Association ofBDNFGene Polymorphism with Bipolar Disorders in Han Chinese Population

Associations of BDNF/BDNF-AS SNPs with Depression, Schizophrenia, and Bipolar Disorder

Brain-Derived Neurotrophic Factor (BDNF) is crucial for various aspects of neuronal development and function, including synaptic plasticity, neurotransmitter release, and supporting neuronal differentiation, growth, and survival. It is involved in the formation and preservation of dopaminergic, serotonergic, GABAergic, and cholinergic neurons, facilitating efficient stimulus transmission within the synaptic system and contributing to learning, memory, and overall cognition. Furthermore, BDNF demonstrates involvement in neuroinflammation and showcases neuroprotective effects. In contrast, BDNF antisense RNA (BDNF-AS) is linked to the regulation and control of BDNF, facilitating its suppression and contributing to neurotoxicity, apoptosis, and decreased cell viability. This review article aims to comprehensively overview the significance of single nucleotide polymorphisms (SNPs) in BDNF/BDNF-AS genes within psychiatric conditions, with a specific focus on their associations with depression, schizophrenia, and bipolar disorder. The independent influence of each BDNF/BDNF-AS gene variation, as well as the interplay between SNPs and their linkage disequilibrium, environmental factors, including early-life experiences, and interactions with other genes, lead to alterations in brain architecture and function, shaping vulnerability to mental health disorders. The potential translational applications of BDNF/BDNF-AS polymorphism knowledge can revolutionize personalized medicine, predict disease susceptibility, treatment outcomes, and guide the selection of interventions tailored to individual patients.

Efficacy and tolerability of therapies set under pharmacogenetic tools suggestions: A systematic review with meta-analysis about mood disorders

BACKGROUND

Bipolar Disorder (BD) and Major Depressive Disorder (MDD) have a huge impact on functioning and quality of life; moreover, they are linked to extensive direct and indirect costs. This systematic review with meta-analysis aims to evaluate the utility of pharmacogenetic tests (PGT) in terms of efficacy and tolerability into the routine clinical treatment of mood disorders.

MATERIALS AND METHODS

The first part of the review is a qualitative overview of the PGTs used in the included studies. The second part aims to compare, in terms of efficacy and tolerability, patients affected by BD and MDD treated as usual (TAU), according to the clinicians' prescribing attitude, versus patients whose psychopharmacological treatments were set up following the PGT suggestions.

RESULTS

6 studies on MDD and 2 studies on BD were included. Regarding MDD, the meta-analysis shows a significantly higher number of patients achieving better outcome in terms of efficacy, through the evaluation of response rate and remission rate at the HDRS (Hamilton Depression Rating Scale) in the group of patients treated under the PGT suggestions; regarding BD the meta-analysis does not show any significant difference in terms of efficacy. In terms of adverse events, the available data suggest promising results about the utility of PGT to set more tolerated therapies.

CONCLUSIONS

Although the limited number of studies, results confirm the importance of PGT in setting up psychopharmacological therapies as a support to clinicians' choices.

Genetic and Epigenetic Markers of Lithium Response

The mood stabilizer lithium represents a cornerstone in the long term treatment of bipolar disorder (BD), although with substantial interindividual variability in clinical response. This variability appears to be modulated by genetics, which has been significantly investigated in the last two decades with some promising findings. In addition, recently, the interest in the role of epigenetics has grown significantly, since the exploration of these mechanisms might allow the elucidation of the gene-environment interactions and explanation of missing heritability. In this article, we provide an overview of the most relevant findings regarding the pharmacogenomics and pharmacoepigenomics of lithium response in BD. We describe the most replicated findings among candidate gene studies, results from genome-wide association studies (GWAS) as well as post-GWAS approaches supporting an association between high genetic load for schizophrenia, major depressive disorder or attention deficit/hyperactivity disorder and poor lithium response. Next, we describe results from studies investigating epigenetic mechanisms, such as changes in methylation or noncoding RNA levels, which play a relevant role as regulators of gene expression. Finally, we discuss challenges related to the search for the molecular determinants of lithium response and potential future research directions to pave the path towards a biomarker guided approach in lithium treatment.

Association study of BDNF Val66Met gene polymorphism with bipolar disorder and lithium treatment response in Indian population

BACKGROUND

The association of the Val66Met (rs6265) polymorphism in the brain-derived neurotrophic factor (BDNF) gene with bipolar disorder (BD) and response to lithium treatment has been suggested, though inconsistently. The considerable diversity of allele frequency across different populations contributes to this. There is no data from South Asia till date. Hence, we examined the association of this polymorphism in BD cases from India, and its association with lithium treatment response.

METHODS

BD patients (N = 301) were recruited from the clinical services of National Institute of Mental Health and Neurosciences (NIMHANS), India. Lithium treatment response for 190 BD subjects was assessed using Alda scale by NIMH life charts. Patients with total score ⩾7 were defined as lithium responders (N = 115) and patients with score <7 were defined as lithium non-responders (N = 75). Healthy controls (N = 484) with no lifetime history of neuropsychiatric illness or a family history of mental illness were recruited as control set. Genotyping was performed by TaqMan genotyping assay.

RESULTS

Genotype and allele frequency of BDNF Val66Met SNP was significantly different (χ2 = 7.78, p = 0.02) in cases compared to controls, and the Val(G) allele was more frequent (χ2 = 7.08, p = 0.008) in BD patients. However, no significant difference is noted in genotype or allele frequencies of this polymorphism between the lithium responders and non-responders.

CONCLUSIONS

The Val(G) allele of BDNF Val66Met polymorphism is associated with risk of BD in this sample, but it is not related to response to lithium.

Peripheral BDNF correlated with miRNA in BD-II patients

OBJECTIVES

We have identified the association between peripheral levels of candidate miRNAs (miR-7-5p, miR-142-3p, miR-221-5p, and miR-370-3p) for BD-II in previous study. Most of these miRNAs are associated with regulation of expression of peripheral brain derived neurotrophic factor (BDNF) levels. In order to clarify the underlying mechanism of BDNF and miRNAs in the pathogenesis of BD-II, it is of interest to investigate the relation between the peripheral levels of miR-7-5p, miR-142-3p, miR-221-5p, miR-370-3p with BDNF levels. Because the BDNF Val66Met polymorphism influence the secretion of BDNF, we further stratified the above correlations by this polymorphism.

