Publications by authors named "Murali Munisamy"

15 Publications

  • Page 1 of 1

Signet ring cell cancer of stomach and gastro-esophageal junction: molecular alterations, stage-stratified treatment approaches, and future challenges.

Langenbecks Arch Surg 2021 Sep 10. Epub 2021 Sep 10.

Department of Pharmacy Practice, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education (MAHE), Manipal, Karnataka, 576104, India.

Purpose: There has been an increase in the incidence of signet ring cell cancer (SRCC) of the stomach and gastro-esophageal junction (GEJ). The multistage carcinogenesis involving genetic and epigenetic aberrations may have a major role in the increasing incidence of SRCC. Although there are numerous studies on the prognostic value of SRCC, they are markedly inconsistent in their results, making it impossible to draw any meaningful conclusions. We aimed to examine the available evidences on molecular alterations and stage-stratified treatment approaches in SRCC of the stomach and GEJ.

Methods: A systematic search was carried out in PubMed. Studies available in English related to SRCC of stomach and gastro-esophageal junction were identified and evaluated.

Results: This study reviewed the current evidence and provided an insight into the molecular alterations, stage-stratified treatment approaches, and future challenges in the management of SRCC of the stomach and GEJ. Specific therapeutic strategies and personalized multimodal treatment have been recommended based on the tumor characteristics of SRCC.

Conclusion: Multistage carcinogenesis involving genetic and epigenetic aberrations in SRCC is interlinked with stage-dependent prognosis. Specific therapeutic strategy and personalized multimodal treatment should be followed based on the tumor characteristics of SRCC. Endoscopic resection, radical surgery, and perioperative chemotherapy should be offered in carefully selected patients based on stage and prognostic stratification. Future studies in genetic and molecular analysis, histopathological classification, and options of multimodality treatment will improve the prognosis and oncological outcomes in SRCC of gastric and GEJ.
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http://dx.doi.org/10.1007/s00423-021-02314-6DOI Listing
September 2021

Prediction of potential drug interactions between repurposed COVID-19 and antitubercular drugs: an integrational approach of drug information software and computational techniques data.

Ther Adv Drug Saf 2021 26;12:20420986211041277. Epub 2021 Aug 26.

Professor and Head, Department of Pharmacy Practice, Coordinator, Centre for Translational Research, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education (MAHE), Manipal 576104, Karnataka, India.

Introduction: Tuberculosis is a major respiratory disease globally with a higher prevalence in Asian and African countries than rest of the world. With a larger population of tuberculosis patients anticipated to be co-infected with COVID-19 infection, an ongoing pandemic, identifying, preventing and managing drug-drug interactions is inevitable for maximizing patient benefits for the current repurposed COVID-19 and antitubercular drugs.

Methods: We assessed the potential drug-drug interactions between repurposed COVID-19 drugs and antitubercular drugs using the drug interaction checker of IBM Micromedex®. Extensive computational studies were performed at a molecular level to validate and understand the drug-drug interactions found from the Micromedex drug interaction checker database at a molecular level. The integrated knowledge derived from Micromedex and computational data was collated and curated for predicting potential drug-drug interactions between repurposed COVID-19 and antitubercular drugs.

Results: A total of 91 potential drug-drug interactions along with their severity and level of documentation were identified from Micromedex between repurposed COVID-19 drugs and antitubercular drugs. We identified 47 pharmacodynamic, 42 pharmacokinetic and 2 unknown DDIs. The majority of our molecular modelling results were in line with drug-drug interaction data obtained from the drug information software. QT prolongation was identified as the most common type of pharmacodynamic drug-drug interaction, whereas drug-drug interactions associated with cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) inhibition and induction were identified as the frequent pharmacokinetic drug-drug interactions. The results suggest antitubercular drugs, particularly rifampin and second-line agents, warrant high alert and monitoring while prescribing with the repurposed COVID-19 drugs.

Conclusion: Predicting these potential drug-drug interactions, particularly related to CYP3A4, P-gp and the human Ether-à-go-go-Related Gene proteins, could be used in clinical settings for screening and management of drug-drug interactions for delivering safer chemotherapeutic tuberculosis and COVID-19 care. The current study provides an initial propulsion for further well-designed pharmacokinetic-pharmacodynamic-based drug-drug interaction studies.

