Cytochrome P450 2B6 516G→T is associated with plasma concentrations of nevirapine at both 200 mg twice daily and 400 mg once daily in an ethnically diverse population

Objectives

The aim of the study was to characterize the impact of the cytochrome P450 2B6 (CYP2B6), CYP3A4, CYP3A5 and ATP‐binding cassette sub‐family B member 1 (ABCB1) polymorphisms on nevirapine plasma concentrations.

Methods

A total of 104 patients (82% male; 26% non‐Caucasian) were genotyped for eight single nucleotide polymorphisms at four loci (CYP2B6, CYP3A4, CYP3A5 and MDR1). Nevirapine plasma concentrations were determined using high‐performance liquid chromatography.

Results

Non‐Caucasian ethnicity [5609 ng/mL (n=27) for non‐Caucasians vs. 3771 ng/mL (n=77) for Caucasians; P<0.0001] and CYP2B6 516G→T [GG, 3574 ng/mL (n=50); GT, 4634 ng/mL (n=50); TT, 8170 ng/mL (n=4); P_{analysis of variance (anova)} =0.001] were significantly associated with a higher nevirapine trough concentration (C_trough). The latter association was maintained with both 200 mg twice daily (bid) and 400 mg once daily (qd) dosing [GG, 3527 ng/mL (n=30); GT, 4525 ng/mL (n=32); TT, 7020 ng/mL (n=2); P_anova =0.05 and GG, 3645 ng/mL (n=20); GT, 4861 ng/mL (n=17); TT, 9508 ng/mL (n=2); P_anova =0.01, respectively]. In a multivariable analysis, CYP2B6 516G→T and non‐Caucasian ethnicity remained significant predictors of nevirapine C_trough but CYP2B6 516G→T homozygosity had the greatest effect (108% higher, 46% higher). No associations were found between nevirapine C_trough and the remaining polymorphisms.

Conclusion

In this population, both non‐Caucasian ethnicity and carriage of the variant allele of CYP2B6 516G→T were significant predictors of nevirapine C_trough. The association between CYP2B6 516G→T and higher plasma nevirapine exposure was maintained at both bid and qd dosing.     

CYP2B6基因多态性与艾滋病患者HAART中依非韦仑血浆浓度的关联研究

目的研究依非韦仑（EFV）的血浆浓度与细胞色素P4502B6（CYP2B6）基因多态性的关系。方法用高效液相色谱仪（HPLC系统）测定深圳市东湖医院艾滋病专科门诊68例患者,服用EFV后8-12小时的EFV血浆浓度,用逆转录-聚合酶链反应检测所有患者的CYP2B6 516位点的G〉T基因频率。结果CYP2B6 516位点的基因型39例是GG型,26例是GT型,3例是TT型。各组EFV的血浆浓度分别是（3.3±1.2）μg/ml、（4.7±2.3）μg/ml、（9.0±0.8）μg/ml,其差异有显著的统计学意义（P〈0.01）。结论GT基因型频率在中国人相当常见,该基因型可出现较高的EFV血浆浓度;TT基因型虽然少见,但EFV血浆浓度异常升高。检测CYP2B6基因多态性可帮助临床个性化EFV用量。     

CYP2B6 genetic variants are associated with nevirapine pharmacokinetics and clinical response in HIV-1-infected children

