Mario Štefanović

Polymorphism of apoprotein E (APOE), methylenetetrahydrofolate reductase (MTHFR) and paraoxonase (PON1) genes in patients with cerebrovascular disease.

Abstract Although controversial, data on the genetic polymorphism of apoprotein E (APOE), methylenetetrahydrofolate (MTHFR) and paraoxonase (PON1) genes implicate their role in the development of cerebrovascular disease. The aim of this study was to assess the association of polymorphism of APOE, MTHFR and PON1 genes in 56 stroke and 36 carotid stenosis patients, and in 124 control subjects by PCR-restriction fragment length polymorphism analysis. In the stroke group a significantly different MTHFR genotype distribution (p=0.004, odds ratio for T/T of 17.571), but no significant difference in APOE and PON1 allele and genotype distribution compared to the control was found. The carotid stenosis group exhibited a significantly different APOE allele and genotype distribution (p=0.023, odds ratio APOE∊3∊4 of 4.24), but no significant difference in the MTHFR and PON1 allele and genotype distribution from the control group. The preliminary results obtained in this study revealed an association of the MTHFR and APOE gene polymorphism with cerebrovascular disease, suggesting a significant risk for stroke in subjects who are homozygous for the T allele and for carotid stenosis in subjects having APOE∊3∊4 genotype. Additional studies in larger patient groups are needed to confirm these observations.

Association between the CYP2C9 polymorphism and the drug metabolism phenotype

Abstract CYP2C9, an isoform of the cytochrome P450 enzyme, is involved in the metabolism of most of the drugs of choice for the treatment of thromboembolic disorders. Functional polymorphism is associated with two variant alleles (alleles *2 and *3) encoding CYP2C9 enzymes with a potentially different catalytic activity. The aim of the study was to determine the frequency of the CYP2C9 polymorphism in a representative sample of the Croatian population (n=177) and to assess the association between the CYP2C9 polymorphism and the warfarin dose in patients with thromboembolism (n=181). The CYP2C9 genotype was determined by polymerase chain reaction-restriction fragment length poymorphism (PCR-RFLP). According to the CYP2C9 genotype distribution, 31.2% of the healthy subjects were identified with a heterozygous or homozygous CYP2C9 variant genotype. The frequency of 2C9*2 and 2C9*3 alleles was 12.4% and 3.7%, respectively. There was no gender-related genotype or allele difference. In thromboembolism patients, the frequency of CYP2C9 alleles *2 and *3 was 17.4% and 6.6%, respectively, and did not differ significantly from the control group. Almost half (42.5%) of the patients carried at least one variant CYP2C9 genotype. The allele difference between patient subgroups receiving warfarin doses lower and higher than the optimal warfarin dose (4.1 mg/day) was significant (p=0.027), especially for allele 2C9*3 (p=0.019; OR 3.250, 95%, CI 1.263–8.413). Comparison of the warfarin dose between patients with different genotypes yielded a significant dose difference between the patients with wild-type genotype and those with variant genotypes (Kruskall-Wallis, χ2=9.745, p=0.008). The results of the association of each of five genotype combinations with the warfarin maintenance dose revealed it to be significantly related to the genotype (Kruskall-Wallis, χ2=12.854, p=0.025). Expressed as percentage of the mean dose in patients with wild-type alleles, the mean warfarin maintenance dose was 92% in 2C9*2 heterozygotes, 74% in 2C*3 heterozygotes, 61% in 2C9*2 homozygotes, 34% in 2C9*3 homozygotes and 63% in compound heterozygotes for 2C9*2 and 2C9*3. Although the mean maintenance dose in homozygous *2/*2 and compound *2/*3 genotype patients was markedly lower (mean 2.66 mg and 2.75 mg, respectively, vs. 4.37 mg), statistical analysis yielded no significance because of the small number of patients carrying these genotypes. A significantly lower maintenance dose was observed in the subgroup of heterozygous *1/*3 genotype patients (p=0.022). These preliminary results suggest a significant association of the CYP2C9 polymorphism with the warfarin dose and underline the importance of pre-therapeutic genotyping to identify the subjects likely to develop undesirable drug effects.

