Genetic variants in major depressive disorder: From pathophysiology to therapy

Mechanism of N6-Methyladenosine Modification in the Pathogenesis of Depression

N6-methyladenosine (m6A) is one of the most common post-transcriptional RNA modifications, which plays a critical role in various bioprocesses such as immunological processes, stress response, cell self-renewal, and proliferation. The abnormal expression of m6A-related proteins may occur in the central nervous system, affecting neurogenesis, synapse formation, brain development, learning and memory, etc. Accumulating evidence is emerging that dysregulation of m6A contributes to the initiation and progression of psychiatric disorders including depression. Until now, the specific pathogenesis of depression has not been comprehensively clarified, and further investigations are warranted. Stress, inflammation, neurogenesis, and synaptic plasticity have been implicated as possible pathophysiological mechanisms underlying depression, in which m6A is extensively involved. Considering the extensive connections between depression and neurofunction and the critical role of m6A in regulating neurological function, it has been increasingly proposed that m6A may have an important role in the pathogenesis of depression; however, the results and the specific molecular mechanisms of how m6A methylation is involved in major depressive disorder (MDD) were varied and not fully understood. In this review, we describe the underlying molecular mechanisms between m6A and depression from several aspects including inflammation, stress, neuroplasticity including neurogenesis, and brain structure, which contain the interactions of m6A with cytokines, the HPA axis, BDNF, and other biological molecules or mechanisms in detail. Finally, we summarized the perspectives for the improved understanding of the pathogenesis of depression and the development of more effective treatment approaches for this disorder.

A cell-type-specific circuit of somatostatin neurons in the habenula encodes antidepressant action in male mice

Major depression is characterized by an array of negative experiences, including hopelessness and anhedonia. We hypothesize that inhibition of negative experiences or aversion may generate antidepressant action. To directly test this hypothesis, we perform multimodal behavioral screenings in male mice and identify somatostatin (SST)-expressing neurons in the region X (HBX) between the lateral and medial habenula as a specific type of antidepressant neuron. SST neuronal activity modulation dynamically regulates antidepressant induction and relief. We also explore the circuit basis for encoding these modulations using single-unit recordings. We find that SST neurons receive inhibitory synaptic inputs directly from cholecystokinin-expressing neurons in the bed nucleus of the stria terminalis and project excitatory axon terminals onto proenkephalin-expressing neurons in the interpeduncular nucleus. This study reveals a cell-type-specific circuit of SST neurons in the HBX that encodes antidepressant action, and the control of the circuit may contribute to improving well-being.

Identifying novel chemical-related susceptibility genes for five psychiatric disorders through integrating genome-wide association study and tissue-specific 3'aQTL annotation datasets

The establishment of 3'aQTLs comprehensive database provides an opportunity to help explore the functional interpretation from the genome-wide association study (GWAS) data of psychiatric disorders. In this study, we aim to search novel susceptibility genes, pathways, and related chemicals of five psychiatric disorders via GWAS and 3'aQTLs datasets. The GWAS datasets of five psychiatric disorders were collected from the open platform of Psychiatric Genomics Consortium (PGC, https://www.med.unc.edu/pgc/ ) and iPSYCH ( https://ipsych.dk/ ) (Demontis et al. in Nat Genet 51(1):63-75, 2019; Grove et al. in Nat Genet 51:431-444, 2019; Genomic Dissection of Bipolar Disorder and Schizophrenia in Cell 173: 1705-1715.e1716, 2018; Mullins et al. in Nat Genet 53: 817-829; Howard et al. in Nat Neurosci 22: 343-352, 2019). The 3'untranslated region (3'UTR) alternative polyadenylation (APA) quantitative trait loci (3'aQTLs) summary datasets of 12 brain regions were obtained from another public platform ( https://wlcb.oit.uci.edu/3aQTLatlas/ ) (Cui et al. in Nucleic Acids Res 50: D39-D45, 2022). First, we aligned the GWAS-associated SNPs of psychiatric disorders and datasets of 3'aQTLs, and then, the GWAS-associated 3'aQTLs were identified from the overlap. Second, gene ontology (GO) and pathway analysis was applied to investigate the potential biological functions of matching genes based on the methods provided by MAGMA. Finally, chemical-related gene-set analysis (GSA) was also conducted by MAGMA to explore the potential interaction of GWAS-associated 3'aQTLs and multiple chemicals in the mechanism of psychiatric disorders. A number of susceptibility genes with 3'aQTLs were found to be associated with psychiatric disorders and some of them had brain-region specificity. For schizophrenia (SCZ), HLA-A showed associated with psychiatric disorders in all 12 brain regions, such as cerebellar hemisphere (P = 1.58 × 10-36) and cortex (P = 1.58 × 10-36). GO and pathway analysis identified several associated pathways, such as Phenylpropanoid Metabolic Process (GO:0009698, P = 6.24 × 10-7 for SCZ). Chemical-related GSA detected several chemical-related gene sets associated with psychiatric disorders. For example, gene sets of Ferulic Acid (P = 6.24 × 10-7), Morin (P = 4.47 × 10-2) and Vanillic Acid (P = 6.24 × 10-7) were found to be associated with SCZ. By integrating the functional information from 3'aQTLs, we identified several susceptibility genes and associated pathways especially chemical-related gene sets for five psychiatric disorders. Our results provided new insights to understand the etiology and mechanism of psychiatric disorders.

Association between polygenic risk scores combined with clinical characteristics and antidepressant efficacy

BACKGROUND

While millions of people suffer from major depressive disorder (MDD), research has shown that individual differences in antidepressant efficacy exist, potentially attributable to various factors. Polygenic risk scores (PRSs) carry clinical potential, but associations with treatment response are seldom reported. Here, we examined whether PRSs for MDD and schizophrenia (SCZ) are associated with antidepressant effectiveness and the influence of other factors.

METHODS

A total of 999 patients were included, and the PRSs for the MDD and SCZ were calculated. The main outcome was a change in the 17-item Hamilton Depression Rating Scale (HAMD17) scores from before to after 2-week treatment. The Mann-Whitney test, Spearman correlation analysis, multiple stepwise linear regression analysis, and interaction analysis were used for statistical analysis.

RESULTS

In the 912 subjects passing quality control, a difference in the HAM-D17 score reduction rate between the MDD phenotype PRS (MDD-PRS) high-risk and the low-risk groups was discovered (P = 0.009), and a correlation was found between the MDD-PRS and the HAM-D17 score reduction rate (r = -0.075, P = 0.024). Moreover, antidepressant efficacy was related to MDD-PRS (β = -4.086, P = 0.039), the Snaith-Hamilton Pleasure Scale-total score (β = -0.009, P = 0.005), and non-first episode (β = -0.039, P < 0.001). However, the result of the interaction analysis was nonsignificant.

LIMITATIONS

The main limitation was that only 1309 targeted genes were selected based on pathways known to be involved in MDD and/or antidepressant effects.

CONCLUSION

These findings suggest a difference in antidepressant efficacy between patients in different MDD-PRS groups. Moreover, the MDD-PRS combined with clinical characteristics partially explained inter-individual differences in antidepressant efficacy.

Helicid Alleviates Neuronal Apoptosis of Rats with Depression-Like Behaviors by Downregulating lncRNA-NONRATT030918.2

Helicid (HEL) has been found to possess antidepressant pharmacological activity. The paper was to testify to the precise molecular mechanism through which HEL regulates lncRNA-NONRATT030918.2 to exert an antidepressant impression in depression models. A depression model stimulated using chronic unpredictable mild stress (CUMS) was created in rats, and the depressive state of the rats was assessed through behavioral experiments. Additionally, an in vitro model of PC12 cells induced by corticosterone (CORT) was established, and cytoactive was tested using the CCK8. The subcellular localization of the NONRATT030918.2 molecule was confirmed through a fluorescence in situ hybridization experiment. The relationship between NONRATT030918.2, miRNA-128-3p, and Prim1 was analyzed using dual-luciferase reporter gene assay, RNA Binding Protein Immunoprecipitation assay, and RNA pull-down assay. The levels of NONRATT030918.2, miRNA-128-3p, and Prim1 were tested using Q-PCR. Furthermore, the levels of Prim1, Bax, Bcl-2, and caspase3 were checked through Western blot. The HEL can alleviate the depression-like behavior of CUMS rats (P < 0.05), and reduce the mortality of hippocampal via downregulating the level of NONRATT030918.2 (P < 0.05). In CORT-induced PC12 cells, intervention with HEL led to decreased expression of NONRATT030918.2 and Prim1 (P < 0.05), as well as increased expression of miRNA-128-3p (P < 0.05). This suggests that HEL regulates the expression of NONRATT030918.2 to upregulate miRNA-128-3p (P < 0.05), which in turn inhibits CORT-induced apoptosis in PC12 cells by targeting Prim1 (P < 0.05). The NONRATT030918.2/miRNA-128-3p/Prim1 axis could potentially serve as a crucial regulatory network for HEL to exert its neuroprotective effects.

Major depressive disorder is associated with mitochondrial ND6 T14502C mutation in two Han Chinese families

BACKGROUND

Globally, the World Health Organization ranks major depressive disorder (MDD) as the leading cause of disability. However, MDD molecular etiology is still poorly understood.

AIM

To explore the possible association between mitochondrial ND6 T14502C mutation and MDD.

