Course of illness, hippocampal function, and hippocampal volume in major depression

Amygdala and hippocampal substructure volumes and their association with improvement in mood symptoms in patients with mood disorders undergoing electroconvulsive therapy

Electroconvulsive therapy (ECT) demonstrates favorable outcomes in the management of severe depressive disorders. ECT has been consistently associated with volumetric increases in the amygdala and hippocampus. However, the underlying mechanisms of these structural changes and their association to clinical improvement remains unclear. In this cross-sectional structural MRI study, we assessed the difference in amygdala subnuclei and hippocampus subfields in n = 37 patients with either unipolar or bipolar disorder immediately after eighth ECT sessions compared to (n = 40) demographically matched patients in partial remission who did not receive ECT (NoECT group). Relative to NoECT, the ECT group showed significantly larger bilateral amygdala volumes post-treatment, with the effect originating from the lateral, basal, and paralaminar nuclei and the left corticoamydaloid transition area. No significant group differences were observed for the hippocampal or cortical volumes. ECT was associated with a significant decrease in depressive symptoms. However, there were no significant correlations between amygdala subnuclei volumes and symptom improvement. Our study corroborates previous reports on increased amygdalae volumes following ECT and further identifies the subnuclei driving this effect. However, the therapeutic effect of ECT does not seem to be directly related to structural changes in the amygdala.

Distinct patterns of hippocampal subfield volumes predict coping strategies, emotion regulation, and impulsivity in healthy adults

BACKGROUND

Recent studies have suggested that the hippocampus (HC) is involved in cognitive and behavioral functions beyond memory. We aimed to investigate how the volume of each subfield of the HC is associated with distinct patterns of coping strategies, emotion regulation, and impulsivity in a healthy population.

METHODS

We studied a total of 218 healthy subjects using the Leipzig mind-brain-body dataset. Participants were assessed for coping strategies, emotion regulation, and impulsivity using the Cognitive Emotion Regulation Questionnaire (CERQ), Coping Orientations to Problems Experienced (COPE), Impulsive Behavior Scale (UPPS), and Behavioral Activation and Inhibition System (BAS/BIS). The associations between HC subfield volumes including CA1, CA2/3, CA4/DG, SR-SL-SM, and subiculum, and behavioral scores were examined using multiple linear regression models adjusted for possible confounders, including age, sex, years of education, handedness, total intracranial volume (ICV), and HC volume.

RESULTS

The use of emotional support, venting, and positive reframing coping strategies were significantly and positively correlated with total, total right, and total left HC volumes. Venting was significantly associated with CA1 after adjusting for age, sex, handedness, and education (P=0.001, B = 0.265, P-FDR = 0.005). No significant association was observed between CERQ subscales and HC subfield volumes after controlling for confounders and multiple analyses. However, sensation-seeking subscale of the UPPS-P was positively correlated with total and right CA2-CA3 volumes after adjustments for age, sex, handedness, ICV, and HC volumes (P=0.002, B = 0.266, P-FDR = 0.035). BAS and BIS subscales did not show significant relationship with HC subfield volumes.

CONCLUSION

Patterns of HC subfields volumes are associated with coping strategies, impulsivity, and emotion regulation. In particular, using emotional support, positive reframing, venting, and sensation seeking are significantly associated with certain HC subfield volumes. These findings suggest that the hippocampus may play a crucial role in modulating emotional responses and behavioral adaptations, offering potential targets for therapeutic interventions.

Exploring the Potential of Probiotics and Prebiotics in Major Depression: From Molecular Function to Clinical Therapy

Major depressive disorder (MDD) represents a complex and challenging mental health condition with multifaceted etiology. Recent research exploring the gut-brain axis has shed light on the potential influence of gut microbiota on mental health, offering novel avenues for therapeutic intervention. This paper reviews current evidence on the role of prebiotics and probiotics in the context of MDD treatment. Clinical studies assessing the effects of prebiotic and probiotic interventions have demonstrated promising results, showcasing improvements in depression symptoms and metabolic parameters in certain populations. Notably, prebiotics and probiotics have shown the capacity to modulate inflammatory markers, cortisol levels, and neurotransmitter pathways linked to MDD. However, existing research presents varied outcomes, underscoring the need for further investigation into specific microbial strains, dosage optimization, and long-term effects. Future research should aim at refining personalized interventions, elucidating mechanisms of action, and establishing standardized protocols to integrate these interventions into clinical practice. While prebiotics and probiotics offer potential adjunctive therapies for MDD, continued interdisciplinary efforts are vital to harnessing their full therapeutic potential and reshaping the landscape of depression treatment paradigms.

The association among negative life events, alexithymia, and depressive symptoms in a psychosomatic outpatient sample

BACKGROUND

Depression is a life-threatening mental health problem. Various factors have been demonstrated to be associated with depressive symptoms, including negative life events (NLEs) and alexithymia. A retrospective study was conducted to investigate the relationship among negative life events, alexithymia, and depression symptoms in a psychosomatic outpatient sample in China.

METHODS

A total of 2747 outpatients (aged 18 - 65) were included in this investigation. The Life Events Scale (LES), Toronto alexithymia scale (TAS-26), and 9-item Patient Health Questionnaire (PHQ-9) were used to assess NLEs, alexithymia, and depressive symptoms, respectively. A stepwise regression analysis model was established to investigate the relationship among alexithymia, NLEs, and depressive symptoms.

RESULTS

Overall, 67.0% of the patient sample had a PHQ-9 score of 10 or higher. The stepwise regression analysis model showed a well-fitted model, in which NLEs and alexithymia explain a total of 34.2% of the variance of depressive symptoms in these participants. NLEs (β = 0.256, p < 0.001) and dimensions of alexithymia (difficult describing feelings (β = 0.192, p < 0.001) and identifying feelings (β = 0.308, p < 0.001)) were positively correlated with symptoms of depression.

CONCLUSIONS

Previous studies have confirmed the correlation between NLEs and depression, alexithymia and depression, respectively. In our study, we used a stepwise regression model to explain the relationship among those variables simultaneously, and found that NLEs and alexithymia could function as predictors of depressive symptoms. Based on this discovery, alexithymia-focused treatment strategies could be alternative in depressive patients with alexithymia, but this remains to be verified in the future.

Visual EMDR stimulation mitigates acute varied stress effects on morphology of hippocampal neurons in male Wistar rats

Introduction

Stress is a pervasive health concern known to induce physiological changes, particularly impacting the vulnerable hippocampus and the morphological integrity of its main residing cells, the hippocampal neurons. Eye Movement Desensitization and Reprocessing (EMDR), initially developed to alleviate emotional distress, has emerged as a potential therapeutic/preventive intervention for other stress-related disorders. This study aimed to investigate the impact of Acute Variable Stress (AVS) on hippocampal neurons and the potential protective effects of EMDR.

Methods

Rats were exposed to diverse stressors for 7 days, followed by dendritic morphology assessment of hippocampal neurons using Golgi-Cox staining.

Results

AVS resulted in significant dendritic atrophy, evidenced by reduced dendritic branches and length. In contrast, rats receiving EMDR treatment alongside stress exposure exhibited preserved dendritic morphology comparable to controls, suggesting EMDR's protective role against stressinduced dendritic remodeling.

Conclusions

These findings highlight the potential of EMDR as a neuroprotective intervention in mitigating stress-related hippocampal alterations.