METHODS

We have recruited 98 BD-II patients. Beside analyzing peripheral levels of miR-7-5p, miR-142-3p, miR-221-5p, miR-370-3p, and BDNF, the genetic distribution of the BDNF Val66Met polymorphism was also analyzed.

RESULTS

We found that the miR7-5p, miR221-5p, and miR370-3p significantly correlated with the BDNF levels for all patients. If stratified by the BDNF Val66Met polymorphism, the significant correlation between miR221-5p and miR370-3p with BDNF only remained in the Val/Met genotype. However, the correlation between miR7-5p and BDNF level is significant in all 3 genotypes.

CONCLUSION

Our result supported that these miRNAs may be involved in the pathomechanism of BD-II through relation with BDNF.

The Genetics of Response to and Side Effects of Lithium Treatment in Bipolar Disorder: Future Research Perspectives

Although the mood stabilizer lithium is a first-line treatment in bipolar disorder, a substantial number of patients do not benefit from it and experience side effects. No clinical tool is available for predicting lithium response or the occurrence of side effects in everyday clinical practice. Multiple genetic research efforts have been performed in this field because lithium response and side effects are considered to be multifactorial endophenotypes. Available results from linkage and segregation, candidate-gene, and genome-wide association studies indicate a role of genetic factors in determining response and side effects. For example, candidate-gene studies often report GSK3β, brain-derived neurotrophic factor, and SLC6A4 as being involved in lithium response, and the latest genome-wide association study found a genome-wide significant association of treatment response with a locus on chromosome 21 coding for two long non-coding RNAs. Although research results are promising, they are limited mainly by a lack of replicability and, despite the collaboration of consortia, insufficient sample sizes. The need for larger sample sizes and "multi-omics" approaches is apparent, and such approaches are crucial for choosing the best treatment options for patients with bipolar disorder. In this article, we delineate the mechanisms of action of lithium and summarize the results of genetic research on lithium response and side effects.

HDAC1 promotes artery injury through activation of VAV3 by binding to miR-182-5p in atherosclerotic mice model

Atherosclerosis (AS) is one of the significant chronic inflammatory pathology considering public health impact. Up-regulation of HDAC1 has been proved to be related with endothelial dysfunction which is correlated intimately with AS. Our research aims to investigate how histone deacetylase 1 (HDAC1)/miR-182-5p/vav guanine nucleotide exchange factor 3 (VAV3)/AKT axis participates in AS in terms of molecular mechanism. We detected miR-181-5p in human umbilical vein endothelial cells after treatment with aorta and ox-LDL in AS model mice. Dual luciferase reporter assay was employed to verify interaction of miR-182-5p and VAV3. ChIP was performed to determine the relationship between HDAC1 and promoter of miR-182-5p. Protein levels of HADC1, VAV3, AKT, p-AKT, vascular cell adhesion molecule-1 (VCAM-1), intercellular cell adhesion molecule-1 (ICAM-1), and monocyte chemotactic protein 1 (MCP-1) were detected by western blot analysis. CCK8 and flow cytometry were used to detect cell viability and apoptosis, respectively. After different treatments, the ability of cells to form monoclonal cells was detected, and AS was evaluated by detecting arterial injury and inflammation-related factors. Overexpression of HDAC1 could inhibit HUVECs proliferation and promote AS in mouse model. It was verified by dual luciferase assay that miR-182-5p could bind to VAV3 3'UTR mRNA. Meanwhile, HDAC1 repressed miR-182-5p expression through binding to miR-182-5p promoter and then inhibit VAV3 expression further. In summary, HDAC1 promoted AS through AKT pathway, which was improved by VAV3 activation mediated by miR-182-5p. Our results demonstrated that HDAC1 repressed miR-182-5p and activating AKT pathway via improving VAV3 to promote AS progression.

Potential pharmacogenomic targets in bipolar disorder: considerations for current testing and the development of decision support tools to individualize treatment selection

Background

Treatment in bipolar disorder (BD) is commonly applied as a multimodal therapy based on decision algorithms that lack an integrative understanding of molecular mechanisms or a biomarker associated clinical outcome measure. Pharmacogenetics/genomics study the individual genetic variation associated with drug response. This selective review of pharmacogenomics and pharmacogenomic testing (PGT) in BD will focus on candidate genes and genome wide association studies of pharmacokinetic drug metabolism and pharmacodynamic drug response/adverse event, and the potential role of decision support tools that incorporate multiple genotype/phenotype drug recommendations.

Main body

We searched PubMed from January 2013 to May 2019, to identify studies reporting on BD and pharmacogenetics, pharmacogenomics and PGT. Studies were selected considering their contribution to the field. We summarize our findings in: targeted candidate genes of pharmacokinetic and pharmacodynamic pathways, genome-wide association studies and, PGT platforms, related to BD treatment. This field has grown from studies of metabolizing enzymes (i.e., pharmacokinetics) and drug transporters (i.e., pharmacodynamics), to untargeted investigations across the entire genome with the potential to merge genomic data with additional biological information.

Conclusions

The complexity of BD genetics and, the heterogeneity in BD drug-related phenotypes, are important considerations for the design and interpretation of BD PGT. The clinical applicability of PGT in psychiatry is in its infancy and is far from reaching the robust impact it has in other medical disciplines. Nonetheless, promising findings are discovered with increasing frequency with remarkable relevance in neuroscience, pharmacology and biology.