Plain Language Summary: Tuberculosis is a major respiratory disease globally with a higher prevalence in Asian and African countries than rest of the world. With a larger population of tuberculosis patients predicted to be infected with COVID-19 during this period, there is a higher risk for the occurrence of medication interactions between the medicines used for COVID-19 and tuberculosis. Hence, identifying and managing these interactions is vital to ensure the safety of patients undergoing COVID-19 and tuberculosis treatment simultaneously. We studied the major medication interactions that could likely happen between the various medicines that are currently given for COVID-19 and tuberculosis treatment using the medication interaction checker of a drug information software (Micromedex®). In addition, thorough molecular modelling was done to confirm and understand the interactions found from the medication interaction checker database using specific docking software. Molecular docking is a method that predicts the preferred orientation of one medicine molecule to a second molecule, when bound to each other to form a stable complex. Knowledge of the preferred orientation may be used to determine the strength of association or binding affinity between two medicines using scoring functions to determine the extent of the interactions between medicines. The combined knowledge from Micromedex and molecular modelling data was used to properly predict the potential medicine interactions between currently used COVID-19 and antitubercular medicines. We found a total of 91 medication interactions from Micromedex. Majority of our molecular modelling findings matched with the interaction information obtained from the drug information software. QT prolongation, an abnormal heartbeat, was identified as one of the most common interactions. Our findings suggest that antitubercular medicines, mainly rifampin and second-line agents, suggest high alert and scrutiny while prescribing with the repurposed COVID-19 medicines. Our current study highlights the need for further well-designed studies confirming the current information for recommending safe prescribing in patients with both infections.
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http://dx.doi.org/10.1177/20420986211041277DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8404633PMC
August 2021

Biomarkers for Antiplatelet Therapies in Acute Ischemic Stroke: A Clinical Review.

Front Neurol 2021 10;12:667234. Epub 2021 Jun 10.

Department of Neurology, All India Institute of Medical Sciences, New Delhi, India.

Stroke is one of the world's leading causes of disability and death. Antiplatelet agents are administered to acute ischemic stroke patients as secondary prevention. Clopidogrel involves biotransformation by cytochrome P450 (CYP) enzymes into an active metabolite, and single nucleotide polymorphisms (SNPs) can influence the efficacy of this biotransformation. Despite the therapeutic advantages of aspirin, there is significant inter-individual heterogeneity in response to this antiplatelet drug. In this clinical review, the recent advances in the biomarkers of antiplatelet agents in acute ischemic stroke are discussed. The studies reviewed herein highlight the clinical relevance of antiplatelet resistance, pharmacotherapy of antiplatelet agents predicting drug response, strategies for identifying aspirin resistance, pharmacogenetic variants of antiplatelet agents, miRNAs, and extracellular vesicles (EVs) as biomarkers toward the personalized approach in the management of acute ischemic stroke. The precise pathways contributing to antiplatelet resistance are not very well known but are presumably multi-factorial. It is essential to understand the clinical relevance of clopidogrel and aspirin-related single nucleotide polymorphism (SNPs) as potential predictive and prognostic biomarkers. Prasugrel is a next-generation antiplatelet agent that prevents ADP-platelet activation by binding irreversibly to P2Y12 receptor. There are sporadic reports of prasugrel resistance and polymorphisms in the Platelet endothelial aggregation receptor-1 (PEAR1) that may contribute to a change in the pharmacodynamics response. Ticagrelor, a direct-acting P2Y12-receptor antagonist, is easily absorbed and partly metabolized to major AR-C124910XX metabolite (ARC). Ticagrelor's primary active metabolite, ARC124910XX (ARC), is formed via the most abundant hepatic cytochrome P450 (CYP) enzyme, CYP3A4, and CYP3A5. The integration of specific biomarkers, genotype as well as phenotype-related data in antiplatelet therapy stratification in patients with acute ischemic stroke will be of great clinical significance and could be used as a guiding tool for more effective, personalized therapy.
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http://dx.doi.org/10.3389/fneur.2021.667234DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8222621PMC
June 2021

Psychosis susceptibility Zinc Finger Protein 804A (ZNF804A) gene polymorphism in Schizophrenia patients treated with Olanzapine in North Indian population.