METHODS

Clinical data were collected from two pedigrees, and detailed mitochondrial genomes were obtained for the two proband members. The assessment of the resulting variants included an evaluation of their evolutionary conservation, allelic frequencies, as well as their structural and functional consequences. Detailed mitochondrial whole genome analysis, phylogenetic, and haplotype analysis were performed on the probands.

RESULTS

Herein, we reported the clinical, genetic, and molecular profiling of two Chinese families afflicted with MDD. These Chinese families exhibited not only a range of onset and severity ages in their depression but also extremely low penetrances to MDD. Sequence analyses of mitochondrial genomes from these pedigrees have resulted in the identification of a homoplasmic T14502C (I58V) mutation. The polymorphism is located at a highly conserved isoleucine at position 58 of ND6 and distinct mitochondrial DNA (mtDNA) polymorphisms originating from haplogroups M10 and H2.

CONCLUSION

Identifying the T14502C mutation in two individuals with no genetic relation who exhibit symptoms of depression provides compelling evidence that this mutation may be implicated in MDD development. Nonetheless, the two Chinese pedigrees that carried the T14502C mutation did not exhibit any functionally significant mutations in their mtDNA. Therefore, the phenotypic expression of the T14502C mutation related to MDD may be influenced by the nuclear modifier gene(s) or environmental factors.

The interaction between TMEM161B (rs768705) and paranoid personality traits in relation to the risk of major depressive disorder: Results form a longitudinal study of 7642 Chinese freshmen

BACKGROUND

Rs768705 (TMEM161B) is one of the identified single nucleotide polymorphisms related to major depressive disorder (MDD). Paranoid personality traits are independently associated with the risk of MDD. This study aimed to investigate the interaction effect between rs768705 (TMEM161B) and paranoid personality traits on the new-onset risk of MDD in Chinese freshmen.

METHODS

A longitudinal study was conducted among 7642 Chinese freshmen without lifetime MDD at baseline in 2018. 158 new-onset MDD cases were ascertained in 2019. DNA samples were extracted to detect the genotype of rs768705. The diagnostic and statistical manual of mental disorders-IV criteria were used to determine MDD and personality disorder traits. Multiplicative interaction was assessed by logistic regression models. Tomas Andersson's method for calculating biological interactions was used to estimate the additive interaction.

RESULTS

Rs768705(AG) (OR = 1.88, 95 % CI: 1.24-2.83) and paranoid personality traits (OR = 3.68, 95 % CI: 2.57-5.26) were significantly associated with the risk of MDD. The multiplicative interaction model with the product term of rs768705 and paranoid personality trait traits had a significant interaction effect (OR = 4.20, 95 % CI:1.62-10.91). There was also a significant additive interaction effect (RR = 7.08, 95 % CI:4.31-11.65) for the incidence of MDD. Seventy seven percent patients among new MDD cases were attributed to the additive interaction effect between rs768705 and paranoid personality traits.

CONCLUSIONS

Rs768705 (AG) may interact with paranoid personality traits to increase the incidence of MDD among Chinese college students. Schools and psychosocial health organizations should pay more attention to individuals with paranoid personality traits for MDD intervention and prevention.

New Evidence for the Role of the Blood-Brain Barrier and Inflammation in Stress-Associated Depression: A Gene-Environment Analysis Covering 19,296 Genes in 109,360 Humans

Mounting evidence supports the key role of the disrupted integrity of the blood-brain barrier (BBB) in stress- and inflammation-associated depression. We assumed that variations in genes regulating the expression and coding proteins constructing and maintaining this barrier, along with those involved in inflammation, have a predisposing or protecting role in the development of depressive symptoms after experiencing severe stress. To prove this, genome-by-environment (GxE) interaction analyses were conducted on 6.26 M SNPS covering 19,296 genes on PHQ9 depression in interaction with adult traumatic events scores in the UK Biobank (n = 109,360) in a hypothesis-free setup. Among the 63 genes that were significant in stress-connected depression, 17 were associated with BBB, 23 with inflammatory processes, and 4 with neuroticism. Compared to all genes, the enrichment of significant BBB-associated hits was 3.82, and those of inflammation-associated hits were 1.59. Besides some sex differences, CSMD1 and PTPRD, encoding proteins taking part in BBB integrity, were the most significant hits in both males and females. In conclusion, the identified risk genes and their encoded proteins could provide biomarkers or new drug targets to promote BBB integrity and thus prevent or decrease stress- and inflammation-associated depressive symptoms, and possibly infection, e.g., COVID-19-associated mental and neurological symptoms.

Epigenetic molecular underpinnings of brain structural-functional connectivity decoupling in patients with major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is progressively recognized as a stress-related disorder characterized by aberrant brain network dynamics, encompassing both structural and functional domains. Yet, the intricate interplay between these dynamic networks and their molecular underpinnings remains predominantly unexplored.

METHODS

Both structural and functional networks were constructed using multimodal neuroimaging data from 183 MDD patients and 300 age- and gender-matched healthy controls (HC). structural-functional connectivity (SC-FC) coupling was evaluated at both the connectome- and nodal-levels. Methylation data of five HPA axis key genes, including NR3C1, FKBP5, CRHBP, CRHR1, and CRHR2, were analyzed using Illumina Infinium Methylation EPIC BeadChip.

RESULTS

We observed a significant reduction in SC-FC coupling at the connectome-level in patients with MDD compared to HC. At the nodal level, we found an imbalance in SC-FC coupling, with reduced coupling in cortical regions and increased coupling in subcortical regions. Furthermore, we identified 23 differentially methylated CpG sites on the HPA axis, following adjustment for multiple comparisons and control of age, gender, and medication status. Notably, three CpG sites on NR3C1 (cg01294526, cg19457823, and cg23430507), one CpG site on FKBP5 (cg25563198), one CpG site on CRHR1 (cg26656751), and one CpG site on CRHR2 (cg18351440) exhibited significant associations with SC-FC coupling in MDD patients.

CONCLUSIONS

These findings provide valuable insights into the connection between micro-scale epigenetic changes in the HPA axis and SC-FC coupling at macro-scale connectomes. They unveil the mechanisms underlying increased susceptibility to MDD resulting from chronic stress and may suggest potential pharmacological targets within the HPA-axis for MDD treatment.

The emergence of antidepressant drugs targeting GABAA receptors: A concise review

Depression is among the most common psychiatric illnesses, which imposes a major socioeconomic burden on patients, caregivers, and the public health system. Treatment with classical antidepressants (e.g. tricyclic antidepressants and selective serotonine reuptake inhibitors), which primarily affect monoaminergic systems has several limitations, such as delayed onset of action and moderate efficacy in a relatively large proportion of depressed patients. Furthermore, depression is highly heterogeneus, and its different subtypes, including post-partum depression, involve distinct neurobiology, warranting a differential approach to pharmacotherapy. Given these shortcomings, the need for novel antidepressants that are superior in efficacy and faster in onset of action is fully justified. The development and market introduction of rapid-acting antidepressants has accelerated in recent years. Some of these new antidepressants act through the GABAergic system. In this review, we discuss the discovery, efficacy, and limitations of treatment with classic antidepressants. We provide a detailed discussion of GABAergic neurotransmission, with a special focus on GABAA receptors, and possible explanations for the mood-enhancing effects of GABAergic medications (in particular neurosteroids acting at GABAA receptors), and, ultimately, we present the most promising molecules belonging to this family which are currently used in clinical practice or are in late phases of clinical development.

Association of single nucleotide polymorphisms and gene-environment interactions with major depressive disorder in Chinese

We conducted a case-control study to investigate the effects of genetics and gene-environment interactions on major depressive disorders (MDD) in the Chinese population. Using targeted-exome sequencing, we included 984 patients with MDD and 508 healthy controls in our study. A logistic regression model was employed to analyze the association between single nucleotide polymorphisms (SNPs) and MDD. Additionally, a linear regression model was utilized to examine the associations between (1) gene-environment interaction and the 17-item Hamilton Depression Rating Scale, (2) SNPs and the Beck Scale for Suicide Ideation-Chinese version, and gene-environment interaction and the Beck scale for suicide ideation-Chinese version. The association analysis between SNPs and MDD revealed that the following loci reached genome-wide significance: rs2305554 of the cholinergic receptor nicotinic alpha 7 subunit, rs9459173 of synaptojanin 2, rs372369000 of beta-1,4-galactosyltransferase 6, rs866666526 of dopa decarboxylase, rs1254882194 of calcium/calmodulin dependent protein kinase ID, rs199880487 of reelin, rs1167948188 of reelin, rs1390140186 of QKI, KH domain containing RNA binding, and rs1776342 of period circadian regulator 3. The association analysis between SNPs and the Beck Scale for Suicide Ideation-Chinese version indicated that rs264272 and rs1774784888 of piezo type mechanosensitive ion channel component 2 reached genome-wide significance. These findings may enhance our understanding of MDD and contribute to the development of new potential targets for its diagnosis and treatment.

Efficacy of ginsenoside Rg1 on rodent models of depression: A systematic review and meta-analysis

RATIONALE

Depression is a prevalent psychiatric disease, and ginsenoside Rg1 is a bioactive compound extracted from the root of Panax ginseng C.A.Mey. To systematically investigate the effectiveness of Rg1 in rodent models of depression and provide evidence-based references for treating depression.

