Contribution of clinical correlates and 13 C-reactive protein gene polymorphisms to interindividual variability in serum C-reactive protein level

Association of AHSG gene polymorphisms with fetuin-A plasma levels and cardiovascular diseases in the EPIC-Potsdam study

BACKGROUND

Elevated circulating levels of fetuin-A in blood have been associated with increased risk of cardiovascular disease. The goal of our study was to prospectively investigate the potential causal nature of the association between fetuin-A levels and myocardial infarction (MI) and ischemic stroke by applying a Mendelian randomization approach.

METHODS AND RESULTS

Five tagging single-nucleotide polymorphisms (rs2248690, rs2070633, rs2070635, rs4917, and rs6787344) capturing the common genetic variation of the fetuin-A coding gene alpha(2)-Heremans-Schmid glycoprotein (AHSG) were genotyped in a case-cohort comprising 214 MI cases, 154 ischemic stroke cases, and 2152 persons who remained free of cardiovascular disease events in the European Prospective Investigation into Cancer and Nutrition-Potsdam study. One single-nucleotide polymorphism (rs6787344) was discarded because of Hardy-Weinberg disequilibrium. All AHSG tagging single-nucleotide polymorphisms were associated with fetuin-A plasma levels (P<0.0001). AHSG rs4917 C>T showed the strongest association, explaining 21.2% of the phenotypic variance independent of potential confounding factors (+35.5 microg/mL increase per C-allele, P= 2 x 10(-121)). Furthermore, the rs4917 C-allele showed a significant association with MI (adjusted hazard rate ratio [RR] 1.34, 95% CI 1.05 to 1.70, P=0.02). Based on this association, the expected RR for MI corresponding to 1 SD in fetuin-A was 1.54 and, thus, strikingly matches the previously observed association between fetuin-A plasma levels and MI risk (RR 1.59).

CONCLUSIONS

These data provide evidence for the causal nature of the recently reported association between fetuin-A plasma levels and MI risk, thereby suggesting an involvement of fetuin-A in the pathogenesis of cardiovascular disease.

Plasma CRP levels in premenopausal women with major depression: a 12-month controlled study

C-reactive protein (CRP), an inflammatory marker of cardiovascular risk, is often elevated in major depressive disorder (MDD). The magnitude and consistency of this elevation have not been previously characterized in premenopausal women with MDD. The aim of the study was to prospectively assess plasma CRP levels, body composition, endocrine and metabolic parameters, and depressive status in premenopausal women with MDD (n=77) and controls (n=41), aged 21 to 45. Women were enrolled in a 12-month, controlled study of bone turnover, the P.O.W.E.R. ( Premenopausal, Osteoporosis, Women, Al Endronate, Dep Ression) Study. Blood samples were taken at Baseline, Month 6, and Month 12. Most subjects with MDD were in clinical remission. These women tended to have consistently higher CRP levels than controls over 12 months (p=0.077). BMI was positively related to log[CRP] in women with MDD only. Nine women with MDD had CRP levels greater than 10 mg/l, a value associated with a very high cardiovascular risk. This subset was obese and had significantly higher triglycerides, total cholesterol, LDL-cholesterol, fasting insulin, and HOMA-IR than the rest of women with MDD. The variations in CRP levels over time were high (intra- and inter-individual coefficients of variations of approximately 30-50% and approximately 70-140%, respectively). No control had CRP levels greater than 10 mg/l. Depression was associated with increased plasma CRP in women with MDD. The clinical significance of abnormal plasma CRP for cardiovascular risk needs to be assessed in large prospective studies of women with depression.

Association of MCP-1 -2518 A/G single nucleotide polymorphism with the serum level of CRP in Slovak patients with ischemic heart disease, angina pectoris, and hypertension

The aim of our work was to find if MCP-1 -2518 (A/G) single nucleotide polymorphism (SNP) influences somehow the serum concentrations of high-sensitive CRP (hsCRP) both in patients suffering from ischemic heart disease (IHD), myocardial infarction (MI), angina pectoris (AP), and hypertension (HT) and in control group of healthy subjects. Totally, 263 patients with the diagnosis of IHD, out of them 89 with MI, 145 with AP, 205 with HT, and also 67 healthy subjects were included in the study. First, we estimated the serum levels of hsCRP. We found that patients with AP had significantly higher serum level of hsCRP than both control group of healthy subjects (P = .043) and IHD patients without AP (P = .026). The presence of the mutant G allele statistically significantly correlated with the higher serum levels of hsCRP in patients with IHD (P = .016), AP (P = .004), and HT (P = .013). Higher correlations were found in men (AP: P = .019; HT: P = .047). In all cases the highest levels of hsCRP were found both in patients and healthy controls with homozygous GG genotype.