An empirical analysis of structural neuroimaging profiles in a staging model of depression

We examine structural brain characteristics across three diagnostic categories: at risk for serious mental illness; first-presenting episode and recurrent major depressive disorder (MDD). We investigate whether the three diagnostic groups display a stepwise pattern of brain changes in the cortico-limbic regions. Integrated clinical and neuroimaging data from three large Canadian studies were pooled (total n = 622 participants, aged 12-66 years). Four clinical profiles were used in the classification of a clinical staging model: healthy comparison individuals with no history of depression (HC, n = 240), individuals at high risk for serious mental illness due to the presence of subclinical symptoms (SC, n = 80), first-episode depression (FD, n = 82), and participants with recurrent MDD in a current major depressive episode (RD, n = 220). Whole-brain volumetric measurements were extracted with FreeSurfer 7.1 and examined using three different types of analyses. Hippocampal volume decrease and cortico-limbic thinning were the most informative features for the RD vs HC comparisons. FD vs HC revealed that FD participants were characterized by a focal decrease in cortical thickness and global enlargement in amygdala volumes. Greater total amygdala volumes were significantly associated with earlier onset of illness in the FD but not the RD group. We did not confirm the construct validity of a tested clinical staging model, as a differential pattern of brain alterations was identified across the three diagnostic groups that did not parallel a stepwise clinical staging approach. The pathological processes during early stages of the illness may fundamentally differ from those that occur at later stages with clinical progression.

Long-term enhancements in antidepressant efficacy and neurogenesis: Effects of intranasal co-administration of neuropeptide Y 1 receptor (NPY1R) and galanin receptor 2 (GALR2) agonists in the ventral hippocampus

This study evaluates the sustained antidepressant-like effects and neurogenic potential of a 3-day intranasal co-administration regimen of galanin receptor 2 (GALR2) agonist M1145 and neuropeptide Y Y1 receptor (NPY1R) agonist [Leu31, Pro34]NPY in the ventral hippocampus of adult rats, with outcomes analyzed 3 weeks post-treatment. Utilizing the forced swimming test (FST), we found that this co-administration significantly enhances antidepressant-like behaviors, an effect neutralized by the GALR2 antagonist M871, highlighting the synergistic potential of these neuropeptides in modulating mood-related behaviors. In situ proximity ligation assay (PLA) indicated a significant increase in GALR2/NPYY1R heteroreceptor complexes in the ventral hippocampal dentate gyrus, suggesting a molecular basis for the behavioral outcomes observed. Moreover, proliferating cell nuclear antigen (PCNA) immunolabeling revealed increased cell proliferation in the subgranular zone of the dentate gyrus, specifically in neuroblasts as evidenced by co-labeling with doublecortin (DCX), without affecting quiescent neural progenitors or astrocytes. The study also noted a significant uptick in the number of DCX-positive cells and alterations in dendritic morphology in the ventral hippocampus, indicative of enhanced neuronal differentiation and maturation. These morphological changes highlight the potential of these agonists to facilitate the functional integration of new neurons into existing neural circuits. By demonstrating the long-lasting effects of a brief, 3-day intranasal administration of GALR2 and NPY1R agonists, our findings contribute significantly to the understanding of neuropeptide-mediated neuroplasticity and herald novel therapeutic strategies for the treatment of depression and related mood disorders, emphasizing the therapeutic promise of targeting neurogenesis and neuronal maturation processes.

Enhanced neuronal survival and BDNF elevation via long-term co-activation of galanin 2 (GALR2) and neuropeptide Y1 receptors (NPY1R): potential therapeutic targets for major depressive disorder

BACKGROUND

Major Depressive Disorder (MDD) is a prevalent and debilitating condition, necessitating novel therapeutic strategies due to the limited efficacy and adverse effects of current treatments. We explored how galanin receptor 2 (GALR2) and Neuropeptide Y1 Receptor (NPYY1R) agonists, working together, can boost brain cell growth and increase antidepressant-like effects in rats. This suggests new ways to treat Major Depressive Disorder (MDD).

RESEARCH DESIGN AND METHODS

In a controlled laboratory setting, adult naive Sprague-Dawley rats were administered directly into the brain's ventricles, a method known as intracerebroventricular (ICV) administration, with GALR2 agonist (M1145), NPYY1R agonist, both, or in combination with a GALR2 antagonist (M871). Main outcome measures included long-term neuronal survival, differentiation, and behavioral.

RESULTS

Co-administration of M1145 and NPYY1R agonist significantly enhanced neuronal survival and maturation in the ventral dentate gyrus, with a notable increase in Brain-Derived Neurotrophic Factor (BDNF) expression. This neurogenic effect was associated with an antidepressant-like effect, an outcome partially reversed by M871.

CONCLUSIONS

GALR2 and NPYY1R agonists jointly promote hippocampal neurogenesis and exert antidepressant-like effects in rats without adverse outcomes, highlighting their therapeutic potential for MDD. The study's reliance on an animal model and intracerebroventricular delivery warrants further clinical exploration to confirm these promising results.

Niuhuang Qingxin Wan ameliorates depressive-like behaviors and improves hippocampal neurogenesis through modulating TrkB/ERK/CREB signaling pathway in chronic restraint stress or corticosterone challenge mice

Introduction: Chronic stress-associated hormonal imbalance impairs hippocampal neurogenesis, contributing to depressive and anxiety behaviors. Targeting neurogenesis is thus a promising antidepressant therapeutic strategy. Niuhuang Qingxin Wan (NHQXW) is an herbal formula for mental disorders in Traditional Chinese Medicine (TCM) practice, but its anti-depressant efficacies and mechanisms remain unverified. Methods: In the present study, we tested the hypothesis that NHQXW could ameliorate depressive-like behaviors and improve hippocampal neurogenesis by modulating the TrkB/ERK/CREB signaling pathway by utilizing two depression mouse models including a chronic restraint stress (CRS) mouse model and a chronic corticosterone (CORT) stress (CCS) induced mouse model. The depression-like mouse models were orally treated with NHQXW whereas fluoxetine was used as the positive control group. We evaluated the effects of NHQXW on depressive- and anxiety-like behaviors and determined the effects of NHQXW on inducing hippocampal neurogenesis. Results: NHQXW treatment significantly ameliorated depressive-like behaviors in those chronic stress mouse models. NHQXW significantly improved hippocampal neurogenesis in the CRS mice and CCS mice. The potential neurogenic mechanism of NHQXW was identified by regulating the expression levels of BDNF, TrkB, p-ERK (T202/T204), p-MEK1/2 (S217/221), and p-CREB (S133) in the hippocampus area of the CCS mice. NHQXW revealed its antidepressant and neurogenic effects that were similar to fluoxetine. Moreover, NHQXW treatment revealed long-term effects on preventing withdrawal-associated rebound symptoms in the CCS mice. Furthermore, in a bioactivity-guided quality control study, liquiritin was identified as one of the bioactive compounds of NHQXW with the bioactivities of neurogenesis-promoting effects. Discussion: Taken together, NHQXW could be a promising TCM formula to attenuate depressive- and anxiety-like behaviors against chronic stress and depression. The underlying anti-depressant mechanisms could be correlated with its neurogenic activities by stimulating the TrkB/ERK/CREB signaling pathway.

An imaging review of the hippocampus and its common pathologies

The hippocampus is a complex structure located in the mesial temporal lobe that plays a critical role in cognitive and memory-related processes. The hippocampal formation consists of the dentate gyrus, hippocampus proper, and subiculum, and its importance in the neural circuitry makes it a key anatomic structure to evaluate in neuroimaging studies. Advancements in imaging techniques now allow detailed assessment of hippocampus internal architecture and signal features that has improved identification and characterization of hippocampal abnormalities. This review aims to summarize the neuroimaging features of the hippocampus and its common pathologies. It provides an overview of the hippocampal anatomy on magnetic resonance imaging and discusses how various imaging techniques can be used to assess the hippocampus. The review explores neuroimaging findings related to hippocampal variants (incomplete hippocampal inversion, sulcal remnant and choroidal fissure cysts), and pathologies of neoplastic (astrocytoma and glioma, ganglioglioma, dysembryoplastic neuroepithelial tumor, multinodular and vacuolating neuronal tumor, and metastasis), epileptic (mesial temporal sclerosis and focal cortical dysplasia), neurodegenerative (Alzheimer's disease, progressive primary aphasia, and frontotemporal dementia), infectious (Herpes simplex virus and limbic encephalitis), vascular (ischemic stroke, arteriovenous malformation, and cerebral cavernous malformations), and toxic-metabolic (transient global amnesia and opioid-associated amnestic syndrome) etiologies.

