Polymorphisms in GRIK4, HTR2A, and FKBP5 show interactive effects in predicting remission to antidepressant treatment

MALDI-TOF MS-based SNP assay used to determine the appropriate antidepression for Chinese patients

Medicine remains the preferred primary treatment for depression, although some patients show remarkable individual variations in achieving satisfactory clinical outcomes during medication. Genetic polymorphisms cause approximately 40 % of individual differences in treatment response. Therefore, this study aimed to develop a technique to identify single nucleotide polymorphisms (SNPs) associated with the metabolism, effectiveness, and side effects of antidepressant medications in Chinese patients. Bibliometrics was used to search literature related to "depression" and "SNP" in Web of Science. The obtained SNP information was screened using the PharmGKB database. By designing and optimizing primers and conducting a compound amplification system, a method was established based on MALDI-TOF MS to detect polymorphisms associated with the antidepressant drugs, including sertraline, fluoxetine, citalopram, escitalopram, venlafaxine, fluvoxamine, paroxetine, and mirtazapine. The accuracy and sensitivity of the established method were verified by Sanger sequencing. A total of 10,043 articles were screened from the database, and 46 SNPs with a mutation frequency of >1 % in Asian populations and annotated with relevant clinical drugs were extracted from the PharmGKB database. This method was compared with the results of Sanger sequencing, and the accuracy of the detection results was 100 %. The MALDI-TOF MS-based SNP assay developed in this study can be a fast, convenient and effective way for patients to find the right medication for themselves. Moreover, we found that this SNP assay holds the promise of being a potential reference tool for assessing individualised differences in drug efficacy, not only for screening the causes of poor antidepressant efficacy in patients after taking medication, but also for advising physicians to understand individualised differences in drug efficacy.

Association of the GRIK4 rs1954787 polymorphism with clinical response in antidepressant-treated depressed patients: results from a prospective cohort and meta-analysis

Major Depressive Disorder (MDD) is the leading cause of disability worldwide. Genetic factors influence the effect of its main treatment option, antidepressant drugs (ATD). The GRIK4 rs1954787(T>C) genetic polymorphism was associated with response following 1-3 months of ATD treatment in some studies, but not others. We aimed to analyze its association with clinical outcomes in a cohort of 6-month ATD-treated patients and meta-analysis. Clinical data were obtained at baseline and after 1 (M1), 3 (M3), and 6 (M6) months of ATD treatment in 390 patients of the METADAP cohort. Mixed-effects models were used to assess the association of the GRIK4 rs1954787 polymorphism with the Hamilton Depression Rating Scale (HDRS) score and response and remission rates across time. Meta-analyses of ATD treatment response were performed with previously meta-analyzed data and METADAP. Compared to C allele carriers at M3 (n = 200), TT homozygotes at M3 (n = 66) had higher HDRS scores (coef = 3.37, 95% CI [1.30-5.54], Padj = 0.0046) and lower remission rates (OR = 0.36, 95% CI [0.16-0.76], Padj = 0.029). At M6, greater differences between TT homozygotes (n = 53) and C allele carriers (n = 152) were observed for HDRS scores (coef = 4.68, 95% CI [2.17-7.18], Padj = 0.00091) and remission rates (OR = 0.26, 95% CI [0.12-0.54], Padj = 0.0016). Meta-analyses of response were significant when comparing C vs T alleles (OR = 1.31, 95% CI [1.06-1.62], P = 0.014) and CC vs TT genotypes (OR = 1.63, 95% CI [1.10-2.38], P = 0.019). Altogether, our results support an association of the GRIK4 rs1954787(T>C) polymorphism with clinical improvement following ATD treatment. This association should be further assessed in other longitudinal studies. Its position within the glutamatergic system may help in understanding the mechanism of ATD action.

Treatment-resistant depression: molecular mechanisms and management

Due to the heterogeneous nature of depression, the underlying etiological mechanisms greatly differ among individuals, and there are no known subtype-specific biomarkers to serve as precise targets for therapeutic efficacy. The extensive research efforts over the past decades have not yielded much success, and the currently used first-line conventional antidepressants are still ineffective for close to 66% of patients. Most clinicians use trial-and-error treatment approaches, which seem beneficial to only a fraction of patients, with some eventually developing treatment resistance. Here, we review evidence from both preclinical and clinical studies on the pathogenesis of depression and antidepressant treatment response. We also discuss the efficacy of the currently used pharmacological and non-pharmacological approaches, as well as the novel emerging therapies. The review reveals that the underlying mechanisms in the pathogenesis of depression and antidepressant response, are not specific, but rather involve an interplay between various neurotransmitter systems, inflammatory mediators, stress, HPA axis dysregulation, genetics, and other psycho-neurophysiological factors. None of the current depression hypotheses sufficiently accounts for the interactional mechanisms involved in both its etiology and treatment response, which could partly explain the limited success in discovering efficacious antidepressant treatment. Effective management of treatment-resistant depression (TRD) requires targeting several interactional mechanisms, using subtype-specific and/or personalized therapeutic modalities, which could, for example, include multi-target pharmacotherapies in augmentation with psychotherapy and/or other non-pharmacological approaches. Future research guided by interaction mechanisms hypotheses could provide more insights into potential etiologies of TRD, precision biomarker targets, and efficacious therapeutic modalities.

Receptor Pharmacogenomics: Deciphering Genetic Influence on Drug Response

The paradigm "one drug fits all" or "one dose fits all" will soon be challenged by pharmacogenetics research and application. Drug response-efficacy or safety-depends on interindividual variability. The current clinical practice does not include genetic screening as a routine procedure and does not account for genetic variation. Patients with the same illness receive the same treatment, yielding different responses. Integrating pharmacogenomics in therapy would provide critical information about how a patient will respond to a certain drug. Worldwide, great efforts are being made to achieve a personalized therapy-based approach. Nevertheless, a global harmonized guideline is still needed. Plasma membrane proteins, like receptor tyrosine kinase (RTK) and G protein-coupled receptors (GPCRs), are ubiquitously expressed, being involved in a diverse array of physiopathological processes. Over 30% of drugs approved by the FDA target GPCRs, reflecting the importance of assessing the genetic variability among individuals who are treated with these drugs. Pharmacogenomics of transmembrane protein receptors is a dynamic field with profound implications for precision medicine. Understanding genetic variations in these receptors provides a framework for optimizing drug therapies, minimizing adverse reactions, and advancing the paradigm of personalized healthcare.

Structural variation of the coding and non-coding human pharmacogenome

Genetic variants in drug targets and genes encoding factors involved in drug absorption, distribution, metabolism and excretion (ADME) can have pronounced impacts on drug pharmacokinetics, response, and toxicity. While the landscape of genetic variability at the level of single nucleotide variants (SNVs) has been extensively studied in these pharmacogenetic loci, their structural variation is only poorly understood. Thus, we systematically analyzed the genetic structural variability across 908 pharmacogenes (344 ADME genes and 564 drug targets) based on publicly available whole genome sequencing data from 10,847 unrelated individuals. Overall, we extracted 14,984 distinct structural variants (SVs) ranging in size from 50 bp to 106 Mb. Each individual harbored on average 10.3 and 1.5 SVs with putative functional effects that affected the coding regions of ADME genes and drug targets, respectively. In addition, by cross-referencing pharmacogenomic SVs with experimentally determined binding data of 224 transcription factors across 130 cell types, we identified 1276 non-coding SVs that overlapped with gene regulatory elements. Based on these data, we estimate that non-coding structural variants account for 22% of the genetically encoded pharmacogenomic variability. Combined, these analyses provide the first comprehensive map of structural variability across pharmacogenes, derive estimates for the functional impact of non-coding SVs and incentivize the incorporation of structural genomic data into personalized drug response predictions.

DRD2, DRD3, and HTR2A Single-Nucleotide Polymorphisms Involvement in High Treatment Resistance to Atypical Antipsychotic Drugs

BACKGROUND

The objective of this study was to investigate the DRD2 rs1800497, rs1799732, rs1801028, DRD3 rs6280, and HTR2A rs6314, rs7997012, and rs6311 single-nucleotide polymorphism (SNP) correlations with resistance to second-generation antipsychotics (SGAs) in a real-world sample of patients with treatment-resistant mental disorders.