C-Reactive protein gene variants are associated with postoperative C-reactive protein levels after coronary artery bypass surgery

Background

Elevated baseline C-reactive protein (CRP) levels are associated with increased risk for developing cardiovascular disease. Several CRP gene variants have been associated with altered baseline CRP levels in ambulatory populations. However, the influence of CRP gene variants on CRP levels during inflammatory states, such as surgery, is largely unexplored. We describe the association between candidate CRP gene variants and postoperative plasma CRP levels in patients undergoing primary, elective coronary artery bypass graft (CABG) surgery with cardiopulmonary bypass (CPB).

Methods

Using a multicenter candidate gene association study design, we examined the association between seventeen candidate CRP single nucleotide polymorphisms (SNPs) and inferred haplotypes, and altered postoperative CRP levels in 604 patients undergoing CABG surgery with CPB. Perioperative CRP levels were measured immediately prior to surgery, post-CPB and on postoperative days (POD) 1–4.

Results

CRP levels were significantly elevated at all postoperative time points when compared with preoperative levels (P < 0.0001). After adjusting for clinical covariates, the minor allele of the synonymous coding SNP, rs1800947 was associated with lower peak postoperative CRP levels (P = 2.4 × 10^-4) and lower CRP levels across all postoperative time points (P = 4.8 × 10^-5). rs1800947 remained highly significant after Bonferroni adjustment for multiple comparisons.

Conclusion

We identified a CRP gene SNP associated with lower postoperative CRP levels in patients undergoing CABG surgery with CPB. Further investigation is needed to clarify the significance of this association between CRP gene variants and the acute-phase rise in postoperative CRP levels with regard to the risk of adverse postoperative outcomes.

C-reactive protein genotypes and haplotypes, polymorphisms in NSAID-metabolizing enzymes, and risk of colorectal polyps

INTRODUCTION

C-reactive protein (CRP) is a nonspecific marker of inflammation linked to cardiovascular disease and possibly colon cancer. Polymorphisms in CRP have been associated with differential CRP concentrations among healthy adults, with some evidence for functional effects on CRP expression.

METHODS

A linkage disequilibrium-based tag single nucleotide polymorphism (SNP)-selection algorithm identified six tagSNPs for Europeans (-821A>G, -390C>T/A, 90A>T, 838G>C, 2043G>A, and 4363C>A), defining six haplotypes with more than 1% frequency. In a case-control study of adenomatous (n=491) or hyperplastic (n=184) polyps versus polyp-free controls (n=583) we investigated these SNPs in relation to colorectal polyp risk.

RESULTS

Individuals with 838 GC or CC genotypes had a modestly, although not statistically significantly, increased risk of adenomas (odds ratio: 1.4 95% confidence interval: 0.9-2.1) and a nearly 2-fold increased risk of concurrent adenomas and hyperplastic polyps (odds ratio: 2.0 95% confidence interval: 1.1-3.6). Increased risk for concurrent adenomas and hyperplastic polyps was also observed for haplotype ACACAC. No other main associations were detected. Risk of adenomas associated with 2043G>A differed with nonsteroidal anti-inflammatory drug (NSAID) use. Among NSAID nonusers, there was a suggestion that the GA or AA genotypes were associated with decreased risk of adenomas; this was not seen among NSAID users (P interaction=0.03). We also observed interactions between UGT1A1 [TA](7) promoter repeat polymorphism and CRP tagSNPs -390C>T/A and 90A>T, in which only the homozygous variant CRP genotype was associated with increased risk of adenoma among those with the UGT1A1 6rpt/6rpt genotype (P interaction=0.02 and 0.04 for -390C>T/A and 90A>T, respectively).

CONCLUSION

These results provide limited support for associations between genetic variation in CRP and colorectal polyp risk. The observed interactions should be evaluated further.

The relation of genetic and environmental factors to systemic inflammatory biomarker concentrations

BACKGROUND

Environmental and genetic correlates of inflammatory marker variability are incompletely understood. In the family-based Framingham Heart Study, we investigated heritability and candidate gene associations of systemic inflammatory biomarkers.

