa; Binge-eating disorder; Bulimia nervosa; Catechol-O-methyltransferase; Dopamine.