METHODS

Electronic searches for rodent studies were performed from inception to October 2022, e.g., PUBMED and EMBASE. Data extraction and quality evaluation were performed for the references, and meta-analysis was performed on the selected data using Review Manager 5.3.5. The outcomes were analyzed via a random-effect model and presented as mean difference (MD) with 95% confidence intervals (CIs).

RESULTS

A total of 24 studies and 678 animals were included in this meta-analysis. Rg1 remarkably improved depressive-like symptoms of depressed rodents, including the sucrose preference test (25.08, 95% CI: 20.17-30.00, Z = 10.01, P < 0.00001), forced swimming test (MD = -37.69, 95% CI: (-45.18, -30.2); Z = 9.86, P < 0.00001), and the tail suspension test (MD = -22.93, seconds, 95% CI: (-38.49, -7.37); Z = 2.89, P = 0.004).

CONCLUSIONS

The main antidepressant mechanism of Rg1 was concluded to be the neurotransmitter system, oxidant stress system, and inflammation. Conclusively, this study indicated the possible protective and therapeutic effects of Rg1 for treating depression via multiple mechanisms.

Offspring's own serotonin transporter genotype, independently from the maternal one, increases anxiety- and depression-like behavior and alters neuroplasticity markers in rats

INTRODUCTION

Developmental changes due to early life variations in the serotonin system affect stress-related behavior and neuroplasticity in adulthood. These outcomes can be caused both by offspring's own and maternal serotonergic genotype. We aimed to dissociate the contribution of the own genotype from the influences of mother genotype.

METHODS

Sixty-six male homozygous (5-HTT-/-) and heterozygous (5-HTT+/-) serotonin transporter knockout and wild-type rats from constant 5-HTT genotype mothers crossed with varying 5-HTT genotype fathers were subjected to tests assessing anxiety- and depression-like behaviors. Additionally, we measured plasma corticosterone levels and mRNA levels of BDNF, GABA system and HPA-axis components in the prelimbic and infralimbic cortex. Finally, we assessed the effect of paternal 5-HTT genotype on these measurements in 5-HTT+/- offspring receiving their knockout allele from their mother or father.

RESULTS

5-HTT-/- offspring exhibited increased anxiety- and depression-like behavior in the elevated plus maze and sucrose preference test. Furthermore, Bdnf isoform VI expression was reduced in the prelimbic cortex. Bdnf isoform IV and GABA related gene expression was also altered but did not survive false discovery rate (FDR) correction. Finally, 5-HTT+/- offspring from 5-HTT-/- fathers displayed higher levels of anxiety- and depression-like behavior and changes in GABA, BDNF and HPA-axis related gene expression not surviving FDR correction.

LIMITATIONS

Only male offspring was tested.

CONCLUSIONS

Offspring's own 5-HTT genotype influences stress-related behaviors and Bdnf isoform VI expression, independently of maternal 5-HTT genotype. Paternal 5-HTT genotype separately influenced these outcomes. These findings advance our understanding of the 5-HTT genotype dependent susceptibility to stress-related disorders.

Systematic identification of the role of gut microbiota in mental disorders: a TwinsUK cohort study

Mental disorders are complex disorders influenced by multiple genetic, environmental, and biological factors. Specific microbiota imbalances seem to affect mental health status. However, the mechanisms by which microbiota disturbances impact the presence of depression, stress, anxiety, and eating disorders remain poorly understood. Currently, there are no robust biomarkers identified. We proposed a novel pyramid-layer design to accurately identify microbial/metabolomic signatures underlying mental disorders in the TwinsUK registry. Monozygotic and dizygotic twins discordant for mental disorders were screened, in a pairwise manner, for differentially abundant bacterial genera and circulating metabolites. In addition, multivariate analyses were performed, accounting for individual-level confounders. Our pyramid-layer study design allowed us to overcome the limitations of cross-sectional study designs with significant confounder effects and resulted in an association of the abundance of genus Parabacteroides with the diagnosis of mental disorders. Future research should explore the potential role of Parabacteroides as a mediator of mental health status. Our results indicate the potential role of the microbiome as a modifier in mental disorders that might contribute to the development of novel methodologies to assess personal risk and intervention strategies.

Sex difference in the non-linear relationship between ethylene oxide exposure and depressive symptoms: A cross-sectional study

BACKGROUND

Ethylene oxide (EO) has been recognized as an animal carcinogen and environmental EO exposure was linked to several diseases. However, the association of EO exposure with depression prevalence is still not clear.

METHODS

We included 6016 participants with complete data on HbEO concentrations, depression diagnosis, and necessary covariates using the 2013-2020 National Health and Nutrition Examination Survey. Weighted multivariable logistic model was applied to examine the association of HbEO concentrations with depression risk. Weighted restricted cubic spline model was applied to draw the dose-response curve.

RESULTS

In the total population, individuals in the second, third, and fourth quartile of HbEO respectively had an adjusted OR of 0.99 (95%CI: 0.60, 1.63), 1.13 (95%CI: 0.73, 1.75), and 2.87 (95%CI: 1.86, 4.45) (Ptrend < 0.001) for depression with a significant "J" shaped non-linear dose-response relationship (Pnon-linear < 0.001). Females, drinkers, and smokers were susceptible to the depressive effect of EO. Doubling the HbEO concentrations was respectively associated with a 1.50-fold (95%CI: 1.25, 1.79), 1.29-fold (1.15, 1.44), and 1.17-fold (1.04, 1.33) increased risk of depression for females, drinkers, and smokers.

LIMITATIONS

Cross-sectional study design and self-reported depressive symptoms.

CONCLUSIONS

Environmental EO exposure was associated with increased depression risk, especially among females, drinkers, and smokers. Further prospective studies are required to affirm these findings.

A Bibliometric and Visual Analysis of Single Nucleotide Polymorphism Studies in Depression

BACKGROUND

Genetic polymorphism has been proven to have an important association with depression, which can influence the risk of developing depression, the efficacy of medications, and adverse effects via metabolic and neurological pathways. Nonetheless, aspects of the association between single nucleotide polymorphisms and depression have not been systematically investigated by bibliometric analysis.

OBJECTIVE

The aim of this study was to analyze the current status and trends of single nucleotide polymorphism research on depression through bibliometric and visual analysis.

METHODS

The Web of Science Core Collection was used to retrieve 10,043 articles that were published between 1998 and 2021. CiteSpace (6.1 R4) was used to perform collaborative network analysis, co-citation analysis, co-occurrence analysis, and citation burst detection.

RESULTS

The most productive and co-cited journals were the Journal of Affective Disorders and Biological Psychiatry, respectively, and an analysis of the references showed that the most recent research focused on the largest thematic cluster, "5-HT", reflecting the important research base in this area. "CYP2D6" has been in the spotlight since its emergence in 2009 and has become a research hotspot since its outbreak in 2019. However, "BDNF ", "COMT ", "older adults", "loci", and "DNA methylation" are also the new frontier of research, and some of them are currently in the process of exploration.

CONCLUSION

These findings offer a useful perspective on existing research and potential future approaches in the study of the association between single nucleotide polymorphisms and depression, which may assist researchers in selecting appropriate collaborators or journals.

The Role of the Adrenal-Gut-Brain Axis on Comorbid Depressive Disorder Development in Diabetes

Diabetic patients are more affected by depression than non-diabetics, and this is related to greater treatment resistance and associated with poorer outcomes. This increase in the prevalence of depression in diabetics is also related to hyperglycemia and hypercortisolism. In diabetics, the hyperactivity of the HPA axis occurs in parallel to gut dysbiosis, weakness of the intestinal permeability barrier, and high bacterial-product translocation into the bloodstream. Diabetes also induces an increase in the permeability of the blood-brain barrier (BBB) and Toll-like receptor 4 (TLR4) expression in the hippocampus. Furthermore, lipopolysaccharide (LPS)-induced depression behaviors and neuroinflammation are exacerbated in diabetic mice. In this context, we propose here that hypercortisolism, in association with gut dysbiosis, leads to an exacerbation of hippocampal neuroinflammation, glutamatergic transmission, and neuronal apoptosis, leading to the development and aggravation of depression and to resistance to treatment of this mood disorder in diabetic patients.

Identification of a diagnostic model and molecular subtypes of major depressive disorder based on endoplasmic reticulum stress-related genes

Subject

Major depressive disorder (MDD) negatively affects patients' behaviours and daily lives. Due to the high heterogeneity and complex pathological features of MDD, its diagnosis remains challenging. Evidence suggests that endoplasmic reticulum stress (ERS) is involved in the pathogenesis of MDD; however, relevant diagnostic markers have not been well studied. This study aimed to screen for ERS genes with potential diagnostic value in MDD.

Methods

Gene expression data on MDD samples were downloaded from the GEO database, and ERS-related genes were obtained from the GeneCards and MSigDB databases. Differentially expressed genes (DEGs) in MDD patients and healthy subjects were identified and then integrated with ERS genes. ERS diagnostic model and nomogram were developed based on biomarkers screened using the LASSO method. The diagnostic performance of this model was evaluated. ERS-associated subtypes were identified. CIBERSORT and GSEA were used to explore the differences between the different subtypes. Finally, WGCNA was performed to identify hub genes related to the subtypes.