CYP2D6 genotyping in patients on psychoactive drug therapy

Abstract The polymorphic isoenzyme CYP2D6 has a major role in the oxidative metabolism of many deal of psychoactive drugs. Its six mutant alleles (null alleles *3, *4, *5, *6, *7 and *8) encode for inactive enzyme molecules. A carrier of two mutant alleles is considered a poor metabolizer phenotype, while a carrier of only one damaged allele is considered an intermediate metabolizer phenotype. The aim of the study was to assess the prevalence of null alleles in a group of psychiatric patients suffering from depression (n=49) and schizophrenia (n=86) in comparison with healthy individuals (n=145) by the method of multiplex allele specific PCR. Only CYP2D6*3,*4 and *6 mutant alleles were found in the study subjects. No significant difference between the depression and control groups was found for allele prevalence, genotype or phenotype distribution (p>0.05). However, a significant difference was observed between schizophrenic patients and controls for allele frequency (p=0.002), genotype distribution (p=0.016), and phenotype prevalence (p=0.018). The odds ratio of 2.542 for 2D6*4 suggested a significant association between this allele and schizophrenia, significantly contributing to poor metabolizer phenotype (odds ratio=5.020). The relationship between CYP2D6 gene polymorphism and side effects in schizophrenic patients undergoing long-term psychoactive drug therapy was investigated. A significant difference was obtained for allele prevalence (p=0.002), genotype (p=0.029), and phenotype (p=0.002) distribution between patients without and with side effects. A relative risk of 2.626 and 5.333 for 2D6*4 and 2D6*6, respectively, and of 7.08 for poor metabolizer phenotype suggested a significant association between the hereditary susceptibility for a particular type of drug metabolism (defect alleles) and side effects. These preliminary r e s u l t s suggest that the CYP2D6 genotyping appears to be useful for predicting risks for side effects of psychoactive drugs in schizophrenic patients, but their usefulness should be further explored.

The glutathione S-transferase polymorphisms in a control population and in Alzheimer's disease patients.

Abstract In this study, we investigated the role of glutathione S-transferase P1 (GSTP1) polymorphisms in the pathogenesis of Alzheimers disease (AD). We genotyped the GSTP1 polymorphisms in exon 5 (A313G) and exon 6 (C341T) by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 56 Croatian patients with AD and 231 controls. Distributions and frequencies of GSTP1 genetic variants were not statistically different between AD patients and healthy controls. Higher frequencies of the mutant genotypes were observed in AD patients (13% for both A313G and C341T) when compared with control subjects (7% for A313G and 8% for C341T), but association of GSTP1 GG (OR 2.057, 95% CI 0.796–5.315, p=0.094) and TT (OR 1.691, 95% CI 0.669–4.270, p=0.514) genotypes with an increased risk of AD was not confirmed by statistical analysis. The frequencies of GSTP1 alleles (A, B, C, D) did not significantly differ between AD patients and controls and they were indicated as follows: 52.7%, 15.2%, 12.5% and 19.6% for AD cases and 58.4%, 14.1%, 14.1% and 13.4% for controls. The estimation of the GSTP1 haplotype distribution showed that GSTP1*A/GSTP1*B and GSTP1*A/GSTP1*C haplotypes were less frequent, while GSTP1*B/GSTP1*B and GSTP1*C/GSTP1*D haplotypes were more frequent in AD patients than in controls. In conclusion, the involvement of GSTP1 alleles in individual susceptibility to AD was not confirmed as statistically significant in the tested Croatian Caucasian population. A possible role of GSTP1 in the complex etiopathogenesis of AD is further discussed, based on observed differences in haplotype distribution and higher frequencies of mutant genotypes in AD patients.

The cytochrome P450 2D6 (CYP2D6) gene polymorphism among breast and head and neck cancer patients

