Analysis of glutamate homeostasis by overexpression of Fd-GOGAT gene in Arabidopsis thaliana.

Glutamate plays a central role in nitrogen flow and serves as a nitrogen donor for the production of amino acids. In plants, some amino acids work as buffers: during photorespiration, ammonium derived from the conversion of glycine to serine is promptly reassimilated into glutamate by the glutamine synthetase (GS-2)/ferredoxin-dependent glutamate synthase (Fd-GOGAT) cycle. The glutamate concentration is relatively stable compared with those of other amino acids under environmental changes. The few studies dealing with glutamate homeostasis have but all used knockouts or mutants of these enzymes. Here, we generated Fd-GOGAT (GLU1)-overexpressing Arabidopsis plants to analyze changes in the amino acid pool caused by glutamate overproduction under different ammonium conditions controlled by CO(2) concentration, light intensity and nitrate concentration. Under photorespiratory conditions with sufficient ammonium supply, aspartate increased and glutamine and glycine decreased, but glutamate barely changed. Under non-photorespiratory conditions, however, glutamate and most other amino acids increased. These results suggest that the synthesized glutamate is promptly converted into other amino acids, especially aspartate. In addition, ammonium supply by photorespiration does not limit glutamate biosynthesis, but glutamine and glycine are important. This study will contribute to the understanding of glutamate homeostasis in plants.

MDR1 C3435T polymorphism has no influence on developing Helicobacter pylori infection-related gastric cancer and peptic ulcer in Japanese.

AIMS: P-glycoprotein, the gene product of multidrug-resistant transporter-1 (MDR1), confers multidrug resistance against antineoplastic agents but also affects the kinetic disposition of some drugs and carcinogens. MDR1 C3435T polymorphism influences the development of colon cancer and adult acute myeloid leukemia by the association with transporting carcinogen. The aim of this study was to clarify the association of MDR1 C3435T polymorphism with susceptibility to gastric cancer and peptic ulcers in patients with Japanese H. pylori infection. MAIN METHODS: We assessed the MDR1 C3435T polymorphism in H. pylori-positive gastritis alone patients (n=150), gastric cancer (n=292), gastric ulcer (n=215), and duodenal ulcer (n=163) and H. pylori-negative subjects (n=168) as control by a PCR-based method. KEY FINDINGS: No significant difference existed in frequencies of MDR1 C3435T polymorphisms between H. pylori-negative controls and H. pylori-positive gastritis alone patients. Moreover, MDR1-3435 T allele carriage didn't affect the risk of gastric cancer or peptic ulcer development. The age- and sex-adjusted odds ratios (ORs) of MDR1 3435 T allele carriers relative to the C/C genotype group for gastric cancer, gastric ulcer and duodenal ulcer risk were 0.96 (95%CI: 0.56-1.66), 1.16 (95%CI: 0.72-1.84) and 1.00 (95%CI: 0.61-1.62), respectively. SIGNIFICANCE: In this preliminary data, the association with MDR1 C3435T polymorphism and risk for developing H. pylori-related gastric cancer and peptic ulcer in Japanese was low. P-glycoprotein might not be involved in the carcinogenesis of H. pylori-related gastric cancer.

Maintenance time of sedative effects after an intravenous infusion of diazepam: a guide for endoscopy using diazepam.

AIM: To examine whether the sedative effects assessed by psychomotor tests would depend on the cytochrome P450 (CYP) 2C19 genotypes after an infusion regimen of diazepam commonly used for gastrointestinal endoscopy in Japan. METHODS: Fifteen healthy Japanese volunteers consisting of three different CYP2C19 genotype groups underwent a critical flicker fusion test, an eye movement analysis and a postural sway test as a test for physical sedative effects, and a visual analog scale (VAS) symptom assessment method as a test for mental sedative effects during the 336 h period after the intravenous infusion of diazepam (5 mg). RESULTS: The physical sedative effects assessed by the critical flicker test continued for 1 h (t values of 5 min, 30 min and 60 min later: 4.35, 5.00 and 3.19, respectively) and those by the moving radial area of a postural sway test continued for 3 h (t values of 5 h, 30 h, 60 min and 3 h later: -4.05, -3.42, -2.17 and -2.58, respectively), which changed significantly compared with the baseline level before infusion (P<0.05). On the other hand, the mental sedative effects by the VAS method improved within 1 h. The CYP2C19 genotype-dependent differences in the postinfusion sedative effects were not observed in any of the four psychomotor function tests. CONCLUSION: With the psychomotor tests, the objective sedative effects of diazepam continued for 1 h to 3 h irrespective of CYP2C19 genotype status and the subjective sedative symptoms improved within 1 h. Up to 3 h of clinical care appears to be required after the infusion of diazepam, although patients feel subjectively improved.