Innovations and changes in the ICD-11 classification of mental, behavioural and neurodevelopmental disorders

Following approval of the ICD-11 by the World Health Assembly in May 2019, World Health Organization (WHO) member states will transition from the ICD-10 to the ICD-11, with reporting of health statistics based on the new system to begin on January 1, 2022. The WHO Department of Mental Health and Substance Abuse will publish Clinical Descriptions and Diagnostic Guidelines (CDDG) for ICD-11 Mental, Behavioural and Neurodevelopmental Disorders following ICD-11's approval. The development of the ICD-11 CDDG over the past decade, based on the principles of clinical utility and global applicability, has been the most broadly international, multilingual, multidisciplinary and participative revision process ever implemented for a classification of mental disorders. Innovations in the ICD-11 include the provision of consistent and systematically characterized information, the adoption of a lifespan approach, and culture-related guidance for each disorder. Dimensional approaches have been incorporated into the classification, particularly for personality disorders and primary psychotic disorders, in ways that are consistent with current evidence, are more compatible with recovery-based approaches, eliminate artificial comorbidity, and more effectively capture changes over time. Here we describe major changes to the structure of the ICD-11 classification of mental disorders as compared to the ICD-10, and the development of two new ICD-11 chapters relevant to mental health practice. We illustrate a set of new categories that have been added to the ICD-11 and present the rationale for their inclusion. Finally, we provide a description of the important changes that have been made in each ICD-11 disorder grouping. This information is intended to be useful for both clinicians and researchers in orienting themselves to the ICD-11 and in preparing for implementation in their own professional contexts.

The Role of Pharmacogenomics in Bipolar Disorder: Moving Towards Precision Medicine

Bipolar disorder (BD) is a common and disabling psychiatric condition with a severe socioeconomic impact. BD is treated with mood stabilizers, among which lithium represents the first-line treatment. Lithium alone or in combination is effective in 60% of chronically treated patients, but response remains heterogenous and a large number of patients require a change in therapy after several weeks or months. Many studies have so far tried to identify molecular and genetic markers that could help us to predict response to mood stabilizers or the risk for adverse drug reactions. Pharmacogenetic studies in BD have been for the most part focused on lithium, but the complexity and variability of the response phenotype, together with the unclear mechanism of action of lithium, limited the power of these studies to identify robust biomarkers. Recent pharmacogenomic studies on lithium response have provided promising findings, suggesting that the integration of genome-wide investigations with deep phenotyping, in silico analyses and machine learning could lead us closer to personalized treatments for BD. Nevertheless, to date none of the genes suggested by pharmacogenetic studies on mood stabilizers have been included in any of the genetic tests approved by the Food and Drug Administration (FDA) for drug efficacy. On the other hand, genetic information has been included in drug labels to test for the safety of carbamazepine and valproate. In this review, we will outline available studies investigating the pharmacogenetics and pharmacogenomics of lithium and other mood stabilizers, with a specific focus on the limitations of these studies and potential strategies to overcome them. We will also discuss FDA-approved pharmacogenetic tests for treatments commonly used in the management of BD.

Memory Impairment and Plasma BDNF Correlates of the BDNF Val66Met Polymorphism in Patients With Bipolar II Disorder

Studies suggest that a functional polymorphism of brain-derived neurotrophic factor (BDNF), polymorphism BDNF Val⁶⁶Met affects cognitive functions, however, the effect is unclear in bipolar II (BD-II) disorder. We used the Wechsler Memory Scale-third edition (WMS-III), the presence of the BDNF Val⁶⁶Met polymorphism, and plasma concentrations of BDNF to investigate the association between memory impairment and BDNF in BD-II disorder. We assessed the memory functions of 228 BD-II patients and 135 healthy controls (HCs). BD-II patients had significantly lower scores on five of the eight WMS-III subscales. In addition to education, the BDNF polymorphism were associated with the following subscales of WMS-III, auditory delayed memory, auditory delayed recognition memory and general memory scores in BD-II patients, but not in HC. Moreover, BD-II patients with the Val-homozygote scored significantly higher on the visual immediate memory subscale than did those with the Met/Met and Val/Met polymorphisms. The significantly positive effect of the Val-homozygote did not have a significantly positive effect on memory in the HC group, however. We found no significant association between BDNF polymorphisms and plasma concentrations of BDNF. The plasma BDNF was more likely to be associated with clinical characteristics than it was with memory indices in the BD-II group. The impaired memory function in BD-II patients might be dependent upon the association between the BDNF Val⁶⁶Met polymorphism and peripheral BDNF levels.

Pharmacogenomic aspects of bipolar disorder: An update

The hopes for readily implementable precision medicine are high. For many complex disorders, such as bipolar disorder, these hopes critically hinge on tangible successes in pharmacogenetics of treatment response or susceptibility to adverse events. In this article, we review the current state of pharmacogenomics of bipolar disorder including latest results from candidate genes and genome-wide association studies. The majority of studies focus on response to lithium treatment. Although a host of genes has been studied, hardly any replicated findings have emerged so far. Very small samples sizes and heterogeneous phenotype definition may be considered the major impediments to success in this field. Drawing from current experiences and successes in studies on diagnostic psychiatric phenotypes, we suggest several approaches for our way forward.

The correlation between plasma brain-derived neurotrophic factor and cognitive function in bipolar disorder is modulated by the BDNF Val66Met polymorphism

We explored the effect of the Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism (rs6265) on correlation between changes in plasma BDNF levels with cognitive function and quality of life (QoL) after 12 weeks of treatment in bipolar disorder (BD). Symptom severity and plasma BDNF levels were assessed upon recruitment and during weeks 1, 2, 4, 8 and 12. QoL, the Wisconsin Card Sorting Test (WCST), and the Conners’ Continuous Performance Test (CPT) were assessed at baseline and endpoint. The BDNF Val66Met polymorphism was genotyped. Changes in cognitive function and QoL over 12 weeks were reduced using factor analysis for the evaluation of their correlations with changes in plasma BDNF. Five hundred forty-one BD patients were recruited and 65.6% of them completed the 12-week follow-up. Changes in plasma BDNF levels with factor 1 (WCST) were significantly negatively correlated (r = −0.25, p = 0.00037). After stratification of BD subtypes and BDNF genotypes, this correlation was significant only in BP-I and the Val/Met genotype (r = −0.54, p = 0.008). We concluded that changes in plasma BDNF levels significantly correlated with changes in WCST scores in BD and is moderated by the BDNF Val66Met polymorphism and the subtype of BD.

