Illness progression, recent stress, and morphometry of hippocampal subfields and medial prefrontal cortex in major depression

Psilocybin has a narrow therapeutic window as an antidepressant treatment

Psilocybin, a naturally occurring psychedelic compound in magic mushrooms, shows promise as a novel intervention with a single administration inducing rapid and long-lasting antidepressant effects. However, there are limited studies on the optimal dosing required for the beneficial effects of psilocybin given its side effects. To address this gap, we investigated in Wistar rats whether a single psilocybin administration (0.1, 0.32, 1.0, and 3.2 mg/kg) had antidepressant-like effects in the forced swim test (FST), a pro-social effect in the social interaction test (SIT), and the ability to alter pleasure using the sucrose preference test (SPT). We also examined the dose-response relationships of psilocybin on the head-twitch response (HTR), locomotor activity, body temperature, and weight gain. Furthermore, we explored whether the brain-derived neurotrophic factor (BDNF) levels in the hippocampus and prefrontal cortex (PFC) paralleled the behavioral changes observed after psilocybin. In the FST, psilocybin induced dose-dependent inverted-U-shaped responses with only the intermediate dose of 0.32 mg/kg producing short and long-term antidepressant-like effects. A similar pattern was observed for the SIT, the SPT, and the HTR. In contrast, the high doses of psilocybin (1.0 and 3.2 mg/kg), while deprived of anti-depressant-like activity, significantly reduced body temperature, locomotor activity, and body weight gain. BDNF levels in the hippocampus and PFC increased dose-dependently after psilocybin, but linearly suggesting a dissociation between high BDNF levels and the observed antidepressant-like behaviors. Our results indicated that there is a narrow window for the therapeutic potential of psilocybin, with 0.32 mg/kg effectively producing antidepressant-like effects without the accompanying adverse effects observed only at higher doses.

Brain structural correlates of an impending initial major depressive episode

Neuroimaging research has yet to elucidate whether reported gray matter volume (GMV) alterations in major depressive disorder (MDD) exist already before the onset of the first episode. Recruitment of presently healthy individuals with a subsequent transition to MDD (converters) is extremely challenging but crucial to gain insights into neurobiological vulnerability. Hence, we compared converters to patients with MDD and sustained healthy controls (HC) to distinguish pre-existing neurobiological markers from those emerging later in the course of depression. Combining two clinical cohorts (n = 1709), voxel-based morphometry was utilized to analyze GMV of n = 45 converters, n = 748 patients with MDD, and n = 916 HC in a region-of-interest approach and exploratory whole-brain. By contrasting the subgroups and considering both remission state and reported recurrence at a 2-year clinical follow-up, we stepwise disentangled effects of (1) vulnerability, (2) the acute depressive state, and (3) an initial vs. a recurrent episode. Analyses revealed higher amygdala GMV in converters relative to HC (ptfce-FWE = 0.037, d = 0.447) and patients (ptfce-FWE = 0.005, d = 0.508), remaining significant when compared to remitted patients with imminent recurrence. Lower GMV in the dorsolateral prefrontal cortex (ptfce-FWE < 0.001, d = 0.188) and insula (ptfce-FWE = 0.010, d = 0.186) emerged in patients relative to HC but not to converters, driven by patients with acute MDD. By examining one of the largest available converter samples in psychiatric neuroimaging, this study allowed a first determination of neural markers for an impending initial depressive episode. Our findings suggest a temporary vulnerability, which in combination with other common risk factors might facilitate prediction and in turn improve prevention of depression.

Proteomics analysis in rats reveals convergent mechanisms between major depressive disorder and dietary zinc deficiency

BACKGROUND

Preclinical and clinical studies have shown that dietary zinc deficiency can lead to symptoms similar to those observed in major depressive disorder (MDD). However, the underlying molecular mechanisms remain unclear. To investigate these mechanisms, we examined proteomic changes in the prefrontal cortex (PFC) and hippocampus (HP) of rats, two critical brain regions implicated in the pathophysiology of depression.

METHODS

Rats were fed diets either adequate in zinc (ZnA, 50 mg Zn/kg) or deficient in zinc (ZnD, <3 mg/kg) for four weeks. High-throughput proteomic analysis was used to detect changes in protein expression, supplemented by enzyme activity assay for mitochondrial complexes I and IV, examining their functional impacts.

RESULTS

ZnD led to significant alterations in protein expression related to zinc transport and mitochondrial function. Proteomic analysis revealed changes in zinc transporter family members such as Slc30a1 (6.64 log2FC), Slc30a3 (-2.32 log2FC), Slc30a4 (2.87 log2FC), Slc30a5 (5.90 log2FC), Slc30a6 (1.50 log2FC), and Slc30a7 (2.17 log2FC) in the PFC, and Slc30a3 (-1.02 log2FC), Slc30a5 (-1.04 log2FC), and Slc30a7 (1.08 log2FC) in the HP of rats subjected to ZnD. Furthermore, ZnD significantly affected essential mitochondrial activity proteins, including Atp5pb (3.25 log2FC), Cox2 (2.28 log2FC), Atp5me (2.04 log2FC), Cyc1 (2.30 log2FC), Cox4i1 (1.23 log2FC), Cox7c (1.63 log2FC), and Cisd1 (1.55 log2FC), with a pronounced decrease in complex I activity in the PFC.

CONCLUSIONS

Our study demonstrates that ZnD leads to significant proteomic changes in the PFC and HP of rats. Specifically, ZnD alters the expression of zinc transporter proteins and proteins critical for mitochondrial function. The significant decrease in complex I activity in the PFC further underscores the impact of ZnD on mitochondrial function. These results highlight the molecular mechanisms by which ZnD can influence brain function and contribute to symptoms similar to those observed in depression.

Multimodal imaging of the amygdala in non-clinical subjects with high vs. low autistic-like social skills traits

Recent clinical and theoretical frameworks suggest that social skills and theory of mind impairments characteristic of autism spectrum disorder (ASD) are distributed in the general population on a continuum between healthy individuals and patients. The present multimodal study aimed at investigating the amygdala's function, perfusion, and volume in 56 non-clinical subjects from the general population with high (n = 28 High-SOC) or low (n = 28 Low-SOC) autistic-like social skills traits. Participants underwent magnetic resonance imaging to evaluate the amygdala's functional connectivity at rest, blood perfusion by means of arterial spin labelling, its activation during a face evaluation task and lastly grey matter volumes. The High-SOC group was characterised by higher blood perfusion in both amygdalae, lower volume of the left amygdala and higher activations of the right amygdala during processing of human faces with fearful value. Resting state analyses did not reveal any significant difference between the two groups. Overall, our results highlight the presence of overlapping morpho-functional alterations of the amygdala between healthy individuals and ASD patients confirming the importance of the amygdala in this disorder and in social and emotional processing. Our findings may help disentangle the neurobiological facets of ASD elucidating aetiology and the relationship between clinical symptomatology and neurobiology.

Genetic architectures of the human hippocampus and those involved in neuropsychiatric traits

BACKGROUND

The hippocampus, with its complex subfields, is linked to numerous neuropsychiatric traits. While most research has focused on its global structure or a few specific subfields, a comprehensive analysis of hippocampal substructures and their genetic correlations across a wide range of neuropsychiatric traits remains underexplored. Given the hippocampus's high heritability, considering hippocampal and subfield volumes (HASV) as endophenotypes for neuropsychiatric conditions is essential.

METHODS

We analyzed MRI-derived volumetric data of hippocampal and subfield structures from 41,525 UK Biobank participants. Genome-wide association studies (GWAS) on 24 HASV traits were conducted, followed by genetic correlation, overlap, and Mendelian randomization (MR) analyses with 10 common neuropsychiatric traits. Polygenic risk scores (PRS) based on HASV traits were also evaluated for predicting these traits.

RESULTS

Our analysis identified 352 independent genetic variants surpassing a significance threshold of 2.1 × 10-9 within the 24 HASV traits, located across 93 chromosomal regions. Notably, the regions 12q14.3, 17q21.31, 12q24.22, 6q21, 9q33.1, 6q25.1, and 2q24.2 were found to influence multiple HASVs. Gene set analysis revealed enrichment of neural differentiation and signaling pathways, as well as protein binding and degradation. Of 240 HASV-neuropsychiatric trait pairs, 75 demonstrated significant genetic correlations (P < 0.05/240), revealing 433 pleiotropic loci. Particularly, genes like ACBD4, ARHGAP27, KANSL1, MAPT, ARL17A, and ARL17B were involved in over 50 HASV-neuropsychiatric pairs. Leveraging Mendelian randomization analysis, we further confirmed that atrophy in the left hippocampus, right hippocampus, right hippocampal body, and right CA1-3 region were associated with an increased risk of developing Parkinson's disease (PD). Furthermore, PRS for all four HASVs were significantly linked to a higher risk of Parkinson's disease (PD), with the highest hazard ratio (HR) of 1.30 (95% CI 1.18-1.43, P = 6.15 × 10⁻⁸) for right hippocampal volume.