METHODS

We divided 129 participants into a high treatment resistance (HTR) group (current treatment with two SGAs, or clozapine, or classic neuroleptics for a failure of previous SGAs trials) and a low treatment resistance (LTR) group (current treatment with one atypical antipsychotic). We used Next-Generation Sequencing on DNA isolated from peripheral blood samples to analyze the polymorphisms. We performed logistic regression to search for predictors of HTR membership.

RESULTS

A diagnosis of schizophrenia significantly predicted the HTR membership compared to other diagnoses. Other predictors were the DRD3 rs6280 C|T (OR = 22.195) and T|T (OR = 18.47) vs. C|C, HTR2A rs7997012 A|G vs. A|A (OR = 6.859) and vs. G|G (OR = 2.879), and DRD2 rs1799732 I|I vs. D|I (OR = 12.079) genotypes.

CONCLUSIONS

A diagnosis of schizophrenia and the DRD2 rs1799732, DRD3 rs6280, and HTR2A rs7997012 genotypes can predict high treatment resistance to SGAs.

Role of FKBP5 and its genetic mutations in stress-induced psychiatric disorders: an opportunity for drug discovery

Stress-induced mental health disorders are affecting many people around the world. However, effective drug therapy for curing psychiatric diseases does not occur sufficiently. Many neurotransmitters, hormones, and mechanisms are essential in regulating the body's stress response. One of the most critical components of the stress response system is the hypothalamus-pituitary-adrenal (HPA) axis. The FKBP prolyl isomerase 51 (FKBP51) protein is one of the main negative regulators of the HPA axis. FKBP51 negatively regulates the cortisol effects (the end product of the HPA axis) by inhibiting the interaction between glucocorticoid receptors (GRs) and cortisol, causing reduced transcription of downstream cortisol molecules. By regulating cortisol effects, the FKBP51 protein can indirectly regulate the sensitivity of the HPA axis to stressors. Previous studies have indicated the influence of FKBP5 gene mutations and epigenetic changes in different psychiatric diseases and drug responses and recommended the FKBP51 protein as a drug target and a biomarker for psychological disorders. In this review, we attempted to discuss the effects of the FKBP5 gene, its mutations on different psychiatric diseases, and drugs affecting the FKBP5 gene.

Pharmacogenetic Testing for the Pediatric Gastroenterologist: Actionable Drug-Gene Pairs to Know

Gastroenterologists represent some of the earlier adopters of precision medicine through pharmacogenetic testing by embracing upfront genotyping for thiopurine S-methyltransferase nucleotide diphosphatase (TPMT) before prescribing 6-mercaptopurine or azathioprine for the treatment of inflammatory bowel disease. Over the last two decades, pharmacogenetic testing has become more readily available for other genes relevant to drug dose individualization. Common medications prescribed by gastroenterologists for conditions other than inflammatory bowel disease now have actionable guidelines, which can improve medication efficacy and safety; however, a clear understanding of how to interpret the results remains a challenge for many clinicians, precluding wide implementation of genotype-guided dosing for drugs other than 6-mercaptopurine and azathioprine. Our goal is to provide a practical tutorial on the currently available pharmacogenetic testing options and a results interpretation for drug-gene pairs important to medications commonly used in pediatric gastroenterology. We focus on evidence-based clinical guidelines published by the Clinical Pharmacogenetics Implementation Consortium (CPIC^®) to highlight relevant drug-gene pairs, including proton pump inhibitors and selective serotonin reuptake inhibitors and cytochrome P450 (CYP) 2C19, ondansetron and CYP2D6, 6-mercaptopurine and TMPT and Nudix hydrolase 15 (NUDT15), and budesonide and tacrolimus and CYP3A5.

BDNF as a Mediator of Antidepressant Response: Recent Advances and Lifestyle Interactions

Conventional antidepressants are widely employed in several psychiatric and neurologic disorders, yet the mechanisms underlying their delayed and partial therapeutic effects are only gradually being understood. This narrative review provides an up-to-date overview of the interplay between antidepressant treatment and Brain-Derived Neurotrophic Factor (BDNF) signaling. In addition, the impact of nutritional, environmental and physiological factors on BDNF and the antidepressant response is outlined. This review underlines the necessity to include information on lifestyle choices in testing and developing antidepressant treatments in the future.

Genetic variables of the glutamatergic system associated with treatment-resistant depression: A review of the literature

Depression is a common, recurrent mental disorder and one of the leading causes of disability and global burden of disease worldwide. Up to 15%-40% of cases do not respond to diverse pharmacological treatments and, thus, can be defined as treatment-resistant depression (TRD). The development of biomarkers predictive of drug response could guide us towards personalized and earlier treatment. Growing evidence points to the involvement of the glutamatergic system in the pathogenesis of TRD. Specifically, the N-methyl-D-aspartic acid receptor (NMDAR) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), which are targeted by ketamine and esketamine, are proposed as promising pathways. A literature search was performed to identify studies on the genetics of the glutamatergic system in depression, focused on variables related to NMDARs and AMPARs. Our review highlights GRIN2B, which encodes the NR2B subunit of NMDAR, as a candidate gene in the pathogenesis of TRD. In addition, several studies have associated genes encoding AMPAR subunits with symptomatic severity and suicidal ideation. These genes encoding glutamatergic receptors could, therefore, be candidate genes for understanding the etiopathogenesis of TRD, as well as for understanding the pharmacodynamic mechanisms and response to ketamine and esketamine treatment.

The pharmacogenomics of selective serotonin reuptake inhibitors

Antidepressant medications are frequently used as the first line of treatment for depression. However, their effectiveness is highly variable and influenced by genetic factors. Recently, pharmacogenetic studies, including candidate-gene, genome-wide association studies or polygenic risk scores, have attempted to uncover the genetic architecture of antidepressant response. Genetic variants in at least 27 genes are linked to antidepressant treatment response in both coding and non-coding genomic regions, but evidence is largely inconclusive due to the high polygenicity of the trait and limited cohort sizes in published studies. Future studies should increase the number and diversity of participants to yield sufficient statistical power to characterize the genetic underpinnings and biological mechanisms of treatment response, improve results generalizability and reduce racial health-related inequities.

DNA Genotyping Based on Isothermal Amplification and Colorimetric Detection by Consumer Electronics Devices

The point-of-care testing of DNA biomarkers requires compact biosensing systems and consumer electronic technologies provide fascinating opportunities. Their portability, mass-produced components, and high-performance readout capabilities are the main advantages for the development of novel bioanalytical methods.This chapter describes the detection of single nucleotide polymorphisms (SNP) through methods based on user-friendly optical devices (e.g., USB digital microscope, flatbed scanner, smartphone, and DVD drive). Loop mediated isothermal amplification (LAMP) enables the required discrimination of each specific variant prior to the optical reading. In the first method, products are directly hybridized to the allele-specific probes attached to plastic chips in an array format. The second method, allele-specific primers are used, enabling the direct end-point detection based a colorimetric dyer and a microfluidic chamber chip. In both approaches, devices are employed for chip scanning.A representative application to the genotyping of a clinically relevant SNP from human samples is provided, showing the excellent features achieved. Consumer electronic devices are able to register sensitive precise measurements in terms of signal-to-noise ratios, image resolution, and scan-to-scan reproducibility. The integrated DNA-based method lead a low detection limit (100 genomic DNA copies), reproducible (variation <15%), high specificity (genotypes validated by reference method), and cheap assays (<10 €/test). The underlying challenge is the reliable implementation into minimal-specialized clinical laboratories, incorporating additional advantages, such as user-friendly interface, low cost, and connectivity for telemedicine needs.

Pharmacogenetically Guided Escitalopram Treatment for Pediatric Anxiety Disorders: Protocol for a Double-Blind Randomized Trial

Current pharmacologic treatments for pediatric anxiety disorders (e.g., selective serotonin reuptake inhibitors (SSRIs)) frequently use "one size fits all" dosing strategies based on average responses in clinical trials. However, for some SSRIs, including escitalopram, variation in CYP2C19 activity produces substantial variation in medication exposure (i.e., blood medication concentrations). This raises an important question: would refining current SSRI dosing strategies based on CYP2C19 phenotypes increase response and reduce side effect burden? To answer this question, we designed a randomized, double-blind trial of adolescents 12-17 years of age with generalized, separation, and/or social anxiety disorders (N = 132). Patients are randomized (1:1) to standard escitalopram dosing or dosing based on validated CYP2C19 phenotypes for escitalopram metabolism. Using this approach, we will determine whether pharmacogenetically-guided treatment-compared to standard dosing-produces faster and greater reduction in anxiety symptoms (i.e., response) and improves tolerability (e.g., decreased risk of treatment-related activation and weight gain). Secondarily, we will examine pharmacodynamic variants associated with treatment outcomes, thus enhancing clinicians' ability to predict response and tolerability. Ultimately, developing a strategy to optimize dosing for individual patients could accelerate response while decreasing side effects-an immediate benefit to patients and their families. ClinicalTrials.gov Identifier: NCT04623099.