Int J Neurosci 2021 Apr 19:1-9. Epub 2021 Apr 19.

Department of Biochemistry, All India Institute of Medical Sciences, Rishikesh, India.

The Zinc finger protein 804 A (ZNF804A) is a potential schizophrenia candidate gene that has emerged from genome-wide association studies. The aim of the study is to investigate whether this gene variant influences the response of positive or negative symptoms to antipsychotic drug olanzapine in North Indian schizophrenia patients. Our study involved 184 unrelated schizophrenia cases (114 males and 70 females; mean age: 52.8 ± 11.6 years) and 300 normal controls (168 males and 132 females; mean age: 54.9 ± 6.9 years). At the start of treatment and after four weeks, we assessed the response of positive and negative symptoms by positive and negative syndrome scale (PANSS). Olanzapine drug level was estimated using HPLC Method and Genotyping was performed using PCR-Snap Shot technique.: Significant differences were observed in the genotype distribution (χ2 = 6.10, d.f. = 2,  = 0.04) and allele frequencies (χ2 = 5.14, d.f. = 1,  = 0.02; odds ratio =0.57, 95% confidence interval =1.09-3.48) between schizophrenia patients and controls group. The improvement of positive and negative schizophrenia symptoms after 4 weeks of treatment with olanzapine was assessed. Patients homozygous for the ZNF804A risk allele for AA show poorer improvement of positive symptoms compared to patients with a protective allele. Our findings indicate that ZNF804A gene polymorphism plays a significant role in the treatment of schizophrenia, suggesting that ZNF804A may be an effective marker for schizophrenia treatment.
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http://dx.doi.org/10.1080/00207454.2021.1916742DOI Listing
April 2021

Pharmacogenetics of ATP binding cassette transporter MDR1(1236C>T) gene polymorphism with glioma patients receiving Temozolomide-based chemoradiation therapy in Indian population.

Pharmacogenomics J 2021 04 15;21(2):262-272. Epub 2021 Feb 15.

Department of Neuro Biochemistry, Neuroscience Centre, All India Institute of Medical Sciences, New Delhi, India.

Temozolomide (TMZ), an alkylating agent with a broad-spectrum antitumor activity, ability to cross blood-brain barrier (BBB), shown to be effective against malignant glioma. This study aims to investigate the effect of 1236C>T (rs1128503) single-nucleotide gene polymorphisms of ABCB1 (MDR1) in north-Indian patients diagnosed with glioma undergoing TMZ-based chemoradiotherapy. Genotyping was performed in 100 patients diagnosed with malignant glioma (50 anaplastic astrocytoma (AA) patients and 50 glioblastoma multiforme (GBM) patients) and 150 age and sex-matched controls by polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) method, followed by sanger sequencing. TMZ plasma levels were analyzed by reverse phase HPLC method. Glioma patient's survival time was analyzed by Kaplan-Meier's curve. Results of MDR1 gene 1236C>T polymorphism showed significant allelic and genotypic frequency association between glioma patients and controls. The plasma TMZ levels between metabolizers group in Grade III and Grade IV were found to be statistically significant (p < 0.05). The mutant genotype (TT) has less survival benefit compared with other genotypes (CT/CC) and the survival difference between AA and GBM was found to be statistically significant (p < 0.05). Though CT and TT polymorphisms have significant association with lower TMZ levels in both Grade III (AA) and IV (GBM) tumors, the survival difference seems to be mainly among patients with Grade III tumors. Our findings suggest that the MDR1 gene polymorphism plays a role in plasma TMZ levels and in survival time of glioma patients and, hence, TMZ therapy in malignant glioma can be predicted by genotyping MDR1 (1236C>T) gene polymorphism.
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http://dx.doi.org/10.1038/s41397-021-00206-yDOI Listing
April 2021

Vitamin D Supplementation in Diabetic Foot Ulcers: A Current Perspective.

