Pharmacogenetics of CYP1A2, novel polymorphisms and haplotypes in three distinct Asian populations

CYP1A2 play an important role in the metabolism of many carcinogens and clinically important drugs. CYP1A2 activity has been found to be influenced by the presence of polymorphic variants which were reported to display wide interethnic variation. This study investigates the frequency distribution and linkage disequilibrium patterns of CYP1A2 genetic polymorphisms, and characterize their haplotype structures in three healthy Asian populations in Singapore (Chinese, Malay, and Indian). The entire CYP1A2 gene was screened in 126 healthy subjects from all three ethnic groups (N=42 each). A total of 25 polymorphisms was identified, of which nine were novel. The polymorphisms, -2467delT and -163C>A were detected at high frequencies in all Asian ethnic groups. Significant interethnic differences were observed in the genotypic frequency distribution of IVS2-99G>A (P<0.01) and 1548C>T (P=0.05) across the three ethnic groups while -163C>A (P=0.02) was found to differ between Chinese and Malays. Haplotype analyses revealed four to six major haplotypes in each ethnic population which accounted for more than 60% of the cumulative haplotype frequencies. Future studies should be done to investigate the functional roles of these haplotypes.     

Anticandidal Activity of Punica granatum. Exhibited in Different Solvents

Abstract

Anticandidal activity of Punica granatum L.. extracts in ethanol, methanol, propanol, acetone, benzyl alcohol, 1,4-dioxan, and N,N.-dimethyl formamide (DMF) is reported. The selection of solvents was on the basis of their polarity. Growth inhibition using the agar ditch diffusion assay was determined on four different strains of Candida. species isolated from HIV-positive patients. Ethanolic extract showed activity against three Candida. species, whereas it was ineffective against Candida albicans. 1. The methanol, acetone, and propanol extracts were effective against all four Candida. species. The DMF extract was effective against Candida albicans. 1 and 2 and showed moderate activity against Candida albicans. 3, whereas it was ineffective against “Candida species. 1.” The 1,4-dioxan extract was effective against Candida albicans. 1, Candida albicans. 2, and Candida species. 1 and was ineffective against Candida albicans. 3. The benzyl alcoholic extract was ineffective in showing any kind of activity against any of the four candidal strains. These different extracts of P. granatum. were also compared with commercially available antibiotics such as nystatin, clotrimazole, and amphotericin B, and the natural plant extract proved to be better against some candidal species.     

Single nucleotide polymorphisms of the pregnane x receptor gene in Han Chinese and a comparison with other ethnic populations

The pregnane X receptor (PXR/NR1I2) gene is a master regulator for a number of cytochrome P450s (CYPs) and drug transporters. This study aimed to detect the single nucleotide polymorphisms (SNPs) of the PXR gene in Han Chinese (n = 186) and to compare the frequencies of polymorphisms of the PXR gene with those in Caucasian and African Americans reported in the literature. The SNPs of the PXR gene were analyzed using the polymerase chain reaction (PCR) and direct sequencing analysis. The mutant frequencies of A11156C and T11193C in Han Chinese were 55% (95% confidence interval (CI): 0.49-0.61) and 59% (95% CI: 0.52-0.64), respectively, higher than those of Caucasian Americans (16 and 16%, respectively) and African Americans (33 and 30%, respectively). However, the reported SNPs in exons 2 and 4 (PXR*2,*3,*4,*6,*9,*10,and *11) were not detected in Han Chinese. These results indicate that there are marked differences in the mutant frequencies of A11156C and T11193C of PXR between Han Chinese and other ethnic groups. The mutant frequency in the coding region (exons 2 and 4) of PXR was very low in Han Chinese. Further studies are needed to determine the impact of common SNPs of PXR in Han Chinese and other ethnic populations on the phenotypic activity of cytochrome P450s and drug transporters transactivated by PXR.     

Influence of APOE genotypes and VKORC1 haplotypes on warfarin dose requirements in Asian patients

Aims

To investigate the influence of APOE genotypes and VKORC1 haplotypes on warfarin dose requirements in Asian patients.

Methods

A total of 174 Asian patients (Chinese, n = 96; Malays, n = 50; Indians, n = 28) who had stable daily warfarin doses for at least 1 month were recruited. Following genomic DNA extraction from venous blood, pharmacogenetic analysis of APOE and VKORC1 genes was done by DNA sequencing.

Results

The majority of the Asian patients (78%) harboured the APOE ε3/ε3 genotype. Different APOE genotypes were found not to have any significant influence on mean daily warfarin dose requirements. Warfarin dose requirements in the pooled Asian patients homozygous for the VKORC1 H1 haplotype were significantly lower compared with patients homozygous for the H7 haplotype (H1-H1 vs. H7-H7: 2.79 ± 1.06 mg day⁻¹vs. 5.45 ± 2.3 mg day⁻¹, P < 0.001).

