Chandrasekaran Adithan

Glutathione S-transferase M1 and T1 null genotype distribution in South Indians

ObjectiveTo investigate the distribution of the homozygous null genotypes of GSTM1 and GSTT1 in the South Indian population.MethodsFive hundred and seventeen unrelated natives of the South Indian states of Tamilnadu and Pondicherry (n=170), Kerala (n=122), Karnataka (n=110) and Andhra Pradesh (n=115) were analyzed for homozygous deletions of GSTM1 and GSTT1. A multiplex polymerase chain reaction method simultaneously detected both GSTM1 and GSTT1 homozygous null genotypes. The observed frequencies from the four groups were compared statistically with each other and the combined frequencies were compared with frequencies of other major populations previously reported in the literature.ResultsIn South India, 30.4% (95% CI 26.4–34.3) lacked the GSTM1 gene, 16.8% (13.6–20.1) lacked the GSTT1 gene and 4.6% (3.0–6.8) lacked both the GSTM1 and GSTT1 genes. The highest frequency of GSTM1 null was observed in Karnataka (36.4%, 27.4–45.4), while Andhra Pradesh had the lowest frequency of the GSTM1 and GSTT1 combined double-null genotypes (1.7%, 0.21–6.2).ConclusionThe prevalence of the GSTM1 null genotype differed within India. The frequency of GSTM1 null in South Indians was significantly lower than that in Caucasians. The frequencies of both GSTM1 and GSTT1 null genotypes in South Indians were significantly lower than in the Japanese.

Allele and genotype frequency of CYP2C9 in Tamilnadu population.

ObjectivesTo identify the frequency of CYP2C9*1, *2 and *3 alleles and the genotype of CYP2C9 gene in the Tamilian population.MethodsThe study was conducted on 135 unrelated healthy human volunteers. DNA was extracted from the peripheral leukocytes samples and was analyzed using the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) protocol. The PCR products were digested with AvaII, KpnI or NsiI restriction enzymes. The digested products were separated using 8% polyacrylamide gel and stained by ethidium bromide. Genotyping of the subjects was done based on DNA fragment size.ResultsThe frequencies of CYP2C9*1, *2 and *3 alleles in the Tamilian population were 0.907, 0.026 and 0.067, respectively. The distribution of CYP2C9*1/*1, *1/*2, *1/*3 and *2/*3 genotypes were 0.823, 0.044, 0.126 and 0.007, respectively.ConclusionCYP2C9*3 is the most frequent mutant allele found in the Tamilian population. The distribution of this mutant allele in the Tamilian population was found to be lesser than in Caucasians but higher than in Chinese.

Cardiovascular dysfunctions and sympathovagal imbalance in hypertension and prehypertension: physiological perspectives

Hypertension (HTN) and prehypertension (pre-HTN) have been identified as independent risk factors for adverse cardiovascular events. Recently, increased psychosocial stress and work stress have contributed to the increased prevalence of HTN and pre-HTN, in addition to the contribution of obesity, diabetes, poor food habits and physical inactivity. Irrespective of the etiology, sympathetic overactivity has been recognized as the main pathophysiologic mechanism in the genesis of HTN and pre-HTN. Sympathovagal imbalance owing to sympathetic overactivity and vagal withdrawal is reported to be the basis of many clinical disorders. However, the role played by vagal withdrawal has been under-reported. In this review, we have analyzed the pathophysiologic involvement of sympathovagal imbalance in the development of HTN and pre-HTN, and the link of sympathovagal imbalance to cardiovascular dysfunctions. We have emphasized that adaptation to a healthier lifestyle will help improve sympathovagal homeostasis and prevent the occurrence of HTN and pre-HTN.