Curr Diabetes Rev 2021 ;17(4):512-521

Department of Pharmacy Practice, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka-576104, India.

Introduction: Diabetic foot ulcer (DFU) is a major complication of diabetes mellitus, as it can physically and emotionally impact the person. Its management can be challenging and expensive, depending on the severity of the wound and the presence of infection.

Background: The fat-soluble molecule, vitamin D, has gained great importance ever since its pleiotropism has been recognized. Its efficacy could be attributed to the presence of vitamin D receptors in most of the body tissues. Vitamin D plays a significant role in cell proliferation, differentiation, and immune modulation. It modulates the T and B cells resulting in the suppression of the immunoglobulins, autoimmunity, and inflammation.

Methods: We performed a literature search with the objective to highlight the role of vitamin D in peripheral vascular disease and peripheral neuropathy, which are the major risk factors for DFU, as well as evidences of its role in wound healing and management of DFU.

Results: Preclinical and clinical studies have shown that vitamin D influences multiple phases of wound healing and thereby accelerates the process. It modulates various cells involved in proliferation and remodelling phases. Vitamin D also enhances the expression of antimicrobial peptides that help to eliminate the microbes, as well as suppress the proinflammatory responses while enhancing the anti-inflammatory responses.

Conclusion: This review concludes vitamin D to have a protective role in the immune and vascular system, improve glycaemic outcomes, and wound healing. Therefore, vitamin D could be a preferred adjuvant in the management of DFU.
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http://dx.doi.org/10.2174/1573399816999201012195735DOI Listing
May 2021

Liquid biopsy approaches for pleural effusion in lung cancer patients.

Mol Biol Rep 2020 Oct 7;47(10):8179-8187. Epub 2020 Oct 7.

Department of Pharmacy Practice, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India.

Genomic profiling of tumors has become the mainstay for diagnosis, treatment monitoring and a guide to precision medicine. However, in clinical practice, the detection of driver mutations in tumors has several procedural limitations owing to progressive disease and tumor heterogeneity. The current era of liquid biopsy promises a better solution. This diagnostic utility of liquid biopsy has been demonstrated by numerous studies for the detection of cell-free DNA (cfDNA) in plasma for disease diagnosis, prognosis, and prediction. However, cfDNAs are limited in blood circulation and still hurdles to achieve promising precision medicine. Malignant pleural effusion (MPE) is usually detected in advanced lung malignancy, which is rich in tumor cells. Extracellular vesicles and cfDNAs are the two major targets currently explored using MPE. Therefore, MPE can be used as a source of biomarkers in liquid biopsy for investigating tumor mutations. This review focuses on the liquid biopsy approaches for pleural effusion which may be explored as an alternative source for liquid biopsy in lung cancer patients to diagnose early disease progression.
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http://dx.doi.org/10.1007/s11033-020-05869-7DOI Listing
October 2020

Histone Demethylase KDM5B as a Therapeutic Target for Cancer Therapy.

Cancers (Basel) 2020 Jul 31;12(8). Epub 2020 Jul 31.

Department of Pharmacy Practice, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India.

Lysine-specific demethylase 5B (KDM5B/PLU1/JARID1B) is found to be overexpressed in numerous malignancies, including breast, lung, skin, liver, and prostate cancer. Identification of molecules targeting the KDM5B enzyme could be a potential lead in cancer research. Although many KDM5B inhibitors with promising outcomes have been developed so far, its further application in clinical practice is limited due to toxicity and lack of target specificity. Here, we summarize the significance of targeting KDM5B in anticancer therapy and report the molecular docking studies of some known anti-viral agents, decitabine, entecavir, abacavir, penciclovir, and 3-deazaneplanocin A in the catalytic domain JmjC of KDM5B. These studies show the repurposing potential of identified anti-viral agents in cancer therapy.
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http://dx.doi.org/10.3390/cancers12082121DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7465382PMC
July 2020

Cannabinoids as an Alternative Option for Conventional Analgesics in Cancer Pain Management: A Pharmacogenomics Perspective.

Indian J Palliat Care 2020 Jan-Mar;26(1):129-133. Epub 2020 Jan 28.

