Guoping Yang

Effects of CYP3A4 and CYP3A5 polymorphisms on tacrolimus pharmacokinetics in Chinese adult renal transplant recipients: a population pharmacokinetic analysis.

Objective Tacrolimus is used clinically for the long-term treatment of antirejection of transplanted organs in liver and kidney transplant recipients, although dose optimization is poorly managed. The aim of this study was to examine the association between tacrolimus pharmacokinetic variability and CYP3A4 and CYP3A5 genotypes by a population pharmacokinetic analysis based on routine drug monitoring data in adult renal transplant recipients. Materials and methods Trough tacrolimus concentrations were obtained from 161 adult kidney transplant recipients after transplantation. The population pharmacokinetic analysis was carried out using the nonlinear mixed-effect modeling software NONMEM version 7.2. The CYP3A4*1G and CYP3A5*3 genetic polymorphisms from the patients studied were determined by direct sequencing using a validated automated genetic analyzer. Results A one-compartment model with first-order absorption and elimination adequately described the pharmacokinetics of tacrolimus. Covariates including CYP3A5*3 and CYP3A4*1G alleles and hematocrit were retained in the final model. The apparent clearance of tacrolimus was about two-fold higher in kidney transplant patients with higher enzymatic activity of CYP3A5*1 and CYP3A4*1G (with the CYP3A5*1/*1 or *1/*3 and CYP3A4*1/*1G or CYP3A4*1G/*1G) compared with those with lower enzymatic activity (CYP3A5*3/*3 and CYP3A4*1/*1). Conclusion This is the first study to extensively determine the effect of CYP3A4*1G and CYP3A5*3 genetic polymorphisms and hematocrit value on tacrolimus pharmacokinetics in Chinese renal transplant recipients. The findings suggest that CYP3A5*3 and CYP3A4*1G polymorphisms and hematocrit are determinant factors in the apparent clearance of tacrolimus. The initial dose design is mainly based on CYP3A5 and CYP3A4 genotypes as well as hematocrit. This result may also be useful for maintenance tacrolimus dose optimization and may help to avoid fluctuating tacrolimus levels and improve the efficacy and tolerability of tacrolimus in kidney transplant recipients.

Effects of the CYP Oxidoreductase Ala503Val Polymorphism on CYP3A Activity In Vivo: A Randomized, Open-Label, Crossover Study in Healthy Chinese Men

BACKGROUND Cytochrome P450 (CYP) oxidoreductase (POR) is the electron donor for microsomal CYP enzymes. The POR Ala503Val (POR*28 C > T) polymorphism has been reported to influence CYP3A activity in vivo in a white population. The influence of this polymorphism on CYP3A activity in vivo in the Chinese population currently unknown. OBJECTIVE This study was designed to assess the influence of the POR*28 polymorphism on the CYP3A activity in vivo in healthy Chinese men using midazolam (MID) as a probe drug. METHODS The POR*28 polymorphism was genotyped in healthy Chinese men. A randomized, 2-phase, open-label, crossover study was performed to assess in vivo CYP3A activity after both oral and intravenous MID administration, which reflect both intestinal and hepatic CYP3A or only hepatic CYP3A activity, respectively. The plasma concentrations of MID and 1-hydroxy-midazolam (1-OH-MID) were determined by liquid chromatography-tandem mass spectrometry. RESULTS A total of 73 healthy Chinese men were enrolled (CC genotype, 21 subjects; TT genotype, 11; CT genotype, 41), 22 of whom were selected for additional phenotyping of the CYP3A5*3 polymorphism (CC, 7; TT, 8; CT, 7). The mean (range) age, weight, height, and body mass index of the 22 subjects were 23 (20-28) years, 65.0 (57-75) kg, 1.74 (1.63-1.80) m, and 22.01 (19.27-24.46) kg/m(2), respectively. The frequency of the POR*28 T (503V) allele was 43.2%. No significant differences in the demographic characteristics of the subjects were observed between the POR*28 genotype groups. All of the POR*28 CC and TT homozygotes and 2 of the POR*28 CT heterozygotes carried the CYP3A5*3/*3 genotype (CYP3A5 low expressors); 6 CT heterozygotes carried the CYP3A5*1 allele (CYP3A5 expressors). The mean (SD) 1-OH-MID AUC(0-8) was significantly greater in the TT homozygotes compared with the CT heterozygotes after intravenous (86.15 [24.34] vs 53.21 [31.36] ng/mL/h; P = 0.026) but not oral (126.36 [31.60] vs 103.09 [31.00] ng/mL/h; P = 0.159) MID administration. Mean 1-OH-MID C(max) was significantly greater in the TT homozygotes (51.40 [10.72] ng/mL) compared with the CC homozygotes (31.47 [11.54] ng/mL; P = 0.002) and CT heterozygotes (30.12 [9.21] ng/mL; P = 0.001) after intravenous MID administration. After intravenous MID injection, the MID metabolic ratio was significantly greater in the TT homozygotes compared with carriers of the C allele (P = 0.031). Based on these findings, no significantly differences in overall (hepatic plus intestinal) CYP3A in vivo activity were observed between the POR*28 genotypes. CONCLUSION These findings suggest that individuals with the POR*28 C > T polymorphism underwent an increase in 1-hydroxylation of MID after intravenous MID administration, and that the polymorphism was associated with increased hepatic, but not intestinal, CYP3A activity in these healthy Chinese volunteers.

