Introduction: Central serotonergic pathways may play an important role in the etiology of anorexia nervosa (AN). Although platelet monoamine oxidase activity (MAO-B) has been proposed as an index of cerebral serotonin activity, studies in patients with AN are scarce.
Methods: Platelet MAO-B activity was determined in 59 acutely underweight AN patients (acAN, aged 14-29 years, BMI=15.2+/-1.4), 35 weight-recovered AN patients (recAN, aged 15-29, BMI=20.8+/-2.2) and 59 healthy control women (HCW, aged 14-26, BMI=21.6+/-2.1). Plasma leptin served as an indicator of malnutrition. Results were compared by ANCOVA controlling for confounding variables.
Results: Platelet MAO-B activity in acAN patients (5.2+/-1.4 nmol/10 (9)pltx15 min) was similar to HCW (5.5+/-1.9) but significantly lower in recAN patients (4.4+/-1.5). BMI and leptin showed a significant negative correlation with MAO-B activity in AN patients, but not in HCW.
Discussion: Our results highlight the importance of malnutrition for the interpretation of abnormalities in neurotransmitter systems in AN. Whether low MAO-B activity in weight-recovered AN patients indicates a premorbid trait or a secondary change due to recovery remains to be elucidated.