Val Allele Carriers Research Articles

The Risk of Posttraumatic Stress Disorder After Trauma Depends on Traumatic Load and the Catechol- O-Methyltransferase Val 158Met Polymorphism

The risk for posttraumatic stress disorder (PTSD) depends on the number of traumatic event types experienced in a dose-response relationship, but genetic factors are known to also influence the risk of PTSD. The catechol-O-methyltransferase (COMT) Val158Met polymorphism has been found to affect fear extinction and might play a role in the etiology of anxiety disorders. Traumatic load and lifetime and current diagnosis of PTSD and COMT genotype were assessed in a sample of 424 survivors of the Rwandan Genocide living in the Nakivale refugee camp in southwestern Uganda. Higher numbers of different lifetime traumatic event types led to a higher prevalence of lifetime PTSD in a dose-response relationship. However, this effect was modulated by the COMT genotype: whereas Val allele carriers showed the typical dose-response relationship, Met/Met homozygotes exhibited a high risk for PTSD independently of the severity of traumatic load. The present findings indicate a gene-environment interaction between the human COMT Val158Met polymorphism and the number of traumatic event types experienced in the risk of developing PTSD.

COMT genotype and resting brain perfusion in children

Levels of extra-synaptic dopamine in the brain vary as a function of polymorphisms at the val158met locus of the catechol-O-methyltransferase ( COMT) gene. In vivo studies of this polymorphism in the human brain have typically measured patterns of neural activation during dopamine-mediated tasks in adults. This study is the first to investigate the effects of COMT on brain physiology during rest and in children. We used flow-sensitive arterial spin-labeling (ASL) magnetic resonance imaging to examine brain blood flow (CBF) in 42 children. Compared with val-allele carriers, met-allele homozygotes exhibited greater CBF in mesolimbic, mesocortical, and nigrostriatal dopamine (DA) pathways. Higher CBF in DA-rich brain structures reflects COMT-related baseline differences that (1) underlie the selective behavioral advantages associated with each genotype; (2) affect interpretations of previously reported genotype differences in BOLD signal changes; and (3) serve as a foundation for future studies on the effects of COMT on brain development.

Brain-derived neurotrophic factor gene polymorphisms and mirtazapine responses in Koreans with major depression

Brain-derived neurotrophic factor (BDNF) is a candidate molecule for influencing the clinical response to antidepressant treatment. The aims of this study were to determine the relationship between the Val66Met polymorphism in the BDNF gene and the response to mirtazapine in 243 Korean subjects with major depressive disorder (MDD). The reduction in the Hamilton Depression score over the 8-week treatment period was not influenced by BDNF V66M genotypes. A marginal effect of genotype on somatic anxiety score was observed at baseline (P = 0.047 in the dominant model). However, genotype-time interaction had no effect on somatic anxiety score after the 8-week a treatment period. Plasma BDNF levels tended to increase during mirtazapine treatment, although without statistical significance (P = 0.055). After 8 weeks of mirtazapine treatment, plasma BDNF levels were higher in Met allele homozygotes (1499.7 ± 370.6 ng/mL) than in Val allele carriers (649.7 ± 158.5 ng/mL, P = 0.049). Our results do not support the hypothesis that the Val66Met promoter polymorphism in the BDNF gene influences the therapeutic response to mirtazapine in Korean MDD patients. However, our data indicate that this polymorphism results in increased plasma BDNF after mirtazapine treatment.

Study of association of platelet endothelial cell adhesion molecule-1 gene polymorphism with acute myocardial infarction