Conclusions

The present study suggests that APOE variants have minimal impact on warfarin dose requirements in Asian patients, probably due to the low frequency of ε4 allele containing genotypes.

What is already known about this subject

• Recent studies on pharmacogenetics of warfarin have implicated apolipoproteinE (APOE) polymorphisms to influence the vitamin K dependent coagulation cascade and hence the efficacy of warfarin.
• Studies among Caucasian and African Americans showed a significant but conflicting role of apolipoproteinE (APOE) isoforms in warfarin pharmacogenetics.
• The contribution of APOE isoforms in influencing variations in warfarin requirements in Asian subjects remains to be investigated.

What this study adds

• This is the first report of a population study in Asians exploring the role of isoforms encoded by three APOE alleles (ε2, ε3, ε4) in influencing warfarin dose requirements.
• The present study showed that the APOE ε3/ε3 isoform is the predominant genotype in the Asian population.
• The study also showed that APOE isoforms may not be important in affecting warfarin pharmacodynamics in Asian patients. It also suggested that the impact of different APOE isoforms depended on the frequency of APOE genotypes in the population, in particular the ε4 allele containing genotypes.

     

Radial artery in CABG: could the early results be comparable to internal mammary artery graft?

Background. The accidental detection of patency of radial artery grafts, by Acar, which had been labeled as blocked 18 years earlier, has led to its revival as a conduit in coronary artery bypass surgery. We used radial artery as one of the grafts in 287 patients from February 1996 to June 1998. Here we present our early clinical experience and the midterm angiographic follow up of the initial 62 patients.

Methods. A no touch, atraumatic harvesting technique coupled with gentle hydrostatic and pharmacological dilatation of the radial artery graft was employed. Radial artery was used to revascularize coronary vessels with >80% proximal stenosis. Postoperatively, the patients were administered a low dose nifedipine that was continued for 6 months thereafter. The patients were followed up clinically after discharge from the hospital and angiographic evaluation of the grafted radial artery by selective injection was done at a mean interval of 16.2 ± 5.1 months (3–24 months) postoperatively.

Results. There was no perioperative or late myocardial infarction or mortality. No significant complications related to the harvesting of radial artery were encountered. Angiographically, the radial artery grafts were found to be patent in 96.8% of patients (60/62). Mild distal anastomotic narrowing was seen in angiogram of one patient with good filling of the target vessel. Another patient showed diffuse spasm of radial artery graft. The patency of the pedicled left internal mammary grafts was also 98.2% (56/57). All the patients were asymptomatic.

Conclusions. Radial artery seems to be an excellent alternate arterial conduit for myocardial revascularization with early and midterm patency rates equivalent to that of pedicled internal mammary artery, and it should be used more often for myocardial revascularization as an adjunct to pedicled internal mammary artery graft.     

Comparison of Indian Council for Medical Research and Lunar Databases for Categorization of Male Bone Mineral Density

The mainstay of diagnosis of osteoporosis is dual-energy X-ray absorptiometry (DXA) scan measuring areal bone mineral density (BMD) (g/cm²). The aim of the present study was to compare the Indian Council of Medical Research database (ICMRD) and the Lunar ethnic reference database of DXA scans in the diagnosis of osteoporosis in male patients. In this retrospective study, all male patients who underwent a DXA scan were included. The areal BMD (g/cm²) was measured at either the lumbar spine (L1–L4) or the total hip using the Lunar DXA machine (software version 8.50) manufactured by GE Medical Systems (Shanghai, China). The Indian Council of Medical Research published a reference data for BMD in the Indian population derived from the population-based study conducted in healthy Indian individuals, which was used to analyze the BMD result by Lunar DXA scan. The 2 results were compared for various values using statistical software SPSS for Windows (version 16; SPSS Inc., Chicago, IL). A total 238 male patients with a mean age of 57.2?yr (standard deviation ±15.9) were included. Overall, 26.4% (66/250) and 2.8% (7/250) of the subjects were classified in the osteoporosis group according to the Lunar database and the ICMRD, respectively. Out of the 250 sites of the DXA scan, 28.8% (19/66) and 60.0% (40/66) of the cases classified as osteoporosis by the Lunar database were reclassified as normal and osteopenia by ICMRD, respectively. In conclusion, the Indian Council of Medical Research data underestimated the degree of osteoporosis in male subjects that might result in deferring of treatment. In view of the discrepancy, the decision on the treatment of osteoporosis should be based on the multiple fracture risk factors and less reliably on the BMD T-score.