Altered Sex Differences in Hippocampal Subfield Volumes in Schizophrenia

BACKGROUND AND HYPOTHESIS

The hippocampus is a heterogenous brain structure that differs between the sexes and has been implicated in the pathophysiology of psychiatric illnesses. Here, we explored sex and diagnostic group differences in hippocampal subfield volumes, in individuals with schizophrenia spectrum disorder (SZ), bipolar disorders (BD), and healthy controls (CTL).

STUDY DESIGN

One thousand and five hundred and twenty-one participants underwent T1-weighted magnetic resonance imaging (SZ, n = 452, mean age 30.7 ± 9.2 [SD] years, males 59.1%; BD, n = 316, 33.7 ± 11.4, 41.5%; CTL, n = 753, 34.1 ± 9.1, 55.6%). Total hippocampal, subfield, and intracranial volumes were estimated with Freesurfer (v6.0.0). Analysis of covariance and multiple regression models were fitted to examine sex-by-diagnostic (sub)group interactions in volume. In SZ and BD, separately, associations between volumes and clinical as well as cognitive measures were examined between the sexes using regression models.

STUDY RESULTS

Significant sex-by-group interactions were found for the total hippocampus, dentate gyrus, molecular layer, presubiculum, fimbria, hippocampal-amygdaloid transition area, and CA4, indicating a larger volumetric deficit in male patients relative to female patients when compared with same-sex CTL. Subgroup analyses revealed that this interaction was driven by males with schizophrenia. Effect sizes were overall small (partial η < 0.02). We found no significant sex differences in the associations between hippocampal volumes and clinical or cognitive measures in SZ and BD.

CONCLUSIONS

Using a well-powered sample, our findings indicate that the pattern of morphological sex differences in hippocampal subfields is altered in individuals with schizophrenia relative to CTL, due to higher volumetric deficits in males.

Serotonin is a common thread linking different classes of antidepressants

Depression pathology remains elusive. The monoamine hypothesis has placed much focus on serotonin, but due to the variable clinical efficacy of monoamine reuptake inhibitors, the community is looking for alternative therapies such as ketamine (neurogenesis theory of antidepressant action). There is evidence that different classes of antidepressants may affect serotonin levels; a notion we test here. We measure hippocampal serotonin in mice with voltammetry and study the effects of acute challenges of escitalopram, fluoxetine, reboxetine, and ketamine. We find that pseudo-equivalent doses of these drugs similarly raise ambient serotonin levels, despite their differing pharmacodynamics because of differences in Uptake 1 and 2, rapid SERT trafficking, and modulation of serotonin by histamine. These antidepressants have different pharmacodynamics but have strikingly similar effects on extracellular serotonin. Our findings suggest that serotonin is a common thread that links clinically effective antidepressants, synergizing different theories of depression (synaptic plasticity, neurogenesis, and the monoamine hypothesis).

Reviewing the neurobiology of electroconvulsive therapy on a micro- meso- and macro-level

BACKGROUND

Electroconvulsive therapy (ECT) remains the one of the most effective of biological antidepressant interventions. However, the exact neurobiological mechanisms underlying the efficacy of ECT remain unclear. A gap in the literature is the lack of multimodal research that attempts to integrate findings at different biological levels of analysis METHODS: We searched the PubMed database for relevant studies. We review biological studies of ECT in depression on a micro- (molecular), meso- (structural) and macro- (network) level.

RESULTS

ECT impacts both peripheral and central inflammatory processes, triggers neuroplastic mechanisms and modulates large scale neural network connectivity.

CONCLUSIONS

Integrating this vast body of existing evidence, we are tempted to speculate that ECT may have neuroplastic effects resulting in the modulation of connectivity between and among specific large-scale networks that are altered in depression. These effects could be mediated by the immunomodulatory properties of the treatment. A better understanding of the complex interactions between the micro-, meso- and macro- level might further specify the mechanisms of action of ECT.

Sex steroids and the female brain across the lifespan: insights into risk of depression and Alzheimer's disease

Despite widespread sex differences in prevalence and presentation of numerous illnesses affecting the human brain, there has been little focus on the effect of endocrine ageing. Most preclinical studies have focused on males only, and clinical studies often analyse data by covarying for sex, ignoring relevant differences between the sexes. This sex- (and gender)-neutral approach is biased and contributes to the absence of targeted treatments and services for all sexes (and genders). Female health has been historically understudied, with grave consequences for their wellbeing and health equity. In this Review, we spotlight female brain health across the lifespan by informing on the role of sex steroids, particularly oestradiol, on the female brain and on risk for diseases more prevalent in females, such as depression and Alzheimer's disease.

Brain-derived neurotrophic factor levels in perinatal depression: A systematic review and meta-analysis

BACKGROUND

This systematic review and meta-analysis aim to synthesize the available evidence and determine the overall brain-derived neurotrophic factor (BDNF) levels in individuals diagnosed with perinatal depression (PND).

METHODS

We performed a thorough search of electronic databases, including PubMed, Embase, PsycINFO, and Web of Science, from their start until April 30, 2023. Our search strategy involved using specific keywords and medical subject headings (MeSH) terms related to BDNF, perinatal, post-partum, and antepartum depression. In the meta-analysis, we employed a random-effects model, and subgroup analyses were conducted to investigate any variations in the results.

RESULTS

A total of 15 studies met the inclusion criteria, of which 10 were used in the quantitative analysis. The meta-analysis demonstrated a significant decrease in BDNF levels in both individuals with antepartum depression (SMD: -0.31; 95% CI: -0.48 to -0.13; p-value = 0.0008; I2  = 71%), and post-partum depression (SMD: -0.61; 95% CI: -0.99 to -0.22; p-value = 0.0002 I2  = 77%). Furthermore, a significantly higher rate of PND among individuals in the lowest BDNF quartile (OR: 2.64; 95% CI: 1.01 to 6.89; p-value = 0.05; I2  = 90%) was seen. The results of subgroup analyses showed a statistically significant effect of the depression assessment tool on overall heterogeneity between studies.

CONCLUSION

This systematic review and meta-analysis provide evidence of lower BDNF protein levels in individuals diagnosed with PND. The results indicate that BDNF dysregulation may play a part in the development of PND. More research is needed to understand the mechanisms behind this and explore potential therapeutic applications.

Temporal relationship between depression and cognitive decline in the elderly: a two-wave cross-lagged study in a Chinese sample

Objectives: Less information is available about the temporal relationship between depression in the elderly and cognitive decline. In the current study, we (1) evaluated the temporal association between depression and cognitive decline in older adults over a 4-year period; (2) indicated which cognitive domains have a strong temporal relationship with depression.Methods: Using data from China Family Panel Studies, we examined the relationship between depression and cognition among adults aged 65 and older with a cross-lagged design.Results: The results showed that initial depression affected subsequent cognitive function, especially immediate and delayed recall, but that cognition decline did not predict depression over time.Conclusion: The findings suggest that depression precedes cognitive decline in older adults, which is of great significance for the future research of mild cognitive impairment and dementia in the elderly.

