Contribution of allelic variations in transporters to the phenotype of drug response

Catecholamine pathway polymorphisms and antidepressant response

INTRODUCTION

Genes that regulate the catecholamine metabolism pathways are potential targets for research in the antidepressant treatment response. This study was intended to determine whether antidepressant responses to selective serotonin reuptake inhibitors (SSRIs) are associated with genetic polymorphisms of the tyrosine or tryptophan gene in Chinese major depressive disorder (MDD) patients.

METHODS

A total of 290 MDD patients were recruited and received a 6-week SSRIs randomized double-blinded treatment. Allele, genotype, and haplotype frequencies were compared between responders and nonresponders in catecholamine genes.

RESULTS

Genotype frequency of the rs1800544 polymorphism in the DRD4 gene was significantly different between responders and nonresponders after false discovery rate correction (P = 0.042). The frequency of the DRD4 rs1800544 CG genotype was significantly higher (P = 0.003) in responders (51.4%) than in nonresponders (35.8%), and patients with the CG genotype showed an 81.7% response rate. In comparison, the response rates were 73.9% and 52.2% in patients with the GG genotype and the CC genotype, respectively. The frequencies of the DRD4 rs1800544 CC and GG genotypes were significantly lower (P = 0.003) in responders (7.7%, 40.9%) than in the nonresponders (19.4%, 44.8%). No significant difference was found between two groups either in genotype or allele frequencies of single nucleotide polymorphisms in the TPH, SLC6A2, SLC6A3, or DRD2 genes. No significant difference was found between two groups in TPH, SLC6A2, SLC6A3, DRD2, orDRD4 gene haplotypes.

DISCUSSION

Polymorphisms of the DRD4 gene appear to be associated with SSRI treatment response in Chinese MDD patients.

Association between interleukin 4 gene intron 3 VNTR polymorphism and recurrent aphthous stomatitis in a cohort of Turkish patients

OBJECTIVE

Recurrent aphthous stomatitis (RAS) is one of the most common oral mucosal diseases, with a multifactorial etiopathogenesis, an interaction between predisposing factors and/or systemic conditions and immunological components in genetically predisposed subjects. Although there is no clear genetic mode of inheritance, there is evidence that inheritance of specific gene polymorphisms may predispose individuals to RAS. The purpose of the present study was to investigate a possible association between the functional interleukin 4 (IL4) VNTR genetic polymorphism and RAS in a sample of Turkish patients.

METHODS

The study included 145 unrelated patients with a clinical diagnosis of RAS and 150 unrelated healthy controls. Genomic DNA was isolated and IL4 gene 70 bp VNTR polymorphism determined by using polymerase chain reaction (PCR) with specific primers.

RESULTS

The distribution of genotype and allele frequencies of IL4 gene intron 3 VNTR polymorphism was statistically different between RAS patients and control group (p<0.0001 and p<0.0001, respectively) P2P2 genotype and P2 allele were also found to be protective with a lower risk for susceptibility to RAS (p<0.0001).

CONCLUSION

The results of this study suggest that intron 3 VNTR polymorphism in the IL4 gene is associated with RAS susceptibility in Turkish population.

Prenatal health behaviors and postpartum depression: is there an association?

Postpartum depression is a prevalent mental disorder; however, scarce research has examined its association with prenatal health behaviors. This study investigated the associations of cigarette smoking, caffeine intake, and vitamin intake during pregnancy with postpartum depressive symptoms at 8 weeks after childbirth. Using a prospective cohort study design, participants were recruited from the postpartum floor at a hospital for women and newborns located in a northeastern city, from 2005 through 2008. Eligible women who were at least 18 years old and spoke English were interviewed in person while hospitalized for childbirth (N = 662). A follow-up home interview was conducted at 8 weeks postpartum with a 79% response rate (N = 526). Hierarchical regression analyses showed that smoking cigarettes anytime during pregnancy and not taking prenatal vitamins in the first trimester were significantly associated with worse depressive symptoms (Edinburgh Postnatal Depression Scale). Moreover, having a colicky infant, an infant that refuses feedings, being stressed out by parental responsibility, and having difficulty balancing responsibilities were stressors associated with worse depressive symptoms. Primary health care providers should consider evaluating women for risk of postpartum depression during their first prenatal visit, identifying prenatal health behaviors such as smoking and taking prenatal vitamins.

