Determination of ABCB1 polymorphisms and haplotypes frequencies in a French population

The ATP-binding cassette (ABC) transporter ABCB1, or P-glycoprotein, is a transmembrane efflux pump well known for its implication in drug transport and chemoresistance. ABCB1 substrates include either drugs, such as antiretrovirals and immunomodulators, or physiological molecules like phospholipids. Pharmacogenetic analysis of ABCB1 polymorphisms, in addition to other xenobiotic metabolizing enzymes, might help to personalize and optimize drug therapy. Indeed, some polymorphisms of ABCB1 have been implicated in susceptibility to diseases, changes in drug pharmacokinetics, and in variation of the biological response to drug treatment. In addition, variant and haplotype distributions differ depending on ethnicity. Thus, some ethnies may be at higher risk for adverse events, inefficacy of treatment or prevalence of pathologies. This study aimed to determine frequencies of ABCB1 polymorphisms and haplotypes in a sample of French healthy individuals. DNA was isolated from blood-EDTA. Polymerase chain reaction-restriction fragment length polymorphism and TaqMan single nucleotide polymorphism genotyping assays were used to genotype 227 individuals for T-129C, G-1A, A61G, G1199A, C1236T, T-76A, G2677T/A and C3435T polymorphisms. The observed frequencies of the variant allele for these eight polymorphisms are 0.04, 0.08, 0.09, 0.06, 0.42, 0.46, 0.45 and 0.46 respectively. These polymorphisms are in linkage disequilibrium and haplotype frequencies were determined, the most frequent haplotype being the one with variants at position 1236, 2677 and 3435 and wild-type alleles at the other positions. Finally, the frequencies of these eight ABCB1 polymorphisms in our French individuals supposed to be healthy population are quite similar to those described in other Caucasian populations except for the C3435T polymorphism.

Third Santorini conference pharmacogenomics workshop report: "Pharmacogenomics at the crossroads: what else than good science will be needed for the field to become part of Personalized Medicine?"

This workshop discussed the use of pharmacogenomics knowledge in clinical practice. It was organized in three sections: educational needs, definition of industry as a potential trigger, and regulatory aspects. Regarding pharmacogenomics education, it appears that this is truly lacking, except for patients, who are becoming increasingly educated thanks to the media. Regarding administrators, education is mainly a problem of cost. Indeed, even if cost-effective for society on the whole, pharmacogenomic tests will be expensive for hospitals. Physicians are facing an overabundance of information. They must be helped to bridge the gap between knowledge/research and clinical application. Collaboration between the pharmaceutical industry and the diagnostics industry could be one of the triggers. Moreover, there is a lack of qualification of this information, even though some guidelines are being produced. The Food and Drug Administration organizes workshops that often lead to publications on pharmacogenomic education, genomic data aims and development concepts, which can finally be translated into guidelines. Industry can contribute to pharmacogenomic development, not only through research, but also through marketing activities, which would promote the use of pharmacogenomics by physicians. Legal aspects were also considered in terms of the problem of availability and the degree of qualification of commercial drug tests on the market. The Innovative Medicine Initiative was also presented, which is a public-private partnership to create a biomedical research and development leader to benefit patients and society. Finally, a technical report from the Institute for Prospective Technological Studies on the socioeconomic impact of pharmacogenomics in the EU was presented.

[Present possibilities and future development of clinical proteomics]

This review focuses on "clinical proteomics" which represents an emerging discipline in biomedical research. "Clinical proteomics" relies on the analysis of the proteome, i.e. the entire set of peptides and proteins present in a biological sample, to provide relevant data for diagnosis, prognosis or therapeutic strategies of human pathologies. This new type of approach has tremendous potential for the diagnosis of complex pathologies or for the early detection of cancers. This article reports the conclusions of a workgroup of the French Society for Clinical Biology (SFBC) 2004-2006 which evaluated the status, the impact and the future development of proteomics in the clinical field. It provides therefore a broad view going from the methods already present in the clinical laboratories (multiplex technologies...), to the tools for clinical and basis research including bioinformatics.