CONCLUSIONS

These findings highlight the extensive distribution of pleiotropic genetic determinants between HASVs and neuropsychiatric traits. Moreover, they suggest a significant potential for effectively managing and intervening in these diseases during their early stages.

A circuit from lateral hypothalamic to dorsal hippocampal dentate gyrus modulates behavioral despair in mice

Behavioral despair is one of the clinical manifestations of major depressive disorder and an important cause of disability and death. However, the neural circuit mechanisms underlying behavioral despair are poorly understood. In a well-established chronic behavioral despair (CBD) mouse model, using a combination of viral tracing, in vivo fiber photometry, chemogenetic and optogenetic manipulations, in vitro electrophysiology, pharmacological profiling techniques, and behavioral tests, we investigated the neural circuit mechanisms in regulating behavioral despair. Here, we found that CBD enhanced CaMKIIα neuronal excitability in the dorsal dentate gyrus (dDG) and dDGCaMKIIα neurons involved in regulating behavioral despair in CBD mice. Besides, dDGCaMKIIα neurons received 5-HT inputs from median raphe nucleus (MRN) and were mediated by 5-HT1A receptors, whereas MRN5-HT neurons received CaMKIIα inputs from lateral hypothalamic (LH) and were mediated by AMPA receptors to regulate behavioral despair. Furthermore, fluvoxamine exerted its role in resisting behavioral despair through the LH-MRN-dDG circuit. These findings suggest that a previously unidentified circuit of LHCaMKIIα-MRN5-HT-dDGCaMKIIα mediates behavioral despair induced by CBD. Furthermore, these support the important role of AMPA receptors in MRN and 5-HT1A receptors in dDG that might be the potential targets for treatment of behavioral despair, and explain the neural circuit mechanism of fluvoxamine-resistant behavioral despair.

Chronic social defeat stress induces the down-regulation of the Nedd4L-GLT-1 ubiquitination pathway in the prefrontal cortex of mice

Stressful life events contribute to the onset of major depressive disorder (MDD). We recently demonstrated abnormalities in ubiquitination in the pathophysiology of MDD. However, the underlying molecular mechanisms remain unclear. We investigated the involvement of the ubiquitination system-mediated glutamatergic dysfunction in social impairment induced by chronic social defeat stress (CSDS). Adult C57BL/6J mice were exposed to aggressor ICR male mice for 10 consecutive days. Social impairment was induced by CSDS in the social interaction test 1 days after the last stress exposure. In terms of brain microdialysis, CSDS reduced depolarization-evoked glutamate release in the prefrontal cortex (PFC), which was reversed by a glutamate transporter 1 (GLT-1) inhibitor. Interestingly, the expression of ubiquitinated, but not total GLT-1, was decreased in the PFC of mice exposed to CSDS. The expression of neural precursor cells expressing developmentally downregulated gene 4-like (Nedd4L: E3 ligase for GLT-1), and ubiquitin-conjugating enzyme E2D2 (Ube2d2: E2 ubiquitin-conjugating enzyme for Nedd4L) was also reduced in CSDS mice. Furthermore, the downregulation of the Nedd4L-GLT-1 ubiquitination pathway decreased SIT ratio, but up-regulation increased it even in non-CSDS mice. Taken together, the decrease in GLT-1 ubiquitination may reduce the release of extracellular glutamate induced by high-potassium stimulation, which may lead to social impairment, while we could not find differences in GLT-1 ubiquitination between susceptible and resistant CSDS mice. In conclusion, GLT-1 ubiquitination could play a crucial role in the pathophysiology of MDD and is an attractive target for the development of novel antidepressants.

Differences in Children and Adolescents with Depression before and after a Remediation Program: An Event-Related Potential Study

Depression is clinically diagnosed when a defined constellation of symptoms manifests over a specific duration with notable severity. According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), Major Depressive Disorder (MDD) is characterized by the presence of five or more symptoms persisting for at least two weeks. As a profound mental health condition affecting millions globally, depression presents a considerable challenge for researchers and clinicians alike. In pediatric and adolescent populations, depression can precipitate adverse outcomes, including substance abuse, academic difficulties, risky sexual behaviors, physical health problems, impaired social relationships, and a markedly elevated risk of suicide-up to thirty times higher than the general population. This paper details a study that evaluated the efficacy of Cognitive Behavioral Therapy (CBT) alone vs. CBT combined with selective serotonin reuptake inhibitors (SSRIs) in a treatment program. The study cohort comprised sixteen (16) children and adolescents diagnosed with depression (eight males and eight females) and sixteen (16) typically developing peers (eight males and eight females) aged from 9 to 15 years (Mean age = 11.94, standard deviation = 2.02). Initial assessments employed Event-Related Potentials (ERPs), the Children's Depression Inventory (CDI), and reaction time measurements. The results reveal that participants with depression exhibit cognitive deficits in attention and memory, as evidenced by prolonged P300 latencies. Following intervention with either CBT alone or CBT combined with medication, the depressed participants demonstrated significant improvements, evidenced by lower CDI scores, reduced P300 latencies, and faster reaction times, both compared to their pre-treatment status and relative to the control group.

Myelin-associated oligodendrocytic basic protein-dependent myelin repair confers the long-lasting antidepressant effect of ketamine

Ketamine exhibits rapid and sustained antidepressant effects. As decreased myelination has been linked to depression pathology, changes in myelination may be a pivotal mechanism underlying ketamine's long-lasting antidepressant effects. Although ketamine has a long-lasting facilitating effect on myelination, the precise roles of myelination in ketamine's sustained antidepressant effects remain unknown. In this study, we employed spatial transcriptomics (ST) to examine ketamine's lasting effects in the medial prefrontal cortex (mPFC) and hippocampus of mice subjected to chronic social defeat stress and identified several differentially expressed myelin-related genes. Ketamine's ability to restore impaired myelination in the brain by promoting the differentiation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes was demonstrated. Moreover, we showed that inhibiting the expression of myelin-associated oligodendrocytic basic protein (Mobp) blocked ketamine's long-lasting antidepressant effects. We also illustrated that α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) signaling mediated ketamine's facilitation on myelination. In addition, we found that the (R)-stereoisomer of ketamine showed stronger effects on myelination than (S)-ketamine, which may explain its longer-lasting antidepressant effects. These findings reveal novel mechanisms underlying the sustained antidepressant effects of ketamine and the differences in antidepressant effects between (R)-ketamine and (S)-ketamine, providing new insights into the role of myelination in antidepressant mechanisms.

Multivariate association between psychosocial environment, behaviors, and brain functional networks in adolescent depression

BACKGROUND

Adolescent depression shows high clinical heterogeneity. Brain functional networks serve as a powerful tool for investigating neural mechanisms underlying depression profiles. A key challenge is to characterize how variation in brain functional organization links to behavioral features and psychosocial environmental influences.

METHODS

We recruited 80 adolescents with major depressive disorder (MDD) and 42 healthy controls (HCs). First, we estimated the differences in functional connectivity of resting-state networks (RSN) between the two groups. Then, we used sparse canonical correlation analysis to characterize patterns of associations between RSN connectivity and symptoms, cognition, and psychosocial environmental factors in MDD adolescents. Clustering analysis was applied to stratify patients into homogenous subtypes according to these brain-behavior-environment associations.

RESULTS

MDD adolescents showed significantly hyperconnectivity between the ventral attention and cingulo-opercular networks compared with HCs. We identified one reliable pattern of covariation between RSN connectivity and clinical/environmental features in MDD adolescents. In this pattern, psychosocial factors, especially the interpersonal and family relationships, were major contributors to variation in connectivity of salience, cingulo-opercular, ventral attention, subcortical and somatosensory-motor networks. Based on this association, we categorized patients into two subgroups which showed different environment and symptoms characteristics, and distinct connectivity alterations. These differences were covered up when the patients were taken as a whole group.

CONCLUSION

This study identified the environmental exposures associated with specific functional networks in MDD youths. Our findings emphasize the importance of the psychosocial context in assessing brain function alterations in adolescent depression and have the potential to promote targeted treatment and precise prevention.

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.

Threat experiences moderate the link between hippocampus volume and depression symptoms prospectively in adolescence

Identifying neuroimaging risk markers for depression has been an elusive goal in psychopathology research. Despite this, smaller hippocampal volume has emerged as a potential risk marker for depression, with recent research suggesting this association is moderated by family income. The current pre-registered study aimed to replicate and extend these findings by examining the moderating role of family income and three dimensions of environmental experience on the link between hippocampus volume and later depression. Data were drawn from the Adolescent Brain Cognitive Development (ABCD) study and were comprised of 6693 youth aged 9-10 years at baseline. Results indicated that psychosocial threat moderated the association between right hippocampus volume and depression symptoms two years later, such that a negative association was evident in low-threat environments (std. beta=0.15, 95% CI [0.05, 0.24]). This interaction remained significant when baseline depression symptoms were included as a covariate, though only in youth endorsing 1 or more depression symptoms at baseline (β = 0.13, 95% CI = [0.03, 0.22]). These results suggest that hippocampus volume may not be a consistent correlate of depression symptoms in high risk environments and emphasize the importance of including measures of environmental heterogeneity when seeking risk markers for depression.

