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Biomedical subjects

S Ricard

Publications and source records attributed to S Ricard.

At least 19 recordsLinked to original sources
PubMed2003

Association studies in candidate genes: strategies to select SNPs to be tested.

OBJECTIVE: When numerous single nucleotide polymorphisms (SNPs) have been identified in a candidate gene, a relevant and still unanswered question is to determine how many and which of these SNPs should be optimally tested to detect an association with the disease. Testing them all is expensive and often unnecessary. Alleles at different SNPs may be associated in the population because of the existence of linkage disequilibrium, so that knowing the alleles carried at one SNP could provide exact or partial knowledge of alleles carried at a second SNP. We present here a method to select the most appropriate subset of SNPs in a candidate gene based on the pairwise linkage disequilibrium between the different SNPs. METHOD: The best subset is identified through power computations performed under different genetic models, assuming that one of the SNPs identified is the disease susceptibility variant. RESULTS: We applied the method on two data sets, an empirical study of the APOE gene region and a simulated study concerning one of the major genes (MG1) from the Genetic Analysis Workshop 12. For these two genes, the sets of SNPs selected were compared to the ones obtained using two other methods that need the reconstruction of multilocus haplotypes in order to identify haplotype-tag SNPs (htSNPs). We showed that with both data sets, our method performed better than the other selection methods.

Algorithms↗
PubMed2000

Polymorphisms in the genes encoding platelet-derived growth factor A and alpha receptor.

Platelet-derived growth factors (PDGFs) may play an important role in the development of atherosclerosis acting as chemoattractants and mitogens for vascular smooth muscle cells and macrophages. Three dimeric forms of PDGF (AA, AB, BB) have different activities due to distinct binding properties mediated by two types of PDGF receptors (Ralpha, Rbeta). To investigate the possible contribution of molecular variants in the human PDGF-A and PDGF-Ralpha genes to coronary heart disease we screened these genes for polymorphisms by polymerase chain reaction/single-strand conformation polymorphism analysis. A total of 600 men with myocardial infarction and 717 age-matched male controls from four populations in Northern Ireland and France (the ECTIM Study) were gneotyped for newly identified polymorphisms in the genes encoding PDGF-A (C-26IN3T, H69H, C+12IN5T) and PDGF-Ralpha [-1630 I/D (+/-AACTT), A-1506G, C-1390G, G-956A, C-908A, G-793T, +69 I/D (+/-GA)] using allele-specific oligonucleotides. All PDGF-Ralpha polymorphisms, except C-908A, involving a nucleotide change in a common consensus site for GCF and SP-1 transcription factors, were in nearly complete association, generating two major haplotypes. The PDGF-A and PDGF-Ralpha polymorphisms provided a heterozygosity of 0.69 and 0.40, respectively. Genotype and allele frequencies of the PDGF-A and PDGF-Ralpha polymorphisms did not differ between patients with myocardial infarction and controls in either country. None of the polymorphisms investigated was associated with blood pressure, coronary artery stenosis, or any biochemical parameter available in the ECTIM Study.

Adult↗
PubMed1999

Sequence diversity in 36 candidate genes for cardiovascular disorders.

Two strategies involving whole-genome association studies have been proposed for the identification of genes involved in complex diseases. The first one seeks to characterize all common variants of human genes and to test their association with disease. The second one seeks to develop dense maps of single-nucleotide polymorphisms (SNPs) and to detect susceptibility genes through linkage disequilibrium. We performed a molecular screening of the coding and/or flanking regions of 36 candidate genes for cardiovascular diseases. All polymorphisms identified by this screening were further genotyped in 750 subjects of European descent. In the whole set of genes, the lengths explored spanned 53.8 kb in the 5' regions, 68.4 kb in exonic regions, and 13 kb in the 3' regions. The strength of linkage disequilibrium within candidate regions suggests that genomewide maps of SNPs might be efficient ways to identify new disease-susceptibility genes, provided that the maps are sufficiently dense. However, the relatively large number of polymorphisms within coding and regulatory regions of candidate genes raises the possibility that several of them might be functional and that the pattern of genotype-phenotype association might be more complex than initially envisaged, as actually has been observed in some well-characterized genes. These results argue in favor of both genomewide association studies and detailed studies of the overall sequence variation of candidate genes, as complementary approaches.