METHODS AND RESULTS

In offspring participants (n=3710), we examined 11 inflammatory biomarkers (CD40 ligand, C-reactive protein, intercellular adhesion molecule-1, interleukin-6, urinary isoprostanes, monocyte chemoattractant protein-1, myeloperoxidase, P-selectin, tumor necrosis factor-alpha, tumor necrosis factor receptor II, fibrinogen). Heritability and bivariate genetic and environmental correlations were assessed by Sequential Oligogenic Linkage Analysis routines in 1012 family members. We examined 1943 tagging single-nucleotide polymorphisms in 233 inflammatory pathway genes with >or=5 minor allele carriers using a general genetic linear model. Clinical correlates explained 2.4% (CD40 ligand) to 28.5% (C-reactive protein) of the variability in inflammatory biomarkers. Estimated heritability ranged from 10.9% (isoprostanes) to 44.8% (P-selectin). Most correlations between biomarkers were weak although statistically significant. A total of 45 single-nucleotide polymorphism-biomarker associations met the q-value threshold of 0.25. Novel top single-nucleotide polymorphisms were observed in ICAM1 gene in relation to intercellular adhesion molecule-1 concentrations (rs1799969, P=1.32 x 10(-8)) and MPO in relation to myeloperoxidase (rs28730837, P=1.9 x 10(-5)). Lowest P values for trans-acting single-nucleotide polymorphisms were observed for APCS with monocyte chemoattractant protein-1 concentrations (rs1374486, P=1.01 x 10(-7)) and confirmed for IL6R with interleukin-6 concentrations (rs8192284, P=3.36 x 10(-5)). Novel potential candidates (APCS, MPO) need to be replicated.

CONCLUSIONS

Our community-based data support the relevance of clinical and genetic factors for explaining variation in inflammatory biomarker traits.

C-reactive protein polymorphisms and genetic susceptibility to ischemic stroke and hemorrhagic stroke in the Chinese Han population

AIM

The inflammatory marker C-reactive protein (CRP) has been strongly correlated with the risk of cardiovascular disease. Some single-nucleotide polymorphisms (SNPs) have been reported to be associated with serum CRP levels. In this study, we assessed the genetic association between SNPs within the CRP gene and ischemic and hemorrhagic stroke in the Han Chinese population.

METHODS

This study comprises 564 ischemic stroke patients, 220 hemorrhagic stroke patients and 564 controls from the ethnic Han Chinese population in Wuhan. Four CRP SNPs, -757A>G (rs3093059), -717A>G (rs2794521), -286C>T>A (rs3091244) and +2147C>T (rs1205), were genotyped from patients using TaqMan assays.

RESULTS

The A allele frequency for the -717A>G polymorphism was significant higher in controls than in ischemic stroke patients (P=0.037), after adjustment for traditional risk factors (odds ratio 0.28; 95% CI 0.12-0.65; P=0.003), suggesting a protective effect for this allele against ischemic stroke. Haplotype analysis showed that the H3 (G-C-C) haplotype conferred a significantly increased risk of ischemic stroke (odds ratio 1.052, 95% CI 1.001-1.106: P=0.047). Neither CRP genotypes nor haplotypes showed an association with hemorrhagic stroke. However, the frequency for haplotype H5 (A-T-C) was significantly higher in ischemic stroke than hemorrhagic stroke patients (P=0.0003).

CONCLUSION

These data suggest that the CRP gene -717A allele confers a protective effect against ischemic stroke. Furthermore, the H3 haplotype (G-C-C) is an independent risk marker for ischemic stroke, whereas the H5 haplotype (A-T-C) can be used as a prognostic marker of hemorrhagic stroke.

Influence of single-nucleotide polymorphisms on C-reactive protein levels in chronic kidney disease before and after kidney transplantation

INTRODUCTION

We sought to evaluate 2 single-nucleotide polymorphisms (SNPs) in the C-reactive protein (CRP) gene promoter region for their effects on CRP levels in chronic kidney disease (CKD) patients before and after a successful kidney transplantation.

METHODS

Fifty CKD patients were evaluated before and at the first and second years after the graft. Two SNPs were studied, a bi-allelic (G-->A) at the -409 and a tri-allelic (C-->T-->A) variation at the -390 position in the CRP gene.

RESULTS

All patients presented the -409GG genotype. At the -390 position, the "A" allele was not found; there were 15 "CC" patients, 11 "TT" patients, and 24 "CT" patients. CRP levels were different among patients with various genotypes (P < .019). Also the presence of the allele "T" was sufficient to determine differences in CRP levels both in pretransplantation (P = .045) and at 1 year posttransplantation (P = .011), but not at the second year (P = .448).

CONCLUSION

SNPs at the -390 position of the CRP gene promoter region influence CRP basal levels in such a way that the "C" allele correlated with the lowest and the "T" with the highest. We did not observe this influence in our patients at the second year posttransplantation.

C-Reactive Protein Gene Polymorphisms in Biopsy-proven Giant Cell Arteritis from Northwestern Spain

Objective.