Wenyang-Tianjing-Jieyu Decoction Improves Depression Rats of Kidney Yang Deficiency Pattern by Regulating T Cell Homeostasis and Inflammation Level

PURPOSE

Chronic inflammation is one of the key mechanisms of depression. Wenyang-Tianjin-Jie Decoction (WTJD) is an effective antidepressant found in the course of diagnosis and treatment, but the mechanism of therapeutic effect is not clear. The study aimed to evaluate the efficacy of WTJD in the kidney yang deficiency (KYD) type of depression rats and reveal its mechanisms.

MATERIALS AND METHODS

We selected forty 6-week-old male Sprague-Dawley rats for the study. We established a KYD [Phellodendron amurense Rupr (Huangbai) solution oral gavage and 4°C environments; 8 weeks] type of depression (chronic unpredictable mild stimulus; 6 weeks) rat model first. After successful modeling, we used WTJD or fluoxetine on rats for 3 weeks. Then we evaluated the depression and KYD behavior. Finally, we observed the expression of key inflammatory factors and proteins in peripheral blood and hippocampus, and further investigated the immune balance of Th17/Treg and Th1/Th2 cells and the activity of their main regulatory pathways JAK2/STAT3 and TLR4/TRAF6/NF-κB.

RESULTS

The imbalance of Th17/Treg and Th1/Th2 cells in rats were related to KYD and depressive symptoms. Through this study, we found that WTJD can inhibit the activity of JAK2/STAT3 and TLR4/TRAF6/NF-κB pathways, balance Th17/Treg and Th1/Th2 cell homeostasis, regulate the levels of inflammatory factors in the hippocampus and peripheral blood, and reverse KYD and depression.

CONCLUSION

This study confirmed that WTJD had a reliable effect on depression rats with KYD, and its mechanism was to regulate the immune homeostasis of hippocampal T cells and related inflammatory factors to improve KYD and depression symptoms in rats.

Emerging roles of SIRT1 activator, SRT2104, in disease treatment

Silent information regulator 1 (SIRT1) is a NAD+-dependent class III deacetylase that plays important roles in the pathogenesis of numerous diseases, positioning it as a prime candidate for therapeutic intervention. Among its modulators, SRT2104 emerges as the most specific small molecule activator of SIRT1, currently advancing into the clinical translation phase. The primary objective of this review is to evaluate the emerging roles of SRT2104, and to explore its potential as a therapeutic agent in various diseases. In the present review, we systematically summarized the findings from an extensive array of literature sources including the progress of its application in disease treatment and its potential molecular mechanisms by reviewing the literature published in databases such as PubMed, Web of Science, and the World Health Organization International Clinical Trials Registry Platform. We focuses on the strides made in employing SRT2104 for disease treatment, elucidating its potential molecular underpinnings based on preclinical and clinical research data. The findings reveal that SRT2104, as a potent SIRT1 activator, holds considerable therapeutic potential, particularly in modulating metabolic and longevity-related pathways. This review establishes SRT2104 as a leading SIRT1 activator with significant therapeutic promise.

Association of hippocampal subfield volumes with prevalence, course and incidence of depressive symptoms: The Maastricht Study

BACKGROUND

Late-life depression has been associated with volume changes of the hippocampus. However, little is known about its association with specific hippocampal subfields over time.

AIMS

We investigated whether hippocampal subfield volumes were associated with prevalence, course and incidence of depressive symptoms.

METHOD

We extracted 12 hippocampal subfield volumes per hemisphere with FreeSurfer v6.0 using T1-weighted and fluid-attenuated inversion recovery 3T magnetic resonance images. Depressive symptoms were assessed at baseline and annually over 7 years of follow-up (9-item Patient Health Questionnaire). We used negative binominal, logistic, and Cox regression analyses, corrected for multiple comparisons, and adjusted for demographic, cardiovascular and lifestyle factors.

RESULTS

A total of n = 4174 participants were included (mean age 60.0 years, s.d. = 8.6, 51.8% female). Larger right hippocampal fissure volume was associated with prevalent depressive symptoms (odds ratio (OR) = 1.26, 95% CI 1.08-1.48). Larger bilateral hippocampal fissure (OR = 1.37-1.40, 95% CI 1.14-1.71), larger right molecular layer (OR = 1.51, 95% CI 1.14-2.00) and smaller right cornu ammonis (CA)3 volumes (OR = 0.61, 95% CI 0.48-0.79) were associated with prevalent depressive symptoms with a chronic course. No associations of hippocampal subfield volumes with incident depressive symptoms were found. Yet, lower left hippocampal amygdala transition area (HATA) volume was associated with incident depressive symptoms with chronic course (hazard ratio = 0.70, 95% CI 0.55-0.89).

CONCLUSIONS

Differences in hippocampal fissure, molecular layer and CA volumes might co-occur or follow the onset of depressive symptoms, in particular with a chronic course. Smaller HATA was associated with an increased risk of incident (chronic) depression. Our results could capture a biological foundation for the development of chronic depressive symptoms, and stresses the need to discriminate subtypes of depression to unravel its biological underpinnings.

Volume of the Dentate Gyrus/CA4 Hippocampal subfield mediates the interplay between sleep quality and depressive symptoms

Background

Emerging evidence increasingly suggests that poor sleep quality is associated with depressive symptoms. The hippocampus might play a crucial role in the interplay between sleep disturbance and depressive symptomatology, e.g., hippocampal atrophy is typically seen in both insomnia disorder and depression. Thus, examining the role of hippocampal volume in the interplay between poor sleep quality and depressive symptoms in large healthy populations is vital.

Methods

We investigated the association between self-reported sleep quality, depressive symptoms, and hippocampal total and subfields' volumes in 1603 healthy young adults from the Behavioral Brain Research Project. Mediation analysis explored the mediating role of hippocampal volumes between sleep quality and depressive symptoms.

Results

Self-reported sleep quality and depressive symptoms were positively correlated. In addition, it negatively related to three hippocampal subfields but not total hippocampal volume. In particular, hippocampal subfield DG and CA4 volumes mediated the interrelationship between poor sleep quality and depressive symptoms.

Conclusions

Our findings improved the current understanding of the relationship between sleep disturbance, depressive symptomatology, and hippocampal subfields in healthy populations. Considering the crucial role of DG in hippocampal neurogenesis, our results suggest that poor sleep quality may contribute to depression through a reduction of DG volume leading to impaired neurogenesis which is crucial for the regulation of mood.

Cytoprotective effects of Hangekobokuto against corticosterone-induced cell death in HT22 cells

The hypothalamic-pituitary-adrenal (HPA) system plays an important role in stress response. Chronic stress is thought to induce neuronal damage and contribute to the pathogenesis of psychiatric disorders by causing dysfunction of the HPA system and promoting the production and release of glucocorticoids, including corticosterone and cortisol. Several clinical studies have demonstrated the efficacy of herbal medicines in treating psychiatric disorders; however, their effects on corticosterone-induced neuronal cell death remain unclear. Here, we used HT22 cells to evaluate the neuroprotective potential of herbal medicines used in neuropsychiatry against corticosterone-induced hippocampal neuronal cell death. Cell death was assessed using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) reduction and Live/Dead assays. Hangekobokuto, Kamikihito, Saikokaryukotsuboreito, Kamishoyosan, and Yokukansan were supplied in the form of water-extracted dried powders. Exposure of HT22 cells to ≥ 100 μM corticosterone decreased MTT values. Exposure to 500 μM corticosterone alone reduced MTT values to 18%, while exposure to 10 μM Mifepristone (RU486)-a glucocorticoid receptor antagonist-restored values to 36%. Corticosterone-induced cell death was partially suppressed by treatment with RU486. At 100 μg/mL, Hangekobokuto significantly suppressed the decrease in MTT values (15-32%) and increase in the percentage of ethidium homodimer-1-positive dead cells caused by corticosterone exposure (78-36%), indicating an inhibitory effect on cell death. By contrast, Kamikihito, Saikokaryukotsuboreito, Kamishoyosan, and Yokukansan did not affect corticosterone-induced cell death. Therefore, our results suggest that Hangekobokuto may ameliorate the onset and progression of psychiatric disorders by suppressing neurological disorders associated with increased levels of glucocorticoids.

