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Biomedical subjects

Hiroshi Takane

Publications and source records attributed to Hiroshi Takane.

At least 19 recordsLinked to original sources
PubMed2006

Human organic cation transporter (OCT1 and OCT2) gene polymorphisms and therapeutic effects of metformin.

Organic cation transporters (OCTs) are responsible for the hepatic and renal transport of metformin. In this study we analyzed variants of OCT1 and OCT2 genes in 33 patients (24 responders and nine non-responders) based on the hypothesis that polymorphisms in both genes contribute to large inter-patient variability in the clinical efficacy of metformin. The sequences of the 5'-flanking and coding regions of the two genes of interest were screened by single-strand conformation polymorphism (SSCP) analysis. To compare the causative factors between responders and non-responders, we performed stepwise discriminant functional analysis. Age, body mass index (BMI) and treatment with lipid-lowering agents were demonstrated as positive predictors, and two mutations in the OCT1 gene, -43T > G in intron 1 and 408Met > Val (1222A > G) in exon 7, were negative and positive predictors, respectively, for the efficacy of metformin; the predictive accuracy was 55.5% (P < 0.05). Subsequent study indicated that OCT1 mRNA levels tended to be lower in human livers with the 408Met (1222A) variant, though the differences did not reach the level of significance. In this study it is suggested that OCT1 and OCT2 gene polymorphisms have little contribution to the clinical efficacy of metformin.

Adult↗
PubMed2006

Pharmacogenetic determinants of variability in lipid-lowering response to pravastatin therapy.

Pravastatin is mainly taken up from the circulation into the liver via organic anion-transporting polypeptide 1B1 (SLCO1B1 gene product). We examined the contribution of genetic variants in the SLCO1B1 gene and other candidate genes to the variability of pravastatin efficacy in 33 hypercholesterolemic patients. In the initial phase of pravastatin treatment (8 weeks), heterozygous carriers of the SLCO1B1*15 allele had poor low-density lipoprotein cholesterol (LDL-C) reduction relative to non-carriers (percent reduction: -14.1 vs -28.9%); however, the genotype-dependent difference in the cholesterol-lowering effect disappeared after 1 year of treatment. Cholesterol 7alpha-hydroxylase (CYP7A1) and apolipoprotein E (APOE) are known to contribute to lipid metabolism. Homozygous carriers of the CYP7A1 -204C allele or heterozygotes for both CYP7A1 -204C and APOE epsilon4 alleles showed significantly poorer LDL-C reduction compared to that in other genotypic groups after 1 year of treatment (-24.3 vs -33.1%). These results suggest that the SLCO1B1*15 allele is associated with a slow response to pravastatin therapy, and the combined genotyping of CYP7A1 and APOE genes is a useful index of the lipid-lowering effect of pravastatin.

Adult↗
PubMed2006

Glucocorticoid regulation of 24-hour oscillation in interferon receptor gene expression in mouse liver.

Although the antiviral effect of interferon (IFN) varies depending on 24-h oscillation in the expression of its specific receptor, the mechanism of oscillation remains to be clarified. Here we report that oscillation in the expression of the IFN receptor gene (IFN-alpha/beta R1) in mouse liver is caused by the endogenous rhythm of glucocorticoid secretion. Brief exposure of mouse hepatic cells (Hepa 1-6) to corticosterone (CORT) resulted in a significant decrease in mRNA levels of IFN-alpha/beta R1. The CORT-induced decrease in IFN-alpha/beta R1 mRNA levels was reversed by pretreating the cells with RU486, a glucocorticoid receptor antagonist. The mRNA levels of IFN-alpha/beta R1 gene in the liver of adrenalectomized mice were consistently increased throughout the day. However, a single administration of CORT to adrenalectomized mice significantly decreased the mRNA levels of IFN-alpha/beta R1 in the liver. Furthermore, the rhythmic phase of IFN-alpha/beta R1 expression was modulated after the alteration of rhythmicity in glucocorticoid secretion, which was induced by restricted daily feeding. As a consequence, under manipulation of the feeding schedule, 2'-5' oligoadenylate synthase activities, as an index of antiviral effect, in plasma and liver at 24 h after IFN-alpha injection also varied depending on the alteration of glucocorticoid secretion rhythm. These results suggest that the endogenous rhythm of glucocorticoid secretion is involved in the circadian regulation of IFN-alpha/beta R1 expression in mouse liver. Our findings also support the notion that monitoring the 24-h variation in IFN receptor function is useful for selecting the most appropriate time of day to administer IFN.

