Genetic polymorphisms of CYP2C19 influences the response to clopidogrel in ischemic heart disease patients in the South Indian Tamilian population.

BACKGROUND: The antiplatelet activity of clopidogrel is variable among patients suffering from ischemic heart disease. Variation in the cytochrome P450 2C19 (CYP2C19) gene coding for the CYP2C19 enzyme is one of the major determinants of this variable response to clopidogrel. The activity of the CYP2C19 enzyme, which plays a role in the conversion of the prodrug clopidogrel to its active metabolite, is genetically influenced by polymorphisms in its gene. The aim of our study was to evaluate the association of CYP2C19 polymorphisms and the antiplatelet effect of clopidogrel in the South Indian Tamilian population. MATERIALS AND METHODS: Genotyping and platelet aggregation results of 149 ischemic heart disease patients on clopidogrel maintenance therapy (75 mg daily dose) were analyzed in this study. CYP2C19 polymorphisms were genotyped by the PCR-restriction fragment length polymorphism method. We measured residual platelet activities in these patients on clopidogrel therapy in terms of impedance (expressed as ohms). The study subjects were divided into two metabolizer phenotype groups [group 1: poor/intermediate metabolizers (PM/IM); group 2: extensive/ultra-rapid metabolizers (EM/URM)] based on CYP2C19 genotype, and the residual platelet activities were compared. Higher values of impedance denote increased residual platelet activity. RESULTS: Poor/intermediate metabolizers had significantly higher impedance values than EM/URM [(median; range) 4.0; 0-13 vs. 2.0; 0-11, respectively; p = 0.04]. These higher impedance values denote higher residual platelet activities among the carriers of loss-of-function alleles (CYP2C19*2,*3) than among non-carriers. However, residual platelet activities were lower among the carriers of the gain-of-function allele (CYP2C19*17) than among non-carriers, although this difference was not significant. CONCLUSION: Patients with CYP2C19 (*2 or *3) genetic polymorphisms had higher residual platelet activities and were associated with a reduced antiplatelet response to clopidogrel. As the South Indian Tamilian population is characterized with higher frequencies of these genetic polymorphisms, our findings mandate further studies aimed at initiating genome-based personalized antiplatelet therapy.

Distribution of CYP2C19*17 allele and genotypes in an Indian population.

WHAT IS KNOWN AND OBJECTIVE: CYP2C19*17 allele increases the metabolic activity of CYP2C19 resulting in decreased therapeutic levels of CYP2C19 substrates. There exist inter-ethnic differences in the distribution of this allele. The present study was aimed at establishing the allele and genotype frequencies of CYP2C19*17 in a South Indian Tamilian population. Furthermore, we describe the haplotype structure of the three common variant alleles of CYP2C19 in the Tamilian population. METHODS: Two hundred and six subjects of South Indian Tamilian origin were genotyped for CYP2C19*17 allele by nested polymerase chain reaction and restriction fragment length polymorphism. A subset of 87 subjects were also genotyped for CYP2C19*2 and CYP2C19*3 alleles. After ascertaining linkage disequilibrium (LD), haplotypes were constructed. Allele and genotype frequencies, LD pattern and haplotype frequency were compared with those of the HapMap populations. RESULTS AND DISCUSSION: The CYP2C19*17 allele frequency in the Tamilian population (n = 206) was found to be 19·2% (95% CI: 15·4 - 20·3). The CYP2C19*2 allele frequency (n = 87) was found to be 40·2% (95% CI: 32·9 - 47·5), whereas the CYP2C19*3 allele was not detected in the study subjects (n = 97). The high frequency of the CYP2C19*17 allele in the study population has resulted in a revision of frequencies for CYP2C19*1/*2 (31·0%) and CYP2C19*1/*1 (16·1%) genotypes in the Tamilian population. We also observed significant differences in haplotype structure and frequencies of these variant alleles in the HapMap population compared to Tamilian population. WHAT IS NEW AND CONCLUSION: CYP2C19*17 allele is present at high frequency in the Tamilian population. This study also demonstrates the need for reassessment of wild-type allele frequencies in view of CYP2C19*17 allele. The estimated high frequency of CYP2C19*17 allele will aid in genotype-phenotype association studies in the Tamilian population. Further genotype-phenotype association studies are required to evaluate the clinical utility of this allele in South Indians.