DNA topoisomerase II interacts with Lim15/Dmc1 in meiosis.

Lim15/Dmc1 is a meiosis specific RecA-like protein. Here we propose its participation in meiotic chromosome pairing-related events along with DNA topoisomerase II. Analysis of protein-protein interactions using in vitro binding assays provided evidence that Coprinus cinereus DNA topoisomerase II (CcTopII) specifically interacts with C.cinereus Lim15/Dmc1 (CcLim15). Co-immunoprecipitation experiments also indicated that the CcLim15 protein interacts with CcTopII in vivo. Furthermore, a significant proportion of CcLim15 and CcTopII could be shown to co-localize on chromosomes from the leptotene to the zygotene stage. Interestingly, CcLim15 can potently activate the relaxation/catenation activity of CcTopII in vitro, and CcTopII suppresses CcLim15-dependent strand transfer activity. On the other hand, while enhancement of CcLim15's DNA-dependent ATPase activity by CcTopII was found in vitro, the same enzyme activity of CcTopII was inhibited by adding CcLim15. The interaction of CcLim15 and CcTopII may facilitate pairing of homologous chromosomes.

Initial 48-hour acid inhibition by intravenous infusion of omeprazole, famotidine, or both in relation to cytochrome P450 2C19 genotype status.

BACKGROUNDS AND AIMS: Faster and stronger acid inhibition is required for the treatment of hemorrhage from peptic ulcers. We compared the effects of intravenous infusion regimens of a proton pump inhibitor (PPI) alone, a histamine 2 receptor antagonist (H2RA) alone, and the combination of a PPI with an H2RA on acid inhibition in the early postadministration phase in relation to cytochrome P450 (CYP) 2C19 genotype status. METHODS: Fifteen Helicobacter pylori-positive volunteers with 3 different CYP2C19 genotypes were administered twice-daily intravenous infusions of 20 mg famotidine alone, 20 mg omeprazole alone, 10 mg omeprazole plus 10 mg famotidine (half-concomitant regimen), and 20 mg omeprazole plus 20 mg famotidine (full-concomitant regimen) for 2 days. The subjects underwent 48-hour intragastric pH monitoring. RESULTS: In homozygous extensive metabolizers (EMs) the median first 24-hour intragastric pH with the full-concomitant regimen was 4.8 (range, 4.5-5.4), which was significantly higher than that with omeprazole alone (3.9 [range, 2.6-4.7], P=.043) or famotidine alone (4.4 [range, 3.8-4.9], P=.043). In heterozygous EMs and poor metabolizers the respective median first 24-hour pH values attained with omeprazole alone (5.8 [range, 4.3-6.3] and 6.1 [range, 5.3-7.4]) and the full-concomitant regimen (5.8 [range, 5.1-6.4] and 5.8 [range, 5.4-6.2]) were significantly higher than those attained with famotidine alone (4.1 [range, 3.9-6.5] and 4.7 [range, 3.7-5.7], P=.043 for all). CONCLUSIONS: For faster and stronger acid inhibition, the concomitant infusion regimen of a PPI and an H2RA appears to be therapeutically useful in homozygous and heterozygous EMs, but omeprazole alone appears to be sufficient in poor metabolizers of CYP2C19.

Influences of proinflammatory and anti-inflammatory cytokine polymorphisms on eradication rates of clarithromycin-sensitive strains of Helicobacter pylori by triple therapy.