2',5'-Oligoadenylate Synthetase↗
PubMed2006

Genetic polymorphisms of drug transporters: pharmacokinetic and pharmacodynamic consequences in pharmacotherapy.

There has been increasing appreciation of the role of drug transporters in pharmacokinetic and pharmacodynamic consequences in pharmacotherapy. The clinical relevance of drug transporters depends on the localisation in human tissues (i.e., vectorial movement), the therapeutic index of the substrates and inherent interindividual variability. With regard to variability, polymorphisms of drug transporter genes have recently been reported to be associated with alterations in the pharmacokinetics and pharmacodynamics of clinically useful drugs. A growing number of preclinical and clinical studies have demonstrated that the application of genetic information may be useful in individualised pharmacotherapy for numerous diseases. However, the reported effects of variants in certain drug transporter genes have been inconsistent and, in some cases, conflicting among studies. Furthermore, the incidence of almost all known variants in transporter genes tends to be racially dependent. These observations suggest the necessity of considering interethnic variability before extrapolating pharmacokinetic data obtained in one ethic group to another, especially in the early phase of drug development. This review focuses on the impact of genetic variations in the function of drug transporters (ABC, organic anion and cation transporters) and the implications of these variations for pharmacotherapy from pharmacokinetic and pharmacodynamic viewpoints.

ATP-Binding Cassette Transporters↗
PubMed2006

Long-term follow-up of patients treated with a combination of continuous ambulatory peritoneal dialysis and hemodialysis.

Continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) both have advantages in the treatment of patients with renal failure. In CAPD, solute removal is sometimes insufficient in patients who have a relatively large muscle mass that produces high levels of creatinine. To compensate for this deficiency, frequent exchanges and large dialysate volumes are required. We previously reported that once-weekly HD helps CAPD patients who experience insufficient solute removal. In the present study, we followed, for more than 3 years, 9 CAPD patients who underwent additional weekly HD. Add-on HD therapy significantly increased the subjects' weekly peritoneal creatinine clearance to 45 +/- 3 L (mean +/- standard deviation); these values rose to more than 60 L over the course of the study. Our findings suggest that the combined use of CAPD and HD improves solute clearance in CAPD patients who are insufficiently dialyzed.

Creatinine↗
PubMed2006

Continuous ambulatory peritoneal dialysis is effective for patients with severe congestive heart failure.

Although the use of continuous ambulatory peritoneal dialysis (CAPD) to treat refractory heart failure is not new, in combination with current medical treatment it improves patients'symptoms as well as their cardiac function. We started 16 patients (13 men with a mean age of 66.3 +/- 2.8 years, and 3 women with a mean age of 72 +/- 4.2 years) on CAPD. All patients were symptomatic with congestive heart failure. Mean left ventricular ejection fraction (LVEF) before the start of CAPD was 31% +/- 3%. Introduction to CAPD was associated with a significant improvement in LVEF (to 44% +/- 6%, p < 0.05) and in blood pressure control at 1 year. Also at 1 year, 87% of patients were classified as New York Heart Association grade I or II (maximum possible grade is grade III). These results suggest that CAPD is a treatment of choice for patients suffering from a combination of congestive heart failure and chronic renal insufficiency.

Aged↗
PubMed2005

Dexamethasone influences human clock gene expression in bronchial epithelium and peripheral blood mononuclear cells in vitro.

We determined whether human peripheral blood mononuclear cells (PBMCs) could be used to analyze clock genes by studying their mRNA expressions in human bronchial epithelium (BEAS-2B) and PBMCs following stimulation by the glucocorticoid homologue dexamethasone (DEX) in vitro. PBMCs were obtained at 10:00 h from two diurnally active (approximately 07:00 to 23:00 h) healthy volunteers and were evaluated for hPer1 mRNA expression following DEX stimulation in vitro using real time-PCR analysis. DEX stimulation of human BEAS-2B cells and PBMCs in vitro led to a remarkable increase of hPer1 mRNA. The glucocorticoid rapidly affected the expression of hPer1 mRNA in PBMCs, suggesting that human PBMCs may be a useful surrogate marker for the investigation of drug effects on clock genes.