Efficacy and safety of capecitabine and oxaliplatin (CAPOX) treatment in colorectal cancer: An observational study from a tertiary cancer center in South India.

Background: ">5-fluorouracil (5-FU) was the standard treatment care for colorectal cancer (CRC), however, its efficacy was limited due to safety concerns. Capecitabine and oxaliplatin (CAPOX) treatment was found equivalent to 5-FU in efficacy and preferred now due to easy management and convenience in administration. Hence, the present study aims to determine the efficacy and safety associated with CAPOX treatment in a real world non clinical setting. Methods: ">145 treatment-naive and newly diagnosed CRC patients were recruited in the study. Each patient received oxaliplatin 130 mg/m2 infusion over 2 hours on day 1 and oral capecitabine 1000 mg/m2 in divided doses twice daily for the next 14 days of a 21-day cycle. Results: In the adjuvant setting, the observed disease-free survival rate was 62% (n=34) in the colon and 67% (n=15) in the rectum cancer patients at 2 years. The observed overall survival rate in the colon and rectal cancer was 80% (n=44) and 83% (n=18) respectively at 2 years. In the palliative setting the observed progression-free survival rate was 28% (n=13) in the colon and 33% (n=7) in rectal cancer patients at 2 years. The observed OSR at 2 years was 64% (n=30) in the colon and 67% (n=14) in the rectal cancer patients. Thrombocytopenia (17, 11.7%) and diarrhea (8, 5.5%) were the most commonly observed grade 3/4 hematological and gastrointestinal toxicities. Hand-foot syndrome and peripheral neuropathy were the major contributors for dose reduction (14, 9.6%), treatment delay (8, 5.4%), and drug discontinuation (9, 6.1%) in the study cohort. Conclusion: CAPOX treatment was found to be effective but associated with several dose-limiting toxicities.

Polymorphic variants of beta1 adrenergic receptor gene (Ser49Gly & Arg389Gly) in healthy Tamilian volunteers.

BACKGROUND & OBJECTIVES: Several studies reported the polymorphisms of beta1-adrenergic receptor gene in healthy volunteers and its influence on cardiovascular disorders. We investigated the genotype and allele frequencies of Ser49Gly and Arg389Gly polymorphism in healthy volunteers of South Indian Tamilian population vis-à-vis other major ethnic groups. METHODS: The genetic variants were determined by using Taqman 5' nuclease assay- real time PCR analysis in 533 normal healthy volunteers (18-60 yr; M=290; F=243). The allelic discrimination analysis was done by 7700 SDS software. RESULTS: The estimated genotype and allele frequencies of Ser49Gly and Arg389Gly polymorphism were compared with other major populations. The frequencies of the variant alleles Gly49 and Gly389 were 15.1 and 25.8 per cent respectively. INTERPRETATION & CONCLUSIONS: Our study shows that interethnic variation exists in the polymorphisms of beta1-adrenergic receptor gene and the results generated in this study might serve as a genetic marker for further studies in Tamilian (South India) population.

Gly460Trp polymorphism of the ADD1 gene and essential hypertension in an Indian population: A meta-analysis on hypertension risk.

BACKGROUND: Essential hypertension is a complex genetic trait. Genetic variant of alpha adducin (ADD1) gene have been implicated as a risk factor for hypertension. Given its clinical significance, we investigated the association between ADD1 Gly460Trp gene polymorphism and essential hypertension in an Indian population. Further, a meta-analysis was carried out to estimate the risk of hypertension. METHODS: In the current study, 432 hypertensive cases and 461 healthy controls were genotyped for the Gly460Trp ADD1 gene polymorphism. Genotyping was determined by real time PCR using Taqman assay. Multiple logistic regression analysis was used to detect the association between Gly460Trp polymorphism and hypertension. RESULTS: No significant association was found in the genotype and allele distribution of Gly460Trp polymorphism with hypertension in our study. A total of 15 case-control studies were included in the meta-analysis. There was no evidence of the association of Gly460Trp polymorphism with hypertension in general or in any of the sub group. CONCLUSIONS: We found that the Gly460Trp polymorphism is not a risk factor for essential hypertension in a south Indian Tamilian population. However, the role of ADD1 polymorphism may not be excluded by a negative association study. Further, large and rigorous case-control studies that investigate gene-gene-environment interactions may generate more conclusive claims about the molecular genetics of hypertension.