BACKGROUND: Cytochrome P450 2B6 (CYP2B6)-G516T genotype is associated with altered activity of hepatic CYP2B6 and efavirenz pharmacokinetics, but the relationship between the CYP2B6-G516T genotype and nevirapine (NVP) pharmacokinetics in plasma and cerebrospinal fluid (CSF) is limited. METHODS: In 126 children who received NVP and protease inhibitors from PACTG 366 and 377 cohorts, CYP2B6 and ATP-binding cassette, sub-family B, member 1 (ABCB1) gene polymorphisms were analyzed using real-time PCR. Plasma NVP pharmacokinetics and clinical data were collected and levels of NVP in CSF were evaluated in children with HIV-related neurologic diseases. RESULTS: NVP oral clearance in children with the CYP2B6-516-T/T genotype (homozygous variant, n = 14) was 1.6 l/h per m2, which was significantly decreased compared to 2.3 l/h per m2 in those with the -G/G (wild type, n = 49, P = 0.002) and 2.1 l/h per m2 in those with the -G/T genotype (heterozygous variants, n = 63, P = 0.008). Furthermore, children with the -T/T genotype had a significant increase in CD4+ T-cell percentage (+9.0%) compared with those with the -G/G (+3.2%, P = 0.01) and -G/T genotype (+5.0%, P = 0.04) from baseline to week 12. The same trend continued at week 24. Although ABCB1-C3435T genotypes did not affect plasma NVP pharmacokinetics (P = 0.39), the NVP CSF: plasma ratios were significantly higher in children with the ABCB1-3435-C/T or -T/T genotypes (0.62, n = 9) in comparison with those with the ABCB1-3435-C/C genotype (0.43, n = 5) (P = 0.01). CONCLUSIONS: The CYP2B6-G516T genotype alters NVP pharmacokinetics and the immunologic response to NVP-containing HAART regimens in children. These data suggest that the CYP2B6-G516T is an important genetic variant that alters the pharmacokinetics and response to HAART regimens containing NVP.     

Genetic variability of CYP2B6 polymorphisms in four southern Chinese populations

AIM： To investigate the genotype and allelic frequencies of Cytochrome P450 2B6 polymorphisms in four southern Chinese populations.
METHODS： DNA was obtained from blood samples from Han Chinese from Hong Kong and three minority groups,the Wa, Bulang and Lahu from Yunnan in southern China. Genotyping was performed using real-time PCR and confirmed by direct sequencing.
RESULTS： A total of 507 subjects from southern China were studied. Results showed there is a high prevalence of 516G 〉 T （34.5%） in ethnic Chinese compared to literature reports on other Asian populations and Caucasians. The frequency of the 516TT genotype is higher in the Hah majority （23.1%） than in three other ethnic minority groups （i.e., 7.4%, 9.1% and 15.8%） in southern China.
CONCLUSION： This was the first study to document the spectrum of CYP2B6 allelic variants and genotypes in a southern Chinese population. The 516G 〉 T allele is associated with a defective metabolism of efavirenz （EFV）, which therefore may predispose to drug toxicity.Treatment regimens for human immunodeficiency virus （HIV） and heroin addiction may need to be optimized in different populations because of the marked variability of the key metabolizing enzyme.     

Paradoxically elevated efavirenz concentrations in HIV/tuberculosis-coinfected patients with CYP2B6 516TT genotype on rifampin-containing antituberculous therapy

Some individuals have higher efavirenz plasma concentrations during rifampin-containing tuberculosis (TB) therapy, contrary to the expected induction effect of rifampin. Among HIV-infected patients without (n = 38) and with TB on rifampin-containing therapy (n = 18), we tested the hypothesis that drug-gene interaction may explain the highly variable drug interactions. Two-way analysis of variance revealed a significant interaction between CYP2B6 516G→T polymorphism and rifampin-containing therapy, suggesting that efavirenz dose adjustment may need to be individualized on the basis of the patient's genotype.     

Efavirenz-induced neurological symptoms in rare homozygote CYP2B6 *2/*2 (C64T)

Some of the HIV-1-infected patients who were given highly active anti-retroviral therapy (HAART) including efavirenz (EFV) presented adverse central nervous system (CNS) symptoms such as fatigue and insomnia. The incidence of adverse CNS symptoms is associated with hepatic cytochrome P450 isozymes (CYP2B6) polymorphisms. For example, CYP2B6 *6 (G516T and A785G) and *7 (G516T, A785G and C1459T) prolonged the EFV half-life despite discontinuation of EFV. CYP2B6 *2/*2 (C64T) is extremely rare and there have been no data describing the EFV plasma concentrations in C64T homozygous patients, who developed adverse CNS symptoms. C64T homozygous possibly has some catalytic defects.     