Genetic Diversity of Drug-Related Genes in Native Americans of the Brazilian Amazon

Introduction

The genetic admixture of the Brazilian population has considerable relevance to the implementation of the principles of pharmacogenomics (PGx), as it may compromise the extrapolation of data obtained in more homogeneous world populations.

Purpose

This study aims to investigate a panel of 117 polymorphisms in 35 pharmacogenes, which contains label recommendations or clinical evidence by international drug regulatory agencies, in Amazonian Native American populations, and compare the results obtained with continental population data from the 1000 Genomes Project Consortium.

Patients and Methods

The study population is composed of 109 Native American individuals from three Brazilian Amazon groups. The genotyping of the PGx polymorphisms was performed by allelic discrimination using TaqMan^® OpenArray Genotyping with a panel of 120 customized assays on the QuantStudio™ 12K Flex Real-Time PCR System.

Results

Statistical differences within the Native American populations were observed regarding both genotypes and phenotypes of some genes of the CYP family. The discriminant analysis of principal components (DAPCs) between the NAM group and the continental populations of the 1000 Genomes Project resulted in the clustering of the three Native American populations. Additionally, in general, the NAM group was determined to be closely situated between East Asia, America, and South Asia groups, which enabled us to infer a genetic similarity between these populations. The DAPC analysis further demonstrated that eight polymorphisms and six polymorphisms were more relevant in differentiating the NAM from the continental populations and the NAM populations among themselves, respectively.

Conclusion

Some investigated polymorphisms show differences among world populations, particularly with populations of European origin, for whom precision medicine protocols are primarily designed. The accumulated knowledge regarding these variations may assist in the design of specific protocols for Native American populations and populations admixed with them.

Associations between the 1438A/G, 102T/C, and rs7997012G/A polymorphisms of HTR2A and the safety and efficacy of antidepressants in depression: a meta-analysis

The correlations between hydroxytryptamine receptor 2A (HTR2A) gene polymorphisms (1438A/G, 102T/C, and rs7997012G/A) and the safety and efficacy of antidepressants in depression patients were constantly reported, but conclusions are debatable. This meta-analysis ascertained forty-two studies on the efficacy (including response and remission) and side-effect issued before February 2020. Pooled analyses indicated significant associations of 1438A/G polymorphism (16 studies, 1931 subjects) and higher response within dominant model (OR: 1.40, 95% CI: 1.12-1.76); rs7997012G/A polymorphism (nine studies, 1434 subjects) and higher remission in overall models (dominant model: OR: 1.30, 95% CI: 1.01-1.66; recessive model: OR: 2.20, 95% CI: 1.53-3.16; homozygote model: OR: 2.73, 95% CI: 1.78-4.17); 102T/C polymorphism (eight studies, 804 subjects) and reduced risk of side-effect within recessive (OR: 0.57, 95% CI: 0.4-0.83) and homozygote models (OR: 0.54, 95% CI: 0.29-0.99). For depression patients, genotyping of HTR2A polymorphisms is a promising tool for estimating the outcome and side-effect of antidepressants.

Low Circulating Levels of GR, FKBP5, and SGK1 in Medicated Patients With Depression Are Not Altered by Electroconvulsive Therapy

OBJECTIVES

Hypothalamic-pituitary-adrenal axis dysregulation is frequently observed in patients with depression, with increased levels of the glucocorticoid (GC) cortisol commonly reported. Hypothalamic-pituitary-adrenal axis dysregulation may be a consequence of impaired feedback inhibition due to GC receptor (GR) impairments or dysfunction, termed "glucocorticoid resistance." Here, our objective was to assess mRNA levels of GC-related markers (GR, FKBP5, serum glucocorticoid kinase 1 [SGK1]) in patients with depression versus controls and in patient samples after electroconvulsive therapy (ECT). We also examined the relationship between these GC-related markers and 24-item Hamilton Depression Rating Scale (HAM-D24) scores to assess the utility of using them as biological markers for depression or the therapeutic response to ECT.

METHODS

GR, FKBP5, and SGK1 mRNA levels were examined in whole blood samples from 88 medicated patients with depression pre-/post-ECT and 63 controls using quantitative real-time polymerase chain reaction. Exploratory subgroup correlational analyses were performed to determine the relationship between GR, FKBP5, and SGK1 and 24-item Hamilton Depression Rating Scale scores.

RESULTS

GR, FKBP5, and SGK1 mRNA levels were significantly lower in medicated patients with depression compared with controls (P < 0.001, P = 0.03, P < 0.001, respectively), but ECT did not alter their levels (all P > 0.05). There was no relationship between GR, FKBP5, or SGK1 and 24-item Hamilton Depression Rating Scale scores.

CONCLUSIONS

GR, FKBP5, and SGK1 do not seem to be involved in the peripheral molecular response to ECT and do not represent useful biomarkers for predicting the therapeutic response to ECT in a real-world clinical setting.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of low dose lysergic acid diethylamide (LSD) in healthy older volunteers

Research has shown that psychedelics, such as lysergic acid diethylamide (LSD), have profound anti-inflammatory properties mediated by 5-HT2A receptor signaling, supporting their evaluation as a therapeutic for neuroinflammation associated with neurodegenerative disease.

OBJECTIVE

This study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of orally repeated administration of 5 μg, 10 μg, and 20 μg LSD in older healthy individuals. In the current paper, we present safety, tolerability, pharmacokinetics, and pharmacodynamic measures that relate to safety, tolerability, and dose response.

METHODS

This was a phase 1 double-blind, placebo-controlled, randomized study. Volunteers were randomly assigned to 1 of 4 dose groups (5 μg, 10 μg, 20 μg LSD, and placebo), and received their assigned dose on six occasions (i.e., every 4 days).

RESULTS

Forty-eight older healthy volunteers (mean age = 62.9 years) received placebo (n = 12), 5 μg (n = 12), 10 μg (n = 12), or 20 μg (n = 12) LSD. LSD plasma levels were undetectable for the 5 μg group and peak blood plasma levels for the 10 μg and 20 μg groups occurred at 30 min. LSD was well tolerated, and the frequency of adverse events was no higher than for placebo. Assessments of cognition, balance, and proprioception revealed no impairment.

CONCLUSIONS

Our results suggest safety and tolerability of orally administered 5 μg, 10 μg, and 20 μg LSD every fourth day over a 21-day period and support further clinical development of LSD for the treatment and prevention of Alzheimer's disease (AD).

Analysis of the Deleterious Single-Nucleotide Polymorphisms Associated With Antidepressant Efficacy in Major Depressive Disorder

Major depressive disorder (MDD) is a serious mental disease with negative effects on both mental and physical health of the patient. Currently, antidepressants are among the major ways to ease or treat MDD. However, the existing antidepressants have limited efficacy in treating MDD, with a large fraction of patients either responding inadequately or differently to antidepressants during the treatment. Pharmacogenetics studies have found that the genetic features of some genes are associated with the antidepressant efficacy. In order to obtain a better understanding on the relationship between the genetic factors and antidepressant treatment response, we compiled a list of 233 single-nucleotide polymorphisms (SNPs) significantly associated with the antidepressant efficacy in treating MDD. Of the 13 non-synonymous SNPs in the list, three (rs1065852, rs3810651, and rs117986340) may influence the structures and function of the corresponding proteins. Besides, the influence of rs1065852 on the structure of CYP2D6 was further investigated via molecular dynamics simulations. Our results showed that compared to the native CYP2D6 the flexibility of the F-G loop was reduced in the mutant. As a portion of the substrate access channel, the lower flexibility of F-G loop may reduce the ability of the substrates to enter the channel, which may be the reason for the lower enzyme activity of mutant. This study may help us to understand the impact of genetic variation on antidepressant efficacy and provide clues for developing new antidepressants.