Genetic variants of beta(1)-adrenoceptor gene polymorphisms (Ser49Gly and Arg389Gly) and essential hypertension in a south Indian Tamil population.

1. Essential hypertension is a complex polygenic disorder, the pathogenesis of which is dependent on an interplay between genetic and environmental factors. Various studies suggest an association between beta(1)-adrenoceptor gene polymorphisms (Ser49Gly and Arg389Gly) and cardiovascular disorders, including hypertension, cardiomyopathy and congestive heart failure. 2. The genetic profile of the beta(1)-adrenoceptor gene has not yet been documented for any Indian population. Thus, the aim of the present study was to investigate the association between beta(1)-adrenoceptor gene polymorphisms and essential hypertension in a south Indian Tamil population. 3. The present case-control study included 438 patients with essential hypertensives and 444 healthy volunteers from the Tamil population. Genotyping was performed using real-time polymerase chain reaction. 4. Genotype and allele frequencies of Ser49Gly and Arg389Gly polymorphism were compared between hypertensive patients and healthy volunteers. The homozygous variant genotype Gly49Gly of the Ser49Gly polymorphism was higher in hypertensive patients compared with controls (12.3 vs 7.4%, respectively). After adjusting for confounding variables (odds ratio (OR) 2.0; 95% confidence interval (CI) 1.2-2.9; P < 0.01) by multilogistic regression analysis, the gene was found to be associated with hypertension. A significant interaction was observed in hypertensive patients carrying the Ser49Gly/Gly49Gly x Arg389Gly/Gly389Gly genotypes (OR 1.9; 95% CI 1.1 2.7). 5. In conclusion, the Ser49Gly polymorphism is associated with essential hypertension in a south Indian Tamil population. The results of the present study deviate from those of previous studies, implying that marked interethnic difference exist in beta(1)-adrenoceptor gene polymorphisms.

Influence of DPYD*9A, DPYD*6 and GSTP1 ile105val Genetic Polymorphisms on Capecitabine and Oxaliplatin (CAPOX) Associated Toxicities in Colorectal Cancer (CRC) Patients.

AIM: CAPOX treatment in CRC patients was reported to cause several dose-limiting toxicities, and are found responsible for treatment interruption or even discontinuation. Therefore there is a critical need for identifying the predictive biomarkers for such toxicities to prevent them. The aim of our present study is to find the influence of DPYD*9A, DPYD*6 and GSTP1 ile105val gene polymorphisms on CAPOX treatment-associated toxicities in south Indian patients with CRC. PATIENTS AND METHODS: We have recruited 145 newly diagnosed and treatment naive CRC patients in the study. Each Patient received a standard treatment schedule of oxaliplatin 130 mg/m2 infusion over 2 hours on day 1 and oral capecitabine 1000mg/m2 in divided doses twice daily for the next 14 days of a 21-day cycle. 5 ml of the venous blood was collected from each patient and genomic DNA extraction and genotyping. The genotyping analysis of the selected genetic polymorphisms was carried out by real-time PCR using TaqMan SNP genotyping assays obtained from applied biosystems. RESULTS: The major dose-limiting toxicities observed with CAPOX treatment were thrombocytopenia, HFS and PN. DPYD*9A carries were found to be at higher risk for HFS, diarrhoea and thrombocytopenia when compared to patients with wild allele. No significant association was found between DPYD*6, GSTP1 ile105val polymorphisms and CAPOX related toxicities except for thrombocytopenia. CONCLUSION: A significant association was observed between DPYD*9A polymorphism and CAPOX induced dose-limiting toxicities strengthening its role as a predictive biomarker.

Gemcitabine and carboplatin in metastatic nonsmall cell lung cancer: Experience from a tertiary cancer center in South India.