Psilocybin induces acute and persisting alterations in immune status in healthy volunteers: An experimental, placebo-controlled study

Patients characterized by stress-related disorders such as depression display elevated circulating concentrations of pro-inflammatory cytokines and a hyperactive HPA axis. Psychedelics are demonstrating promising results in treatment of such disorders, however the mechanisms of their therapeutic effects are still unknown. To date the evidence of acute and persisting effects of psychedelics on immune functioning, HPA axis activity in response to stress, and associated psychological outcomes is preliminary. To address this, we conducted a placebo-controlled, parallel group design comprising of 60 healthy participants who received either placebo (n = 30) or 0.17 mg/kg psilocybin (n = 30). Blood samples were taken to assess acute and persisting (7 day) changes in immune status. Seven days' post-administration, participants in each treatment group were further subdivided: 15 underwent a stress induction protocol, and 15 underwent a control protocol. Ultra-high field (7-Tesla) magnetic resonance spectroscopy was used to assess whether acute changes in glutamate or glial activity were associated with changes in immune functioning. Finally, questionnaires assessed persisting self-report changes in mood and social behavior. Psilocybin immediately reduced concentrations of the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α), while other inflammatory markers (interleukin (IL)- 1β, IL-6, and C-reactive protein (CRP)) remained unchanged. Seven days later, TNF-α concentrations returned to baseline, while IL-6 and CRP concentrations were persistently reduced in the psilocybin group. Changes in the immune profile were related to acute neurometabolic activity as acute reductions in TNF-α were linked to lower concentrations of glutamate in the hippocampus. Additionally, the more of a reduction in IL-6 and CRP seven days after psilocybin, the more persisting positive mood and social effects participants reported. Regarding the stress response, after a psychosocial stressor, psilocybin did not significantly alter the stress response. Results are discussed in regards to the psychological and therapeutic effects of psilocybin demonstrated in ongoing patient trials.

Two-carba cyclic phosphatidic acid treatment promotes phenotypic switch from M1 to M2 microglia and prevents behavioral abnormalities in a mouse model of neuropsychiatric systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease associated with the production of double-stranded DNA (dsDNA) antibodies and other antibodies that predominantly affects women with a wide range of lesions. Although neuropsychiatric lupus erythematosus (NPSLE), characterized by neuropsychiatric symptoms related to cerebrovascular diseases or depression, ranks high in severity, no specific treatment has been defined. Two-carba cyclic phosphatidic acid (2ccPA), a derivative of cyclic phosphatidic acid, was isolated from the true slime mold Physarum polycephalum in 1992. 2ccPA treatment suppresses neuroinflammation and promotes tissue repair in mouse multiple sclerosis and traumatic brain injury models. In this study, we performed behavioral tests on MRL/lpr mice as an NPSLE model. MRL/lpr mice showed increased depression-like behaviors compared with control mice, which were significantly suppressed by 2ccPA treatment. The expression of CD68, an M1 phenotypic marker of microglia, was significantly elevated in the prefrontal cortex and hippocampus of MRL/lpr mice, which was significantly suppressed by 2ccPA treatment. In contrast, the expression of Arginase1, an M2 phenotypic marker of microglia, was significantly increased by 2ccPA treatment. Compared to control mice, MRL/lpr mice showed higher plasma levels of anti-dsDNA antibodies, which are mainly involved in SLE pathogenesis. 2ccPA treatment decreased these levels in the MRL/lpr mice. These results suggest that 2ccPA treatment suppresses behavioral abnormalities by promoting a microglial phenotypic switch from M1 to M2 in MRL/lpr mice.

Alterations of learning and memory are accompanied by alterations in the expression of 5-HT receptors, glucocorticoid receptor and brain-derived neurotrophic factor in different brain regions of an animal model of depression generated by neonatally male treatment with clomipramine in male rats

Depressive illness has been associated with impaired cognitive processes accompanied by reduced neurotrophin levels, especially brain-derived neurotrophic factor (BDNF), and dysfunctions in the hypothalamic-pituitary-adrenal (HPA) axis. In addition, depression is characterized by a decreased functioning of the serotonergic system due to changes in the activity or expression of its receptors including, most significantly, 5-HT1A, 5-HT2A, and 5-HT3 in brain regions that regulate mood, emotions, and memory, such as the prefrontal cortex, hippocampus, and amygdala. In this regard, rats treated with clomipramine (CMI) in the neonatal stage show depression-like behaviors that persist into adulthood; hence, this constitutes an adequate model of depression for exploring various molecular aspects associated with the etiology of this disorder. This, study, then, was designed to analyze the long-term effects of early postnatal exposure to CMI on the expression of 5-HT1A, 5-HT2A, and 5-HT3 receptors, as well as BDNF and GR in the following brain regions: PFC, amygdala, hippocampus, and hypothalamus, which could be related to alterations in memory and learning, as evaluated using the novel object recognition (NOR) and Morris water maze (MWM). Expression of the 5-HT1A, 5-HT2A, and 5-HT3 receptors, BDNF, and the glucocorticoid receptor (GR) was assessed by RT-qPCR in the four aforementioned brain regions, all of which play important roles in the control of memory and mood. Findings show that neonatal treatment with CMI causes alterations in memory and learning, as indicated by alterations in the results of the MWM and NOR tests. Expression of the 5-HT1A receptor increased in the hippocampus, amygdala, and hypothalamus, but decreased in the PFC, while the 5-HT2A and BDNF receptors decreased their expression in the PFC, amygdala, and hippocampus. There was no change in the expression of the 5-HT3 receptor. In addition, expression of GR in the hippocampus and PFC was low, but increased in the hypothalamus. Taken together, these data show that neonatal CMI treatment produces permanent molecular changes in brain regions related to learning and memory that could contribute to explaining the behavioral alterations observed in this model.

Roles of microglia in adult hippocampal neurogenesis in depression and their therapeutics

Adult hippocampal neurogenesis generates functional neurons from neural progenitor cells in the hippocampal dentate gyrus (DG) to complement and repair neurons and neural circuits, thus benefiting the treatment of depression. Increasing evidence has shown that aberrant microglial activity can disrupt the appropriate formation and development of functional properties of neurogenesis, which will play a crucial role in the occurrence and development of depression. However, the mechanisms of the crosstalk between microglia and adult hippocampal neurogenesis in depression are not yet fully understood. Therefore, in this review, we first introduce recent discoveries regarding the roles of microglia and adult hippocampal neurogenesis in the etiology of depression. Then, we systematically discuss the possible mechanisms of how microglia regulate adult hippocampal neurogenesis in depression according to recent studies, which involve toll-like receptors, microglial polarization, fractalkine-C-X3-C motif chemokine receptor 1, hypothalamic-pituitary-adrenal axis, cytokines, brain-derived neurotrophic factor, and the microbiota-gut-brain axis, etc. In addition, we summarize the promising drugs that could improve the adult hippocampal neurogenesis by regulating the microglia. These findings will help us understand the complicated pathological mechanisms of depression and shed light on the development of new treatment strategies for this disease.

A Study of Brain Function Characteristics of Service Members at High Risk for Accidents in the Military

Military accidents are often associated with stress and depressive psychological conditions among soldiers, and they often fail to adapt to military life. Therefore, this study analyzes whether there are differences in EEG and pulse wave indices between general soldiers and three groups of soldiers who have not adapted to military life and are at risk of accidents. Data collection was carried out using a questionnaire and a device that can measure EEG and pulse waves, and data analysis was performed using SPSS. The results showed that the concentration level and brain activity indices were higher in the general soldiers and the soldiers in the first stage of accident risk. The body stress index was higher for each stage of accident risk, and the physical vitality index was higher for general soldiers. Therefore, it can be seen that soldiers who have not adapted to military life and are at risk of accidents have somewhat lower concentration and brain activity than general soldiers, and have symptoms of stress and lethargy. The results of this study will contribute to reducing human accidents through EEG and pulse wave measurements not only in the military but also in occupations with a high risk of accidents such as construction.

