Plasma caffeine metabolite ratio (17X/137X) in vivo associated with G-2964A and C734A polymorphisms of human CYP1A2

Coffee Consumption and CYP1A2 Polymorphism Involvement in Type 2 Diabetes in a Romanian Population

Cytochrome P450 1A2 (CYP1A2) is known to be the main enzyme directly responsible for caffeine metabolism. Rs762551 (NC_000015.10:g.74749576C>A) is a single nucleotide polymorphism of the CYP1A2 gene, and it is known mainly for metabolizing caffeine. A significant worldwide health issue, type 2 diabetes (T2DM), has been reported to be negatively associated with coffee consumption. Yet, some studies have proven that high intakes of coffee can lead to a late onset of T2DM.

OBJECTIVES

This study aims to find any significant correlations among CYP1A2 polymorphism, coffee consumption, and T2DM.

METHODS

A total of 358 people were enrolled in this study-218 diagnosed with T2DM, and 140 representing the control sample. The qPCR technique was performed, analyzing rs762551 (assay C_8881221) on the LightCycler 480 (Roche, Basel, Switzerland) with Gene Scanning software version 1.5.1 (Roche).

RESULTS

Our first observation was that the diabetic patients were likely to consume more coffee than the non-diabetic subjects. People with the AA genotype, or the fast metabolizers, are the least common, yet they are the highest coffee consumers and present the highest glucose and cholesterol levels. Another important finding is the correlation between coffee intake and glucose level, which showed statistically significant differences between the diabetic group (p = 0.0002) and the control group (p = 0.029).

CONCLUSIONS

The main conclusion of this study is that according to genotype, caffeine levels, glucose, and cholesterol are interconnected and proportionally related, regardless of type 2 diabetes.

The influence of the CYP1A2-163 C>A polymorphism on the hemostatic response to exercise following caffeine supplementation

BACKGROUND

Prior work from our group suggests that caffeine increases thrombotic potential after acute exercise. The aim of this study was to determine if hemostatic responses to exercise affected by caffeine are influenced by the CYP1A2-163 C>A polymorphism.

METHODS

Forty-two healthy men performed two trials in which a graded maximal exercise test was completed one hour after consuming either 6 mg/kg of caffeine or placebo. Subjects were categorized as possessing the C allele (N.=21) or being homozygous for the A allele (N.=21).

RESULTS

Factor VIII increased more (265%) during exercise in the caffeinated condition than the placebo condition (178%) (P<0.05). Tissue plasminogen activator (tPA) activity also increased more following caffeine as compared to placebo (increase of 8.70±4.32 IU/mL vs. 6.77±3.79 IU/mL respectively, P<0.05). There was no treatment × genotype or treatment × time × genotype interactions.

CONCLUSIONS

Although caffeine increases factor VIII and tPA responses to maximal exercise, these changes are not influenced by the CYP1A2-163 C>A polymorphism.

The Impact of Coffee and Its Selected Bioactive Compounds on the Development and Progression of Colorectal Cancer In Vivo and In Vitro

Coffee is one of the most popular beverages worldwide. Coffee contains bioactive compounds that affect the human body such as caffeine, caffeic acid, chlorogenic acids, trigonelline, diterpenes, and melanoidins. Some of them have demonstrated potential anticarcinogenic effects in animal models and in human cell cultures, and may play a protective role against colorectal cancer. Colorectal cancer (CRC) is the third leading cause of cancer-related mortality in the USA and other countries. Dietary patterns, as well as the consumption of beverages, may reduce the risk of CRC incidence. In this review, we focus on published epidemiological studies concerning the association of coffee consumption and the risk of development of colorectal cancer, and provide a description of selected biologically active compounds in coffee that have been investigated as potential cancer-combating compounds: Caffeine, caffeic acid (CA), chlorogenic acids (CGAs), and kahweol in relation to colorectal cancer progression in in vitro settings. We review the impact of these substances on proliferation, viability, invasiveness, and metastasis, as well as on susceptibility to chemo- and radiotherapy of colorectal cancer cell lines cultured in vitro.

Validation of biomarkers of food intake-critical assessment of candidate biomarkers

Biomarkers of food intake (BFIs) are a promising tool for limiting misclassification in nutrition research where more subjective dietary assessment instruments are used. They may also be used to assess compliance to dietary guidelines or to a dietary intervention. Biomarkers therefore hold promise for direct and objective measurement of food intake. However, the number of comprehensively validated biomarkers of food intake is limited to just a few. Many new candidate biomarkers emerge from metabolic profiling studies and from advances in food chemistry. Furthermore, candidate food intake biomarkers may also be identified based on extensive literature reviews such as described in the guidelines for Biomarker of Food Intake Reviews (BFIRev). To systematically and critically assess the validity of candidate biomarkers of food intake, it is necessary to outline and streamline an optimal and reproducible validation process. A consensus-based procedure was used to provide and evaluate a set of the most important criteria for systematic validation of BFIs. As a result, a validation procedure was developed including eight criteria, plausibility, dose-response, time-response, robustness, reliability, stability, analytical performance, and inter-laboratory reproducibility. The validation has a dual purpose: (1) to estimate the current level of validation of candidate biomarkers of food intake based on an objective and systematic approach and (2) to pinpoint which additional studies are needed to provide full validation of each candidate biomarker of food intake. This position paper on biomarker of food intake validation outlines the second step of the BFIRev procedure but may also be used as such for validation of new candidate biomarkers identified, e.g., in food metabolomic studies.

Investigation of the major cytochrome P450 1A2 genetic variant in a healthy Tibetan population in China

The cytochrome P450 (CYP) 1A2 gene is involved in the metabolism of several carcinogens and clinically important drugs, generating a high potential for pharmacokinetic interactions. Since no data are available for Tibetan aborigines, the present study aimed to investigate the distribution of variant CYP1A2 alleles in a population living in Tibetan region of China. Genotyping analyses of CYP1A2 were conducted in 96 unrelated, healthy volunteers of Tibetan ancestry using direct sequencing assays. A total of 14 different CYP1A2 polymorphisms, including two novel variants (1690G>A and 2896C>T) in the intron region and a novel non-synonymous one (795G>C, Gln265His) were detected. CYP1A2*1A (6.77%), CYP1A2*1B (58.33%) and CYP1A2*1F (14.58%) were the most frequent defective alleles identified in the sample. The frequencies of the prevalent genotypes CYP1A2*1A/*1B, *1B/*1B, *1B/*1F were 13.54%, 16.67% and 29.17%, respectively. In addition, the novel non-synonymous variant 795G>C (Gln265His) was predicted to be benign by PolyPhen-2 and SIFT tools. The present study provides useful information on the pattern of CYP1A2 polymorphisms in Chinese Tibetan population. The current results may have potential benefits for the development of personalized medicine in the Tibetan population.

A case-control field study on the relationships among type 2 diabetes, sleepiness and habitual caffeine intake

OBJECTIVES

The purpose of this study was to examine the possible links between type 2 diabetes, daytime sleepiness, sleep quality and caffeine consumption.