Adult↗
PubMed2004

Functional assessment of ABCG2 (BCRP) gene polymorphisms to protein expression in human placenta.

The aim of the present study was to assess the contribution of polymorphisms in the breast cancer resistance protein/ATP-binding cassette transporter G2 (BCRP/ABCG2) gene to the placental expression from a new perspective, allelic imbalance. Polymorphisms were screened by polymerase chain reaction (PCR)-single-strand conformation polymorphism analysis followed by sequencing with DNA extracted from 100 placentas. To examine whether polymorphisms of the BCRP gene correlate with the placental BCRP expression, we determined mRNA and protein levels by quantitative real-time PCR and Western blotting, respectively. In placentas, G34A (Val(12)Met) and C421A (Gln(141)Lys) were frequently observed (18-36%), but C376T, which creates a stop codon (Gln(126) stop codon), was found with an allelic frequency of 1%. The mean of the BCRP protein level was significantly lower (p < 0.05) in homozygotes for the A421 allele than in those for the C421 allele, and heterozygotes had an intermediate value. To evaluate whether the C421A polymorphism acts as a cis-element in BCRP transcription, allelic imbalance was determined using informative lymphoblasts and 56 samples of placental cDNA. In most of the placental samples we tested, the difference in expression levels between the two alleles was small, and only two samples indicated a monoallelic expression (i.e., preferential expression of one allele). These results suggest that 1) the predominant allelic expression pattern of BCRP in placental samples is biallelic, and 2) the mutation C421A is not a genetic variant acting in cis, but is considered to influence the translation efficiency.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2004

Allelic expression imbalance of the human CYP3A4 gene and individual phenotypic status.

The human cytochrome P450 3A4 (CYP3A4) plays a dominant role in the metabolism of numerous clinically useful drugs. Alterations in the activity or expression of this enzyme may account for a major part of the variation in drug responsiveness and toxicity. However, it is generally accepted that most of the known single nucleotide polymorphisms in the coding and 5'-flanking regions are not the main determinants for the large inter-individual variability of CYP3A4 expression and activity. We show that the allelic variation is critically involved in determining the individual total hepatic CYP3A4 mRNA level and metabolic capability. There exists a definite correlation between the total CYP3A4 mRNA level and allelic expression ratio, the relative transcript level ratio derived from the two alleles. Individuals with a low expression ratio, exhibiting a large difference of transcript level between the two alleles, revealed extremely low levels of total hepatic CYP3A4 mRNA, and thus low metabolic capability as assessed by testosterone 6beta-hydroxylation. These results present a new insight into the individualized CYP3A4-dependent pharmacotherapy and the importance of expression imbalance to human phenotypic diversity.

Alleles↗
PubMed2004

Haplotype-oriented genetic analysis and functional assessment of promoter variants in the MDR1 (ABCB1) gene.

Recently, a number of nucleotide variants have been described in the multidrug resistance 1 (MDR1/ABCB1) gene; however, most studies have focused on the coding region. In the present study, we identified promoter variants of the MDR1 gene and evaluated their phenotypic consequences using a reporter gene assay and the real-time polymerase chain reaction method. Ten allelic variants were detected in the promoter region (approximately 2 kilobases), seven of which were newly identified. Certain mutations occurred simultaneously, and a total of 10 haplotypes were observed. These promoter polymorphisms were found more frequently in Japanese than Caucasians. Some haplotypes were associated with changes in luciferase activity and placental and hepatic mRNA levels. We also determined DNA methylation status in the proximal promoter region of the MDR1 gene. The promoter region around potential binding sites for transcription factors was found to be hypomethylated and thus likely to be independent of the gene expression. Nucleotide and/or haplotype variants not only in the coding region but also in the promoter region of the MDR1 gene may be important for interindividual differences of P-glycoprotein expression.

Adult↗
PubMed2004

Influence of common variants in the pharmacokinetic genes (OATP-C, UGT1A1, and MRP2) on serum bilirubin levels in healthy subjects.