To investigate the association of single nucleotide polymorphism (SNP) and its haplotypes of platelet endothelial cell adhesion molecule-1 (PECAM-1) gene with susceptibility to acute myocardial infarction (AMI), and to analyze association the serum levels and genotypes of PECAM-1 with AMI. Three SNPs of PECAM-1 gene Leu125Val, Asn563Ser and Gly670Arg were analyzed in 180 patients with AMI and 200 age and sex matched controls, using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) strategy, and the serum level of PECAM-1 was determined by enzyme linked immunosorbent assay (ELISA). Frequency of haplotypes and linkage disequilibrium of PECAM-1 gene in different groups were analyzed by SHEsis programs. The distributions of PECAM-1 gene Asn563Ser and Gly670Arg polymorphisms were not different between AMI and control group (P>0.05), but the PECAM-1 gene Leu125Val polymorphism was significantly different (P<0.05). The relative risk suffered from AMI of Val allele was 1.480 folds of the Leu allele carriers [odds ratio (OR)=1.480, 95% confidence interval (CI): 1.111-1.972, P=0.007]; the serum level of PECAM-1 Val allele carriers was significantly higher than that of noncarriers (P<0.01). With the results of the genotyping analyses, PECAM-1 gene Leu125Val, Asn563Ser and Gly670Arg polymorphisms showed strong linkage disequilibrium, and the Val-Ser-Arg haplotype was associated with a significantly increased risk of AMI as compared with the controls (OR=1.489, 95%CI: 1.118-1.984, P=0.006). PECAM-1 gene Leu125Val polymorphism and its Val-Ser-Arg haplotype are associated with AMI, Val allele is an important genetic susceptibility gene for AMI. The PECAM-1 Val allele carriers may have a higher risk by enhancing the PECAM-1 expression in the pathogenesis of AMI.

Neuroimaging genetics: new perspectives in research on major depression?

Stress-related changes in the hippocampus are influenced by genetic factors. To enhance our understanding of both the interaction between the brain, behaviour and genetics and of biological mechanisms in mood disorders neuroimaging genetics provide a good opportunity. A MEDLINE search was conducted to identify articles on neuroimaging genetics in major depression (MD). Hippocampal volumes were found to be associated with polymorphisms in the promotor region of the serotonin transporter (5-HTTLPR) in patients with MD. Met-allele carriers of the BDNF (val66met) polymorphism had smaller hippocampal volumes in both patients and healthy controls when compared with homozygous val-allele carriers. Polymorphisms of the serotonin transporter (5-HTTLPR) and 5-HT1a receptor are associated with increased amygdala activation investigated with functional MRI in patients with MD. Genetic variants seem to modulate the effects of stress on hippocampal volumes as well as amygdala activity as well as the development of the brain.

GSTP1 Ile105Val polymorphism correlates with progression-free survival in MCRC patients treated with or without irinotecan: a study of the Dutch Colorectal Cancer Group

A Valine residue at position 105 of the GSTP1 protein results in decreased enzyme activity. As nuclear GSTP1 activity decreases irinotecan cytotoxicity, Val-allele carriers may benefit more from irinotecan chemotherapy. Our aim was to investigate the association of GSTP1 genotype with treatment outcome of irinotecan. Progression-free survival (PFS) and toxicity were determined in 267 metastatic colorectal cancer (MCRC) patients who were treated with first-line capecitabine (CAP) plus irinotecan (CAPIRI), or CAP single agent in a prospective randomised phase III trial (CAIRO). GSTP1 genotype was determined by Pyrosequencing. Patients receiving CAP showed a PFS of 6.6 (Ile/Ile), 6.0 (Ile/Val) and 6.5 months (Val/Val); compared to 7.0 (Ile/Ile), 8.8 (Ile/Val) and 9.2 months (Val/Val) with CAPIRI. Median PFS was 2.7 months longer in Val-allele carriers treated with CAPIRI compared to CAP (P=0.005). Patients with the Ile/Ile genotype showed similar PFS with CAPIRI and CAP (7.0 compared to 6.6 months, P=0.972). Toxicity did not differ significantly among genotypes. GSTP1 codon 105 polymorphism may be predictive for the response to irinotecan-based chemotherapy in patients with MCRC, with the Val-allele being associated with a better outcome. Ile/Ile genotype patients do not appear to benefit from the addition of irinotecan to CAP.

The A98V Single Nucleotide Polymorphism (SNP) in Hepatic Nuclear Factor 1 α (HNF-1α) is Associated with Insulin Sensitivity and β-Cell Function

Mutations in the hepatic nuclear factor-1-alpha ( HNF-1alpha) gene is considered as a candidate for the aetiology of type 2 diabetes. The aims of the study was to determine whether two single nucleotide polymorphisms (SNPs) ile27-to-leu and ala98-to-val in the HNF-1alpha gene associate with diabetes, insulin sensitivity as well as beta-cell function. 1 479 subjects of a volunteer sample with increased risk of type 2 diabetes were investigated. They underwent a 75 g oral glucose tolerance test (OGTT) with measurements of plasma glucose, insulin and C-peptide at fasting and at 30, 60, 90 and 120 minutes after the glucose challenge. The HNF-1alpha SNPs, I27L and A98V were genotyped. Patients harbouring the V98 allele exhibited higher serum insulin and C-peptide levels. The heterozygote variant was also associated with decrease in beta-cell function but better insulin sensitivity. No significant differences of any clinical parameters were found for I27L gene variants. Significant associations between the heterozygote A98V genotype and clinical parameters of insulin metabolism were reported but no relationship with type 2 diabetes was obtained. This may be explained by a balancing negative effect on insulin secretion and concomitant positive effect on insulin resistance in Val allele carriers.