Apolipoproteins B↗
PubMed1999

A wide variety of mutations in the parkin gene are responsible for autosomal recessive parkinsonism in Europe. French Parkinson's Disease Genetics Study Group and the European Consortium on Genetic Susceptibility in Parkinson's Disease.

Autosomal recessive juvenile parkinsonism (AR-JP, PARK2; OMIM 602544), one of the monogenic forms of Parkinson's disease (PD), was initially described in Japan. It is characterized by early onset (before age 40), marked response to levodopa treatment and levodopa-induced dyskinesias. The gene responsible for AR-JP was recently identified and designated parkin. We have analysed the 12 coding exons of the parkin gene in 35 mostly European families with early onset autosomal recessive parkinsonism. In one family, a homozygous deletion of exon 4 could be demonstrated. By direct sequencing of the exons in the index patients of the remaining 34 families, eight previously undescribed point mutations (homozygous or heterozygous) were detected in eight families that included 20 patients. The mutations segregated with the disease in the families and were not detected on 110-166 control chromosomes. Four mutations caused truncation of the parkin protein. Three were frameshifts (202-203delAG, 255delA and 321-322insGT) and one a nonsense mutation (Trp453Stop). The other four were missense mutations (Lys161Asn, Arg256Cys, Arg275Trp and Thr415Asn) that probably affect amino acids that are important for the function of the parkin protein, since they result in the same phenotype as truncating mutations or homozygous exon deletions. Mean age at onset was 38 +/- 12 years, but onset up to age 58 was observed. Mutations in the parkin gene are therefore not invariably associated with early onset parkinsonism. In many patients, the phenotype is indistinguishable from that of idiopathic PD. This study has shown that a wide variety of different mutations in the parkin gene are a common cause of autosomal recessive parkinsonism in Europe and that different types of point mutations seem to be more frequently responsible for the disease phenotype than are deletions.

Binding Sites↗
PubMed1998

Polymorphisms of the tumour necrosis factor-alpha gene, coronary heart disease and obesity.

BACKGROUND: Tumour necrosis factor-alpha (TNF-alpha) is a cytokine that has multiple functions. Through its effects on lipid metabolism, coagulation, insulin resistance and endothelial function, TNF-alpha could be involved in cardiovascular pathophysiology. Given this possibility, we hypothesized that polymorphisms of the TNF-alpha gene might be associated with a predisposition to coronary heart disease (CHD). METHODS: The entire coding region and 1053 bp upstream of the transcription start site of the TNF-alpha gene were screened for polymorphisms using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and sequencing. Five polymorphisms were identified: four were located in the upstream region at positions -857, -851, -308, -238 from the first transcribed nucleotide and one was found in a non-translated region at position +691. Six-hundred and forty-one patients with myocardial infarction (MI) and 710 control subjects from the ECTIM Study were genotyped. RESULTS: The genotype frequencies were similar in cases and control subjects in the high-risk population of Belfast and in France; however, the TNF-alpha/-308A allele was more frequent in Belfast than in France (0.242 vs. 0.157; P < 0.0001), and carriers of this allele were more frequently obese than non-carriers [1.52 (1.15-1.99), P < 0.004]. No associations were found for the other polymorphisms. CONCLUSIONS: These results suggest that polymorphisms of the TNF-alpha gene are unlikely to contribute to CHD risk in an important way, but the TNF-alpha/-308 polymorphism should be investigated further in relation to obesity.

Adult↗
PubMed1998

The P-selectin gene is highly polymorphic: reduced frequency of the Pro715 allele carriers in patients with myocardial infarction.