BACKGROUND: Gemcitabine and carboplatin combination is widely used as one of the first-line chemotherapeutic regimens in patients with metastatic nonsmall cell lung cancer patients. METHODOLOGY: A total of 112 patients with metastatic disease were recruited. They were on standard 21-day gemcitabine 1.2 g/m2 and carboplatin AUC 5 dosing schedule. Each patient received at least four cycles and a maximum of 6 cycles of treatment. The patients were followed up, and the demographic, efficacy and toxicity profiles were analyzed. RESULT: The mean age was 53.81±9.85 with 71 male and 41 female patients. Response assessment was done in 82 patients, and the objective response rate was found to be 47.6% with 39 partial responders, 20 patients with stable disease and 23 patients with progressive disease. The median overall survival was 12 months (95% CI 9.89-14.11). We found anemia (62.5%) to be more prominent than the other toxicities followed by thrombocytopenia and vomiting (31.3%). The nonhematological toxicities were minimal and manageable. CONCLUSION: Treatment with gemcitabine and carboplatin is efficacious with manageable toxicity profile in the real world non-clinical trial setting.

Frequency of single nucleotide platelet receptor gene polymorphism (P2Y12-i744T>C) in coronary artery disease patients among Tamilian population.

Several factors contribute to the development of coronary artery disease (CAD). Adenosine diphosphate (ADP) activated P2Y12 receptor also plays a key role in platelet activation and aggregation. It has been found that common variation in the P2Y12 gene was associated with increased platelet aggregation resulting in adverse cardiovascular outcomes. Thus, polymorphisms in the ADP receptor P2Y12 may contribute to the development of CAD. This study aims to determine the frequency distribution of platelet receptor polymorphism P2Y12 (i744T>C) in Tamilian population and to predict its possible role in CAD. Three hundred seventy-one subjects were recruited comprising of 221 healthy volunteers and 150 patients with CAD belonging to either sex, aged 18-60 years of Tamilian origin. Genomic DNA was extracted using phenol-chloroform method. Genotyping was done by PCR-RFLP (Polymerase chain reaction-restriction fragment length polymorphism). The C allele frequency of P2Y12 polymorphism in controls and cases was 8.4% and 17.7%, respectively. The TT, TC, and CC genotype frequencies in controls and cases were 83.7%, 15.8%, 0.5% and 66.7%, 31.3%, 2%, respectively. The genotype frequencies were in Hardy-Weinberg equilibrium. There was a significant association (p < 0.05) between the mutant genotypes of P2Y12 (i744T>C) polymorphism  and risk of CAD. The odds ratio was found to be 2.6. The variant allele frequency of P2Y12-i744T>C was significantly different from other populations. There was a significant association between the mutant genotypes of P2Y12 (i744T>C) polymorphism  and risk of developing CAD. Thus, the present study will emphasize on the relevance of pharmacogenetic testing of P2Y12 (i744T>C)  receptor gene polymorphism in CAD patients.

A study on the vasopressin induced delay in the gastrointestinal transit in mice: possible mechanism of action.

The effect of arginine vasopressin (AVP) on the gastrointestinal (GI) transit and its possible mechanism were studied using charcoal meal test in mice. A dose related inhibitory effect was recorded. The effect appears to be independent of the time allowed between AVP administration and testing. The studies on the mechanism reveal that AVP acts without involving V1 and V2 vasopressin receptors. An almost complete reversal of the effect by physostigmine and potentiation by atropine indicate that AVP might act through an inhibition of the release of acetylcholine. However, the neural nicotinic receptors mechanisms do not seem to contribute since hexamethonium failed to modify the AVP action. Further, a partial antagonism by naloxone or prazosin pretreatment indicates that opioid and alpha 1 adrenergic systems also contribute to this action of AVP. However, the effect appears to be independent of alpha 2 and beta adrenergic systems since yohimbine and propranolol failed to modify the same.

Gastric antisecretory and antiulcer activity of oxytocin in rats and guinea pigs.