Department of Pharmacy Practice, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India.

The global cancer burden is significantly increasing at an alarming rate affecting patients, relatives, communities, and health-care system. Cancer patients require adequate pain relief and palliative care throughout the life course, especially in terminal illness. Although opioid treatment is successful in majority of patients, around 40% do not achieve enough analgesia or are prone to serious side effects and toxicity. The treatment of medical conditions with cannabis and cannabinoid compounds is constantly expanding. This review organizes the current knowledge in the context of SNPs associated with opioids and nonopioids and its clinical consequences in pain management and pharmacogenetic targets of cannabinoids, for use in clinical practice.
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http://dx.doi.org/10.4103/IJPC.IJPC_155_19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7017683PMC
January 2020

Pharmacogenetics of CYP2C19 genetic polymorphism on clopidogrel response in patients with ischemic stroke from Saudi Arabia.

Neurosciences (Riyadh) 2017 01;22(1):31-37

Assistant Professor of Neurology, Department of Neurosciences, College of Medicine, King Khalid University, Abha, Kingdom of Saudi Arabia.

Objective: To elucidate the degree of genetic polymorphisms CYP2C19 (CYP2C19*2, CYP2C19*3) of key drug metabolizing enzymes on the antiplatelet effect of clopidogrel response in patients with acute ischemic stroke from Saudi Arabia.

Methods: A case-control study carried out at Neurology Clinics at Asser Central Hospital, Abha, Kingdom of Saudi Arabia from October 2015 to January 2016 and included 25 stroke patients responding to clopidogrel therapy and 25 stroke patients non responding to clopidogrel monotherapy. After obtaining their informed consent, the blood samples were collected and genotyped for CYP2C19 polymorphisms by the polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP Method). Allele frequencies were derived from genotypic data and platelet aggregation was measured using multiple electrode aggregometry on the multiplate analyser. Chi Square tests, p-values, odds ratio (OR) and corresponding confidence intervals were calculated for each polymorphism.

Results: The CYP2C19*2 (681G>A) and CYP2C19*3 (636 G>A) polymorphism were seen to be in Hardy-Weinberg equilibrium and showed significant allelic and genotypic association between responders and non-responders to clopidogrel (p<0.01). The CYP2C19*2: allelic chi-square=21.49, p=0.000036, OR=5.52 (2.42-12.83); Genotypic Chi-square=10.27, p=0.001, OR=7.88 (1.78-9.73). The CYP2C19*3: Allelic chi-square=11.66, p=0.0006, OR=3.45 (1.57-7.70); genotypic chi-square=4.37, p=0.036, OR=3.69 (0.90-5.81). The variant allele (homozygous and homozygous Mutant) showed significant influence on platelet inhibition and the antiplatelet effect of clopidogrel in ischemic stroke.

Conclusion: Our findings provide certain evidence on the genetic effect of CYP2C19 on clopidogrel responsiveness in stroke patients from Saudi Arabia.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726834PMC
http://dx.doi.org/10.17712/nsj.2017.1.20160303DOI Listing
January 2017

Impact of MTHFR (C677T) gene polymorphism on antiepileptic drug monotherapy in North Indian epileptic population.

Ann Saudi Med 2015 Jan-Feb;35(1):51-7

Murali Munisamy, Asst. Professor, Faculty of Pharmacy,, King Khalid University,, PO Box 1882, Abha 61441,, Saudi Arabia, T: +966551656946,

Background And Objectives: Antiepileptic drugs (AEDs) are known to interfere with homocysteine metabolism. Hyperhomocysteinemia may be a risk factor associated in the long-term treatment with AEDs. Both genetic and non-genetic factors are responsible for hyperhomocysteinemia. MTHFR C677T polymorphism leads to the reduction in enzyme activity and subsequent elevation of plasma homocysteine. This study aimed to investigate the role of MTHFR C677T polymorphism in epileptic patients receiving AEDs as monotherapy (phenytoin, carbamazepine, and sodium valproate) and showing toxicity and non-toxicity, and the impact of AEDs on hyperhomocysteinemia in North Indian population.

