Meenal Gupta

Association studies of catechol-O-methyltransferase (COMT) gene with schizophrenia and response to antipsychotic treatment

AIM We investigated the catechol-O-methyltrasferase (COMT) gene, which is a strong functional and positional candidate gene for schizophrenia and therapeutic response to antipsychotic medication. MATERIALS & METHODS Single-locus as well as detailed haplotype-based association analysis of the COMT gene with schizophrenia and antipsychotic treatment response was carried out using seven COMT polymorphisms in 398 schizophrenia patients and 241 healthy individuals from a homogeneous south Indian population. Further responsiveness to risperidone treatment was assessed in 117 schizophrenia patients using Clinical Global Impressions (CGI). A total of 69 patients with a CGI score of 2 or less met the criteria of good responders and 48 were patients who continued to have a score of 3 and above and were classified as poor responders to risperidone treatment. RESULTS The association of SNP rs4680 with schizophrenia did not remain significant after adjusting for multiple testing. Haplotype analysis showed highly significant association of seven COMT marker haplotypes with schizophrenia (CLUMP T4 p-value = 0.0001). Our results also demonstrated initial significant allelic associations of two SNPs with drug response (rs4633: chi(2) = 4.36, p-value = 0.036, OR: 1.80, 95% CI: 1.03-3.15; and rs4680: chi(2) = 4.02, p-value = 0.044, OR: 1.76, 95% CI: 1.01-3.06) before multiple correction. We employed two-marker sliding window analysis for haplotype association and observed a significant association of markers located between intron 1 and intron 2 (rs737865, rs6269: CLUMP T4 p-value = 0.021); and in exon 4 (rs4818, rs4680: CLUMP T4 p-value = 0.028) with drug response. CONCLUSION The present study thus indicates that the interacting effects within the COMT gene polymorphisms may influence the disease status and response to risperidone in schizophrenia patients. However, the study needs to be replicated in a larger sample set for confirmation, followed by functional studies.

Genetic susceptibility to schizophrenia: role of dopaminergic pathway gene polymorphisms

AIM We investigated 16 polymorphisms from three genes, dopamine receptor D2 (DRD2), catechol-O-methyl transferase (COMT) and brain derived neurotrophic factor (BDNF), which are involved in the dopaminergic pathways, and have been reported to be associated with susceptibility to schizophrenia and response to antipsychotic therapy. MATERIALS & METHODS Single-locus association analyses of these polymorphisms were carried out in 254 patients with schizophrenia and 225 controls, all of southern Indian origin. Additionally, multifactor-dimensionality reduction analysis was performed in 422 samples (243 cases and 179 controls) to examine the gene-gene interactions and to identify combinations of multilocus genotypes associated with either high or low risk for the disease. RESULTS Our results demonstrated initial significant associations of two SNPs for DRD2 (rs11608185, genotype: chi(2) = 6.29, p-value = 0.043; rs6275, genotype: chi(2) = 8.91, p-value = 0.011), and one SNP in the COMT gene (rs4680, genotype: chi(2) = 6.67, p-value = 0.035 and allele: chi(2) = 4.75, p-value = 0.029; odds ratio: 1.33, 95% confidence interval: 1.02-1.73), but not after correction for multiple comparisons indicating a weak association of individual markers of DRD2 and COMT with schizophrenia. Multifactor-dimensionality reduction analysis suggested a two locus model (rs6275/DRD2 and rs4680/COMT) as the best model for gene-gene interaction with 90% cross-validation consistency and 42.42% prediction error in predicting disease risk among schizophrenia patients. CONCLUSION The present study thus emphasizes the need for multigene interaction studies in complex disorders such as schizophrenia and to understand response to drug treatment, which could lead to a targeted and more effective treatment.

Genetic profile of patients with epilepsy on first-line antiepileptic drugs and potential directions for personalized treatment

BACKGROUND The first-line antiepileptic drugs, although affordable and effective in the control of seizures, are associated with adverse drug effects, and there is large interindividual variability in the appropriate dose at which patients respond favorably. This variability may partly be explained by functional consequences of genetic polymorphisms in the drug-metabolizing enzymes, such as the CYP450 family, microsomal epoxide hydrolase and UDP-glucuronosyltransferases, drug transporters, mainly ATP-binding cassette transporters, and drug targets, including sodium channels. The purpose of this study was to determine the allele and genotype frequencies of such genetic variants in patients with epilepsy from North India administered first-line antiepileptic drugs, such as phenobarbitone, phenytoin, carbamazepine and valproic acid, and compare them with worldwide epilepsy populations. MATERIALS & METHODS SNP screening of 19 functional variants from 12 genes in 392 patients with epilepsy was carried out, and the patients were classified with respect to the metabolizing rate of their drug-metabolizing enzymes, efflux rate of drug transporters and sensitivity of drug targets. RESULTS A total of 16 SNPs were found to be polymorphic, and the allelic frequencies for these SNPs were in conformance with Hardy-Weinberg equilibrium. Among all the polymorphisms studied, functional variants from genes encoding CYP2C19, EPHX1, ABCB1 and SCN1A were highly polymorphic in North Indian epilepsy patients, and might account for differential drug response to first-line antiepileptic drugs. CONCLUSION Interethnic differences were elucidated for several polymorphisms that might be responsible for differential serum drug levels and optimal dose requirement for efficacious treatment.