METHODS

In this case-control field study, comparing type 2 diabetic ( n=134) and non-type 2 diabetic ( n=230) participants, subjects completed detailed and validated questionnaires to assess demographic status, health, daytime sleepiness, sleep quality and timing, diurnal preference, mistimed circadian rhythms and habitual caffeine intake. All participants gave saliva under standardised conditions for CYP1A2 genotyping and quantification of caffeine concentration. Hierarchical linear regression analyses examined whether type 2 diabetes status was associated with caffeine consumption.

RESULTS

Type 2 diabetic participants reported greater daytime sleepiness ( p=0.001), a higher prevalence of sleep apnoea ( p=0.005) and napping ( p=0.008), and greater habitual caffeine intake ( p<0.001), derived from the consumption of an extra cup of coffee each day. This finding was confirmed by higher saliva caffeine concentration at bedtime ( p=0.01). Multiple regression analyses revealed that type 2 diabetes status was associated with higher self-reported caffeine consumption ( p<0.02) and higher salivary caffeine ( p<0.02). Next to male sex, type 2 diabetes status was the strongest predictor of caffeine intake. Subjective sleep and circadian estimates were similar between case and control groups.

CONCLUSIONS

Type 2 diabetic patients may self-medicate with caffeine to alleviate daytime sleepiness. High caffeine intake reflects a lifestyle factor that may be considered when promoting type 2 diabetes management.

Assessment of CYP1A2 enzyme activity in relation to type-2 diabetes and habitual caffeine intake

BACKGROUND

Coffee consumption is a known inducer of cytochrome P450 1A2 (CYP1A2) enzyme activity. We recently observed that a group of type-2 diabetes patients consumed more caffeine (coffee) on a daily basis than non-type-2 diabetes controls. Here, we investigated whether type-2 diabetes cases may metabolize caffeine faster than non-type-2 diabetes controls.

METHODS

To estimate CYP1A2 enzyme activity, an established marker of caffeine metabolism, we quantified the paraxanthine/caffeine concentration ratio in saliva in 57 type-2 diabetes and 146 non-type-2 diabetes participants in a case-control field study. All participants completed validated questionnaires regarding demographic status, health and habitual caffeine intake, and were genotyped for the functional -163C > A polymorphism of the CYP1A2 gene.

RESULTS

In the diabetes group, we found a larger proportion of participants with the highly inducible CYP1A2 genotype. Furthermore, the paraxanthine/caffeine ratio, time-corrected to mitigate the impact of different saliva sampling times with respect to the last caffeine intake, was higher than in the control group. Participants who reported habitually consuming more caffeine than the population average showed higher CYP1A2 activity than participants with lower than average caffeine consumption. Multiple regression analyses revealed that higher caffeine intake was potentially an important mediator of higher CYP1A2 activity.

CONCLUSIONS

Estimated CYP1A2 enzyme activity, and thus speed of caffeine metabolism, was higher in our type-2 diabetes group; this was possibly due to higher intake of caffeine, a known inducer of CYP1A2 enzyme activity. Given the fairly small sample sizes, the results need to be considered as preliminary and require validation in larger populations.

Moving towards Specific Nutrigenetic Recommendation Algorithms: Caffeine, Genetic Variation and Cardiovascular Risk

Recent research has indicated that part of the interindividual variability in cardiovascular responses to caffeine has a genetic basis. Therefore, knowledge of the individual's genetic constitution may allow an individual tailoring of dietary advice for the use of caffeine-containing beverages, yielding an example of the potential of practical translation of nutrigenetic information. This paper reviews the basis for possible nutrigenetic recommendations on the consumption of caffeine, discussing the current gaps in knowledge but also proposing a mode of action in this research area, which may be transposed to other types of similar recommendations.

Caffeine: Friend or Foe?

The debate on the safety of and regulatory approaches for caffeine continues among various stakeholders and regulatory authorities. This decision-making process comes with significant challenges, particularly when considering the complexities of the available scientific data, making the formulation of clear science-based regulatory guidance more difficult. To allow for discussions of a number of key issues, the North American Branch of the International Life Sciences Institute (ILSI) convened a panel of subject matter experts for a caffeine-focused session entitled "Caffeine: Friend or Foe?," which was held during the 2015 ILSI Annual Meeting. The panelists' expertise covered topics ranging from the natural occurrence of caffeine in plants and interindividual metabolism of caffeine in humans to specific behavioral, reproductive, and cardiovascular effects related to caffeine consumption. Each presentation highlighted the potential risks, benefits, and challenges that inform whether caffeine exposure warrants concern. This paper aims to summarize the key topics discussed during the session.

Quercetin significantly inhibits the metabolism of caffeine, a substrate of cytochrome P450 1A2 unrelated to CYP1A2*1C (-2964G>A) and *1F (734C>A) gene polymorphisms

Background. Quercetin is abundant in plants and human diets. Previous studies indicated that quercetin inhibited the activity of CYP1A2, and the combination of quercetin with the substrates of CYP1A2 might produce herb-drug interactions. This research aims to determine the effects of quercetin and the CYP1A2 gene polymorphisms, namely, CYP1A2*1C  (−2964G>A) and *1F (734C>A), on the metabolism of caffeine. Method. The experiment was designed into two treatment phases separated by a 2-week washout period. Six homozygous individuals for the CYP1A2*1C/*1F (GG/AA) genotype and 6 heterozygous individuals for the CYP1A2*1C/*1F (GA/CA) genotype were enrolled in the study. Quercetin capsules (500 mg) were given to each volunteer once daily for 13 consecutive days, and after that, each subject was coadministrated 100 mg caffeine capsules with 500 mg quercetin on the 14th day. Then a series of venous blood samples were collected for HPLC analysis. Correlation was determined between pharmacokinetics of caffeine and paraxanthine with caffeine metabolite ratio. Results. Quercetin significantly affected the pharmacokinetics of caffeine and its main metabolite paraxanthine, while no differences were found in the pharmacokinetics of caffeine and paraxanthine between GG/AA and GA/CA genotype groups. Conclusion. Quercetin significantly inhibits the caffeine metabolism, which is unrelated to CYP1A2*1C (−2964G>A) and *1F (734C>A) gene polymorphisms.

Considering CYP1A2 phenotype and genotype for optimizing the dose of olanzapine in the management of schizophrenia

INTRODUCTION

Schizophrenia, a mental disorder, is a debilitating condition which typically strikes young people in their early 20's. Antipsychotic medications are widely prescribed for the treatment of schizophrenia however a balancing act is necessary to provide the correct dose to each patient. It is suggested that a large number of patients discontinue antipsychotic pharmacotherapy because the treatments provided do not always reduce the positive symptoms of the disease, while many have adverse effects on the patients. This implies that neither the incorrect drug nor the optimal dosage for that patient is achieved.

AREAS COVERED

The current review investigates variability in response to olanzapine with a specific focus on the common intrinsic and extrinsic factors that influence both olanzapine and CYP1A2 activity. Furthermore, the authors discuss the utilization of phenotyping and genotyping of CYP1A2 and their potential utility in clinical practice for olanzapine dosing regimens. The authors also consider the potential of pharmacometrics compared to pharmacogenomics as a tool to personalize medicine.

