Serum TNF- Related Weak Inducer of Apoptosis (TWEAK), TNF- Related Apoptosis-Inducing Ligand (TRAIL) Levels in Patients with Bipolar Depression, Major Depression and a Healthy Control Group.

BACKGROUND A low-grade inflammation is presumed to be related to the etiopathogenesis of major depressive disorder (MDD) and bipolar disorder. Tumor necrosis factor (TNF) superfamily members have roles in the pathogenesis of neuropsychiatric disorders because of the relationship with inflammation and neurogenesis. The aim of this study was to investigate the serum TNF-related weak inducer of apoptosis (TWEAK) and TNF-related apoptosis-inducing ligand (TRAIL) levels in patients with bipolar depression (BD), MDD and a healthy control (HC) group to determine any differences between MDD and BD in terms of inflammation biomarkers. SUBJECTS AND METHODS After a 12-hour overnight fast, 5 milliliter (mL) samples of fasting blood were obtained from the participants. The TWEAK and TRAIL plasma levels were calculated using ELISA kits. RESULTS The TWEAK levels were found to be higher in the BD group than in the HC group (p=0.03). No statistically significant differences were determined between the BD vs MDD and MDD vs HC groups (p=0.17, p=0.37, respectively). There were no statistically significant differences between the three groups (BD vs HC; BD vs MDD; MDD vs HC) in terms of TRAIL levels (p=0.21). CONCLUSION To the best of our knowledge, this study is the first to have explored TWEAK levels in patients with BD. The higher TWEAK levels in BD than in the control group is compatible with the inflammation hypothesis of BD. Limitations of the study were the differences in medications of the patient groups and that it was a cross-sectional study. There is a need for further longitudinal studies with larger sample size and medication-free patients.