P-selectin is an adhesion molecule, expressed at the surface of activated cells, that mediates the interaction of activated endothelial cells or platelets with leukocytes. P-selectin expression is increased in atherosclerotic plaques, and high plasma levels of this molecule have been observed in patients with unstable angina. We investigated the P-selectin gene as a possible candidate for myocardial infarction (MI). The P-selectin gene is situated on chromosome 1q21-q24, spans >50 kb and contains 17 exons. The sequences of the 5'-flanking region and exons of 40 alleles from patients with MI were screened for polymorphisms using polymerase chain reaction/single-strand conformation polymorphism (PCR-SSCP) and sequencing. Thirteen polymorphisms were identified: five in the 5'-flanking and eight in the exonic sequences. Four polymorphisms (Ser290Asn, Asn562Asp, Leu599Val and Thr715Pro) predicted a change in the amino acid sequence of the P-selectin protein. All P-selectin polymorphisms as well as a common E-selectin polymorphism, Ser128Arg which has been reported as being associated with an increased risk of premature coronary heart disease (CHD), and is in tight linkage disequilibrium with several P-selectin polymorphisms, were investigated in 647 patients with MI and 758 control subjects from four regions of France and Northern Ireland (the ECTIM study). The entire set of P-selectin polymorphisms provided a heterozygosity of 91%. The polymorphisms were tightly associated with one another and displayed patterns of linkage disequilibrium suggesting the existence of highly conserved ancestral haplotypes. The five polymorphisms in the 5'-flanking region of the gene were unrelated to MI or any relevant phenotype measured in the ECTIM study. We inferred that the four missense variants identified in the coding region predicted eight common forms of the P-selectin protein. The Pro715 allele which characterizes one of these forms was less frequent in France than in Northern Ireland ( P < 0.002) and in cases than in controls ( P < 0.002; P < 0.02 after correction for the number of tests). We conclude that the P-selectin gene is highly polymorphic and hypothesize that the Pro715 variant may be protective for MI. Whether this variant affects the properties of the P-selectin protein in a way which is compatible with this hypothesis needs to be checked experimentally.

Adult↗
PubMed1998

New polymorphisms of the angiotensin II type 1 receptor gene and their associations with myocardial infarction and blood pressure: the ECTIM study. Etude Cas-Témoin de l'Infarctus du Myocarde.

OBJECTIVE: In an earlier report, we suggested that a polymorphism located in the 3' untranslated region of the angiotensin II type 1 receptor gene (AT1R+1166 A/C) might interact with the angiotensin I converting enzyme (ACE) insertion/deletion (I/D) polymorphism to increase the risk of myocardial infarction. Since the AT1R+1166 A/C polymorphism does not appear to be functional, we postulated that it might be in linkage disequilibrium with an unidentified functional variant which would affect the regulation of the gene in response to angiotensin II. The present study was conducted to identify new polymorphisms of the AT1R gene that might be responsible for this interaction. METHODS: The first four exons, which are untranslated, and 2.2 kb in the 5' flanking region of the AT1R gene were explored by polymerase chain reaction/single-strand conformation polymorphism. Seven polymorphisms were detected in the 5' region at positions -1424, -810, -713, -521, -214, -213 and -153 upstream from the start of transcription. The genotypes of the -810, -713, -214, -213 and -153 polymorphisms were completely concordant. One substitution was detected at the 55th nucleotide of exon 4. These polymorphisms, together with the +1166 A/C polymorphism and a previously described T/C substitution at the 573th nucleotide of exon 5, were genotyped in the Etude Cas-Témoin de l'Infarctus du Myocarde (ECTIM) study, a multicentre study comparing 651 patients who had survived a myocardial infarction and 728 controls from Belfast (United Kingdom) and Lille, Strasbourg and Toulouse (France). RESULTS: The newly identified polymorphisms were not in linkage disequilibrium with the +1166 A/C polymorphism and therefore could not explain the interaction observed with ACE I/D. None of the polymorphisms was associated with blood pressure levels in control subjects. In the four populations, the A allele of the -810 polymorphism was associated with a lower risk of myocardial infarction (population-adjusted odds ratio of 0.80, confidence interval 0.65-0.97, P< 0.05). CONCLUSIONS: None of the newly identified polymorphisms could account for the previously described interaction between the AT1R+1166 A/C and the ACE I/D polymorphisms affecting the risk of myocardial infarction. However, the present study suggests that AT1R-810 T/A, or other polymorphisms which are in complete association with it, might be associated with the risk of myocardial infarction. Further studies are required to confirm this finding and to identify the functional variants.

Adult↗
PubMed1996

Influence of angiotensin-converting enzyme and angiotensin II type 1 receptor gene polymorphisms on aortic stiffness in normotensive and hypertensive patients.

