Comparison of plasma MicroRNA levels in drug naive, first episode depressed patients and healthy controls

Identifying the differentially expressed peripheral blood microRNAs in psychiatric disorders: a systematic review and meta-analysis

Background

Evidence has suggested that microRNAs (miRNAs) may play an important role in the pathogenesis of psychiatric disorders (PDs), but the results remain inconclusive. We aimed to identify specific differentially expressed miRNAs and their overlapping miRNA expression profiles in schizophrenia (SZ), major depression disorder (MDD), and bipolar disorder (BD), the three major PDs.

Methods

The literatures up to September 30, 2023 related to peripheral blood miRNAs and PDs were searched and screened from multiple databases. The differences in miRNA levels between groups were illustrated by the standardized mean difference (SMD) and 95% confidence interval (95% CI).

Results

In total, 30 peripheral blood miRNAs were included in the meta-analysis, including 16 for SZ, 12 for MDD, and 2 for BD, each was reported in more than 3 independent studies. Compared with the control group, miR-181b-5p, miR-34a-5p, miR-195-5p, miR-30e-5p, miR-7-5p, miR-132-3p, miR-212-3p, miR-206, miR-92a-3p and miR-137-3p were upregulated in SZ, while miR-134-5p, miR-107 and miR-99b-5p were downregulated. In MDD, miR-124-3p, miR-132-3p, miR-139-5p, miR-182-5p, miR-221-3p, miR-34a-5p and miR-93-5p were upregulated, while miR-144-5p and miR-135a-5p were downregulated. However, we failed to identify statistically differentially expressed miRNAs in BD. Interestingly, miR-132-3p and miR-34a-5p were upregulated in both SZ and MDD.

Conclusions

Our study identified 13 differentially expressed miRNAs in SZ and 9 in MDD, among which miR-132-3p and miR-34a-5p were upregulated in both SZ and MDD by systematically analyzing qualified studies. These miRNAs may be used as potential biomarkers for the diagnosis of SZ and MDD in the future.

Systematic Review Registration

http://www.crd.york.ac.uk/PROSPERO, identifier CRD42023486982.

Diagnostic significance and potential function of miR-320d in schizophrenia

OBJECTIVES

Schizophrenia is a chronic brain disorder and needs objective diagnostic biomarkers. MicroRNAs are highly expressed in the nervous system. The study investigated the expression and clinical values of serum miR-320d in schizophrenia patients. In addition, the underlying mechanism was preliminarily examined via bioinformatic analysis.

MATERIALS AND METHODS

Serum samples were collected from 57 patients with first-episode schizophrenia and 62 healthy controls. The cognitive function of patients was assessed via Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus Cognitive Battery (MCCB) consisting of seven domains. Serum miR-320d levels were tested via qRT-PCR. The miRNA target predictions were obtained from Target Scan, and annotated through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis.

RESULTS

Based on the GSE167630 dataset, downregulated serum miR-320d in schizophrenia was identified, which was determined in the serum of schizophrenia patients. Serum miR-320d presented a conspicuous relationship with MCCB score in both the control group and the schizophrenia group. After adjusting for age, sex, BMI, and education, serum miR-320d was still independently related to the occurrence of schizophrenia. It can identify schizophrenia cases from healthy ones with an AUC of 0.931. The Go enrichment analysis indicated that the target genes were mainly enriched in homophilic cell adhesion and cell-cell adhesion via plasma-membrane adhesion molecules, and GTPase activity and guanosine diphosphate (GDP) binding. Rap1 signaling pathway was enriched via KEGG analysis.

CONCLUSION

Serum miR-320d can be taken as a candidate marker for the diagnosis of schizophrenia. Its regulatory role in neuronal cell adhesion and Rap1 signaling pathway might be the potential underlying mechanism of miR-320d in schizophrenia.

Exploratory Analysis of MicroRNA Alterations in a Neurodevelopmental Mouse Model for Autism Spectrum Disorder and Schizophrenia

MicroRNAs (miRNAs) play a crucial role in the regulation of gene expression levels and have been implicated in the pathogenesis of autism spectrum disorder (ASD) and schizophrenia (SCZ). In this study, we examined the adult expression profiles of specific miRNAs in the prefrontal cortex (PFC) of a neurodevelopmental mouse model for ASD and SCZ that mimics perinatal pathology, such as NMDA receptor hypofunction, and exhibits behavioral and neurophysiological phenotypes related to these disorders during adulthood. To model the early neuropathogenesis of the disorders, mouse pups were administered subcutaneously with ketamine (30 mg/Kg) at postnatal days 7, 9, and 11. We focused on a set of miRNAs most frequently altered in ASD (miR-451a and miR-486-3p) and in SCZ (miR-132-3p and miR-137-3p) according to human studies. Additionally, we explored miRNAs whose alterations have been identified in both disorders (miR-21-5p, miR-92a-2-5p, miR-144-3p, and miR-146a-5p). We placed particular emphasis on studying the sexual dimorphism in the dynamics of these miRNAs. Our findings revealed significant alterations in the PFC of this ASD- and SCZ-like mouse model. Specifically, we observed upregulated miR-451a and downregulated miR-137-3p. Furthermore, we identified sexual dimorphism in the expression of miR-132-3p, miR-137-3p, and miR-92a-2-5p. From a translational perspective, our results emphasize the potential involvement of miR-92a-2-5p, miR-132-3p, miR-137-3p, and miR-451a in the pathophysiology of ASD and SCZ and strengthen their potential as biomarkers and therapeutic targets of such disorders.

MicroRNA-451a is a candidate biomarker and therapeutic target for major depressive disorder

Background

Increasing evidence supports the role of microRNAs (miRNAs) in major depressive disorder (MDD), but the pathophysiological mechanism remains elusive.

Aims

To explore the mechanism of microRNA-451a (miR-451a) in the pathology and behaviours of depression.

Methods

Abnormal miRNAs such as miR-451a reported previously in the serum of patients with MDD were screened and then confirmed in a mouse model of depression induced by chronic restraint stress (CRS). Eight-week-old male C57BL/6 mice had miR-451a overexpression in the medial prefrontal cortex (mPFC) via adeno-associated virus serotype 9 vectors encoding a pri-mmu-miR-451a-GFP fusion protein followed by behavioural and pathological analyses. Finally, molecular biological experiments were conducted to investigate the potential mechanism of miR-451a against depression.

Results

The serum levels of miRNA-451a were significantly lower in patients with MDD, with a negative correlation with the Hamilton Depression Scale scores. Additionally, a negative association between serum miR-451a and behavioural despair or anhedonia was observed in CRS mice. Notably, miR-451a expression was significantly downregulated in the mPFC of CRS-susceptible mice. Overexpressing miR-451a in the mPFC reversed the loss of dendritic spines and the depression-like phenotype of CRS mice. Mechanistically, miR-451a could inhibit CRS-induced corticotropin-releasing factor receptor 1 expression via targeting transcription factor 2, subsequently protecting dendritic spine plasticity.

Conclusions

Together, these results highlighted miR-451a as a candidate biomarker and therapeutic target for MDD.

Extracellular vesicles from cerebrospinal fluid revealed changes in miR-19a-3p and miR-4516 expression in Slovene male suicides

Suicide is an important public-health concern, with more than 700,000 people dying by suicide yearly. It is a multifactorial phenomenon, shaped by the effects of sociodemographic, environmental and biological factors. The latter two factors can be linked through epigenetic studies, which examine differences in gene expression that are not due to changes in the DNA sequence itself. Epigenetic mechanisms include micro RNAs (miRNAs), which have a direct effect on already translated mRNA, leading to either decay or translational repression of the target mRNA. MiRNA molecules have been identified as cargo of extracellular vesicles (EVs) used by cells for long-distance communication, and pathophysiological changes in miRNA in brain cells may be reflected in cerebrospinal fluid (CSF) vesicles. In this study we investigated the presence and differential expression of selected miRNAs in EVs from the CSF of male suicide completers and controls. Western blot and nanoparticle tracking analyses confirmed the presence of small and medium sized EVs. Of the miRNA analyzed (miR-16-5p, miR-19a-3p, miR-34c-5p, miR-17-5p, miR-4286, miR-26b-5p, miR-381-3p, and miR-4516) miR-19a-3p and miR-4516 reached statistical significance with p-values of 0.0408 and 0.0168, respectively. Mir-4516 and miRNA-19a-3p have been previously studied in suicide, and target SLC6A4 and TNF-α expression, correspondingly. Approximately 70% of known miRNAs are expressed in the central nervous system, and therefore represent an important biomarker potential. Investigating the cargo of CFS and blood EVs would further support the identification of miRNAs with clinical use potential.