To investigate the potential implication of several polymorphisms of the C-reactive protein (CRP) gene in the predisposition to or clinical expression of giant cell arteritis (GCA).

Methods.

A total of 125 patients diagnosed with biopsy-proven GCA and 234 ethnically matched controls from the Lugo region of Northwestern Spain were included in our study. Four functional gene polymorphisms for CRP rs1417938, rs1800947, rs1205, and rs3093059 variants were assessed using a polymerase chain reaction system with predeveloped TaqMan allelic discrimination assay.

Results.

Although we observed a significant increase in the frequency of heterozygotes for rs1417938 A/T [odds ratio (OR) = 1.70; 95% confidence interval (CI) 1.04–2.80; p = 0.03] and rs1205 C/T (OR 1.73; 95% CI 1.07–2.78; p = 0.02) in patients with GCA, no statistically significant differences in the allelic frequencies of these 2 polymorphisms were found between patients with GCA and controls. A marginal significant increase in the frequency of rs3093059 allele T in patients with GCA compared to controls was observed (OR 1.81; 95% CI 0.97–3.39; p = 0.04). However, the increased frequency of patients with GCA homozygous for rs3093059 T/T in patients with GCA compared to controls was out of the range of significance (OR 1.77; 95% CI 0.92–3.40; p = 0.07). No significant differences were found when we stratified patients with GCA according to the presence of polymyalgia rheumatica or severe ischemic complications of the disease.

Conclusion.

The functional CRP gene polymorphisms assessed in our study do not seem to play a major role in the pathogenesis of GCA in individuals from Northwestern Spain.

Association of the FTO rs9939609 single nucleotide polymorphism with C-reactive protein levels

Adipose tissue is a key factor determining C-reactive protein (CRP) plasma levels. Variation at the fat-mass and obesity-associated (FTO) gene locus has been reported to be associated with increased body fat. We investigated whether the FTO rs9939609 T>A single nucleotide polymorphism might alter CRP levels in a population-based sample of 2,415 participants from a large prospective cohort study. Genotype/phenotype relationships were studied by linear trend analysis stratified by sex. The rs9939609 A-allele was significantly associated with CRP levels in both genders (men, +21%, P = 0.002; women, +14%, P = 0.01 per A-allele). The association was attenuated, but remained statistically significant after additional adjustment for BMI, waist-to-hip ratio, and other potential confounding factors (men, +14%, P = 0.03; women, +12%, P = 0.02; per A-allele). Similar results were obtained when subjects with CRP levels higher then 10 mg/l were excluded. Our data provide preliminary evidence that the FTO rs9939609 T>A polymorphism contributes to variation in plasma CRP levels independently of obesity indices.

The interaction of adiposity with the CRP gene affects CRP levels: age, gene/environment susceptibilty-Reykjavik study

OBJECTIVE

Common diseases often have an inflammatory component reflected by associated markers such as serum C-reactive protein (CRP) levels. Circulating CRP levels have also been associated with adipose tissue as well as with specific CRP genotypes. We examined the interaction between measures of body mass index (BMI), waist circumference and fat percent (total fat measured by bioimpedance) with genotypes of the CRP gene in the determination of CRP levels.

METHODS

The first 2296 participants (mean age 76+/-6 years, 42% men) in the Age, Gene/Environment Susceptibility-Reykjavik Study, a multidisciplinary epidemiological study to determine risk factors in aging, were genotyped for 10 single nucleotide polymorphisms (SNPs) in the CRP gene. General linear models with age and terms for interaction of CRP genotypes with BMI, waist circumference and percent fat were used to evaluate the association of genotypes to CRP levels (high-sensitivity method, range 0-10 mg l(-1)) in men and women separately.

RESULTS

We focused on the SNP rs1205 that represents the allele that captures the strongest effects of the gene on CRP levels. Carriers of the rs1205 G allele had significantly higher CRP levels than noncarriers in a dose-dependent manner. Compared to the AA genotype, the slope of the increase in CRP with increasing BMI (P=0.045) and waist circumference (P=0.014) was different for the G allele carriers and of similar magnitude in both men and women. The rs1205 interactions were not significant for fat mass percent, suggesting a possible association with fat localization.

CONCLUSIONS

This study further illuminates the known association between measures of adiposity and CRP levels and is shown to be dependent on variation in the rs1205 SNP of the CRP gene. The correlated increase in CRP levels with adiposity is accentuated by presence of the G allele.