Influence of CYP2C9 and CYP2C19 genetic polymorphisms on phenytoin-induced neurological toxicity in Indian epileptic patients

ObjectiveCytochrome P450 2C9 and 2C19 (CYP2C9 and CYP2C19, respectively) genetic polymorphisms play an important role in phenytoin (PHT) metabolism. We have evaluated whether these genetic polymorphisms have an effect on PHT-induced neurological toxicity in Tamilian (ethnic group native to southern India) patients with epilepsy.MethodsWe studied 292 Tamilian patients who were taking PHT for the treatment of various epileptic seizures. PHT toxicity was defined on the basis of neurological signs of toxicity and further sub-classified into mild, moderate, and severe toxicity based on clinical severity. Genomic DNA was extracted from peripheral leukocytes and genotyped for CYP2C9*2, *3 and CYP2C19*2, *3 by PCR-restriction fragment length polymorphism analysis.ResultsOf the 292 patients in the patient cohort, 58 were clinically diagnosed to have PHT toxicity. When risk ratios were calculated for each mutant CYP2C9 genotype separately, the adjusted odds ratio for CYP2C9*1/*3 was found to be 15.3 (95% confidence interval 5.8–40.3, P < 0.0001) for the cases compared to controls. When the four single nucleotide polymorphisms of CYP2C9 and CYP2C19 were analyzed using a haplotype approach, significant difference in the distribution of the C-C-G-G haplotype was observed between the cases and controls.ConclusionOur results show that CYP2C9 genetic polymorphisms (particularly the *3 allele) were associated with high risk of epileptic patients developing PHT-induced neurological toxicity.

Assessment of sympathovagal imbalance by spectral analysis of heart rate variability in prehypertensive and hypertensive patients in Indian population.

Though the incidence of hypertension has increased considerably in recent years, the pathophysiologic mechanism that causes progression from stage of prehypertension to hypertension has not been fully elucidated. Therefore, the present study was conducted to assess the sympathovagal imbalance in prehypertensives and hypertensives by spectral analysis of heart rate variability (HRV) to understand the nature of change in autonomic balance in this common dysfunction of mankind. Body mass index (BMI), basal heart rate (BHR), blood pressure (BP), and spectral indices of HRV such as total power (TP), normalized low frequency power (LFnu), normalized high frequency power (HFnu), ratio of low frequency power to high frequency power (LF-HF ratio), mean heart rate (mean RR), square root of the mean squared differences of successive normal to normal intervals (RMSSD), the number of interval differences of successive NN intervals greater than 50 ms (NN50), and the proportion derived by dividing NN50 by the total number of NN intervals (pNN50) were assessed in three groups of subjects: normotensives (n = 32), prehypertensives (n = 28), and hypertensives (n = 31). Sympathovagal balance was analyzed and correlated with BMI, BHR, and BP in all the groups. It was observed that autonomic imbalance in prehypertensives was due to proportionate increased sympathetic activity and vagal inhibition, whereas in hypertensives, vagal withdrawal was more prominent than sympathetic overactivity. The LF-HF ratio, the sensitive indicator of sympathovagal balance, was significantly correlated with BMI, BHR, and BP. It was concluded that vagal inhibition plays an important role in the critical alteration of sympathovagal balance in the development of clinical hypertension in prehypertensive subjects.

Influence of CYP2C9 gene polymorphisms on response to glibenclamide in type 2 diabetes mellitus patients