Perineuronal Nets Alterations Contribute to Stress-Induced Anxiety-Like Behavior

Anxiety disorder is one of the most common mental disorders worldwide, affecting nearly 30% of adults. However, its underlying molecular mechanisms are still unclear. Here we subjected mice to chronic restraint stress (CRS), a paradigm known to induce anxiety-like behavior in mice. CRS mice exhibited anxiety-like behavior and reduced synaptic transmission in the medial prefrontal cortex (mPFC). Notably, Wisteria Floribunda agglutinin (WFA) staining showed a reduction of perineuronal nets (PNNs) expression in the mPFC of CRS mice. And the mRNA and protein levels of aggrecan (ACAN), a core component of PNNs, were also reduced. Parallelly, enzymatic digestion of PNNs in the mPFC by injecting Chondroitinase ABC (chABC) resulted in anxiety-like behavior in mice. Fluoxetine (FXT) is a clinically prescribed antidepressant/anxiolytic drug. FXT treatment in CRS mice not only ameliorated their deficits in behavior and synaptic transmissions, but also prevented CRS-induced reduction of PNNs and ACAN expressions. This study demonstrates that proper PNNs level is critical to brain functions, and their decline may serve as a pathological mechanism of anxiety disorders.

Association of retinal vessel pathology and brain atrophy in relapsing-remitting multiple sclerosis

Background

Optical coherence tomography angiography (OCTA) allows non-invasive assessment of retinal vessel structures. Thinning and loss of retinal vessels is evident in eyes of patients with multiple sclerosis (MS) and might be associated with a proinflammatory disease phenotype and worse prognosis. We investigated whether changes of the retinal vasculature are linked to brain atrophy and disability in MS.

Material and methods

This study includes one longitudinal observational cohort (n=79) of patients with relapsing-remitting MS. Patients underwent annual assessment of the expanded disability status scale (EDSS), timed 25-foot walk, symbol digit modalities test (SDMT), retinal optical coherence tomography (OCT), OCTA, and brain MRI during a follow-up duration of at least 20 months. We investigated intra-individual associations between changes in the retinal architecture, vasculature, brain atrophy and disability. Eyes with a history of optic neuritis (ON) were excluded.

Results

We included 79 patients with a median disease duration of 12 (interquartile range 2 - 49) months and a median EDSS of 1.0 (0 - 2.0). Longitudinal retinal axonal and ganglion cell loss were linked to grey matter atrophy, cortical atrophy, and volume loss of the putamen. We observed an association between vessel loss of the superficial vascular complex (SVC) and both grey and white matter atrophy. Both observations were independent of retinal ganglion cell loss. Moreover, patients with worsening of the EDSS and SDMT revealed a pronounced longitudinal rarefication of the SVC and the deep vascular complex.

Discussion

ON-independent narrowing of the retinal vasculature might be linked to brain atrophy and disability in MS. Our findings suggest that retinal OCTA might be a new tool for monitoring neurodegeneration during MS.

Aberrant intrinsic hippocampal and orbitofrontal connectivity in drug-naive adolescent patients with major depressive disorder

Alterations in resting-state functional connectivity (rsFC) of hippocampus and orbitofrontal cortex (OFC) have been highly implicated in major depressive disorder (MDD) and the researches have penetrated to the subregional level. However, relatively little is known about the intrinsic connectivity patterns of these two regions in adolescent MDD (aMDD), especially that of their functional subregions. Therefore, in the current study, we recruited 68 first-episode drug-naive aMDD patients and 43 matched typically developing controls (TDC) to characterize the alterations of whole-brain rsFC patterns in hippocampus and OFC at both regional and subregional levels in aMDD. The definition of specific functional subregions in hippocampus and OFC were based on the prior functional clustering-analysis results. Furthermore, the relationship between rsFC alterations and clinical features was also explored. Compared to TDC group, aMDD patients showed decreased connectivity of the left whole hippocampus with bilateral OFC and right inferior temporal gyrus at the regional level and increased connectivity between one of the right hippocampal subregions and right posterior insula at the subregional level. Reduced connectivity of OFC was only found in the subregion of left OFC with left anterior insula extending to lenticula in aMDD patients relative to TDC group. Our study identifies that the aberrant hippocampal and orbitofrontal rsFC was predominantly located in the insular cortex and could be summarized as an altered hippo-orbitofrontal-insular circuit in aMDD, which may be the unique features of brain network dysfunction in depression at this particular age stage. Moreover, we observed the distinct rsFC alterations in adolescent depression at the subregional level, especially the medial and lateral OFC.

Altered topology of individual brain structural covariance networks in major depressive disorder

BACKGROUND

The neurobiological pathogenesis of major depression disorder (MDD) remains largely controversial. Previous literatures with limited sample size utilizing group-level structural covariance networks (SCN) commonly generated mixed findings regarding the topology of brain networks.

METHODS

We analyzed T1 images from a high-powered multisite sample including 1173 patients with MDD and 1019 healthy controls (HCs). We used regional gray matter volume to construct individual SCN by utilizing a novel approach based on the interregional effect size difference. We further investigated MDD-related structural connectivity alterations using topological metrics.

RESULTS

Compared to HCs, the MDD patients showed a shift toward randomization characterized by increased integration. Further subgroup analysis of patients in different stages revealed this randomization pattern was also observed in patients with recurrent MDD, while the first-episode drug naïve patients exhibited decreased segregation. Altered nodal properties in several brain regions which have a key role in both emotion regulation and executive control were also found in MDD patients compared with HCs. The abnormalities in inferior temporal gyrus were not influenced by any specific site. Moreover, antidepressants increased nodal efficiency in the anterior ventromedial prefrontal cortex.

CONCLUSIONS

The MDD patients at different stages exhibit distinct patterns of randomization in their brain networks, with increased integration during illness progression. These findings provide valuable insights into the disruption in structural brain networks that occurs in patients with MDD and might be useful to guide future therapeutic interventions.

Modulation of resting-state functional connectivity in default mode network is associated with the long-term treatment outcome in major depressive disorder

BACKGROUND

Treatment non-response and recurrence are the main sources of disease burden in major depressive disorder (MDD). However, little is known about its neurobiological mechanism concerning the brain network changes accompanying pharmacotherapy. The present study investigated the changes in the intrinsic brain networks during 6-month antidepressant treatment phase associated with the treatment response and recurrence in MDD.

METHODS

Resting-state functional magnetic resonance imaging was acquired from untreated patients with MDD and healthy controls at baseline. The patients' depressive symptoms were monitored by using the Hamilton Rating Scale for Depression (HAMD). After 6 months of antidepressant treatment, patients were re-scanned and followed up every 6 months over 2 years. Traditional statistical analysis as well as machine learning approaches were conducted to investigate the longitudinal changes in macro-scale resting-state functional network connectivity (rsFNC) strength and micro-scale resting-state functional connectivity (rsFC) associated with long-term treatment outcome in MDD.

RESULTS

Repeated measures of the general linear model demonstrated a significant difference in the default mode network (DMN) rsFNC change before and after the 6-month antidepressant treatment between remitters and non-remitters. The difference in the rsFNC change over the 6-month antidepressant treatment between recurring and stable MDD was also specific to DMN. Machine learning analysis results revealed that only the DMN rsFC change successfully distinguished non-remitters from the remitters at 6 months and recurring from stable MDD during the 2-year follow-up.

CONCLUSION

Our findings demonstrated that the intrinsic DMN connectivity could be a unique and important target for treatment and recurrence prevention in MDD.

Alterations of brainstem volume in patients with first-episode and recurrent major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is a prevalent mental health condition characterized by recurrent episodes in a substantial proportion of patients. The number of previous episodes is one of the most crucial predictors of depression recurrence. However, the underlying neural mechanisms remain unclear. To date, there have been limited neuroimaging studies investigating morphological changes of the brainstem in patients with first-episode MDD (FMDD) and recurrent MDD (RMDD). This study aimed to examine volumetric changes of individual brainstem regions in relation to the number of previous episodes and disease duration.

METHOD

A total of 111 individuals including 36 FMDD, 25 RMDD, and 50 healthy controls (HCs) underwent T1-weighted structural magnetic resonance imaging scans. A Bayesian segmentation algorithm was used to analyze the volume of each brainstem region, including the medulla oblongata, pons, midbrain, and superior cerebellar peduncle (SCP), as well as the whole brainstem volume. Analyses of variance (ANOVA) were performed to obtain brain regions with significant differences among three groups and then post hoc tests were calculated for inter-group comparisons. Partial correlation analyses were further conducted to identify associations between regional volumes and clinical features.

RESULTS

The ANOVA revealed significant brainstem volumetric differences among three groups in the pons, midbrain, SCP, and the whole brainstem (F = 3.996 ~ 5.886, adjusted p = 0.015 ~ 0.028). As compared with HCs, both groups of MDD patients showed decreased volumes in the pons as well as the entire brainstem (p = 0.002 ~ 0.034), however, only the FMDD group demonstrated a significantly reduced volume in the midbrain (p = 0.003). Specifically, the RMDD group exhibited significantly decreased SCP volume when comparing to both FMDD (p = 0.021) group and HCs (p = 0.008). Correlation analyses revealed that the SCP volumes were negatively associated with the number of depressive episodes (r=-0.36, p < 0.01) and illness duration (r=-0.28, p = 0.035) in patients with MDD.