Damaging coding variants within kainate receptor channel genes are enriched in individuals with schizophrenia, autism and intellectual disabilities

Schizophrenia (Scz), autism spectrum disorder (ASD) and intellectual disability are common complex neurodevelopmental disorders. Kainate receptors (KARs) are ionotropic glutamate ion channels involved in synaptic plasticity which are modulated by auxiliary NETO proteins. Using UK10K exome sequencing data, we interrogated the coding regions of KAR and NETO genes in individuals with Scz, ASD or intellectual disability and population controls; performed follow-up genetic replication studies; and, conducted in silico and in vitro functional studies. We found an excess of Loss-of-Function and missense variants in individuals with Scz compared with control individuals (p = 1.8 × 10⁻¹⁰), and identified a significant burden of functional variants for Scz (p < 1.6 × 10⁻¹¹) and ASD (p = 6.9 × 10⁻¹⁸). Single allele associations for 6 damaging missense variants were significantly replicated (p < 5.0 × 10⁻¹⁵) and confirmed GRIK3 S310A as a protective genetic factor. Functional studies demonstrated that three missense variants located within GluK2 and GluK4, GluK2 (K525E) and GluK4 (Y555N, L825W), affect agonist sensitivity and current decay rates. These findings establish that genetic variation in KAR receptor ion channels confers risk for schizophrenia, autism and intellectual disability and provide new genetic and pharmacogenetic biomarkers for neurodevelopmental disease.

Clinical association to FKBP5 rs1360780 in patients with depression

The FKBP5 protein is of importance for the function of the glucocorticoid receptor. The purpose of the present study was to examine the possible association between the different genotypes of rs1360780 in the FKBP5 gene, and clinical symptoms in patients with unipolar depression. Seven hundred eighteen patients and 673 controls from the Danish Psychiatric Biobank were participated. No association was found between any genotype and diagnosis of unipolar depression. It was found that the group of depressed patients with the CC genotype showed significantly earlier start of treatment with medicine, had a significantly greater tendency to be treated with electroconvulsive therapy and showed a significantly higher frequency of family history of depression compared with the combined group of patients with the CT and TT genotypes. The only informations about controls were their sex and that they were recruited from the blood bank. The clinical data were not complete for all patients.

Convergent neurobiological predictors of mood and anxiety symptoms and treatment response

Introduction: Mood and anxiety disorders are leading contributors to the global burden of diseases. Comorbid mood and anxiety disorders have a lifetime prevalence of ~20% globally and increases the risk for suicide, a leading cause of death. Areas covered: In this review, authors highlight recent advances in the understanding of multilevel-neurobiological mechanisms for normal/pathological human affective-functioning. The authors then address the complex interplay between environmental-adversity and molecular-genetic mediators of brain correlates of affective-symptoms. The molecular focus is strategically limited to GTF2i, BDNF, and FKBP5 genes that are, respectively, involved in transcriptional-, neurodevelopmental- and neuroendocrine-pathway mediation of affective-functions. The importance of these genes is illustrated with studies of copy-number-variants, genome-wide association (GWAS), and candidate gene-sequence variant associations with disease etiology. Authors concluded by highlighting the predictive values of integrative neurobiological processing of gene-environment interactions for affective disorder symptom management. Expert opinion: Given the transcriptional, neurodevelopmental and neuroimmune relevance of GTF2i, BDNF, and FKBP5 genes, respectively, authors reviewed the putative roles of these genes in neurobiological mediation of adaptive affective-responses. Authors discussed the importance of studying gene-dosage effects in understanding affective disorder risk biology, and how such targeted neurogenetic studies could guide precision identification of novel pharmacotherapeutic targets and aid in prediction of treatment response.

Pharmacogenetics of Sertraline Tolerability and Response in Pediatric Anxiety and Depressive Disorders

Objective: To determine whether genetic variants in a pharmacokinetic gene (the number of CYP2C19 reduced function alleles [RFAs]), and in pharmacodynamic genes (HTR2A, SLC6A4, and GRIK4) influence sertraline tolerability and response in a cohort of pediatric patients with anxiety and depressive disorders. Methods: A retrospective analysis was performed using the electronic medical record data of 352 patients <19 years of age being treated for anxiety and/or depressive disorders with sertraline and who underwent routine clinical CYP2C19 genotyping. Additional genotyping and analysis of variants in HTR2A, SLC6A4, and GRIK4 were conducted for 249 patients. Multivariate regression models testing for associations with CYP2C19 were adjusted for concomitant use of interacting medications. Combinatorial classification and regression tree (CART) analyses containing all pharmacokinetic and pharmacodynamic genes and clinical factors were performed. Results: The maximum sertraline dose during the initial titration period of sertraline was inversely associated with the number of CYP2C19 RFAs and sertraline dose at 60 (p = 0.025) and 90 days (p = 0.025). HTR2A rs6313 was associated with sertraline dose (p = 0.011) and time to the average maximum sertraline dose (p = 0.039). Regarding efficacy, the number of CYP2C19 RFAs was not associated with the sertraline dose at the time of response (p = 0.22), whereas for the pharmacodynamic genes, only HTR2A rs6313 was associated with response dose (p = 0.022). An association was observed between predicted expression levels of SLC6A4 and the duration on sertraline (p = 0.025). Combinatorial CART and multivariate regression analyses implicated that pharmacodynamic genes and clinical factors influence the maximum sertraline dose and response dose. The total number of side effects was not associated with any of the variants tested. Conclusion: Both pharmacokinetic and pharmacodynamic factors, in addition to clinical and demographic components, influence sertraline dose, response, and tolerability, thereby necessitating further research to assess for the validity of these pharmacogenetic associations in children and adolescents.

GRIK4 and GRM7 gene may be potential indicator of venlafaxine treatment reponses in Chinese of Han ethnicity

Venlafaxine is one of commonly prescribed antidepressants for major depressive disorder (MDD). Accumulated evidence implicates the involvement of glutamatergic receptors in the pathophysiology of MDD and antidepressant treatment.By using 193 MDD patients who have been taking venlafaxine for 6 weeks, we investigated whether single nucleotide polymorphisms (SNPs) in glutamate ionotropic receptor kainate type subunit 4 (GRIK4), glutamate ionotropic receptor AMPA type subunit 1 (GRIA1) and glutamate metabotropic receptor 7 (GRM7) were associated with treatment response. 14 SNPs were selected randomly depended on association studies. Efficacy of treatment was determined by 17-item of Hamilton Rating Scale. Allele and genotype frequencies were compared between responders and non-responders.After adjusting by the false discovery rate (FDR), rs6589847 and rs56275759 in GRIK4 and rs9870680 in GRM7 showed associating with venlafaxine treatment response at week 6. (FDR: P = .018, P = .042, and P = .040, respectively).Our results indicated that genetic variants in the GRIK4 and GRM7 may associate with the treatment response in MDD patients treated by venlafaxine.

Systems Approach to Identify Common Genes and Pathways Associated with Response to Selective Serotonin Reuptake Inhibitors and Major Depression Risk

Despite numerous studies on major depressive disorder (MDD) susceptibility, the precise underlying molecular mechanism has not been elucidated which restricts the development of etiology-based disease-modifying drug. Major depressive disorder treatment is still symptomatic and is the leading cause of (~30%) failure of the current antidepressant therapy. Here we comprehended the probable genes and pathways commonly associated with antidepressant response and MDD. A systematic review was conducted, and candidate genes/pathways associated with antidepressant response and MDD were identified using an integrative genetics approach. Initially, single nucleotide polymorphisms (SNPs)/genes found to be significantly associated with antidepressant response were systematically reviewed and retrieved from the candidate studies and genome-wide association studies (GWAS). Also, significant variations concerning MDD susceptibility were extracted from GWAS only. We found 245 (Set A) and 800 (Set B) significantly associated genes with antidepressant response and MDD, respectively. Further, gene set enrichment analysis revealed the top five co-occurring molecular pathways (p ≤ 0.05) among the two sets of genes: Cushing syndrome, Axon guidance, cAMP signaling pathway, Insulin secretion, and Glutamatergic synapse, wherein all show a very close relation to synaptic plasticity. Integrative analyses of candidate gene and genome-wide association studies would enable us to investigate the putative targets for the development of disease etiology-based antidepressant that might be more promising than current ones.

How to choose an antidepressant medication

OBJECTIVE

We consider how to choose an antidepressant (AD) medication for the treatment of clinical depression.

METHOD

A narrative review was undertaken addressing antidepressant 'choice' considering a range of parameters either weighted by patients and clinicians or suggested in the scientific literature. Findings were synthesised and incorporated with clinical experience into a model to assist AD choice.