Association of BDNF Polymorphisms with the Risk of Epilepsy: a Multicenter Study

Epilepsy is a common neurological disease characterized by recurrent unprovoked seizures. Evidence suggested that abnormal activity of brain-derived neurotrophic factor (BDNF) contributes to the pathogenesis of epilepsy. Some previous studies identified association between genetic variants of BDNF and risk of epilepsy. In this study, this association has been examined in the Hong Kong and Malaysian epilepsy cohorts. Genomic DNA of 6047 subjects (1640 patients with epilepsy and 4407 healthy individuals) was genotyped for rs6265, rs11030104, rs7103411, and rs7127507 polymorphisms by using Sequenom MassArray and Illumina HumanHap 610-Quad or 550-Duo BeadChip arrays techniques. Results showed significant association between rs6265 T, rs7103411 C, and rs7127507 T and cryptgenic epilepsy risk (p = 0.00003, p = 0.0002, and p = 0.002, respectively) or between rs6265 and rs7103411 and symptomatic epilepsy risk in Malaysian Indians (TT vs. CC, p = 0.004 and T vs. C, p = 0.0002, respectively) as well as between rs6265 T and risk of cryptogenic epilepsy in Malaysian Chinese (p = 0.005). The Trs6265-Crs7103411-Trs7127507 was significantly associated with cryptogenic epilepsy in Malaysian Indians (p = 0.00005). In conclusion, our results suggest that BDNF polymorphisms might contribute to the risk of epilepsy in Malaysian Indians and Chinese.

Toward stratified treatments for bipolar disorders

In bipolar disorders, there are unclear diagnostic boundaries with unipolar depression and schizophrenia, inconsistency of treatment guidelines, relatively long trial-and-error phases of treatment optimization, and increasing use of complex combination therapies lacking empirical evidence. These suggest that the current definition of bipolar disorders based on clinical symptoms reflects a clinically and etiologically heterogeneous entity. Stratification of treatments for bipolar disorders based on biomarkers and improved clinical markers are greatly needed to increase the efficacy of currently available treatments and improve the chances of developing novel therapeutic approaches. This review provides a theoretical framework to identify biomarkers and summarizes the most promising markers for stratification regarding beneficial and adverse treatment effects. State and stage specifiers, neuropsychological tests, neuroimaging, and genetic and epigenetic biomarkers will be discussed with respect to their ability to predict the response to specific pharmacological and psychosocial psychotherapies for bipolar disorders. To date, the most reliable markers are derived from psychopathology and history-taking, while no biomarker has been found that reliably predicts individual treatment responses. This review underlines both the importance of clinical diagnostic skills and the need for biological research to identify markers that will allow the targeting of treatment specifically to sub-populations of bipolar patients who are more likely to benefit from a specific treatment and less likely to develop adverse reactions.

The role of brain-derived neurotrophic factor (BDNF) Val66Met genetic polymorphism in bipolar disorder: a case-control study, comorbidities, and meta-analysis of 16,786 subjects

OBJECTIVES

The aim of this study was to evaluate the association of Val66Met brain-derived neurotrophic factor (BDNF) polymorphism with bipolar disorder in (i) a meta-analysis and (ii) a case-control study in a Mexican population. We also investigated the possible association of this polymorphism with clinical features.

METHODS

We performed a keyword search of the PubMed and Web of Science databases. A total of 22 studies that have investigated the association of Val66Met (rs6265) with bipolar disorder were selected for inclusion and combined with random effects meta-analysis, using allelic, additive, dominant, and recessive models. Finally, the single nucleotide polymorphism (rs6265) Val66Met in the BDNF gene was genotyped and compared between 139 patients with bipolar disorder and 141 healthy volunteers in a Mexican population.

RESULTS

The pooled results from the meta-analysis (9,349 cases and 7,437 controls) did not show a significant association in any of the models. The same results were obtained in our case-control study when analyzing the distribution of the genotypic frequencies of the Val66Met polymorphism in patients with bipolar disorder. However, when we analyzed the association between rs6265 and lifetime history of suicidal behavior, we found an association between genotype Val-Val and suicide attempt (p = 0.02).

CONCLUSIONS

Although the present study has some limitations, the results indicate a lack of association between the Val66Met polymorphism and bipolar disorder. However, in our case-control study in a Mexican population, the Val66Met polymorphism was associated with suicidal behavior in patients with bipolar disorder. Nevertheless, it is important to consider potential interactions of the BDNF gene, the environment, and different inheritance patterns, when carrying out future genetic studies with larger samples.

Association between brain-derived neurotrophic factor genetic polymorphism Val66Met and susceptibility to bipolar disorder: a meta-analysis

BACKGROUND

In view of previous conflicting findings, this meta-analysis was performed to comprehensively determine the overall strength of associations between brain-derived neurotrophic factor (BDNF) genetic polymorphism Val66Met and susceptibility to bipolar disorders (BPD).

METHODS

Literatures published and cited in Pubmed and Wanfang Data was searched with terms of 'Val66Met', 'G196A', 'rs6265', 'BDNF', 'association', and 'bipolar disorder' up to March 2014. All original case-control association studies were meta-analyzed with a pooled OR to estimate the risk and 95% confidence interval (CI) to reflect the magnitude of variance.

RESULTS

Twenty-one case-control association studies met our criteria for the meta-analysis. Overall, there was no significant difference in allelic distribution of Val66Met polymorphism between patients and controls with a pooled OR = 1.03 (95% CI 0.98, 1.08) although there was a trend towards association between Val66Met polymorphism and BPD in Caucasians with an OR of 1.08 (95% CI 1.00, 1.16). However, subgroup analyses showed that there was a significant association of Val allele with decreased disease susceptibility for bipolar disorder type II with a pooled OR of 0.88 (95% CI 0.78, 0.99).

CONCLUSIONS

There is no compelling evidence to supportVal66Met polymorphism in BDNF gene playing an important role in the susceptibility to BPD across different ethnicities.