EXPERT OPINION

Careful consideration must be given to the impact of a genetic variant on the disposition of a drug prior to implementing genetic 'tests' to determine response. CYP1A2 phenotypic assessment can yield important information regarding the disposition of olanzapine; however, it relies on the accuracy of the metric and the minimal impact of other metabolic pathways. The application of pharmacometrics provides an effective method to establish covariates that significantly influence olanzapine disposition which can incorporate phenotype and/or genotype.

Association between common CYP1A2 polymorphisms and theophylline metabolism in non-smoking healthy volunteers

This study was designed to investigate the impact of cytochrome P450 (CYP) 1A2 polymorphisms on theophylline metabolism in a non-smoking healthy male Chinese population. Four polymorphisms CYP1A2 1C (G-3860A), G-3113A, CYP1A2 1F (C-163A) and CYP1A2 1B (C-5347T) were screened in 238 unrelated male volunteers. Then, a single oral 200-mg dose of theophylline was administered to 37 volunteers, who were selected from 238 volunteers based on the CYP1A2 genotype. CYP1A2 activities were evaluated by plasma 1,7-dimethylxanthine/caffeine ratios (17X/137X) after administration of 100-mg caffeine. The plasma concentrations of theophylline, 17X and 137X were determined by high-performance liquid chromatography. The activity of CYP1A2 was lower in volunteers with the -3113 AA genotype compared with those with the -3113 AG genotype (0.35 ± 0.04 versus 0.48 ± 0.07, p = 0.016) or the -3113 GG genotype (0.35 ± 0.04 versus 0.58 ± 0.22, p = 0.037). CYP1A2 1F polymorphisms were associated with increased CYP1A2 activity in volunteers with -3860G/-3113G/5347C homozygosity (0.66 ± 0.24 versus 0.46 ± 0.05, p = 0.034). However, theophylline metabolism showed no difference among volunteers carrying different haplotype pairs. CYP1A2 genetic polymorphisms influenced CYP1A2 enzyme activity as measured by caffeine, but CYP1A2 gene polymorphisms appeared to have limited influence on theophylline metabolism in our study.

Effects of 16-week consumption of caffeinated and decaffeinated instant coffee on glucose metabolism in a randomized controlled trial

Objective. Observational studies have shown a protective association between coffee consumption and type 2 diabetes mellitus whereas caffeine or caffeinated coffee acutely deteriorates glucose tolerance. We investigated the effects of chronic drinking of instant coffee on glucose and insulin concentrations during a 75 g oral glucose tolerance test. Methods. Overweight men with a mild-to-moderate elevation of fasting plasma glucose were randomly allocated to a 16-week intervention of consuming 5 cups of caffeinated (n = 17) or decaffeinated (n = 15) instant coffee per day or no coffee (n = 13). Results. The caffeinated coffee group showed statistically significant decreases in the 2-hour concentrations and the area under the curve of glucose while neither decaffeinated coffee nor coffee group showed such a change. Waist circumstance decreased in the caffeinated coffee group, increased in the decaffeinated coffee group, and did not change in the noncoffee group (P = 0.002). With adjustment for the change in waist circumference, caffeinated and decaffeinated coffee consumption were associated with a modest decrease in the postload glucose levels. Conclusion. Both caffeinated and decaffeinated coffee may be protective against deterioration of glucose tolerance.

Using bioinformatic approaches to identify pathways targeted by human leukemogens

We have applied bioinformatic approaches to identify pathways common to chemical leukemogens and to determine whether leukemogens could be distinguished from non-leukemogenic carcinogens. From all known and probable carcinogens classified by IARC and NTP, we identified 35 carcinogens that were associated with leukemia risk in human studies and 16 non-leukemogenic carcinogens. Using data on gene/protein targets available in the Comparative Toxicogenomics Database (CTD) for 29 of the leukemogens and 11 of the non-leukemogenic carcinogens, we analyzed for enrichment of all 250 human biochemical pathways in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. The top pathways targeted by the leukemogens included metabolism of xenobiotics by cytochrome P450, glutathione metabolism, neurotrophin signaling pathway, apoptosis, MAPK signaling, Toll-like receptor signaling and various cancer pathways. The 29 leukemogens formed 18 distinct clusters comprising 1 to 3 chemicals that did not correlate with known mechanism of action or with structural similarity as determined by 2D Tanimoto coefficients in the PubChem database. Unsupervised clustering and one-class support vector machines, based on the pathway data, were unable to distinguish the 29 leukemogens from 11 non-leukemogenic known and probable IARC carcinogens. However, using two-class random forests to estimate leukemogen and non-leukemogen patterns, we estimated a 76% chance of distinguishing a random leukemogen/non-leukemogen pair from each other.

Caffeine increases tear volume depending on polymorphisms within the adenosine A2a receptor gene and cytochrome P450 1A2

PURPOSE

The primary aim of the present study was to examine the effect of caffeine on tear volume. The secondary aim was to investigate the relation between caffeine-induced changes in tear volume and polymorphisms in ADORA2A and CYP1A2.

DESIGN

Double-masked, placebo-controlled, crossover study.

PARTICIPANTS

Seventy-eight healthy volunteers were recruited for the study.

METHODS

Subjects participated in 2 sessions in which they received capsules containing either placebo or caffeine. The caffeine capsules were given to the subjects to keep the caffeine volume per body weight within 5 to 7 mg/kg. After caffeine intake, tear meniscus height (TMH) was measured. Subjects provided a blood sample for genotyping.

MAIN OUTCOME MEASURES

Tear meniscus height, single nucleotide polymorphism.

RESULTS

The tear volume increased after caffeine consumption. The net increase in TMH was 0.08 mm (95% confidence interval, 0.05-0.10) greater when participants were given caffeine than when given placebo (P<0.0001). In ADORA2A, the difference in the net increase in TMH for participants who were heterozygous at rs5751876 and rs2298383 was 0.07 mm (P = 0.001) and who were minor homozygous was 0.08 mm (P = 0.007). In CYP1A2, the net increase in TMH for participants who were minor homozygous at rs2472304 was lower than for those who were major homozygous; the difference was 0.06 mm (P = 0.039).

CONCLUSIONS

Caffeine intake increases tear volume and polymorphisms within ADORA2A, and CYP1A2 is associated with the tear increase after caffeine intake. Genetic polymorphisms had a significant effect on tear meniscus that was of limited clinical significance.

Coffee, ADORA2A, and CYP1A2: the caffeine connection in Parkinson's disease

BACKGROUND AND PURPOSE

In 1-methyl-4-phenyl 1,2,3,6-tetrahydropyridine animal models of Parkinson's disease (PD), caffeine protects neurons by blocking the adenosine receptor A2A (ADORA2A). Caffeine is primarily metabolized by cytochrome P450 1A2 (CYP1A2). Our objective was to examine whether ADORA2A and CYP1A2 polymorphisms are associated with PD risk or modify the caffeine-PD association.