FcgammaRIIa genotype is associated with acute coronary syndromes as first manifestation of coronary artery disease

OBJECTIVE

Identification of clinically relevant determinants for acute coronary syndromes (ACS) promises reduction of ACS-associated mortality. C-reactive protein (CRP) has proved to be useful identifying people at risk for cardiovascular events. However, it is unknown whether genetic variants at Fcgamma receptor IIa (FcgammaRIIa), the main receptor for CRP, are involved in CRP-related cardiovascular risk. We evaluated the potential impact of FcgammaRIIa through a genetic association study in patients with ACS.

METHODS AND RESULTS

We conducted a genetic association study among 701 consecutive patients with first event of ACS compared to 467 patients with stable angina pectoris. All patients were genotyped for a frequent functional variant at position 131 of the mature FcgammaRIIa, where the arginine (R) allele results in an increased signal transduction upon CRP binding. In our study, the R/R131 genotype was significantly associated with ACS as the first manifestation of coronary artery disease (P=1.2x10(-9), odds ratio 2.86, 95% CI: 2.06-3.99) compared to the non-R/R131 genotype.

CONCLUSIONS

Our data show a genetic association of the FcgammaRIIa R/R131 genotype with a more frequent occurrence of ACS as the first manifestation of coronary artery disease, probably mediated via its interaction with CRP. Genotyping of this FcgammaRIIa variant could help to improve risk stratification in the course of coronary disease in the future.

C-reactive protein and coronary heart disease: predictive test or therapeutic target?

BACKGROUND

The hepatocyte-derived acute-phase reactant C-reactive protein (CRP) has been the subject of intense research over the last 2 decades for its possible role in the pathogenesis of cardiovascular diseases. This research has spawned interest in the use of the blood concentration of CRP for predicting a first coronary heart disease (CHD) event, which has been made possible with the development of high-sensitivity CRP (hsCRP) assays that can measure the typically low concentrations of CRP that circulate in the absence of an overt infective or inflammatory episode, and as a potential causal factor that might be targeted therapeutically. The research has encompassed observational and genetic epidemiology, basic science studies with cells and tissues, experiments with animal models and humans, and randomized trials (although not of specific CRP-lowering therapies as yet).

CONTENT

We focus on investigations of the potential role of small differences in basal hsCRP concentration seen in healthy individuals and the relationship of such differences to the long-term risk of a first CHD event, rather than on research devoted to the high acute-phase CRP concentrations, which occur after acute atherothrombotic events and can influence the severity of ischemic tissue damage and the subsequent prognosis. We concentrate mainly on research findings at the translational interface and draw on evidence from human observational and genetic epidemiology, as well as from randomized trials.

CONCLUSIONS

As the field matures from one of discovery to an evaluative science, the development of possible clinical applications requires a sharpening of focus on and a critical appraisal of the strengths and deficiencies of the accumulated evidence. Such assessments require attention to both the current state of affairs and the design of future research, so that the existing uncertainties about the utility of CRP in predicting CHD and its role in causing this disease can be resolved.

Impact of genetic and environmental factors on hsCRP concentrations and response to therapeutic agents

BACKGROUND

Inflammation plays an instrumental role in all stages of atherosclerosis. High-sensitivity C-reactive protein (hsCRP), a systemic inflammatory marker, has been gaining recognition as an independent risk factor for cardiovascular disease (CVD). Both baseline hsCRP concentrations and drug-induced hsCRP changes are highly variable and potentially subject to genetic regulation.

CONTENT

This review summarizes the current studies examining the effect of genetic and environmental factors on baseline plasma hsCRP concentrations, with a main focus on C-reactive protein, pentraxin-related (CRP) genetic polymorphisms and various dietary components that affect hsCRP concentrations. We also address the association of CRP genetic variations with CVD risk, a relationship that may support or refute the causality of CRP in the atherosclerotic process. Moreover, we discuss the impact of CRP genetic polymorphisms on hsCRP changes in response to 3-week fenofibrate treatment in the genetic intervention of the Genetics of Lipid Lowering Drugs and Diet Network study.

SUMMARY

Genetic variants on the CRP locus and other loci and dietary and lifestyle factors are responsible for the interindividual variability of plasma hsCRP concentrations. CRP genetic variants further influence differing plasma hsCRP response after 3-week fenofibrate treatment in patients with metabolic syndrome. Future studies focusing on the influence and interaction of genetic variation on the hsCRP response to dietary and other behavior modification as well as drug treatment could have important implications for the development of more personalized preventive and therapeutic approaches to reduce CVD.

Association between C-reactive protein gene haplotypes and C-reactive protein levels in Taiwanese: interaction with obesity

OBJECTIVE

The level of C-reactive protein (CRP), an inflammatory marker that predicts future cardiovascular events, is a heritable trait. Our aim was to test the statistical associations between variations in the CRP gene and serum CRP levels in a Taiwanese population with interaction analysis.