Metrological sharp shooting for plasma proteins and peptides: The need for reference materials for accurate measurements in clinical proteomics and in vitro diagnostics to generate reliable results

Reliable study results are necessary for the assessment of discoveries, including those from proteomics. Reliable study results are also crucial to increase the likelihood of making a successful choice of biomarker candidates for verification and subsequent validation studies, a current bottleneck for the transition to in vitro diagnostic (IVD). In this respect, a major need for improvement in proteomics appears to be accuracy of measurements, including both trueness and precision of measurement. Standardization and total quality management systems (TQMS) help to provide accurate measurements and reliable results. Reference materials are an essential part of standardization and TQMS in IVD and are crucial to provide metrological correct measurements and for the overall quality assurance process. In this article we give an overview on how reference materials are defined, prepared and what role they play in standardization and TQMS to support the generation of reliable results. We discuss how proteomics can support the establishment of reference materials and biomarker tests for IVD applications, how current reference materials used in IVD may be beneficially applied in proteomics, and we provide considerations on the establishment of reference materials specific for proteomics. For clarity, we solely focus on reference materials related to serum and plasma.

Compared Effect of Immunosuppressive Drugs Cyclosporine A and Rapamycin on Cholesterol Homeostasis Key Enzymes CYP27A1 and HMG-CoA Reductase

Hyperlipidaemia, i.e. increase in total cholesterol and triglycerides, is a common side-effect of the immunosuppressive drugs rapamycin (RAPA) and cyclosporine A (CsA), and is probably related to inhibition of the 27-hydroxylation of cholesterol (acid pathway of bile acid biosynthesis). This might be one of the causes for the increase in plasma cholesterol, as 27-hydroxycholesterol is a potent suppressor of 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), a key enzyme of cholesterol synthesis. As the sterol 27-hydroxylase (CYP27A1) inhibition by CsA is well known, we evaluated the effect of another immunosuppressive drug, RAPA, on this enzyme in HepG2 mitochondria, which confirmed the dose-dependent inhibition of mitochondrial CYP27A1 by cyclosporine (10-20 microM), while the inhibition by RAPA required a higher dose (50-100 microM). Corresponding K(i) was 10 microM for CsA (non-competitive inhibition) and 110 microM for RAPA (competitive inhibition). Cotreatment with both immunosuppressive drugs showed an additive inhibitory effect on CYP27A1 activity. Later, we analysed the effect of these immunosuppressants on HMGR expression in HepG2 cells, and a dose-dependent up-regulation of HMGR gene expression was observed. The results suggest that RAPA and CsA are both inhibitors of CYP27A1 activity with slightly different mechanisms and that they may accordingly increase HMGR expression.

Enzymes and pharmacogenetics of cardiovascular drugs

To select the best drug for a patient, physicians can use pharmacogenomics to optimize the effective drug and to minimize adverse reactions. Many enzymes are involved in the pharmacokinetic and pharmacodynamic sources of cardiovascular drugs. Taking the antihypertensive drugs as an example, the variability in blood pressure response is very high in different individuals, some of them having an increase in blood pressure. The most important proteins involved in the patient response to a drug are cytochrome P450 (CYP) 2D6, CYP2C19, CYP3A4 and the ABCB1 transporter. These enzymes, at the origin of important side effects or drug interactions, are responsible, at a great extent, of the cardiovascular drug response variability. Genotyping of the most important CYP today is easy while no reliable tool has been developed for the ABC transporters ATPase dependent and linked to the other phase I and phase II enzymes. The second relevant group of enzymes are involved in pharmacodynamic action of cardiovascular drugs: enzymes of the renin-angiotensin system and enzymes of the lipid metabolism. Angiotensin converting enzyme (ACE) is the most studied target with a relevant insertion deletion polymorphism. Contradictory reported data could be explained by ethnic differences or patient sample size which are often too small.

Une étude prospective de la prévalence du syndrome métabolique dans des familles françaises supposées saines

Metabolic syndrome (MS) is a cluster of synergistically interacting cardiovascular risk factors which may have serious consequences for the development of cardiovascular disease and diabetes. In this study, we aimed to estimate the prevalence of MS within presumably healthy French families of the STANISLAS cohort, and to observe biological parameters involved in cardiovascular diseases among the offspring of MS subjects. 371 apparently healthy families (1366 individuals) were examined at two visits with a five-year interval (t0 and t+5). MS prevalence was assessed among parents following the ATP-III definition. Our results show that MS is present in presumably healthy adults of the STANISLAS cohort and increases with age. Moreover, low HDL-C and TNF-alpha may play an important role in the development of MS in childhood, at least in our population. Therefore, a systematic tracking of MS appears to be all the more important as it will permit early management of MS in parents and the installation of efficient preventive measures in children including specific advice for diet and physical activity.