BACKGROUNDS AND AIMS: Polymorphisms of proinflammatory cytokines, such as interleukin (IL) 1beta and tumor necrosis factor (TNF) alpha, are associated with individual differences in gastric mucosal inflammation and acid inhibition in response to Helicobacter pylori infection. We investigated whether inflammation-related cytokine polymorphisms would influence the eradication rates of H pylori by a triple-therapy regimen. METHODS: Three hundred sixty patients infected with clarithromycin-sensitive strains of H pylori were genotyped for IL1B -511, IL1RN, TNFA -857/-863/-1,031, IL10 -1,082/-819/-592, and CYP2C19 and underwent triple therapy for 1 week with a proton pump inhibitor (20 mg omeprazole, 30 mg lansoprazole, or 10 mg rabeprazole) twice daily, 400 mg clarithromycin twice daily, and 750 mg amoxicillin (INN, amoxicilline) twice daily. The influences of the previously mentioned polymorphisms on the eradication rates were analyzed. RESULTS: The intention-to-treat-based total eradication rate was 83.6% (301/360). The logistic regression analysis revealed that polymorphisms of CYP2C19 and IL1B -511 were independently associated with the eradication rates, but other cytokine polymorphisms were not associated with these rates. The eradication rates in patients with IL1B -511 C/C, C/T, and T/T genotypes were 72.2% (70/97), 87.7% (164/187), and 88.2% (67/76), respectively (P = .0017). When patients were stratified by CYP2C19 genotype status, IL1B -511 genotype-dependent differences in eradication rates were observed in homozygous extensive metabolizers (EMs) but not in heterozygous EMs and poor metabolizers of CYP2C19. The eradication rate in homozygous EM patients with the IL1B -511 C/C genotype was quite low (51.1% [22/43]). CONCLUSIONS: IL1B -511 polymorphism, but not IL1RN, TNFA, or IL10 polymorphism, is one of the determinants of triple therapy for clarithromycin-sensitive strains of H pylori in CYP2C19 homozygous EMs.

Sumoylation of a meiosis-specific RecA homolog, Lim15/Dmc1, via interaction with the small ubiquitin-related modifier (SUMO)-conjugating enzyme Ubc9.

Sumoylation is a post-translational modification system that covalently attaches the small ubiquitin-related modifier (SUMO) to target proteins. Ubc9 is required as the E2-type enzyme for SUMO-1 conjugation to targets. Here, we show that Ubc9 interacts with the meiosis-specific RecA homolog, Lim15/Dmc1 in the basidiomycete Coprinus cinereus (CcLim15), and mediates sumoylation of CcLim15 during meiosis. In vitro protein-protein interaction assays revealed that CcUbc9 interacts with CcLim15 and binds to the C-terminus (amino acids 105-347) of CcLim15, which includes the ATPase domain. Immunocytochemistry demonstrates that CcUbc9 and CcLim15 colocalize in the nuclei from the leptotene stage to the early pachytene stage during meiotic prophase I. Coimmunoprecipitation experiments indicate that CcUbc9 interacts with CcLim15 in vivo during meiotic prophase I. Furthermore, we show that CcLim15 is a target protein of sumoylation both in vivo and in vitro, and identify the C-terminus (amino acids 105-347) of CcLim15 as the site of sumoylation in vitro. These results suggest that sumoylation is a candidate modulator of meiotic recombination via interaction between Ubc9 and Lim15/Dmc1.

Role of pfmdr1 mutations on chloroquine resistance in Plasmodium falciparum isolates with pfcrt K76T from Papua New Guinea.