CONCLUSION

The present findings provided evidence of decreased brainstem volume involving in the pathophysiology of MDD, particularly, volumetric reduction in the SCP might represent a neurobiological marker for RMDD. Further research is needed to confirm our observations and deepen our understanding of the neural mechanisms underlying depression recurrence.

Progressive grey matter alterations in bipolar disorder across the life span - A systematic review

OBJECTIVES

To elucidate the relationship between the course of bipolar disorder (BD) and structural brain changes across the life span, we conducted a systematic review of longitudinal imaging studies in adolescent and adult BD patients.

METHODS

Eleven studies with 329 BD patients and 277 controls met our PICOS criteria (participants, intervention, comparison, outcome and study design): BD diagnosis based on DSM criteria, natural course of disease, comparison of grey matter changes in BD individuals over ≥1-year interval between scans.

RESULTS

The selected studies yielded heterogeneous findings, partly due to varying patient characteristics, data acquisition and statistical models. Mood episodes were associated with greater grey matter loss in frontal brain regions over time. Brain volume decreased or remained stable in adolescent patients, whereas it increased in healthy adolescents. Adult BD patients showed increased cortical thinning and brain structural decline. In particular, disease onset in adolescence was associated with amygdala volume reduction, which was not reported in adult BD.

CONCLUSIONS

The evidence collected suggests that the progression of BD impairs adolescent brain development and accelerates structural brain decline across the lifespan. Age-specific changes in amygdala volume in adolescent BD suggest that reduced amygdala volume is a correlate of early onset BD. Clarifying the role of BD in brain development across the lifespan promises a deeper understanding of the progression of BD patients through different developmental episodes.

Bidirectional relationships between cannabis use, anxiety and depressive symptoms in the mediation of the association with psychotic experience: further support for an affective pathway to psychosis

BACKGROUND

Empirical evidence suggests that people use cannabis to ameliorate anxiety and depressive symptoms, yet cannabis also acutely worsens psychosis and affective symptoms. However, the temporal relationship between cannabis use, anxiety and depressive symptoms and psychotic experiences (PE) in longitudinal studies is unclear. This may be informed by examination of mutually mediating roles of cannabis, anxiety and depressive symptoms in the emergence of PE.

METHODS

Data were derived from the second longitudinal Netherlands Mental Health Survey and Incidence Study. Mediation analysis was performed to examine the relationship between cannabis use, anxiety/depressive symptoms and PE, using KHB logit in STATA while adjusting for age, sex and education status.

RESULTS

Cannabis use was found to mediate the relationship between preceding anxiety, depressive symptoms and later PE incidence, but the indirect contribution of cannabis use was small (for anxiety: % of total effect attributable to cannabis use = 1.00%; for depression: % of total effect attributable to cannabis use = 1.4%). Interestingly, anxiety and depressive symptoms were found to mediate the relationship between preceding cannabis use and later PE incidence to a greater degree (% of total effect attributable to anxiety = 17%; % of total effect attributable to depression = 37%).

CONCLUSION

This first longitudinal cohort study examining the mediational relationship between cannabis use, anxiety/depressive symptoms and PE, shows that there is a bidirectional relationship between cannabis use, anxiety/depressive symptoms and PE. However, the contribution of anxiety/depressive symptoms as a mediator was greater than that of cannabis.

In vivo analyses reveal hippocampal subfield volume reductions in adolescents with schizophrenia, but not with major depressive disorder

BACKGROUND

Adult studies have reported atypicalities in the hippocampus and subfields in patients with schizophrenia (SCZ) and major depressive disorder (MDD). Both affective and psychotic disorders typically onset in adolescence, when human brain develops rapidly and shows increased susceptibility to adverse environments. However, few in vivo studies have investigated whether hippocampus subfield abnormalities occur in adolescence and whether they differ between SCZ and MDD cases.

METHODS

We recruited 150 adolescents (49 SCZ patients, 67 MDD patients, and 34 healthy controls) and obtained their structural images. We used FreeSurfer to automatically segment hippocampus into 12 subfields and analyzed subfield volumetric differences between groups by analysis of covariance, covarying for age, sex, and intracranial volume. Composite measures by summing subfield volumes were further compared across groups and analyzed in relation to clinical characteristic.

RESULTS

SCZ adolescents showed significant volume reductions in subfields of CA1, molecular layer, subiculum, parasubiculum, dentate gyrus and CA4 than healthy controls, and almost significant reductions, as compared to the MDD group, in left molecular layer, dentate gyrus, CA2/3 and CA4. Composite analyses showed smaller volumes in SCZ group than in healthy controls in all bilateral composite measures, and reduced volumes in comparison to MDD group in all left composite measures only.

CONCLUSIONS

SCZ adolescents exhibited both hippocampal subfield and composite volumes reduction, and also showed greater magnitude of deviance than those diagnosed with MDD, particularly in core CA regions. These results indicate a hippocampal disease process, suggesting a potential intervention marker of early psychotic patients and risk youths.

Apigenin attenuates depressive-like behavior via modulating monoamine oxidase A enzyme activity in chronically stressed mice

Chronic stress is a risk factor for depression and is characterized by elevated levels of brain monoamine oxidase A (MAOA). Mounting evidence has shown that MAOA is a biochemical link between stress and depression. Apigenin (API), a natural flavonoid, as demonstrated in vitro inhibitory effect on MAOA, is suggestive of antidepressant-like activity. However, the in vivo inhibitory effect of API on MAOA and how it affects depression still remain unclear. Here, we report the probable mechanisms of action of API in chronic unpredictable mild stress (CUMS)-induced depression in mice. Treatment with API reversed anhedonia, and reduced anxiety and immobility time in behavioral studies. API reduced brain corticosterone and malondialdehyde (MDA) levels but increased brain levels of glutathione and superoxide dismutase. Furthermore, interleukin-6 and tumor necrosis factor-α were attenuated by API. It also restored cell loss and inhibited the activity of MAOA in the hippocampal brain regions and prefrontal cortex. Comparative binding affinity of API for MAOA (-7.7 kcal/mol) through molecular docking studies was greater than that of reference compound, clorgyline (-6.8 kcal/mol). Favorable hydrophobic interactions important to API binding at MAOA binding cavity was revealed to include conventional hydrogen bond (Cys323 and Tyr444), π-Sulfur (Cys323), π-π Stacked (Tyr407), π-π T-shaped (Phe208), π-lone pair and π-alkyl (Ile335, Ile180) interactions. These results suggest that API is a potent, selective, reversible inhibitor of MAOA with capability of attenuating CUMS-induced depression via inhibiting MAOA enzyme activity and altering other pathomechanisms.

Reward Processing in Psychiatric Inpatients With Depression

BACKGROUND

Previous neuroimaging studies have investigated reward-processing dysfunction in major depressive disorder and have led to the common finding that major depressive disorder is associated with reduced reward responses within the reward circuit. Yet it is unclear whether such reward-processing dysfunction is specifically associated with the severity of depressive symptoms in major depressive disorder or is associated with common comorbidities.

METHODS

We investigated reward-processing differences using a classic juice-delivery functional magnetic resonance imaging experiment to compare psychiatric patients with severe depressive symptoms (DEPs) to both psychiatric control subjects (PCs) and healthy control subjects. In this study, the DEPs (n = 108) were matched to healthy control subjects (n = 62) for demographic characteristics and to the PCs (n = 108) for demographics and comorbid psychiatric diagnoses. An a priori region of interest, the left putamen, was selected using previous studies. An exploratory whole-brain analysis was performed to explore for nonhypothesized regions.

RESULTS

Relative to the PCs and healthy control subjects, the DEP group showed smaller responses to reward stimulus in the left putamen. Whole-brain exploratory analysis revealed that DEPs had significantly lower responses to reward stimulus in the bilateral dorsal striatum (putamen and caudate), middle frontal gyrus, left precentral gyrus, and middle cingulate cortex than PCs.

CONCLUSIONS

Our findings suggest that DEPs may have a lesser ability to modulate behavior as a function of reward, especially in those individuals who experience the most severe depressive symptoms. In both DEPs and PCs, the severity of depressive symptoms was related to reduced reward responses in the left putamen.

Understanding the causal relationships of attention-deficit/hyperactivity disorder with mental disorders and suicide attempt: a network Mendelian randomisation study

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is a lifespan neurodevelopmental condition resulting from complex interactions between genetic and environmental risk factors. There is evidence that ADHD is associated with other mental disorders, but it remains unclear whether and in what way a causal relationship exists.

OBJECTIVE

To investigate the direct and indirect causal paths between ADHD and seven common mental disorders.

METHODS

Two-sample network Mendelian randomisation analysis was performed to identify psychiatric disorders causally related to ADHD. Total and direct effects were estimated in an univariable and multivariable setting, respectively. Robustness of results was ensured in three ways: a range of pleiotropy-robust methods, an iterative approach identifying and excluding outliers, and use of up to two genome-wide association studies per outcome to replicate results and calculate subsequently pooled meta-estimates.