Pharmacogénomique et pharmacoprotéomique

The development of personalized medicine will require improved knowledge of biological variability, particularly concerning the important impact of each individual's genetic makeup. A five-step strategy can be followed when trying to identify genes and gene products involved in differential responses to cardiovascular drugs: 1) Pharmacokinetic-related genes and phenotypes; (2) Pharmacodynamic targets, genes and products; (3) Cardiovascular diseases and risks depending on specific or large metabolic cycles; (4) Physiological variations of previously identified genes and proteins; (5) Environmental influences on them. After summarizing the most well known genes involved in drug metabolism, we used statins as an example. In addition to their economic impact, statins are generally considered to be of significant importance in terms of public health. Individuals respond differently to these drugs depending on multiple polymorphisms. Applying a pharmacoproteomic strategy, it is important to use available information on peptides, proteins and metabolites, generally gene products, in each of the five steps. A profiling approach dealing with genomics as well as proteomics is useful. In conclusion, the ever growing volume of available data will require an organized interpretation of variations in DNA and mRNA as well as proteins, both on the individual and population level.

Heritability of serum hs-CRP concentration and 5-year changes in the Stanislas family study: association with apolipoprotein E alleles

We aimed at estimating additive genetic heritability, household component effect and the influence of common alleles of the apolipoprotein E gene (APOE) on serum high-sensitivity C-reactive protein (hs-CRP) concentrations and the subsequent changes over 5 years. A sub-sample of 320 nuclear families was randomly selected from the Stanislas Family Study. Serum hs-CRP concentration was measured by immunonephelometry at entrance and after 5 years. APOE alleles were determined by restriction fragment length polymorphism. After adjustment for covariates, the number of the epsilon4 allele was negatively associated with serum concentration of hs-CRP in the whole sample, at entrance and 5 years later, without significant interaction with sex by generation groups (P=0.003 and P=0.0003, respectively). However, no significant association was found between epsilon4 allele and 5-year changes in hs-CRP concentration. Using a variance component analysis, no significant genetic influence was shown in family aggregation of both hs-CRP measurements and 5-year changes; the household common component was between 6.5 and 12.8%. In addition, after adjustment for APOE gene polymorphisms, degrees of resemblance were almost unchanged. In the Stanislas Family Study, epsilon4 allele of the APOE gene was associated with lower hs-CRP concentration, but not with 5-year changes. However, variance component analysis did not evidence a significant polygenic effect.

Analysis of the effect of multiple genetic variants of cardiovascular disease risk on insulin concentration variability in healthy adults of the STANISLAS cohort

INTRODUCTION

Given the hypothesis of a common soil for atherosclerosis, type 2 diabetes and metabolic syndrome, we tested the contribution of gene polymorphisms involved in cardiovascular diseases on fasting insulin concentration (FIC).

METHODS

The polymorphisms were investigated by a multiplex assay in 308 apparently healthy French middle-aged men and women, taken from the STANISLAS cohort. FIC was measured by a microparticular enzymatic immunoassay.

RESULTS

After a series of regression analyses involving 34 polymorphisms, FGB -455G/A was the only polymorphism that remained significantly associated with FIC when adjusting the analyses for multiple testing. Stepwise models showed that FGB polymorphism accounted for 4.39% of FIC variability in men. Additionally, interactions between FGB and with environmental factors (alcohol and smoking in men, and BMI in women) were found.

DISCUSSION

To our knowledge, this is the first study reporting an influence of FGB polymorphism on FIC in a healthy population. Our results concord with the already shown link between fibrinogen concentration and FIC, and support the hypothesis of a relationship between fibrinogen and endothelium in FIC homeostasis whose alteration may induce several metabolic disorders. The contribution of this gene, although modest, is consistent with the polygenic nature of insulin levels.

