Multidisciplinary Treatment Intervention in 24 Patients with Oligodontia: A Case-Cohort Study.

PURPOSE: To characterize the multidisciplinary treatment intervention for patients with nonsyndromic oligodontia, focusing on both the preprosthodontic intervention and the type of prosthodontic and functional occlusal units at the end of treatment. MATERIALS AND METHODS: A retrospective study on the multidisciplinary treatment of 24 patients with agenesis of 8 to 22 (median 15) permanent teeth was carried out by reviewing the patients' medical records, preprosthodontic surgical and orthodontic procedures, and the final dental and prosthodontic status. RESULTS: A total of 23 patients underwent orthodontic treatment, and one-third of them had additional orthognathic surgery. Presurgical intervention involved bone augmentation in 20 patients and insertion of 2 to 16 implants per patient (median 8). The number of implants was positively correlated with the number of missing teeth (P = .004). At the end of treatment, the number of functional occlusal units ranged from 20 to 28 (median 24). A single-tooth crown was mounted on 167 implants, 32 implants were part of a fixed partial denture, and 29 fixed partial dentures were tooth-borne. CONCLUSION: The treatment of patients with severe oligodontia is comprehensive and complex. Irrespective of the number of congenitally missing teeth, the final functional occlusion consisted of a minimum of 20 units, which in addition to permanent teeth included preserved deciduous teeth, implants, and fixed partial dentures.

Effect of ACE insertion/deletion and 12 other polymorphisms on clinical outcomes and response to treatment in the LIFE study.

OBJECTIVE: This pharmacogenetics substudy from the Losartan Intervention for Endpoint reduction in Hypertension study in patients with hypertension and left ventricular hypertrophy (LVH) treated with the angiotensin receptor blocker losartan versus the beta-blocker atenolol for 4.8 years tested whether the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene and 12 other previously well-characterized polymorphisms of hypertension susceptibility genes affected blood pressure reduction, heart rate reduction, cardiovascular events, and/or response to treatment. These polymorphisms were chosen because they could affect blood pressure control or the pharmacological action of losartan or atenolol. METHODS: We genotyped 3503 patients, 1774 on losartan and 1729 on atenolol. RESULTS: ACE and the 12 other genotypes did not affect the reduction in systolic blood pressure, diastolic blood pressure, pulse pressure, mean arterial pressure, or heart rate, or treatment differences between losartan and atenolol on these endpoints, as assessed by general linear models. Also, ACE and the 12 other genotypes did not affect risk of the primary composite endpoint or its components stroke, myocardial infarction, and cardiovascular death, or treatment differences between losartan and atenolol on these endpoints, as assessed by Cox proportional hazards models including baseline Framingham risk score and LVH. CONCLUSION: ACE insertion/deletion and 12 other polymorphisms of hypertension susceptibility genes did not affect blood pressure reduction, heart rate reduction, or cardiovascular events in patients with hypertension and LVH, or treatment differences between losartan and atenolol on these endpoints. These results suggest that the observed effects of losartan versus atenolol in the Losartan Intervention for Endpoint reduction in hypertension study do not depend on ACE and 12 other polymorphisms of hypertension susceptibility genes.

CYP2C9 genetic variants and losartan oxidation in a Turkish population.

OBJECTIVE: Cytochrome P(450) 2C9 (CYP2C9) is a polymorphic enzyme catalysing the metabolism of several important drugs. Losartan has recently been suggested as a selective probe for CYP2C9 metabolic activity. The aim of the study was to determine the activity of CYP2C9, using losartan as a probe drug, in relation to CYP2C9 genotype in healthy Turkish subjects. METHODS: A single oral dose of 25 mg losartan was given to 85 Turkish unrelated subjects. Concentrations of losartan and its carboxylic acid metabolite, E3174, were analysed by means of high-performance liquid chromatography in urine collected for 8 h. The CYP2C9 genotypes were determined in 85 subjects using polymerase chain reaction-based endonuclease digestion methods specific for CYP2C9*2 and *3. Losartan oxidation was also studied in vitro, using human CYP2C8 and CYP2C9 enzymes expressed in yeast. RESULTS: The frequencies of the allelic variants CYP2C9*2 and CYP2C9*3 were 0.100 and 0.088, respectively. The urinary losartan/E3174 ratio was significantly higher in subjects with CYP2C9*1/*3 genotype (median 2.35, n=12) than in subjects with CYP2C9*1/*1 (0.71, n=58) and *1/*2 (0.85, n=10) genotypes ( P<0.05). In contrast to CYP2C9, no E3174 was formed by CYP2C8 in vitro. CONCLUSION: The urinary losartan to E3174 metabolic ratio after a 25-mg losartan dose was found to be a safe and useful phenotyping assay for CYP2C9 activity in vivo. CYP2C9*3 variant allele is a major determinant of the enzyme activity, and it decreases losartan metabolism significantly, while CYP2C9*2 allele has less impact on enzyme function.