miR-218-5p and miR-320a-5p as Biomarkers for Brain Disorders: Focus on the Major Depressive Disorder and Parkinson's Disease

Depression is one of the early and most persistent non-motor symptoms of Parkinson's disease (PD), which remains ignored, resulting in the underdiagnosis of PD. Unfortunately, scarce studies and the non-availability of diagnostic strategies cause countless complications, highlighting the need for appropriate diagnostic biomarkers. Recently, brain-enriched miRNAs regulating vital neurological functions have been proposed as potent biomarkers for therapeutic strategies. Therefore, the present study is aimed to identify the brain-enriched miR-218-5p and miR-320-5p in the serum of the Chinese depressed PD patients (n = 51) than healthy controls (n = 51) to identify their potency as biomarkers. For this purpose, depressive PD patients were recruited based on HAMA and HAMD scores and miR-218-5p and miR-320-5p and IL-6, and S100B levels were analyzed using real-time PCR (qRT-PCR) and ELISA assay, respectively. In silico analysis was performed to identify key biological pathways and hub genes involved in the psychopathology of depression in PD. Here, we found significantly downregulated miR-218-5p and miR-320-5p following higher levels of IL-6 and S100B in depressed PD patients than in control (p < 0.05). The correlation analysis revealed that both miRNAs were negatively correlated with HAMA and HAMD, and IL-6 scores, along with a positive correlation with PD duration and LEDD medication. ROC analysis showed AUC above 75% in both miRNAs in depressed PD patients, and in silico analysis revealed that both miRNA's targets regulate key neurological pathways such as axon guidance, dopaminergic synapse, and circadian rhythm. Additional analysis revealed PIK3R1, ATRX, BM1, PCDHA10, XRCC5, PPP1CB, MLLT3, CBL, PCDHA4, PLCG1, YWHAZ, CDH2, AGO3, PCDHA3, and PCDHA11 as hub-genes in PPI network. In summary, our findings show that miR-218-5p and miR-320-5p can be utilized as future biomarkers for depression in PD patients, which may aid in the early diagnosis and treatment of Parkinson's disease.

Epigenetic regulation in major depression and other stress-related disorders: molecular mechanisms, clinical relevance and therapeutic potential

Major depressive disorder (MDD) is a chronic, generally episodic and debilitating disease that affects an estimated 300 million people worldwide, but its pathogenesis is poorly understood. The heritability estimate of MDD is 30-40%, suggesting that genetics alone do not account for most of the risk of major depression. Another factor known to associate with MDD involves environmental stressors such as childhood adversity and recent life stress. Recent studies have emerged to show that the biological impact of environmental factors in MDD and other stress-related disorders is mediated by a variety of epigenetic modifications. These epigenetic modification alterations contribute to abnormal neuroendocrine responses, neuroplasticity impairment, neurotransmission and neuroglia dysfunction, which are involved in the pathophysiology of MDD. Furthermore, epigenetic marks have been associated with the diagnosis and treatment of MDD. The evaluation of epigenetic modifications holds promise for further understanding of the heterogeneous etiology and complex phenotypes of MDD, and may identify new therapeutic targets. Here, we review preclinical and clinical epigenetic findings, including DNA methylation, histone modification, noncoding RNA, RNA modification, and chromatin remodeling factor in MDD. In addition, we elaborate on the contribution of these epigenetic mechanisms to the pathological trait variability in depression and discuss how such mechanisms can be exploited for therapeutic purposes.

The role of Extracellular Genomic Materials (EGMs) in psychiatric disorders

Extracellular Genomic Materials (EGMs) are the nucleic acids secreted or released from all types of cells by endogenous or exogenous stimuli through varying mechanisms into the extracellular region and inevitably to all biological fluids. EGMs could be found as free, protein-bound, and/ or with vesicles. EGMs can potentially have immunophenotypic and/or genotypic characteristics of a cell of origin, travel to distant organs, and interact with the new microenvironment. To achieve all, EGMs might bi-directionally transit through varying membranes, including the blood-brain barrier. Such ability provides the transfer of any information related to the pathophysiological changes in psychiatric disorders in the brain to the other distant organ systems or vice versa. In this article, many aspects of EGMs have been elegantly reviewed, including their potential in diagnosis as biomarkers, application in treatment modalities, and functional effects in the pathophysiology of psychiatric disorders. The psychiatric disorders were studied under subgroups of Schizophrenia spectrum disorders, bipolar disorder, depressive disorders, and an autism spectrum disorders. EGMs provide a robust and promising tool in clinics for prognosis and diagnosis. The successful application of EGMs into treatment modalities might further provide encouraging outcomes for researchers and clinicians in psychiatric disorders.

Circulating plasma and exosome levels of the miR-320 family as a non-invasive biomarker for methamphetamine use disorder

The neurobiological mechanism underlying methamphetamine (MA) use disorder was still unclear, and no specific biomarker exists for clinical diagnosis of this disorder. Recent studies have demonstrated that microRNAs (miRNAs) are involved in the pathological process of MA addiction. The purpose of this study was to identify novel miRNAs for the diagnosis biomarkers of MA user disorder. First, members of the miR-320 family, including miR-320a-3p, miR-320b, and miR-320c, were screened and analyzed in the circulating plasma and exosomes by microarray and sequencing. Secondly, plasma miR-320 was quantified by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) in eighty-two MA patients and fifty age-gender-matched healthy controls. Meanwhile, we also analyzed exosomal miR-320 expression in thirty-nine MA patients and twenty-one age-matched healthy controls. Furthermore, the diagnostic power was evaluated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curve. The expression of miR-320 significantly increased in plasma and exosomes of MA patients compared with healthy controls. The AUC of the ROC curves of miR-320 in plasma and exosomes of MA patients were 0.751 and 0.962, respectively. And the sensitivities of miR-320 were 0.900 and 0.846, respectively, whereas the specificities of miR-320 were 0.537 and 0.952, respectively, in plasma and exosomes in MA patients. And the increased plasma miR-320 was positively correlated with cigarette smoking, age of onset, and daily use of MA in MA patients. Finally, cardiovascular disease, synaptic plasticity, and neuroinflammation were predicted to be the target pathways related to miR-320. Taken together, our findings indicated that plasma and exosomal miR-320 might be used as a potential blood-based biomarker for diagnosing MA use disorder.

The role of microRNAs in depression

Major depressive disorder (MDD) is a psychiatric disorder with increasing prevalence worldwide. It is a leading cause of disability and suicide, severely affecting physical and mental health. However, the study of depression remains at an exploratory stage in terms of diagnostics and treatment due to the complexity of its pathogenesis. MicroRNAs are endogenous short-stranded non-coding RNAs capable of binding to the 3’untranslated region of mRNAs. Because of their ability to repress translation process of genes and are found at high levels in brain tissues, investigation of their role in depression has gradually increased recently. This article summarizes recent research progress on the relationship between microRNAs and depression. The microRNAs play a regulatory role in the pathophysiology of depression, involving dysregulation of monoamines, abnormalities in neuroplasticity and neurogenesis, hyperactivity of the HPA axis, and dysregulation of inflammatory responses. These microRNAs might provide new clue for the diagnosis and treatment of MDD, and the development of antidepressant drugs.

MiR-1281 is involved in depression disorder and the antidepressant effects of Kai-Xin-San by targeting ADCY1 and DVL1

Kai-Xin-San (KXS) is a Chinese medicine formulation that is commonly used to treat depression caused by dual deficiencies in the heart and spleen. Recent studies indicated that miRNAs were involved in the pathophysiology of depression. However, there have been few studies on the mechanism underlying the miRNAs directly mediating antidepressant at clinical level, especially in nature drugs and TCM compound. In this study, we identified circulating miRNAs defferentially expressed among the depression patients (DPs), DPs who underwent 8weeks of KXS treatment and health controls (HCs). A total of 45 miRNAs (17 were up-regulated and 28 were down-regulated) were significantly differentially expressed among three groups. Subsequently, qRT-PCR was used to verify 10 differentially expressed candidate miRNAs in more serum samples, and the results showed that 6 miRNAs (miR-1281, miR-365a-3p, miR-2861, miR-16-5p, miR-1202 and miR-451a) were consistent with the results of microarray. Among them, miR-1281, was the novel dynamically altered and appeared to be specifically related to depression and antidepressant effects of KXS. MicroRNA-gene-pathway-net analysis showed that miR-1281-regulated genes are mostly key nodes in the classical signaling pathway related to depression. Additionally, our data suggest that ADCY1 and DVL1 were the targets of miR-1281. Thus, based on the discovery of miRNA expression profiles in vivo, our findings suggest a new role for miR-1281 related to depression and demonstrated in vitro that KXS may activate cAMP/PKA/ERK/CREB and Wnt/β-catenin signal transduction pathways by down-regulating miR-1281 that targets ADCY1 and DVL1 to achieve its role in neuronal cell protection.