RESULTS

Genetic liability to ADHD was independently associated with the risk of anorexia nervosa (OR 1.28 (95% CI 1.11 to 1.47); p=0.001). A bidirectional association was found with major depressive disorder (OR 1.09 (95% CI 1.03 to 1.15); p=0.003 in the forward direction and OR 1.76 (95% CI 1.50 to 2.06); p=4×10-12 in the reverse direction). Moreover, after adjustment for major depression disorder, a direct association with both suicide attempt (OR 1.30 (95% CI 1.16 to 1.547); p=2×10-5) and post-traumatic stress disorder (OR 1.18 (95% CI 1.05 to 1.33); p=0.007) was observed. There was no evidence of a relationship with anxiety, bipolar disorder or schizophrenia.

CONCLUSIONS

This study suggests that ADHD is an independent risk factor for a number of common psychiatric disorders.

CLINICAL IMPLICATIONS

The risk of comorbid psychiatric disorders in individuals with ADHD needs to be considered both in diagnosis and treatment.

Transcranial magnetic stimulation of the left middle frontal gyrus modulates the information people communicate in different social contexts

Neocortical structures of the left frontal lobe, middle frontal gyrus (MFG) in particular, have been suggested to be linked to the processing of punishing and unpleasant outcomes in decision tasks. To assess the role of left MFG (lMFG) in communicative decisions, we used repetitive transcranial magnetic stimulation (rTMS) to inhibit its function during communicational exchanges under two types of social contexts: formal and informal. Three groups of participants received an offline 1-Hz inhibitory rTMS of lMFG, right MFG as an active control site, or lMFG sham/placebo TMS as a passive control condition. Participants' task included answering difficult general-knowledge questions, rating their confidence in their answers' correctness, and, finally, deciding if they would report or withhold these answers in formal and informal social contexts. There were significantly more reported than withheld answers in the informal context in all groups. The formal context showed no differences between reported and withheld answers in both control conditions, while, crucially, real rTMS of lMFG produced a different pattern, with more withheld than reported answers. Thus, lMFG inhibition seems to result in more rational decisions made only in formal communication contexts, where there is a perception of a certain pressure or possible negative outcomes. In informal social contexts and in the absence of negative consequences the pattern of answers did not change, regardless of the reporting strategy or the TMS protocol used. These results suggest selective context-dependent involvement of the lMFG in decision-making processes during communicational exchanges taking place under social pressure.

Cross-ancestry genome-wide association meta-analyses of hippocampal and subfield volumes

The hippocampus is critical for memory and cognition and neuropsychiatric disorders, and its subfields differ in architecture and function. Genome-wide association studies on hippocampal and subfield volumes are mainly conducted in European populations; however, other ancestral populations are under-represented. Here we conduct cross-ancestry genome-wide association meta-analyses in 65,791 individuals for hippocampal volume and 38,977 for subfield volumes, including 7,009 individuals of East Asian ancestry. We identify 339 variant-trait associations at P < 1.13 × 10^-9 for 44 hippocampal traits, including 23 new associations. Common genetic variants have similar effects on hippocampal traits across ancestries, although ancestry-specific associations exist. Cross-ancestry analysis improves the fine-mapping precision and the prediction performance of polygenic scores in under-represented populations. These genetic variants are enriched for Wnt signaling and neuron differentiation and affect cognition, emotion and neuropsychiatric disorders. These findings may provide insight into the genetic architectures of hippocampal and subfield volumes.

High-frequency repetitive transcranial magnetic stimulation regulates neural oscillations of the hippocampus and prefrontal cortex in mice by modulating endocannabinoid signalling

BACKGROUND

Neural oscillations play a role in the antidepressant effects of repetitive transcranial magnetic stimulation (rTMS). However, the effects of high-frequency rTMS on the neural oscillations of the medial prefrontal cortex (mPFC) and hippocampus (HPC) and its molecular mechanism have not been fully clarified.

METHODS

The depressive-like behaviours, local field potentials (LFPs) of the ventral HPC (vHPC)-mPFC, and alternations of endocannabinoid system (ECS) in the HPC and mPFC were observed after rTMS treatment. Meanwhile, depressive-like behaviours and LFPs were also observed after cannabinoid type-1 receptor (CB1R) antagonist AM281 or monoacylglycerol lipase inhibitor JZL184 injection. Moreover, the antidepressant effect of rTMS was further assessed in glutamatergic-CB1R and gamma-amino butyric acid (GABA)-ergic -CB1R knockout mice.

RESULTS

Alternations of endocannabinoids and energy value and synchronisation of mPFC-vHPC, especially the decrease of theta oscillation induced by CUMS, were alleviated by rTMS. JZL184 has similar effects to rTMS and AM281 blocked the effects of rTMS. GABAergic-CB1R deletion inhibited CUMS-induced depressive-like behaviours whereas Glutaminergic-CB1R deletion dampened the antidepressant effects of rTMS.

LIMITATIONS

The immediate effect of rTMS on field-potential regulation was not observed. Moreover, the role of region-specific regulation of the ECS in the antidepressant effect of rTMS was unclear and the effects of cell-specific CB1R knockout on neuronal oscillations of the mPFC and vHPC should be further investigated.

CONCLUSION

Endocannabinoid system mediated the antidepressant effects and was involved in the regulation of LFP in the vHPC-mPFC of high-frequency rTMS.

Neural plasticity and depression treatment

Depression is one of the most common mental disorders, which can lead to a variety of emotional problems and even suicide at its worst. As this neuropsychiatric disorder causes the patients to suffer a lot and function poorly in everyday life, it is imposing a heavy burden on the affected families and the whole society. Several hypotheses have been proposed to elucidate the pathogenesis of depression, such as the genetic mutations, the monoamine hypothesis, the hypothalamic-pituitary-adrenal (HPA) axis hyperactivation, the inflammation and the neural plasticity changes. Among these models, neural plasticity can occur at multiple levels from brain regions, cells to synapses structurally and functionally during development and in adulthood. In this review, we summarize the recent progresses (especially in the last five years) on the neural plasticity changes in depression under different organizational levels and elaborate different treatments for depression by changing the neural plasticity. We hope that this review would shed light on the etiological studies for depression and on the development of novel treatments.

Progressive brain structural abnormality in depression assessed with MR imaging by using causal network analysis

BACKGROUND

As a neuroprogressive illness, depression is accompanied by brain structural abnormality that extends to many brain regions. However, the progressive structural alteration pattern remains unknown.

METHODS

To elaborate the progressive structural alteration of depression according to illness duration, we recruited 195 never-treated first-episode patients with depression and 130 healthy controls (HCs) undergoing T1-weighted MRI scans. Voxel-based morphometry method was adopted to measure gray matter volume (GMV) for each participant. Patients were first divided into three stages according to the length of illness duration, then we explored stage-specific GMV alterations and the causal effect relationship between them using causal structural covariance network (CaSCN) analysis.

RESULTS

Overall, patients with depression presented stage-specific GMV alterations compared with HCs. Regions including the hippocampus, the thalamus and the ventral medial prefrontal cortex (vmPFC) presented GMV alteration at onset of illness. Then as the illness advanced, others regions began to present GMV alterations. These results suggested that GMV alteration originated from the hippocampus, the thalamus and vmPFC then expanded to other brain regions. The results of CaSCN analysis revealed that the hippocampus and the vmPFC corporately exerted causal effect on regions such as nucleus accumbens, the precuneus and the cerebellum. In addition, GMV alteration in the hippocampus was also potentially causally related to that in the dorsolateral frontal gyrus.

CONCLUSIONS

Consistent with the neuroprogressive hypothesis, our results reveal progressive morphological alteration originating from the vmPFC and the hippocampus and further elucidate possible details about disease progression of depression.

Microbiota and probiotics: chances and challenges - a symposium report

The 10th International Yakult Symposium was held in Milan, Italy, on 13-14 October 2022. Two keynote lectures covered the crewed journey to space and its implications for the human microbiome, and how current regulatory systems can be adapted and updated to ensure the safety of microorganisms used as probiotics or food processing ingredients. The remaining lectures were split into sections entitled "Chances" and "Challenges." The "Chances" section explored opportunities for the science of probiotics and fermented foods to contribute to diverse areas of health such as irritable bowel syndrome, major depression, Parkinson's disease, immune dysfunction, infant colic, intensive care, respiratory infections, and promoting healthy longevity. The "Challenges" section included selecting appropriate clinical trial participants and methodologies to minimise heterogeneity in responses, how to view probiotics in the context of One Health, adapting regulatory frameworks, and understanding how substances of bacterial origin can cross the blood-brain barrier. The symposium provided evidence from cutting-edge research that gut eubiosis is vital for human health and, like space, the microbiota deserves further exploration of its vast potential.