BACKGROUND: Clinical and experimental studies have demonstrated a major role of the renin-angiotensin system in the functional and structural changes of the large arteries in hypertension. Because genetic studies may help us to understand the mechanisms underlying the involvement of this system in arterial regulation, the present study was designed to assess the contribution of polymorphisms of the ACE insertion/deletion (I/D) and angiotensin II type 1 receptor (AGTR1 A 1166C) genes on aortic stiffness regulation. METHODS AND RESULTS: This study included 311 untreated hypertensive and 128 normotensive subjects. Aortic stiffness was evaluated by measurement of the carotid-femoral pulse-wave velocity (PWV). In normotensive subjects, the two polymorphisms did not influence any of the studied parameters. In hypertensive subjects, there was a decreasing trend of mean PWV with the number of ACE D alleles, but this association became significant only after adjustment for blood pressure (P < .05). Conversely, the AGTR1 A 1166C polymorphism was independently associated with aortic stiffness. Mean values of PWV were 11.6 +/- 2.7 m/s in AGTR1 AA homozygotes, 13.3 +/- 3.3 m/s in AC heterozygotes, and 15.3 +/- 4.3 m/s in CC homozygotes (P < .0001 and P < .00001 after adjustment for age and mean blood pressure, respectively). The percentage of variance of PWV explained by AGTR1 A 1166C polymorphism (11.6%) was much larger than that of ACE I/D polymorphism (1.7%). CONCLUSIONS: These results suggest that in hypertensive but not normotensive subjects, the AGTR1 and ACE genotypes are involved in the regulation of aortic rigidity. The presence of the AGTR1 C allele is a strong independent determinant of aortic stiffness, whereas presence of the ACE 1 allele is weakly associated with increased stiffness.

Adolescent↗
PubMed1996

Role of polymorphic residues of human leucocyte antigen-DR molecules on the binding of human immunodeficiency virus peptides.

A study was made of the binding properties of 96 human immunodeficiency virus peptides to human leucocyte antigen (HLA)-DR1 and HLA-DR103 molecules, which differ by three amino acids at positions 67, 70 and 71 in the beta chains. The affinity of the peptides was characterized by their inhibitory concentrations in competitive binding assays which displace half of the labelled influenza haemagglutinin peptide HA306-318 (IC50). Among the high-affinity peptides (IC50 < or = 1 microM), seven bound to DR1, three to DR103 and five equally well to both alleles (promiscuous peptides). Thirty-two other peptides showed medium or low affinity for DR molecules. The role of polymorphic residues was analysed using six mutated DR molecules, intermediates between DR1 and DR103 and differing by one or two substitutions at positions 67, 70 or 71. We reached the same conclusions when using DR1-specific or DR103-specific peptides: modification of residue 70 had no effect on peptide affinity, but single substitution at positions 67 or 71 decreased the allele specificity of the peptides while double substitution at 67 and 71 completely reversed the peptide specificity. In functional assays, DR-binding peptides are able to outcompete specific T-cell proliferation. Furthermore, modification at position 67 or 70 significantly affects the T-cell response and mutation at position 71 abolishes completely the T-cell proliferation. Thus, the polymorphic positions 67 and 71 contributed to the peptide binding with direct effects on T-cell receptor (TCR) recognition while position 70 seems to be mostly engaged in TCR interactions. Furthermore, our results suggest that polymorphic residues may select allele-specific peptides and also influence the conformation of promiscuous peptides.

Amino Acid Sequence↗
PubMed1996

Polymorphisms of the transforming growth factor-beta 1 gene in relation to myocardial infarction and blood pressure. The Etude Cas-Témoin de l'Infarctus du Myocarde (ECTIM) Study.