PurposeThe antidiabetic drug glibenclamide is metabolized by the enzyme cytochrome P450 2C9 (CYP2C9) encoded by the polymorphic gene CYP2C9. Previous studies involving healthy volunteers have shown a significant influence of variant CYP2C9 genotypes on glibenclamide metabolism. The aim of this study was to investigate the influence of genetic polymorphisms of CYP2C9 on the response to glibenclamide and on glibenclamide plasma levels in type 2 diabetes mellitus patients.MethodsThe study cohort consisted of type 2 diabetes mellitus patients (n = 80) on regular therapy with glibenclamide either alone or with concomitant metformin. Plasma levels of glibenclamide were estimated by reverse phase high pressure liquid chromatography. The variant alleles of CYP2C9, namely CYP2C9 *2 and *3, were identified by PCR–restricted fragment length polymorphism. The plasma levels of glibenclamide and occurrences of hypoglycemic adverse effects with their severity were compared between the genotype groups.ResultsOf the 80 patients (61 males, 19 females), 78 were on concomitant treatment with two drugs, namely, glibenclamide and metformin, and two were on monotherapy with glibenclamide. There was a significant association (p < 0.001) between genotype status of CYP2C9 and the control of diabetes in patients receiving treatment with glibenclamide. There were no statistically significant differences in hypoglycemic adverse effects between the genotype groups.ConclusionThe type 2 diabetes mellitus patients participating in this study with variant genotypes of CYP2C9 were found to respond better to treatment with glibenclamide than those with the normal genotype. The variant genotype CYP2C9 *1/*3 did not significantly influence the hypoglycemic adverse effects among those patients on long-term glibenclamide treatment.

Sympathovagal imbalance contributes to prehypertension status and cardiovascular risks attributed by insulin resistance, inflammation, dyslipidemia and oxidative stress in first degree relatives of type 2 diabetics.

Background Though cardiovascular (CV) risks are reported in first-degree relatives (FDR) of type 2 diabetics, the pathophysiological mechanisms contributing to these risks are not known. We investigated the association of sympathovagal imbalance (SVI) with CV risks in these subjects. Subjects and Methods Body mass index (BMI), basal heart rate (BHR), blood pressure (BP), rate-pressure product (RPP), spectral indices of heart rate variability (HRV), autonomic function tests, insulin resistance (HOMA-IR), lipid profile, inflammatory markers, oxidative stress (OS) marker, rennin, thyroid profile and serum electrolytes were measured and analyzed in subjects of study group (FDR of type 2 diabetics, n = 72) and control group (subjects with no family history of diabetes, n = 104). Results BMI, BP, BHR, HOMA-IR, lipid profile, inflammatory and OS markers, renin, LF-HF (ratio of low-frequency to high-frequency power of HRV, a sensitive marker of SVI) were significantly increased (p<0.0001) in study group compared to the control group. SVI in study group was due to concomitant sympathetic activation and vagal inhibition. There was significant correlation and independent contribution of markers of insulin resistance, dyslipidemia, inflammation and OS to LF-HF ratio. Multiple-regression analysis demonstrated an independent contribution of LF-HF ratio to prehypertension status (standardized beta 0.415, p<0.001) and bivariate logistic-regression showed significant prediction (OR 2.40, CI 1.128–5.326, p = 0.002) of LF-HF ratio of HRV to increased RPP, the marker of CV risk, in study group. Conclusion SVI in FDR of type 2 diabetics occurs due to sympathetic activation and vagal withdrawal. The SVI contributes to prehypertension status and CV risks caused by insulin resistance, dyslipidemia, inflammation and oxidative stress in FDR of type 2 diabetics.

Genetic polymorphisms of drug‐metabolizing phase I enzymes CYP2E1, CYP2A6 and CYP3A5 in South Indian population