Results

A diagnostic model was developed based on seven ERS genes: KCNE1, PDIA4, STAU1, TMED4, MGST1, RCN1, and SHC1. The validation analysis showed that this model had a good diagnostic performance. KCNE1 expression was positively correlated with M0 macrophages and negatively correlated with resting CD4+ memory T cells. Two subtypes (SubA and SubB) were identified, and these two subtypes showed different ER score. The SubB group showed higher immune infiltration than the SubA group. Finally, NCF4, NCF2, CSF3R, and FPR2 were identified as hub genes associated with ERS molecular subtypes.

Conclusion

Our current study provides novel diagnostic biomarkers for MDD from an ERS perspective, and these findings further facilitate the use of precision medicine in MDD.

The Role of Pharmacogenetics in Personalizing the Antidepressant and Anxiolytic Therapy

Pharmacotherapy for neuropsychiatric disorders, such as anxiety and depression, has been characterized by significant inter-individual variability in drug response and the development of side effects. Pharmacogenetics, as a key part of personalized medicine, aims to optimize therapy according to a patient's individual genetic signature by targeting genetic variations involved in pharmacokinetic or pharmacodynamic processes. Pharmacokinetic variability refers to variations in a drug's absorption, distribution, metabolism, and elimination, whereas pharmacodynamic variability results from variable interactions of an active drug with its target molecules. Pharmacogenetic research on depression and anxiety has focused on genetic polymorphisms affecting metabolizing cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT) enzymes, P-glycoprotein ATP-binding cassette (ABC) transporters, and monoamine and γ-aminobutyric acid (GABA) metabolic enzymes, transporters, and receptors. Recent pharmacogenetic studies have revealed that more efficient and safer treatments with antidepressants and anxiolytics could be achieved through genotype-guided decisions. However, because pharmacogenetics cannot explain all observed heritable variations in drug response, an emerging field of pharmacoepigenetics investigates how epigenetic mechanisms, which modify gene expression without altering the genetic code, might influence individual responses to drugs. By understanding the epi(genetic) variability of a patient's response to pharmacotherapy, clinicians could select more effective drugs while minimizing the likelihood of adverse reactions and therefore improve the quality of treatment.

Biotypes of major depressive disorder identified by a multiview clustering framework

BACKGROUND

The advances in resting-state functional magnetic resonance imaging techniques motivate parsing heterogeneity in major depressive disorder (MDD) through neurophysiological subtypes (i.e., biotypes). Based on graph theories, researchers have observed the functional organization of the human brain as a complex system with modular structures and have found wide-spread but variable MDD-related abnormality regarding the modules. The evidence implies the possibility of identifying biotypes using high-dimensional functional connectivity (FC) data in ways that suit the potentially multifaceted biotypes taxonomy.

METHODS

We proposed a multiview biotype discovery framework that involves theory-driven feature subspace partition (i.e., "view") and independent subspace clustering. Six views were defined using intra- and intermodule FC regarding three MDD focal modules (i.e., the sensory-motor system, default mode network, and subcortical network). For robust biotypes, the framework was applied to a large multisite sample (805 MDD participants and 738 healthy controls).

RESULTS

Two biotypes were stably obtained in each view, respectively characterized by significantly increased and decreased FC compared to healthy controls. These view-specific biotypes promoted the diagnosis of MDD and showed different symptom profiles. By integrating the view-specific biotypes into biotype profiles, a broad spectrum in the neural heterogeneity of MDD and its separation from symptom-based subtypes was further revealed.

LIMITATIONS

The power of clinical effects is limited and the cross-sectional nature cannot predict the treatment effects of the biotypes.

CONCLUSIONS

Our findings not only contribute to the understanding of heterogeneity in MDD, but also provide a novel subtyping framework that could transcend current diagnostic boundaries and data modality.

Association between blood manganese levels and depressive symptoms among US adults: A nationally representative cross-sectional study

BACKGROUND

Recent studies indicated that manganese (Mn) levels were inconsistently associated with the prevalence of depression. We aimed to evaluate whether blood Mn concentrations were associated with the risk of depression among US adults.

METHODS

Using the NHANES 2011-2019 datasets, we conducted a cross-sectional study in 16,572 eligible participants with complete data on blood Mn concentrations and depression diagnosis. A weighted multivariable logistic model and restricted cubic spline model were applied to explore the association and dose-response relationship of blood Mn concentrations with depression risk in the total population and subgroups.

RESULTS

In the total population, compared with the lowest reference group of blood Mn, participants in the second, third, and fourth quartile had an OR of 0.84 (95%CI: 0.66, 1.07), 0.93 (95%CI: 0.73, 1.19) and 0.91 (95%CI: 0.71, 1.15) for depression (p_trend = 0.640). In subgroup analyses, doubling of blood Mn concentrations was associated with a 0.83-fold (95%CI: 0.67, 1.02), 0.30 -fold (0.14, 0.65) decreased risk of depression in females and other ethnic groups, respectively. Significant modification effects of ethnicity on the association of blood Mn concentrations with depression risk were observed.

LIMITATIONS

cross-sectional study design and self-reported depressive symptoms.

CONCLUSIONS

Elevated blood Mn concentrations were associated with decreased depression risk in females and other specific subgroups. Mn supplementation could be a potential pathway for intervention and prevention of depression.

Does Having Rheumatoid Arthritis Increase the Dose of Depression Medications? A Mendelian Randomization Study

BACKGROUND

Rheumatoid arthritis (RA) increases the risk of depression. However, studies on the effects of RA on the dose of depression medications are limited. Therefore, in this study, we used two-sample Mendelian randomization (MR) to explore whether RA increases the dose of depression medications and gain a more comprehensive understanding of the relationship between RA and depression.

METHODS

Two-sample MR was used to evaluate the causal effect of RA on the dose of depression medications. The aggregated data on RA originated from extensive genome-wide association studies (GWASs) of European descent (14,361 cases and 42,923 controls). The summary GWAS data for the dose of depression medications were derived from the FinnGen consortium (58,842 cases and 59,827 controls). Random effects inverse-variance weighted (IVW), MR-Egger regression, weighted median, and fixed effects IVW methods were used for the MR analysis. Random effects IVW was the primary method. The heterogeneity of the MR results was detected using the IVW Cochran's Q test. The pleiotropy of the MR results was detected using MR-Egger regression and the MR pleiotropy residual sum and outlier (MR-PRESSO) test. Finally, a leave-one-out analysis was performed to determine whether the MR results were affected by a specific single-nucleotide polymorphism (SNP).

RESULTS

The primary method, random effects IVW, revealed that genetically predicted RA had a positive causal association with the dose of depression medications (Beta, 0.035; 95% confidence interval (CI), 0.007-0.064; p = 0.015). The IVW Cochran's Q test results revealed no heterogeneity in the MR analysis (p > 0.05). The MR-Egger regression and MR-PRESSO tests revealed that there was no pleiotropy in our MR analysis. The leave-one-out analysis confirmed that a single SNP did not affect the MR results, indicating the study's robustness.

CONCLUSION

Using MR techniques, we discovered that having RA increases the dose of depression medications; however, the exact mechanisms and pathways still need to be further explored.

A Review of Antidepressant Effects and Mechanisms of Three Common Herbal Medicines: Panax ginseng, Bupleurum chinense, and Gastrodia elata

OBJECTIVES

Major depressive disorder (MDD) has been reported to affect an increasing number of individuals due to the modern lifestyle. Because of its complicated mechanisms and recurrent attacks, MDD is considered a refractory chronic disease. Although the mainstream therapy for MDD is chemical drugs, they are not a panacea for MDD because of their expensiveness, associated serious adverse reactions, and endless treatment courses. Hence, we studied three kinds of herbal medicines, namely, Panax ginseng C.A. Mey (PGM), Bupleurum chinense DC (BCD), and Gastrodia elata Blume (GEB), and reviewed the mechanisms underlying their antidepressant properties to provide a reference for the development of antidepressants and clinical medications.

METHODS

An extensive range of medicinal, clinical, and chemistry databases and search engines were used for our literature search. We searched the literature using certain web literature search engines, including Google Scholar, PubMed, Science Direct, CNKI (China National Knowledge Infrastructure), and Web of Science.

RESULTS

Experimental research found that active compounds of these three medicines exhibited good antidepressant effects in vivo and in vitro. Clinical investigations revealed that single or combined treatment of these medicines improved certain depressive symptoms. Antidepressant mechanisms are summarized based on this research.

CONCLUSION

The antidepressant mechanism of these three medicines includes but is not limited to ameliorating inflammation within the brain, reversing the hypothalamic-pituitary adrenal axis (HPA) system hyperfunction, inhibiting monoamine neurotransmitters reuptake, anti-neuron apoptosis and preventing neurotoxicity, and regulating depressive-related pathways such as the BDNF pathway and the PI3K/Akt/mTOR pathway.