Design And Settings: Blood samples for this case-control study were collected from the outpatient department and wards of the Department of Neurosciences at the All India Institute of Medical Sciences, New Delhi, India, between July 2008 and May 2010.

Patients And Methods: In this study, 200 epileptic patients and 100 normal controls were assessed for total homocysteine (tHcy), vitamin B12, and folate levels using enhanced chemiluminescence enzyme immunoassay method (ImmuliteR, 1000 systems, DPC, United States); genotyping of MTHFR C677T was done using polymerase chain reaction-restriction fragment length polymorphism method.

Results: The results showed a significant increase in tHcy levels in epileptic patients with toxicity and non-toxicity than in normal controls (P < .005). The allelic and genotypic distributions were found to be statistically significant in toxicity and non-toxicity groups (P < .05).

Conclusion: The result confirmed that hyperhomocysteinemia is common in adults receiving AED treatment for epilepsy with toxicity and non-toxicity groups. This increase in tHcy is mainly related to low folate and vita.min B12 levels, which are the main determinants for tHcy.
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http://dx.doi.org/10.5144/0256-4947.2015.51DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6152547PMC
March 2016

The effect of uridine diphosphate glucuronosyltransferase (UGT)1A6 genetic polymorphism on valproic acid pharmacokinetics in Indian patients with epilepsy: a pharmacogenetic approach.

Mol Diagn Ther 2013 Oct;17(5):319-26

Department of Neurobiochemistry, Neurosciences Center, All India Institute of Medical Sciences, New Delhi, 110029, India.

Background And Objective: Sodium valproate is a widely prescribed broad-spectrum antiepileptic drug. It shows high inter-individual variability in pharmacokinetics and pharmacodynamics and has a narrow therapeutic range. We evaluated the effects of polymorphic uridine diphosphate glucuronosyltransferase (UGT)1A6 (541A>G, 552A>C) metabolizing enzyme on the pharmacokinetics of sodium valproate in the patients with epilepsy who showed toxicity to therapy.

Methods: Genotype analysis of the patients was made with polymerase chain-restriction fragment length polymorphism (RFLP) with sequencing. Plasma drug concentrations were measured with reversed phase high-performance liquid chromatography (HPLC) and concentration-time data were analyzed by using a non-compartmental approach.

Results: The results of this study suggested a significant genotypic as well as allelic association with valproic acid toxicity for UGT1A6 (541A>G) or UGT1A6 (552A>C) polymorphic enzymes. The elimination half-life (t ½ = 40.2 h) of valproic acid was longer and the clearance rate (CL = 917 ml/h) was lower in the poor metabolizers group of UGT1A6 (552A>C) polymorphism who showed toxicity than in the intermediate metabolizers group (t ½ = 35.5 h, CL = 1,022 ml/h) or the extensive metabolizers group (t ½ = 25.4 h, CL = 1,404 ml/h).

Conclusion: Our findings suggest that the UGT1A6 (552A>C) genetic polymorphism plays a significant role in the steady state concentration of valproic acid, and it thereby has an impact on the toxicity of the valproic acid used in the patients with epilepsy.
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http://dx.doi.org/10.1007/s40291-013-0041-8DOI Listing
October 2013

Pharmacogenetics of taxanes: impact of gene polymorphisms of drug transporters on pharmacokinetics and toxicity.

Pharmacogenomics 2012 Dec;13(16):1979-88

Pharmacotherapeutics Unit, Department of Medicine & Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia.

Interindividual variability in drug response and the emergence of adverse drug effects are the main causes of treatment failure in cancer therapy. Functional membrane drug transporters play important roles in altering pharmacokinetic profile, resistance to treatment, toxicity and patient survival. Pharmacogenetic studies of these transporters are expected to provide new approaches for optimizing therapy. Taxanes are approved for the treatment of various cancers. Circulating taxanes are taken up by SLCO1B3 into hepatocytes. The CYP450 enzymes CYP3A4, CYP3A5 and CYP2C8 are responsible for the conversion of taxanes into their metabolites. Ultimately, ABCB1 and ABCC2 will dispose the metabolites into bile canaliculi. Polymorphisms of genes encoding for proteins involved in the transport and clearance of taxanes reduce excretion of the drugs, leading to development of toxicity in patients. This review addresses current knowledge on genetic variations of transporters affecting taxanes pharmacokinetics and toxicity, and provides insights into future direction for personalized medicine.
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http://dx.doi.org/10.2217/pgs.12.165DOI Listing
December 2012

Allelic hierarchy of CDH23 mutations causing non-syndromic deafness DFNB12 or Usher syndrome USH1D in compound heterozygotes.