PPAR-γ2 and PTPRD gene polymorphisms influence type 2 diabetes patients' response to pioglitazone in China

Aim:To investigate the influence of peroxisome proliferator-activated receptor γ2 (PPAR-γ2) gene polymorphism rs1801282 and protein tyrosine phosphatase receptor type D (PTPRD) gene polymorphism rs17584499 on the occurrence of type 2 diabetes and pioglitazone efficacy in a Chinese Han population.Methods:One hundred ninety seven type 2 diabetes patients and 212 healthy controls were enrolled. Among them, 67 type 2 diabetes patients were administered pioglitazone (30 mg/d, po) for 3 months. All the subjects were genotyped for genetic variants in PPAR-γ2 and PTPRD using MALDI-TOF mass spectrometry. Fasting plasma glucose, postprandial plasma glucose, glycated hemoglobin, serum triglyceride, total cholesterol, low-density and high-density lipoprotein-cholesterol were determined.Results:The PPAR-γ2 gene rs1801282 polymorphism was significantly associated with type 2 diabetes susceptibility (OR=0.515, 95% CI 0.268–0.990) and the PTPRD gene rs17584499 polymorphism was also significantly associated with type 2 diabetes (OR=1.984, 95% CI 1.135–3.469) in a dominant model adjusted for age, gender and BMI. After pioglitazone treatment for 3 months, the type 2 diabetes patients with PPAR-γ2 rs1801282 CG genotypes significantly showed higher differential values of postprandial plasma glucose and serum triglyceride compared with those with rs1801282 CC genotype. The patients with PTPRD rs17584499 CT+TT genotypes showed significantly lower differential value of postprandial plasma glucose compared to those with rs17584499 CC genotype.Conclusion:Diabetes risk alleles in PPAR-γ2 (rs1801282) and PTPRD (rs17584499) are associated with pioglitazone therapeutic efficacy.

The ALDH2 rs671 polymorphism affects post-stroke epilepsy susceptibility and plasma 4-HNE levels.

Recent studies have demonstrated the protective effect of mitochondrial aldehyde dehydrogenase 2 (ALDH2) in cardiovascular diseases. Increased levels of the potential ALDH2 substrate 4-hydroxynonenal (4-HNE) are involved in myocardial/cerebral ischemia accompanied by a high level of oxidative stress. In this investigation, we first performed a case-control study to explore the potential association of ALDH2 rs671 polymorphism and post-stroke epilepsy (PSE). Then, we performed an in vitro study to determine whether the overexpression of ALDH2 could decrease the level of oxidative stress and the apoptosis ratio induced by 4-HNE. There was a significant difference in the distribution of the allele and genotype frequencies of the rs671 polymorphism between PSE patients and ischemic stroke (IS) patients. Individuals with the rs671 A allele showed significantly higher levels of plasma 4-HNE. The overexpression of ALDH2 partially blocked the increased levels of malondialdehyde (MDA), reactive oxygen species (ROS) and apoptosis ratio induced by 4-HNE and also partially restored the ALDH2 activity in PC12 cells; these effects were reversed in the presence of εV1-2. Our results suggest that the ALDH2 rs671 polymorphism is associated with PSE susceptibility and affects the 4-HNE levels. Targeting ALDH2 might be a useful strategy for the treatment or prevention of PSE.

Development and validation of an LC-MS/MS method for the determination of tolvaptan in human plasma and its application to a pharmacokinetic study.

Tolvaptan is a selective vasopressin V(2)-receptor antagonist mainly used for the treatment of hyponatremia. This study described the development and validation of an LC-MS/MS method for the determination of tolvaptan in human plasma. Sample preparation involved protein precipitation with acetonitrile containing 2-demethyl tolvaptan (internal standard, IS). Chromatographic separation was performed on a Zorbax XDB C(18) column with an isocratic mobile phase consisting of water (containing 0.1% formic acid) and methanol (25:75, v/v). Determination of the analytes was achieved by tandem-mass spectrometry with positive electrospray ionization. The multiple reaction monitoring (MRM) transitions were performed at m/z 449.2→252.1 for tolvaptan and m/z 435.2→238.1 for IS. The assay was linear over the concentration range of 0.457-1000ng/mL, with a lower limit of quantification of 0.457ng/mL. The intra- and inter-day precisions at three concentration levels (0.914, 111 and 800ng/mL) were less than 15% and their accuracies were within the range of 97.7-107.8%. The mean recovery ranged from 99.2 to 104.6% and the matrix effect from 89.3 to 99.5%. Tolvaptan was stable under all tested conditions. This validated method was successfully applied to a pharmacokinetic study in healthy volunteers after oral administration of single-dose tolvaptan tablets.