METHODS

A sample population of 617 Taiwanese subjects was enrolled. Five CRP single nucleotide polymorphisms (SNPs) previously reported to be associated with CRP level and with reasonable coverage of the CRP gene region were analyzed using polymerase chain reaction and restriction enzyme digestion or by TaqMan SNP Genotyping Assays.

RESULTS

After adjusting for clinical covariates, minor alleles of 3 of the 5 SNPs were associated with change in CRP level: rs3091244 and rs1205 were associated with increased CRP level (P=0.001 and P<0.001, respectively) and rs1800947 with decreased CRP level (P=0.003). Two haplotypes inferred from 5 SNPs (GCGCG and AAGCG) were associated with increased CRP level (P=0.017 and P<0.0001, respectively). Interaction analysis revealed interaction of obesity with CRP genotypes associated with high CRP level (interaction P=0.034 and 0.020 for SNPs rs2794521 and rs1800947, respectively). An effect of obesity on CRP level was also noted in haplotype interaction analysis with the association occurring predominantly in obese subjects (P=0.034).

CONCLUSION

CRP polymorphisms are independently associated with increased or decreased CRP level in Taiwanese. Further, CRP genotypes/haplotypes interact with obesity to set CRP level. These findings have implications for the prediction of atherosclerotic disease.

Genetically elevated C-reactive protein and ischemic vascular disease

BACKGROUND

Elevated levels of C-reactive protein (CRP) are associated with increased risks of ischemic heart disease and ischemic cerebrovascular disease. We tested whether this is a causal association.

METHODS

We studied 10,276 persons from a general population cohort, including 1786 in whom ischemic heart disease developed and 741 in whom ischemic cerebrovascular disease developed. We examined another 31,992 persons from a cross-sectional general population study, of whom 2521 had ischemic heart disease and 1483 had ischemic cerebrovascular disease. Finally, we compared 2238 patients with ischemic heart disease with 4474 control subjects and 612 patients with ischemic cerebrovascular disease with 1224 control subjects. We measured levels of high-sensitivity CRP and conducted genotyping for four CRP polymorphisms and two apolipoprotein E polymorphisms.

RESULTS

The risk of ischemic heart disease and ischemic cerebrovascular disease was increased by a factor of 1.6 and 1.3, respectively, in persons who had CRP levels above 3 mg per liter, as compared with persons who had CRP levels below 1 mg per liter. Genotype combinations of the four CRP polymorphisms were associated with an increase in CRP levels of up to 64%, resulting in a theoretically predicted increased risk of up to 32% for ischemic heart disease and up to 25% for ischemic cerebrovascular disease. However, these genotype combinations were not associated with an increased risk of ischemic vascular disease. In contrast, apolipoprotein E genotypes were associated with both elevated cholesterol levels and an increased risk of ischemic heart disease.

CONCLUSIONS

Polymorphisms in the CRP gene are associated with marked increases in CRP levels and thus with a theoretically predicted increase in the risk of ischemic vascular disease. However, these polymorphisms are not in themselves associated with an increased risk of ischemic vascular disease.

Air Pollution and Inflammatory Response in Myocardial Infarction Survivors: Gene–Environment Interactions in a High-Risk Group

Ambient air pollution has been associated with an increased risk of hospital admission and mortality in potentially susceptible subpopulations, including myocardial infarction (MI) survivors. The multicenter epidemiological study described in this report was set up to study the role of air pollution in eliciting inflammation in MI survivors in six European cities, Helsinki, Stockholm, Augsburg, Rome, Barcelona, and Athens. Outcomes of interest are plasma concentrations of the proinflammatory cytokine interleukin 6 (IL-6) and the acute-phase proteins C-reactive protein (CRP) and fibrinogen. In addition, the study was designed to assess the role of candidate gene polymorphisms hypothesized to lead to a modification of the short-term effects of ambient air pollution. In total, 1003 MI survivors were recruited and assessed with at least 2 repeated clinic visits without any signs of infections. In total, 5813 blood samples were collected, equivalent to an average of 5.8 repeated clinic visits per subject (97% of the scheduled 6 repeated visits). Subjects across the six cities varied with respect to risk factor profiles. Most of the subjects were nonsmokers, but light smokers were included in Rome, Barcelona, and Athens. Substantial inter- and intraindividual variability was observed for IL-6 and CRP. The study will permit assessing the role of cardiovascular disease risk factors, including ambient air pollution and genetic polymorphisms in candidate genes, in determining the inter- and the intraindividual variability in plasma IL-6, CRP, and fibrinogen concentrations in MI survivors.