Pharmacogenetics of efavirenz and central nervous system side effects: an Adult AIDS Clinical Trials Group study

OBJECTIVES: Efavirenz is an effective antiretroviral agent, but central nervous system side effects occur commonly, and population (racial) differences in pharmacokinetics and response have been reported. Efavirenz is metabolized by cytochrome P4502B6 (CYP2B6). We investigated whether polymorphisms in CYP2B6, CYP3A4, CYP3A5, and MDR1 were associated with efavirenz central nervous system side effects and pharmacokinetics. DESIGN: Twenty-four week cohort from a randomized study. METHODS: Adult AIDS Clinical Trials Group study A5097s examined relationships between central nervous system side effects and efavirenz plasma concentration-time profiles in HIV-infected subjects. Efavirenz plasma pharmacokinetics were estimated by a population-based method. Central nervous system symptoms were assessed by questionnaires and neuropsychological testing. RESULTS: Study subjects included 89 (57%) European-Americans, 50 (32%) African-Americans, and 15 (10%) Hispanics. The CYP2B6 T/T genotype at position 516 (GlnHis) was more common in African-Americans (20%) than in European-Americans (3%), and was associated with greater efavirenz plasma exposure (P < 0.0001). The median efavirenz [area-under-the-curve] (0-24 h) according to G/G, G/T, and T/T genotype was 44 (n = 78), 60 (n = 60), and 130 (n = 14) mug.h/ml, respectively (P < 0.0001). The CYP2B6 G516T genotype was also associated with central nervous system symptoms at week 1 (P = 0.036). Analysis of DNA from other subjects confirmed population differences in frequency of the G516T variant. No associations were apparent with the other polymorphisms studied. CONCLUSIONS: A CYP2B6 allelic variant that is more common in African-Americans than in Europeans-Americans was associated with significantly greater efavirenz plasma exposure during HIV therapy. Inter-individual differences in metabolism may, in part, explain susceptibility to efavirenz central nervous system side effects.     

Successful efavirenz dose reduction in HIV type 1-infected individuals with cytochrome P450 2B6 *6 and *26.

BACKGROUND: Efavirenz (EFV) is metabolized primarily by cytochrome P450 2B6 (CYP2B6), and high plasma concentrations of the drug are associated with a G-->T polymorphism at position 516 (516G-->T) of CYP2B6 and frequent central nervous system (CNS)-related side effects. Here, we tested the feasibility of genotype-based dose reduction of EFV. METHODS: CYP2B6 genotypes were determined in 456 human immunodeficiency virus type 1 (HIV-1)-infected patients who were receiving EFV treatment or were scheduled to receive EFV-containing treatment. EFV dose was reduced in CYP2B6 516G-->T carriers who had high plasma EFV concentrations while receiving the standard dosage (600 mg). EFV-naive homozygous CYP2B6 516G-->T carriers were treated with low-dose EFV. In both groups, the dose was further reduced when plasma EFV concentration remained high. RESULTS: CYP2B6 516G-->T was identified in the *6 allele (found in 17.9% of our subjects) and a novel allele, *26 (found in 1.3% of our patients). All EFV-treated CYP2B6 *6/*6 and *6/*26 carriers had extremely high plasma EFV concentrations (>6000 ng/mL) while receiving the standard dosage. EFV dose was reduced to 400 mg for 11 patients and to 200 mg for 7 patients with persistently suppressed HIV-1 loads. EFV-containing treatment was initiated at 400 mg in 4 CYP2B6 *6/*6 carriers and one *6/*26 carrier. Two of them still had a high plasma EFV concentration while receiving that dose, and the dose was further reduced to 200 mg, with successful HIV-1 suppression. CNS-related symptoms improved with dose reduction in 10 of the 14 patients, although some had not been aware of the symptoms at initial dosage. CONCLUSIONS: Genotype-based EFV dose reduction is feasible in CYP2B6 *6/*6 and *6/*26 carriers, which can reduce EFV-associated CNS symptoms.     