Role of sphingosine-1-phosphate receptor 1 and sphingosine-1-phosphate receptor 2 in hyperglycemia-induced endothelial cell dysfunction

The hyperglycemia-induced production of oxidative stress results in endothelial cell dysfunction. Previous studies have demonstrated that sphingosine-1-phosphate (S1P) regulates an array of biological activities in endothelial cells mediated by sphingosine-1-phosphate receptors (S1PRs). However, the role of S1PR-mediated signaling pathways in hyperglycemia-induced endothelial cell dysfunction is currently unknown. In the present study, we aimed to explore the role of S1PRs in endothelial cell dysfunction. For this purpose, hyperglycemia-induced oxidative stress was examined using human umbilical vein endothelial cells (HUVECs) cultured with either normal (5.6 mM) or high (25 mM) levels of glucose. The levels of reactive oxygen species (ROS) and nitric oxide (NO) were determined by flow cytometric (FCM) analysis and nitrate reductase, respectively. Endothelial morphogenesis assay was performed in three-dimensional Matrigel. The mRNA and protein expression levels of S1PRs in the HUVECs were determined by RT-qPCR and western blot analysis, respectively. In addition, ROS, NO and endothelial morphogenesis assays were conducted using the high glucose-treated endothelial cells transfected with adenoviral vector expressing exogenous S1PR1 gene (pAd-S1PR1) or with adenoviral vector expressing S1PR2-specific shRNA (pAd-shRNA-S1PR2). The expression levels of S1PR1 and S1PR2 in the endothelial cells treated with high levels of glucose decreased and increased, respectively. However, the effects of high levels of glucose on S1PR3 were minimal. In addition, high levels of glucose enhanced ROS generation and markedly reduced NO generation and morphogenetic responses. Nevertheless, all the aforementioned changes were completely reversed by transfection with pAd-S1PR1 or pAd-shRNA-S1PR2, which increased S1PR1 and decreased S1PR2 expression, respectively. It can thus be concluded that S1PR1 and S1PR2 play crucial roles in hyperglycemia-induced endothelial cell dysfunction.

Liu Wei Di Huang Wan, a well-known traditional Chinese medicine, induces CYP1A2 while suppressing CYP2A6 and N-acetyltransferase 2 activities in man.

ETHNOPHARMACOLOGICAL RELEVANCE Liu wei di huang wan (LDW), a well-known traditional Chinese medicine, is frequently combined with other prescription or non-prescription drugs in China. AIM OF THE STUDY This study was designed to investigate the effects of LDW on the activities of CYP1A2, CYP2A6, N-acetyltransferase 2 (NAT2) and xanthine oxidase (XO) in healthy subjects, using caffeine as a probe drug. MATERIALS AND METHODS Twelve unrelated healthy males were enrolled in a single-blind, randomized, placebo-controlled, two-phase crossover study. Placebo or LDW (12 pills, 0.2 g/pill, twice daily) was given to each participant for 14 continuous days with a wash-out period of 2 weeks. A dose of 100 mg caffeine was given afterwards to test the activities of drug-metabolizing enzymes of interest. RESULTS Compared to placebo, LDW significantly induced the CYP1A2 activity, as determined by an increase in the ratio of (AFMU+1U+1X)/17U and the formation of 17X and 1X after taking caffeine. Interestingly, LDW significantly decreased the ratio of 17U/(17U+17X+1X+1U+AFMU) and the formation of 17U (CYP2A6-mediated) (by 39.2%; 95%CI: 23.1-55.3%; P=0.026), and decreased the ratio of AFMU/(AFMU+1U+1X) and the formation of AFMU (NAT2-catalyzed) (by 26.2%; 95%CI: 9.2-61.6%; P=0.038), suggesting a marked inhibition of CYP2A6 and NAT2, respectively. CONCLUSIONS LDW can induce CYP1A2 and suppress CYP2A6 and NAT2 activities, and affect caffeine metabolism in vivo.