Electroconvulsive Stimulation in Rats Induces Alterations in the Hippocampal miRNome: Translational Implications for Depression

MicroRNAs (miRNAs) may contribute to the development of depression and its treatment. Here, we used the hypothesis-neutral approach of next-generation sequencing (NGS) to gain comprehensive understanding of the effects of a course of electroconvulsive stimulation (ECS), the animal model equivalent of electroconvulsive therapy (ECT), on rat hippocampal miRNAs. Significant differential expression (p < 0.001) of six hippocampal miRNAs was noted following NGS, after correcting for multiple comparisons. Three of these miRNAs were upregulated (miR-132, miR-212, miR-331) and three downregulated (miR-204, miR-483, miR-301a). qRT-PCR confirmed significant changes in four of the six miRNAs (miR-132, miR-212, miR-204, miR-483). miR-483 was also significantly reduced in frontal cortex, though no other significant alterations were noted in frontal cortex, cerebellum, or whole blood. Assessing the translatability of the results, miR-132 and miR-483 were significantly reduced in whole blood samples from medicated patients with depression (n = 50) compared to healthy controls (n = 45), though ECT had no impact on miRNA levels. Notably, pre-ECT miR-204 levels moderately positively correlated with depression severity at baseline and moderately negatively correlated with mood score reduction post-ECT. miRNAs were also examined in cerebrospinal fluid and serum from a separate cohort of patients (n = 8) treated with ECT; no significant changes were noted post-treatment. However, there was a large positive correlation between changes in miR-212 and mood score post-ECT in serum. Though replication studies using larger sample sizes are required, alterations in miRNA expression may be informative about the mechanism of action of ECS/ECT and in turn might give insight into the neurobiology of depression.

Potential of Circulating miRNAs as Molecular Markers in Mood Disorders and Associated Suicidal Behavior

Mood disorders are the most prevalent psychiatric disorders associated with significant disability, morbidity, and mortality. The risk of suicide is associated with severe or mixed depressive episodes in patients with mood disorders. However, the risk of suicide increases with the severity of depressive episodes and is often presented with higher incidences in bipolar disorder (BD) patients than in patients with major depression (MDD). Biomarker study in neuropsychiatric disorders is critical for developing better treatment plans by facilitating more accurate diagnosis. At the same time, biomarker discovery also provides more objectivity to develop state-of-the-art personalized medicine with increased accuracy through clinical interventions. Recently, colinear changes in miRNA expression between brain and systemic circulation have added great interest in examining their potential as molecular markers in mental disorders, including MDD, BD, and suicidality. A present understanding of circulating miRNAs in body fluids implicates their role in managing neuropsychiatric conditions. Most notably, their use as prognostic and diagnostic markers and their potential role in treatment response have significantly advanced our knowledge base. The present review discusses circulatory miRNAs and their underlying possibilities to be used as a screening tool for assessing major psychiatric conditions, including MDD, BD, and suicidal behavior.

Elevated Serum Macrophage Migration Inhibitory Factor Levels are Associated With Major Depressive Disorder

Background

Previous studies have suggested the involvement of an activated inflammatory process in major depressive disorder (MDD), as altered expression of inflammatory cytokines is observed in depression. This alteration can be the cause or a consequence of MDD. However, acknowledging inflammatory cytokines as prospective biomarkers would aid in diagnosing or guiding better therapeutic options. Therefore, we designed this study to assess the macrophage migration inhibitory factor (MIF) in depression.

Method

We collected blood samples from 115 MDD patients and 113 healthy controls (HCs) matched by age and sex. MDD patients were diagnosed by a qualified psychiatrist based on the symptoms mentioned in the diagnostic and statistical manual of mental disorders (DSM-5). We applied the Hamilton depression (Ham-D) rating scale to assess the severity of depression. We assessed serum levels of MIF using ELISA kit (Boster Bio, USA).

Result

We detected increased serum MIF levels in MDD patients compared to HCs (6.15 ± 0.23 ng/mL vs 3.95 ± 0.21 ng/mL, P < 0.001). Moreover, this increase is more among female patients than female controls. Also, we noticed a positive correlation between altered MIF levels and the Ham-D scores (r = 0.233; P = 0.012), where we found that patients who scored higher on the Ham-D scale had higher MIF levels in serum. Moreover, the area under the curve (AUC) of receiver operating characteristic (ROC) curve represented the good diagnostic performance of altered serum MIF.

Conclusion

Our study findings indicate the association of pro-inflammatory cytokine MIF in the pathophysiology of depression as we identified elevated serum MIF levels in depressive patients compared to HCs. However, more researches are required to confirm whether this alteration of cytokine is the causative factor or a consequence of depression. We recommend conducting further studies to understand the pattern of this alteration of MIF levels in MDD patients.

Plasma Exo-miRNAs Correlated with AD-Related Factors of Chinese Individuals Involved in Aβ Accumulation and Cognition Decline

Numerous studies have investigated the risk factors of Alzheimer’s disease (AD); however, AD-risk factors related miRNAs were rarely reported. In this study, AD-risk factor related miRNAs of 105 Chinese individuals (45 AD patients and 60 cognitively normal controls) were investigated. The results showed that Hsa-miR-185-5p, Hsa-miR-20a-5p, and Hsa-miR-497-5p were related to AD and education, Hsa-miR-185-5p, Hsa-miR-181c-5p, Hsa-miR-664a-3p, Hsa-miR-27a-3p, Hsa-miR-451a, and Hsa-miR-320a were related to AD and depression. Target prediction of above miRNAs showed that these miRNAs were involved in the generation and clearance of amyloid-beta (Aβ), important molecules related to cognition, and disease-activated microglia response to AD. It is worth noting that Hsa-miR-185-5p was related to both education and depression, whose decreased expression pattern in AD patients was alleviated by education and enhanced by depression, and participates in Aβ generation and accumulation. Our results indicated that certain education and depression factors can contribute to AD progression by modulating miRNA expression, implying that preventive interventions might alter AD progression in Chinese patients.

miRNAs as potential diagnostic biomarkers and pharmacogenomic indicators in psychiatric disorders

The heterogeneity of psychiatric disorders and the lack of reliable biomarkers for prediction and treatments follow-up pose difficulties towards recognition and understanding of the molecular basis of psychiatric diseases. However, several studies based on NGS approaches have shown that miRNAs could regulate gene expression during onset and disease progression and could serve as potential diagnostic and pharmacogenomics biomarkers during treatment. We provide herein a detailed overview of circulating miRNAs and their expression profiles as biomarkers in schizophrenia, bipolar disorder and major depressive disorder and their role in response to specific treatments. Bioinformatics analysis of miR-34a, miR-106, miR-134 and miR-132, which are common among SZ, BD and MDD patients, showed brain enrichment and involvement in the modulation of critical signaling pathways, which are often deregulated in psychiatric disorders. We propose that specific miRNAs support accurate diagnosis and effective precision treatment of psychiatric disorders.

A New Player in Depression: MiRNAs as Modulators of Altered Synaptic Plasticity

Depression is a psychiatric disorder that presents with a persistent depressed mood as the main clinical feature and is accompanied by cognitive impairment. Changes in neuroplasticity and neurogenesis greatly affect depression. Without genetic changes, epigenetic mechanisms have been shown to function by regulating gene expression during the body’s adaptation to stress. Studies in recent years have shown that as important regulatory factors in epigenetic mechanisms, microRNAs (miRNAs) play important roles in the development and progression of depression through the regulation of protein expression. Herein, we review the mechanisms of miRNA-mediated neuroplasticity in depression and discus synaptic structural plasticity, synaptic functional plasticity, and neurogenesis. Furthermore, we found that miRNAs regulate neuroplasticity through several signalling pathways to affect cognitive functions. However, these pathways do not work independently. Therefore, we try to identify synergistic correlations between miRNAs and multiple signalling pathways to broaden the potential pathogenesis of depression. In addition, in the future, dual-function miRNAs (protection/injury) are promising candidate biomarkers for the diagnosis of depression, and their regulated genes can potentially be used as target genes for the treatment of depression.