The N86Y mutation in pfmdr1 is reported to play an additional role for the chloroquine resistance in Plasmodium falciparum isolates. However, not much has been done to clarify whether this mutation augments the level of chloroquine resistance in the isolates harboring pfcrt K76T mutation. We compared the in vitro chloroquine efficacy between pfcrt K76T mutant parasites with or without N86Y mutation from Papua New Guinea. A total of 57 isolates (4% sensitive, 14% borderline, and 82% resistant) were successfully tested in vitro for chloroquine sensitivity. We found a slightly higher effective concentration of chloroquine needed to inhibit P. falciparum by 50% (mean EC50=107 nM) in isolates with the pfcrt K76T+pfmdr1 N86Y than that in isolates with the pfcrt K76T+pfmdr1 N86 (EC50=88 nM), but this difference was not statistically significant. A significant non-random association was observed between the pfcrt K76T and pfmdr1 N86Y alleles. Our results suggest that the pfmdr1 N86Y mutation plays a compensatory role to chloroquine-resistant isolates under a chloroquine pressure while it may also augment the level of chloroquine resistance in the K76T parasites to a small extent.

Coprinus cinereus DNA ligase I during meiotic development.

DNA ligase I is thought to be essential for DNA replication, repair and recombination, at least in the mitotic cell cycle, but whether this is also the case during the meiotic cell cycle is still obscure. To investigate the role of DNA ligase I during the meiotic cell cycle, we cloned the Coprinus cinereus DNA ligase I cDNA (CcLIG1). Northern blotting analysis indicated that CcLIG1 is expressed not only in the premeiotic S-phase but also during the meiotic cell cycle itself. Especially, intense signals were observed in the leptotene and zygotene stages. Western blotting analysis indicated that CcLIG1 is expressed through the meiotic cell cycle and immunofluorescence also showed CcLIG1 protein staining in meiotic cells. Interestingly, the patterns was similar to that for the C. cinereus proliferating cell nuclear antigen gene (CcPCNA) and immunoprecipitation analysis suggested that CcPCNA binds to CcLIG1 in crude extracts of meiotic prophase I tissues. Based on these observations, relationships and roles during the meiotic cell cycle are discussed.

Comparison of an increased dosage regimen of rabeprazole versus a concomitant dosage regimen of famotidine with rabeprazole for nocturnal gastric acid inhibition in relation to cytochrome P450 2C19 genotypes.

BACKGROUND AND OBJECTIVE: A concomitant dosage regimen of a histamine 2 receptor antagonist with a proton pump inhibitor (PPI) effectively decreases the incidence of nocturnal acid breakthrough, which is one of the problems encountered when acid-related diseases are treated with a PPI alone. We compared the effectiveness of an increased dosage regimen of rabeprazole with that of a concomitant dosage regimen of rabeprazole with famotidine, relative to cytochrome P450 (CYP) 2C19 genotype status, on nocturnal acid inhibition. METHODS: Fifteen Helicobacter pylori-negative volunteers, consisting of 5 homozygous extensive metabolizers (EMs), 6 heterozygous EMs, and 4 poor metabolizers (PMs) of CYP2C19, took 20 mg rabeprazole, 40 mg rabeprazole, and 20 mg rabeprazole plus 20 mg famotidine at bedtime (at 10 PM) for 8 days. The subjects then underwent 24-hour intragastric pH monitoring on day 8. RESULTS: For the 20-mg rabeprazole, 40-mg rabeprazole, and concomitant dosage regimens, the median percent times and ranges when nocturnal intragastric pH values were lower than 4.0 were 78.8% (47.5%-98.0%), 45.3% (29.0%-52.2%), and 15.5% (0.0%-40.8%), respectively, for homozygous EMs; 51.0% (7.0%-91.6%), 41.3% (33.0%-59.0%), and 18.5% (8.4%-31.9%), respectively, for heterozygous EMs; and 4.5% (2.0%-31.2%), 9.5% (0.0%-31.1%), and 9.3% (0.0%-14.7%), respectively, for PMs. Although significant differences in acid inhibition between the different CYP2C19 genotypes were observed when rabeprazole alone was given (P = .016 for 20 mg rabeprazole and P = .023 for 40 mg rabeprazole), such differences were not observed when famotidine was concomitantly given (P = .206). CONCLUSIONS: The combination regimen of famotidine plus rabeprazole is more effective for nocturnal acid inhibition in homozygous and heterozygous EMs than the increased dosage regimen of rabeprazole. This concomitant therapy could be a rescue regimen for patients with nocturnal acid breakthrough refractory to a standard PPI therapy who are likely to be CYP2C19 EMs.