METHODS

Parkinson's Epidemiology and Genetic Associations Studies in the United States (PEGASUS) included five population-based case-control studies. One laboratory genotyped four ADORA2A and three CYP1A2 polymorphisms in 1325 PD cases and 1735 age- and sex-matched controls. Information regarding caffeine (coffee) consumption and other lifestyle factors came from structured in-person or telephone interviews. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression.

RESULTS

Two ADORA2A polymorphisms were inversely associated with PD risk - rs71651683, a 5' variant (adjusted allelic OR = 0.51, 95% CI 0.33-0.80, permutation-adjusted P = 0.015) and rs5996696, a promoter region variant (adjusted OR for AC and CC genotypes compared with the AA wild-type genotype were 0.76 (95% CI 0.57-1.02) and 0.37 (95% CI 0.13-1.01), respectively (permutation-adjusted P for trend = 0.04). CYP1A2 polymorphisms were not associated with PD risk; however, the coffee-PD association was strongest among subjects homozygous for either variant allele rs762551 (P(interaction) = 0.05) or rs2470890 (P(interaction) = 0.04).

CONCLUSION

In this consortium study, two ADORA2A polymorphisms were inversely associated with PD risk, but there was weak evidence of interaction with coffee consumption. In contrast, the coffee-PD association was strongest among slow metabolizers of caffeine who were homozygous carriers of the CYP1A2 polymorphisms.

Caffeine consumption during pregnancy and risk of preterm birth: a meta-analysis

BACKGROUND

The effect of caffeine intake during pregnancy on the risk of preterm delivery has been studied for the past 3 decades with inconsistent results.

OBJECTIVE

We performed a meta-analysis examining the association between caffeine consumption during pregnancy and risk of preterm birth.

DESIGN

We searched MEDLINE and EMBASE articles published between 1966 and July 2010, cross-referenced reference lists of the retrieved articles, and identified 15 cohort and 7 case-control studies that met inclusion criteria for this meta-analysis.

RESULTS

The combined odds ratios (ORs) obtained by using fixed-effects models for cohort studies were 1.11 (95% CI: 0.96, 1.28), 1.10 (95% CI: 1.01, 1.19), and 1.08 (95% CI: 0.93, 1.27) for risk of preterm birth comparing the highest with the lowest level of caffeine intake (or no intake) (mg/d) during the first, second, and third trimesters, respectively. Results for the case-control studies yielded no associations for the first (OR: 1.07; 95% CI: 0.84, 1.37), second (OR: 1.17; 95% CI: 0.94, 1.45), or third (OR: 0.94; 95% CI: 0.79, 1.12) trimesters. No overall heterogeneity was found by region, publication decade, exposure and outcome assessment, caffeine sources, or adjustment for confounding, which was largely driven by individual studies.

CONCLUSION

In this meta-analysis, we observed no important association between caffeine intake during pregnancy and the risk of preterm birth for cohort and case-control studies.

Caffeine, selected metabolic gene variants, and risk for neural tube defects

BACKGROUND

Investigations of maternal caffeine intake and neural tube defects (NTDs) have not considered genetic influences. Caffeine metabolism gene effects were examined in the National Birth Defects Prevention Study.

METHODS

Average daily caffeine was summed from self-reported coffee, tea, soda, and chocolate intake for mothers of 768 NTD cases, and 4143 controls delivered from 1997 to 2002. A subset of 306 NTD and 669 control infants and their parents were genotyped for CYP1A2*1F, NAT2 481C>T, and NAT2 590G>A. CYP1A2*1F was classified by fast or slow oxidation status, and NAT2 variants were categorized into rapid or slow acetylation status. Case-control logistic regression analyses, family-based transmission/disequilibrium tests and log-linear analyses, and hybrid log-linear analyses were conducted to produce odds ratios (ORs) or relative risks (RRs) and 95% confidence intervals (CIs) for caffeine intake and maternal and infant gene variants, and to examine interaction effects.

RESULTS

NTDs were independently associated with infant slow NAT2 acetylator status (RR, 2.00; 95% CI, 1.10-3.64) and maternal CYP1A2*1F fast oxidation status (OR, 1.49; 95% CI, 1.10-2.03). Mothers who consumed caffeine, oxidized CYP1A2*1F quickly, and acetylized NAT2 slowly had a nonsignificantly elevated estimated risk for an NTD-affected pregnancy (OR, 3.10; 95% CI, 0.86-11.21). Multiplicative interaction effects were observed between maternal caffeine and infant CYP1A2*1F fast oxidizer status (p(interaction) = 0.03).

CONCLUSIONS

The association identified between maternal CYP1A2*1F fast oxidation status and NTDs should be examined further in the context of the other substrates of CYP1A2. Maternal caffeine and its metabolites may be associated with increased risk for NTD-affected pregnancies in genetically susceptible subgroups.

Structure, function, regulation and polymorphism and the clinical significance of human cytochrome P450 1A2

Human CYP1A2 is one of the major CYPs in human liver and metabolizes a number of clinical drugs (e.g., clozapine, tacrine, tizanidine, and theophylline; n > 110), a number of procarcinogens (e.g., benzo[a]pyrene and aromatic amines), and several important endogenous compounds (e.g., steroids). CYP1A2 is subject to reversible and/or irreversible inhibition by a number of drugs, natural substances, and other compounds. The CYP1A gene cluster has been mapped on to chromosome 15q24.1, with close link between CYP1A1 and 1A2 sharing a common 5'-flanking region. The human CYP1A2 gene spans almost 7.8 kb comprising seven exons and six introns and codes a 515-residue protein with a molecular mass of 58,294 Da. The recently resolved CYP1A2 structure has a relatively compact, planar active site cavity that is highly adapted for the size and shape of its substrates. The architecture of the active site of 1A2 is characterized by multiple residues on helices F and I that constitutes two parallel substrate binding platforms on either side of the cavity. A large interindividual variability in the expression and activity of CYP1A2 has been observed, which is largely caused by genetic, epigenetic and environmental factors (e.g., smoking). CYP1A2 is primarily regulated by the aromatic hydrocarbon receptor (AhR) and CYP1A2 is induced through AhR-mediated transactivation following ligand binding and nuclear translocation. Induction or inhibition of CYP1A2 may provide partial explanation for some clinical drug interactions. To date, more than 15 variant alleles and a series of subvariants of the CYP1A2 gene have been identified and some of them have been associated with altered drug clearance and response and disease susceptibility. Further studies are warranted to explore the clinical and toxicological significance of altered CYP1A2 expression and activity caused by genetic, epigenetic, and environmental factors.

Coffee consumption and CYP1A2 genotype in relation to bone mineral density of the proximal femur in elderly men and women: a cohort study

Background

Drinking coffee has been linked to reduced calcium conservation, but it is less clear whether it leads to sustained bone mineral loss and if individual predisposition for caffeine metabolism might be important in this context. Therefore, the relation between consumption of coffee and bone mineral density (BMD) at the proximal femur in men and women was studied, taking into account, for the first time, genotypes for cytochrome P450 1A2 (CYP1A2) associated with metabolism of caffeine.