Smaller cornu ammonis (CA3) as a potential risk factor for suicidal behavior in mood disorders

Mood disorders and suicidal behavior have moderate heritability and familial transmission, and are associated with smaller hippocampal volumes. However, it is unclear whether hippocampal alterations reflect heritable risk or epigenetic effects of childhood adversity, compensatory mechanisms, illness-related changes, or treatment effects. We sought to separate the relationships of hippocampal substructure volumes to mood disorder, suicidal behavior, and risk and resilience to both by examining high familial risk individuals (HR) who have passed the age of greatest risk for psychopathology onset. Structural brain imaging and hippocampal substructure segmentation quantified Cornu Ammonis (CA1-4), dentate gyrus, and subiculum gray matter volumes in healthy volunteers (HV, N = 25) and three groups with one or more relatives reporting early-onset mood disorder and suicide attempt: 1. Unaffected HR (N = 20); 2. HR with lifetime mood disorder and no suicide attempt (HR-MOOD, N = 25); and 3. HR with lifetime mood disorder and a previous suicide attempt (HR-MOOD + SA, N = 18). Findings were tested in an independent cohort not selected for family history (HV, N = 47; MOOD, N = 44; and MOOD + SA, N = 21). Lower CA3 volume was found in HR (vs. HV), consistent with the direction of previously published findings in MOOD+SA (vs. HV and MOOD), suggesting the finding reflects a familial biological risk marker, not illness or treatment-related sequelae, of suicidal behavior and mood disorder. Familial suicide risk may be mediated in part by smaller CA3 volume. The structure may serve as a risk indicator and therapeutic target for suicide prevention strategies in high-risk families.

Gut microbiota changes require vagus nerve integrity to promote depressive-like behaviors in mice

Chronic stress constitutes a major risk factor for depression that can disrupt various aspects of homeostasis, including the gut microbiome (GM). We have recently shown that GM imbalance affects adult hippocampal (HPC) neurogenesis and induces depression-like behaviors, with the exact mechanisms being under active investigation. Here we hypothesized that the vagus nerve (VN), a key bidirectional route of communication between the gut and the brain, could relay the effects of stress-induced GM changes on HPC plasticity and behavior. We used fecal samples derived from mice that sustained unpredictable chronic mild stress (UCMS) to inoculate healthy mice and assess standard behavioral readouts for anxiety- and depressive-like behavior, conduct histological and molecular analyses for adult HPC neurogenesis and evaluate neurotransmission pathways and neuroinflammation. To study the potential role of the VN in mediating the effects of GM changes on brain functions and behavior, we used mice that sustained subdiaphragmatic vagotomy (Vx) prior the GM transfer. We found that inoculation of healthy mice with GM from UCMS mice activates the VN and induces early and sustained changes in both serotonin and dopamine neurotransmission pathways in the brainstem and HPC. These changes are associated with prompt and persistent deficits in adult HPC neurogenesis and induce early and sustained neuroinflammatory responses in the HPC. Remarkably, Vx abrogates adult HPC neurogenesis deficits, neuroinflammation and depressive-like behavior, suggesting that vagal afferent pathways are necessary to drive GM-mediated effects on the brain.

Repetitive transcranial magnetic stimulation and fluoxetine reverse depressive-like behavior but with differential effects on Olig2-positive cells in chronically stressed mice

Depression is a mood disorder coursing with several behavioral, cellular, and neurochemical alterations. The negative impact of chronic stress may precipitate this neuropsychiatric disorder. Interestingly, downregulation of oligodendrocyte-related genes, abnormal myelin structure, and reduced numbers and density of oligodendrocytes in the limbic system have been identified in patients diagnosed with depression, but also in rodents exposed to chronic mild stress (CMS). Several reports have emphasized the importance of pharmacological or stimulation-related strategies in influencing oligodendrocytes in the hippocampal neurogenic niche. Repetitive transcranial magnetic stimulation (rTMS) has gained attention as an intervention to revert depression. Here, we hypothesized that 5 Hz (Hz) of rTMS or Fluoxetine (Flx) would revert depressive-like behaviors by influencing oligodendrocytes and revert neurogenic alterations caused by CMS in female Swiss Webster mice. Our results showed that 5 Hz rTMS or Flx revert depressive-like behavior. Only rTMS influenced oligodendrocytes by increasing the number of Olig2-positive cells in the hilus of the dentate gyrus and the prefrontal cortex. However, both strategies exerted effects on some events of the hippocampal neurogenic processes, such as cell proliferation (Ki67-positive cells), survival (CldU-positive cells), and intermediate stages (doublecortin-positive cells) along the dorsal-ventral axis of this region. Interestingly, the combination of rTMS-Flx exerted antidepressant-like effects, but the increased number of Olig2-positive cells observed in mice treated only with rTMS was canceled. However, rTMS-Flx exerted a synergistic effect by increasing the number of Ki67-positive cells. It also increased the number of CldU- and doublecortin-positive cells in the dentate gyrus. Our results demonstrate that 5 Hz rTMS has beneficial effects, as it reverted depressive-like behavior by increasing the number of Olig2-positive cells and reverting the decrement in hippocampal neurogenesis in CMS-exposed mice. Nevertheless, the effects of rTMS on other glial cells require further investigation.

Exploring the Therapeutic Effect of Neurotrophins and Neuropeptides in Neurodegenerative Diseases: at a Glance

Neurotrophins and neuropeptides are the essential regulators of peripheral nociceptive nerves that help to induce, sensitize, and maintain pain. Neuropeptide has a neuroprotective impact as it increases trophic support, regulates calcium homeostasis, and reduces excitotoxicity and neuroinflammation. In contrast, neurotrophins target neurons afflicted by ischemia, epilepsy, depression, and eating disorders, among other neuropsychiatric conditions. Neurotrophins are reported to inhibit neuronal death. Strategies maintained for "brain-derived neurotrophic factor (BDNF) therapies" are to upregulate BDNF levels using the delivery of protein and genes or compounds that target BDNF production and boosting BDNF signals by expanding with BDNF mimetics. This review discusses the mechanisms of neurotrophins and neuropeptides against acute neural damage as well as highlighting neuropeptides as a potential therapeutic agent against Parkinson's disease (PD), Huntington's disease (HD), Alzheimer's disease (AD), and Machado-Joseph disease (MJD), the signaling pathways affected by neurotrophins and their receptors in both standard and diseased CNS systems, and future perspectives that can lead to the potent application of neurotrophins and neuropeptides in neurodegenerative diseases (NDs).

Quantifying numerical and spatial reliability of hippocampal and amygdala subdivisions in FreeSurfer

On-going, large-scale neuroimaging initiatives can aid in uncovering neurobiological causes and correlates of poor mental health, disease pathology, and many other important conditions. As projects grow in scale with hundreds, even thousands, of individual participants and scans collected, quantification of brain structures by automated algorithms is becoming the only truly tractable approach. Here, we assessed the spatial and numerical reliability for newly deployed automated segmentation of hippocampal subfields and amygdala nuclei in FreeSurfer 7. In a sample of participants with repeated structural imaging scans (N = 928), we found numerical reliability (as assessed by intraclass correlations, ICCs) was reasonable. Approximately 95% of hippocampal subfields had "excellent" numerical reliability (ICCs ≥ 0.90), while only 67% of amygdala subnuclei met this same threshold. In terms of spatial reliability, 58% of hippocampal subfields and 44% of amygdala subnuclei had Dice coefficients ≥ 0.70. Notably, multiple regions had poor numerical and/or spatial reliability. We also examined correlations between spatial reliability and person-level factors (e.g., participant age; T1 image quality). Both sex and image scan quality were related to variations in spatial reliability metrics. Examined collectively, our work suggests caution should be exercised for a few hippocampal subfields and amygdala nuclei with more variable reliability.

Long-term dietary folic acid supplementation attenuated aging-induced hippocampus atrophy and promoted glucose uptake in 25-month-old rats with cognitive decline

The brain has high energy demand making it sensitive to changes in energy fuel supply. Aging shrinks brain volume, decreases glucose uptake availability of the brain, and finally, causes cognitive dysfunction. Folic acid supplementation delayed cognitive decline and neurodegeneration. However, whether folic acid affects brain energy metabolism and structural changes is unclear. The study aimed to determine if long-term dietary folic acid supplementation could alleviate age-related cognitive decline by attenuating hippocampus atrophy and promoting brain glucose uptake in Sprague-Dawley (SD) rats. According to folic acid levels in diet, three-month-old male SD rats were randomly divided into four intervention groups for 22 months in equal numbers: folic acid-deficient diet (FA-D) group, folic acid-normal diet (FA-N) group, low folic acid-supplemented diet (FA-L) group, and high folic acid-supplemented diet (FA-H) group. The results showed that serum folate concentrations decreased and serum homocysteine (Hcy) concentrations increased with age, and dietary folic acid supplementation increased serum folate concentrations and decreased Hcy concentrations at 11, 18, and 22 months of intervention. Dietary folic acid supplementation attenuated aging-induced hippocampus atrophy, which was showed by higher fractional anisotropy and lower mean diffusivity in the hippocampus, increased brain ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) uptake, then stimulated neuronal survival, and alleviated age-related cognitive decline in SD rats. In conclusion, long-term dietary folic acid supplementation alleviated age-related cognitive decline by attenuating hippocampus atrophy and promoting brain glucose uptake in SD rats.