Hippocampal and amygdala volumes vary with transdiagnostic psychopathological dimensions of distress, anxious arousal, and trauma

Reduced hippocampal and/or amygdala volumes have been reported in patients with a variety of different anxiety diagnoses, suggesting that structural alterations may vary transdiagnostically across the internalizing disorders. The current study measured hippocampal and amygdala volumes in anxiety and mood disorder patients assessing differences that vary dimensionally with transdiagnostic factors of distress, anxious arousal, and trauma, based on a principal components analysis of questionnaires relating to symptomology. High-resolution structural images were collected in a sample of 165 patients, and volumes extracted from the hippocampal formation (including CA1, CA2/3, CA4/DG, subiculum, and molecular layer) and the amygdala. Transdiagnostically, increasing distress was associated with reduced hippocampal CA1 volume, increasing anxious arousal was associated with reduced hippocampal CA4/DG volume, and increasing trauma severity was associated with reduced amygdala volume in women. Taken together, the data indicate that subcortical brain volumes decrease as the severity of transdiagnostic psychopathological symptomology increases.

Dorsal Dentate Gyrus, a Key Regulator for Mood and Psychiatric Disorders

The dentate gyrus, a "gate" that controls the flow of information into the hippocampus, is critical for learning, memory, spatial navigation, and mood regulation. Several lines of evidence have demonstrated that deficits in dentate granule cells (DGCs) (e.g., loss of DGCs or genetic mutations in DGCs) contribute to the development of various psychiatric disorders, such as depression and anxiety disorders. Whereas ventral DGCs are believed to be critical for mood regulation, the functions of dorsal DGCs in this regard remain elusive. Here, we review the role of DGCs, in particular the dorsal DGCs, in the regulation of mood, their functional relationships with DGC development, and the contributions of dysfunctional DGCs to mental disorders.

Disturbed hippocampal intra-network in first-episode of drug-naïve major depressive disorder

Complex networks inside the hippocampus could provide new insights into hippocampal abnormalities in various psychiatric disorders and dementia. However, evaluating intra-networks in the hippocampus using MRI is challenging. Here, we employed a high spatial resolution of conventional structural imaging and independent component analysis to investigate intra-networks structural covariance in the hippocampus. We extracted the intra-networks based on the intrinsic connectivity of each 0.9 mm isotropic voxel to every other voxel using a data-driven approach. With a total volume of 3 cc, the hippocampus contains 4115 voxels for a 0.9 mm isotropic voxel size or 375 voxels for a 2 mm isotropic voxel of high-resolution functional or diffusion tensor imaging. Therefore, the novel method presented in the current study could evaluate the hippocampal intra-networks in detail. Furthermore, we investigated the abnormality of the intra-networks in major depressive disorders. A total of 77 patients with first-episode drug-naïve major depressive disorder and 79 healthy subjects were recruited. The independent component analysis extracted seven intra-networks from hippocampal structural images, which were divided into four bilateral networks and three networks along the longitudinal axis. A significant difference was observed in the bilateral hippocampal tail network between patients with major depressive disorder and healthy subjects. In the logistic regression analysis, two bilateral networks were significant predictors of major depressive disorder, with an accuracy of 78.1%. In conclusion, we present a novel method for evaluating intra-networks in the hippocampus. One advantage of this method is that a detailed network can be estimated using conventional structural imaging. In addition, we found novel bilateral networks in the hippocampus that were disturbed in patients with major depressive disorders, and these bilateral networks could predict major depressive disorders.

Serotonin regulation of behavior via large-scale neuromodulation of serotonin receptor networks

Although we understand how serotonin receptors function at the single-cell level, what role different serotonin receptors play in regulating brain-wide activity and, in turn, human behavior, remains unknown. Here, we developed transcriptomic-neuroimaging mapping to characterize brain-wide functional signatures associated with specific serotonin receptors: serotonin receptor networks (SRNs). Probing SRNs with optogenetics-functional magnetic resonance imaging (MRI) and pharmacology in mice, we show that activation of dorsal raphe serotonin neurons differentially modulates the amplitude and functional connectivity of different SRNs, showing that receptors' spatial distributions can confer specificity not only at the local, but also at the brain-wide, network level. In humans, using resting-state functional MRI, SRNs replicate established divisions of serotonin effects on impulsivity and negative biases. These results provide compelling evidence that heterogeneous brain-wide distributions of different serotonin receptor types may underpin behaviorally distinct modes of serotonin regulation. This suggests that serotonin neurons may regulate multiple aspects of human behavior via modulation of large-scale receptor networks.

Psychosocial factors and hippocampal subfields: The Medea-7T study

Specific subfields within the hippocampus have shown vulnerability to chronic stress, highlighting the importance of looking regionally within the hippocampus to understand the role of psychosocial factors in the development of neurodegenerative diseases. A systematic review on psychosocial factors and hippocampal subfield volumes was performed and showed inconsistent results, highlighting the need for future studies to explore this relationship. The current study aimed to explore the association of psychosocial factors with hippocampal (subfield) volumes, using high-field 7T MRI. Data were from the Memory Depression and Aging (Medea)-7T study, which included 333 participants without dementia. Hippocampal subfields were automatically segmented from T2-weighted images using ASHS software. Generalized linear models accounting for correlated outcomes were used to assess the association between subfields (i.e., entorhinal cortex, subiculum, Cornu Ammonis [CA]1, CA2, CA3, dentate gyrus, and tail) and each psychosocial factor (i.e., depressive symptoms, anxiety symptoms, childhood maltreatment, recent stressful life events, and social support), adjusted for age, sex, and intracranial volume. Neither depression nor anxiety was associated with specific hippocampal (subfield) volumes. A trend for lower total hippocampal volume was found in those reporting childhood maltreatment, and a trend for higher total hippocampal volume was found in those who experienced a recent stressful life event. Among subfields, low social support was associated with lower volume in the CA3 (B = -0.43, 95% CI: -0.72; -0.15). This study suggests possible differential effects among hippocampal (subfield) volumes and psychosocial factors.

Role of vortioxetine in the treatment of neuropathic pain

Neuropathic pain is an important and disabling clinical problem, its management constitutes a challenge for healthcare professionals. Vortioxetine is a new antidepressant drug with multimodal action, which gives it a unique profile. Tricyclic antidepressants, in particular amitriptyline, and serotonin and norepinephrine reuptake inhibitors venlafaxine and duloxetine are first-line drugs in the treatment of neuropathic pain. The interaction between the pain and depression binomial is very frequent, being the most frequent psychological complication in patients with chronic pain. This comprehensive and descriptive review summarizes the most relevant pharmacological data on vortioxetine, as well as the specific literature on vortioxetine in neuropathic pain and chronic pain.

The prevalence of psychiatric comorbidities in adult ADHD compared with non-ADHD populations: A systematic literature review

Comorbid psychiatric disorders in adults with ADHD are important because these comorbidities might complicate the diagnosis of ADHD and also worsen the prognosis. However, the prevalence of comorbid psychiatric disorders in adult ADHD varies according to the diagnostic tools used and the characteristics of target populations. The purpose of this review was to describe the prevalence of comorbid psychiatric disorders in adults with ADHD compared with adults without ADHD. Thirty-two studies published before August 2022 were identified and classified according to diagnosis of other psychiatric disorder in those with ADHD. The most frequent comorbid psychiatric disorder in the ADHD group was substance use disorder (SUD), followed by mood disorders, anxiety disorders, and personality disorders. The prevalence of these four disorders was higher in the ADHD group, whether or not subjects were diagnosed with other psychiatric disorders. In addition, the diversity of ADHD diagnostic tools was observed. This also might have affected the variability in prevalence of comorbidities. Standardization of ADHD diagnostic tools is necessary in the future.

Stress-induced myelin damage in the hippocampal formation in a rat model of depression

BACKGROUND

According to previous studies, myelin damage may be involved in the occurrence of depression. However, to date, no study has quantitatively investigated the changes in myelinated fibers and myelin sheaths in the hippocampal formation (HF) and hippocampal subfields in the context of depression.

METHODS

Male Sprague-Dawley (SD) rats (aged 4-5 weeks) were evenly divided into the control group and chronic unpredictable stress (CUS) group. Behavioral tests were performed, and then changes in myelinated fibers and myelin ultrastructure in hippocampal subfields in depression model rats were investigated using modern stereological methods and transmission electron microscopy techniques.

RESULTS

After a four-week CUS protocol, CUS rats showed depressive-like and anxiety-like behaviors. The total length and total volume of myelinated fibers were reduced in the CA1 region and DG in the CUS group compared with the control group. The total volumes of myelin sheaths and axons in the CA1 region but not in the DG were significantly lower in the CUS group than in the control group. The decrease in the total length of myelinated nerve fibers in the CA1 region in CUS rats was mainly due to a decrease in the length of myelinated fibers with a myelin sheath thickness of 0.15 μm-0.20 μm.

LIMITATIONS

The exact relationship between the degeneration of myelin sheaths and depression-like, anxiety-like behaviors needs to be further investigated.

CONCLUSIONS

CUS induces depression- and anxiety-like behaviors, and the demyelination in the CA1 region induced by 4 weeks of CUS might be an important structural basis for these behaviors.