Genetic and environmental contributions to serum ascorbic acid concentrations: the Stanislas Family Study

Although numerous environmental factors are documented to influence serum ascorbic concentrations, little is known about the genetic versus environmental contributions to variation of this trait. The aim of this study was to estimate family correlation and, additive genetic heritability and household effects in a variance component analysis for serum ascorbic acid concentrations. In a sample of ninety French families, information was obtained regarding serum ascorbic acid concentrations, usual dietary intake, lifestyle, and other related covariates. Spouse, parent–offspring and offspring–offspring significant correlation coefficients for serum ascorbic acid concentrations, adjusted for age, cigarette consumption and oral contraceptive use, were 0·432, 0·298 and 0·485, respectively, and for adjusted values for additional diet covariates (vitamin C intake and fruit and vegetable consumption), were 0·362, 0·154 and 0·348, respectively. Variance component analysis for serum ascorbic concentrations showed no significant genetic contribution to variability of this trait. Conversely, household common environment accounted for 27·7 and 42·6 % in parents and offspring, respectively, after adjustment for age, cigarette consumption and oral contraceptive use. After adjustment for the two additional diet covariates (vitamin C intake and fruit and vegetable consumption) household common variance decreased to 13·6 and 30·5 % in parents and offspring, respectively. These results show that serum ascorbic acid concentrations aggregate within healthy families partly due to diet intake but without a significant genetic component.

Variations pré-analytiques des biomarqueursprotéiques

In the area of proteomic, results of analysis were for a long time dependant on analytical variations. Nowadays, due to the emergence of new technologies and controls of data, these variations are less important than those due to preanalytical conditions, which are difficult to overcome. The reasons are due to the number of parameters and to the fact that the biologist is not always fully informed. In this document, we present the main preanalytical factors of variation, and their effects on the results of analysis. New technologies involving mass spectrometry are very promising, but they are very sensitive to parameters like the stability of samples and the choice of the clotting agent. Thus, it is more and more necessary to take these data into account.

Interaction between CYP1A1 T3801C and AHR G1661A polymorphisms according to smoking status on blood pressure in the Stanislas cohort

BACKGROUND

CYP1A1, one of the key enzymes in detoxifying toxic components produced during cigarette smoking, is regulated by aromatic hydrocarbon receptor (AHR). A CYP1A1 T3801C polymorphism, associated with a higher CYP1A1 inducibility and enhanced catalytic activity, has been linked to stroke, triple vessel disease and may, therefore, be associated with blood pressure (BP). The relation of the widely studied G1661A polymorphism of the human AHR gene with BP is unknown.

OBJECTIVES

To investigate the genetic influence of CYP1A1 T3801C and AHR G1661A polymorphisms on BP in relation to tobacco consumption.

DESIGN AND PARTICIPANTS

Study participants were selected from a French longitudinal cohort of volunteers for a free health check-up. These individuals (302 men and 311 women) were not taking medication that can affect blood pressure. Information about active smoking status was obtained by a self-administered questionnaire.

RESULTS

After multiple regression analysis, systolic blood pressure (SBP) and diastolic blood pressure (DBP) did not differ significantly according to their tobacco status excepted for DBP in men. In addition, neither CYP1A1 T3801C nor AHR G1661A polymorphism was linked to blood pressure. However, systolic and diastolic blood pressures differed significantly according to CYP1A1 T3801C genotype between ex-smokers and smokers. Finally, the interaction between CYP1A1 T3801C and AHR G1661A polymorphisms explained a significant difference of SBP and DBP between carriers of both CYP1A1-C3801 and AHR-A1661 alleles.

CONCLUSION

This study is the first to show an interaction between the CYP1A1 T3801C and AHR G1661A polymorphisms. This interaction could explain the difference in blood pressure level between smokers and non-smokers/ex-smokers but needs to be confirmed in a large sample.

The structure of human apolipoprotein E2, E3 and E4 in solution. 2. Multidomain organization correlates with the stability of apoE structure

The stabilities toward thermal and chemical denaturation of three recombinant isoforms of human apolipoprotein E (r-apoE2, r-apoE3 and r-apoE4), human plasma apoE3, the recombinant amino-terminal (NT) and the carboxyl-terminal (CT) domains of plasma apoE3 at pH 7 were studied using near and far ultraviolet circular dichroism (UV CD), fluorescence and size-exclusion chromatography. By far UV CD, thermal unfolding was irreversible for the intact apoE isoforms and consisted of a single transition. The r-apoE3 was found to be less stable as compared to the plasma protein and the stability of recombinant isoforms was r-apoE4<r-apoE3<r-apoE2. The thermal denaturation of the isolated NT- and CT-domains of apoE3 was largely reversible and included two transitions. The NT-domain was more resistant to heating than the CT-domain, both of which were more resistant than the intact protein. By near UV CD, the thermal unfolding was biphasic. When compared, thermal unfolding of the secondary and tertiary structures appeared to occur concurrently in r-apoE2 whereas heating affected the tertiary structure, initially, in r-apoE3 and r-apoE4. Denaturation with guanidine hydrochloride did not follow a two-state transition. A three-state treatment of the denaturation curves revealed the order of stability as r-apoE4<r-apoE3<r-apoE2 for the whole proteins as well as that for the NT-domains, as established by fluorescence and far UV CD spectroscopy, whereas the CT-domains had roughly similar stabilities. There are isoform-specific differences in the stability and in the state of association and the unfolding of both the NT- and CT-domains may be more complex than a two-state transition.