TINY IN SIZE, BIG IN IMPACT: EXTRACELLULAR VESICLES AS MODULATORS OF MOOD, ANXIETY AND NEURODEVELOPMENTAL DISORDERS

Extracellular Vesicles (EVs) are tiny vesicles used by cells as means of cellular communication, through which the function and state of a given cell can be changed. A body of evidence has suggested that EVs could be culprits in the development and progression of various types of diseases, including neurodegenerative diseases such as Multiple Sclerosis (MS) and Alzheimer's Disease (AD). Unsurprisingly, EVs have also been implicate in mood, anxiety and neurodevelopmental disorders, such as Major Depressive Disorder (MDD), anxiety disorder and Autism-Spectrum Disorder (ASD), respectively. Here, we review the state-of-art regarding the roles of EVs in the aforementioned diseases and focus on the mechanisms by which they can cause and worsen disease. Harnessing the knowledge of EVs is not only important to deliver different cargos to cells in a specific manner to treat these diseases, but also to establish reliable disease biomarkers, which will aid in the early disease diagnosis and treatment, increasing the chance of successful treatment.

Circulating hsa-let-7e-5p and hsa-miR-125a-5p as Possible Biomarkers in the Diagnosis of Major Depression and Bipolar Disorders

Background. Evidence shows that microRNAs (miRNAs) could play a key role in the homeostasis and development of major depressive disorder and bipolar disorder. The present study is aimed at investigating the changes in circulating miRNA expression profiles in a plasma of patients suffering from major depressive disorder (MDD) and bipolar disorder (BD) to distinguish and evaluate these molecules as biomarkers for mood disorders. Methods. A study enrolled a total of 184 subjects: 74 controls, 84 MDD patients, and 26 BD patients. Small RNA sequencing revealed 11 deregulated circulating miRNAs in MDD and BD plasma, of which expression of 5, hsa-miR-139-3p, miRNAs hsa-let-7e-5p, hsa-let-7f-5p, hsa-miR-125a-5p, and hsa-miR-483-5p, were further verified using qPCR. miRNA gene expression data was evaluated alongside the data from clinical assessment questionnaires. Results. hsa-let-7e-5p and hsa-miR-125a-5p were both confirmed upregulated: 0.75-fold and 0.25-fold, respectively, in the MDD group as well as 1.36-fold and 0.68-fold in the BD group. Receiver operating curve (ROC) analysis showed mediocre diagnostic sensitivity and specificity of both hsa-let-7e-5p and hsa-miR-125a-5p with approximate area under the curve (AOC) of 0.66. ROC analysis of combined miRNA and clinical assessment data showed that hsa-let-7e-5p and hsa-miR-125a-5p testing could improve MDD and BD diagnostic accuracy by approximately 10%. Conclusions. Circulating hsa-let-7e-5 and hsa-miR-125a-5p could serve as additional peripheral biomarkers for mood disorders; however, suicidal ideation remains the major diagnostic factor for MDD and BD.

A Systematic Review of Circulatory microRNAs in Major Depressive Disorder: Potential Biomarkers for Disease Prognosis

Major depressive disorder (MDD) is a neuropsychiatric disorder, which remains challenging to diagnose and manage due to its complex endophenotype. In this aspect, circulatory microRNAs (cimiRNAs) offer great potential as biomarkers and may provide new insights for MDD diagnosis. Therefore, we systemically reviewed the literature to explore various cimiRNAs contributing to MDD diagnosis and underlying molecular pathways. A comprehensive literature survey was conducted, employing four databases from 2012 to January 2021. Out of 1004 records, 157 reports were accessed for eligibility criteria, and 32 reports meeting our inclusion criteria were considered for in-silico analysis. This study identified 99 dysregulated cimiRNAs in MDD patients, out of which 20 cimiRNAs found in multiple reports were selected for in-silico analysis. KEGG pathway analysis indicated activation of ALS, MAPK, p53, and P13K-Akt signaling pathways, while gene ontology analysis demonstrated that most protein targets were associated with transcription. In addition, chromosomal location analysis showed clustering of dysregulated cimiRNAs at proximity 3p22-p21, 9q22.32, and 17q11.2, proposing their coregulation with specific transcription factors primarily involved in MDD physiology. Further analysis of transcription factor sites revealed the existence of HIF-1, REST, and TAL1 in most cimiRNAs. These transcription factors are proposed to target genes linked with MDD, hypothesizing that first-wave cimiRNA dysregulation may trigger the second wave of transcription-wide changes, altering the protein expressions of MDD-affected cells. Overall, this systematic review presented a list of dysregulated cimiRNAs in MDD, notably miR-24-3p, let 7a-5p, miR-26a-5p, miR135a, miR-425-3p, miR-132, miR-124 and miR-16-5p as the most prominent cimiRNAs. However, various constraints did not permit us to make firm conclusions on the clinical significance of these cimiRNAs, suggesting the need for more research on single blood compartment to identify the biomarker potential of consistently dysregulated cimiRNAs in MDD, as well as the therapeutic implications of these in-silico insights.

Mechanism of Depression through Brain Function Imaging of Depression Patients and Normal People

In recent years, functional magnetic resonance technology has discovered that abnormal connections in different brain regions of the brain may serve as the pathophysiological mechanism of mental illness. Exploring the mechanism of information flow and integration between different brain regions is of great significance for understanding the pathophysiological mechanism of mental illness. This article aims to analyze the mechanism of depression by comparing human brain images of normal people and patients with depression and conduct research. Fluoxetine, a selective 5-HT reuptake inhibitor (SSRI) widely used in clinical practice, can selectively inhibit 5-HT transporter and block the reuptake of 5-HT by the presynaptic membrane. The effect of 5-HT is prolonged and increased, thereby producing antidepressant effects. It has low affinity for adrenergic, histaminergic, and cholinergic receptors and has a weaker effect, resulting in fewer adverse reactions. This paper uses the comparative experiment method and the Welch method and uses the average shortest path length L to describe the average value of the shortest path length between two nodes in the network. Attention refers to the ability of a person's mental activity to point and to concentrate on something. Sustained attention means that attention is kept on a certain cognitive object or activity for a certain period of time, which is also called the stability of attention. The research on attention of depression patients generally focuses on continuous attention, and the results obtained show inconsistencies. Most studies have shown that the sustained attention of the depression group is significantly worse than that of the healthy control group. An overview of magnetic resonance imaging technology and an analysis of depression based on resting state were carried out. The key brain areas of the sample core network were scanned, and the ALFF results were analyzed. The data showed that the severity of depression in the depression group was negatively correlated with the ReHo value in the posterior left cerebellum (P=0.010). The sense of despair was negatively correlated with the ReHo value in the posterior right cerebellum (P=0.013). The diurnal variation was negatively correlated with the ReHo value of the left ring (P=0.014). It was positively correlated with the ReHo value of the left ventricle (P=0.048). This experiment has better completed the research on the mechanism of depression by analyzing the functional images of patients with depression and normal human brain.

Circulating microRNA associated with future relapse status in major depressive disorder

Major depressive disorder (MDD) is an episodic condition with relapsing and remitting disease course. Elucidating biomarkers that can predict future relapse in individuals responding to an antidepressant treatment holds the potential to identify those patients who are prone to illness recurrence. The current study explored relationships between relapse risk in recurrent MDD and circulating microRNAs (miRNAs) that participate in RNA silencing and post-transcriptional regulation of gene expression. Serum samples were acquired from individuals with a history of recurrent MDD who were followed longitudinally in the observational study, OBSERVEMDD0001 (ClinicalTrials.gov Identifier: NCT02489305). Circulating miRNA data were obtained in 63 participants who relapsed ("relapsers") and 154 participants who did not relapse ("non-relapsers") during follow-up. The miRNA was quantified using the ID3EAL™ miRNA Discovery Platform from MiRXES measuring 575 circulating miRNAs using a patented qPCR technology and normalized with a standard curve from spike-in controls in each plate. The association between miRNAs and subsequent relapse was tested using a linear model, adjusting for age, gender, and plate. Four miRNAs were nominally associated with relapse status during the observational follow-up phase with a false discover rate adjusted p-value < 0.1. Enrichment analysis of experimentally validated targets revealed 112 significantly enriched pathways, including neurogenesis, response to cytokine, neurotrophin signaling, vascular endothelial growth factor signaling, relaxin signaling, and cellular senescence pathways. These data suggest these miRNAs putatively associated with relapse status may have the potential to regulate genes involved in multiple signaling pathways that have previously been associated with MDD. If shown to be significant in a larger, independent sample, these data may hold potential for developing a miRNA signature to identify patients likely to relapse, allowing for earlier intervention.