Transforming growth factor-beta 1 (TGF-beta 1) plays an important role in the modulation of cellular growth and differentiation and the production and degradation of the extracellular matrix. A number of experimental results suggest that TGF-beta 1 may be involved in cardiovascular physiopathology. In the present study, we assessed whether the TGF-beta 1 gene is a candidate gene for coronary heart disease or hypertension. We screened the coding region and 2181 bp upstream of the TGF-beta gene for polymorphisms and identified seven polymorphisms: 3 in the upstream region of the gene at positions -988, -800, and -509 from the first transcribed nucleotide; 1 in a nontranslated region at position +72; 2 in the signal peptide sequence Leu10-->Pro, Arg25-->Pro; and 1 in the region of the gene coding for the precursor part of the protein not present in the active form, Thr263-->Ile. We analyzed these TGF-beta 1 polymorphisms in 563 patients with myocardial infarction and 629 control subjects from four regions in Northern Ireland and France. The Pro25 allele was more frequent in patients than in control subjects in Belfast (P < .01) and Strasbourg (P < .05). The TGF-beta 1 polymorphisms were not associated with the degree of angiographically assessed coronary artery disease in patients. The presence of a Pro25 allele was associated with a lower systolic pressure in the four control groups (P < .002), and a history of hypertension was significantly less frequent in homozygotes or heterozygotes for Pro25 than in hormozygotes for Arg25 (odds ratio, 0.43, 95% confidence interval, 0.19 to 0.92; P < .03). Since the Pro25 allele was associated with an increased risk of myocardial infarction and a reduced risk of hypertension, we favor a cautious interpretation of these apparently inconsistent results. Other studies will need to verify whether these associations are real.

Adult↗
PubMed1996

Influence of the angiotensin II type 1 receptor gene polymorphism on the effects of perindopril and nitrendipine on arterial stiffness in hypertensive individuals.

Angiotensin-converting enzyme inhibitors improve arterial stiffness independently of blood pressure reduction. Since we have recently shown that in hypertensive individuals the A1166C polymorphism of the angiotensin II type 1 receptor (AT1-R) is an independent determinant of aortic stiffness, we designed the present study to assess the influence of this polymorphism on the changes of aortic stiffness after chronic treatment with the angiotensin-converting enzyme inhibitor perindopril and the calcium channel blocker nitrendipine. Forty perindopril- and 42 nitrendipine-treated hypertensive individuals were studied. We evaluated aortic stiffness by measuring the carotid-femoral pulse wave velocity. Carriers of the AT1-RC allele showed higher baseline values of pulse wave velocity than AA homozygotes (P < .05). In the perindopril group, a threefold greater reduction in pulse wave velocity was observed in carriers of the C allele than in AA homozygotes (-2.85 +/- 0.62 versus -0.94 +/- 0.32 m/s, respectively; P < .001), whereas in the nitrendipine group, pulse wave velocity decreased only in AA homozygotes and not in AT1-R C carriers (-1.38 +/- 0.35 versus +0.04 +/- 0.60 m/s, respectively; P < .01). These results indicate that according to the AT1-R A1166C genotype, an angiotensin-converting enzyme inhibitor and a calcium channel blocker affect pulse wave velocity in opposite ways. Since some evidence shows that increased pulse wave velocity may enhance cardiovascular risk, it might be useful for physicians to consider the AT1-R genotype when prescribing an angiotensin-converting enzyme inhibitor or calcium channel blocker to a hypertensive individual.

Adult↗
PubMed1996

Angiotensinogen gene polymorphisms in IDDM patients with diabetic nephropathy.

Genotypic abnormalities of the renin-ANG system have been suggested as a risk factor for the development of diabetic nephropathy. Cleavage of angiotensinogen is the rate-limiting step in the activation of the renin-ANG system. The TT genotype of a polymorphism encoding threonine instead of methionine (M235T) has been associated not only with increased plasma angiotensinogen concentration but also with essential hypertension. In addition, a polymorphism in the angiotensinogen gene substituting methionine for threonine (T174M) has been associated with hypertension in nondiabetic populations. We studied the relationship between these polymorphisms in the angiotensinogen gene in IDDM patients with diabetic nephropathy (121 men, 74 women, age 40.9 +/- 10 years, diabetes duration 27 +/- 8 years). There was no difference in M235T genotype distribution between IDDM patients with diabetic nephropathy and those with normoalbuminuria: 73/97/25 (37/50/13%) vs. 67/95/23 (36/52/12%) had MM/MT/TT genotypes, respectively. No difference in distribution of T174M genotypes between nephropathic and normoalbuminuric IDDM patients was observed either: 148/44/1 (77/23/0.5%) vs. 141/42/2 (76/23/1%) had TT/TM/MM genotypes, respectively. In patients with nephropathy, systolic blood pressure was higher (161 +/- 22 mmHg [mean +/- SD]) in patients carrying TT genotype of the M235T angiotensinogen polymorphism as compared with patients with MM or MT genotypes (150 +/- 23 mmHg; P = 0.03). We conclude that neither the M235T nor the T174M polymorphism in the angiotensinogen gene contributes to genetic susceptibility to diabetic nephropathy in white IDDM patients, whereas the TT genotype of the M235T is associated with elevated blood pressure in patients with diabetic nephropathy.