Preschool Depression and Hippocampal Volume: The Moderating Role of Family Income

OBJECTIVE

Depression and low socioeconomic status have both been associated with hippocampal volume alterations. Whether these factors interact to predict neurobehavioral outcomes has not been adequately studied. The authors investigated family income as a moderator of the relationship between depression and hippocampal volume in a longitudinal sample.

METHOD

Longitudinal behavioral data, beginning at preschool age, and behavioral and neuroimaging data from school age to adolescence were used to assess the impact of preschool only and total preschool to adolescent depression symptoms on hippocampal volumes using family income as a moderator (N = 176).

RESULTS

Depression severity during the preschool period interacted with family income to predict hippocampal volumes at the intercept (ie, age 13 years; B = -0.078, p = .003). Interaction decomposition revealed that only individuals with relatively high family income exhibited smaller hippocampal volume with increasing depression severity (B = -0.146, p = .005). Family income was associated with hippocampus volumes only in individuals with low to moderate preschool depression severity (B = 0.289, p = .007 and B = 0.169, p = .030, respectively).

CONCLUSION

Preschool depression severity interacts with family income to predict hippocampal volume across development, such that the effects of early depression are evident only in those with higher income. These findings suggest that hippocampal volume may not be an effective marker of risk for depression at different levels of socioeconomic status, and emphasizes the importance of the environmental context when assessing risk markers for depression. Future research should explore how socioeconomic stress may eclipse the effects of depression on hippocampal development, setting alternative neurodevelopmental risk trajectories.

Alteration in NMDAR subunits in different brain regions of chronic unpredictable mild stress (CUMS) rat model

N-Methyl-d-aspartate receptor (NMDAR) signaling pathway has been implicated in the pathogenesis and treatment of depression. However, the role of NMDAR subunits in depression is still unclear. In this study, alteration in all seven NMDAR subunits in several brain areas of rats exposed to chronic unpredictable mild stress (CUMS), an animal model of depression, was detected. Our findings demonstrated that: (1) CUMS could induce a reduction in sucrose preference, an indicator of typical depression-like behaviors; (2) CUMS significantly reduced the NMDAR subunits of GluN2B and GluN3 in the medial prefrontal cortex (mPFC), but not altered all seven NMDAR subunits in hippocampus and corpus callosum of rats; (3) subunit composition of NMDARs in corpus callosum was different from that in mPFC, PFC and hippocampus; and (4) the mRNA expressions of GluN2B, GluN3A and GluN3B in mPFC as well as mRNA expression of GluN2C in corpus callosum were correlated to sucrose preference in rats. These findings suggested that GluN2B and GluN3 in mPFC may contribute to the pathophysiology of depression.

Epigenetic and Neuronal Activity Markers Suggest the Recruitment of the Prefrontal Cortex and Hippocampus in the Three-Hit Model of Depression in Male PACAP Heterozygous Mice

Depression and its increasing prevalence challenge patients, the healthcare system, and the economy. We recently created a mouse model based on the three-hit concept of depression. As genetic predisposition (first hit), we applied pituitary adenylate cyclase-activating polypeptide heterozygous mice on CD1 background. Maternal deprivation modeled the epigenetic factor (second hit), and the chronic variable mild stress was the environmental factor (third hit). Fluoxetine treatment was applied to test the predictive validity of our model. We aimed to examine the dynamics of the epigenetic marker acetyl-lysine 9 H3 histone (H3K9ac) and the neuronal activity marker FOSB in the prefrontal cortex (PFC) and hippocampus. Fluoxetine decreased H3K9ac in PFC in non-deprived animals, but a history of maternal deprivation abolished the effect of stress and SSRI treatment on H3K9ac immunoreactivity. In the hippocampus, stress decreased, while SSRI increased H3K9ac immunosignal, unlike in the deprived mice, where the opposite effect was detected. FOSB in stress was stimulated by fluoxetine in the PFC, while it was inhibited in the hippocampus. The FOSB immunoreactivity was almost completely abolished in the hippocampus of the deprived mice. This study showed that FOSB and H3K9ac were modulated in a territory-specific manner by early life adversities and later life stress interacting with the effect of fluoxetine therapy supporting the reliability of our model.

Sex-specific alterations of cortical morphometry in treatment-naïve patients with major depressive disorder

Major depressive disorder (MDD) shows sex differences in terms of incidence and symptoms, but the neurobiological basis underlying these sex differences remains to be clarified. High resolution T1-weighted Magnetic Resonance Imaging (MRI) scans were obtained from 123 non-comorbid treatment-naïve individuals with MDD and 81 age-, sex-, and handedness-matched healthy controls (HCs). MRI data were preprocessed with FreeSurfer software and four cortical measures were extracted: cortical thickness (CT), surface area (SA), cortical volume (CV), and local gyrification index (LGI). We tested for both sex-specific and sex-nonspecific patterns of cortical anatomic alterations. Regardless of sex, individuals with MDD showed significantly higher LGI in posterior cortex relative to HCs. Significant sex-by-group interactions were observed, and subsequent post-hoc analyses revealed that female individuals with MDD showed significantly lower SA in left ventrolateral prefrontal cortex (vlPFC), lower CV in right rostromedial prefrontal cortex (rmPFC), and higher LGI in left visual cortex compared with sex-matched HCs, whereas the opposite patterns of significant effects were seen in male individuals with MDD relative to their sex-matched HCs. Thus, sex-nonspecific and specific morphometric differences from HCs were found in posterior cortex, while in PFC alterations were highly sex-specific early in the illness course. This may involve sex-specific alterations in brain development or processes related to illness onset. These findings highlight the presence and regional distribution of generalized as well as sex-specific alterations of brain neurobiology in MDD.

An ecological animal model of subthreshold depression in adolescence: behavioral and resting state 18F-FDG PET imaging characterization

The different depressive disorders that exist can take root at adolescence. For instance, some functional and structural changes in several brain regions have been observed from adolescence in subjects that display either high vulnerability to depressive symptoms or subthreshold depression. For instance, adolescents with depressive disorder have been shown to exhibit hyperactivity in hippocampus, amygdala and prefrontal cortex as well as volume reductions in hippocampus and amygdala (prefrontal cortex showing more variable results). However, no animal model of adolescent subthreshold depression has been developed so far. Our objective was to design an animal model of adolescent subthreshold depression and to characterize the neural changes associated to this phenotype. For this purpose, we used adolescent Swiss mice that were evaluated on 4 tests assessing cognitive abilities (Morris water maze), anhedonia (sucrose preference), anxiety (open-field) and stress-coping strategies (forced swim test) at postnatal day (PND) 28-35. In order to identify neural alterations associated to behavioral profiles, we assessed brain resting state metabolic activity in vivo using ¹⁸F-FDG PET imaging at PND 37. We selected three profiles of mice distinguished in a composite Z-score computed from performances in the behavioral tests: High, Intermediate and Low Depressive Risk (HDR, IDR and LDR). Compared to both IDR and LDR, HDR mice were characterized by passive stress-coping behaviors, low cognition and high anhedonia and anxiety and were associated with significant changes of ¹⁸F-FDG uptakes in several cortical and subcortical areas including prelimbic cortex, infralimbic cortex, nucleus accumbens, amygdala, periaqueductal gray and superior colliculus, all displaying higher metabolic activity, while only the thalamus was associated with lower metabolic activity (compared to IDR). LDR displayed an opposing behavioral phenotype and were associated with significant changes of ¹⁸F-FDG uptakes in the dorsal striatum and thalamus that both exhibited markedly lower metabolic activity in LDR. In conclusion, our study revealed changes in metabolic activities that can represent neural signatures for behavioral profiles predicting subthreshold depression at adolescence in a mouse model.

The effects of perceived stress and anhedonic depression on mnemonic similarity task performance

Previous research has demonstrated hippocampal alterations in individuals experiencing elevated stress. The Mnemonic Similarity Task (MST) is a hippocampal-dependent task sensitive to age-related hippocampal decline, but it is unknown how performance on this task is related to one's experience of daily stress. We conducted separate discovery and replication analyses in 510 participants who completed the MST across four different Mechanical Turk studies. We hypothesized that higher scores on the Perceived Stress Scale would be associated with poorer discrimination of "lure" items from previously seen targets - a behavioral index of pattern separation - but not with recognition memory. The zero-order relationship between perceived stress and lure discrimination was not significant in the discovery or replication sample. Exploratory analyses involving anhedonic depression symptoms (from the Mood and Anxiety Symptoms Questionnaire) revealed a robust perceived stress*anhedonic depression interaction in the discovery sample that was confirmed in the replication sample. In both samples, individuals with low but not high anhedonic depression symptoms showed an inverse association between perceived stress and lure discrimination ability. Contrary to hypotheses, a similar interaction was observed for recognition memory. The novel association between perceived stress and behavioral pattern separation suggests a candidate behavioral process associated with stress-related hippocampal deficits. The specificity of this effect for individuals with low anhedonic depression symptoms - and the lack of behavioral specificity - highlight the need for additional research to unpack the clinical and neurobiological significance of these findings.