Abnormal evidence accumulation underlies the positive memory deficit in depression

Healthy adults show better memory for low-arousal positive versus negative stimuli, but depression compromises this positive memory advantage. Existing studies are limited by small samples or analyses that provide limited insight into underlying mechanisms. Our study addresses these concerns by using a multistaged analysis, including diffusion modeling, to identify precise psychological processes underlying the positive memory advantage and its disruption by depression in a large sample. A total of 1,358 participants completed the BDI-II (Beck et al., 1996) and an emotional memory task. At encoding, participants judged whether positive and negative words were positive or self-descriptive. After a free recall test, participants viewed an equal mix of studied and unstudied words and judged whether each was "old" or "new"; if judged "old," they indicated whether the study source was a valence or self-reference judgment. We replicate the positive memory advantage and its decrease in depression in recall, recognition, and source accuracy. The hierarchical drift diffusion model (HDDM; Wiecki et al., 2013) revealed that higher BDI-II scores are associated with more efficient evidence accumulation for negative words in the recognition and source memory tasks. By contrast, evidence accumulation for positive words is unaffected by BDI-II during the recognition task but becomes less efficient with increased BDI-II during the source memory task. In conclusion, in a well-controlled design with a large sample, we find that depression reduces the positive memory advantage. HDDM analyses suggest that this reflects differential effects of depression on the speed of evidence accumulation during the retrieval of positive versus negative memories. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Lack of bombesin receptor-activated protein homologous protein impairs hippocampal synaptic plasticity and promotes chronic unpredictable mild stress induced behavioral changes in mice

Bombesin receptor-activated protein (BRAP) and its homologous protein in mice, which is encoded by bc004004 gene, were expressed abundantly in brain tissues with unknown functions. We treated bc004004^-/- mice with chronic unpredictable mild stress (CUMS) to test whether those mice were more vulnerable to stress-related disorders. The results of forced swimming test, sucrose preference test, and open field test showed that after being treated with CUMS for 28 days or 35 days both bc004004^-/- and bc004004^+/+ mice exhibited behavioural changes and there was no significant difference between bc004004^+/+ and bc004004^-/-. However, behavioural changes were observed only in bc004004^-/- mice after being exposed to CUMS for 21 days, but not in bc004004^+/+ after 21-day CUMS exposure, indicating that lack of BRAP homologous protein may cause vulnerability to stress-related disorders in mice. In addition, bc004004^-/- mice showed a reduction in recognition memory as revealed by novel object recognition test. Since memory changes and stress related behavioural changes are all closely related to the hippocampus function we further analyzed the changes of dendrites and synapses of hippocampal neurons as well as expression levels of some proteins closely related to synaptic function. bc004004^-/- mice exhibited decreased dendritic lengths and increased amount of immature spines, as well as altered expression pattern of synaptic related proteins including GluN2A, synaptophysin and BDNF in the hippocampus. Those findings suggest that BRAP homologous protein may have a protective effect on the behavioural response to stress via regulating dendritic spine formation and synaptic plasticity in the hippocampus.

The sex-dependent response to psychosocial stress and ischaemic heart disease

Stress is an important risk factor for modern chronic diseases, with distinct influences in males and females. The sex specificity of the mammalian stress response contributes to the sex-dependent development and impacts of coronary artery disease (CAD). Compared to men, women appear to have greater susceptibility to chronic forms of psychosocial stress, extending beyond an increased incidence of mood disorders to include a 2- to 4-fold higher risk of stress-dependent myocardial infarction in women, and up to 10-fold higher risk of Takotsubo syndrome-a stress-dependent coronary-myocardial disorder most prevalent in post-menopausal women. Sex differences arise at all levels of the stress response: from initial perception of stress to behavioural, cognitive, and affective responses and longer-term disease outcomes. These fundamental differences involve interactions between chromosomal and gonadal determinants, (mal)adaptive epigenetic modulation across the lifespan (particularly in early life), and the extrinsic influences of socio-cultural, economic, and environmental factors. Pre-clinical investigations of biological mechanisms support distinct early life programming and a heightened corticolimbic-noradrenaline-neuroinflammatory reactivity in females vs. males, among implicated determinants of the chronic stress response. Unravelling the intrinsic molecular, cellular and systems biological basis of these differences, and their interactions with external lifestyle/socio-cultural determinants, can guide preventative and therapeutic strategies to better target coronary heart disease in a tailored sex-specific manner.

Individual variation in brain network topology is linked to course of illness in major depressive disorder

Major depressive disorder (MDD) is a chronic and highly recurrent disorder. The functional connectivity in depression is affected by the cumulative effect of course of illness. However, previous neuroimaging studies on abnormal functional connection have not mainly focused on the disease duration, which is seen as a secondary factor. Here, we used a data-driven analysis (multivariate distance matrix regression) to examine the relationship between the course of illness and resting-state functional dysconnectivity in MDD. This method identified a region in the anterior cingulate cortex, which is most linked to course of illness. Specifically, follow-up seed analyses show this phenomenon resulted from the individual differences in the topological distribution of three networks. In individuals with short-duration MDD, the connection to the default mode network was strong. By contrast, individuals with long-duration MDD showed hyperconnectivity to the ventral attention network and the frontoparietal network. These results emphasized the centrality of the anterior cingulate cortex in the pathophysiology of the increased course of illness and implied critical links between network topography and pathological duration. Thus, dissociable patterns of connectivity of the anterior cingulate cortex is an important dimension feature of the disease process of depression.

Ameliorated Neurogenesis Deficits in Dentate Gyrus May Underly the Pronounced Antidepressant Effect of TREK-1 Potassium Channel Blockade in Rats with Depressive-like Behavior

Depression is considered to be the most common mental disorder and is probed by several studies that chronic mild stress contributes to depression, and fortunately, most antidepressants ameliorate depressive-like behavior accompanied with reversed hippocampal neurogenesis defects. In our present study, we confirmed that different antidepressants repaired the stress-induced neuronal and behavioral deficits by modulating adult hippocampal neurogenesis. Antidepressant treatment restored the adult hippocampal neurodegeneration, which was impaired by chronic unpredicted mild stress displaying decreased proliferation and neuronal differentiation but increased apoptosis of newly formed neurons in dentate gyrus. Notably, sucrose preference ratio significantly correlated with both neuronal differentiation proportion and newborn apoptosis proportion, suggesting a mechanistic relationship between neurogenesis and behavior. Indeed, the neotype TREK-1 potassium channel blocker expressed an earlier and pronounced antidepressant manifestation compared to the traditional selective serotonin-reuptake inhibitors fluoxetine. We therefore conclude that the administration of TREK-1 potassium channel antagonism can reverse the depressive deficits caused by chronic stress quickly via regulation of adult hippocampal neurogenesis.