Identification of ANKK1 rs1800497 variant in schizophrenia: new data and meta-analysis

One functional polymorphism (rs1800497) within the ankyrin repeat and kinase domain containing-1 gene (ANKK1) was reported to be associated with schizophrenia, but results among different studies vary and conclusions remain controversial. The present study sought to clarify this potential association among a population of Han Chinese with early onset schizophrenia using a case-control (396 patients and 399 controls) and family based study (103 trios). We then performed a meta-analysis (comprising 11 case-control and 2 family-based studies) based on the present literature. Results of the association study revealed no significant difference in allele and genotype frequencies between the cases and controls, and no significant transmission distortion was detected. Kaplan-Meier survival analysis showed that age at onset in schizophrenia was significantly associated with the rs1800497 polymorphism in female patients, but not in males. Female T allele carriers had a lower age at onset than those without T allele (log rank statistic χ(2) = 5.16, P = 0.023; corrected P = 0.046). Meta-analysis results indicated that rs1800497 is not associated with schizophrenia in the overall population (P = 0.77 for the case-control studies; P = 0.06 for the family-based studies). Our results support the hypothesis that rs1800497 polymorphism is likely to have a modifying rather than causative effect on schizophrenia. These findings may represent a significant genetic clue for the etiology of schizophrenia in females, but further investigation is required to clarify the exact role of ANKK1 in the development of schizophrenia.

MiRNA-206 and BDNF genes interacted in bipolar I disorder

BACKGROUND

Several lines of evidence have suggested that has-mir-206 (miRNA-206) may regulate brain-derived neurotrophic factor (BDNF) protein synthesis. The primary aim of this study was to determine whether miRNA-206 gene (MIR206) may confer susceptibility to bipolar disorder type I (BD-I) and treatment response to mood stabilizers. Also, we intended to verify the hypothesis that a potential interplay of MIR206 and BDNF may influence the genetic risk for BD-I and treatment response.

METHODS

The MIR206 rs16882131 and BDNF rs6265 polymorphisms were genotyped in 280 BD-I patients and 288 healthy controls. Treatment response to lithium and valproate was retrospectively determined.

RESULTS

No association was observed in the individual polymorphism with regards to risk of BD-I and treatment response. Our results showed a significant gene to gene interaction between the MIR206 rs16882131 and BDNF rs6265 polymorphisms that contribute to BD-I susceptibility and treatment response. Further analysis showed a significant interaction between MIR206 and BDNF on treatment score (F3, 138=8.61, P=0.046), and individuals with MIR206 T/T+TC and BDNF A/A genotypes had a significantly lower mean treatment score than those with MIR206 CC and BDNF A/A+A/G as well as those with MIR206 CC and BDNF G/G genotypes (P=0.018 and 0.013, respectively).

LIMITATION

This is a preliminary investigation with relatively small sample size.

CONCLUSION

Our findings provide initial evidence of the gene-to-gene interaction of MIR206 and BDNF in regards to the risk for BD-I as well as treatment response to mood stabilizers.

Towards the clinical implementation of pharmacogenetics in bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a psychiatric illness defined by pathological alterations between the mood states of mania and depression, causing disability, imposing healthcare costs and elevating the risk of suicide. Although effective treatments for BD exist, variability in outcomes leads to a large number of treatment failures, typically followed by a trial and error process of medication switches that can take years. Pharmacogenetic testing (PGT), by tailoring drug choice to an individual, may personalize and expedite treatment so as to identify more rapidly medications well suited to individual BD patients.

DISCUSSION

A number of associations have been made in BD between medication response phenotypes and specific genetic markers. However, to date clinical adoption of PGT has been limited, often citing questions that must be answered before it can be widely utilized. These include: What are the requirements of supporting evidence? How large is a clinically relevant effect? What degree of specificity and sensitivity are required? Does a given marker influence decision making and have clinical utility? In many cases, the answers to these questions remain unknown, and ultimately, the question of whether PGT is valid and useful must be determined empirically. Towards this aim, we have reviewed the literature and selected drug-genotype associations with the strongest evidence for utility in BD.

SUMMARY

Based upon these findings, we propose a preliminary panel for use in PGT, and a method by which the results of a PGT panel can be integrated for clinical interpretation. Finally, we argue that based on the sufficiency of accumulated evidence, PGT implementation studies are now warranted. We propose and discuss the design for a randomized clinical trial to test the use of PGT in the treatment of BD.

Genetic modulation of working memory deficits by ankyrin 3 gene in schizophrenia

Neuropsychological endophenotype approach is an emerging strategy in schizophrenia research to understand and identify the functional importance of genetically transmitted, brain-based deficits present in this disorder. Accumulating evidence indicated that working memory deficit is a core neuropsychological dysfunction in schizophrenia and a primary endophenotype indexing the liability to develop schizophrenia. Genetic variation in ankyrin 3 gene (ANK3) is likely to have widespread cognitive effects. Our previous study has identified a significant association of ANK3 SNPs and schizophrenia. In this study, we aimed to examine whether the schizophrenia-risk SNPs within ANK3 may affect working memory deficits in schizophrenia patients. Herein, we assess the working memory performance in 163 patients with first-episode, antipsychotic-naïve schizophrenia and 42 sex, age-matched healthy subjects using N-back task. Two SNPs rs10761482 and rs10994336 were genotyped among the patients and 209 controls. Our results showed that schizophrenia patients showed significantly poorer performance than healthy controls on N-back task (ps<0.01). After adjusting for the scores of intelligence quotient, memory quotient and the demographic factors, there was a significant genotype effect of the rs10994336 on the accuracy rate and reaction time of 2-back item (p=0.048 and 0.024, respectively). Post-hoc analyses showed that patients with rs10994336T/T genotype had significantly lower accuracy rate and more reaction time at 2-back task than those with T/C and C/C genotypes. The association of SNP rs10994336 with schizophrenia was replicated in our sample (genotypic p=0.024 and allelic p=0.006). However, we did not find any significant association of rs10761482 with schizophrenia and parameters in N-back task. Our results indicated that genetic variation within ANK3 may exert gene-specific modulating effects on working memory deficits in schizophrenia.