NOS2 C-1173T、G-954C单核苷酸双重多态性与高血压病的关系

目的研究中国汉族人群诱导型一氧化氮合酶(NOS2)基因启动子区C-1173T、G-954C单核苷酸双重多态性(SNP)及其基因型组合与高血压病的相关性。方法随机选择的高血压病个体192人(男97例,女95例)以及健康汉族个体109例(男61例,女48例)检测血白细胞基因DNA,利用嵌巢式等位基因特异性引物PCR技术检测NOS2C-1173T(C-T)、NOS2G-954CSNP(G-C),并应用聚类分析其基冈多态性特征。结果NOS2C-T与G-CSNP基因型分布:高血压病组CC基因型频率(64.06％)与正常对照组(59.17％)相比无差异(P>0.05),TT基因型频率较正常对照组低(P<0.05,x2=4.804)。在女性高血压病患者T等位基因频率与正常对照组无显著性差异;而在男性高血压病患者T等位基因频率较正常对照组低(P<0.05,x2=5.182)。NOS2C-T与G-C组合基因型分布发现:高血压病组携带TT+GG与TT+GC总频率明显低于正常对照组(P<0.05,x2=4.804),男性高血压病患者尤为明显(P<0.05,x2=4.2876)。结论(1)中国汉族人群NOS2C-1173T多态性与男性患高血压病有相关性;NOS2G-954CSNP多态性与高血压病无关。(2)在高血压病男性病人携带,T-1173T+NOS2G-954G与NOS2T-1173T+NOS2G-954C频率较正常对照组低。     

CYP11B2 -344T/C gene polymorphism and blood pressure in patients with acromegaly

CONTEXT: The pathogenesis of increased blood pressure (BP) in acromegaly is unclear, and the role of IGF-I levels and the renin-angiotensin-aldosterone system (RAAS) in this disease remains controversial. OBJECTIVE AND DESIGN: The aim of this study was to investigate the role of gene polymorphisms of the RAAS and involved in sodium handling on BP in acromegaly. SETTING AND PATIENTS: We conducted a multicentric retrospective study that included 100 consecutive patients with acromegaly referred during the period 2000-2003. INTERVENTION: All patients were genotyped for ACE I/D, AGT M235T, CYP11B2 -344T/C, B2R -58T/C, and alpha-adducin G460W polymorphisms. MAIN OUTCOME MEASURE: We assessed the prevalence of hypertension and BP according to the genotype. RESULTS: Patients with the CYP11B2 -344CC genotype displayed a significant increase in the risk of hypertension compared with patients with CT/TT genotypes (odds ratio = 4.0; 95% confidence interval = 1.4-11.6; P = 0.01). Consistently, a significant proportion of patients with the CYP11B2 -344CC genotypes were under antihypertensive treatment (73.1%) compared with patients with the TT/TC genotypes (38.2%; P = 0.003). Patients with the -344CC genotype displayed a significant increase in systolic BP (10.2 +/- 4.3 mm Hg; P = 0.02) but not a significant increase in diastolic BP (2.6 +/- 2.6 mm Hg; P = 0.32) compared with patients with the CT/TT genotype. CONCLUSIONS: We have shown an association of the -344T/C CYP11B2 gene polymorphism with BP in patients affected by acromegaly. These findings suggest that the RAAS is implicated in the pathogenesis of hypertension in acromegaly.     

Correlation between left ventricular mass and urinary sodium excretion in specific genotypes of CYP11B2

BACKGROUND: Aldosterone has essential roles in regulating intravascular volume and blood pressure, and is suggested to influence cardiac structure. However, the association of polymorphisms in the aldosterone synthase gene (CYP11B2) with hypertension or cardiac hypertrophy remains controversial. OBJECTIVE: To evaluate the distribution of polymorphisms in the CYP11B2 gene and the possible associations between genotypes and blood pressure, urinary excretion of aldosterone or electrolytes and echocardiographic measurements, in a Japanese population. METHODS AND RESULTS: We examined the association of two common diallelic polymorphisms within CYP11B2, one in the promoter -344T/C and the other an intron 2 gene conversion, with blood pressure, 24-h urinary excretion of aldosterone and electrolytes, and echocardiographic measurements, in a Japanese population. We confirmed significant linkage disequilibrium between these polymorphic loci and ethnic differences in frequency of the alleles. The -344C and -344T haplotypes apparently diverged before the intron conversion polymorphism was generated on the latter haplotype. Allele frequencies did not differ between 535 normotensive and 360 hypertensive individuals or between hypertensive individuals with higher and lower concentrations of renin. The only significant correlation was a positive correlation of left ventricular mass with 24-h urinary excretion of sodium, which occurred only in individuals with the -344CC genotype or the intron 2 conversion (-/-) genotype. CONCLUSIONS: The -344CC or intron 2 conversion (-/-) genotype in CYP11B2 may be a risk factor for developing sodium-sensitive cardiac hypertrophy. Ethnic differences in the distribution of CYP11B2 genotypes combined with differences in salt intake might account for inconsistencies between previous reports.     