The effect of oxytocin (1 mg/kg s.c) on gastric acid secretion and on different experimentally induced gastric and duodenal ulcers was studied. The acute gastric ulcer models used were pylorus ligation, indomethacin, ethanol and histamine induced acute gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by cysteamine hydrochloride. Oxytocin showed significant antisecretory and antiulcer activity in pylorus ligated rats. Similarly oxytocin reduced the ulcer index in histamine induced gastric ulcers in guinea pigs and cysteamine induced duodenal ulcers in rats. The antiulcer and antisecretory effect was comparable to that of ranitidine (50mg/kg, i.p) though less in intensity. However, it did not show any gastric cytoprotective effect in ethanol and indomethacin induced ulcer models but ranitidine showed protection (p<0.05) in later model. Oxytocin enhanced gastric ulcer healing in acetic acid induced chronic gastric ulcer model. The reversal of oxytocin effect by atosiban, an oxytocin receptor antagonist indicates a role for oxytocin receptors. The antiulcer activity of oxytocin can be attributed to its antisecretory effect.

Effect of centrally administered prolactin on gastric and duodenal ulcers in rats.

The effect of centrally administered prolactin on gastric acid secretion and experimentally-induced gastric and duodenal ulcers was studied. The acute gastric ulcer models used were pylorus ligation, indomethacin-induced and ethanol-induced gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by cysteamine hydrochloride. In pylorus ligated rats, prolactin (1 microg/kg icv) produced 45% increase in gastric content volume, significant increase in free acidity (P < 0.001), total acidity (P < 0.001) and ulcer index (P < 0.001). It did not show any significant effect on ethanol-induced and indomethacin-induced gastric ulcers. Prolactin increased the ulcer index (P < 0.001) and ulcer score (P < 0.05) in acetic acid-induced chronic gastric ulcers. It also increased ulcer area (P < 0.05) in cysteamine-induced duodenal ulcers. Therefore, the proulcerogenic activity of prolactin was due to its gastric hypersecretory effect.

Relative efficacy of some prokinetic drugs in morphine-induced gastrointestinal transit delay in mice.

AIM: To study the relative efficacy of cisapride, metoclopramide, domperidone, erythromycin and mosapride on gastric emptying (GE) and small intestinal transit (SIT) in morphine treated mice. METHODS: Phenol red marker meal was employed to estimate GE and SIT in Swiss albino mice of either sex. The groups included were control, morphine 1 mg/kg (s.c. 15 min before test meal) alone or with (45 min before test meal p.o.) cisapride 10 mg/kg, metoclopramide 20 mg/kg, domperidone 20 mg/kg, erythromycin 6 mg/kg and mosapride 20 mg/kg. RESULTS: Cisapride, metoclopramide and mosapride were effective in enhancing gastric emptying significantly (P<0.001) whereas other prokinetic agents failed to do so in normal mice. Metoclopramide completely reversed morphine induced delay in gastric emptying followed by mosapride. Metoclopramide alone was effective when given to normal mice in increasing the SIT. Cisapride, though it did not show any significant effect on SIT in normal mice, was able to reverse morphine induced delay in SIT significantly (P<0.001) followed by metoclopramide and mosapride. CONCLUSION: Metoclopramide and cisapride are most effective in reversing morphine-induced delay in gastric emptying and small intestinal transit in mice respectively.

Further studies on the anti-nociceptive effect of vasopressin.

The possible interactions of pathways which mediate anti-nociception when stimulated by alpha 2-adrenoceptor agonists and arginine vasopressin (AVP) were investigated. Yohimbine, an alpha 2-antagonist, failed to modify the anti-nociceptive response of AVP. However, clonidine pretreatment, in sub-effective and effective doses, potentiated the anti-nociceptive response of a sub-effective dose of AVP. This potentiation was attenuated by yohimbine and completely antagonized by naloxone. These studies suggest that pathways related to the opioidergic system and those stimulated by alpha 2-agonists may be utilized by AVP in eliciting the anti-nociceptive response.

Effect of hyperprolactinaemia as induced by pituitary homografts under kidney capsule on gastric and duodenal ulcers in rats.

