Increased inflammation and lower platelet 5-HT in depression with metabolic syndrome.

BACKGROUND: Recent studies suggest comorbidity between major depressive disorder (MDD) and metabolic syndrome. For both disorders, impaired serotoninergic neurotransmission and inflammatory factors have been suggested. The objective of this study was to investigate the concentration of platelet serotonin, interleukin-6 (IL-6) and C-reactive protein (CRP) in MDD patients with and without metabolic syndrome. The second goal was to investigate the association of the concentrations of platelet serotonin, IL-6 and CRP with individual components of metabolic syndrome in MDD patients.
METHODS: A total of 145 MDD patients were included in the study (diagnosed according DSM IV TR criteria). The metabolic syndrome was defined according to the criteria of the American National Cholesterol Education Program-Treatment Panel III (ATP III). Inflammation factors (IL-6 and CRP) and platelet serotonin concentration were assessed by the enzyme-linked immunosorbent assay (ELISA).
RESULTS: MDD patients with metabolic syndrome showed lower platelet serotonin and higher IL-6 and CRP concentrations when compared to MDD patients without metabolic syndrome. An inverse correlation was found between platelet serotonin and waist circumference and serum glucose levels. A positive correlation was found between IL-6 and glucose or triglyceride concentrations, while the correlation with HDL cholesterol was negative. LIMITATIONS: Data on dietary habits or physical activity prior to hospitalisation were not collected. Also, the study was a cross-sectional without a prospective design.
CONCLUSION: Metabolic syndrome in patients with MDD may be associated with reduced concentrations of platelet serotonin and increased concentrations of IL-6 and CRP.