醛固酮合成酶基因多态性与小动脉顺应性的研究

目的探讨醛固酮合成酶（CYP11B2）基因-344C／T多态性与小动脉顺应性（C2）的关系及其临床意义。方法（1）用CVProfilorDO-2020动脉脉搏分析仪测量大小动脉顺应性,共224例,其中C2异常组123例,对照组101例。（2）用多聚酶链反应-限制性片段长度多态性分析方法检测CYP11B2基因-344C／T多态性。结果（1）C2异常组TT基因型、T等位基因频率均高于对照组,但差异无统计学意义（55．3％比41．6％,P〉0．05,75．6％比66．8％,P〉0．05）。（2）CC型与CT型合并分析,显示C2异常组TT型频率显著高于对照组（30．3％比18．8％,P〈0．05）。（3）协方差分析显示,与CT／CC型比较,TT型者C2显著降低。（4）Logistic回归分析表明,TT型是导致C2减退重要的基因型（P=0．043,OR=1．9395％ CI1．02～3．63）。结论CYP11B2基因-344C／T多态性与小动脉顺应性C2密切相关,TT型是C2减退的敏感基因型。     

A polymorphism regulates CYP4A11 transcriptional activity and is associated with hypertension in a Japanese population

CYP4A11 oxidizes arachidonic acid to 20-hydroxyeicosatetraenoic acid, a metabolite with renovascular and tubular function in humans. A previous study demonstrated a significant association between the CYP4A11 gene polymorphism and hypertension; however, the precise mechanism of the association has not been clarified. To assess the involvement of CYP4A11 in the pathogenesis of hypertension, we sought to identify a functional polymorphism of CYP4A11 and examined its impact on predisposition to hypertension in the Tanno-Sobetsu Study. The -845A/G polymorphism was identified in the promoter region of CYP4A11 by direct sequencing. Luciferase expression driven by the promoter of CYP4A11 containing the wild-type -845GG genotype was 30% lower than expression with the variant -845AA genotype. Gel mobility shift assays with nuclear protein extracts showed specific binding to probes containing the variant -845GG. To assess the effect of CYP4A11 polymorphisms on hypertension, we also carried out a case-control study using 4 single nucleotide polymorphisms (-845A/G, -366C/T, 7119C/T, and 8590T/C) in the Tanno-Sobetsu Study. The odds ratio for hypertension in participants with the AG+GG genotype of -845A/G was 1.42 (P=0.008), and the odds ratio for hypertension of the TT genotype of 7119C/T was 1.37 (P=0.037) after adjusting for confounding factors. The haplotype-based case-control analysis using 4 single nucleotide polymorphisms revealed a significant haplotype (G-C-T-T) that was significantly associated with hypertension, with an odds ratio of 1.44 (P=0.006) after adjusting for confounding factors. We have identified a functional variant (-845A/G) of CYP4A11 that is significantly associated with hypertension and that appears to be a novel candidate for a predisposing factor for hypertension.     