The effect of hyperprolactinaemia, induced by two or four pituitary homografts under the kidney capsule, on gastric and duodenal ulcers has been studied. The acute gastric ulcer models used were pylorus ligation, indometacin-induced and ethanol-induced gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by mercaptamine hydrochloride. After pylorus ligation, there was an approximate 30-40% increase in gastric secretion, a significant increase in total acidity (P < 0.01) and in the ulcer index (P < 0.01) in rats bearing pituitary homografts under the kidney capsule when compared with the sham-operated control. Hyperprolactinaemia did not affect the formation of ethanol-induced gastric ulcers but showed a 40% reduction in the development of indometacin-induced gastric ulcers. It also produced a 20% increase in the ulcer index in acetic acid-induced chronic gastric ulcers and a 30% increase in ulcer area in mercaptamine-induced duodenal ulcers. Our results showed that hyperprolactinaemia induced gastric acid secretion and thereby aggravated gastric and duodenal ulcers in rats. Hyperprolactinaemia did not affect gastric cytoprotection.

Pharmaco-economic analysis of psychotropic drugs.

OBJECTIVES: To analyse cost and adverse reactions of psychotropic drugs for their cost-effective use. METHODS: Four hundred and sixty nine psychotropic formulations from CIMS, June 1998 were evaluated for (a) extent of variation in retail price for same strength and dosage form, (b) role of number of companies manufacturing the same formulation and (c) companies pricing their product at price less than average of maximum and minimum price in relation to number of products marketed by them. The side effects of antipsychotic and antidepressant drugs were graded for their severity and cumulative side effects score. Side effect index and cost index were calculated on relative basis and their product was used as cost benefit index. RESULTS: Fifty per cent of psychotropic drugs had less than 100% price variation with highest of 2049% for risperidone 4 mg tablets. A direct relationship existed between the drug cost and price variation wherever the variation crossed 200%. Similar trend was noticed between the minimum price variations and the number of companies marketing the product. There was no appreciable relationship between number of products marketed and pricing by the manufacturer. Cumulative side effect score was lowest (10) for trifluoperazine and pimozide and highest (15) for risperidone amongst antipsychotic drugs, whereas amongst antidepressants fluoxetine had lowest (1.75) and amitryptyline had highest (28.5) cumulative side effect score. CONCLUSION: One has to be more careful while selecting a brand of a drug when price variation is more (200-2049%). Trifluoperazine (1.0) and fluoxetine (1.7) were found to be most economical with better cost benefit index compared to thioridazine (494.2) and clomipramine (113.0) in their respective groups. Thus our analysis provides basic information regarding cost effective therapy with psychotropic drugs.

Effect of ATP sensitive potassium channel modifiers on antinociceptive effect of metoclopramide.

Metoclopramide, a prokinetic drug, has been documented to produce antinociceptive response in animal models through opioid pathways. Morphine has been shown to act through ATP sensitive potassium channels (KATP) to produce antinociceptive response. However, such a possibility has not been examined for metoclopramide. The present study investigated this using pharmacological tools. Acetic acid induced abdominal constriction assay procedure was utilized to assess antinociception. The results confirmed that metoclopramide has antinociceptive response. Glibenclamide, a KATP channel blocker, pretreatment antagonized this response. Where as, in minoxidil pretreated animals, metoclopramide elicited an enhanced antinociceptive response. Glibenclamide and minoxidil, which are known KATP channel blocker and opener respectively, interfered with metoclopramide antinociception. These finding are suggestive of a role for KATP channels in metoclopramide antinociception in mice.

Prolactin induced analgesia is dependent on ATP sensitive potassium channels.

1. The role of ATP sensitive potassium channels in the analgesic activity of prolactin (PRL) was studied in mice using glibenclamide and minoxidil, a blocker and an opener of these channel, respectively. 2. Pre-treatment with glibenclamide attenuated the analgesic activity of PRL while treatment with minoxidil potentiated the activity. 3. It is concluded that PRL, similar to morphine, utilizes ATP sensitive potassium channels in eliciting the analgesic response.

A comprehensive study on the mechanism of inhibition of serine proteases by benzamidines based on quantitative structure-activity relationship studies.

Based on quantitative structure-activity relationship studies, investigation is made on the mechanism of inhibition of serine proteases, i.e., thrombin, plasmin, trypsin, and complement, by benzamidines. It is found that inhibitions of all the four enzymes, thrombin, plasmin, trypsin and complement, involve hydrophobic interaction in general but they do not involve electronic interaction in all the cases. In the cases where the electronic interaction is involved the mode of interaction is not necessarily the same. The electronic interaction depends upon the kind and the source of the enzyme.