Serum brain-derived neurotrophic factor and peripheral indicators of the serotonin system in underweight and weight-recovered adolescent girls and women with anorexia nervosa

Background: Brain-derived neurotrophic factor (BDNF) mutant mice show hyperphagia and hyperleptinemia. Animal and cell-culture experiments suggest multiple interrelations between BDNF and the serotonin (5-HT) system. We studied serum BDNF in patients with anorexia nervosa and its associations with peripheral indicators of the 5-HT system. To control for secondary effects of acute malnutrition, we assessed acutely underweight patients with anorexia nervosa (acAN) in comparison to long-term weight-recovered patients with the disorder (recAN) and healthy controls. Methods: We determined serum BDNF, platelet 5-HT content and platelet 5-HT uptake in 33 patients in the acAN group, 20 patients in the recAN group and 33 controls. Plasma leptin served as an indicator of malnutrition. Results: Patients in the acAN group were aged 14–29 years and had a mean body mass index (BMI) of 14.9 (standard deviation [SD] 1.4) kg/m 2 . Those in the recAN group were aged 15–29 years and had a mean BMI of 20.5 (SD 1.3) kg/m 2 and the controls were aged 15–26 years and had a BMI of 21.4 (SD 2.1) kg/m 2 . The mean serum BDNF levels were significantly increased in the recAN group compared with the acAN group (8820, SD 3074 v. 6161, SD 2885 pg/mL, U = 154.5, p = 0.001). There were no significant associations between BDNF and either platelet 5-HT content or platelet 5-HT uptake. Among patients with anorexia nervosa, we found significant positive linear relations between BDNF and BMI ( r = 0.312, p = 0.023) and between BDNF and leptin ( r = 0.365, p = 0.016). Limitations: We measured the signal proteins under study in peripheral blood. Conclusion: Serum BDNF levels in patients with anorexia nervosa depend on the state of illness and the degree of hypoleptinemia. Upregulation of BDNF in weight-recovered patients with anorexia nervosa could be part of a regenerative process after biochemical and molecular neuronal injury due to prolonged malnutrition. Associations between the BDNF and the 5-HT system in humans remain to be established.