RESULTS

Efficacy studies comparing ADs offer indicative guidance, while precision psychiatry prediction based on genetics, developmental trauma, neuroimaging, behavioural and cognitive biomarkers, currently has limited clinical utility. Our model offers guidance for AD choice by assessing first for the presence of a depressive subtype or symptom cluster and matching choice of AD class accordingly. Failing this, an AD can be chosen based on depression severity. Within-class choice can be determined by reference to personality style, patient preference, medical or psychiatric comorbidities and side-effect profile.

CONCLUSION

Clarification of AD choice would occur if medications are trialled in specific depressive subtypes rather than using the generic diagnosis of major depressive disorder (MDD). Such 'top-down' methods could be enhanced by 'bottom-up' studies to classify individuals according to symptom clusters and biomarkers with AD efficacy tested in these categories. Both methods could be utilised for personalised AD choice.

Influence of CYP2C19 Metabolizer Status on Escitalopram/Citalopram Tolerability and Response in Youth With Anxiety and Depressive Disorders

In pediatric patients, the selective serotonin reuptake inhibitors (SSRIs) escitalopram and citalopram (es/citalopram) are commonly prescribed for anxiety and depressive disorders. However, pharmacogenetic studies examining CYP2C19 metabolizer status and es/citalopram treatment outcomes have largely focused on adults. We report a retrospective study of electronic medical record data from 263 youth < 19 years of age with anxiety and/or depressive disorders prescribed escitalopram or citalopram who underwent routine clinical CYP2C19 genotyping. Slower CYP2C19 metabolizers experienced more untoward effects than faster metabolizers (p = 0.015), including activation symptoms (p = 0.029) and had more rapid weight gain (p = 0.018). A larger proportion of slower metabolizers discontinued treatment with es/citalopram than normal metabolizers (p = 0.007). Meanwhile, faster metabolizers responded more quickly to es/citalopram (p = 0.005) and trended toward less time spent in subsequent hospitalizations (p = 0.06). These results highlight a disparity in treatment outcomes with es/citalopram treatment in youth with anxiety and/or depressive disorders when standardized dosing strategies were used without consideration of CYP2C19 metabolizer status. Larger, prospective trials are warranted to assess whether tailored dosing of es/citalopram based on CYP2C19 metabolizer status improves treatment outcomes in this patient population.

Further Support for the Involvement of Genetic Variants Related to the Serotonergic Pathway in the Antidepressant Response in Children and Adolescents After a 12-Month Follow-Up: Impact of the HTR2A rs7997012 Polymorphism

Objective: Fluoxetine is an effective and well-tolerated pharmacological treatment for children and adolescents with major depressive disorder (MDD). However, a high percentage of patients do not respond. There is a substantial genetic contribution to this variable clinical outcome. Based on previous genetic results of our group and given the lack of pharmacogenetics studies of antidepressant response with a long follow-up period, we evaluated the influence of single nucleotide polymorphisms (SNPs) in genes related to the serotonergic pathway on remission and recovery in children and adolescents diagnosed with MDD after 12 months of initiating fluoxetine treatment. Methods: The assessment was performed in 46 patients. All of them were visited at least once a month during the 12-month follow-up. Psychiatrists interviewed patients and their parents to explore clinical improvement. A total of 75 genotyped SNPs in 10 candidate genes were included in the genetic association analysis with remission and recovery. Bonferroni correction for multiple testing was applied to avoid false positive results. Results: The HTR2A rs7997012 SNP was significantly associated after Bonferroni correction with clinical improvement. Particularly, the homozygotes for the major allele (GG) showed the highest percentage of remitters and the highest score reductions on the Clinical Global Impressions-Severity (CGI-S) scale. Moreover, although the results were on the border of statistical significance, the GG homozygotes also tended to experience fewer readmissions during the follow-up period Conclusions: These results provide more evidence of the involvement of genetic variants related to the serotonergic pathway in the antidepressant response. Studies with larger cohorts are needed to integrate all relevant variants into clinical predictors of antidepressant response.

Overweight in Boys With ADHD Is Related to Candidate Genes and Not to Deficits in Cognitive Functions

OBJECTIVE

The aim of the study was to assess the relationship of overweight, the polymorphisms of selected candidate genes, and deficits in the executive functions among children with ADHD.

METHOD

We examined 109 boys with ADHD aged between 7 and 17 years. The study indicated variants of 14 polymorphisms in eight candidate genes. We applied seven neuropsychological tests to evaluate the executive functions. Overweight was diagnosed on the basis of the guidelines of the International Obesity Task Force.

RESULTS

Analyses revealed significant association between DRD4 rs1800955, SNAP25 rs363039 and rs363043, 5HTR2A rs17288723, and overweight in boys with ADHD. There were no significant differences in the level of neuropsychological test results between patients with overweight and without overweight.

CONCLUSION

Overweight in boys with ADHD is associated with polymorphisms in three candidate genes: DRD4, SNAP25, and 5HTR2A, but not through conditioning deficits in cognitive functions.

Genetic variants in major depressive disorder: From pathophysiology to therapy

In spite of promising preclinical results there is a decreasing number of new registered medications in major depression. The main reason behind this fact is the lack of confirmation in clinical studies for the assumed, and in animals confirmed, therapeutic results. This suggests low predictive value of animal studies for central nervous system disorders. One solution for identifying new possible targets is the application of genetics and genomics, which may pinpoint new targets based on the effect of genetic variants in humans. The present review summarizes such research focusing on depression and its therapy. The inconsistency between most genetic studies in depression suggests, first of all, a significant role of environmental stress. Furthermore, effect of individual genes and polymorphisms is weak, therefore gene x gene interactions or complete biochemical pathways should be analyzed. Even genes encoding target proteins of currently used antidepressants remain non-significant in genome-wide case control investigations suggesting no main effect in depression, but rather an interaction with stress. The few significant genes in GWASs are related to neurogenesis, neuronal synapse, cell contact and DNA transcription and as being nonspecific for depression are difficult to harvest pharmacologically. Most candidate genes in replicable gene x environment interactions, on the other hand, are connected to the regulation of stress and the HPA axis and thus could serve as drug targets for depression subgroups characterized by stress-sensitivity and anxiety while other risk polymorphisms such as those related to prominent cognitive symptoms in depression may help to identify additional subgroups and their distinct treatment. Until these new targets find their way into therapy, the optimization of current medications can be approached by pharmacogenomics, where metabolizing enzyme polymorphisms remain prominent determinants of therapeutic success.

Clinical Implementation of Pharmacogenetic Decision Support Tools for Antidepressant Drug Prescribing

The accrual and analysis of genomic sequencing data have identified specific genetic variants that are associated with major depressive disorder. Moreover, substantial investigations have been devoted to identifying gene-drug interactions that affect the response to antidepressant medications by modulating their pharmacokinetic or pharmacodynamic properties. Despite these advances, individual responses to antidepressants, as well as the unpredictability of adverse side effects, leave clinicians with an imprecise prescribing strategy that often relies on trial and error. These limitations have spawned several combinatorial pharmacogenetic testing products that are marketed to physicians. Typically, combinatorial pharmacogenetic decision support tools use algorithms to integrate multiple genetic variants and assemble the results into an easily interpretable report to guide prescribing of antidepressants and other psychotropic medications. The authors review the evidence base for several combinatorial pharmacogenetic decision support tools whose potential utility has been evaluated in clinical settings. They find that, at present, there are insufficient data to support the widespread use of combinatorial pharmacogenetic testing in clinical practice, although there are clinical situations in which the technology may be informative, particularly in predicting side effects.

Progress in Elucidating Biomarkers of Antidepressant Pharmacological Treatment Response: A Systematic Review and Meta-analysis of the Last 15 Years

BACKGROUND

Antidepressant drugs are widely prescribed, but response rates after 3 months are only around one-third, explaining the importance of the search of objectively measurable markers predicting positive treatment response. These markers are being developed in different fields, with different techniques, sample sizes, costs, and efficiency. It is therefore difficult to know which ones are the most promising.

OBJECTIVE

Our purpose was to compute comparable (i.e., standardized) effect sizes, at study level but also at marker level, in order to conclude on the efficacy of each technique used and all analyzed markers.

METHODS

We conducted a systematic search on the PubMed database to gather all articles published since 2000 using objectively measurable markers to predict antidepressant response from five domains, namely cognition, electrophysiology, imaging, genetics, and transcriptomics/proteomics/epigenetics. A manual screening of the abstracts and the reference lists of these articles completed the search process.