Association of circulating let-7b-5p with major depressive disorder: a nested case-control study

BACKGROUND

Major depressive disorder (MDD) is one of the most common psychiatric disorders and is a great disease burden. However, its underlying pathophysiology and aetiology remain poorly understood. Available evidence suggests that circulating microRNAs (miRNAs) are associated with MDD, but it is still unknown whether miRNAs can predict subsequent incident MDD.

METHODS

In this nested case-control study, a total of 104 individuals, who were free of MDD at baseline, from the Women's Health in Lund Area (WHILA) cohort were included. Among them, 52 individuals developed MDD (cases) during the 5 years follow-up and 52 individuals did not develop MDD (controls). Plasma expression levels of miR-17-5p, miR-134-5p, miR-144-5p, let-7b-5p and let-7c-5p at baseline were assessed using qRT-PCR. Logistic regression was used to estimate the odds of developing MDD among individuals with different levels of miRNA expression.

RESULTS

Plasma expression levels of let-7b-5p were significantly lower (p = 0.02) at baseline in cases compared to controls. After adjustment for age and BMI, let-7b-5p was negatively associated with odds for developing MDD (OR = 0.33, p = 0.03, 95% CI = 0.12-0.91). Moreover, let-7b-5p expression levels showed a trend over time with larger differences between cases and controls for the earlier cases (MDD diagnosis <2 years from baseline) than MDD cases developed later (MDD diagnosis 2-5 years from baseline).

CONCLUSIONS

These findings show that lower plasma levels of let-7b-5p are associated with a higher future risk of MDD. Results need to be validated in a large cohort to examine its potential as a peripheral biomarker for MDD.

MicroRNAs as Critical Biomarkers of Major Depressive Disorder: A Comprehensive Perspective

Major Depressive Disorder (MDD) represents a major global health concern, a body-mind malady of rising prevalence worldwide nowadays. The complex network of mechanisms involved in MDD pathophysiology is subjected to epigenetic changes modulated by microRNAs (miRNAs). Serum free or vesicles loaded miRNAs have starred numerous publications, denoting a key role in cell-cell communication, systematically and in brain structure and neuronal morphogenesis, activity and plasticity. Upregulated or downregulated expression of these signaling molecules may imply the impairment of genes implicated in pathways of MDD etiopathogenesis (neuroinflammation, brain-derived neurotrophic factor (BDNF), neurotransmitters, hypothalamic-pituitary-adrenal (HPA) axis, oxidative stress, circadian rhythms...). In addition, these miRNAs could serve as potential biomarkers with diagnostic, prognostic and predictive value, allowing to classify severity of the disease or to make decisions in clinical management. They have been considered as promising therapy targets as well and may interfere with available antidepressant treatments. As epigenetic malleable regulators, we also conclude emphasizing lifestyle interventions with physical activity, mindfulness and diet, opening the door to new clinical management considerations.

Circulating microRNAs and Molecular Oxidative Stress in Older Adults with Neuroprogression Disorders

BACKGROUND

circulating microRNAs are potential blood biomarkers differentially expressed in many diseases including neuro depression disorders. It controls the expression of human genes and associated cellular and physiological processes in normal and diseased cells. We aimed to evaluate the potential role of circulating miRNAs and their association with both stress hormones and cellular oxidative stress in neuro depression disorders occurred among older adults.

METHODS

a total of 70 healthy subjects were included in this study. Based upon the profile of mood states (POMS-32 score), the participants classified into two groups; healthy subjects (n =30) and depression (n =40). The expression of microRNAs; miR-124, miR-34a-5p, miR-135, and miR-451-a and their correlation with cellular oxidative stress parameters; cellular NO, genes of SOD2, CAT and iNOS, and hormones; cortisol and serotonin were estimated by a quantitative real-time RT-PCR, high-performance liquid chromatography, and ELISA Immunoassay techniques, respectively.

RESULTS

depression was reported in 57.14% of the participants. The results showed a significant increase (p =0.01) in the total mood scores, and relative depression domains in older adults with depression compared to healthy controls. The relative expression levels of miR-124, miR-34a-5p significantly increased and the expression levels of miR-135, and miR-451-a significantly decreased in older adults with depression compared to healthy controls. In addition, the levels of cortisol significantly increased and serotonin (5HT) significantly reduced in all participants with depression. Cellular oxidative stress analysis for depressed subjects showed that serum NO levels and the expression of iNO gene significantly increased conversely with a decline in the molecular expression antioxidative genes; SOD2, CAT, respectively. The results showed that cellular oxidative stress parameters correlated positively with depression scores, cortisol, and negatively with cellular serotonin levels. In depressed subjects, the relative expression of microRNAs correlated positively with depression score, NO, iNOS, cortisol, and negatively associated with SOD2, CAT, and serotonin.

CONCLUSION

The combination of cellular oxidative stress and hormonal levels strongly supports a role for circulating miRNAs; miR-124, miR-34a-5p, miR-135, and miR-451-a in the regulation of depression and mood disorders among older adults. The expressed microRNAs with their related association to cellular oxidative stress and adrenal hormones are a step towards understanding the role of these small RNA molecules in the progression of depression among older adults. Thus, cellular miRNAs might have a prognostic role in the diagnosis and as a target for treatment strategies in depressed subjects.

The miRNome of Depression

Depression is an effect of complex interactions between genetic, epigenetic and environmental factors. It is well established that stress responses are associated with multiple modest and often dynamic molecular changes in the homeostatic balance, rather than with a single genetic factor that has a strong phenotypic penetration. As depression is a multifaceted phenotype, it is important to study biochemical pathways that can regulate the overall allostasis of the brain. One such biological system that has the potential to fine-tune a multitude of diverse molecular processes is RNA interference (RNAi). RNAi is an epigenetic process showing a very low level of evolutionary diversity, and relies on the posttranscriptional regulation of gene expression using, in the case of mammals, primarily short (17–23 nucleotides) noncoding RNA transcripts called microRNAs (miRNA). In this review, our objective was to examine, summarize and discuss recent advances in the field of biomedical and clinical research on the role of miRNA-mediated regulation of gene expression in the development of depression. We focused on studies investigating post-mortem brain tissue of individuals with depression, as well as research aiming to elucidate the biomarker potential of miRNAs in depression and antidepressant response.

The role of circulating blood microRNA-374 and microRNA-10 levels in the pathogenesis and therapeutic mechanisms of major depressive disorder

Compelling recent evidence suggests that microRNAs (miRNAs) regulate specific mRNA transcripts at the transcriptomic level and coordinately influence complex regulatory networks, which may play a crucial role in the pathogenesis of major depressive disorder (MDD) and the treatment effects of antidepressants. To evaluate the possible involvement of miRNAs in the pathophysiology and therapeutic response of MDD, we conducted a miRNA expression array analysis of the peripheral blood mononuclear cells (PBMCs) of 5 depressed patients and 5 healthy controls (HCs). Subsequently, we chose 2 miRNAs for validation with real-time PCR (RT-PCR) analysis pre- and post-treatment in another group of 25 MDD patients and 25 HCs. In the array, 5 miRNAs were differentially expressed in medication-naïve MDD patients compared to HCs, of which 2 miRNAs were upregulated and 3 were downregulated. Furthermore, in comparison with HCs, MDD patients showed significantly lower expression levels of miR-374b and miR-10a before treatment. After 8 weeks of antidepressant treatment, both miR-374b and the miR-10a expression levels in MDD patients were significantly elevated only in responders. In conclusion, these results indicate the involvement of miR-374b and miR-10a in the biological mechanisms and therapeutic response of MDD, and provide new insights for exploring miRNAs as potential biomarkers for MDD.

Uncovering the Roles of MicroRNAs in Major Depressive Disorder: From Candidate Diagnostic Biomarkers to Treatment Response Indicators

Major depressive disorder (MDD) is a recurrent debilitating illness that represents a major health burden due to its increasing worldwide prevalence, unclear pathological mechanism, nonresponsive treatment, and lack of reliable and specific diagnostic biomarkers. Recently, microRNA species (miRs) have gained particular interest because they have the ability to post-transcriptionally regulate gene expression by modulating mRNA stability and translation in a cohesive fashion. By regulating entire genetic circuitries, miRs have been shown to have dysregulated expression levels in blood samples from MDD patients, when compared to healthy subjects. In addition, antidepressant treatment (AD) also appears to alter the expression pattern of several miRs. Therefore, we critically and systematically reviewed herein the studies assessing the potential biomarker role of several candidate miRs for MDD, as well as treatment response monitoring indicators, in order to enrich the current knowledge and facilitate possible diagnostic biomarker development for MDD, which could aid in reducing both patients' burden and open novel avenues toward a better understanding of MDD neurobiology.