Catechol-O-Methyltransferase (COMT) Val158Met Genotype is Associated with BOLD Response as a Function of Task Characteristic

The catechol-O-methyltransferase (COMT) val(158)met single nucleotide polymorphism (rs4680) has been shown to be associated with brain activation during a number of neurocognitive and emotional tasks. The present study evaluated genotypic associations with brain function during measurement of cognitive stability (prosaccades) and plasticity (antisaccades). A total of 36 healthy volunteers were genotyped for rs4680 and underwent functional magnetic resonance imaging (fMRI) at 1.5 T. Individuals with at least one val(158) allele (val(158) carriers, N=24) showed lower blood oxygen level-dependent (BOLD) response in ventromedial and dorsomedial prefrontal cortex during antisaccades compared to val(158) noncarriers, whereas met(158) homozygotes (N=12) showed lower BOLD response in a cluster in the posterior cingulate and precuneus during prosaccades compared to val(158) carriers. These findings suggest that associations of COMT val(158)met genotype with brain function may be mediated by task characteristics. The findings may be compatible with a hypothesis on the role of COMT val(158)met genotype in tonic and phasic dopamine levels in brain and differential effects on cognitive measures of stability (eg prosaccades) and plasticity (eg antisaccades).

Sleep and COMT Polymorphism in ADHD Children: Preliminary Actigraphic Data

To examine whether COMT (catechol-O-methyltransferase) polymorphism modulates aspects of sleep in children diagnosed with attention-deficit/hyperactivity disorder (ADHD). Nightly sleep actigraphic recordings during a double-blind, placebo-controlled, crossover clinical study (1 week of 0.5 mg/kg MPH; 1 week of placebo) were obtained for 34 children, 7.4 to 12 years old, diagnosed with ADHD (DSM-IV). Diagnosis was generated by the Diagnostic Interview Schedule for Children and was confirmed by multidisciplinary consensus. Children who were Val allele carriers had poorer sleep continuity compared with children with the Met-Met genotype while receiving a placebo and while receiving methylphenidate. The findings of the present study support the hypothesis that sleep disturbances in children with ADHD are related to the underlying pathophysiology of the disorder.

Impact of Catechol-O-Methyltransferase on Prefrontal Brain Functioning in Schizophrenia Spectrum Disorders

The enzyme catechol-O-methyltransferase (COMT) has attracted increasing interest regarding a genetic disposition towards schizophrenias and as a modulator of prefrontal brain function. A common SNP in the COMT gene causes a Val to Met transition at AA158/AA108 (Val158Met), resulting in reduced COMT activity in Met allele carriers. An impact of COMT genotype on cognition has been well established; however, the exact nature of this influence has yet to be elucidated. The aim of this study was to determine whether COMT genotype affects an electrophysiological marker of prefrontal activation and neuropsychological frontal lobe measures in schizophrenia. To this end, 56 acutely psychotic in-patients with schizophrenia spectrum disorders were investigated. Patients with the COMT 1947AA (Met/Met) genotype (n=13) were compared to a carefully matched sample of patients with a G1947A (Val/Met) genotype (n=15); matching criteria included patients' age, handedness, gender distribution, diagnosis, and medication status. A small group of six homozygous Val allele carriers was additionally included to allow an assessment of possible gene-dosage effects. P300 amplitudes and latencies, as well as an electrophysiological marker of prefrontal brain function (NoGo-Anteriorization/NGA) and neuropsychological measures (Stroop Test, Verbal Fluency, Trail Making Test) were regarded. Homozygous Met allele carriers had significantly increased NGA values and fronto-central Nogo amplitudes compared to patients with at least one Val allele. They also tended to perform better in the Stroop task, as compared to the matched group of Val/Met patients. These results indicate that COMT genotype exerts a strong impact on prefrontal functioning and executive control in schizophrenia spectrum disorders.