To assess the contribution of OATP-C to the hepatobiliary transport of bilirubin, a pharmacogenomic evaluation with regard to polymorphisms of three candidate genes, OATP-C, MRP2, and UGT1A1, was performed. Serum total and direct (conjugated) bilirubin levels were used as phenotypic indexes. Pharmacokinetic variables of pravastatin, a typical substrate for OATP-C, were obtained from our previous study. Among 23 volunteers, two variants (Val417Ile and Ser789Phe) were observed in the MRP2 gene. While there was no apparent effect of these two variants and the UGT1A1*28 on direct bilirubin levels, the OATP-C variants were associated with differences in unconjugated bilirubin levels. Subjects with the OATP-C*15 allele had higher bilirubin levels; unconjugated bilirubin levels in *1b/*1b (n = 3), *1b/*15 (n= 7), and *15/*15 (n = 1) subjects were 0.40 +/- 0.10, 0.77 +/- 0.35, and 0.70 (mg/dL), respectively. In addition, the correlation between unconjugated bilirubin levels and pharmacokinetic parameters of pravastatin revealed that the subjects with higher bilirubin levels had lower non-renal clearance values, and then higher serum concentrations of pravastatin. Large clinical studies are needed to confirm a role of OATP-C in the carrier-mediated uptake of bilirubin in the human liver.

Journal Article↗
PubMed2004

Angiotensin receptor antagonist regresses left ventricular hypertrophy associated with diabetic nephropathy in dialysis patients.

BACKGROUND: Left ventricular hypertrophy (LVH) is frequently found at the initiation of dialysis therapy for diabetic and hypertensive patients, and is highly predictive of future cardiac morbidity and mortality. Angiotensin type 1 receptor (AT1) antagonists may be able to regress LVH by mechanisms independent of their antihypertensive effects in diabetic patients. It is not known whether AT1 antagonists are able to reverse LVH in diabetic patients on dialysis therapy. METHOD: Twenty-four type II diabetic patients with end-stage renal disease who had just entered into hemodialysis therapy, and were diagnosed as having LVH evaluated by echocardiography, were selected from 3 dialysis units staffed by the faculty of Saitama Medical School between 1998 and 2001. The study was carried out for 1 year. All patients were randomly assigned to 2 groups. One group received an AT 1 antagonist, losartan 100 mg daily 30 minutes after the cessation of dialysis therapy on dialysis days, or in the evening when dialysis therapy did not occur. The control group received placebo. LVH was evaluated by echocardiography before the start of administration of drugs, at 4 and 8 months, and again at 12 months after the start of drug therapy. A systolic blood pressure of less than 140 mm Hg was the target blood pressure in both groups. RESULTS: Using repeated measures analysis of variance, applied to those with 4 echocardiograms, there were progressive decreases over time in the left ventricular mass index (LVMi), posterior wall thickness, and intraventricular wall thickness in patients receiving losartan. The biggest changes in mass and the other parameters occurred between baseline and at month 6. Compared with these changes in the patients receiving losartan, left ventricular internal diameters and their derived parameters (e.g., ejection fraction) remained unchanged throughout the study. In spite of a similar reduction of bp in the patients receiving placebo, no significant changes in echocardiographic parameters were found in these patients. CONCLUSION: An AT 1 antagonist, losartan, is beneficial for the regression of LVH in diabetic patients who started dialysis therapy under adequate blood pressure control.

Aged↗
PubMed2004

Comparison of the effects of angiotensin receptor antagonist, angiotensin converting enzyme inhibitor, and their combination on regression of left ventricular hypertrophy of diabetes type 2 patients on recent onset hemodialysis therapy.