Methods

Dietary intakes of 359 men and 358 women (aged 72 years), participants of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS), were assessed by a 7-day food diary. Two years later, BMD for total proximal femur, femoral neck and trochanteric regions of the proximal femur were measured by Dual-energy X-ray absorptiometry (DXA). Genotypes of CYP1A2 were determined. Adjusted means of BMD for each category of coffee consumption were calculated.

Results

Men consuming 4 cups of coffee or more per day had 4% lower BMD at the proximal femur (p = 0.04) compared with low or non-consumers of coffee. This difference was not observed in women. In high consumers of coffee, those with rapid metabolism of caffeine (C/C genotype) had lower BMD at the femoral neck (p = 0.01) and at the trochanter (p = 0.03) than slow metabolizers (T/T and C/T genotypes). Calcium intake did not modify the relation between coffee and BMD.

Conclusion

High consumption of coffee seems to contribute to a reduction in BMD of the proximal femur in elderly men, but not in women. BMD was lower in high consumers of coffee with rapid metabolism of caffeine, suggesting that rapid metabolizers of caffeine may constitute a risk group for bone loss induced by coffee.

Genetic polymorphism of metabolic enzymes P450 (CYP) as a susceptibility factor for drug response, toxicity, and cancer risk

The polymorphic P450 (CYP) enzyme superfamily is the most important system involved in the biotransformation of many endogenous and exogenous substances including drugs, toxins, and carcinogens. Genotyping for CYP polymorphisms provides important genetic information that help to understand the effects of xenobiotics on human body. For drug metabolism, the most important polymorphisms are those of the genes coding for CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5, which can result in therapeutic failure or severe adverse reactions. Genes coding for CYP1A1, CYP1A2, CYP1B1, and CYP2E1 are among the most responsible for the biotransformation of chemicals, especially for the metabolic activation of pre-carcinogens. There is evidence of association between gene polymorphism and cancer susceptibility. Pathways of carcinogen metabolism are complex, and are mediated by activities of multiple genes, while single genes have a limited impact on cancer risk. Multigenic approach in addition to environmental determinants in large sample studies is crucial for a reliable evaluation of any moderate gene effect. This article brings a review of current knowledge on the relations between the polymorphisms of some CYPs and drug activity/toxicity and cancer risk.

CYP1A2 genotype modifies the association between coffee intake and the risk of hypertension

OBJECTIVES

The longitudinal relationship between coffee use and hypertension is still controversial. Cytochrome P450 1A2 (CYP1A2) is the main responsible enzyme for the metabolism of caffeine. The aim of the present study was to investigate the effect of coffee intake on the risk of developing hypertension needing antihypertensive treatment in individuals stratified by CYP1A2 genotype.

DESIGN

We assessed prospectively 553 young White individuals screened for stage 1 hypertension. Coffee intake was ascertained from regularly administered questionnaires. Incident physician-diagnosed hypertension was the outcome measure. Genotyping of CYP1A2 SNP was performed by real time PCR.

RESULTS

During a median follow-up of 8.2 years, 323 individuals developed hypertension. For carriers of the slow *1F allele (59%), hazard ratios of hypertension from multivariable Cox analysis were 1.00 in abstainers (reference), 1.72 (95%CI, 1.21-2.44) in moderate coffee drinkers (P = 0.03), and 3.00 (1.53-5.90) in heavy drinkers (P = 0.001). In contrast, hazard ratios for coffee drinkers with the rapid *1A/*1A genotype were 0.80 (0.52-1.23, P = 0.29) for moderate drinkers and 0.36 (0.14-0.89, P = 0.026) for heavy drinkers. In a two-way ANCOVA, a gene x coffee interactive effect was found on follow-up changes in systolic (P = 0.000) and diastolic (P = 0.007) blood pressure. Urinary epinephrine was higher in coffee drinkers than abstainers but only among individuals with slow *1F allele (P = 0.001).

CONCLUSION

These data show that the risk of hypertension associated with coffee intake varies according to CYP1A2 genotype. Carriers of slow *1F allele are at increased risk and should thus abstain from coffee, whereas individuals with *1A/*1A genotype can safely drink coffee.

Insights into the substrate specificity, inhibitors, regulation, and polymorphisms and the clinical impact of human cytochrome P450 1A2

Human CYP1A2 is one of the major CYPs in human liver and metabolizes a variety of clinically important drugs (e.g., clozapine, tacrine, tizanidine, and theophylline), a number of procarcinogens (e.g. benzo[a]pyrene and aflatoxin B(1)), and several important endogenous compounds (e.g. steroids and arachidonic acids). Like many of other CYPs, CYP1A2 is subject to induction and inhibition by a number of compounds, which may provide an explanation for some drug interactions observed in clinical practice. A large interindividual variability in the expression and activity of CYP1A2 and elimination of drugs that are mainly metabolized by CYP1A2 has been observed, which is largely caused by genetic (e.g., SNPs) and epigenetic (e.g., DNA methylation) and environmental factors (e.g., smoking and comedication). CYP1A2 is primarily regulated by the aromatic hydrocarbon receptor (AhR) and CYP1A2 is induced through AhR-mediated transactivation following ligand binding and nuclear translocation. To date, more than 15 variant alleles and a series of subvariants of the CYP1A2 gene have been identified and some of they have been associated with altered drug clearance and response to drug therapy. For example, lack of response to clozapine therapy due to low plasma drug levels has been reported in smokers harboring the -163A/A genotype; there is an association between CYP1A2*1F (-163C>A) allele and the risk for leflunomide-induced host toxicity. The *1F allele is associated with increased enzyme inducibility whereas *1C causes reduced inducibility. Further studies are warranted to explore the clinical and toxicological significance of altered CYP1A2 expression and activity caused by genetic, epigenetic, and environmental factors.

CYP1A2 genotype and rheumatoid arthritis in Koreans

Cytochrome P540 (CYP) 1A2 plays a role in the production of reactive oxygen species (ROS), which have been implicated in the development of rheumatoid arthritis (RA). The objective of this study was to investigate the association between a common polymorphism in the CYP1A2 gene with risk and severity of RA in a Korean population. Cases (n = 1321) with RA and controls (n = 1037) were genotyped for the CYP1A2 -163 A>C polymorphism by real-time PCR. HLA-DRB1 typing and further subtyping of all alleles was performed by PCR, sequence-specific oligonucleotide probe hybridization and direct DNA sequencing analysis. The odds ratio (OR) [(95% confidence interval (CI)] of RA associated with the low inducible C allele was 1.11 (0.80-1.55) among non-shared epitope (SE) carriers, 0.82 (0.56-1.20) among heterozygotes and 0.32 (0.10-1.04) among individuals homozygous for the SE (P = 0.03 for CYP1A2-SE interaction). A protective effect of the low inducibility CYP1A2 C allele among carriers of the SE suggests that a product of CYP1A2-mediated metabolism, such as ROS, may be involved in the development of RA.

Effect of smoking and CYP2D6 polymorphisms on the extent of fluvoxamine-alprazolam interaction in patients with psychosomatic disease

PURPOSE

Fluvoxamine (FVX) is metabolized by cytochrome P450 (CYP) 2D6 and CYP1A2 and inhibits CYP3A4. The aim of this study was to investigate the factors responsible for interindividual variability in the extent of interaction between FVX and alprazolam (ALP).