New evidences for C-reactive protein (CRP) deposits in the arterial intima as a cardiovascular risk factor

Inflammatory processes are orchestrated by several soluble molecules, which interact with cell populations involved. Cytokines, chemokines, acute-phase reactants, and hormones are crucial in the evolution of several inflammatory disorders, such as atherosclerosis. Several evidences suggest that C-reactive protein (CRP) started to be considered as a cardiovascular risk factor, since CRP directly induces atheroslerosis development. The recent demonstration of CRP production not only by the liver, but also within atherosclerotic plaques by activated vascular cells, also suggests a possible dual role, as both a systemic and tissue agent. Although more studies are needed, some therapeutic approaches to reduce CRP levels have been performed with encouraging results. However, given the strong limitations represented by its low specificity and still accordingly with the American Heart Association, there is no need for high sensitivity CRP screening of the entire adult population as a public-health measure. The measure of serum CRP might be useful only for patients who are considered at intermediate risk.

Very low C-reactive protein in apparently healthy individuals: physiological status or just a reflection of an improved health profile

The objective of our study was to determine whether the very low concentrations of C-reactive protein (CRP) detected by high-sensitivity CRP (hs-CRP) assays that one encounters from time to time in apparently healthy individual represent a physiological status or are just a reflection of an improved general health profile. The concentration of hs-CRP was determined by using the Behring BN II nephelometer. The arbitrary cut-off point of hs-CRP (<or=0.16 mg l(-1)) was determined at the lower detection level of the assay. A total of 6588 apparently healthy individuals were screened following exclusion of recent infection/inflammation by using a detailed questionnaire. One hundred and sixty (2.4%) individuals out of the above-mentioned cohort presented hs-CRP concentrations of <or=0.16 mg l(-1). They were found to be significantly younger and lean, had an improved lipid profile and an attenuated acute-phase response in terms of lower erythrocyte sedimentation rate and fibrinogen concentration as well as white blood cell count. In addition, these individuals had less atherothrombotic risk factors, except for smoking habits which were as frequent as in those of individuals with a higher hs-CRP concentration. After calculating the concentration of this biomarker following multiple adjustments, the individuals with very low CRP remained with a very low value despite the multiplicity of the adjustments. We raise the possibility that this particular low concentration might represent a physiological status and is not necessarily a result of the improved general health profile per se.

C-reactive protein and coronary heart disease: a critical review

Modestly elevated baseline concentrations of C-reactive protein (CRP), the classical acute phase protein, are associated with the long-term risk of coronary heart disease in general populations, whilst the major acute phase response of CRP following myocardial infarction is associated with death and cardiac complications. The pathogenic and clinical significance of these associations is controversial. Here we critically review the evidence and describe large-scale epidemiological studies, novel experiments and possible specific therapies which will rigorously inform the debate. We distinguish between the potential pathogenicity of high acute phase circulating CRP concentrations in individuals with substantial tissue damage and modest but persistent increases in baseline values in generally healthy subjects.

C-reactive protein (CRP) elevation in patients with abdominal aortic aneurysm is independent of the most important CRP genetic polymorphism

OBJECTIVE

C-reactive protein (CRP) is a marker of cardiovascular disease. The objective was to determine if abdominal aortic aneurysm (AAA) and CRP serum concentration and its CRP gene are associated.

METHODS AND RESULTS

AAA patients and AAA negative controls were recruited. CRP concentration was measured and the single nucleotide polymorphism (SNP), rs3091244, assessed. AAA cases were divided into those measuring 30-55 mm and >55 mm in diameter, to assess correlation of CRP with AAA size. A total of 248 (227 male) cases and 400 (388 male) controls were included. CRP concentration was higher in cases (385.0 microl/dL [310.4-442.8] vs 180.3 microl/dL [168.1-196.9]; P < .0001). It was higher in large aneurysms (685.7 microl/dL [511.8-1083.0] vs 291.0 microl/dL [223.6-349.6]; P < .0001), with significant correlation observed to size (r = 0.37, P < .0001). CC was the most common SNP genotype with no difference in distribution (P = .43) between cases and controls. No difference existed in CRP for each genotype in the overall cohort (P = .17), cases (P = .18) and controls (P = .19).

CONCLUSION

The results demonstrate that CRP production may be related to the presence of AAA, especially in advanced disease. The serum concentration of CRP does not appear to be influenced by the functional SNP of the CRP gene, which also appears to have no association with AAA formation.