Targeting the Arginine Vasopressin V1b Receptor System and Stress Response in Depression and Other Neuropsychiatric Disorders

A healthy stress response is critical for good mental and overall health and promotes neuronal growth and adaptation, but the intricately balanced biological mechanisms that facilitate a stress response can also result in predisposition to disease when that equilibrium is disrupted. The hypothalamic-pituitary-adrenal (HPA) axis neuroendocrine system plays a critical role in the body's response and adaptation to stress, and vasopressinergic regulation of the HPA axis is critical to maintaining system responsiveness during chronic stress. However, exposure to repeated or excessive physical or emotional stress or trauma can shift the body's stress response equilibrium to a "new normal" underpinned by enduring changes in HPA axis function. Exposure to early life stress due to adverse childhood experiences can also lead to lasting neurobiological changes, including in HPA axis function. HPA axis impairment in patients with depression is considered among the most reliable findings in biological psychiatry, and chronic stress has been shown to play a major role in the pathogenesis and onset of depression and other neuropsychiatric disorders. Modulating HPA axis activity, for example via targeted antagonism of the vasopressin V_1b receptor, is a promising approach for patients with depression and other neuropsychiatric disorders associated with HPA axis impairment. Despite favorable preclinical indications in animal models, demonstration of clinical efficacy for the treatment of depressive disorders by targeting HPA axis dysfunction has been challenging, possibly due to the heterogeneity and syndromal nature of depressive disorders. Measures of HPA axis function, such as elevated cortisol levels, may be useful biomarkers for identifying patients who may benefit from treatments that modulate HPA axis activity. Utilizing clinical biomarkers to identify subsets of patients with impaired HPA axis function who may benefit is a promising next step in fine-tuning HPA axis activity via targeted antagonism of the V_1b receptor.

Association between Perceived Health-Related Quality of Life and Depression with Frailty in the FRASNET Study

Frailty is a major challenge facing the aging world. The phenotype of the frail subject is still far from being satisfactorily defined. We report data on mood, cognition, and quality of life (QoL) in relation to anamnestic factors, health, and socio-economic status in the FRASNET geriatric population (1204 subjects in stable health conditions), which is an observational cohort study that includes fairly balanced groups of Italian frail (421, 35%), pre-frail (449, 37.3%) and robust (334, 27.7%) subjects. A conditional inference tree analysis revealed a substantial influence of psychological variables on frailty. The physical indicator of QoL (Short Form Survey-36-Physical Component Summary, SF-36-PCS) was the predominant variable in the full model (threshold at 39.9, p < 0.001): higher frailty was found in subjects with a caregiver and lower SF-36-PCS. Frailty was also associated with the mental indicator of QoL (Short Form Survey-36-Mental Component Summary, SF-36-MCS), depression (Geriatric Depression Scale, GDS-15), leisure activities, and level of education. In support of the prominent role of inflammation in aging and mental illness, the SF-36-PCS score was correlated with the blood concentration of C-X-C motif chemokine ligand 10 (CXCL10) (r Pearson -0.355, p = 0.015), a critical signal in cell senescence and inflammaging, while the rs7567647 variant in FN1 gene encoding a glycoprotein in the extracellular matrix was significantly associated with frailty in a multivariable model (p = 0.0006). The perception of health-related QoL and subclinical depression contribute to frailty. Their assessment could improve the identification of older patients at increased risk of adverse outcomes.

Persistence of Anxiety/Depression Symptoms in Early Adolescence: A Prospective Study of Daily Life Stress, Rumination, and Daytime Sleepiness in a Genetically Informative Cohort

In this prospective study of mental health, we examine the influence of three interrelated traits - perceived stress, rumination, and daytime sleepiness - and their association with symptoms of anxiety and depression in early adolescence. Given the known associations between these traits, an important objective is to determine the extent to which they may independently predict anxiety/depression symptoms. Twin pairs from the Queensland Twin Adolescent Brain (QTAB) project were assessed on two occasions (N = 211 pairs aged 9-14 years at baseline and 152 pairs aged 10-16 years at follow-up). Linear regression models and quantitative genetic modeling were used to analyze the data. Prospectively, perceived stress, rumination, and daytime sleepiness accounted for 8-11% of the variation in later anxiety/depression; familial influences contributed strongly to these associations. However, only perceived stress significantly predicted change in anxiety/depression, accounting for 3% of variance at follow-up after adjusting for anxiety/depression at baseline, although it did not do so independently of rumination and daytime sleepiness. Bidirectional effects were found between all traits over time. These findings suggest an underlying architecture that is shared, to some degree, by all traits, while the literature points to hypothalamic-pituitary-adrenal (HPA) axis and/or circadian systems as potential sources of overlapping influence and possible avenues for intervention.

Genetic Variants Associated With Resilience in Human and Animal Studies

Resilience is broadly defined as the ability to maintain or regain functioning in the face of adversity and is influenced by both environmental and genetic factors. The identification of specific genetic factors and their biological pathways underpinning resilient functioning can help in the identification of common key factors, but heterogeneities in the operationalisation of resilience have hampered advances. We conducted a systematic review of genetic variants associated with resilience to enable the identification of general resilience mechanisms. We adopted broad inclusion criteria for the definition of resilience to capture both human and animal model studies, which use a wide range of resilience definitions and measure very different outcomes. Analyzing 158 studies, we found 71 candidate genes associated with resilience. OPRM1 (Opioid receptor mu 1), NPY (neuropeptide Y), CACNA1C (calcium voltage-gated channel subunit alpha1 C), DCC (deleted in colorectal carcinoma), and FKBP5 (FKBP prolyl isomerase 5) had both animal and human variants associated with resilience, supporting the idea of shared biological pathways. Further, for OPRM1, OXTR (oxytocin receptor), CRHR1 (corticotropin-releasing hormone receptor 1), COMT (catechol-O-methyltransferase), BDNF (brain-derived neurotrophic factor), APOE (apolipoprotein E), and SLC6A4 (solute carrier family 6 member 4), the same allele was associated with resilience across divergent resilience definitions, which suggests these genes may therefore provide a starting point for further research examining commonality in resilience pathways.

Peripheral Blood Circular RNAs as a Biomarker for Major Depressive Disorder and Prediction of Possible Pathways

Circular RNAs (circRNAs) are highly expressed in the central nervous system and have been reported to be associated with neuropsychiatric diseases, but their potential role in major depressive disorder (MDD) remains unclear. Here, we demonstrated that there was a disorder of circRNAs in the blood of MDD patients. It has been preliminarily proved that hsa_circ_0002473, hsa_circ_0079651, hsa_circ_0137187, hsa_circ_0006010, and hsa_circ_0113010 were highly expressed in MDD patients and can be used as diagnostic markers for MDD. Bioinformatics analysis revealed that hsa_circ_0079651, hsa_circ_0137187, hsa_circ_0006010, and hsa_circ_0113010 may affect the neuroplasticity of MDD through the ceRNA mechanism.

Effect of repetitive transcranial magnetic stimulation on patients with severe depression: a study protocol for systematic review and meta-analysis of randomised clinical trials

INTRODUCTION

Depression is characterised by easy recurrence, high disability and high burden, and antidepressant therapy is the standard treatment. However, its treatment effect on patients with severe depressive disorder has been unsatisfactory. Previous studies have shown that repetitive transcranial magnetic stimulation (rTMS), as a neurotherapy, can effectively mitigate the severity of depressive symptoms. Yet, more evidence is still required for TMS to treat severe depression. This study will be the first systematic review of the efficacy and tolerability of TMS for treating severe depression. We expect it to guide future clinical practice of TMS for the treatment of psychiatric disorders.

METHODS AND ANALYSIS

We will search for the randomised controlled trial (RCT) involving rTMS for treating depression in eight electronic databases, including PubMed, Web of Science, EMBASE, the Cochrane Library and Wanfang Database, from publication up to September 2021. We will define Improvement in depressive symptoms, the difference between pretreatment (baseline) and post-treatment as the primary outcomes. The difference between pretreatment and post-treatment changes in resting state fMRI will be regarded as the secondary outcomes. Quality assessment of the included articles will be independently performed according to the Cochrane Risk of Bias tool.

ETHICS AND DISSEMINATION

Ethical approval is not essential because there is no need to collect individual patient data. And this study will be published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

CRD42020211460.

Ankyrin-G Heterozygous Knockout Mice Display Increased Sensitivity to Social Defeat Stress

The ANK3 locus has been repeatedly found to confer an increased risk for bipolar disorder. ANK3 codes for Ankyrin-G (Ank-G), a scaffold protein concentrated at axon initial segments, nodes of Ranvier, and dendritic spines, where it organizes voltage-gated sodium and potassium channels and cytoskeletal proteins. Mice with homozygous conditional knockout of Ank-G in the adult forebrain display hyperactivity and reduced anxiety-like behaviors, responsive to mood stabilizers. Their behavior switches to a depression-like phenotype when exposed to chronic social defeat stress (SDS), and then spontaneously reverts to baseline hyperactivity. Ank-G heterozygous conditional knockouts (Ank-G Het cKO) have not previously been characterized. Here, we describe the behavior of Ank-G Het cKO mice compared to littermate controls in the open field, elevated plus maze, and forced swim test, under both unstressed and stressed conditions. We found that Ank-G Het cKO is not significantly different from controls at baseline or after chronic SDS. The chronic stress-induced "depression-like" behavioral phenotype is persistent for at least 28 days and is responsive to fluoxetine. Strikingly, Ank-G Het cKO mice display increased sensitivity to a short duration SDS, which does not affect controls. The heterozygous Ank-G genetic model may provide novel insights into the role of Ank-G in the pathophysiology of stress sensitivity and "depression-like" phenotypes and could be useful for studying Ank-G-related gene-environment interactions.

Association between SLC17A7 gene polymorphisms and venlafaxine for major depressive disorder in a Chinese Han population: a prospective pharmacogenetic case-control study

Objective:

Venlafaxine is a common antidepressant and its therapeutic effect varies among people with different genetic backgrounds. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) in the SLC17A7 gene are associated with the treatment outcome of venlafaxine in a Chinese Han population with major depressive disorder.