The role of reelin in the pathological mechanism of depression from clinical to rodents

Major depressive disorder (MDD) is a devastating mental illness and the leading cause of disability worldwide. Previous studies have suggested that synaptic plasticity in the hippocampus plays an important role in depression pathogenesis. Reelin is expressed mainly in the frontal lobe and hippocampus, and is closely associated with neurodevelopment and synaptic plasticity. However, few studies have investigated its role in MDD combining clinical trials and animal experiments. We show that in a clinical trial, plasma reelin levels decreased in patients with first-episode drug-naïve MDD and increased after treatment; further, plasma reelin levels allowed to distinguish drug-naïve patients with first-episode MDD from healthy individuals. In rats, chronic mild and unpredictable stress led to a decrease in both reelin mRNA and protein levels in the hippocampus, which could be reversed by vortioxetine. Subsequent experiments confirmed that the reelin-ApoER2-NR2A /NR2B pathway regulates hippocampal synaptic plasticity and may be involved in depression or antidepressant responses. Our work contributes to a deeper understanding of MDD pathogenesis and provides new evidence that reelin should be considered a potential therapeutic target for MDD.

Association of Oxidative Stress-Induced Nucleic Acid Damage With Psychiatric Disorders in Adults: A Systematic Review and Meta-analysis

IMPORTANCE

Nucleic acid damage from oxidative stress (NA-OXS) may be a molecular mechanism driving the severely increased morbidity and mortality from somatic causes in adults with psychiatric disorders.

OBJECTIVE

To systematically retrieve and analyze data on NA-OXS across the psychiatric disorder diagnostic spectrum.

DATA SOURCES

The PubMed, Embase, and PsycINFO databases were searched from inception to November 16, 2021. A hand search of reference lists of relevant articles was also performed.

STUDY SELECTION

Key study inclusion criteria in this meta-analysis were as follows: adult human study population, measurement of any marker of DNA or RNA damage from oxidative stress, and either a (1) cross-sectional design comparing patients with psychiatric disorders (any diagnosis) with a control group or (2) prospective intervention. Two authors screened the studies, and 2 senior authors read the relevant articles in full and assessed them for eligibility.

DATA EXTRACTION AND SYNTHESIS

The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed. Two authors performed data extraction independently, and a senior coauthor was consulted in cases of disagreement. Data were synthesized with random-effects and multilevel meta-analyses.

MAIN OUTCOMES AND MEASURES

The predefined hypothesis was that individuals with psychiatric disorders have increased NA-OXS levels. The main outcome was the standardized mean differences (SMDs) among patients and controls in nucleic acid oxidation markers compared across diagnostic groups. Analyses were divided into combinations of biological matrices and nucleic acids.

RESULTS

Eighty-two studies fulfilled the inclusion criteria, comprising 205 patient vs control group comparisons and a total of 10 151 patient and 10 532 control observations. Overall, the data showed that patients with psychiatric disorders had higher NA-OXS levels vs controls across matrices and molecules. Pooled effect sizes ranged from moderate for urinary DNA markers (SMD = 0.44 [95% CI, 0.20-0.68]; P < .001) to very large for blood cell DNA markers (SMD = 1.12 [95% CI, 0.69-1.55; P < .001). Higher NA-OXS levels were observed among patients with dementias followed by psychotic and bipolar disorders. Sensitivity analyses excluding low-quality studies did not materially alter the results. Intervention studies were few and too heterogenous for meaningful meta-analysis.

CONCLUSIONS AND RELEVANCE

The results of this meta-analysis suggest that there is an association with increased NA-OXS levels in individuals across the psychiatric disorder diagnostic spectrum. NA-OXS may play a role in the somatic morbidity and mortality observed among individuals with psychiatric disorders.

Association Between the C4 Binding Protein Level and White Matter Integrity in Major Depressive Disorder

OBJECTIVE

Considerable evidence suggests that neuroinflammation plays an important role in the pathophysiology of major depressive disorder (MDD). However, the relationship between serum C4 binding protein (C4BP) and white matter (WM) tract integrity in MDD has not been investigated.

METHODS

We obtained diffusion tensor images of 44 patients with MDD and 44 healthy controls and performed TRActs Constrained by UnderLying Anatomy (TRACULA) analysis to assess WM tract integrity. Serum C4-binding protein alpha chain (C4BPA) and C4- binding protein beta chain (C4BPB) levels were measured and in-between group comparisons were obtained. The correlation between serum C4BP levels and WM tract integrity was examined.

RESULTS

In comparison to healthy controls, both serum C4BPA and C4BPB were higher in MDD. Also, fractional anisotropy (FA) was increased in the left cingulum-angular bundle (CAB) in MDD, but not healthy controls (HCs). A significant correlation was found between serum C4BP and FA levels in the right cingulum-cingulate gyrus bundle (CCG) in MDD.

CONCLUSION

This study is the first to investigate the correlation between serum C4BP levels and WM tract integrity in MDD. We identified an increase in WM integrity in the left CAB region in MDD. Furthermore, serum C4BP levels were higher in MDD, and this finding correlated with increased WM integrity in the right CCG region.

Allostatic load as a mediator of childhood maltreatment and adulthood depressive symptoms: A longitudinal analysis

Childhood maltreatment (CM) is associated with several negative outcomes in adulthood, including major depression. People who experience CM that go on to develop symptoms of major depression in adulthood tend to have earlier depressive symptom onset and greater symptom severity than those who do not experience CM. Studies have utilized allostatic load (AL) to understand how CM "gets under the skin" to contribute to depressive symptoms. However, studies largely utilize cross-sectional designs and limited biomarkers. The present study uses data from Wave 2 and Wave 3 of the Midlife Development in the United States study in regression-based analyses, examining if AL mediates the relationship between CM and the number of depressive symptoms in adulthood. AL was measured at Wave 2 using the system risk method with 27 biomarkers across seven different systems. CM was measured using the Childhood Trauma Questionnaire at Wave 2. Number of depressive symptoms were measured using the Composite International Diagnostic Interview-Short Form at Wave 3. Past month perceived stress, age, household income, education, sex, racial/ethnic identity, and current prescription medication use at Wave 2 were included as controls. Analyses identified that CM was associated with AL cross-sectionally, and that both CM and AL at were associated with the number of depressive symptoms prospectively. AL partially mediated the effects of CM on the number of depressive symptoms. The present study is the first to identify the mediating role of AL in the relationship between CM and adulthood depressive symptoms in a longitudinal design.

Memory-related neurophysiological mechanisms in the hippocampus underlying stress susceptibility

Stress-induced psychiatric symptoms, such as increased anxiety, decreased sociality, and depression, differ considerably across individuals. The cognitive model of depression proposes that biased negative memory is a crucial determinant in the development of mental stress-induced disorders. Accumulating evidence from both clinical and animal studies has demonstrated that such biased memory processing could be triggered by the hippocampus, a region well known to be involved in declarative memories. This review mainly describes how memory-related neurophysiological mechanisms in the hippocampus and their interactions with other related brain regions are involved in the regulation of stress susceptibility and discusses potential interventions to prevent and treat stress-related psychiatric symptoms. Further neurophysiological insights based on memory mechanisms are expected to devise personalized prevention and therapy to confer stress resilience.

Activation of liver X receptors protects oligodendrocytes in CA3 of stress-induced mice

Depression is a complex disorder that is associated with various structural abnormalities. Oligodendrocyte (OL) dysfunction is associated with the pathogenesis of depression and the promotion of hippocampal oligodendrocyte maturation and myelination could be a novel therapeutic strategy for ameliorating depressive behaviors. Recent studies have shown that activation of liver X receptors (LXRs) by GW3965 improves depressive phenotypes, but the effects of GW3965 on OL function and myelination in the hippocampus of depression remain relatively unclear. To address this issue, we investigated the effects of GW3965 on mature OL in the hippocampus and on the myelin sheaths of mice subjected to chronic unpredictable stress (CUS). Behavioral tests were performed to assess depressive behaviors. Then, the number of mature OLs (CC1⁺) in each hippocampal subregion was precisely quantified with immunohistochemical and stereological methods, and the density of newborn mature OLs (BrdU⁺/Olig2⁺/CC1⁺ cells) in each hippocampal subregion was quantified with immunofluorescence. In addition, myelin basic protein (MBP) staining intensity in the cornu ammonis 3 (CA3) region was assessed by using immunofluorescence. We found that both the number of CC1⁺ OLs and the density of BrdU⁺/Olig2⁺/CC1⁺ cells were obviously decreased in each hippocampal subregion of mice subjected to CUS, and 4 weeks of GW3965 treatment reversed these effects only in the CA3 region. Furthermore, the decreased MBP expression in the CA3 region of mice subjected to CUS was ameliorated by GW3965 treatment. Collectively, these results suggested that improvement of OL maturation and enhancement of myelination may be structural mechanisms underlying the antidepressant effects of LXR agonists.