Non-coding RNAs in depression: Promising diagnostic and therapeutic biomarkers

Non-coding RNAs (ncRNAs), including microRNAs, circular RNAs, and long non-coding RNAs, are important regulators of normal biological processes and their abnormal expression may be involved in the pathogenesis of human diseases including depression. Multiple studies have demonstrated a significantly increased or reduced ncRNAs expression in depressed patients compared with healthy subjects and that antidepressant therapy can alter the aberrant expression of ncRNAs in depressed patients. Although the existing evidence is important, it is also mixed and a comprehensive review to guide an effective clinical translation is lacking. Focused on human research, this review summarizes clinical findings of ncRNAs in depression, including those in brain tissues and peripheral samples. We outlined the characteristics and functions of ncRNAs and highlighted their performance in the diagnosis and treatment of depression. Although their precise roles in depression remain uncertain, ncRNAs have shown potential value as biomarkers for diagnosis and therapy in depressed patients.

Nrf2 Alleviates Cognitive Dysfunction and Brain Inflammatory Injury via Mediating Wfs1 in Rats with Depression-Like Behaviors

Depression is a major threat to global mental health and demands targeted therapeutic regimens. The current study set out to evaluate the regulatory mechanism of nuclear factor erythroid-2 related factor 2 (Nrf2) in depression-induced cognitive dysfunction and inflammatory injury. First, depressive rat models were established via chronic unpredicted mild stress (CUMS) treatment. Cognitive function of rats was assessed by a series of behavioral tests. Rats were further stereotactically injected with Nrf2 overexpression vector, with expression patterns of Nrf2, miR-17-5p, and wolfram syndrome 1 (Wfs1) detected using qRT-PCR and Western blot assay. In addition, pathological changes of murine hippocampus were analyzed using hematoxylin-eosin staining. In vitro cell models were additionally established using lipopolysaccharide. Cell viability was detected via the CCK-8 method. Moreover, levels of TNF-α, IL-1β, and IL-10 were detected via ELISA. Furthermore, the binding relationships between Nrf2 and the miR-17-5p promoter, miR-17-5p, and Wfs1 were verified. It was found that Nrf2 was weakly expressed in CUMS-treated rats, whereas Nrf2 upregulation alleviated cognitive dysfunction and brain inflammatory injury. Meanwhile, Nrf2 inhibited miR-17-5p expression via binding to the miR-17-5p promoter. miR-17-5p was also found to limit Wfs1 transcription. miR-17-5p overexpression or Wfs1 downregulation partly reversed the role of Nrf2 in reliving inflammatory injury of murine hippocampal neurons. Overall, our findings indicated that Nrf2 inhibited miR-17-5p expression and promoted Wfs1 transcription, thereby alleviating cognitive dysfunction and inflammatory injury in rats with depression-like behaviors.

Cataloging recent advances in epigenetic alterations in major mental disorders and autism

During the last two decades, diverse epigenetic modifications including DNA methylation, histone modifications, RNA editing and miRNA dysregulation have been associated with psychiatric disorders. A few years ago, in a review we outlined the most common epigenetic alterations in major psychiatric disorders (e.g., aberrant DNA methylation of DTNBP1, HTR2A, RELN, MB-COMT and PPP3CC, and increased expression of miR-34a and miR-181b). Recent follow-up studies have uncovered other DNA methylation aberrations affecting several genes in mental disorders, in addition to dysregulation of many miRNAs. Here, we provide an update on new epigenetic findings and highlight potential origin of the diversity and inconsistencies, focusing on drug effects, tissue/cell specificity of epigenetic landscape and discuss shortcomings of the current diagnostic criteria in mental disorders.

MicroRNAs, Multiple Sclerosis, and Depression

Multiple sclerosis (MS) is a chronic disease of the central nervous system that affects the brain and spinal cord. There are several disease courses in MS including relapsing–remitting MS (RRMS), primary progressive MS (PPMS), and secondary progressive MS (SPMS). Up to 50% of MS patients experience depressive disorders. Major depression (MD) is a serious comorbidity of MS. Many dysfunctions including neuroinflammation, peripheral inflammation, gut dysbiosis, chronic oxidative and nitrosative stress, and neuroendocrine and mitochondrial abnormalities may contribute to the comorbidity between MS and MD. In addition to these actions, medical treatment and microRNA (miRNA) regulation may also be involved in the mechanisms of the comorbidity between MS and MD. In the study, I review many common miRNA biomarkers for both diseases. These common miRNA biomarkers may help further explore the association between MS and MD.

Neural extracellular vesicle-derived miR-17 in blood as a potential biomarker of subthreshold depression

Subthreshold depression (StD) is a depressive state that does not fulfil the criteria for major depressive disorder (MDD); however, StD has a risk for progression to MDD, and early intervention is therefore needed. Recently, a method for extracting neural extracellular vesicles (NEVs) excreted from neural cells of the brain from blood has been established, and microRNAs (miRNAs) encapsulated in NEVs are attracting interest because of their potential correlation to the pathogenesis of psychiatric disorders. However, miRNAs closely related to StD are still unknown. Therefore, to try to identify miRNAs closely related to the degree of StD, we examined the correlations between expression levels of some candidate miRNAs in NEVs and Patient Health Questionnaire-9 (PHQ-9) scores in subjects. Total RNAs in NEVs were extracted from serum of young adult males who had PHQ-9 scores of less than 10 (n = 9). Expression levels of eight miRNAs that were previously reported to be depression-associated miRNAs (let-7a-5p, miR-17-5p, miR-26b-5p, miR-34a-5p, miR-132-3p, miR-182-5p, miR-212-3p, and miR-1202) were measured using real-time PCR. Two of the eight miRNAs (miR-17-5p and miR-26b-5p) were stably detected. The relative expression levels of miR-17-5p showed a significant positive correlation with PHQ-9 scores (r = 0.85, p < 0.01), while those of miR-26b-5p showed no significance. Although a larger-scale analysis is needed due to the small number of subjects, these findings suggest that miR-17-5p in NEVs is a potential biomarker for StD.

Emerging role of microRNAs in major depressive disorder and its implication on diagnosis and therapeutic response

BACKGROUND

Major depressive disorder (MDD) is a serious and common psychiatric disorder with a high prevalence in the population. Although great advances have been made, its pathogenesis is still unclear and a validated biomarker for diagnosis or therapeutic response remains unidentified. This review aims at summarizing the functional role of miRNAs in MDD pathogenesis and their potential as biomarkers for MDD diagnosis and antidepressant response.

METHODS

We performed a bibliographic research on the main databases (PubMed, Google Scholar and Web of Science) using the terms "microRNAs", "major depressive disorder", "synaptic plasticity", "biomarker", "antidepressant treatment", in order to find studies that propose the role of microRNAs in MDD pathogenesis and their potential as biomarkers for MDD diagnosis and antidepressant response.

RESULTS

microRNAs (miRNAs), a class of small noncoding RNAs, act as key regulators of synaptic plasticity in MDD pathogenesis. Growing researches provide the evidence for peripheral miRNAs as potential biomarkers for MDD diagnosis and antidepressant response. These results suggest that targeting miRNAs directly could be therapeutically beneficial for MDD and miRNAs are potential biomarkers of MDD and its treatment.

LIMITATIONS

The role of miRNAs in MDD pathogenesis needs further investigation. Whether miRNAs in peripheral tissues truly represent brain-derived miRNAs is still unclear at the present time. Moreover, only a few blood miRNAs alterations are consistent across studies.

CONCLUSIONS

Overall, miRNAs act key regulators of synaptic plasticity in MDD pathogenesis and hold significant promise as biomarkers or therapeutic targets for MDD, but further research is still needed.

Potential clinical value of circular RNAs as peripheral biomarkers for the diagnosis and treatment of major depressive disorder

Background

circular RNAs (circRNAs) are expressed abundantly in the brain and are implicated in the pathophysiology of neuropsychiatric disease. However, the potential clinical value of circRNAs in major depressive disorder (MDD) remains unclear.

Methods

RNA sequencing was conducted in whole-blood samples in a discovery set (7 highly homogeneous MDD patients and 7 matched healthy controls [HCs]). The differential expression of circRNAs was verified in an independent validation set. The interventional study was conducted to assess the potential effect of the antidepressive treatment on the circRNA expression.