Influence of CYP2C19 pharmacogenetic polymorphism on proton pump inhibitor-based therapies.

Proton pump inhibitors (PPIs), such as omeprazole, lansoprazole, rabeprazole, esomeprazole, and pantoprazole, are mainly metabolized by CYP2C19 in the liver. There are genetically determined differences in the activity of this enzyme. The genotypes of CYP2C19 are classified into the three groups, rapid extensive metabolizer (RM), intermediate metabolizer (IM), and poor metabolizer (PM). The pharmacokinetics and pharmacodynamics of PPIs depend on CYP2C19 genotype status. Plasma PPI levels and intragastric pHs during PPI treatment in the RM group are lowest, those in the IM group come next, and those in the PM group are highest of the three groups. These CYP2C19 genotype-dependent differences in pharmacokinetics and pharmacodynamics of PPIs influence the cure rates for the gastro-esophageal reflux disease and H. pylori infection by PPI-based therapies. For the better PPI-based treatment, doses and dosing schemes of PPIs should be optimized based on CYP2C19 genotype status.

Pharmacogenetic roles of CYP2C19 and CYP2B6 in the metabolism of R- and S-mephobarbital in humans.

OBJECTIVES AND METHODS: We assessed the relationship between the metabolism of R- and S-mephobarbital (MPB) and genetic polymorphisms of cytochrome P450 (CYP) 2C19 and CYP2B6. Nine homozygous extensive metabolizers (homo-EMs, 2C19*1/2C19*1) of CYP2C19, ten heterozygous EMs (hetero-EMs, 2C19*1/2C19*2, 2C19*1/2C19*3) and eleven poor metabolizers (PMs, 2C19*2/2C19*2, 2C19*3/2C19*3, 2C19*2/2C19*3) recruited from a Japanese population, received an oral 200 mg-dose of racemic MPB. Blood and urine samples were collected, and R-MPB, S-MPB and the metabolites, phenobarbital (PB) and 4'-hydroxy-MPB, were measured. Each subject was also genotyped for CYP2B6 gene. RESULTS: The mean area under the plasma concentration-time curve (AUC) of R-MPB was 92-fold greater in PMs than in homo-EMs. R/S ratios for AUC of MPB were much higher in PMs than in EMs (homo- and hetero-). The cumulative urinary excretion of 4'-hydroxy-MPB up to 24 h postdose was 21-fold less in PMs than in homo-EMs. The metabolic ratio of AUCPB/(AUCS-MPB + AUCR-MPB) was higher in PMs than in EMs (homo- and hetero-). In addition, this metabolic ratio was lower in the carriers of CYP2B6*6 compared with that in its non-carriers. CONCLUSIONS: Our results indicate that the 4'-hydroxylation of R-MPB is mediated via CYP2C19 and that the rapid 4'-hydroxylation of R-MPB results in a marked difference in the pharmacokinetic profiles between R-MPB and S-MPB in the different CYP2C19 genotypic individuals. In addition, a minor fraction of the interindividual variability in PB formation from MPB may be explainable by the CYP2B6*6 allele.

Analysis of Sepik populations of Papua New Guinea suggests an increase of CYP2C19 null allele frequencies during the colonization of Melanesia.

The cytochrome P450 (CYP) isozyme CYP2C19 metabolizes clinically important drugs, including the anti-malarial proguanil currently used for multi-drug resistant Plasmodium falciparum malaria. CYP2C19 activity varies among geographical regions due to high frequencies of two null alleles (CYP2C19*2/*3) in Asian and especially Pacific populations. Previously, we reported an unprecedentedly high frequency of CYP2C19 poor metabolizers (PM) within populations of Vanuatu, which suggested even higher PM frequencies in Papua New Guinea. We examined CYP2C19 allele frequencies of three malarious populations from inland East Sepik Province, Papua New Guinea to evaluate this prediction and the use of proguanil in malaria treatment programs. These Papua New Guinean populations have PM frequencies intermediate between island South-east Asia and Vanuatu, most likely resulting from genetic drift during the settlement of the Pacific. This study highlights the medical consequences of population origins and the need for a better understanding of the genetic diversity of our global species.