METHODS

Blood samples were taken from 49 depressive patients to determine plasma concentration of FVX, ALP or both. Twenty-four samples were taken during the FVX-alone period, 21 samples during the ALP-alone period and 30 samples during the FVX-ALP period. Subjects were also genotyped for CYP2D6.

RESULTS

The concentration-to-dose (C/D) ratio of ALP during the FVX-treatment period was significantly higher than that during the ALP-alone period. The CYP2D6 genotype affected neither the C/D ratios of FVX nor the extent of interaction. The mean C/D ratio of FVX in smokers was reduced by more than 30% in comparison with that in non-smokers. The mean C/D ratio of ALP in non-smokers was increased by FVX, while that in smokers was unchanged.

CONCLUSIONS

The extent of interaction between FVX and ALP may be affected by smoking, which alters the C/D ratio of FVX. Therefore, when FVX and ALP are concomitantly administered, it should be noted that non-smokers may exhibit greater drug interaction than smokers.

Coffee intake, variants in genes involved in caffeine metabolism, and the risk of epithelial ovarian cancer

We evaluated whether genetic variability, as well as menopausal status, modify the association between coffee intake and risk of ovarian cancer. Risk factor information and biologic specimens from three large epidemiological studies, the Nurses' Health Study (NHS), NHSII, and the New England based Case-Control Study of ovarian cancer (NECC) were pooled resulting in 1,354 ovarian cancer cases and 1,851 controls for analysis. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated using conditional (NHS/NHSII) and unconditional (NECC) logistic regression. Coffee consumption was not associated with overall risk (OR = 0.99; 95% CI 0.77-1.28); however, there was a suggested increased risk of ovarian cancer among premenopausal women in the NECC only and an inverse association among postmenopausal women. Carrying one or both of the variant CYP19013 A or CYP19027 G alleles was associated with an 18% increased (P for trend = 0.02) and 15% decreased (P for trend = 0.05) risk of ovarian cancer, respectively. Variation in CYP1A1, CYP1A2, or CYP2A6 did not explain the inconsistent reports of coffee intake and risk. Furthermore, we did not observe any clear gene-environment interactions between caffeine metabolizing genes and ovarian cancer. Future studies evaluating mechanisms by which coffee mediates this relationship are warranted.

Synergism between oral estrogen therapy and cytochrome P450 3A5*1 allele on the risk of venous thromboembolism among postmenopausal women

CONTEXT

Hormone therapy increases the risk of venous thromboembolism (VTE) among postmenopausal women. This effect may be modulated by the expression of cytochromes P450 3A5 (CYP3A5) and 1A2 (CYP1A2) which are involved in the hepatic metabolism of estrogens.

OBJECTIVE

The objective was to investigate the impact of CYP3A5 and CYP1A2 genetic polymorphisms on the association of VTE with hormone therapy.

DESIGN

We conducted a case-control study.

SETTING

This study was conducted in eight French hospital centers and in the general population.

PATIENTS

CYP3A5 and CYP1A2 genotypes were evaluated among 195 cases with a first documented episode of idiopathic VTE and 533 controls matched for center, age, and admission date.

OUTCOME MEASURE

The outcome measure was hormone therapy by route of estrogen administration.

RESULTS

Overall, oral but not transdermal estrogen increased VTE risk [odds ratio (OR) = 4.5, 95% confidence interval (CI) = 2.6-7.6, and OR = 1.2, 95% CI = 0.8-1.8, respectively]. The allele frequency of CYP3A5*1 was 9 and 10% among cases and controls (OR = 1.0; 95% CI = 0.6-1.5) and that of CYP1A2*1F was 72 and 71% among cases and controls (OR = 1.5; 95% CI = 0.8-2.8). Compared with nonusers, OR for VTE in users of oral estrogen was 3.8 (95% CI = 2.1-6.7) among patients without CYP3A5*1 allele and 30.0 (95% CI = 4.4-202.9) among patients with this allele (test for interaction P = 0.04). By contrast, there was no significant interaction between CYP3A5*1 allele and transdermal estrogen on VTE risk. There is no interaction between CYP1A2 genetic polymorphism and hormone therapy on VTE risk.

CONCLUSIONS

Women with CYP3A5*1 allele using oral estrogen can define a subgroup at high VTE risk. Additional data are needed to assess the relevance of this genetic biomarker in the medical management of menopause.

The CYP1A2 genotype modifies the association between coffee consumption and breast cancer risk among BRCA1 mutation carriers

We have recently reported that, among BRCA1 mutation carriers, the consumption of caffeinated coffee was associated with a significant reduction in breast cancer risk. Because the metabolism of caffeine is primarily by CYP1A2, we examined whether or not the CYP1A2 genotype modifies the association between a history of coffee consumption and the risk of breast cancer. A common A to C polymorphism in the CYP1A2 gene is associated with decreased enzyme inducibility and impaired caffeine metabolism. Information regarding coffee consumption habits and the CYP1A2 genotype was available for 411 BRCA1 mutation carriers (170 cases and 241 controls). We estimated the odds ratios (ORs) and 95% confidence intervals (95% CIs) for breast cancer associated with the CYP1A2 genotype and a history of coffee consumption before age 35, adjusting for potential confounders. The CYP1A2 genotype did not affect breast cancer risk. Among women with at least one variant C allele (AC or CC), those who consumed coffee had a 64% reduction in breast cancer risk, compared with women who never consumed coffee (OR, 0.36; 95% CI, 0.18-0.73). A significant protective effect of coffee consumption was not observed among women with the CYP1A2 AA genotype (OR, 0.93; 95% CI, 0.49-1.77). Similar results were obtained when the analysis was restricted to caffeinated coffee. This study suggests that caffeine protects against breast cancer in women with a BRCA1 mutation and illustrates the importance of integrating individual genetic variability when assessing diet-disease associations.

Using pharmacokinetics to predict the effects of pregnancy and maternal-infant transfer of drugs during lactation

Knowledge of pharmacokinetics and the use of a mechanistic-based approach can improve our ability to predict the effects of pregnancy for medications when data are limited. Despite the many physiological changes that occur during pregnancy that could theoretically affect absorption, bioavailability does not appear to be altered. Decreased albumin and alpha(1)-acid glycoprotein concentrations during pregnancy will result in decreased protein binding for highly bound drugs. For drugs metabolised by the liver, this can result in misinterpretation of total plasma concentrations of low extraction ratio drugs and overdosing of high extraction ratio drugs administered by non-oral routes. Renal clearance and the activity of the CYP isozymes, CYP3A4, 2D6 and 2C9, and uridine 5'-diphosphate glucuronosyltransferase are increased during pregnancy. In contrast, CYP1A2 and 2C19 activity is decreased. The dose of a drug an infant receives during breastfeeding is dependent on the amount excreted into the breast milk, the daily volume of milk ingested and the average plasma concentration of the mother. The lipophilicity, protein binding and ionisation properties of a drug will determine how much is excreted into the breast milk. The milk to plasma concentration ratio has large inter- and intrasubject variability and is often not known. In contrast, protein binding is usually known. An extensive literature review was done to identify case reports including infant concentrations from breast-fed infants exposed to maternal drugs. For drugs that were at least 85% protein bound, measurable concentrations of drug in the infant did not occur if there was no placental exposure immediately prior to or during delivery. Knowledge of the protein binding properties of a drug can provide a quick and easy tool to estimate exposure of an infant to medication from breastfeeding.

