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Summary: Background: Disturbances in emotion regulation are the hallmarks of major depressive disorder (MDD). The incapacity to control negative emotion in patients has been associated with abnormal hyperactivation of the limbic system and hypoactivation of the frontal cortex. The amygdala and orbital frontal cortex (OFC) are two critical regions of the emotion regulation neural systems. Methods: This study investigated the anatomical basis of abnormal emotion regulation by tracking the fiber tracts connecting the amygdala and OFC. In addition, using dynamic casual modeling on resting‐state fMRI data of 20 MDD patients and equivalent controls, we investigated the exact neural mechanism through which abnormal communications between these two nodes were mediated in MDD. Key Results: The results revealed disrupted white matter integrity of fiber tracts in MDD, suggesting that functional abnormalities were accompanied by underlying anatomical basis. We also detected a failure of inhibition of the OFC on the activity of the amygdala in MDD, suggesting dysconnectivity was mediated through "top‐down" influences from the frontal cortex to the amygdala. Following 8 weeks of antidepressant treatment, the patients showed significant clinical improvement and normalization of the abnormal OFC‐amygdala structural and effective connectivity in the left hemisphere. Conclusions & Inferences: Our findings suggest that pathways connecting these two nodes may be core targets of the antidepressant treatment. In particular, it raised the intriguing question: Does the reversal of structural markers of connectivity reflect a response to antidepressant medication or activity‐dependent myelination following a therapeutic restoration of effective connectivity? [ABSTRACT FROM AUTHOR]

• A cross-sectional study was conducted on 1289 young Chinese outpatients with first-episode medication-naïve major depressive disorder. • The prevalence of abnormal glucose metabolism was 12.57%. • Higher TSH levels and more severe anxiety symptoms were associated with fasting glucose levels in young patients with first-episode medication-naïve major depressive disorder. • TSH could distinguish patients with abnormal glucose metabolism from those without. The high co-morbidity of abnormal glucose metabolism in depressed patients has been extensively studied, but few studies have explored abnormal glucose metabolism in young patients with major depressive disorder (MDD). This study aimed to examine the prevalence and clinical correlates of abnormal glucose metabolism in young patients with first-episode medication-naïve (FEMN) MDD. A cross-sectional study was conducted on 1289 young Chinese outpatients with FEMN MDD. All subjects were assessed on the Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale (HAMA), Positive and Negative Syndrome Scale, and their sociodemographic information was collected, and blood pressure, blood glucose, lipid and thyroid hormone levels were measured. The prevalence of abnormal glucose metabolism was 12.57% in young FEMN MDD outpatients. Thyroid stimulating hormone (TSH) levels and HAMA scale scores were associated with fasting blood glucose levels in patients with FEMN MDD (P <0.05), and TSH could differentiate patients with abnormal normal glucose metabolism from those without abnormal glucose metabolism (Area Under Curve of 0.774). Our study showed a high prevalence of comorbid glucose metabolism abnormalities in young FEMN MDD outpatients. TSH may be a promising biomarker of abnormal glucose metabolism in young patients with FEMN MDD. [ABSTRACT FROM AUTHOR]

Transcranial magnetic stimulation (TMS) is a safe, tolerable, and evidence‐based intervention for major depressive disorder (MDD). However, even after decades of research, nearly half of the patients with MDD fail to respond to conventional TMS, with responding slowly and requiring daily attendance at the treatment site for 4–6 weeks. To intensify antidepressant efficacy and shorten treatment duration, accelerated TMS protocols, which involve multiple sessions per day over a few days, have been proposed and evaluated for safety and viability. We reviewed and summarized the current knowledge in accelerated TMS, including stimulation parameters, antidepressant efficacy, anti‐suicidal efficacy, safety, and adverse effects. Limitations and suggestions for future directions are also addressed, along with a brief discussion on the application of accelerated TMS during the COVID‐19 pandemic. This article is categorized under:Neuroscience > Clinical Neuroscience [ABSTRACT FROM AUTHOR]

Depression accounts for a high proportion of neuropsychiatric disorders and is associated with abnormal states of neurons in specific brain regions. Microglia play a pivotal role in the inflammatory state during depression development; however, the exact mechanism underlying chronic mood states remains unknown. Thus, the present study aimed to determine whether microRNAs (miRNAs) alleviate stress-induced depression-like behavior in mice by regulating the expression levels of their target genes, explore the role of neuroinflammation induced by microglial activation in the pathogenesis and progression of depression, and determine whether the role of the miR-29a-5p/transmembrane protein 33 (TMEM33) axis. In this study, chronic unpredictable mild stress (CUMS) mouse depression model, various behavioral tests, western blotting, dual-luciferase reporter assay, enzyme-linked immunosorbent assay, real-time quantitative reverse transcription PCR, immunofluorescence and lentivirus-mediated gene transfer were used. After exposure to the CUMS paradigm, miR-29a-5p was significantly down-regulated. This downregulation subsequently promoted the polarization of microglia M1 by upregulating the expression of TMEM33, resulting in enhanced inflammatory chemokines affecting neurons. Conversely, the upregulation of miR-29a-5p within the prefrontal cortex (PFC) suppressed TMEM33 expression, facilitated microglia M2-polarization, and ameliorated depressive-like behavior. Only rodent models of depression were used, and human samples were not included. The results of this study suggest that miR-29a-5p deficits within the PFC mediate microglial anomalies and contribute to depressive-like behaviors. miR-29a-5p and TMEM33 may, therefore, serve as potential therapeutic targets for the treatment of depression. • miR-29a-5p is downregulated by chronic stress. • Upregulation of miR-29a-5p improved depression-like behavior. • miR-29a-5p deficits in prefrontal cortex mediate microglial anomalies. • miR-29a-5p and TMEM33 are potential therapeutic targets for depression treatment. [ABSTRACT FROM AUTHOR]