J Med Genet 2011 Nov 22;48(11):767-75. Epub 2011 Sep 22.

Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD 20850, USA.

Background: Recessive mutant alleles of MYO7A, USH1C, CDH23, and PCDH15 cause non-syndromic deafness or type 1 Usher syndrome (USH1) characterised by deafness, vestibular areflexia, and vision loss due to retinitis pigmentosa. For CDH23, encoding cadherin 23, non-syndromic DFNB12 deafness is associated primarily with missense mutations hypothesised to have residual function. In contrast, homozygous nonsense, frame shift, splice site, and some missense mutations of CDH23, all of which are presumably functional null alleles, cause USH1D. The phenotype of a CDH23 compound heterozygote for a DFNB12 allele in trans configuration to an USH1D allele is not known and cannot be predicted from current understanding of cadherin 23 function in the retina and vestibular labyrinth.

Methods And Results: To address this issue, this study sought CDH23 compound heterozygotes by sequencing this gene in USH1 probands, and families segregating USH1D or DFNB12. Five non-syndromic deaf individuals were identified with normal retinal and vestibular phenotypes that segregate compound heterozygous mutations of CDH23, where one mutation is a known or predicted USH1 allele.

Conclusions: One DFNB12 allele in trans configuration to an USH1D allele of CDH23 preserves vision and balance in deaf individuals, indicating that the DFNB12 allele is phenotypically dominant to an USH1D allele. This finding has implications for genetic counselling and the development of therapies for retinitis pigmentosa in Usher syndrome. ACCESSION NUMBERS: The cDNA and protein Genbank accession numbers for CDH23 and cadherin 23 used in this paper are AY010111.2 and AAG27034.2, respectively.
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http://dx.doi.org/10.1136/jmedgenet-2011-100262DOI Listing
November 2011

Homocystine levels, polymorphisms and the risk of ischemic stroke in young Asian Indians.

J Stroke Cerebrovasc Dis 2009 Mar-Apr;18(2):103-10

Department of Hematology, All India Institute of Medical Sciences, New Delhi, India.

Background: Homocysteine has been for a fairly long time been debated to be a risk factor for stroke. Opinions are divided as to whether raised levels of homocysteine seen in stroke patients are the cause or consequence of stroke. A large number of studies have been conducted in the Caucasian as well as on the Oriental population, which tend to suggest contradictory findings at many times. However, there have been no reports forthcoming from the Asian Indian population, which is a genetically different population than the previously studied populations.

Subjects And Methods: In our present study, we looked at homocysteine levels and four commonly seen polymorphisms of homocysteine metabolizing enzymes and their respective prevalence in 120 acute onset ischemic stroke patients compared with an equal number of age and gender matched healthy population. We also tested the influence of folic acid dosage (5 mg OD) on the levels of homocysteine and the allied vitamin supplements, vitamin B12 and folate in smaller groups selected from the larger group.

Results And Conclusions: We found homocysteine levels to be significantly raised in the stroke population compared with healthy controls [patients: 12 micromol/L (range: 5.3-39.1 micromol/L), controls: 11.2 micromol/L (range: 6.2-14.2 micromol/L); P =0.001]. There was an almost total response to folic acid dosage as all hyperhomocysteinemic patients showed lowering of homocysteine levels in response to the dosage. The MTHFR 677 C > T polymorphisms showed association with both homocysteine levels as well as stroke (P < 0.001). Nutritional deficiency plays a dominant role in hyperhomocysteinemic conditions in our stroke population, however. Genetic determinants of homocysteine level may also have some part in determining hyperhomocysteinemic conditions in the Asian Indian populations.
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http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2008.09.014DOI Listing
June 2009
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