CYP2E1, CYP2A6 and CYP3A5 enzymes belong to phase I group of drug‐metabolizing enzymes, which are involved in the metabolism of various compounds and xenobiotics. Presence of polymorphisms in the genes coding for these enzymes results in interindividual variations in drug metabolism, therapeutic response and susceptibility towards various diseases. The frequencies of these variants in genes differ considerably between ethnic groups. This study was carried out to estimate the allele and genotype frequencies of common variants in CYP2E1, CYP2A6 and CYP3A5 in South Indian population. Six hundred and fifty‐two unrelated healthy volunteers of South Indian origin (Andhra Pradesh, Karnataka, Kerala and Tamil Nadu) were included in this study. Polymerase chain reaction–restriction fragment length polymorphism, allele‐specific PCR, real‐time PCR, SNaPshot and gene sequencing methods were used for the identification of gene polymorphisms. The frequencies of CYP2E1*1B, CYP2E1*5B and CYP2E1*6 alleles in South Indian population were 14.3, 1.3 and 22.4%, respectively. The frequencies of CYP2A6*2, CYP2A6*4A and CYP2A6*5 alleles were found to be 1, 8.9 and 0.7%, respectively. The distribution of CYP3A5*3 allele was 63.5%. There were no variant alleles of CYP3A5*2, CYP3A5*4 and CYP3A5*6 in South Indian population. The frequencies of CYP2E1, CYP2A6 and CYP3A5 in the South Indian population are distinct from Caucasians, Chinese, Japanese, African Americans and other compared populations. This is the first study conducted in the South Indian population with a larger sample size. The findings of our study provide the basic genetic information for further pharmacogenomic investigations in the population.

A study of adverse drug reactions in pediatric patients

Aim: To study the adverse drug reaction (ADR) pattern in a pediatric population in a tertiary care hospital. Materials and Methods: An observational study was done in the department of pediatrics in a tertiary care hospital. The ADRs occurring in the inpatient wards and outpatient department of pediatrics were actively monitored. The collected reports were analyzed for ADR pattern, drug groups, demographic profile, causality, severity, and preventability of the ADR. Results: A total of 30 ADRs were documented during the mid period of 2009 among pediatric patients. Most of the ADRs (60%) occurred below the age of 1 year. Antibiotics comprised the major group of drugs causing ADRs (67%). Rashes and urticaria were the most common type of ADR (37%) followed by fever, anaphylactic shock, vomiting, chills, and rigors. A single case of death had been reported in the study period. There were more occurrences of ADRs with multiple drugs compared to single drug therapy. About 80% of the ADRs were of probable causality and 87% were of probable preventability. There were no mild reactions, with 77% of reactions being moderate and 23% of reactions being severe in the severity scale. Conclusions: ADRs occur more among infants and antibiotics were more commonly implicated. Most of the reactions were of moderate severity. This indicates the need for a rigid ADR monitoring among pediatric patients to ensure safety of drug therapy.

Adverse drug reaction profile of cisplatin-based chemotherapy regimen in a tertiary care hospital in India: An evaluative study

Aims: This prospective study was designed to monitor and analyze the pattern of occurrence of adverse drug reactions (ADRs) to cisplatin-based chemotherapy regimen in the cancer ward of a tertiary care hospital. Materials and Methods: Cancer patients who received cisplatin-based cancer chemotherapy were monitored for adverse reactions. The collected reports were analyzed for demographic and drug details, causality, preventability and severity of adverse effects. Causality was assessed by the World Health Organization (WHO) causality assessment scale and Naranjos Algorithm. Preventability and severity of ADRs were assessed by modified Schumock and Thornton scale, modified Hartwig and Siegel scale respectively. Results: Among 51 patients, 48 developed ADRs to cisplatin chemotherapy. The reactions observed were nausea, alopecia, anorexia, vomiting, taste alteration, diarrhea, constipation, tinnitus, and hypocalcaemia. The WHO causality assessment scale indicated 69% “possible” and 31% “probable” but no “certain” reactions. Naranjos Algorithm showed 62% “probable” and 38% “possible” reactions. Most of the reactions belonged to the category of “not preventable”. Reactions like nausea and vomiting belonged to the category of “definitely preventable”. Modified Hartwig and Siegel scale of severity assessment showed that most of the reactions were of “mild level 1” severity except for vomiting, diarrhea and hypocalcaemia, which were of “moderate level 3” severity. Conclusion: Cisplatin-based chemotherapy has a high potential to cause adverse effects. Most of the reactions were of milder nature but not preventable. The common adverse effects such as nausea and vomiting were preventable, but reactions like hypersensitivity reactions and anaphylaxis were not predictable.