PS189. Post-transcriptional processes in the main serotonin degrading enzyme MAO-A in the adult human brain investigated in vivo with PET and postmortem data

Background: The relationship between functional changes in brain and therapeutic efficacy remains an intriguing field of research in depression. Emerging evidences indicate that the alteration of interhemispheric functional coordination may be involved in the pathogenesis of major depressive disorder (MDD). However, it remains unclear weather the imbalanced interhemispheric functional connectivity is associated with the treatment response in MDD. Methods: In present study, we aim to explore the potential marker by using the voxel-mirrored homotopic connectivity (VMHC) approach, which may be contributing to predict the clinical prognosis in MDD. 82 MDD patients and 50 normal control (NC) subjects participated in this study. We divided the MDD group into unresponded and responded group according to the reduction rate of Hamilton Rating Scale for Depression (HAMD) within 2 weeks. Results: The study detected significantly decreased VMHC in bilateral precuneus (pCu), inferior temporal gyrus (ITG) and increased VMHC in middle frontal gyrus (MFG) and caudate nucleus when compared remitted depression (RD) group to unremitted depression (URD) group. Meanwhile, when compared with NC group, the URD group presented reduced VMHC in bilateral cerebellum anterior lobe, thalamus and postcentral gyrus. Furthermore, the VHMC in media frontal gyrus, postcentral gyrus and precentral gyrus were significantly decreased in RD group. Correlation analysis suggested that reduced VMHC in bilateral pCu was negatively correlated with the baseline HAMD score of URD (r=-0.325, P=0.041). Receiver Operating Characteristic (ROC) curve indicated that three regional VMHC changes could identify depressed patient with poorer treatment response: ITG [area under curve (AUC)=0.699, P=0.002, 95%CI=0.586–0.812], MFG (AUC=0.692, P=0.003, 95%CI=0.580– 0.805), pCu (AUC=0.714, P=0.001, 95%CI=0.603–0.825). Conclusion: The current study combined with previous evidence indicates that the subdued intrinsic interhemispheric functional connectivity might represents a novel neural trait involved in the pathophysiology of MDD. PS188 Predict value of functional topological features for early response to antidepressant treatment in major depressive disorder Zhenghua Hou1, Zan Wang2, Wenhao Jiang1, Yingying Yin1, Yingying Yue1, Yuqun Zhang1, Xiaopeng Song3, and Yonggui Yuan1* 1Department of Psychosomatics & Psychiatry, Institute of Psychosomatic Medicine, Zhongda Hospital, Medical School of Southeast University, No. 87, Dingjiaqiao Road, Nanjing 210009, China 2Department of Neurology, Institute of Neuropsychology, Medical School of Southeast University, Nanjing 210009, China 3 Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China Abstract Background: Major depressive disorder (MDD) disrupts functional networks in focal brain regions. Identifying a pretreatment marker would be aid in optimizing therapy. Methods: 82 MDD patients and 50 healthy controls (HC) were recruited in this study and underwent a resting-state functional magnetic resonance imaging scan. Based on the thresholded partial correlation matrices of 58 specific brain regions, graph theory approach was applied to analysis the topological properties. Results: Both responsed depression (RD) and unresponsed depression (URD) shown decreased normalized characteristic path length (λ) as compared to HC (P<0.05). Importantly, when compared to HC, the nodal degrees of RD were reduced in left superior medial orbitofrontal gyrus and left anterior cingulate gyrus but increased in right Inferior orbitofrontal gyrus (all P<0.017, FDR corrected). Moreover, the nodal degree in right dorsolateral prefrontal cortex (DLPFC) was significantly decreased in RD compared with URD (P<0.017, FDR corrected). Receiver operating characteristic (ROC) curve analysis indicated that theBackground: Major depressive disorder (MDD) disrupts functional networks in focal brain regions. Identifying a pretreatment marker would be aid in optimizing therapy. Methods: 82 MDD patients and 50 healthy controls (HC) were recruited in this study and underwent a resting-state functional magnetic resonance imaging scan. Based on the thresholded partial correlation matrices of 58 specific brain regions, graph theory approach was applied to analysis the topological properties. Results: Both responsed depression (RD) and unresponsed depression (URD) shown decreased normalized characteristic path length (λ) as compared to HC (P<0.05). Importantly, when compared to HC, the nodal degrees of RD were reduced in left superior medial orbitofrontal gyrus and left anterior cingulate gyrus but increased in right Inferior orbitofrontal gyrus (all P<0.017, FDR corrected). Moreover, the nodal degree in right dorsolateral prefrontal cortex (DLPFC) was significantly decreased in RD compared with URD (P<0.017, FDR corrected). Receiver operating characteristic (ROC) curve analysis indicated that the area under curve (AUC) of nodal degree in right DLPFC was 0.658 [95% confidence interval (CI): 0.64–0.78,P=0.014], which could serve as a specific predictor to differentiate responsed patients from unresponsed patients. Conclusion: The results extend the nascent understanding of exploring the#8232; pretreatment neuroimaging predictors of early response to antidepressants therapies.