General and comparative efficacy and effectiveness of antidepressants in the acute treatment of depressive disorders: a report by the WPA section of pharmacopsychiatry

Current gold standard approaches to the treatment of depression include pharmacotherapeutic and psychotherapeutic interventions with social support. Due to current controversies concerning the efficacy of antidepressants in randomized controlled trials, the generalizability of study findings to wider clinical practice and the increasing importance of socioeconomic considerations, it seems timely to address the uncertainty of concerned patients and relatives, and their treating psychiatrists and general practitioners. We therefore discuss both the efficacy and clinical effectiveness of antidepressants in the treatment of depressive disorders. We explain and clarify useful measures for assessing clinically meaningful antidepressant treatment effects and the types of studies that are useful for addressing uncertainties. This includes considerations of methodological issues in randomized controlled studies, meta-analyses, and effectiveness studies. Furthermore, we summarize the differential efficacy and effectiveness of antidepressants with distinct pharmacodynamic properties, and differences between studies using antidepressants and/or psychotherapy. We also address the differential effectiveness of antidepressant drugs with differing modes of action and in varying subtypes of depressive disorder. After highlighting the clinical usefulness of treatment algorithms and the divergent biological, psychological, and clinical efforts to predict the effectiveness of antidepressant treatments, we conclude that the spectrum of different antidepressant treatments has broadened over the last few decades. The efficacy and clinical effectiveness of antidepressants is statistically significant, clinically relevant, and proven repeatedly. Further optimization of treatment can be helped by clearly structured treatment algorithms and the implementation of psychotherapeutic interventions. Modern individualized antidepressant treatment is in most cases a well-tolerated and efficacious approach to minimize the negative impact of otherwise potentially devastating and life-threatening outcomes in depressive disorders.

Pharacogenetic effects of dopamine transporter gene polymorphisms on response to chlorpromazine and clozapine and on extrapyramidal syndrome in schizophrenia

A number of studies have investigated the effectiveness of the dopamine transporter (SLC6A3) Gene as an antipsychotic target. However, the focus has mainly been on a 40-bp variable number of a tandem repeat (VNTR) in the 3'-region and results have been inconsistent. To fully evaluate SLC6A3 as a therapeutic antipshycotic target we investigated association of the gene with responses to chlorpromazine and clozapine and with chlorpromazine-induced extrapyramidal syndrome (EPS) in the Chinese schizophrenia population. Six polymorphisms across the whole region of this gene were analyzed, namely rs2652511 (T-844C) and rs2975226 (T-71A) in the 5'-regulatory region, rs2963238 (A1491C) in intron 1, a 30-bp VNTR in intron 8, rs27072 and the 40-bp VNTR in the 3'-region. We found that the polymorphic marker, rs2975226, showed significant association of allele and genotype frequencies with response to clozapine (allele-wise: adjusted p=0.00404; genotype-wise: adjusted p=0.024), and that patients with the T allele had a better response to the drug. The haplotype block constructed from the first three markers near the 5'-region showed significant association with response to clozapine (for haplotype T-T-A: p=0.0085; for haplotype C-A-C: p=0.0092). We did not identify any significant association of the six genetic variants or haplotypes with EPS after Bonferoni correction. Our findings suggest that the 5'-regulatory region of SLC6A3 plays an important role in response to clozapine and that its role in EPS needs to be replicated in a large-scale well designed study.

A pharmacogenetic study of escitalopram in autism spectrum disorders

OBJECTIVE

To determine the effect of serotonin transporter polymorphism promoter region (5-HTTPLR) genotypic variation (low, intermediate, and high expression groups) on response to escitalopram treatment of children and adolescents with autism spectrum disorders (ASDs).

METHOD

The study used a forced titration, open label design, with genotype blind until study completion. Participants were children and adolescents aged 4-17 years of age with a confirmed ASD (autistic disorder, Asperger's disorder, or pervasive developmental disorder, not otherwise specified).

RESULTS

There was an interaction between genotype group and time on the Aberrant Behavior Checklist (ABC) Irritability Subscale (primary outcome variable) (linear maximum marginal likelihood estimation=-4.84, Z=-2.89, SE=1.67, P=0.004). Examination of baseline to last visit revealed that a genotype grouping based on a previous study of platelet 5-HT uptake revealed less response in the genotype group that had S/S genotype for 5-HTTLPR and did not have a diplotype in intron 1 previously shown to be associated with increased platelet 5-HT uptake.

CONCLUSION

This genotype-blind, prospective pharmacogenetic study found the group of subjects with associated with the lowest platelet 5-HT uptake from previous study had the smallest reduction in ABC-Irritability scores after open label treatment with escitalopram. Replication is necessary to confirm these findings.

Application of pharmacogenomics to clinical problems in depression

The goal of this article is to review the literature for evidence supporting an association between polymorphisms within drug target genes and clinical outcomes for treating depression, with a purpose to identify a research area having the most promising potential to be introduced into clinical settings, and thus, discussing the perspectives of genotyping in antidepressant therapy. A total of 67 articles were identified. Polymorphic sites within the serotonin transporter gene promoter, 5-HTTLPR, were the most studied polymorphisms. All except three articles were designed as cohort studies. The other three articles included two meta-analyses and one decision-analytic model. The main finding from these meta-analyses was that the l variant was associated with a better response to selective serotonin reuptake inhibitors. The main conclusion from the decision-analytic model study was that performing genetic testing before prescribing antidepressant treatment may lead to greater numbers of patients experiencing remission early in treatment. Clinical outcomes of genotyping this polymorphism were evaluated by improvement of depression score, odds ratio and absolute risk reduction.