Decreased coumarin 7-hydroxylase activities and CYP2A6 expression levels in humans caused by genetic polymorphism in CYP2A6 promoter region (CYP2A6*9).

One of seven poor metabolizers of coumarin found in Thai subjects was previously genotyped as heterozygote for the CYP2A6*4 (whole deletion) and CYP2A6*9. Thus, we aimed to investigate the relationship between the genetic polymorphism in the TATA box of the CYP2A6 gene (CYP2A6*9), expression levels of CYP2A6 mRNA and coumarin 7-hydroxylase activities in human livers. Levels of CYP2A6 mRNA were quantified by real-time quantitative reverse transcriptase-polymerase chain reaction. The mean expression levels of CYP2A6 mRNA in individuals with CYP2A6*1/*4, CYP2A6*1/*9 and CYP2A6*4/*9 were 58%, 71% and 21% of the individuals genotyped as CYP2A6*1/*1, respectively. The mean in-vitro coumarin 7-hydroxylase activities in subjects carrying CYP2A6*1/*4, CYP2A6*1/*9 and CYP2A6*4/*9 were 41%, 71% and 12%, respectively, compared to those of the subjects judged as wild-type. Vmax values for coumarin 7-hydroxylation in the liver microsomes from human subjects with genotypes of CYP2A6*1/*1, CYP2A6*1/*4, CYP2A6*1/*9 and CYP2A6*4/*9 were 0.58, 0.26, 0.44 and 0.13 nmol/min/nmol total P450, respectively. CYP2A6 protein levels in human liver microsomes with the CYP2A6*4 and the CYP2A6*9 alleles were markedly decreased. These results suggest that the genetic polymorphism in the promoter region of the CYP2A6 gene (CYP2A6*9) reduced the expression levels of CYP2A6 mRNA and protein in human livers, resulting in the decrease of coumarin 7-hydroxylase activities. Individuals judged as CYP2A6*4/*9 were expected to be poor metabolizers, having extremely low activity of CYP2A6.

Different dosage regimens of rabeprazole for nocturnal gastric acid inhibition in relation to cytochrome P450 2C19 genotype status.

OBJECTIVE: For the treatment of gastroesophageal reflux disease, intragastric pH should be lower than 4.0 for no more than 4 hours a day (<16.7%). We aimed to develop optimal dosage regimens for rabeprazole to control nocturnal acidity in relation to cytochrome P450 (CYP) 2C19 genotypes. METHODS: Fifteen Helicobacter pylori -negative volunteers, comprising 5 homozygous extensive metabolizers (EMs), 6 heterozygous EMs, and 4 poor metabolizers (PMs) of CYP2C19, took placebo and rabeprazole, at a dose of 20 or 40 mg once daily (at 10 pm ) for 8 days. Plasma rabeprazole concentrations and 24-hour intragastric pH were determined on days 7 and 8, respectively. Because the nocturnal intragastric pH was lower than 4.0 for more than 16.7% of the time with once-daily regimens in homozygous EMs and heterozygous EMs, they were administered 20 mg rabeprazole twice daily (8 am and 10 pm ) or 10 mg rabeprazole 4 times daily (8 am , 12:30 pm , 6 pm , and 10 pm ). RESULTS: With 40 mg rabeprazole once daily, the median percent time with nocturnal pH lower than 4.0 was less than 16.7% in PMs (9.5% [range, 3.0%-31.1%]) but not in homozygous EMs (45.3% [range, 29.0%-52.2%]) ( P = .043) and heterozygous EMs (41.3% [range, 33.0%-59.0%]) ( P = .043). The mean plasma rabeprazole concentrations differed among the different CYP2C19 genotype groups. With 20 mg rabeprazole twice daily and 10 mg rabeprazole 4 times daily, the median percent times with nocturnal pH lower than 4.0 were 5.0% (range, 0.0%-42.0%) and 1.0% (range, 5.0%-7.1%) in heterozygous EMs and 62.0% (range, 10.8%-68.3%) and 14.7% (range, 0.0%-41.7%) in homozygous EMs, respectively, and plasma concentrations were sustained longer than with the once-daily regimens. CONCLUSIONS: We propose that rabeprazole dosage regimens for sufficient acid inhibition are 20 mg once daily for PMs, 20 mg twice daily for heterozygous EMs, and 10 mg 4 times daily for homozygous EMs or heterozygous EMs.

