Alterations in brain synaptic proteins and mRNAs in mood disorders: a systematic review and meta-analysis of postmortem brain studies.

The pathophysiological mechanisms underlying bipolar (BD) and major depressive disorders (MDD) are multifactorial but likely involve synaptic dysfunction and dysregulation. There are multiple synaptic proteins but three synaptic proteins, namely SNAP-25, PSD-95, and synaptophysin, have been widely studied for their role in synaptic function in human brain postmortem studies in BD and MDD. These studies have yielded contradictory results, possibly due to the small sample size and sourcing material from different cortical regions of the brain. We performed a systematic review and meta-analysis to understand the role of these three synaptic proteins and other synaptic proteins, messenger RNA (mRNA) and their regional localizations in BD and MDD. A systematic literature search was conducted and the review is reported in accordance with the MOOSE Guidelines. Meta-analysis was performed to compare synaptic marker levels between BD/MDD groups and controls separately. 1811 papers were identified in the literature search and screened against the preset inclusion and exclusion criteria. A total of 72 studies were screened in the full text, of which 47 were identified as eligible to be included in the systematic review. 24 of these 47 papers were included in the meta-analysis. The meta-analysis indicated that SNAP-25 protein levels were significantly lower in BD. On average, PSD-95 mRNA levels were lower in BD, and protein levels of SNAP-25, PSD-95, and syntaxin were lower in MDD. Localization analysis showed decreased levels of PSD-95 protein in the frontal cortex. We found specific alterations in synaptic proteins and RNAs in both BD and MDD. The review was prospectively registered online in PROSPERO international prospective register of systematic reviews, registration no. CRD42020196932.

[Study on the EEG functional brain connectivity characteristics of college students with depression].

The aim of the present study was to explore the changes in some functional connectivity in the resting-state electroencephalogram (EEG) based functional brain network of depressed college students, and to understand the brain regions involved in the onset of depression and the electrophysiological activity of subcortical nerve cells, hoping to provide additional information for the diagnosis of depression. Twenty female college students with depressive symptoms were selected according to the Beck Depression Inventory-II (BDI-II) and the Self-rating Depression Scale (SDS). The EEG information of 20 female college students under resting-state was collected by using a 32-conduction EEG acquisition system (Neuroscan). Then Pearson correlation analysis, coherence analysis, phase locking value analysis, phase lag index analysis and weighted phase lag index analysis were used to construct the resting-state brain functional network. The results showed that, compared with the normal group, the depression group exhibited significantly increased correlation in θ and ß bands of EEG (P < 0.05), and extremely significantly increased in α band (P < 0.01). Among them, the coherence in α and ß bands was significantly increased (P < 0.05), mainly concentrated in the left hemisphere frontal lobe and temporal lobe region. The phase locking value in θ, α and ß bands was significantly increased (P < 0.05), mainly concentrated in the prefrontal region and the left hemisphere from the frontal region to the temporal region, and the connectivity in α band was the most obvious. Correlation analysis showed a significant positive correlation between indicators of differential functional connectivity (coherence and phase locking value) and BDI-II scores in the depression group, and the receiver operating characteristics (ROC) curve indicated a high specificity of 85% for the differential indicators. These results suggest that the abnormal brain function of the depressed college students is related to the change of functional connectivity in the left hemisphere, especially α frequency band in the frontal region, which is of great significance for the diagnosis of depression in the future.