Molecular actions and clinical pharmacogenetics of lithium therapy

Mood disorders, including bipolar disorder and depression, are relatively common human diseases for which pharmacological treatment options are often not optimal. Among existing pharmacological agents and mood stabilizers used for the treatment of mood disorders, lithium has a unique clinical profile. Lithium has efficacy in the treatment of bipolar disorder generally, and in particular mania, while also being useful in the adjunct treatment of refractory depression. In addition to antimanic and adjunct antidepressant efficacy, lithium is also proven effective in the reduction of suicide and suicidal behaviors. However, only a subset of patients manifests beneficial responses to lithium therapy and the underlying genetic factors of response are not exactly known. Here we discuss preclinical research suggesting mechanisms likely to underlie lithium's therapeutic actions including direct targets inositol monophosphatase and glycogen synthase kinase-3 (GSK-3) among others, as well as indirect actions including modulation of neurotrophic and neurotransmitter systems and circadian function. We follow with a discussion of current knowledge related to the pharmacogenetic underpinnings of effective lithium therapy in patients within this context. Progress in elucidation of genetic factors that may be involved in human response to lithium pharmacology has been slow, and there is still limited conclusive evidence for the role of a particular genetic factor. However, the development of new approaches such as genome-wide association studies (GWAS), and increased use of genetic testing and improved identification of mood disorder patients sub-groups will lead to improved elucidation of relevant genetic factors in the future.

Pharmacogenomics of bipolar disorder

Bipolar disorder (BD) is a lifelong severe psychiatric condition with high morbidity, disability and excess mortality. The longitudinal clinical trajectory of BD is significantly modified by pharmacological treatment(s), both in acute and in long-term stages. However, a large proportion of BD patients have inadequate response to pharmacological treatments. Pharmacogenomic research may lead to the identification of molecular predictors of treatment response. When integrated with clinical information, pharmacogenomic findings may be used in the future to determine the probability of response/nonresponse to treatment on an individual basis. Here we present a selective review of pharmacogenomic findings in BD. In light of the evidence suggesting a genetic effect of lithium reponse in BD, we focused particularly on the pharmacogenomic literature relevant to this trait. The article contributes a detailed overview of the current status of pharmacogenomics in BD and offers a perspective on the challenges that can hinder its transition to personalized healthcare.

Influence of BCL2 gene in major depression susceptibility and antidepressant treatment outcome

BACKGROUND

Our recent work indicated that low-expression of the anti-apoptotic protein B-cell/lymphoma 2 (Bcl-2) mRNA was observed among untreated major depressive disorder (MDD) patients, and the subsequent altered level of Bcl-2 was found to be close to the antidepressant treatment outcome. The primary aim of this present study was to examine whether a particular gene, encoding Bcl-2 (BCL2) confers risk to MDD, and likewise to investigate whether this gene acts as an indicator of antidepressant treatment outcome.

METHODS

We enrolled 178 treatment-resistant depression (TRD) and 612 non-treatment-resistant depression (NTRD) patients as well as 725 healthy controls. In total, three selected tagging SNPs (tagSNPs) of BCL2 (rs2279115, rs1801018 and rs1564483) were genotyped to test for possible association. Using TaqMan relative quantitative real-time polymerase chain reaction (PCR), we analyzed leukocytic expression of BCL2 mRNA in 47 healthy subjects.

RESULTS

Of the three SNPs, we observed no significant differences in genotype and allele frequencies between the MDD and control groups as well as between the TRD and NTRD groups. However, we found a significant association between the rs2279115C allele and TRD in males (corrected P=0.048) but not in females. Further real-time quantitative PCR analysis in healthy subjects revealed that the rs2279115 polymorphism significantly influenced BCL2 mRNA expression (P=0.03).

LIMITATIONS

This is a preliminary investigation with relatively small sample size and cross-sectional design.

CONCLUSIONS

These initial findings strengthen the hypothesis that BCL2 may play an important role in mediating the outcome of antidepressant treatment, a result that may further be confirmed by future genetic studies from large-scale populations that can overcome the limited sample size of this preliminary finding.

Genotype variant associated with add-on memantine in bipolar II disorder

Memantine is a non-competitive N-methyl-d-asparate (NMDA) receptor antagonist with a mood-stabilizing effect. We investigated whether using valproic acid (VPA) plus add-on memantine to treat bipolar II disorder (BP-II) is more effective than using VPA alone (VPA + Pbo). We also evaluated, in BP-II patients, the association between the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism with treatment response to VPA + add-on memantine and to VPA + Pbo. In this randomized, double-blind, controlled 12 wk study, BP-II patients undergoing regular VPA treatments were randomly assigned to a group: VPA + Memantine (5 mg/day) (n = 115) or VPA + Pbo (n = 117). The Hamilton Depression Rating Scale (HDRS) and Young Mania Rating Scale (YMRS) were used to evaluate clinical response during week 0, 1, 2, 4, 8 and 12. The genotypes of the BDNF Val66Met polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis. To adjust within-subject dependence over repeated assessments, multiple linear regression with generalized estimating equation methods was used to analyze the effects of the BDNF Val66Met polymorphism on the clinical performance of memantine. Both groups showed significantly decreased YMRS and HDRS scores after 12 wk of treatment; the differences between groups were non-significant. When stratified by the BDNF Val66Met genotypes, significantly greater decreases in HDRS scores were found in the VPA + memantine group in patients with the Val Met genotype (p = 0.004). We conclude that the BDNF Val66Met polymorphism influenced responses to add-on memantine by decreasing depressive symptoms in patients with BP-II.

A study of N-methyl-D-aspartate receptor gene (GRIN2B) variants as predictors of treatment-resistant major depression

RATIONALE

In clinical practice, ketamine, an antagonist of the N-methyl-D-aspartate receptor (NMDAR), is used to alleviate depressive symptoms in patients with major depressive disorder (MDD), especially in those with treatment-resistant depression (TRD). Accordingly, the human gene coding for the 2B subunit of the NMDAR (GRIN2B) is considered a promising candidate gene for MDD susceptibility.

OBJECTIVES

The primary aim of this study is to examine whether potentially functional polymorphisms of GRIN2B confer risk for MDD, and second to investigate whether GRIN2B acts as a genetic predictor for TRD in MDD patients.

METHODS

We enrolled 178 TRD and 612 non-TRD patients as well as 779 healthy controls.

RESULTS

Four potentially functional polymorphisms (rs1805502, rs890, rs1806201, and rs7301328) within GRIN2B were genotyped in all participants. The haplotype analysis found significant differences in the distribution of the G-T haplotype between the TRD and control groups (corrected P = 0.007), and the frequency of the G-T haplotype in TRD group was significantly higher than that in the controls (TRD/control ratio 0.31:0.21). Statistically significant differences in allele and genotype frequencies were detected between TRD and non-TRD groups for the rs1805502 polymorphism within GRIN2B. There was a significant allelic association between rs1805502 and TRD with an excess of the G allele in the TRD group, compared to non-TRD group (OR = 1.55, 95 % CI = 1.18-2.05, corrected P = 0.008).

