Melatonin and neurotrophins NT-3, BDNF, NGF in patients with varying levels of depression severity

Background: Disrupted circadian rhythm of melatonin secretion in depression shows a relationship with the exacerbation of inflammatory processes. Proinflammatory mechanisms of depression are sustained by oxidative stress. This contributes to melatonin deficiency and to the malfunction of the defense mechanisms in the brain. Disrupted melatonin secretion in depression may have an influence on the concentrations of neurotrophic factors (NF), such as neurotrophin-3 (NT-3), brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). Disturbance in neurotrophin release may affect synaptic plasticity and cause exacerbation of neurodegenerative processes in the central nervous system. The aim of this study was to assess the concentrations of melatonin and NF of the brain in patients with varying levels of depression severity. Method: 160 males and females were enrolled in the study, 120 of whom were diagnosed with various types of depression. The control group comprised 40 healthy individuals. At 3:00 a.m. all patients had salivary melatonin concentrations determined utilizing a competitive enzyme immunoassay technique (ELISA). In addition, at 7:00 a.m. all patients had serum neurotrophin (NT-3, BDNF, NGF) concentrations determined by means of ELISA. Results: The highest melatonin secretion was observed at 3:00 a.m. in severely depressed females. In the groups with mild and moderate depression, melatonin secretion at 3:00 a.m. was comparable between males and females. In addition, a decrease in the concentrations of neurotrophins was revealed in patients at all levels of depression severity. Conclusion: Melatonin may be a significant marker of depression severity. Melatonin and NF in depressed patients show neuroprotective effects. (C) 2016 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.