Findings

in the validation set, compared with 52 HCs, significantly decreased circFKBP8 levels (Diff: -0.24; [95% CI -0.39 ~ -0.09]) and significantly elevated circMBNL1 levels (Diff: 0.37; [95% CI 0.09 ~ 0.64]) were observed in 53 MDD patients. The expression of circMBNL1 was negatively correlated with 24-item Hamilton Depression Scale (HAMD-24) scores in 53 MDD patients. A mediation model indicated that circMBNL1 affected HAMD-24 scores through a mediator, serum brain-derived neurotrophic factor. In 53 MDD patients, the amplitude of low-frequency fluctuations in the right orbital part middle frontal gyrus was positively correlated with circFKBP8 and circMBNL1 expression. Furthermore, the interventional study of 53 MDD patients demonstrated that antidepressive treatment partly increased circFKBP8 expression and the change in expression of circFKBP8 was predictive of further reduced HAMD-24 scores.

Interpretation

whole-blood circFKBP8 and circMBNL1 may be potential biomarkers for the diagnosis of MDD, respectively, and circFKBP8 may show great potential for the antidepressive treatment.

Periodontal Pathogens and Neuropsychiatric Health

Increasing evidence incriminates low-grade inflammation in cardiovascular, metabolic diseases, and neuropsychiatric clinical conditions, all important causes of morbidity and mortality. One of the upstream and modifiable precipitants and perpetrators of inflammation is chronic periodontitis, a polymicrobial infection with Porphyromonas gingivalis (P. gingivalis) playing a central role in the disease pathogenesis. We review the association between P. gingivalis and cardiovascular, metabolic, and neuropsychiatric illness, and the molecular mechanisms potentially implicated in immune upregulation as well as downregulation induced by the pathogen. In addition to inflammation, translocation of the pathogens to the coronary and peripheral arteries, including brain vasculature, and gut and liver vasculature has important pathophysiological consequences. Distant effects via translocation rely on virulence factors of P. gingivalis such as gingipains, on its synergistic interactions with other pathogens, and on its capability to manipulate the immune system via several mechanisms, including its capacity to induce production of immune-downregulating micro-RNAs. Possible targets for intervention and drug development to manage distal consequences of infection with P. gingivalis are also reviewed.

Fluoxetine ameliorates depressive symptoms by regulating lncRNA expression in the mouse hippocampus

Depression is a prevalent mental disorder that is associated with aging and contributes to increased mortality and morbidity. The overall prevalence of geriatric depression with clinically significant symptoms is currently on the rise. Recent studies have demonstrated that altered expressions of long non-coding RNAs (lncRNAs) in the brain affect neurodevelopment and manifest modulating functions during the depression. However, most lncRNAs have not yet been studied. Herein, we analyzed the transcriptome of dysregulated lncRNAs to reveal their expressions in a mouse model exhibiting depressive-like behaviors, as well as their corresponding response following antidepressant fluoxetine treatment. A chronic unpredictable mild stress (CUMS) mouse model was applied. A six-week fluoxetine intervention in CUMS-induced mice attenuated depressive-like behaviors. In addition, differential expression analysis of lncRNAs was performed following RNA-sequencing. A total of 282 lncRNAs (134 up-regulated and 148 down-regulated) were differentially expressed in CUMS-induced mice relative to non-stressed counterparts ( P<0.05). Moreover, 370 differentially expressed lncRNAs were identified in CUMS-induced mice after fluoxetine intervention. Gene Ontology (GO) analyses showed an association between significantly dysregulated lncRNAs and protein binding, oxygen binding, and transport activity, while the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that these dysregulated lncRNAs might be involved in inflammatory response pathways. Fluoxetine effectively ameliorated the symptoms of depression in CUMS-induced mice by regulating the expression of lncRNAs in the hippocampus. The findings herein provide valuable insights into the potential mechanism underlying depression in elderly people.

Neuronal Development-Related miRNAs as Biomarkers for Alzheimer's Disease, Depression, Schizophrenia and Ionizing Radiation Exposure

Radiation exposure may induce Alzheimer's disease (AD), depression or schizophrenia. A number of experimental and clinical studies suggest the involvement of miRNA in the development of these diseases, and also in the neuropathological changes after brain radiation exposure. The current literature review indicated the involvement of 65 miRNAs in neuronal development in the brain. In the brain tissue, blood, or cerebral spinal fluid (CSF), 11, 55, or 28 miRNAs are involved in the development of AD respectively, 89, 50, 19 miRNAs in depression, and 102, 35, 8 miRNAs in schizophrenia. We compared miRNAs regulating neuronal development to those involved in the genesis of AD, depression and schizophrenia and also those driving radiation-induced brain neuropathological changes by reviewing the available data. We found that 3, 11, or 8 neuronal developmentrelated miRNAs from the brain tissue, 13, 16 or 14 miRNAs from the blood of patient with AD, depression and schizophrenia respectively were also involved in radiation-induced brain pathological changes, suggesting a possibly specific involvement of these miRNAs in radiation-induced development of AD, depression and schizophrenia respectively. On the other hand, we noted that radiationinduced changes of two miRNAs, i.e., miR-132, miR-29 in the brain tissue, three miRNAs, i.e., miR- 29c-5p, miR-106b-5p, miR-34a-5p in the blood were also involved in the development of AD, depression and schizophrenia, thereby suggesting that these miRNAs may be involved in the common brain neuropathological changes, such as impairment of neurogenesis and reduced learning memory ability observed in these three diseases and also after radiation exposure.

Increased Expression of Plasma miRNA-320a and let-7b-5p in Heroin-Dependent Patients and Its Clinical Significance

Heroin use disorder is a chronic and relapsing disease that induces persistent changes in the brain. The diagnoses of heroin use disorders are mainly based on subjective reports and no valid biomarkers available. Recent researches have revealed that circulating miRNAs are useful non-invasive biomarkers for diagnosing brain diseases such as Alzheimer's disease, multiple sclerosis, schizophrenia, and bipolar disorder. However, studies on circulating miRNAs for the diagnosis of heroin use disorders are rarely reported. In this study, we investigated the differential expression of plasma miRNAs in 57 heroin-dependent patients. Based on literature research and microarray analysis, two candidate miRNAs, miR-320a and let-7b-5p, were selected and analyzed by quantitative real-time RT-PCR. The results showed miR-320a and let-7b were significantly upregulated in plasma of the heroin-dependent patients compared to that in healthy controls. The area under curves (AUCs) of receiver operating characteristic (ROC) curves of miR-320a and let-7b-5p were 0.748 and 0.758, respectively. The sensitivities of miR-320a and let-7b-5p were 71.9 and 70.2%, while the specificities of miR-320a and let-7b-5p were 76.1 and 78.3%, respectively. The combination of these two miRNAs predicted heron dependence with an AUC of 0.782 (95% CI 0.687-0.876), with 73.7% sensitivity and 82.6% specificity. Our findings suggest a potential use for circulating miRNAs as biomarkers for the diagnosis of heroin abuse.

Cell-free nucleic acid patterns in disease prediction and monitoring-hype or hope?

Interest in the use of cell-free nucleic acids (CFNAs) as clinical non-invasive biomarker panels for prediction and prevention of multiple diseases has greatly increased over the last decade. Indeed, circulating CFNAs are attributable to many physiological and pathological processes such as imbalanced stress conditions, physical activities, extensive apoptosis of different origin, systemic hypoxic-ischemic events and tumour progression, amongst others. This article highlights the involvement of circulating CFNAs in local and systemic processes dealing with the question, whether specific patterns of CFNAs in blood, their detection, quantity and quality (such as their methylation status) might be instrumental to predict a disease development/progression and could be further utilised for accompanying diagnostics, targeted prevention, creation of individualised therapy algorithms, therapy monitoring and prognosis. Presented considerations conform with principles of 3P medicine and serve for improving individual outcomes and cost efficacy of medical services provided to the population.