The prevalence of CYP2D6*3 and CYP2D6*4 alleles in normal controls and cancer patients was studied using the reliable PCR-SSCP method. In the control group (n=144), four subjects (2.8%) were found to carry CYP2D6*3 allele (heterozygote), while 30 (20.8%) subjects carried CYP2D6*4 allele (18.8% heterozygotes, 2.1% homozygotes). One (1.3%) of the breast cancer (BC) patients (n=76) carried CYP2D6*3 allele, but 24 (31.6%) carried CYP2D6*4 allele (26.3% heterozygotes, 5.3% homozygotes). In the head and neck cancer (HNC) group (n=56), two (3.6%) patients were heterozygous for CYP2D6*3 mutation and 15 (26.8%) for CYP2D6*4 mutation. Fourteen of 56 (25%) and one of 56 (1. 8%) of these patients carried heterozygous and homozygous mutations, respectively. In controls, 2.1% were identified as poor metabolizers (PM), 76.4% as extensive metabolizers (EM), and 21.5% as intermediate heterozygotes (IEM). In BC group, 5.3, 27.6 and 67.1% were classified as PM, IEM and EM, respectively. In HNC group, the incidence of PM was 1.8, but as many as 28.6% were identified as IEM phenotypes.

Genotyping of CYP2D6 in Parkinsons's Disease

Abstract Parkinsons disease is characterized by progressive degradation of dopaminergic neurons. Cytochrome P450 CYP2D6 enzyme is one of the most investigated and highly polymorphic isoforms, which metabolizes many drugs and is also involved in the metabolism of dopamine. Using allele-specific multiplex PCR, we genotyped 186 subjects for CYP2D6 *3, *4, *6, *7, and *8 alleles in order to estimate allelic, genotype and predicted phenotype frequencies in the control and patient groups, and to investigate the possible statistical difference between Parkinsons disease patients (n=41) and healthy controls (n=145). Parkinsons disease patients were further divided into two subgroups according to Hoehn and Yahr staging of the disease (HY), i.e. groups with HY stage less than 2.5 (HY <2.5; n=27) and more than 2.5 (HY >2.5; n=14). A subgroup of Parkinsons disease patients exhibiting side effects such as “on-off” phenomenon and dyskinesia (both suggesting favorable response to therapy) were compared with a subgroup of patients showing no such response. The preliminary results of this study showed that only the prevalence of CYP2D6 *4 allele differed significantly between the PD patients and control group (20.7% vs. 11.0%; p=0.027; RR=2.1, 95%CI 1.113−3.994). In the HY >2.5 subgroup, the CYP2D6*4 allelic difference was even greater (25.0% vs. 11.0% in controls; p=0.062, RR=2.69, 95%CI 1.090−6.624). Genotype frequencies differed only in the HY >2.5 subgroup, however with a level of significance of p=0.095.

Correlation of UGT1A1 TATA-box polymorphism and jaundice in breastfed newborns-early presentation of Gilbert's syndrome.

Abstract Objective: The etiology of jaundice in otherwise healthy breastfed newborns that can present as early-onset exaggerated physiologic jaundice, or late breast milk jaundice (BMJ), is not yet entirely understood. This study tested the hypothesis that molecular marker for Gilberts syndrome (GS), UGT1A1 TATA-box polymorphism, is associated with this disorders. Methods: We have investigated the UGT1A1 polymorphism frequency and its relation to severity of hyperbilirubinemia and jaundice duration among 220 exclusively breastfed term newborns; 57 of them with non-physiologic hyperbilirubinemia (NH), and 163 with BMJ, and in 187 healthy controls. Results: Significant differences in TA7/7 genotype frequency were established. The highest frequency was observed among the newborns with BMJ (42.0%), intermediate in the NH group (24.6%), while the controls had the lowest TA7/7 frequency (12.8%). Linear increase in TA7/7 frequency was observed depending on the duration of jaundice, peaking at 42.4% in newborns with the longest jaundice duration. Positive correlation between the serum bilirubin levels and the TATA-box length was established in all groups. Conclusion: This study provides evidence that UGT1A1 TATA-box polymorphism is an important risk factor for developing jaundice in term breastfed newborns, presented as either early non-physiologic hyperbilirubinemia or breast milk jaundice. These results further support the original Odells idea of neonatal jaundice as an early presentation of GS.