CONCLUSIONS

These initial findings strengthen the hypothesis that GRIN2B not only confers susceptibility to TRD, but also plays a genetic predictor for TRD in MDD patients.

Association study of common variants within the G protein-coupled receptor kinase 6 gene and schizophrenia susceptibility in Han Chinese

In this study, we examined whether common variants in the G protein-coupled receptor kinase 6 gene (GRK6) confers susceptibility to schizophrenia in Chinese. We genotyped two common variants in 697 schizophrenia patients and 563 healthy control subjects. No significant difference in either allele or genotype comparisons between the case and control groups was found. Our results imply that GRK6 may not play a role in the pathophysiology of schizophrenia among Han Chinese.

Integrated neurobiology of bipolar disorder

From a neurobiological perspective there is no such thing as bipolar disorder. Rather, it is almost certainly the case that many somewhat similar, but subtly different, pathological conditions produce a disease state that we currently diagnose as bipolarity. This heterogeneity - reflected in the lack of synergy between our current diagnostic schema and our rapidly advancing scientific understanding of the condition - limits attempts to articulate an integrated perspective on bipolar disorder. However, despite these challenges, scientific findings in recent years are beginning to offer a provisional "unified field theory" of the disease. This theory sees bipolar disorder as a suite of related neurodevelopmental conditions with interconnected functional abnormalities that often appear early in life and worsen over time. In addition to accelerated loss of volume in brain areas known to be essential for mood regulation and cognitive function, consistent findings have emerged at a cellular level, providing evidence that bipolar disorder is reliably associated with dysregulation of glial-neuronal interactions. Among these glial elements are microglia - the brain's primary immune elements, which appear to be overactive in the context of bipolarity. Multiple studies now indicate that inflammation is also increased in the periphery of the body in both the depressive and manic phases of the illness, with at least some return to normality in the euthymic state. These findings are consistent with changes in the hypothalamic-pituitary-adrenal axis, which are known to drive inflammatory activation. In summary, the very fact that no single gene, pathway, or brain abnormality is likely to ever account for the condition is itself an extremely important first step in better articulating an integrated perspective on both its ontological status and pathogenesis. Whether this perspective will translate into the discovery of innumerable more homogeneous forms of bipolarity is one of the great questions facing the field and one that is likely to have profound treatment implications, given that fact that such a discovery would greatly increase our ability to individualize - and by extension, enhance - treatment.

Lack of association of SLC1A1 variants with schizophrenia in Chinese Han population

In this study, we analyzed four single nucleotide polymorphisms (SNPs) (rs10491734, rs2228622, rs301430 and rs301443) of the solute carrier family 1 gene (SLC1A1) in a set of 616 schizophrenia patients and 638 matched healthy controls of Han Chinese descent. No significant differences of genotype or allele distribution were identified between the patients and controls. Our data suggest that SLC1A1 is unlikely to be a major susceptibility gene for schizophrenia in Han Chinese.

BDNF Val66Met polymorphism and lithium response: a meta-analysis

AIM

To characterize the impact of the Val66Met polymorphism on lithium response in patients with bipolar disorder.

METHODS

A systematic literature search of MEDLINE, Web of Science, PsychINFO and Cochrane CENTRAL was conducted from the earliest possible date through to 1 July 2012. The search was performed using the following medical subject headings: bipolar disorder, lithium, lithium carbonate, pharmacogenomics, pharmacogenetics, polymorphism and brain-derived neurotrophic factor. Five of 71 identified studies met the inclusion criteria. Data were abstracted using a standardized data abstraction tool. For categorical end points, the pooled odds ratio with 95% CI was calculated. Random effects models were used for analysis.

RESULTS

The Val66Met polymorphism did not predict response to prophylactic lithium in this combined population (odds ratio: 2.67; p = 0.078).

CONCLUSION

This analysis suggests that the Val66Met polymorphism does not predict response to lithium treatment in bipolar disorder in this combined population. Prospective studies are needed to clearly define the role of Val66Met polymorphism of BDNF in lithium response.

The interacting effect of the BDNF Val66Met polymorphism and stressful life events on adolescent depression is not an artifact of gene-environment correlation: evidence from a longitudinal twin study

BACKGROUND

Confounding introduced by gene-environment correlation (rGE) may prevent one from observing a true gene-environment interaction (G × E) effect on psychopathology. The present study investigated the interacting effect of the BDNF Val66Met polymorphism and stressful life events (SLEs) on adolescent depression while controlling for the rGE by two means: separating pure environmental factors (independent SLEs) from the environmental factors under partial genetic control (dependent SLEs) and adopting a prospective longitudinal design.

METHODS

A total of 780 pairs of Chinese twins, aged 11-17 years (mean = 13.6, SD = 1.8) at intake, were followed up twice. Self-reported depression symptoms at Time 1 and Time 2 were assessed by the Children's Depression Inventory (CDI). SLEs occurring between Time 1 and Time 2 were assessed by a self-reported checklist. SLEs were differentiated into independent and dependent ones and were validated by heritability analyses using twin design. The interacting effects between the BDNF Val66Met polymorphism and numbers of SLEs (total SLEs and independent SLEs) on intraindividual change of depression symptoms were examined.

RESULTS

After controlling for sex, age, age square, and Time 1 depression, both total SLEs × BDNF Val66Met genotype and independent SLEs × BDNF Val66Met genotype significantly predicted Time 2 depression. Val allele carriers (Val/Val and Val/Met) were more susceptible to the detrimental effects of stress.

CONCLUSIONS

There is a true G × E effect underlying the observed interaction between BDNF Val66Met polymorphism and environmental stress on depression.