Left ventricular hypertrophy (LVH) is frequently found at the initiation of dialysis therapy of diabetic and hypertensive patients, and is highly predictive of future cardiac morbidity and mortality. In patients with hypertension and LVH, both an angiotensin converting enzyme (ACE) inhibitor and an angiotensin type 1 receptor (AT1) antagonist regress LVH. However, it remains controversial whether dual blockade of the renin-angiotensin system will regress LVH in these patients using a combination of ACE inhibitor and AT1 antagonist. Thirty-three type II diabetic patients with end-stage renal disease who had just entered into hemodialysis therapy and were diagnosed as having LVH evaluated by echocardiography were selected from three dialysis units staffed by the faculty of Saitama Medical School, Saitama, Japan between 1999 and 2001. The study was carried out for 1 year. All patients were assigned randomly to three groups with equal number: group I, an ACE inhibitor, enalapril 10 mg daily; group II, an AT1 antagonist, losartan 100 mg daily; group III, combination of enalapril 10 mg and losartan 100 mg daily. All antihypertensive drugs were given 30 min after the cessation of dialysis therapy. LVH was evaluated by echocardiography before the start of administration of drugs, at 6 months and 12 months after the start of drug therapy. Systolic blood pressure levels less than 140 mmHg were the target for the three groups. Using repeated measures analysis of variance, applied to those with four echocardiograms, there were progressive decreases over time in left ventricular mass index, posterior wall thickness and interventricular septum thickness. There were no significant differences in regression of LVH as well as blood pressure control between enalapril and losartan groups; however, dual blockade induced an additional 28% reduction in left ventricular mass index compared with any type of monotherapy. Both ACE inhibitors and AT1 antagonists benefit the regression of LVH in diabetic patients who start dialysis therapy. Moreover, combination therapy with ACE inhibitors and AT1 antagonists would provide more beneficial effects on LVH in these patients than monotherapy.

Angiotensin Receptor Antagonists↗
PubMed2004

The MDR1 (ABCB1) gene polymorphism and its clinical implications.

There has been an increasing appreciation of the role of drug transporters in the pharmacokinetic and pharmacodynamic profiles of certain drugs. Among various drug transporters, P-glycoprotein, the MDR1 gene product, is one of the best studied and characterised. P-glycoprotein is expressed in normal human tissues such as liver, kidney, intestine and the endothelial cells of the blood-brain barrier. Apical (or luminal) expression of P-glycoprotein in these tissues results in reduced drug absorption from the gastrointestinal tract, enhanced drug elimination into bile and urine, and impeded entry of certain drugs into the central nervous system. The clinical relevance of P-glycoprotein depends on the localisation in human tissues (i.e. vectorial or directional movement), the therapeutic index of the substrate drug and the inherent inter- and intra-individual variability. With regard to the variability, polymorphisms of the MDR1 gene have recently been reported to be associated with alterations in disposition kinetics and interaction profiles of clinically useful drugs, including digoxin, fexofenadine, ciclosporin and talinolol. In addition, polymorphism may play a role in patients who do not respond to drug treatment. Moreover, P-glycoprotein is an important prognostic factor in malignant diseases, such as tumours of the gastrointestinal tract.A growing number of preclinical and clinical studies have demonstrated that polymorphism of the MDR1 gene may be a factor in the overall outcome of pharmacotherapy for numerous diseases. We believe that further understanding the physiology and biochemistry of P-glycoprotein with respect to its genetic variations will be important to establish individualised pharmacotherapy with various clinically used drugs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

An unusual form of crystal-forming chronic interstitial nephritis following long-term exposure to tosufloxacin tosilate.

Fluoroquinolones are known to cause acute renal failure because of interstitial nephritis with or without epithelioid granulomas. We report the first case of slowly progressive renal failure caused by crystal-forming chronic interstitial nephritis with non-Langerhans' cell histiocytosis after long-term exposure to a fluoroquinolone, tosufloxacin tosilate. Lesions consisted of spindle- to cuboidal-shaped histiocytes with minimal collagenous matrix and low-level lymphocyte infiltration replacing normal tubulointerstitial structure of the kidney. Histiocytes were positive for CD68, but negative for S-100, suggesting they were derived from macrophages. There were numerous rhomboid- to needle-shaped crystal deposits in the cytoplasm of histiocytes, which showed bright birefringence under polarized light. No immunoglobulin deposits were seen in the kidney, and no evidence of paraproteinemia/lymphoproliferative diseases was identified in this patient. Despite a negative drug lymphocyte-stimulating test result using tosufloxacin tosilate, withdrawal of the drug and treatment with steroids gradually improved renal function. In this report, we describe the clinical course and histopathologic findings of this patient and discuss the possible pathogenesis.

Acute Kidney Injury↗