Methods:

This prospective pharmacogenetic case-control study that involved genotyping of four SNPs of SLC17A7 was conducted on 175 major depressive disorder patients of Chinese Han origin, aged 18 to 65 years, participated in the study from April 2005 to September 2006. Comparisons of allele and genotype frequencies of all SNPs were performed between the responder/remission group and the nonresponder/nonremission group. This study was approved by the Institutional Ethics Committee of Sichuan University (approval No. 20151112-265).

Results:

The allele and genotype frequencies of the four candidate SNPs in SCL17A7 showed no significant difference between responders and nonresponders. Meanwhile, no significant difference was detected in the four investigated SLC17A7 SNPs between patients who did and did not exhibit remission. Although one of the investigated SLC17A7 variants (rs1578944) demonstrated a significant association ( P =0.022) with a response to venlafaxine after 6 weeks of treatment in the survival analysis, the association was unclear after a Bonferroni multiple comparisons test was conducted.

Conclusion:

No significant association exists between the four candidate SNPs (rs1043558, rs1320301, rs1578944, and rs74174284) in SLC17A7 and venlafaxine treatment in the Chinese Han population.

Paeoniflorin: A neuroprotective monoterpenoid glycoside with promising anti-depressive properties

BACKGROUND

Depression, as a prevalent and debilitating psychiatric disease, severely decreases the life quality of individuals and brings heavy burdens to the whole society. Currently, some antidepressants are applied in the treatment of severe depressive symptoms, while there are still some undesirable drawbacks. Paeoniflorin is a monoterpenoid glycoside that was firstly extracted from Paeonia lactiflora Pall, a traditional Chinese herb that is widely used in the Chinese herbal formulas for treating depression.

PURPOSE

This review summarized the previous pre-clinical studies of paeoniflorin in treating depression and further discussed the potential anti-depressive mechanisms for that paeoniflorin to be further explored and utilized in the treatment of depression clinically.

METHODS

Some electronic databases, e.g., PubMed and China National Knowledge Infrastructure, were searched from inception until April 2021.

RESULTS

This review summarized the effective anti-depressive properties of paeoniflorin, which is related to its functions in the upregulation of the levels of monoaminergic neurotransmitters, inhibition of the hypothalamic-pituitary-adrenal axis hyperfunction, promotion of neuroprotection, promotion of hippocampus neurogenesis, and upregulation of brain-derived neurotrophic factor level, inhibition of inflammatory reaction, downregulation of nitric oxide level, etc. CONCLUSION: This review focused on the pre-clinical studies of paeoniflorin in depression and summarized the recent development of the anti-depressive mechanisms of paeoniflorin, which approves the role of paeoniflorin plays in anti-depression. However, more high-quality pre-clinical and clinical studies are expected to be conducted in the future.

Every Night and Every Morn: Effect of Variation in CLOCK Gene on Depression Depends on Exposure to Early and Recent Stress

The role of circadian dysregulation is increasingly acknowledged in the background of depressive symptoms, and is also a promising treatment target. Similarly, stress shows a complex relationship with the circadian system. The CLOCK gene, encoding a key element in circadian regulation has been implicated in previous candidate variant studies in depression with contradictory findings, and only a few such studies considered the interacting effects of stress. We investigated the effect of CLOCK variation with a linkage-disequilibrium-based clumping method, in interaction with childhood adversities and recent negative life events, on two phenotypes of depression, lifetime depression and current depressive symptoms in a general population sample. Methods: Participants in NewMood study completed questionnaires assessing childhood adversities and recent negative life events, the Brief Symptom Inventory to assess current depressive symptoms, provided data on lifetime depression, and were genotyped for 1054 SNPs in the CLOCK gene, 370 of which survived quality control and were entered into linear and logistic regression models with current depressive symptoms and lifetime depression as the outcome variable, and childhood adversities or recent life events as interaction variables followed by a linkage disequilibrium-based clumping process to identify clumps of SNPs with a significant main or interaction effect. Results: No significant clumps with a main effect were found. In interaction with recent life events a significant clump containing 94 SNPs with top SNP rs6825994 for dominant and rs6850524 for additive models on current depression was identified, while in interaction with childhood adversities on current depressive symptoms, two clumps, both containing 9 SNPs were found with top SNPs rs6828454 and rs711533. Conclusion: Our findings suggest that CLOCK contributes to depressive symptoms, but via mediating the effects of early adversities and recent stressors. Given the increasing burden on circadian rhythmicity in the modern lifestyle and our expanding insight into the contribution of circadian disruption in depression especially as a possible mediator of stress, our results may pave the way for identifying those who would be at an increased risk for depressogenic effects of circadian dysregulation in association with stress as well as new molecular targets for intervention in stress-related psychopathologies in mood disorders.

The Microbiota/Microbiome and the Gut-Brain Axis: How Much Do They Matter in Psychiatry?

The functioning of the central nervous system (CNS) is the result of the constant integration of bidirectional messages between the brain and peripheral organs, together with their connections with the environment. Despite the anatomical separation, gut microbiota, i.e., the microorganisms colonising the gastrointestinal tract, is highly related to the CNS through the so-called "gut-brain axis". The aim of this paper was to review and comment on the current literature on the role of the intestinal microbiota and the gut-brain axis in some common neuropsychiatric conditions. The recent literature indicates that the gut microbiota may affect brain functions through endocrine and metabolic pathways, antibody production and the enteric network while supporting its possible role in the onset and maintenance of several neuropsychiatric disorders, neurodevelopment and neurodegenerative disorders. Alterations in the gut microbiota composition were observed in mood disorders and autism spectrum disorders and, apparently to a lesser extent, even in obsessive-compulsive disorder (OCD) and related conditions, as well as in schizophrenia. Therefore, gut microbiota might represent an interesting field of research for a better understanding of the pathophysiology of common neuropsychiatric disorders and possibly as a target for the development of innovative treatments that some authors have already labelled "psychobiotics".

Stressful social environment and financial strain drive depressive symptoms, and reveal the effects of a FKBP5 variant and male sex, in African Americans living in Tallahassee

OBJECTIVES

The World Health Organization estimates that almost 300 million people suffer from depression worldwide. African Americans are understudied for depression-related phenotypes despite widespread racial disparities. In our study of African Americans, we integrated information on psychosocial stressors with genetic variation in order to better understand how these factors associated with depressive symptoms.

METHODS

Our research strategy combined information on financial strain and social networks with genetic data to investigate variation in symptoms of depression (CES-D scores). We collected self-report data on depressive symptoms, financial strain (difficulty paying bills) and personal social networks (a model of an individual's social environment), and we genotyped genetic variants in five genes previously implicated in depressive disorders (HTR1a, BDNF, GNB3, SLC6A4, and FKBP5) in 128 African Americans residing in Tallahassee, Florida. We tested for direct and gene-environment interactive effects of the psychosocial stressors and genetic variants on depressive symptoms.

RESULTS

Significant associations were identified between high CES-D scores and a stressful social environment (i.e., a high percentage of people in participants' social network who were a source of stress) and high financial strain. Only one genetic variant (rs1360780 in FKBP5) was significantly associated with CES-D scores and only when psychosocial stressors were included in the model; the T allele had an additive effect on depressive symptoms. Sex was also significantly associated with CES-D score in the model with psychosocial stressors and genetic variants; males had higher CES-D scores. No significant interactive effects were detected.

CONCLUSIONS

A stressful social environment and material disadvantage increase depressive symptoms in the study population. Additional associations with FKBP5 and male sex were revealed in models that included both psychosocial and genetic data. Our results suggest that incorporating psychosocial stressors may empower future genetic association studies and help clarify the biological consequences of social and financial stress.

P2RX7 gene variation mediates the effect of childhood adversity and recent stress on the severity of depressive symptoms

The P2X purinoceptor 7 (P2RX7) mediates inflammatory microglial responses and is implicated in neuroimmune mechanisms of depression and neurodegenerative disorders. A number of studies suggest that psychosocial stress may precipitate depression through immune activation. Genetic association studies of P2RX7 variants with depression have been inconclusive. However, nearly all studies have focused on only one single-nucleotide polymorphism (SNP) and have not considered interaction with psychosocial stress. We investigated the effect of several variations in P2RX7 gene using a clumping method in interaction with early adversities and recent stress on depression severity. 1752 subjects provided information on childhood adversities, recent life events, and current depression severity. Participants were genotyped for 681 SNPs in the P2RX7 gene, 335 of them passed quality control and were entered into linear regression models followed by a clumping procedure for main effect and interactions. No significant main effect was observed. Rs74892325 emerged as a top SNP for interaction with childhood adversities and rs61953400 for interaction with recent life events. Our study is the first to investigate several variants in the P2RX7 gene and in interaction with two types of stress, extending our understanding of neuroinflammation in depression, and supporting that the majority of genes influence depression by enhancing sensitivity to stressors.

Losing DNA methylation at repetitive elements and breaking bad

Background

DNA methylation is an epigenetic chromatin mark that allows heterochromatin formation and gene silencing. It has a fundamental role in preserving genome stability (including chromosome stability) by controlling both gene expression and chromatin structure. Therefore, the onset of an incorrect pattern of DNA methylation is potentially dangerous for the cells. This is particularly important with respect to repetitive elements, which constitute the third of the human genome.