RESULTS

Executive functioning, theta activity in the rostral Anterior Cingular Cortex (rACC), and polysomnographic sleep measures could be considered as belonging to the best objectively measured markers, with a combined d around 1 and at least four positive studies. For inter-category comparisons, the approaches that showed the highest effect sizes are, in descending order, imaging (combined d between 0.703 and 1.353), electrophysiology (0.294-1.138), cognition (0.929-1.022), proteins/nucleotides (0.520-1.18), and genetics (0.021-0.515).

CONCLUSION

Markers of antidepressant treatment outcome are numerous, but with a discrepant level of accuracy. Many biomarkers and cognitions have sufficient predictive value (d ≥ 1) to be potentially useful for clinicians to predict outcome and personalize antidepressant treatment.

Peripheral biomarkers of major depression and antidepressant treatment response: Current knowledge and future outlooks

BACKGROUND

In recent years, we have accomplished a deeper understanding about the pathophysiology of major depressive disorder (MDD). Nevertheless, this improved comprehension has not translated to improved treatment outcome, as identification of specific biologic markers of disease may still be crucial to facilitate a more rapid, successful treatment. Ongoing research explores the importance of screening biomarkers using neuroimaging, neurophysiology, genomics, proteomics, and metabolomics measures.

RESULTS

In the present review, we highlight the biomarkers that are differentially expressed in MDD and treatment response and place a particular emphasis on the most recent progress in advancing technology which will continue the search for blood-based biomarkers.

LIMITATIONS

Due to space constraints, we are unable to detail all biomarker platforms, such as neurophysiological and neuroimaging markers, although their contributions are certainly applicable to a biomarker review and valuable to the field.

CONCLUSIONS

Although the search for reliable biomarkers of depression and/or treatment outcome is ongoing, the rapidly-expanding field of research along with promising new technologies may provide the foundation for identifying key factors which will ultimately help direct patients toward a quicker and more effective treatment for MDD.

Epigenetic Changes of FKBP5 as a Link Connecting Genetic and Environmental Risk Factors with Structural and Functional Brain Changes in Major Depression

The gene for the glucocorticoid receptor regulator FK506 binding protein 5 (FKBP5) plays a role for risk, response to treatment, and changes in brain areas in major depressive disorder (MDD). Chronic stress is associated with lower methylation of FKBP5. Our aim was to investigate whether methylation of FKBP5 reflected exposure to childhood adversity in MDD and controls and whether it was associated with structure and function of emotional processing regions. FKBP5 intron 7 GR response element region methylation and rs1360780 allelic status were assessed from whole blood in 56 MDD adults and 50 controls. Using magnetic resonance imaging, we assessed gray matter concentration of selected areas and their function during valence recognition of emotional images. Childhood adversity was investigated using the Childhood Trauma Questionnaire. In MDD patients carrying the high-risk T allele of rs1360780, lower methylation of FKBP5 was predicted by childhood adversity (F=4.95, p=0.04). In all participants, lower FKBP5 intron methylation levels were associated with reduced gray matter concentration in the inferior frontal orbital gyrus bilaterally (Wald chi-square=11.93, p_FDR<0.01) and, in MDD, with its bilaterally higher activation during valence recognition (Wald chi-square=5.58, p=0.02). Activation of this region, regardless of side, was found to be lower in MDD compared to controls (Wald chi-square=3.88, p=0.049) and to be inversely correlated with depression severity (Wald chi-square=4.65, p=0.03). Our findings support the hypothesis that, in genetically predisposed individuals carrying a high-risk variant of the gene, childhood maltreatment might induce demethylation of FKBP5. This is in turn associated with structural and functional changes in the inferior frontal orbital gyrus, a relevant area for the clinical symptoms of MDD.

Pleiotropic genes in psychiatry: Calcium channels and the stress-related FKBP5 gene in antidepressant resistance

A candidate gene and a genome-wide approach were combined to study the pharmacogenetics of antidepressant response and resistance. Investigated genes were selected on the basis of pleiotropic effect across psychiatric phenotypes in previous genome-wide association studies and involvement in antidepressant response. Three samples with major depressive disorder (total=671) were genotyped for 44 SNPs in 8 candidate genes (CACNA1C, CACNB2, ANK3, GRM7, TCF4, ITIH3, SYNE1, FKBP5). Phenotypes were response/remission after 4weeks of treatment and treatment-resistant depression (TRD). Genome-wide data from STAR*D were used to replicate findings for response/remission (n=1409) and TRD (n=620). Pathways including the most promising candidate genes were investigated in STAR*D for involvement in TRD. FKBP5 polymorphisms showed replicated but nominal associations with response, remission or TRD. CACNA1C rs1006737 and rs10848635 were the only polymorphisms that survived multiple-testing correction. In STAR*D the best pathway associated with TRD included CACNA1C (GO:0006942, permutated p=0.15). Machine learning models showed that independent SNPs in this pathway predicted TRD with a mean sensitivity of 0.83 and specificity of 0.56 after 10-fold cross validation repeated 100 times. FKBP5 polymorphisms appear good candidates for inclusion in antidepressant pharmacogenetic tests. Pathways including the CACNA1C gene may be involved in TRD and they may provide the base for developing multi-marker predictors of TRD.

Association of the Polygenic Scores for Personality Traits and Response to Selective Serotonin Reuptake Inhibitors in Patients with Major Depressive Disorder

Studies reported a strong genetic correlation between the Big Five personality traits and major depressive disorder (MDD). Moreover, personality traits are thought to be associated with response to antidepressants treatment that might partly be mediated by genetic factors. In this study, we examined whether polygenic scores (PGSs) derived from the Big Five personality traits predict treatment response and remission in patients with MDD who were prescribed selective serotonin reuptake inhibitors (SSRIs). In addition, we performed meta-analyses of genome-wide association studies (GWASs) on these traits to identify genetic variants underpinning the cross-trait polygenic association. The PGS analysis was performed using data from two cohorts: the Pharmacogenomics Research Network Antidepressant Medication Pharmacogenomic Study (PGRN-AMPS, n = 529) and the International SSRI Pharmacogenomics Consortium (ISPC, n = 865). The cross-trait GWAS meta-analyses were conducted by combining GWAS summary statistics on SSRIs treatment outcome and on the personality traits. The results showed that the PGS for openness and neuroticism were associated with SSRIs treatment outcomes at p < 0.05 across P_T thresholds in both cohorts. A significant association was also found between the PGS for conscientiousness and SSRIs treatment response in the PGRN-AMPS sample. In the cross-trait GWAS meta-analyses, we identified eight loci associated with (a) SSRIs response and conscientiousness near YEATS4 gene and (b) SSRI remission and neuroticism eight loci near PRAG1, MSRA, XKR6, ELAVL2, PLXNC1, PLEKHM1, and BRUNOL4 genes. An assessment of a polygenic load for personality traits may assist in conjunction with clinical data to predict whether MDD patients might respond favorably to SSRIs.

Pharmacogenomics and Biomarkers of Depression

The standard of care for antidepressant treatment in major depressive disorder (MDD) is a trial-and-error approach. Patients often have to undergo multiple medication trials for weeks to months before finding an effective treatment. Clinical factors such as severity of baseline symptoms and the presence of specific individual (anhedonia or insomnia) or cluster (atypical, melancholic, or anxious) of symptoms are commonly used without any evidence of their utility in selecting among currently available antidepressants. Genomic and proteomic biomarker have gained recent attention for their potential in informing antidepressant medication selection. In this report, we have reviewed some of the major pharmacogenomics studies along with individual genetic and proteomic biomarker of antidepressant response. Additionally, we have reviewed the blood-based protein biomarkers that can inform selection of one antidepressant over another. Among all currently available biomarkers, C-reactive protein (CRP) appears to be the most promising and pragmatic choice. Low CRP (<1 mg/L) in patients with MDD predicts better response to escitalopram while higher levels are associated with better response to noradrenergic/dopaminergic antidepressants. Future studies are needed to demonstrate the superiority of a CRP-based treatment assignment over high-quality measurement-based care in real-world clinical practices.