The impact of CYP2C9 genetics and oral contraceptives on cytochrome P450 2C9 phenotype.

CYP2C9-dependent drug metabolism is subject to large interindividual variation. To some extent, this is explained by genetic polymorphism with expression of enzyme variants that differ in catalytic activity. The aim of this study was to characterize the variation in CYP2C9 phenotype in relation to genotype, with further analysis of the CYP2C9 gene in metabolic outliers. A study population of 126 healthy white subjects were recruited and genotyped for the variant alleles, CYP2C9*1-3. In CYP2C9 phenotyping with losartan, three subpopulations were distinguished that differed in the number of CYP2C9*3 alleles (0, 1, or 2). A three-fold higher metabolic ratio (MR; urinary losartan/carboxymetabolite) was found comparing CYP2C9*1/*3 (n = 20) to CYP2C9*1/*1 (n = 81), but there was considerable variation within each genotype. Subjects genotyped as CYP2C9*1/*1, but with an unexpectedly slow oxidation of losartan, were selected for DNA-sequencing analysis of the CYP2C9 gene. Interestingly, single nucleotide polymorphisms (SNPs) could not be identified either in the 5'-flanking region, the nine exons, or exon-intron boundaries. However, sequencing of the CYP2C9 gene was also carried out in patients genotyped as CYP2C9*1/*1 but with an exceptionally low steady-state clearance of S-warfarin. Here, five different SNPs were identified. In further analysis of the healthy volunteers, it became evident that women on oral contraceptives (OCs) had slower oxidation of losartan (MR of losartan: 1.7) than women without OCs (MR of losartan: 0.86). This novel finding was not explained by a different frequency of variant alleles. In summary, CYP2C9 genotype and oral contraceptives both contribute to a large interindividual variation in CYP2C9 activity.

Bioactivation of cyclophosphamide: the role of polymorphic CYP2C enzymes.

Several-fold differences have been observed among patients in the biotransformation of cyclophosphamide. The aim of this study was to investigate the contribution of CYP2C9 and CYP2C19 and their polymorphisms to the variability of cyclophosphamide activation. The formation of 4-hydroxycyclophosphamide was studied in microsomes from a total of 32 different genotyped human livers, as well as in yeast microsomes expressing different genetic variants of CYP2C9 and CYP2C19. The kinetic data obtained in the yeast system revealed that the intrinsic clearance (V(max)/K(m)) of cyclophosphamide by CYP2C9.2 and CYP2C9.3 samples was approximately threefold lower than that by CYP2C9.1. However, in liver microsomes, there were no statistically significant differences in the intrinsic clearance of 4-hydroxycyclophosphamide formation between the group of seven CYP2C9*1/*1 livers and the remaining nine with one or two variant CYP2C9 alleles ( P>0.7). We found a statistically significant correlation ( r(s)=0.65, P=0.003) between 4-hydroxylation of cyclophosphamide and 5'-hydroxylation of R-omeprazole, a measure of CYP2C19 activity in human liver microsomes ( n=19). No correlation was found between 4-hydroxylation of cyclophosphamide and the formation rate of hydroxycelecoxib, mainly catalysed by CYP2C9 ( r(s)=0.17, P=0.55, n=32). In conclusion, based on the correlation with the formation of R-5'-hydroxyomeprazole, CYP2C19 may partly contribute to the bioactivation of cyclophosphamide in human liver microsomes, while the role of CYP2C9 appears minor.

Analysis of CYP2C9*5 in Caucasian, Oriental and black-African populations.

