Abstract
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Objectives Previous studies have demonstrated that there was an association between the cortisol and serotonin transporter (SERT) availability in both healthy subjects and patients with major depressive disorder (MDD). The aim of this study was to assess if this association could be replicated in bipolar disorder (BD). Furthermore, a second biomarker, brain derived neurotrophic factor (BDNF), was also inserted into the regression model to test the role of BDNF on SERT availability in BD.
Methods Twenty-eight BD I euthymic patients and 28 sex- age- matched controls were recruited. 123I-ADAM with single photon emission computed tomography (SPECT) was applied for the measurement of the SERT availability. Ten ml venous blood was withdrawn when the subject underwent SPECT measurement. Simple ratio method was used for derivation of the SERT availability.
Results There was a significant decreased in SERT availability in patients compared with controls (2.4±0.6 vs. 2.9±0.7, p=0.002), whereas the cortisol and BDNF was not different between patients and controls. Regression model showed that the SERT availability can be explained by cortisol but not by BDNF and their interaction in controls (whole model: R square=0.19, p=0.02, cortisol: β=0.64, p=0.013, BDNF: β=0.22, p=0.418, Cortisol*BDNF: β=0.39, p=0.158).
Conclusions Notably, the finding cannot be found in BD patients. The current results imply that the role of cortisol in regulating SERT availability is different between MDD and BD.