The FKBP51 Glucocorticoid Receptor Co-Chaperone: Regulation, Function, and Implications in Health and Disease

Among the chaperones and co-chaperones regulating the glucocorticoid receptor (GR), FK506 binding protein (FKBP) 51 is the most intensely investigated across different disciplines. This review provides an update on the role of the different co-chaperones of Hsp70 and Hsp90 in the regulation of GR function. The development leading to the focus on FKBP51 is outlined. Further, a survey of the vast literature on the mechanism and function of FKBP51 is provided. This includes its structure and biochemical function, its regulation on different levels—transcription, post-transcription, and post-translation—and its function in signaling pathways. The evidence portraying FKBP51 as a scaffolding protein organizing protein complexes rather than a chaperone contributing to the folding of individual proteins is collated. Finally, FKBP51’s involvement in physiology and disease is outlined, and the promising efforts in developing drugs targeting FKBP51 are discussed.

Pharmacogenomics in the treatment of mood disorders: Strategies and Opportunities for personalized psychiatry

Personalized medicine (personalized psychiatry in a specific setting) is a new model towards individualized care, in which knowledge from genomics and other omic pillars (microbiome, epigenomes, proteome, and metabolome) will be combined with clinical data to guide efforts to new drug development and targeted prescription of the existing treatment options. In this review, we summarize pharmacogenomic studies in mood disorders that may lay the foundation towards personalized psychiatry. In addition, we have discussed the possible strategies to integrate data from omic pillars as a future path to personalized psychiatry. So far, the progress of uncovering single nucleotide polymorphisms (SNPs) underpinning treatment efficacy in mood disorders (e.g., SNPs associated with selective serotonin re-uptake inhibitors or lithium treatment response in patients with bipolar disorder and major depressive disorder) are encouraging, but not adequate. Genetic studies have pointed to a number of SNPs located at candidate genes that possibly influence response to; (a) antidepressants COMT, HTR2A, HTR1A, CNR1, SLC6A4, NPY, MAOA, IL1B, GRIK4, BDNF, GNB3, FKBP5, CYP2D6, CYP2C19, and ABCB1 and (b) mood stabilizers (lithium) 5-HTT, TPH, DRD1, FYN, INPP1, CREB1, BDNF, GSK3β, ARNTL, TIM, DPB, NR3C1, BCR, XBP1, and CACNG2. We suggest three alternative and complementary strategies to implement knowledge gained from pharmacogenomic studies. The first strategy can be to implement diagnostic, therapeutic, or prognostic genetic testing based on candidate genes or gene products. The second alternative is an integrative analysis (systems genomics approach) to combine omics data obtained from the different pillars of omics investigation, including genomics, epigenomes, proteomics, metabolomics and microbiomes. The main goal of system genomics is an identification and understanding of biological pathways, networks, and modules underlying drug-response. The third strategy aims to the development of multivariable diagnostic or prognostic algorithms (tools) combining individual's genomic information (polygenic score) with other predictors (e.g., omics pillars, neuroimaging, and clinical characteristics) to finally predict therapeutic outcomes. An integration of molecular science with that of traditional clinical practice is the way forward to drug discoveries and novel therapeutic approaches and to characterize psychiatric disorders leading to a better predictive, preventive, and personalized medicine (PPPM) in psychiatry. With future advances in the omics technology and methodological developments for data integration, the goal of PPPM in psychiatry is promising.

5-HT2A receptor deficiency alters the metabolic and transcriptional, but not the behavioral, consequences of chronic unpredictable stress

Chronic stress enhances risk for psychiatric disorders, and in animal models is known to evoke depression-like behavior accompanied by perturbed neurohormonal, metabolic, neuroarchitectural and transcriptional changes. Serotonergic neurotransmission, including serotonin_2A (5-HT_2A) receptors, have been implicated in mediating specific aspects of stress-induced responses. Here we investigated the influence of chronic unpredictable stress (CUS) on depression-like behavior, serum metabolic measures, and gene expression in stress-associated neurocircuitry of the prefrontal cortex (PFC) and hippocampus in 5-HT_2A receptor knockout (5-HT2A−/−) and wild-type mice of both sexes. While 5-HT2A−/− male and female mice exhibited a baseline reduced anxiety-like state, this did not alter the onset or severity of behavioral despair during and at the cessation of CUS, indicating that these mice can develop stress-evoked depressive behavior. Analysis of metabolic parameters in serum revealed a CUS-evoked dyslipidemia, which was abrogated in 5-HT2A−/− female mice with a hyperlipidemic baseline phenotype. 5-HT2A−/− male mice in contrast did not exhibit such a baseline shift in their serum lipid profile. Specific stress-responsive genes (Crh, Crhr1, Nr3c1, and Nr3c2), trophic factors (Bdnf, Igf1) and immediate early genes (IEGs) (Arc, Fos, Fosb, Egr1-4) in the PFC and hippocampus were altered in 5-HT2A−/− mice both under baseline and CUS conditions. Our results support a role for the 5-HT_2A receptor in specific metabolic and transcriptional, but not behavioral, consequences of CUS, and highlight that the contribution of the 5-HT_2A receptor to stress-evoked changes is sexually dimorphic.

BDNF Val66Met Genotype Interacts With a History of Simulated Stress Exposure to Regulate Sensorimotor Gating and Startle Reactivity

Reduced expression of Brain-Derived Neurotrophic Factor (BDNF) has been implicated in the pathophysiology of schizophrenia. The BDNF Val66Met polymorphism, which results in deficient activity-dependent secretion of BDNF, is associated with clinical features of schizophrenia. We investigated the effect of this polymorphism on Prepulse Inhibition (PPI), a translational model of sensorimotor gating which is disrupted in schizophrenia. We utilized humanized BDNFVal66Met (hBDNFVal66Met) mice which have been modified to carry the Val66Met polymorphism, as well as express humanized BDNF in vivo. We also studied the long-term effect of chronic corticosterone (CORT) exposure in these animals as a model of history of stress. PPI was assessed at 30ms and 100ms interstimulus intervals (ISI). Analysis of PPI at the commonly used 100ms ISI identified that, irrespective of CORT treatment, the hBDNFVal/Met genotype was associated with significantly reduced PPI. In contrast, PPI was not different between hBDNFMet/Met and hBDNFVal/Val genotype mice. At the 30ms ISI, CORT treatment selectively disrupted sensorimotor gating of hBDNFVal/Met heterozygote mice but not hBDNFVal/Val or hBDNFMet/Met mice. Analysis of startle reactivity revealed that chronic CORT reduced startle reactivity of hBDNFVal/Val male mice by 51%. However, this was independent of the effect of CORT on PPI. In summary, we provide evidence of a distinct BDNFVal66Met heterozygote-specific phenotype using the sensorimotor gating endophenotype of schizophrenia. These data have important implications for clinical studies where, if possible, the BDNFVal/Met heterozygote genotype should be distinguished from the BDNFMet/Met genotype.

Genetic Studies on the Tripartite Glutamate Synapse in the Pathophysiology and Therapeutics of Mood Disorders

Both bipolar disorder (BD) and major depressive disorder (MDD) have high morbidity and share a genetic background. Treatment options for these mood disorders are currently suboptimal for many patients; however, specific genetic variables may be involved in both pathophysiology and response to treatment. Agents such as the glutamatergic modulator ketamine are effective in treatment-resistant mood disorders, underscoring the potential importance of the glutamatergic system as a target for improved therapeutics. Here we review genetic studies linking the glutamatergic system to the pathophysiology and therapeutics of mood disorders. We screened 763 original genetic studies of BD or MDD that investigated genes encoding targets of the pathway/mediators related to the so-called tripartite glutamate synapse, including pre- and post-synaptic neurons and glial cells; 60 papers were included in this review. The findings suggest the involvement of glutamate-related genes in risk for mood disorders, treatment response, and phenotypic characteristics, although there was no consistent evidence for a specific gene. Target genes of high interest included GRIA3 and GRIK2 (which likely play a role in emergent suicidal ideation after antidepressant treatment), GRIK4 (which may influence treatment response), and GRM7 (which potentially affects risk for mood disorders). There was stronger evidence that glutamate-related genes influence risk for BD compared with MDD. Taken together, the studies show a preliminary relationship between glutamate-related genes and risk for mood disorders, suicide, and treatment response, particularly with regard to targets on metabotropic and ionotropic receptors.