Introduction: Repetitive transcranial magnetic stimulation (rTMS) is a clinically useful therapy for depression. However, the effects of rTMS on the metabolism of fatty acids (FAs) and the composition of gut microbiota in depression are not well established. Methods: Mice received rTMS (15 Hz, 1.26 T) for seven consecutive days after exposure to chronic unpredictable mild stress (CUMS). The subsequent depressive‐like behaviors, the composition of gut microbiota of stool samples, as well as medium‐ and long‐chain fatty acids (MLCFAs) in the plasma, prefrontal cortex (PFC), and hippocampus (HPC) were evaluated. Results: CUMS induced remarkable changes in gut microbiotas and fatty acids, specifically in community diversity of gut microbiotas and PUFAs in the brain. 15 Hz rTMS treatment alleviates depressive‐like behaviors and partially normalized CUMS induced alterations of microbiotas and MLCFAs, especially the abundance of Cyanobacteria, Actinobacteriota, and levels of polyunsaturated fatty acids (PUFAs) in the hippocampus and PFC. Conclusion: These findings revealed that the modulation of gut microbiotas and PUFAs metabolism might partly contribute to the antidepressant effect of rTMS. [ABSTRACT FROM AUTHOR]

Background: The association between abnormal gut microbiome composition and depression is well established. However, the composition and functional capacity of the gut microbiota regarding depressed women has been poorly addressed.Methods: Stool samples from 62 female patients with major depressive disorder (MDD) and 46 healthy controls (Con) were analyzed by 16S rRNA gene sequencing; Twenty fecal samples from the patient group and 21 fecal samples from the Con group were further analyzed by shotgun metagenomic sequencing. Psychiatric symptoms and psychological, social, and professional functioning was also assessed.Results: Phylum Bacteroidetes, proteobaeteria, and Fusobacteria were greatly enriched in patients with MDD, while the Firmicutes and Actinobacteria phyla were consistently higher in Con. Notably, 18 microbial markers were identified on a random forest model and achieve an area under the curve of 0.92 between patients with MDD and the Con group. Forty-five species and their associated function were identified with statistically significant differences between patients with MDD and the Con group.Limitations: The number of recruited samples, especially samples enrolled for shotgun metagenomic sequencing was relatively small, and the stool samples were collected only at baseline, making it difficult to establish a causal association between changes in gut microbiota compositions and disease remission.Conclusions: This study characterizes the gut microbiota and their related function in female MDD. The gut microbiota-based biomarkers may be helpful in diagnosis and the altered gut microbial metabolites may contribute to the pathogenesis of MDD in women, representing potential microbial targets. [ABSTRACT FROM AUTHOR]

Understanding the neural substrates of depression is crucial for diagnosis and treatment. Here, we review recent studies of functional and effective connectivity in depression, in terms of functional integration in the brain. Findings from these studies, including our own, point to the involvement of at least four networks in patients with depression. Elevated connectivity of a ventral limbic affective network appears to be associated with excessive negative mood (dysphoria) in the patients; decreased connectivity of a frontal‐striatal reward network has been suggested to account for loss of interest, motivation, and pleasure (anhedonia); enhanced default mode network connectivity seems to be associated with depressive rumination; and diminished connectivity of a dorsal cognitive control network is thought to underlie cognitive deficits especially ineffective top‐down control of negative thoughts and emotions in depressed patients. Moreover, the restoration of connectivity of these networks—and corresponding symptom improvement—following antidepressant treatment (including medication, psychotherapy, and brain stimulation techniques) serves as evidence for the crucial role of these networks in the pathophysiology of depression. [ABSTRACT FROM AUTHOR]

Quetiapine (QUE) and repetitive transcranial magnetic stimulation (rTMS) have been considered to be possible monotherapies for depression or adjunctive therapies for the treatment of the resistant depression, but the underlying mechanisms remain unclear. The present study aimed to assess the effects of combined QUE and rTMS treatment on depressive-like behaviors, hippocampal proliferation, and the in vivo and in vitro expressions of phosphorylated extracellular signal-regulated protein kinase (pERK1/2) and brain-derived neurotrophic factor (BDNF) in male Sprague–Dawley rats. The administration of QUE and rTMS was determined not only to reverse the depressive-like behaviors of rats exposed to chronic unpredictable stress (CUS) but also to restore the protein expressions of pERK1/2 and BDNF and cell proliferation in the hippocampus. Additionally, QUE and rTMS promoted the proliferation and increased the expression of pERK1/2 and BDNF in hippocampal-derived neural stem cells (NSCs), and these effects were abolished by U0126. Taken together, these results suggest that the antidepressive-like effects of QUE and rTMS might be related to the activation of the BDNF/ERK signaling pathway and the up-regulation of cell proliferation in the hippocampus. [ABSTRACT FROM AUTHOR]

Highlights: [•] 20–30% of depressive rats respond poorly to fluoxetine treatment. [•] A significant decrease of hippocampal neurogenesis was observed. [•] Quetiapine add-on treatment significantly improved the depressive behaviors. [•] The increased newborn neurons may be implicated in quetiapine augmentation therapy. [•] Quetiapine add-on therapy increased newborn cell proliferation but not neuronal differentiation. [Copyright &y& Elsevier]

Front cover: The cover image, by Bao‐Juan Li et al., is based on the Review Article A brain network model for depression: From symptom understanding to disease intervention. DOI: https://doi.org/10.1111/cns.12998. [ABSTRACT FROM AUTHOR]