CYP1A2 polymorphism (C > A at position −163) in Ovambos, Koreans and Mongolians

Cytochrome P450 1A2 (CYP1A2) plays an important role in metabolizing drugs and xenobiotics, and is a possible participant in the development of several human diseases. Recent studies have shown that genetic polymorphism of -163 C > A single nucleotide mutation of CYP1A2 increases the risk of myocardial infarction and modulates CYP1A2 activity. In this study, we investigated the frequency of the -163 C > A mutation in Ovambos (n = 177), Koreans (n = 250) and Mongolians (n = 153) and compared our results with other studies. Detection of this single nucleotide polymorphism was by polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP). The frequencies of mutation (CYP1A2*-163A) in the Ovambos, Koreans and Mongolians were 0.46, 0.32 and 0.21, respectively. Ovambos showed a relatively higher frequency of mutation, similar to that of Tanzanians, while the Mongolians showed the lowest frequency of all study groups, including those from previous studies. This study is the first to investigate the distribution of the CYP1A2 (-163 C > A single nucleotide polymorphism) mutant allele in Ovambo, Korean and Mongolian populations.

Effects of type of smoking (pipe, cigars or cigarettes) on biological indices of tobacco exposure and toxicity

Although all forms of smoking are harmful, smoking pipes or cigars is associated with lower exposure to the lethal products of tobacco products and lower levels of morbidity and mortality than smoking cigarettes. Cytochrome P-450-1A (CYP1A) is a major pathway activating carcinogens from tobacco smoke. Our primary aim was to compare CYP1A2 activity in individuals smoking pipes or cigars only, cigarettes only and in non-smokers. We studied 30 smokers of pipes or cigars only, 28 smokers of cigarettes only, and 30 non-smokers male subjects matched for age. CYP1A2 activity was assessed as the caffeine metabolic ratio in plasma. One-day urine collection was used for determining exposure to products of tobacco metabolism. Nitrosamine and benzo[a]pyrene DNA adducts were measured in lymphocytes. CYP1A2 activity was greater (p<0.0001) in cigarette smokers (median: 0.61; interquartile range: 0.52-0.76) than in pipe or cigar smokers (0.27; 0.21-0.37) and non-smokers (0.34; 0.25-0.42) who did not differ significantly. Urinary cotinine and 1-hydroxypyrene levels were higher in cigarette smokers than in pipe or cigar smokers and higher in the later than in non-smokers. DNA adducts levels were significantly lower in pipe or cigar smokers than in cigarette smokers. In multivariate analysis, cigarette smoking was the only independent predictor of CYP1A2 activity (p<0.0001) and of 1-hydroxypyrene excretion in urine (p=0.0012). In this study, pipe or cigar smoking was associated with lower exposure to products of tobacco metabolism than cigarette smoking and to an absence of CYP1A2 induction. Cigarette smoking was the only independent predictor of CYP1A2 activity in smokers. However, inhalation behaviour, rather than the type of tobacco smoked, may be the key factor linked to the extent of tobacco exposure and CYP1A2 induction. Our results provide a reasonable explanation for the results of epidemiological studies showing pipe or cigar smoking to present fewer health hazards than cigarette smoking.

Effect of Caffeine Intake 12 or 24 Hours Prior to Melatonin Intake and CYP1A2*1F Polymorphism on CYP1A2 Phenotyping by Melatonin

Earlier evidence suggests that melatonin is almost exclusively metabolised by CYP1A2 and could serve as a probe drug for CYP1A2 phenotyping. However, caffeine inhibits the metabolism of melatonin by CYP1A2 and dietary caffeine could be a potential confounder for the measurement of CYP1A2 activity with melatonin. We undertook a 3-phase cross-over study in 12 healthy volunteers to examine whether caffeine (200 mg single dose), taken 12 hr or 24 hr prior to melatonin intake, would affect the results of CYP1A2 phenotyping results as assessed by a spot sample melatonin concentration 1.5 hr after intake of 6 mg of melatonin orally. In addition we examined the influence of the CYP1A2*1F polymorphism on the phenotyping results by combining the present material with another 12 persons from a previous study. Caffeine, co-administered 12 or 24 hr prior to melatonin intake, did not have any significant effect on the 1.5 hr melatonin concentration (P=0.086 for ANOVA), but in two volunteers about 4 times increase in melatonin concentration was observed after caffeine intake 12 hr (but not 24 hr) before phenotyping with melatonin. Also, individuals homozygous for the CYP1A2*1A allele had clearly higher 1.5 hr melatonin concentration compared with the *1F/*1F or the *1F/*1A genotypes. Abstinence from caffeine for 24 hr prior to melatonin intake should be enough to overcome the possible confounding effect of caffeine on the CYP1A2 phenotyping with melatonin. Also, melatonin may be a sensitive probe to detect phenotypic differences with regard to CYP1A2*1F polymorphism. Melatonin might be, thus, advantageous for CYP1A2 phenotyping compared to the standard probe caffeine.

Cytochrome P450 interactions in human cancers: new aspects considering CYP1B1

Molecular epidemiological studies are now a powerful tool to determine differential genetic susceptibilities to cancer-causing agents, and to obtain information on potential mechanisms. Cytochrome P450 (CYP) allelic variants are considered biomarkers of susceptibility to cancer. Such variants have an influence on the bioactivation and thereby on the potency of chemical carcinogens. This is very much straight forward for tobacco smoke-related human cancers. A new aspect is the implication of CYP1B1 in tobacco smoke-related cancers at several organ sites. On this basis, the present review is focused on lung, breast, urinary bladder and head and neck cancer. The CYP profile of the human lung includes CYP1A1, -1B1, -2A6, -2A13, -2B6, -2C18, -2E1, -2F1, -3A5 and -4B1. Polycyclic aromatic hydrocarbons (PAHs) and nitrosamines, as active components of tobacco smoke, appear as primary chemical factors for lung malignancies. For human mammary cancer, the use of hormone replacement therapy (HRT) has been shown to be associated with an increase of breast cancer risk, and there seems to be a link between risks caused by HRT use and modifying polymorphisms of drug/xenobiotic enzymes. Specifically, an association of the CYP1B1*3/*3 genotype with increased breast cancer risks has been postulated. Cigarette smoking is a major cause of human urinary bladder cancer. Arylamines, PAHs and nitrosamines are locally activated within the urothelium. Important CYPs in the bladder epithelium of experimental animals and man are CYP1B1 and -4B1. Alcohol consumption and tobacco smoking are known as the major causes of head and neck cancers. Recently, it appears that a polymorphic variant CYP1B1*3/*3 relates significantly to the individual susceptibility of smokers to head and neck cancer, supporting the view that PAH are metabolically activated through CYP1B1. It appears that CYP1B1 plays a key role for the activation of carcinogens at several organ targets, with a likelihood of complex gene-environment interactions implying Phase II enzymes.