A population phenotyping study of three drug-metabolizing enzymes in Kyushu, Japan, with use of the caffeine test.

OBJECTIVE: We assessed in vivo activities of cytochrome P450 1A2 (CYP1A2), N-acetyltransferase 2, and xanthine oxidase in Japanese residents of Kyushu, the southern island of Japan. METHODS: One hundred eighty-two healthy volunteers (108 men and 74 women) received a 150-mg oral dose of caffeine before they went to sleep. The concentrations of caffeine, caffeine metabolites, and uric acid in their overnight urine samples were analyzed. The CYP2A6 genotypes were determined in 66 of the 182 volunteers to assess whether they affected a metabolic ratio for CYP1A2 activity index. RESULTS: The metabolic ratio for CYP1A2 was not polymorphic, but its mean ratio was greater in smokers than in nonsmokers (P <.05). Twenty subjects (11.0%) were found to be slow acetylators. Twenty subjects were determined to be putative poor metabolizers of xanthine oxidase, and the mean urinary uric acid concentration of those subjects was 53% lower than that of the other subjects (P <.0001). The mean ratio for CYP1A2 obtained from 3 subjects with the CYP2A6(*)4C/CYP2A6(*)4C genotype was greater than the mean ratio from subjects with other genotypes (P <.01) or that from subjects with a wild-type CYP2A6(*)1A allele (P <.05). CONCLUSIONS: Our results suggest that putative poor metabolizers of xanthine oxidase activities exist in a Japanese population and that a decreased 1,7-dimethyluric acid formation from caffeine in poor metabolizers of CYP2A6 appears to affect the metabolic ratio used for the assessment of CYP1A2 activity.

Effect of cytochrome P4502C19 genotypic differences on cure rates for gastroesophageal reflux disease by lansoprazole.

BACKGROUND AND OBJECTIVES: The acid-inhibitory effect of lansoprazole depends on differences in cytochrome P450 (CYP) 2C19 genotypes. We assessed whether therapeutic effects of lansoprazole on gastroesophageal reflux disease (GERD) depended on the CYP2C19 genotype status in relation to the grade of GERD. METHODS: A total of 65 patients with GERD (grades A-D) completed treatment with lansoprazole, by taking 30 mg orally once a day for 8 weeks. The CYP2C19 genotype status of patients was determined by polymerase chain reaction-restriction fragment length polymorphism analysis. Before and after treatment, esophageal endoscopy was performed. GERD was considered to be cured on the basis of endoscopic findings at the end of treatment. Plasma lansoprazole levels could be determined at 3 hours after the last 30-mg dose of lansoprazole in the 27 genotyped patients. RESULTS: Cure rates for GERD depended significantly on the CYP2C19 genotype status, as well as the grade of GERD before treatment. Cure rates in the homozygous extensive, heterozygous extensive, and poor metabolizer groups were 45.8%, 67.9%, and 84.6%, respectively. Cure rates in the groups with GERD grade A, grade B, and grade C or D were 85.0%, 60.0%, and 45.0%, respectively. The cure rate in patients with the homozygous extensive metabolizer genotype of CYP2C19 with a GERD grade of C or D was very low (16.7%). Plasma lansoprazole levels in patients with the homozygous extensive metabolizer genotype were the lowest of the 3 groups. CONCLUSIONS: CYP2C19 genotype status, as well as the grade of GERD before treatment, is one of the determinants for the success or failure of treatment of GERD with lansoprazole. The low cure rate in patients with the homozygous extensive metabolizer genotype appeared to be a result of these patients having the lowest plasma lansoprazole levels among the 3 genotype groups.