Distributed genetic architecture across the hippocampal formation implies common neuropathology across brain disorders

Despite its major role in complex human functions across the lifespan, most notably navigation, learning and memory, much of the genetic architecture of the hippocampal formation is currently unexplored. Here, through multivariate genome-wide association analysis in volumetric data from 35,411 white British individuals, we reveal 177 unique genetic loci with distributed associations across the hippocampal formation. We identify genetic overlap with eight brain disorders with typical onset at different stages of life, where common genes suggest partly age- and disorder-independent mechanisms underlying hippocampal pathology.

Impaired allocentric spatial memory in patients with affective disorders

BACKGROUND

Memory disturbances are frequent in unipolar depression (UD) and bipolar disorder (BD) and may comprise important predisposing and maintaining factors. Previous studies have demonstrated hippocampal abnormalities in UD and BD but there is a lack of studies specifically assessing hippocampus-dependent memory.

METHODS

We used a virtual task to assess hippocampus-dependent (allocentric) vs non-hipppocampal (egocentric) spatial memory in remitted and partially remitted patients with UD or BD (N = 22) and a healthy control group (N = 32). Participants also completed a range of standard neuropsychological and functional assessments.

RESULTS

Participants in the UD/BD group showed selective impairments on high-load hippocampal (allocentric) memory compared to egocentric memory and this effect was independent of residual mood symptoms. Across both samples, both allocentric and egocentric spatial memory correlated with more general measures of memory and other aspects of cognition measured on standard neuropsychological tests but only high-load allocentric memory showed a significant relationship with functional capacity.

CONCLUSION

Results show a selective impairment in high-load allocentric spatial memory compared to egocentric memory in the patient group, suggesting impaired hippocampal functioning in patients with remitted UD/BD.

Maternal separation induced resilience to depression and spatial memory deficit despite intensifying hippocampal inflammatory responses to chronic social defeat stress in young adult male rats

Early life adversity has been suggested to affect neuroendocrine responses to subsequent stressors and accordingly vulnerability for behavioral disorders. This is the first work to study the effects of maternal separation (MS) stress on the co-occurrence of depression and cognitive impairments along with hippocampal inflammatory response under chronic social defeat stress (CSDS) in young adult male rats. During the first two postnatal weeks, the male pups were either exposed to MS or left undisturbed with their mothers (Std). Subsequently, starting on postnatal day 50, the animals of each group were either left undisturbed in the standard group housing (Con) or underwent CSDS for three weeks. Totally, there were four groups (n = 10/group), namely Std-Con, Ms-Con, Std-CSDS, and MS-CSDS. Pup retrieval test was performed on daily basis from PND1 to PND14. During the last week of the CSDS exposure, in the light phase, the behavioral tests and the retro-orbital blood sampling were performed to assess basal plasma corticosterone levels. Afterwards, the hippocampus of the animals was removed to measure the interleukin 1β (IL-1β) content. Exposure to CSDS increased the plasma corticosterone levels and induced social avoidance along with memory deficit. Maternal separation intensified hippocampal IL-1β contents as well as the plasma corticosterone levels in response to CSDS. Meanwhile, it facilitated the spatial learning and potentiated resilience to social avoidance and memory deficit. In conclusion, although maternal separation increased the basal plasma corticosterone levels, it could facilitate the learning process and induce resilience to the onset of depression and memory deficit in response to CSDS, probably through the compensatory increase in maternal care and the induction of mild hippocampal inflammatory response.

Association of disease course and brain structural alterations in major depressive disorder

INTRODUCTION

The investigation of disease course-associated brain structural alterations in Major Depressive Disorder (MDD) have resulted in heterogeneous findings, possibly due to low reliability of single clinical variables used for defining disease course. The present study employed a principal component analysis (PCA) on multiple clinical variables to investigate effects of cumulative lifetime illness burden on brain structure in a large and heterogeneous sample of MDD patients.

METHODS

Gray matter volumes (GMV) was estimated in n = 681 MDD patients (mean age: 35.87 years; SD = 12.89; 66.6% female) using voxel-based-morphometry. Five clinical variables were included in a PCA to obtain components reflecting disease course to associate resulting components with GMVs.

RESULTS

The PCA yielded two main components: Hospitalization reflected by patients' frequency and duration of inpatient treatment and Duration of Illness reflected by the frequency and duration of depressive episodes. Hospitalization revealed negative associations with bilateral dorsolateral prefrontal cortex (DLPFC) and left insula volumes. Duration of Illness showed significant negative associations with left hippocampus and right DLPFC volumes. Results in the DLPFC and hippocampus remained significant after additional control for depressive symptom severity, psychopharmacotherapy, psychiatric comorbidities, and remission status.

CONCLUSION

This study shows that a more severe and chronic lifetime disease course in MDD is associated with reduced volume in brain regions relevant for executive and cognitive functions and emotion regulation in a large sample of patients representing the broad heterogeneity of MDD disease course. These findings were only partly influenced by other clinical characteristics (e.g., remission status, psychopharmacological treatment).

Neurobiology of Depression: Chronic Stress Alters the Glutamatergic System in the Brain-Focusing on AMPA Receptor

Major depressive disorder (MDD) is a common neuropsychiatric disorder affecting the mood and mental well-being. Its pathophysiology remains elusive due to the complexity and heterogeneity of this disorder that affects millions of individuals worldwide. Chronic stress is frequently cited as the one of the risk factors for MDD. To date, the conventional monoaminergic theory (serotonin, norepinephrine, and/or dopamine dysregulation) has received the most attention in the treatment of MDD, and all available classes of antidepressants target these monoaminergic systems. However, the contributions of other neurotransmitter systems in MDD have been widely reported. Emerging preclinical and clinical findings reveal that maladaptive glutamatergic neurotransmission might underlie the pathophysiology of MDD, thus revealing its critical role in the neurobiology of MDD and as the therapeutic target. Aiming beyond the monoaminergic hypothesis, studies of the neurobiological mechanisms underlying the stress-induced impairment of AMPA (a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid)-glutamatergic neurotransmission in the brain could provide novel insights for the development of a new generation of antidepressants without the detrimental side effects. Here, the authors reviewed the recent literature focusing on the role of AMPA-glutamatergic neurotransmission in stress-induced maladaptive responses in emotional and mood-associated brain regions, including the hippocampus, amygdala, prefrontal cortex, nucleus accumbens and periaqueductal gray.

Sex Differences in Major Depressive Disorder (MDD) and Preclinical Animal Models for the Study of Depression

Depression and related mood disorders constitute an enormous burden on health, quality of life, and the global economy, and women have roughly twice the lifetime risk of men for experiencing depression. Here, we review sex differences in human brain physiology that may be connected to the increased susceptibility of women to major depressive disorder (MDD). Moreover, we summarize decades of preclinical research using animal models for the study of mood dysfunction that uncover some of the potential molecular, cellular, and circuit-level mechanisms that may underlie sex differences and disease etiology. We place particular emphasis on a series of recent studies demonstrating the central contribution of the circuit projecting from ventral hippocampus to nucleus accumbens and how inherent sex differences in the excitability of this circuit may predict and drive depression-related behaviors. The findings covered in this review underscore the continued need for studies using preclinical models and circuit-specific strategies for uncovering molecular and physiological mechanisms that could lead to potential sex-specific diagnosis, prognosis, prevention, and/or treatments for MDD and other mood disorders.