Effects of genetic polymorphisms of MDR1, FMO3 and CYP1A2 on susceptibility to colorectal cancer in Koreans

The aim of the present study was to evaluate the effects on the susceptibility to colorectal cancer (CRC) of genetic polymorphisms in P-glycoprotein (PGP) and the metabolic enzymes cytochrome P450 1A2 (CYP1A2) and flavin-containing monooxygenase 3 (FMO3). We analyzed five single-nucleotide polymorphisms (SNP) in 93 cancer-free volunteers and 111 patients with CRC: one common genetic variant of the PGP-encoding MDR1 gene and four SNP in genes for metabolic enzymes (two SNP in FMO3 and two SNP in CYP1A2). The genotypes and allele frequencies of the MDR1/C3435T, FMO3/G488A, FMO3/A923G and CYP1A2/G-3860 A polymorphisms were not significantly different in cancer-free subjects and CRC patients. However, a significant association was found between the CYP1A2/A-163C polymorphism and the risk of CRC, particularly in elderly (>55 years) subjects and smokers. A phenotyping study in normal smokers showed that the CYP1A2 activity of subjects with the CYP1A2/-163 AA genotype was significantly lower than that of subjects carrying the CYP1A2/-163C allele. Combined results show that the CYP1A2/-163C allele is significantly associated with an increase in CYP1A2 activity and a consequent increased risk of CRC in Koreans, particularly in elderly people and smokers.

Caffeine metabolites in umbilical cord blood, cytochrome P-450 1A2 activity, and intrauterine growth restriction

Studies investigating antenatal caffeine consumption and reproductive outcomes show conflicting results, and most studies have used maternal self-reported caffeine consumption to estimate fetal exposure. This study (n=1,606) was specifically designed to test the association of caffeine and its primary metabolites in umbilical cord blood with intrauterine growth restriction (IUGR). Pregnant women were recruited from 56 obstetric practices and 15 clinics affiliated with six hospitals in Connecticut and Massachusetts between September 1996 and January 2000. In an adjusted model including caffeine only, levels in all quartiles were associated with reduced risk of IUGR. In adjusted analyses including paraxanthine and caffeine, serum paraxanthine levels in the highest quartile were associated with increased risk of IUGR (adjusted odds ratio=3.29, 95% confidence interval: 1.17, 9.22); caffeine remained protective. These conflicting findings suggest that cytochrome P-450 1A2 (CYP1A2) metabolic activity may be associated with IUGR, so the ratio of paraxanthine to caffeine was then modeled. The likelihood of IUGR increased 21% for every one standard deviation change in the ratio (adjusted odds ratio=1.21, 95% confidence interval: 1.07, 1.37), suggesting that CYP1A2 activity, and not the absolute levels of paraxanthine, influences fetal growth. No associations were observed between caffeine or any metabolites and preterm delivery.

Increased clozapine plasma concentrations and side effects induced by smoking cessation in 2 CYP1A2 genotyped patients

Clozapine, an atypical antipsychotic, depends mainly on cytochrome P4501A2 (CYP1A2) for its metabolic clearance. CYP1A2 is inducible by smoking, and lower plasma concentrations of clozapine are measured in smokers than in nonsmokers. Case reports have been published on the effects of discontinuing smoking in patients receiving clozapine, which might lead to elevated plasma concentrations and severe side effects. We present 2 cases on the consequences of smoking cessation in patients receiving this drug. In the first patient, smoking cessation resulted, within 2 weeks, in severe sedation and fatigue, with an approximately 3-fold increase of plasma clozapine concentrations. In the second patient, a very high plasma concentration of clozapine (3004 ng/mL) was measured 6 days following a 16-day stay in a general hospital, during which smoking was prohibited. In the latter patient, the replacement of omeprazole, a strong CYP1A2 inducer, by pantoprazole, a weaker CYP1A2 inducer, could have contributed, in addition to smoking cessation, to the observed strong increase of plasma clozapine concentrations. Genotyping of the 2 patients revealed that they were carriers of the AA genotype for the -164C>A polymorphism (CYP1A2*1F) in intron 1 of CYP1A2 gene, which has previously been shown to confer a high inducibility of CYP1A2 by smoking. Thus, at the initiation of clozapine treatment, smoking patients should be informed that, if they decide to stop smoking, they are encouraged to do so but must inform their prescriber beforehand. Also, because of the increased use of no-smoking policies in many hospitals, studies examining the consequences of such policies on the pharmacokinetics/pharmacodynamics of drugs metabolized by CYP1A2, taking into account different CYP1A2 genotypes, are needed.

Pregnancy-induced changes in pharmacokinetics: a mechanistic-based approach

Observational studies have documented that women take a variety of medications during pregnancy. It is well known that pregnancy can induce changes in the plasma concentrations of some drugs. The use of mechanistic-based approaches to drug interactions has significantly increased our ability to predict clinically significant drug interactions and improve clinical care. This same method can also be used to improve our understanding regarding the effect of pregnancy on pharmacokinetics of drugs. Limited studies suggest bioavailability of drugs is not altered during pregnancy. Increased plasma volume and protein binding changes can alter the apparent volume of distribution (Vd) of drugs. Through changes in Vd and clearance, pregnancy can cause increases or decreases in the terminal elimination half-life of drugs. Depending on whether a drug is excreted unchanged by the kidneys or which metabolic isoenzyme is involved in the metabolism of a drug can determine whether or not a change in dosage is needed during pregnancy. The renal excretion of unchanged drugs is increased during pregnancy. The metabolism of drugs catalysed by select cytochrome P450 (CYP) isoenzymes (i.e. CYP3A4, CYP2D6 and CYP2C9) and uridine diphosphate glucuronosyltransferase (UGT) isoenzymes (i.e. UGT1A4 and UGT2B7) are increased during pregnancy. Dosages of drugs predominantly metabolised by these isoenzymes or excreted by the kidneys unchanged may need to be increased during pregnancy in order to avoid loss of efficacy. In contrast, CYP1A2 and CYP2C19 activity is decreased during pregnancy, suggesting that dosage reductions may be needed to minimise potential toxicity of their substrates. There are limitations to the available data. This analysis is based primarily on observational studies, many including small numbers of women. For some isoenzymes, the effect of pregnancy on only one drug has been evaluated. The full-time course of pharmacokinetic changes during pregnancy is often not studied. The effect of pregnancy on transport proteins is unknown. Drugs eliminated by non-CYP or non-UGT pathways or multiple pathways will need to be evaluated individually. In conclusion, by evaluating the pharmacokinetic data of a variety of drugs during pregnancy and using a mechanistic-based approach, we can start to predict the effect of pregnancy for a large number of clinically used drugs. However, because of the limitations, more clinical, evidence-based studies are needed to fully elucidate the effects of pregnancy on the pharmacokinetics of drugs.