Presence of autoantibody against ATTR Val30Met after sequential liver transplantation.

BACKGROUND: Recently, sequential liver transplantation has been performed with an explanted liver from a patient with familial amyloidotic polyneuropathy (FAP) because of the shortage of donors. However, metabolism of amyloidogenic transthyretin (ATTR), the pathogenic protein of FAP, has not been well studied in patients who have undergone sequential liver transplantation. The purpose of this study was to examine the changes in serum ATTR levels and to investigate the presence of an autoantibody in patients who underwent sequential liver transplantation with an explanted organ from a patient with heterozygotic FAP (FAP ATTR Val30Met). METHODS: This was a case study performed at the Kumamoto University School of Medicine, Kumamoto, Japan, and Kyoto University School of Medicine, Kyoto, Japan. Intervention occurred by sequential liver transplantation with an explanted FAP patient's liver. Levels of normal TTR and ATTR in the two patients who received the transplanted liver were analyzed by means of an enzyme-linked immunosorbent assay (ELISA) and a matrix-assisted laser desorption/time-of-flight mass spectrometry. In addition, the presence of an autoantibody against ATTR Val30Met was evaluated via ELISA using purified ATTR Val30Met from homozygotic FAP patients' sera. RESULTS: After the operation, the variant TTR levels were unexpectedly lower than levels of normal TTR in serum samples from patients with a transplanted liver from the FAP patient. An autoantibody against the variant TTR was detected on day 3 after the operation in the serum of those patients and continued to be present for at least 2 months after the operation. CONCLUSIONS: An autoantibody against the variant TTR may reduce the serum levels of variant TTR. Although the antibody may play a beneficial role in reducing the pathogenic protein, the long-term effect of the antibody must be investigated further.

Pharmacogenomics of proton pump inhibitors.

Proton pump inhibitors (PPIs), such as omeprazole, lansoprazole, rabeprazole, esomeprazole, and pantoprazole, are metabolized by cytochrome P450 isoenzyme 2C19 (CYP2C19) in the liver. There are genetic differences that affect the activity of this enzyme. The genotypes of CYP2C19 are classified into three groups: homozygous extensive metabolizer (homEM), heterozygous extensive metabolizer (hetEM), and poor metabolizer (PM). The pharmacokinetics and pharmacodynamics of PPIs differ among the different CYP2C19 genotype groups. Plasma PPI and intragastric pH levels during PPI treatment are the lowest in the homEM group and the highest in the PM group. These CYP2C19 genotype-dependent differences in pharmacokinetics and pharmacodynamics of PPIs are reflected in the cure rates for gastroesophageal reflux disease and Helicobacter pylori infection with PPI-based therapies. The CYP2C19 genotyping test is a useful tool for deciding on the optimal treatment regimen using a PPI, including a dual (PPI plus antibiotic) or a triple (PPI plus two antibiotics) therapy.

Presence of variant transthyretin in aqueous humor of a patient with familial amyloidotic polyneuropathy after liver transplantation.

To determine the origin of transthyretin (TTR) in the aqueous humor of patients with familial amyloidotic polyneuropathy (FAP), we measured TTR levels and analyzed the TTR forms in the aqueous humor of three FAP patients (one patient; liver transplanted, and two patients; non-transplanted). The total TTR levels were almost the same as reported previously in non-transplanted patients and slightly increased in a transplanted patient. Analyses with mass spectrometry in the two non-transplanted FAP ATTR V30M patients revealed that both wild type and variant TTR forms were detected in their aqueous humor samples. Moreover, variant TTR forms could be detected in the aqueous humor of the transplanted patient while the liver produced no variant TTR. These results suggest that variant TTR in aqueous humor may be derived from retina where TTR was produced. In conclusion, TTR metabolism may occur in its own ocular cycle and variant TTR produced by the retina may play an important role in amyloid formation in the ocular tissues of FAP patients.