OBJECTIVE: CYP2C9 is a polymorphic gene with at least six known allelic variants (CYP2C9*1 to *6). CYP2C9*5 has been recently described in African-Americans. The lower activity of CYP2C9*5 encoded enzyme than *1 has been reported for the S-warfarin 7-hydroxylation in vitro. The aim of the present study was to develop an assay for the analysis of this variant and to determine the frequency of this polymorphism in different ethnic populations. MATERIALS AND METHODS: A PCR-based endonuclease digestion method, using a mismatched forward primer that introduced a recognition site for AvaII in all the CYP2C9 genotypes except CYP2C9*5, is described. DNA samples from 150 Ethiopians, 183 Tanzanians, 200 Caucasians from Sweden and 150 Orientals from Korea were screened for this variant allele. RESULTS AND CONCLUSION: The CYP2C9*5 allele was analysed using a polymerase chain reaction-based endonuclease method, and it was found in three Tanzanians (allele frequency, 0.0082) but not in Ethiopians, Caucasians or Orientals.

Oxidation of celecoxib by polymorphic cytochrome P450 2C9 and alcohol dehydrogenase.

AIMS: Celecoxib is a novel selective cyclooxygenase-2 inhibitor, which is subject to extensive hepatic metabolism. The aims of the present in vitro investigation were 1) to compare the rate of celecoxib hydroxylation by different genetic variants of cytochrome P450 2C9 (CYP2C9), and 2) to identify the enzyme(s) involved in the formation of the major metabolite carboxycelecoxib. METHODS: Hydroxycelecoxib formation was studied in human liver microsomes from 35 genotyped livers, as well as in yeast microsomes with recombinant expression of different P450 variants. Carboxycelecoxib formation was studied in liver microsomes incubated in the absence or presence of liver cytosol. The metabolites were identified and quantified by h.p.l.c. In addition, hydroxycelecoxib oxidation by different variants of recombinant human alcohol dehydrogenase (ADH1-3) was analysed by spectrophotometric monitoring of NADH generation from NAD+. RESULTS: The intrinsic clearance of celecoxib hydroxylation was significantly lower for yeast-expressed CYP2C9.3 (0.14 ml min-1 nmol-1 enzyme) compared with CYP2C9.1 (0.44 ml min-1 nmol-1 enzyme). In human liver microsomes, a significant 2-fold decrease in the rate of hydroxycelecoxib formation was evident in CYP2C9*1/*3 samples compared with CYP2C9*1/*1 samples. There was also a marked reduction (up to 5.3 times) of hydroxycelecoxib formation in a liver sample genotyped as CYP2C9*3/*3. However, the CYP2C9*2 samples did not differ significantly from CYP2C9*1 in any of the systems studied. Inhibition experiments with sulphaphenazole (SPZ) or triacetyloleandomycin indicated that celecoxib hydroxylation in human liver microsomes was mainly dependent on CYP2C9 and not CYP3A4. The further oxidation of hydroxycelecoxib to carboxycelecoxib was completely dependent on liver cytosol and NAD+. Additional experiments showed that ADH1 and ADH2 catalysed this reaction in vitro with apparent K m values of 42 micro m and 10 micro m, respectively, whereas ADH3 showed no activity. CONCLUSIONS: The results confirm that CYP2C9 is the major enzyme for celecoxib hydroxylation in vitro and further indicate that the CYP2C9*3 allelic variant is associated with markedly slower metabolism. Furthermore, it was shown for the first time that carboxycelecoxib formation is dependent on cytosolic alcohol dehydrogenase, presumably ADH1 and/or ADH2.

Paeoniae Radix, a traditional Chinese medicine, and CYP2C9 activity.

Paeoniae Radix (PR) is a commonly used traditional Chinese medicine. A slight effect of PR on the pharmacokinetics of phenytoin that is mainly metabolised by CYP2C9 has been reported. The aim of this pilot study was to clarify if PR has an effect on losartan oxidation used as a measure of CYP2C9 activity. Three healthy volunteers received a single oral dose of losartan before and after PR treatment. Losartan and E-3174, an active metabolite of losartan, were analysed in 8 hour urine. PR did not seem to have an effect on CYP2C9 activity when the losartan/E-3174 ratios were compared before and after PR treatment (P = 0.56) although a larger study would need to be undertaken to confirm this finding.