Genetic polymorphisms in sex hormone metabolizing genes and drug response in women with epilepsy

AIMS It is hypothesized that functionally relevant polymorphisms in genes encoding metabolizing enzymes of sex steroids may influence drug response by directly predisposing women with epilepsy to seizure exacerbation. An alteration in estradiol:progesterone ratio is believed to play a role in seizure occurrence in women. CYP1A1 is a key enzyme involved in the metabolism of estradiol, with variants of the CYP1A1 gene having been reported to play a role in the alteration of sex hormone metabolism in women. The objective of the present study was to test for the association of genetic variants in CYP1A1 with seizure recurrence in patients diagnosed with epilepsy. MATERIALS & METHODS In the study, the association of five variants in CYP1A1 with seizure control in 228 patients with epilepsy on first-line antiepileptic drug therapy for a minimum period of 12 months was investigated. RESULTS A significant association of an intronic SNP, IVS1 +606C>A (rs2606345), with respect to seizure recurrence (genotypic: p = 3.3 × 10(-4); allelic: p = 7.2 × 10(-4); OR: 2.86; 95% CI: 1.5-5.3) in women with epilepsy from North India was observed. CONCLUSION Since CYP1A1 is not involved in the metabolism of any of the first-line antiepileptic drugs, these results imply that variants from genes encoding sex hormone metabolizing enzymes might act as markers for predicting response to antiepileptic drug therapy in women with epilepsy.

Genetic studies indicate a potential target 5-HTR3B for Drug Therapy in Schizophrenia Patients†‡

Genetic Studies Indicate a Potential Target 5-HTR3B for Drug Therapy in Schizophrenia Patients Meenal Gupta, Sanjeev Jain, Nagaraj Moily, Harpreet Kaur, Ajay Jajodia, Meera Purushottam, and Ritushree Kukreti* Genomics and Molecular Medicine, Institute of Genomics and Integrative Biology (Council of Scientific and Industrial Research), Delhi, India Molecular Genetic Laboratory, Department of Psychiatry, National Institute of Mental Health and Neuro Sciences, Bangalore, India

Challenges and recommendations for conducting epidemiological studies in the field of epilepsy pharmacogenetics

Epilepsy is one of the most prevalent neurological disorders, afflicting approximately 50 million Indians. Owing to affordability and easy availability, use of first-generation antiepileptic drugs (AEDs) is heavily encouraged for the treatment of epilepsy in resource-limited countries such as India. Although first-generation AEDs are at par with second-generation AEDs in terms of efficacy, adverse drug reactions (ADRs) are quite common with them. This could be attributed to the inferior pharmacokinetic parameters such as nonlinear metabolism, narrow therapeutic index and formation of toxic intermediates. In addition, epilepsy patients may differ in the pharmacokinetic and pharmacodynamic profiles, with about 1/3rd of the population failing to respond to treatment. A proportion of this interindividual variability in response may be explained by genetic heterogeneity in the activity and expression of the network of proteins such as metabolizing enzymes, transporters and targets of AEDs. Over the last two decades, a considerable effort has been made by the scientific community for unraveling this genetic basis of variable response to AEDs. However, there have been inconsistencies in such genetic association studies conducted across different territories of the world. There could be several reasons underlying the poor replicability of these studies, mainly nonuniform phenotypic definitions, poor sample size and interethnic variability. In the present review article, we provide an overview of heterogeneity in study designs for conducting pharmacogenetic studies. In addition, critical recommendations required for overcoming such challenges imposed by pharmacogenetic epidemiological studies have been briefly discussed.

Pharmacogenomics and treatment for dementia induced by Alzheimer's disease

Pharmacogenomics is the study of interindividual genetic variability, which plays a significant role in defining drug response and toxicity. As research has graduated from studying single candidate genes to whole-genome scans, pharmacogenomics is beginning to make its impact on the therapeutics of complex CNS disorders, such as schizophrenia, Parkinsons disease and Alzheimers disease. Alzheimers disease is a progressive complex disorder, where genetic predisposition interacts with environmental factors. With conventional therapeutics only providing symptomatic treatment, the current focus of the pharmaceutical industry is on novel strategies with an etiopathogenic orientation. In this review, we have summarized the current knowledge of pathogenetic mechanisms of Alzheimers disease, with a focus on the known relevant molecules and the potential of pharmacogenomics in translating this knowledge of human genome variability into efficacious and safer therapeutics.

Association of GRIN1, ABCB1, and DRD4 genes and response to antipsychotic drug treatment in schizophrenia.

Department of Biotechnology, School of Life Sciences, Department of Psychiatry, Kasturba Medical College, Manipal University, Manipal, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka and CSIRInstitute of Genomics and Integrative Biology, New Delhi, India Correspondence to Kapaettu Satyamoorthy, PhD, Department of Biotechnology, School of Life Sciences, Manipal University, Planetarium Complex, Manipal 576104, Karnataka, India Tel: + 91 82