Adult↗
PubMed1996

Angiotensin-II type 1 receptor gene polymorphism and diabetic microangiopathy.

BACKGROUND: Genotypic abnormalities of the renin-angiotensin system have been suggested as risk factors for the development of hypertension, diabetic nephropathy and proliferative retinopathy. Most of the known actions of angiotensin-II are exerted through the angiotensin-II type 1 receptor, which is present particularly in vascular smooth muscle cells, myocardium and the kidney. A transversion of adenine to cytosine at nucleotide position 1166 in the gene coding for the angiotensin-II type 1 receptor has been associated with hypertension in the non-diabetic population. METHODS: We studied the relationship between the A1166-->C polymorphism in the angiotensin-II type 1 receptor gene in patients with insulin dependent diabetes mellitus (IDDM) and diabetic nephropathy (121 men, 77 women, age 41 +/- 10 years, diabetes duration 27 +/- 8 years) and in IDDM patients with normoalbuminuria (116 men, 74 women, age 43 +/- 10 years, diabetes duration 27 +/- 8 years). 156 patients (40%) had proliferative retinopathy, 67 patients (17%) had no diabetic retinopathy. RESULTS: There was no difference in genotype distribution between IDDM patients with diabetic nephropathy and normoalbuminuria 103 (52%) / 81 (41%) / 14 (7%) vs. 97 (51%) / 80 (42%) / 13 (7%) had AA/AC/CC genotypes, respectively. The allele frequencies (A/C) in patients with nephropathy (0.73/0.27) and patients with normoalbuminuria (0.72/0.28) were also similar. No difference in genotype distribution between IDDM patients with proliferative retinopathy and without diabetic retinopathy was found either: 77 (50%) / 66 (42%) / 13 (8%) vs. 42 (63%) / 22 (33%) / 3 (4%) had AA/AC/CC genotypes, respectively. CONCLUSIONS: The A1166-->C polymorphism in the angiotensin-II type 1 receptor gene does not contribute to the genetic susceptibility to diabetic nephropathy or proliferative retinopathy in caucasian IDDM patients.

Adult↗
PubMed1995

Influence of angiotensin II type 1 receptor polymorphism on aortic stiffness in never-treated hypertensive patients.

Several clinical and experimental studies have suggested a significant role of angiotensin II in the development of alterations of small and large arteries. The present study was designed to assess the contribution of polymorphism (corresponding to an A1166-->C transversion) of the angiotensin II type 1 receptor (AT1) gene to aortic stiffness. One hundred thirty-four never-treated hypertensive patients were included in the study. Aortic distensibility was evaluated by measuring carotid-femoral pulse wave velocity. Age, systolic and diastolic pressure, and metabolic parameters were similar in the three genotypes. Pulse wave velocity was 11.4 +/- 2.5 m/s in AT1 AA homozygotes, 12.5 +/- 3.2 m/s in AC heterozygotes, and 14.7 +/- 4.0 m/s in CC homozygotes (P = .003, P < .001 after adjustment for age, blood pressure, and body mass index). Moreover, an interaction was found between AT1 genotype and the ratio of total to high-density lipoprotein cholesterol in terms of the development of aortic stiffness. Thus, a positive correlation was observed between the ratio of total to high-density lipoprotein cholesterol and pulse wave velocity in AC and CC (r = .42, P < .001) but not AA patients. These results suggest that the AT1 gene is involved in the development of aortic stiffness in hypertensive patients and could modulate the effects of lipids on large arteries.

Adult↗
PubMed1995

Alcohol intake modulates the effect of a polymorphism of the cholesteryl ester transfer protein gene on plasma high density lipoprotein and the risk of myocardial infarction.