A Pilot Longitudinal Evaluation of MicroRNAs for Monitoring the Cognitive Impairment in Pediatric Multiple Sclerosis

MicroRNAs (miRNAs), a class of non-coding RNAs, seem to play a key role in complex diseases like multiple sclerosis (MS), as well as in many cognitive functions associated with the disease. In a previous cross-sectional evaluation on pediatric MS (PedMS) patients, the expression of some miRNAs and their target genes were found to be associated with the scores of some neuropsychiatric tests, thus suggesting that they may be involved in early processes of cognitive impairment. To verify these data, we asked the same patients to be re-evaluated after a 1-year interval; unfortunately, only nine of them agreed to this further clinical and molecular analysis. The main results showed that 13 differentially expressed miRNAs discriminated the two time-points. Among them, the expression of miR-182-5p, miR-320a-3p, miR-744-5p and miR-192-5p significantly correlated with the attention and information processing speed performances, whereas the expression of miR-182-5p, miR-451a, miR-4742-3p and miR-320a-3p correlated with the expressive language performances. The analysis of mRNA expression uncovered 58 predicted and/or validated miRNA-target pairs, including 23 target genes, some of them already associated with cognitive impairment, such as the transducing beta like 1 X-linked receptor-1 gene (TBL1XR1), correlated to disorders of neurodevelopment; the Snf2 related CREBBP activator protein gene (SRCAP) that was found implicated in a rare form of dementia; and the glia maturation factor beta gene (GMFB), which has been reported to be implicated in neurodegeneration and neuroinflammation. No molecular pathways involving the most targeted genes survived the adjustment for multiple data. Although preliminary, these findings showed the feasibility of the methods also applied to longitudinal investigations, as well as the reliability of the obtained results. These findings should be confirmed in larger PedMS cohorts in order to identify early markers of cognitive impairment, towards which more efficient therapeutic efforts can be addressed.

Changes in Non-Coding RNA in Depression and Bipolar Disorder: Can They Be Used as Diagnostic or Theranostic Biomarkers?

The similarities between the depressive symptoms of Major Depressive Disorders (MDD) and Bipolar Disorders (BD) suggest these disorders have some commonality in their molecular pathophysiologies, which is not apparent from the risk genes shared between MDD and BD. This is significant, given the growing literature suggesting that changes in non-coding RNA may be important in both MDD and BD, because they are causing dysfunctions in the control of biochemical pathways that are affected in both disorders. Therefore, understanding the changes in non-coding RNA in MDD and BD will lead to a better understanding of how and why these disorders develop. Furthermore, as a significant number of individuals suffering with MDD and BD do not respond to medication, identifying non-coding RNA that are altered by the drugs used to treat these disorders offer the potential to identify biomarkers that could predict medication response. Such biomarkers offer the potential to quickly identify patients who are unlikely to respond to traditional medications so clinicians can refocus treatment strategies to ensure more effective outcomes for the patient. This review will focus on the evidence supporting the involvement of non-coding RNA in MDD and BD and their potential use as biomarkers for treatment response.

miR-409 and miR-411 Modulation in the Adult Brain of a Rat Model of Depression and After Fluoxetine Treatment

Depression is a chronic debilitating disorder predicted to affect around 20% of the world population. Both brain and peripheral changes, including neuroplastic changes have been shown to occur in the brains of depressed individuals and animal models of depression. Over the past few decades, growing evidence has supported the role of miRNAs as regulators of critical aspects of brain plasticity and function, namely in the context of depression. These molecules are not only highly expressed in the brain, but are also relatively stable in bodily fluids, including blood. Previous microarray analysis from our group has disclosed molecular players in the hippocampal dentate gyrus (DG), in the context of depression and antidepressant treatment. Two miRNAs in particular-miR-409-5p and miR-411-5p-were significantly up-regulated in the DG of an unpredictable chronic mild stress (CMS) rat model of depression and reversed by antidepressant treatment. Here, we further analyzed the levels of these miRNAs along the DG longitudinal axis and in other brain regions involved in the pathophysiology of depression, as well as in peripheral blood of CMS-exposed rats and after fluoxetine treatment. The effects of CMS and fluoxetine treatment on miR-409-5p and miR-411-5p levels varied across brain regions, and miR-411-5p was significantly decreased in the blood of fluoxetine-treated rats. Additional bioinformatic analyses revealed target genes and pathways of these miRNAs related to neurotransmitter signaling and neuroplasticity functions; an implication of the two miRNAs in the regulation of the cellular and molecular changes observed in these brain regions in depression is worth further examination.

MicroRNA dysregulation in manic and euthymic patients with bipolar disorder

BACKGROUND

Bipolar disorder (BPD) is a major psychiatric disorder with an unclear pathophysiology. Peripheral blood samples are easily drawn, making them are good candidates for diagnosing diseases. MicroRNAs are small non-coding RNA transcripts that regulate gene expression by binding to the 3'- UTR of mRNAs and directing their degradation. The aim of this study was to use blood plasma to investigate microRNA dysregulations in bipolar manic and euthymic patients.

SUBJECTS AND METHODS

Blood samples were collected from 58 patients with bipolar I disorder (19 manic, 39 euthymic) and 51 healthy controls.

RESULTS

Four microRNAs (miR-29a-3p, p = 0.035; miR-106b-5p, p = 0.014; miR-107, p = 0.011; and miR-125a-3p, p = 0.014) were upregulated in the entire bipolar group, compared to the healthy controls. Seven microRNAs (miR-9-5p, p = 0.032; miR-29a-3p, p = 0.001; miR-106a-5p, p = 0.034; miR-106b-5p, p = 0.003; miR-107, p < 0.001; miR-125a-3p, p = 0.016; and miR-125b-5p, p = 0.004) were more upregulated in bipolar manic patients compared to the healthy controls, and two microRNAs (miR-106a-5p, p = 0.013, and miR-107, p = 0.021) showed statistically significant upregulation in the manic patients compared to the euthymic patients.

CONCLUSIONS

Our results showed greater miRNA dysregulation in the manic patients than in the euthymic patients. Two microRNAs could be more selective for bipolar manic episodes. Future studies should include depressive patients along with euthymic and manic patients.

MicroRNA-Based Biomarkers in the Diagnosis and Monitoring of Therapeutic Response in Patients with Depression

Depression is a debilitating mental illness that affects up to 120 million people worldwide; it is currently determined based on subjective diagnostic schemes that are limited by high uncertainty. Hence, there is an urgent need to identify effective and reliable biomarkers to increase diagnostic accuracy. MicroRNAs (miRNAs) constitute a recently discovered class of non-coding RNAs that play a key role in the regulation of gene expression by modulating translation, messenger RNA (mRNA) degradation, or stability of mRNA targets. Dysregulated expression of miRNAs is being investigated as a clinical biomarker for a variety of diseases, including depression. Accumulating evidence has shown that miRNAs participate in many aspects of neural plasticity, neurogenesis, and the stress response. This is supported by more direct studies based on human postmortem brain tissue that strongly indicate that miRNAs not only play a key role in the pathogenesis of major depressive disorder, but also present potential for the development of therapeutic targets. miRNAs in the peripheral and central nervous system are being considered as potential biomarkers in the diagnosis of depression and in monitoring the therapeutic response to antidepressants, owing to their stability, tissue-specificity, and disease-specific expression. In this review, we focus on various miRNAs in tissues and fluids that could be employed as diagnostic and therapeutic biomarkers in patients with depression.

Whole Genome Expression Analyses of miRNAs and mRNAs Suggest the Involvement of miR-320a and miR-155-3p and their Targeted Genes in Lithium Response in Bipolar Disorder

Lithium is the mainstay in the maintenance of bipolar disorder (BD) and the most efficacious pharmacological treatment in suicide prevention. Nevertheless, its use is hampered by a high interindividual variability and important side effects. Genetic and epigenetic factors have been suggested to modulate lithium response, but findings so far have not allowed identifying molecular targets with predictive value. In this study we used next generation sequencing to measure genome-wide miRNA expression in lymphoblastoid cell lines from BD patients excellent responders (ER, n = 12) and non-responders (NR, n = 12) to lithium. These data were integrated with microarray genome-wide expression data to identify pairs of miRNA/mRNA inversely and significantly correlated. Significant pairs were prioritized based on strength of association and in-silico miRNA target prediction analyses to select candidates for validation with qRT-PCR. Thirty-one miRNAs were differentially expressed in ER vs. NR and inversely correlated with 418 genes differentially expressed between the two groups. A total of 331 of these correlations were also predicted by in-silico algorithms. miR-320a and miR-155-3p, as well as three of their targeted genes (CAPNS1 (Calpain Small Subunit 1) and RGS16 (Regulator of G Protein Signaling 16) for miR-320, SP4 (Sp4 Transcription Factor) for miR-155-3p) were validated. These miRNAs and mRNAs were previously implicated in psychiatric disorders (miR-320a and SP4), key processes of the central nervous system (CAPNS1, RGS16, SP4) or pathways involved in mental illnesses (miR-155-3p). Using an integrated approach, we identified miRNAs and their targeted genes potentially involved in lithium response in BD.