Detection of CYP2D6*3 and 2D6*4 Allelic Variants by PCR-Restriction Fragment Length Polymorphism

Abstract The mutant of CYP2D6*3 allele with A2637 deletion in exon 5 and the mutant of CYP2D6*4 allele G1934→A, splice site defect are among the most common polymorphic alleles of CYP2D6 gene, resulting in a decreased or no activity of CYP isoenzyme. In this study, a reliable polymerase chain reaction-restriction fragment length polymorphism method for identification of CYP2D6*3 and CYP2D6*4 alleles was used to investigate the genotype and phenotype prevalence in the groups of normal controls, and of cirrhosis and cancer patients. The results showed none of 36 controls genotyped for 2D6*3 and 2D6*4 allele to have the 2D6*3 allele with frameshift mutation in exon 5, while 33 % (n=12) were found to bear the 2D6*4 allele with G to A mutation at the intron 3—exon 4 junction. In breast cancer patients (n=35) genotyped for 2D6*3 and 2D6*4 alleles, none with 2D6*3 allele was found either, but 60 % (n=18) were found to bear the 2D6*4 allele. In patients with head and neck squamous cell cancer, there was only one subject with 2D6*3 allele and he was heterozygous. Among them, as many as ten (40 %) patients were found to bear 2D6*4 allele. In the cirrhosis group, none of the patients was found to have the 2D6*3 allele, while the CYP2D6*4 allele was found in 23 % (n=6) patients. The phenotype predicted according to the genotype was as follows: in the control group, 3% of individuals were identified as poor metabolizers, 70 % as extensive metabolizers, and 27 % as heterozygote extensive metabolizers. In the group of breast cancer, 7% of the patients were identified as poor metabolizer, 57 % as extensive metabolizer and 36% as phenotype. In squamous cell cancer and cirrhosis patients, the incidence of poor metabolizer was zero, and of heterozygotes extensive metabolizer 42 % and 31 %, respectively.

Rare TA repeats in promoter TATA box of the UDP glucuronosyltranferase (UGT1A1) gene in Croatian subjects.

Abstract Background: Gilberts syndrome is a chronic or recurrent mild unconjugated hyperbilirubinemia caused by decreased activity of UDP glucuronosyltranferase (UGT1A1). The most common cause of Gilberts syndrome in Caucasians is homozygous variant of the A(TA)7TAA promoter polymorphism. Alleles with five or eight TA repeats have also been described, but they are very rare in Caucasian populations. Methods: Over a 6-year period (2001–2006), 1109 subjects with suspected Gilberts syndrome were included in this study. Genotyping of (TA)6 and (TA)7 alleles was performed using high-resolution electrophoretic separation of amplified PCR products on Spreadex EL300 gels. In seven subjects, aberrant electrophoretic patterns were observed and additionally sequenced on an ABI Prism 310 Genetic Analyzer. Results: Genotype distributions for 1102 subjects with (TA)6 or (TA)7 alleles were as follows: 54.10%, 26.33% and 18.94% for the (TA)7/(TA)7, (TA)6/(TA)7 and (TA)6/(TA)6, respectively. Sequencing of seven samples that could not be identified as one of these alleles identified four subjects with the (TA)5/(TA)7, two with the (TA)7/(TA)8 and one with the (TA)6/(TA)8 genotype. Conclusion: Genotyping of TA repeats in the promoter region of the UGT1A1 gene revealed the presence of rare alleles with five or eight TA repeats, with a very high frequency of the (TA)7 allele in subjects suspected of having Gilberts syndrome. Clin Chem Lab Med 2008;46:174–8.

Detection of Factor V Leiden by PCR-SSCP using GMATM Precast Elchrom Scientific Gels

Genetic abnormalities in hemostatic proteins associated with hypercoagulability are an important hereditary risk factor for venous thrombosis. Several genetic mutations that cause hereditary disorders predisposing to thrombosis have been described, point mutation in the coagulation factor V gene (FV:R506Q), called factor V Leiden, being the most common of them. A new inexpensive and simple polymerase chain reaction-single-strand polymorphism (PCRSSCP) based method for detection of this genetic abnormality is reported. The study population consisted of 150 subjects whose factor V genotype was previously determined by PCR-RFLP method using the Mnl I restriction endonuclease. A 223-bp fragment containing the G1692-A (Arg 506-Gln) polymorphic site in exon 10 of the factor V gene was amplified, denatured, and run overnight on the commercially available GMA gels for SSCP. PCR-SSCP analysis showed reproducible and uniform band patterns for FV mutant and wild type alleles. Furthermore, PCR-SSCP results were consistent with those obtained with PCR-RFLP analysis (100%). The described PCR-SSCP procedure is reliable, time-saving, and cost-effective. The method may be considered as a potentially powerful new tool in the routine detection of factor V Leiden.