Genetic determinants of blood pressure regulation

Hypertension is a multifactorial disorder that probably results from the inheritance of a number of susceptibility genes and involves multiple environmental determinants. Existing evidence suggests that the genetic contribution to blood pressure variation is about 30-50%. Although a number of candidate genes have been studied in different ethnic populations, results from genetic analysis are still inconsistent and specific causes of hypertension remain unclear. Furthermore, the abundance of data in the literature makes it difficult to piece together the puzzle of hypertension and to define candidate genes involved in the dynamic of blood pressure regulation. In this review, we attempt to highlight the genetic basis of hypertension pathogenesis, focusing on the most important existing genetic variations of candidate genes and their potential role in the development of this disease. Our objective is to review current knowledge and discuss limitations to clinical applications of genotypic information in the diagnosis, evaluation and treatment of hypertension. Finally, some principles of pharmacogenomics are presented here along with future perspectives of hypertension.

Pharmacogenomics and cardiovascular drugs: need for integrated biological system with phenotypes and proteomic markers

Personalized medicine is based on a better knowledge of biological variability, considering the important part due to genetics. When trying to identify involved genes and their products in differential cardiovascular drug responses, a five-step strategy is to be followed: 1) Pharmacokinetic-related genes and phenotypes (2) Pharmacodynamic targets, genes and products (3) Cardiovascular diseases and risks depending on specific or large metabolic cycles (4) Physiological variations of previously identified genes and proteins (5) Environment influences on them. After summarizing the most well-known genes involved in drug metabolism, we will take as example of drugs, the statins, considered as very important drugs from a Public-Health standpoint, but also for economical reasons. These drugs respond differently in human depending on multiple polymorphisms. We will give examples with common ApoE polymorphisms influencing the hypolipemic effects of statins. These drugs also have pleiotropic effects and decrease inflammatory markers. This illustrates the need to separate clinical diseases phenotypes in specific metabolic pathways, which could propose other classifications, of diseases and related genes. Hypertension is also a good example of clinical phenotype which should be followed after various therapeutic approaches by genes polymorphisms and proteins markers. Gene products are under clear environmental expression variations such as age, body mass index and obesity, alcohol, tobacco and dietary interventions which are the first therapeutical actions taken in cardiovascular diseases. But at each of the five steps, within a pharmacoproteomic strategy, we also need to use available information from peptides, proteins and metabolites, which usually are the gene products. A profiling approach, i.e., dealing with genomics, but now also with proteomics, is to be used. In conclusion, the profiling, as well as the large amount of data, will more than before render necessary an organized interpretation of DNA, RNA as well as proteins variations, both at individual and population level.

Cardiovascular risk-associated allele frequencies for 15 genes in healthy elderly French and Chinese

In order to investigate possible ethnic differences in genetic and environmental determinants, we investigated several cardiovascular disease-associated genetic variations in successful ageing populations of France (Nancy) and China (Hong Kong). Allelic frequencies of these genetic variations were compared between healthy elderly Chinese (n=103) and French populations (n=100). A multi-locus assay was used to genotype 15 genes for 29 biallelic sites, genes implicated in lipid and homocysteine metabolism, thrombosis, leukocyte adhesion, and blood pressure regulation. For most of the candidate markers within lipid metabolism genes, the less frequent alleles were more common in the Chinese population compared with the French population, while the less frequent alleles of the majority of the other markers were detected only or more commonly in the French population. In conclusion, polymorphisms in 13 genes exhibited statistically significant differences in allelic frequencies between the two populations. Since the two populations were selected as examples of successful ageing, we could hypothesise that genetic factors that could play a role in a successful ageing process may be different between the two populations.