Main body

Repetitive sequences are involved in several cell processes, however, due to their intrinsic nature, they can be a source of genome instability. Thus, most repetitive elements are usually methylated to maintain a heterochromatic, repressed state. Notably, there is increasing evidence showing that repetitive elements (satellites, long interspersed nuclear elements (LINEs), Alus) are frequently hypomethylated in various of human pathologies, from cancer to psychiatric disorders. Repetitive sequences’ hypomethylation correlates with chromatin relaxation and unscheduled transcription. If these alterations are directly involved in human diseases aetiology and how, is still under investigation.

Conclusions

Hypomethylation of different families of repetitive sequences is recurrent in many different human diseases, suggesting that the methylation status of these elements can be involved in preservation of human health. This provides a promising point of view towards the research of therapeutic strategies focused on specifically tuning DNA methylation of DNA repeats.

Genetic underpinnings of affective temperaments: a pilot GWAS investigation identifies a new genome-wide significant SNP for anxious temperament in ADGRB3 gene

Although recently a large-sample GWASs identified significant loci in the background of depression, the heterogeneity of the depressive phenotype and the lack of accurate phenotyping hinders applicability of findings. We carried out a pilot GWAS with in-depth phenotyping of affective temperaments, considered as subclinical manifestations and high-risk states for affective disorders, in a general population sample of European origin. Affective temperaments were measured by TEMPS-A. SNP-level association was assessed by linear regression models, assuming an additive genetic effect, using PLINK1.9. Gender, age, the first ten principal components (PCs) and the other four temperaments were included in the regression models as covariates. SNP-level relevances (p-values) were aggregated to gene level using the PEGASUS method¹. In SNP-based tests, a Bonferroni-corrected significance threshold of p ≤ 5.0 × 10^-8 and a suggestive significance threshold of p ≤ 1.0 × 10^-5, whereas in gene-based tests a Bonferroni-corrected significance of 2.0 × 10^-6 and a suggestive significance of p ≤ 4.0 × 10^-4 was established. To explore known functional effects of the most significant SNPs, FUMA v1.3.5 was used. We identified 1 significant and 21 suggestively significant SNPs in ADGRB3, expressed in the brain, for anxious temperament. Several other brain-relevant SNPs and genes emerged at suggestive significance for the other temperaments. Functional analyses reflecting effect on gene expression and participation in chromatin interactions also pointed to several genes expressed in the brain with potentially relevant phenotypes regulated by our top SNPs. Our findings need to be tested in larger GWA studies and candidate gene analyses in well-phenotyped samples in relation to affective disorders and related phenotypes.

Oligonucleotides as therapeutic tools for brain disorders: Focus on major depressive disorder and Parkinson's disease

Remarkable advances in understanding the role of RNA in health and disease have expanded considerably in the last decade. RNA is becoming an increasingly important target for therapeutic intervention; therefore, it is critical to develop strategies for therapeutic modulation of RNA function. Oligonucleotides, including antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA mimic (miRNA), and anti-microRNA (antagomir) are perhaps the most direct therapeutic strategies for addressing RNA. Among other mechanisms, most oligonucleotide designs involve the formation of a hybrid with RNA that promotes its degradation by activation of endogenous enzymes such as RNase-H (e.g., ASO) or the RISC complex (e.g. RNA interference - RNAi for siRNA and miRNA). However, the use of oligonucleotides for the treatment of brain disorders is seriously compromised by two main limitations: i) how to deliver oligonucleotides to the brain compartment, avoiding the action of peripheral RNAses? and once there, ii) how to target specific neuronal populations? We review the main molecular pathways in major depressive disorder (MDD) and Parkinson's disease (PD), and discuss the challenges associated with the development of novel oligonucleotide therapeutics. We pay special attention to the use of conjugated ligand-oligonucleotide approach in which the oligonucleotide sequence is covalently bound to monoamine transporter inhibitors (e.g. sertraline, reboxetine, indatraline). This strategy allows their selective accumulation in the monoamine neurons of mice and monkeys after their intranasal or intracerebroventricular administration, evoking preclinical changes predictive of a clinical therapeutic action after knocking-down disease-related genes. In addition, recent advances in oligonucleotide therapeutic clinical trials are also reviewed.

Targeting the dysfunction of glutamate receptors for the development of novel antidepressants

Increasing evidence indicates that dysfunction of glutamate receptors is involved in the pathophysiology of major depressive disorder (MDD). Although accumulating efforts have been made to elucidate the applications and mechanisms underlying antidepressant-like effects of ketamine, a non-selective antagonist of N-methyl-d-aspartate receptor (NMDAR), the role of specific glutamate receptor subunit in regulating depression is not completely clear. The current review aims to discuss the relationships between glutamate receptor subunits and depressive-like behaviors. Research literatures were searched from inception to July 2020. We summarized the alterations of glutamate receptor subunits in patients with MDD and animal models of depression. Animal behaviors in response to dysfunction of glutamate receptor subunits were also surveyed. To fully understand mechanisms underlying antidepressant-like effects of modulators targeting glutamate receptors, we discussed effects of each glutamate receptor subunit on serotonin system, synaptic plasticity, neurogenesis and neuroinflammation. Finally, we collected most recent clinical applications of glutamate receptor modulators and pointed out the limitations of these candidates in the treatment of MDD.

Pathophysiological Bases of Comorbidity in Migraine

Despite that it is commonly accepted that migraine is a disorder of the nervous system with a prominent genetic basis, it is comorbid with a plethora of medical conditions. Several studies have found bidirectional comorbidity between migraine and different disorders including neurological, psychiatric, cardio- and cerebrovascular, gastrointestinal, metaboloendocrine, and immunological conditions. Each of these has its own genetic load and shares some common characteristics with migraine. The bidirectional mechanisms that are likely to underlie this extensive comorbidity between migraine and other diseases are manifold. Comorbid pathologies can induce and promote thalamocortical network dysexcitability, multi-organ transient or persistent pro-inflammatory state, and disproportionate energetic needs in a variable combination, which in turn may be causative mechanisms of the activation of an ample defensive system with includes the trigeminovascular system in conjunction with the neuroendocrine hypothalamic system. This strategy is designed to maintain brain homeostasis by regulating homeostatic needs, such as normal subcortico-cortical excitability, energy balance, osmoregulation, and emotional response. In this light, the treatment of migraine should always involves a multidisciplinary approach, aimed at identifying and, if necessary, eliminating possible risk and comorbidity factors.

Basolateral Amygdala Serotonin 2C Receptor Regulates Emotional Disorder-Related Symptoms Induced by Chronic Methamphetamine Administration

Globally, methamphetamine (MA) is the second most abused drug, with psychotic symptoms being one of the most common adverse effects. Emotional disorders induced by MA abuse have been widely reported both in human and animal models; however, the mechanisms underlying such disorders have not yet been fully elucidated. In this study, a chronic MA administration mouse model was utilized to elucidate the serotonergic pathway involved in MA-induced emotional disorders. After 4 weeks of MA administration, the animals exhibited significantly increased depressive and anxious symptoms. Molecular and morphological evidence showed that chronic MA administration reduced the expression of the 5-hydroxytryptamine (5-HT) rate-limiting enzyme, tryptophan hydroxylase 2, in the dorsal raphe and the concentrations of 5-HT and its metabolite 5-hydroxyindoleacetic acid in the basolateral amygdala (BLA) nuclei. Alterations in both 5-HT and 5-HT receptor levels occurred simultaneously in BLA; quantitative polymerase chain reaction, western blotting, and fluorescence analysis revealed that the expression of the 5-HT2C receptor (5-HT_2CR) increased. Neuropharmacology and virus-mediated silencing strategies confirmed that targeting 5-HT_2CR reversed the depressive and anxious behaviors induced by chronic MA administration. In the BLA, 5-HT_2CR-positive cells co-localized with GABAergic interneurons. The inactivation of 5-HT_2CR ameliorated impaired GABAergic inhibition and decreased BLA activation. Thus, herein, for the first time, we report that the abnormal regulation of 5-HT_2CR is involved in the manifestation of emotional disorder-like symptoms induced by chronic MA use. Our study suggests that 5-HT_2CR in the BLA is a promising clinical target for the treatment of MA-induced emotional disorders.

Inflamed Mind: Multiple Genetic Variants of IL6 Influence Suicide Risk Phenotypes in Interaction With Early and Recent Adversities in a Linkage Disequilibrium-Based Clumping Analysis

Background: Understanding and predicting suicide remains a challenge, and a recent paradigm shift regarding the complex relationship between the immune system and the brain brought attention to the involvement of inflammation in neuropsychiatric conditions including suicide. Among cytokines, IL-6 has been most frequently implicated in suicide, yet only a few candidate gene studies and without considering the effect of stress investigated the role of IL6 in suicidal behaviour. Our study aimed to investigate the association of IL6 variation with a linkage disequilibrium-based clumping method in interaction with childhood adversities and recent stress on manifestations along the suicide spectrum. Methods: One thousand seven hundred and sixty-two participants provided information on previous suicide attempts, current suicidal ideation, thoughts of death, and hopelessness, and were genotyped for 186 variants in IL6. Early childhood adversities were recorded with an instrument adapted from the Childhood Trauma Questionnaire, recent life events were registered using the List of Threatening Life Events. Following a 3-step quality control, logistic and linear regression models were run to explore the effect of genotype and gene-environment interactions on suicide phenotypes. All regression models were followed by a clumping process based on empirical estimates of linkage disequilibrium between clumps of intercorrelated SNPs. Interaction effects of distinct types of recent life events were also analysed. Results: No clumps with significant main effects emerged, but we identified several clumps significantly interacting with childhood adversities on lifetime suicide attempts, current suicidal ideation, and current thoughts of death. We also identified clumps significantly interacting with recent negative life events on current suicidal ideation. We reported no clumps with significant effect on hopelessness either as a main effect or in interaction with childhood adversities or recent stress. Conclusion: We identified variant clumps in IL6 influencing suicidal behaviour, but only in interaction with childhood or recent adversities. Our results may bring us a step further in understanding the role of neuroinflammation and specifically of IL-6 in suicide, towards identifying novel biological markers of suicidal behaviour especially in those exposed to stressful experiences, and to fostering the adaptation of a new paradigm and identifying novel approaches and targets in the treatment of suicidal behaviour.