The interaction of BDNF and NTRK2 gene increases the susceptibility of paranoid schizophrenia

The association between BDNF gene functional Val66Met polymorphism rs6265 and the schizophrenia is far from being consistent. In addition to the heterogeneous in schizophrenia per se leading to the inconsistent results, the interaction among multi-genes is probably playing the main role in the pathogenesis of schizophrenia, but not a single gene. Neurotrophic tyrosine kinase receptor 2 (NTRK2) is the high-affinity receptor of BDNF, and was reported to be associated with mood disorders, though no literature reported the association with schizophrenia. Thus, in the present study, total 402 patients with paranoid schizophrenia (the most common subtype of schizophrenia) and matched 406 healthy controls were recruited to investigate the role of rs6265 in BDNF, three polymorphisms in NTRK2 gene (rs1387923, rs2769605 and rs1565445) and their interaction in the susceptibility to paranoid schizophrenia in a Chinese Han population. We did not observe significant differences in allele and genotype frequencies between patients and healthy controls for all four polymorphisms separately. The haplotype analysis also showed no association between haplotype of NTRK2 genes (rs1387923, rs2769605, and rs1565445) and paranoid schizophrenia. However, we found the association between the interaction of BDNF and NTRK2 with paranoid schizophrenia by using the MDR method followed by conventional statistical analysis. The best gene-gene interaction model was a three-locus model (BDNF rs6265, NTRK2 rs1387923 and NTRK2 rs2769605), in which one low-risk and three high-risk four-locus genotype combinations were identified. Our findings implied that single polymorphism of rs6265 rs1387923, rs2769605, and rs1565445 in BDNF and NTRK2 were not associated with the development of paranoid schizophrenia in a Han population, however, the interaction of BDNF and NTRK2 genes polymorphisms (BDNF-rs6265, NTRK2-rs1387923 and NTRK2-rs2769605) may be involved in the susceptibility to paranoid schizophrenia.

Association of genetic variation in CACNA1C with bipolar disorder in Han Chinese

BACKGROUND

A growing body of evidence highlights the existence of shared genetic susceptibility to both major depressive disorder (MDD) and bipolar disorder (BD), suggesting some potential genetic overlap between the disorders. Genome-wide association studies have identified consistent association of single nucleotide polymorphisms of the α-1 C subunit of the L-type voltage-gated calcium channel gene (CACNA1C) with MDD and BD, suggesting CACNA1C as a promising candidate gene for susceptibility to mood disorders. In the present study, we tested the association of CACNA1C with MDD and BD in Han Chinese.

METHODS

We genotyped three potentially functional polymorphisms in 635 MDD patients, 286 BD patients and 730 normal, control patients.

RESULTS

The genotype frequencies of SNP rs1051375 showed statistically significant differences between the BD and control groups (P=0.005). At the allele level, the difference of G allele frequency of rs1051375 between BD patients and control subjects was also significant (P=0.011; OR=1.30, 95% CI: 1.06-1.58). We found that GG genotype of rs1051375 carriers had a lower age at onset than those with the AG or AA genotype, and the mean±standard deviation ages at onset of GG, AG and AA carriers were 24.04±4.22, 25.76±4.75 and 25.78±4.33 years, respectively. Neither genotype nor allele frequencies of the three polymorphisms were found to be significantly different between the MDD patients and control subjects.

LIMITATIONS

The relative small sample size in BD group should be considered a limitation of this study.

CONCLUSIONS

Our initial findings support a potential association of CACNA1C as a genetic risk factor for BD susceptibility.

The role of BDNF, NTRK2 gene and their interaction in development of treatment-resistant depression: data from multicenter, prospective, longitudinal clinic practice

BACKGROUND

Although genetic variants may play a key role in development of treatment-resistant depression (TRD), relevant research is scarce.

METHODS

To examine whether the polymorphisms of BDNF (rs6265) and NTRK2 (rs1387923, rs2769605 and rs1565445) genes confer risk for TRD in major depressive disorder (MDD), a total of 948 MDD patients were recruited in a 12-week, multicenter, prospective longitudinal study.

RESULTS

Our study showed a significant allelic association between rs1565445 and TRD with an excess of the T allele in the TRD group, compared to non-TRD group (OR = 1.43, 95%CI: 1.16-1.76, p = 0.0008); while patients with genotype C/C and T/C in rs1565445 were less likely to develop TRD than those carrying T/T (OR = 0.52, 95%CI: 0.33-0.82; OR = 0.72, 95%CI: 0.54-0.97, respectively; p = 0.005). Haplotype T-T (rs1565445 and rs1387923) had 1.41-fold increased risk of TRD (p = 0.0014). Furthermore, significant four-locus (rs1387923-rs1565445-rs2769605-rs6265) gene-gene interactions were detected by the Multifactor-dimensionality reduction (MDR) method.

DISCUSSION

These results suggest that the interactions of BDNF (rs6265) with NTRK2 (rs1387923, rs2769605 and rs1565445) gene polymorphisms likely play an essential role in the development of TRD in Han Chinese MDD patients.

Evidence for single nucleotide polymorphisms and their association with bipolar disorder

Bipolar disorder (BD) is a complex disorder with a number of susceptibility genes and environmental risk factors involved in its pathogenesis. In recent years, huge progress has been made in molecular techniques for genetic studies, which have enabled identification of numerous genomic regions and genetic variants implicated in BD across populations. Despite the abundance of genetic findings, the results have often been inconsistent and not replicated for many candidate genes/single nucleotide polymorphisms (SNPs). Therefore, the aim of the review presented here is to summarize the most important data reported so far in candidate gene and genome-wide association studies. Taking into account the abundance of association data, this review focuses on the most extensively studied genes and polymorphisms reported so far for BD to present the most promising genomic regions/SNPs involved in BD. The review of association data reveals evidence for several genes (SLC6A4/5-HTT [serotonin transporter gene], BDNF [brain-derived neurotrophic factor], DAOA [D-amino acid oxidase activator], DTNBP1 [dysbindin], NRG1 [neuregulin 1], DISC1 [disrupted in schizophrenia 1]) to be crucial candidates in BD, whereas numerous genome-wide association studies conducted in BD indicate polymorphisms in two genes (CACNA1C [calcium channel, voltage-dependent, L type, alpha 1C subunit], ANK3 [ankyrin 3]) replicated for association with BD in most of these studies. Nevertheless, further studies focusing on interactions between multiple candidate genes/SNPs, as well as systems biology and pathway analyses are necessary to integrate and improve the way we analyze the currently available association data.