Single nucleotide polymorphisms in the FcγR3A and TAP1 genes impact ADCC in cynomolgus monkey PBMCs

Phenotypic variability is often observed in cynomolgus monkeys on preclinical studies and may, in part, be driven by genetic variability. However, the role of monkey genetic variation remains largely unexplored in the context of drug response. This study evaluated genetic variation in cynomolgus monkey FcγR3A and TAP1 genes and the potential impact of identified polymorphisms on antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro. Studies in humans have demonstrated that a single nucleotide polymorphism (SNP), F158V, in FcγR3A can influence response to rituximab through altered ADCC and that SNPs in TAP1/2 decrease natural killer (NK) cell activity against major histocompatibility complex (MHC) class I deficient cells, potentially through altered ADCC. Monkeys were genotyped for FcγR3A and TAP1 SNPs, and ADCC was assessed in vitro using peripheral blood mononuclear cells (PBMCs) treated with trastuzumab in the presence of NCI-N87 cells. FcγR3A g.1134A>C (exonic S42R), FcγR3A g.5027A>G (intronic), and TAP1 g.1A>G (start codon loss) SNPs were all significantly associated with decreased ADCC for at least one trastuzumab concentration ≥0.0001 μM when compared with wild type (WT). Regression analysis demonstrated significant association of the SNP-SNP pairs FcγR3A g.1134A>C/TAP1 g.1A>G and FcγR3A g.5027A>G/TAP1 g.1A>G with a combinatorial decrease on ADCC. Mechanisms underlying the decreased ADCC were investigated by measuring FcγR3A/IgG binding affinity and expression of FcγR3A and TAP1 in PBMCs; however, no functional associations were observed. These data demonstrate that genetic variation in cynomolgus monkeys is reflective of known human genetic variation and may potentially contribute to variable drug response in preclinical studies.

Consensus paper of the WFSBP Task Force on Genetics: Genetics, epigenetics and gene expression markers of major depressive disorder and antidepressant response

Major depressive disorder (MDD) is a heritable disease with a heavy personal and socio-economic burden. Antidepressants of different classes are prescribed to treat MDD, but reliable and reproducible markers of efficacy are not available for clinical use. Further complicating treatment, the diagnosis of MDD is not guided by objective criteria, resulting in the risk of under- or overtreatment. A number of markers of MDD and antidepressant response have been investigated at the genetic, epigenetic, gene expression and protein levels. Polymorphisms in genes involved in antidepressant metabolism (cytochrome P450 isoenzymes), antidepressant transport (ABCB1), glucocorticoid signalling (FKBP5) and serotonin neurotransmission (SLC6A4 and HTR2A) were among those included in the first pharmacogenetic assays that have been tested for clinical applicability. The results of these investigations were encouraging when examining patient-outcome improvement. Furthermore, a nine-serum biomarker panel (including BDNF, cortisol and soluble TNF-α receptor type II) showed good sensitivity and specificity in differentiating between MDD and healthy controls. These first diagnostic and response-predictive tests for MDD provided a source of optimism for future clinical applications. However, such findings should be considered very carefully because their benefit/cost ratio and clinical indications were not clearly demonstrated. Future tests may include combinations of different types of biomarkers and be specific for MDD subtypes or pathological dimensions.

Pharmacogenetics and Imaging-Pharmacogenetics of Antidepressant Response: Towards Translational Strategies

Genetic variation underlies both the response to antidepressant treatment and the occurrence of side effects. Over the past two decades, a number of pharmacogenetic variants, among these the SCL6A4, BDNF, FKBP5, GNB3, GRIK4, and ABCB1 genes, have come to the forefront in this regard. However, small effects sizes, mixed results in independent samples, and conflicting meta-analyses results led to inherent difficulties in the field of pharmacogenetics translating these findings into clinical practice. Nearly all antidepressant pharmacogenetic variants have potentially pleiotropic effects in which they are associated with major depressive disorder, intermediate phenotypes involved in emotional processes, and brain areas affected by antidepressant treatment. The purpose of this article is to provide a comprehensive review of the advances made in the field of pharmacogenetics of antidepressant efficacy and side effects, imaging findings of antidepressant response, and the latest results in the expanding field of imaging-pharmacogenetics studies. We suggest there is mounting evidence that genetic factors exert their impact on treatment response by influencing brain structural and functional changes during antidepressant treatment, and combining neuroimaging and genetic methods may be a more powerful way to detect biological mechanisms of response than either method alone. The most promising imaging-pharmacogenetics findings exist for the SCL6A4 gene, with converging associations with antidepressant response, frontolimbic predictors of affective symptoms, and normalization of frontolimbic activity following antidepressant treatment. More research is required before imaging-pharmacogenetics informed personalized medicine can be applied to antidepressant treatment; nevertheless, inroads have been made towards assessing genetic and neuroanatomical liability and potential clinical application.

Influence of GRIK4 genetic variants on the electroconvulsive therapy response

Several lines of evidence have shown the involvement of the glutamatergic system in the function of electroconvulsive therapy (ECT). In particular, patients with treatment resistant depression (TRD) and chronic depression have lower levels of glutamate/glutamine than controls, and ECT can reverse this deficit. Genetic factors might contribute to modulating the mechanisms underlying ECT. This study aimed to evaluate the relationship between three polymorphisms (rs1954787, rs4936554 and rs11218030) of the glutamate receptor ionotropic kainate 4 (GRIK4) gene and responsiveness to ECT treatment in a sample of one hundred individuals, TRD or depressive Bipolar Disorder patients resistant to pharmacological treatments. The results revealed that GRIK4 variants were significantly associated with the response to ECT. In particular, we found that patients carrying the G allele of the GRIK4 rs11218030 had a significantly poorer response to ECT (p=2.71×10(-4)), showing five times the risk of relapse after ECT compared to the AA homozygotes. Analogously, patients carrying the GG rs1954787 genotype and rs4936554A allele carriers presented a double risk of lack of response after ECT (p=0.013 and p=0.040, respectively). In conclusion, the current study provides new evidence, indicating that some GRIK4 variants modulate the response to ECT in patients with depression resistant to treatment, suggesting a role for kainate receptor modulation.

Serotonin pathway polymorphisms and the treatment of major depressive disorder and anxiety disorders

While antidepressants are widely used to treat major depressive disorder and anxiety disorders, only half of the patients will respond to antidepressant treatment and only a third of patients will experience a remission of symptoms. Identification of genetic biomarkers that predict antidepressant treatment response could thus greatly improve current clinical practice by providing guidance on which drug to use for which patient. Most antidepressant drugs for the treatment of depression and anxiety disorders have effects on the serotonergic neurotransmitter system; thus, genetic polymorphisms in the genes involved in this pathway represent logical candidates for investigation. This article reviews recent findings on the pharmacogenetics of antidepressant drugs with a focus on serotonergic pathway polymorphisms and discusses future clinical applications.

Genetic dysfunction of serotonin 2A receptor hampers response to antidepressant drugs: A translational approach

Pharmacological studies have yielded valuable insights into the role of the serotonin 2A (5-HT2A) receptor in major depressive disorder (MDD) and antidepressant drugs (ADs) response. However, it is still unknown whether genetic variants in the HTR2A gene affect the therapeutic outcome of ADs and the mechanism underlying the regulation of such response remains poorly described. In this context, a translational human-mouse study offers a unique opportunity to address the possibility that variations in the HTR2A gene may represent a relevant marker to predict the efficacy of ADs. In a first part of this study, we investigated in depressed patients the effect of three HTR2A single nucleotide polymorphisms (SNPs), selected for their potential functional consequences on 5-HT2A receptor (rs6313, rs6314 and rs7333412), on response and remission rates after 3 months of antidepressant treatments. We also explored the consequences of the constitutive genetic inactivation of the 5-HT2A receptor (i.e. in 5-HT2A(-/-) mice) on the activity of acute and prolonged administration of SSRIs. Our clinical data indicate that GG patients for the rs7333412 SNP were less prone to respond to ADs than AA/AG patients. In the preclinical study, we demonstrated that the 5-HT2A receptor exerts an inhibitory influence on the neuronal activity of the serotonergic system after acute administration of SSRIs. However, while the chronic administration of the SSRIs escitalopram or fluoxetine elicited a progressive increased in the firing rate of 5-HT neurons in 5-HT2A(+/+) mice, it failed to do so in 5-HT2A(-/-) mutants. These electrophysiological impairments were associated with a decreased ability of the chronic administration of fluoxetine to stimulate hippocampal plasticity and to produce antidepressant-like activities. Genetic loss of the 5-HT2A receptor compromised the activity of chronic treatment with SSRIs, making this receptor a putative marker to predict ADs response.