A polymorphism of the CETP gene (CETP/TaqIB) with two alleles B1 (60%) and B2 (40%) has been investigated in relation to lipid variables and the risk of myocardial infarction in a large case-control study (ECTIM) of men aged 25-64. No association was observed between the polymorphism and LDL or VLDL related lipid variables. Conversely, B2 carriers had reduced levels of plasma CETP (P < 0.0001) and increased levels of HDL cholesterol (P < 0.0001) and of other HDL related lipid variables. The effects of the polymorphism on plasma CETP and HDL cholesterol were independent, suggesting the presence of at least two functional variants linked to B2. A search for these variants on the coding sequence of the CETP gene failed to identify them. The effect of B2 on plasma HDL cholesterol was absent in subjects drinking < 25 grams/d of alcohol but increased commensurably, with higher values of alcohol consumption (interaction: P < 0.0001). A similar interaction was not observed for plasma CETP. The odds-ratio for myocardial infarction of B2 homozygotes decreased from 1.0 in nondrinkers to 0.34 in those drinking 75 grams/d or more. These results provide the first demonstration of a gene-environment interaction affecting HDL cholesterol levels and coronary heart disease risk.

Adult↗
PubMed1995

Genetic variation at the angiotensinogen locus in relation to high blood pressure and myocardial infarction: the ECTIM Study.

OBJECTIVES: To study the association between polymorphisms of the angiotensinogen (AGT) gene and blood pressure in population-based samples, and to determine whether genetic variation at the AGT locus is involved in the susceptibility to myocardial infarction. METHODS: The study population comprised 630 cases who survived a myocardial infarction, recruited from the World Health Organization Monitoring Cardiovascular Diseases registers in Belfast, Lille, Strasbourg and Toulouse, and 741 controls drawn from the corresponding populations. The AGT polymorphisms investigated were T174M and M235T. High blood pressure was defined as diastolic blood pressure > 100 mmHg or the use of antihypertensive medication, or both. RESULTS: In the controls the mean +/- SEM frequency of the M174 allele was 0.116 +/- 0.008, and that of the T235 allele was 0.401 +/- 0.013. In the whole population blood pressure levels and prevalence of high blood pressure did not vary according to T174M and M235T genotypes. However, obesity appeared as a crucial factor influencing the relationship between high blood pressure and T174M. In subjects with body mass index < 26 kg/m2 there was a 2.4-fold increase of the prevalence of high blood pressure in carriers of the M174 allele compared with in homozygotes for the T174 allele, whereas no association was detected in subjects with body mass index > 26 kg/m2. The association between high blood pressure and M235T was not significant in either group. The T174M and M235T genotype distributions did not differ between survivors of myocardial infarction and controls. CONCLUSIONS: These data suggest that the AGT gene could be involved in the predisposition to high blood pressure in non-overweight, but not in overweight men, possibly reflecting genetically different types of hypertension. No significant impact of the AGT locus in the risk of non-fatal myocardial infarction was detected.

Adult↗
PubMed1994

Synergistic effects of angiotensin-converting enzyme and angiotensin-II type 1 receptor gene polymorphisms on risk of myocardial infarction.

We reported from our previous multicentre case-control study that the deletion (D) polymorphism of the gene encoding angiotensin-converting enzyme (ACE) was associated with increased risk of myocardial infarction. The main function of ACE is to convert angiotensin I into angiotensin II, which exerts its known cellular actions through the angiotensin II AT1 receptor subtype (AGT1R). We have now investigated the role of a common polymorphism of the AT1 receptor gene (an A-->C transversion at position 1166 of AGT1R) and looked for an interaction between ACE and AGT1R gene polymorphisms on the risk of myocardial infarction. We analysed DNA from 613 patients with myocardial infarction and 723 age-matched population controls. We found a significant interaction between ACE and AGT1R gene polymorphisms; the odds ratio for myocardial infarction associated with the ACE DD genotype was 1.05 (95% CI 0.75-1.49) for subjects without the AGT1R C allele, 1.52 (1.06-2.18) in AC heterozygotes, and 3.95 (1.26-12.4) in CC homozygotes (test for trend, p < 0.02). Among patients defined as low risk by traditional risk factors (serum apolipoprotein B < 1.25 g/L, body-mass index < 26 kg/m2) the interaction was even stronger (odds ratios 1.64 [0.68-3.92], 7.03 [2.61-19.0], and 13.3 [p = 0.05], respectively). These findings, if confirmed, could have clinical implications for the prevention and treatment of coronary heart disease.

Adult↗