Biotypes of major depressive disorder: Neuroimaging evidence from resting-state default mode network patterns

BACKGROUND

Major depressive disorder (MDD) is heterogeneous disorder associated with aberrant functional connectivity within the default mode network (DMN). This study focused on data-driven identification and validation of potential DMN-pattern-based MDD subtypes to parse heterogeneity of the disorder.

METHODS

The sample comprised 1397 participants including 690 patients with MDD and 707 healthy controls (HC) registered from multiple sites based on the REST-meta-MDD Project in China. Baseline resting-state functional magnetic resonance imaging (rs-fMRI) data was recorded for each participant. Discriminative features were selected from DMN between patients and HC. Patient subgroups were defined by K-means and principle component analysis in the multi-site datasets and validated in an independent single-site dataset. Statistical significance of resultant clustering were confirmed. Demographic and clinical variables were compared between identified patient subgroups.

RESULTS

Two MDD subgroups with differing functional connectivity profiles of DMN were identified in the multi-site datasets, and relatively stable in different validation samples. The predominant dysfunctional connectivity profiles were detected among superior frontal cortex, ventral medial prefrontal cortex, posterior cingulate cortex and precuneus, whereas one subgroup exhibited increases of connectivity (hyperDMN MDD) and another subgroup showed decreases of connectivity (hypoDMN MDD). The hyperDMN subgroup in the discovery dataset had age-related severity of depressive symptoms. Patient subgroups had comparable demographic and clinical symptom variables.

CONCLUSIONS

Findings suggest the existence of two neural subtypes of MDD associated with different dysfunctional DMN connectivity patterns, which may provide useful evidence for parsing heterogeneity of depression and be valuable to inform the search for personalized treatment strategies.

"Influence of diet on mood and social cognition: a pilot study"

Recently, a relationship has been observed between nutrition and social cognition. In this aspect, several dietary patterns, or even some probiotics, have been reported as social cognition modulators. However, to date, no studies have reported the effects of specific nutrients. Our aim was to evaluate the relationship between dietary macronutrients and the processing of social and affective information. Participants were undergraduates from the University of Extremadura (Badajoz, Spain) aged 21.3 ± 2.9 years., with a BMI of 22.8 ± 3.9 (kg m-2). The students' social cognition and diet were analysed through questionnaires and a dietary record. The diets were analysed with DIAL v.1.18® software (Alce Ingeniería®). The participants filled out the WHO-5 well-being index, Beck's anxiety inventory, Beck's depression inventory, ruminative response scale (RSS), Leiden index of depression sensitivity (LEIDS-r), empathy quotient (EQ), and interpersonal reactivity index (IRI). To analyse the data, nutrients were grouped through principal component analysis (PCA) into lipids, carbohydrates and proteins. Additionally, we assayed if these principal components were associated with psychological questionnaire scores using multiple linear regression analyses. The dietary pattern differed from the traditional Mediterranean diet due to high intake of proteins and saturated fatty acids. Regarding social cognition and macronutrients, we found a positive association between lipids, specifically cholesterol, and the Perspective-Taking Scale (an IRI component). Carbohydrates influenced the RSS, indicating that complex carbohydrates may be a risk factor for depression. Moreover, the brooding factor, a component of the RRS, was negatively affected by dietary carbohydrates and proteins, specifically by fiber and aspartate. Diet may influence several variables related to social cognition and mood. Particularly, a low-cholesterol diet rich in fiber, complex carbohydrates, and aspartate apparently provides benefits, improving the processing of social and affective information and psychic well-being.

Can I Get a Witness? Using Vicarious Defeat Stress to Study Mood-Related Illnesses in Traditionally Understudied Populations

The chronic social defeat stress model has been instrumental in shaping our understanding of neurobiology relevant to affect-related illnesses, including major depressive disorder. However, the classic chronic social defeat stress procedure is limited by its exclusive application to adult male rodents. We have recently developed a novel vicarious social defeat stress procedure wherein one mouse witnesses the physical defeat bout of a conspecific from the safety of an adjacent compartment. This witness mouse develops a similar behavioral phenotype to that of the mouse that physically experiences social defeat stress, modeling multiple aspects of major depressive disorder. Importantly, this new procedure allows researchers to perform vicarious social defeat stress in males or females and in juvenile mice, which typically are excluded from classic social defeat experiments. Here we discuss several recent advances made using this procedure and how its application provides a new preclinical approach to study the neurobiology of psychological stress-induced phenotypes.

Nature and Nurture: Effects of Affective Temperaments on Depressive Symptoms Are Markedly Modified by Stress Exposure

BACKGROUND

Lack of proper consideration of the interaction between biological and environmental factors limits our understanding of the development of depression. Our cross-sectional study investigated whether recent stress influences the effect of affective temperaments on depressive symptoms.

METHODS

1015 general population participants completed the Brief Symptom Inventory to capture depressive symptoms, the List of Threatening Experiences Questionnaire to assess recent stressors, and the Temperament Evaluation of Memphis Pisa, Paris, and San Diego Autoquestionnaire to evaluate affective temperaments (TEMPS-A). Linear regression models were built to investigate the effect of temperament and stress on depression, temperament on stress, and the effect of temperament on depressive symptoms in different stress exposure groups.

RESULTS

Recent life events and anxious, depressive, cyclothymic, and hyperthymic temperaments significantly predicted depressive symptoms, and cyclothymic, and hyperthymic temperaments significantly predicted recent life event exposure. While in case of mild stress all affective temperaments except irritable predicted depression, in case of moderate exposure only the effect of depressive, cyclothymic, and hyperthymic temperament, while in the high exposure group only the effect of anxious temperament was significant.

LIMITATIONS

All measures were based on self-report, and subjective impact of life events was not considered. This was a cross-sectional study with a correlational nature which does not allow for causative conclusions.

CONCLUSIONS

The contribution of affective temperaments to depression is much higher compared to stress, and severity of exposure to life events influences the impact of affective temperaments on depressive symptoms, pointing to divergent pathways of emotional reactivity mediating the effects of stress on depression which can be exploited for prevention and treatment.

Plasma levels of nesfatin-1 as a new biomarker in depression in Asians: evidence from meta-analysis

Objective: This study aims to review the alteration of plasma nesfatin-1 levels in patients with depression.Methods: Under the guidance of the latest PRISMA checklist, a systematic review and meta-analysis were conducted by searching English database (PubMed, Web of Science, EMDASE) and Chinese database for relevant studies up to August, 2019. Pooled standardised mean difference (SMD) with 95% confidence intervals (CI) was calculated with the random effects model.Results: Nine studies that reported the association between plasma levels of nesfatin-1 and the risk of depression with 567 patients and 447 control participants were included in the meta-analysis. Compared with the healthy controls, depressive patients had a higher plasma level of nesfatin-1 [SMD (95% CI):1.58(0.75, 2.41), Z = 3.74, p for Z < 0.001; I² = 96.8%, p for I² < 0.001]. The subgroup analyses and meta-regression failed to find the source of the heterogeneity. No evidence of publication bias was found either in Begg's test (p = 0.348) or the Egger's test (p = 0.523).Conclusion: The present meta-analysis indicated that a higher plasma level of nesfatin-1 was associated with an increased risk of depression.

Targeted exome sequencing identifies five novel loci at genome-wide significance for modulating antidepressant response in patients with major depressive disorder

In order to determine the role of single nucleotide variants (SNVs) in modulating antidepressant response, we conducted a study, consisting of 929 major depressive disorder (MDD) patients, who were treated with antidepressant drugs (drug-only) or in combination with a repetitive transcranial magnetic stimulation (plus-rTMS), followed by targeted exome sequencing analysis. We found that the "plus-rTMS" patients presented a more effective response to the treatment when compared to the 'drug-only' group. Our data firstly demonstrated that the SNV burden had a significant impact on the antidepressant response presented in the "drug-only" group, but was limited in the "plus-rTMS" group. Further, after controlling for overall SNV burden, seven single nucleotide polymorphisms (SNPs) at five loci, IL1A, GNA15, PPP2CB, PLA2G4C, and GBA, were identified as affecting the antidepressant response at genome-wide significance (P < 5 × 10^-08). Additional multiple variants achieved a level of correction for multiple testing, including GNA11, also shown as a strong signal for MDD risk. Our study showed some promising evidence on genetic variants that could be used as individualized therapeutic guides for MDD patients.