Polymorphism of CYP11B2 determines salt sensitivity in Japanese

Aldosterone plays essential roles in body fluid and electrolyte homeostasis and blood pressure. However, the association between polymorphisms in the CYP11B2 gene and hypertension is controversial. We resequenced CYP11B1 and CYP11B2 and identified 35 polymorphisms in this region. We performed association studies between the plasma aldosterone concentration and 13 polymorphisms in this region in 1443 subjects. The subjects were all obtained from the Suita Cohort Study. Multiple regression analysis indicated that aldosterone levels were determined by renin activity, age, total cholesterol, and hematocrit. Residuals of the aldosterone levels after adjusting for these confounding factors were nominally associated with the T(-344)C (P=0.0026), C(595)T (P=0.0180), -(4837)C (P=0.0310), and G(4936)A (P=0.0498) polymorphisms. Only the T(-344)C polymorphism was significantly associated with the aldosterone level after a correction for multiple testing (Bonferroni). A significant interaction was observed between the T(-344)C polymorphism and renin activity in determining aldosterone levels. Moreover, a significant interaction was observed in 2063 subjects between urinary sodium excretion, which reflects sodium intake, and the T(-344)C polymorphism in determining systolic blood pressure. Only subjects with the TT genotype showed a positive correlation between urinary sodium excretion and systolic blood pressure. In vitro experiments confirmed the functional significance of this T(-344)C polymorphism in terms of angiotensin II reactivity. Thus, the T(-344)C polymorphism in CYP11B2 appears to affect salt sensitivity in Japanese and to have clinical significance.     

Serotonin Receptor 2A (HTR2A) Gene Polymorphisms Are Associated with Blood Pressure, Central Adiposity, and the Metabolic Syndrome

Background: Although the etiology of the metabolic syndrome remains unclear, recent evidence suggests that dysregulation of brain serotonergic activity may partly underlie the covariation of risk factors comprising the syndrome. In addition, prior studies have shown polymorphisms in the serotonin 2A receptor (HTR2A) gene to be associated with two syndrome components, hypertension and central adiposity. We conducted a study to confirm associations of HTR2A polymorphisms with elevated blood pressure and central adiposity and tested for association between these polymorphisms and the metabolic syndrome. Methods: The study sample included 934 unrelated individuals of European ancestry. We tested for association of two HTR2A polymorphisms, one in the promoter: (-1438[G/A]) and one in the first intron (2416 [C/T]), individually and as a diplotype, with elevated blood pressure, central adiposity, elevated fasting glucose, triglycerides, high density lipoprotein (HDL) cholesterol and presence of the metabolic syndrome, as defined by the American Heart Association/National Heart, Lung and Blood Institute (AHA/NHLBI) Scientific Statement Executive Summary. Results: Confirming previous reports, elevated blood pressure (>130/85 mm Hg) was associated with both the -1438 GG and 2416 TT genotypes and the GG/TT diplotype (ORs = 1.39-1.76); high waist circumference was associated with -1438 GG genotype only (OR = 1.57). In addition, both the -1438 GG and 2416 TT genotypes, and the GG/TT diplotype, predicted presence of the metabolic syndrome (ORs = 1.44-1.77). Fasting glucose, triglyceride and HDL cholesterol were not associated with either polymorphism. Conclusions: Elevated blood pressure, central adiposity, and the metabolic syndrome are associated with polymorphisms in HTR2A gene.     

急慢性HBV感染者外周血白细胞IL-6-572位点基因多态性分析

目的探讨成年人群IL-6基因启动子区-597G/A和-572C/G位点多态性与HBV感染的关系。方法采用聚合酶链反应-限制性片断长度多态性法检测179例HBV感染者(包括118例慢性乙型肝炎和61例急性乙型肝炎)和120例健康对照人群外周血IL-6基因启动子区-597G/A和-572C/G位点基因分型。结果本研究在-597位点仅发现GG基因型,未发现GA或AA基因型,而-572位点发现CC、CG和GG基因型;对179例HBV感染者和120例健康对照人群检测发现,IL-6-572 GG基因型频率分别为15.1%和19.1%(P>0.05),而118例慢性乙型肝炎患者GG基因型(18.7%)明显高于61例急性乙型肝炎(8.2%)和健康人(11.7%),差异有统计学意义(P<0.05);在HBV感染患者G等位基因频率(47.9%)显著高于健康对照组(35.2%),但差异无统计学意义(P>0.05),而慢性乙型肝炎患者G等位基因频率(37.7%)明显高于急性乙型肝炎(22.1%)和健康对照组(26.7%),差异有统计学意义(P<0.05);多因素非条件Lo-gistic回归分析显示-572基因多态性与HBV感染后慢性化有关[P=0.038,OR=3.788(1.075～13.333)]。结论IL-6-572C/G基因多态性与HBV感染慢性化有关。