Assessment of a pharmacokinetic and pharmacodynamic interaction between simvastatin and Ginkgo biloba extracts in healthy subjects

Abstract 1. Ginkgo biloba extract (GBE) is one of the most commonly used herbal remedies worldwide. It is usually concomitantly administrated with statins to treat diseases in geriatric patients. We aim to determine the influence of GBE on the pharmacokinetics (PK) and pharmacodynamics of simvastatin, which is currently unknown. 2. An open-label, randomized, two-period, two-treatment, balanced, crossover study was performed in 14 healthy volunteers. Subjects received simvastatin 40 mg once daily, co-treated with placebo or GBE 120 mg twice daily. Each treatment was administered for 14 d, separated by a wash-out period of 1 month. Simvastatin, simvastatin acid and lipoprotein concentrations were assessed. 3. GBE administration reduced mean simvastatin area under the curve (AUC)0–24, AUC0–∞ and Cmax by 39% (p = 0.000), 36%(p = 0.001) and 32% (p = 0.002), respectively, but did not cause significant differences in simvastatin acid PK or its cholesterol-lowering efficacy. 4. GBE consumption decreased simvastatin system exposure, but did not affect simvastatin acid PK. However, we cannot rule out the possibility for a pharmacodynamic interaction between GBE and simvastatin in vivo.

Effect of a traditional Chinese medicine Liu Wei Di Huang Wan on the activities of CYP2C19, CYP2D6 and CYP3A4 in healthy volunteers

Liu Wei Di Huang Wan (LDW), a well-known traditional Chinese medicine, is widely used for the treatment of various diseases in China. This study was designed to investigate the potential herb–drug interactions of LDW in healthy volunteers and attempted to ascertain whether the interaction might be affected by genotypes. We assessed the effect of LDW on the activities of CYP2C19, CYP2D6 and CYP3A4 in 12 Chinese healthy subjects in a single-center, controlled, non-blinded, two-way crossover clinical trial. The subject pool consisted of six extensive metabolizers with CYP2C19*1/*1 and six poor metabolizers with CYP2C19*2/*2. Placebo or 4.8 g LDW (12 pills, 0.2 g/pill, twice daily) was given to each participant for 14 continuous days with a wash-out period of 2 weeks after an oral administration of 30 mg omeprazole, 30 mg dextromethorphan hydrobromide and 7.5 mg midazolam. The activities of CYP2C19, CYP2D6 and CYP3A4 were ascertained by their respective plasma or urinary metabolic ratios on day 14 post-treatment. There is no difference in the activities of the three tested enzymes before or after a 14-day administration of LDW. LDW had no effect on the pharmacokinetic parameters of the substrates and their metabolites. A 14-day administration of LDW did not affect the activities of CYP2C19, CYP2D6 and CYP3A4. LDW is unlikely to cause pharmacokinetic interaction when it is combined with other medications predominantly metabolized by these enzymes.

Comparing Antihypertensive Effect and Plasma Ciclosporin Concentration between Amlodipine and Valsartan Regimens in Hypertensive Renal Transplant Patients Receiving Ciclosporin Therapy

BackgroundHypertension, a major complication in kidney transplant recipients, is associated with premature death and graft loss. However, an optimal antihypertensive therapy for these patients has not been established [Chinese Clinical Trial Registry No. ChiCTR-TRC-10001071].ObjectiveThe aim of the present study was to evaluate the effect of amlodipine and valsartan on BP control in renal transplant patients and to analyze the correlation between cytochrome P450 (CYP) 3A5 or multidrug resistance-1 gene (MDR1) genotype and the antihypertensive effect of these two regimens.Methods150 renal transplant patients with stage 1 or 2 hypertension were enrolled in the trial. Patients were randomly assigned to amlodipine or valsartan. Metoprolol was added if BP was not under control after 4 weeks. BP and plasma levels of ciclosporin were monitored during the 24-week trial. CYP3A5 and MDR1 genotypes were determined using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.ResultsThe demographic features and baseline BP were similar between these two groups. During the 24-week trial, the reduction of systolic BP (SBP) was similar between the amlodipine and valsartan groups. However, the reduction of diastolic BP (DBP) was significantly greater in the amlodipine group compared with the valsartan group at 12, 16, and 24 weeks of treatment. The plasma level of ciclosporin at 2 hours of medication was significantly higher in the amlodipine group than in the valsartan group after 4 weeks of the trial. The reduction of DBP at 24 weeks was greater in the subjects with CYP3A5 *3/*3 variant than in those with CYP3A5*1/*1 variant (−13.5± 1.9mmHg vs −8.7± 1.6mmHg, p<0.05).ConclusionThe present study demonstrated that amlodipine produced a greater reduction of DBP than valsartan, although both amlodipine and valsartan resulted in satisfactory control of BP in patients with renal transplantation. Administration of amlodipine significantly increased the plasma concentration of ciclosporin, and its effects on BP control and ciclosporin concentration may be associated with the CYP3A5 genotype in these subjects [Chinese Clinical Trial Registry No. ChiCTR-TRC-10001071].