Epidemiology, heritability, and genetic linkage of C-reactive protein in African Americans (from the Jackson Heart Study)

C-reactive protein (CRP) has been studied largely in white non-Hispanic cohorts. There is limited information on CRP's range of values, heritability, and relation to cardiovascular disease risk factors in African Americans. The aim of this study was to evaluate the distribution, clinical correlates, heritability, and genetic linkage of log-transformed CRP in participants in the middle-aged to elderly African American cohort in the community-based Jackson Heart Study. The distribution and correlates of CRP were analyzed for the entire study cohort who underwent the first examination (2001 to 2004). Heritability was estimated for the family cohort nested within the larger Jackson Heart Study (246 families, n = 1,317). The relation between CRP and cardiovascular disease risk factors was tested with multivariable stepwise regression analyses. Heritability was estimated using a variance-components method. Linkage analysis was performed using the multipoint variance-components approach. The study sample consisted of 4,919 participants (mean age 55 +/- 13 years, 63% women); the median CRP concentration was 2.7 mg/L. In stepwise models, traditional risk factors explained 23.8% of CRP's variability, with body mass index (partial R(2) = 13.6%) explaining 57.1% of the variability of CRP due to traditional risk factors. The heritability of CRP (adjusted for age, gender, and body mass index) was 0.45. The strongest linkage evidence for CRP was observed on chromosome 11 (11p13 to 11p11.2), with a logarithm of odds score of 2.72. In conclusion, in this large population-based cohort of African Americans, circulating CRP concentration was heritable and associated with several traditional cardiovascular risk factors, particularly body mass index.

Maternal and fetal C-reactive protein genotype and first trimester CRP concentrations in maternal plasma

Maternal plasma CRP concentrations in pregnancy are increased over pre-pregnancy values and high concentrations have been associated with adverse obstetrical outcomes. The objective of this study was to explore the relationship between maternal and fetal variation in C-reactive protein (CRP) genotype and maternal plasma CRP concentrations in the first trimester in low risk patients. DNA was extracted from maternal and cord blood of subjects in a prospective observational cohort. Single-nucleotide polymorphism (SNP) selection was made using a linkage disequilibrium bin approach. CRP concentrations were measured in first trimester maternal plasma using an enzyme-linked immunosorbent assay (ELISA) kit. Kruskal-Wallis rank testing was used to analyze genetic and clinical determinants of CRP concentrations. Genotype results were available in 190 mother-baby pairs. There was no significant difference in CRP concentration among maternal or fetal CRP genotypes. Thus, first trimester concentrations of maternal plasma CRP in low risk subjects do not appear to be significantly associated with CRP genotype. Instead, differences in clinical factors probably have more influence on baseline maternal CRP concentrations.

Does high C-reactive protein concentration increase atherosclerosis? The Whitehall II Study

BACKGROUND

C-reactive protein (CRP), a marker of systemic inflammation, is associated with risk of coronary events and sub-clinical measures of atherosclerosis. Evidence in support of this link being causal would include an association robust to adjustments for confounders (multivariable standard regression analysis) and the association of CRP gene polymorphisms with atherosclerosis (Mendelian randomization analysis).

METHODOLOGY/PRINCIPAL FINDINGS

We genotyped 3 tag single nucleotide polymorphisms (SNPs) [+1444T>C (rs1130864); +2303G>A (rs1205) and +4899T>G (rs 3093077)] in the CRP gene and assessed CRP and carotid intima-media thickness (CIMT), a structural marker of atherosclerosis, in 4941 men and women aged 50-74 (mean 61) years (the Whitehall II Study). The 4 major haplotypes from the SNPs were consistently associated with CRP level, but not with other risk factors that might confound the association between CRP and CIMT. CRP, assessed both at mean age 49 and at mean age 61, was associated both with CIMT in age and sex adjusted standard regression analyses and with potential confounding factors. However, the association of CRP with CIMT attenuated to the null with adjustment for confounding factors in both prospective and cross-sectional analyses. When examined using genetic variants as the instrument for serum CRP, there was no inferred association between CRP and CIMT.

CONCLUSIONS/SIGNIFICANCE

Both multivariable standard regression analysis and Mendelian randomization analysis suggest that the association of CRP with carotid atheroma indexed by CIMT may not be causal.

The association of C-reactive protein and CRP genotype with coronary heart disease: findings from five studies with 4,610 cases amongst 18,637 participants

Background

It is unclear whether C-reactive protein (CRP) is causally related to coronary heart disease (CHD). Genetic variants that are known to be associated with CRP levels can be used to provide causal inference of the effect of CRP on CHD. Our objective was to examine the association between CRP genetic variant +1444C>T (rs1130864) and CHD risk in the largest study to date of this association.

Methods and Results

We estimated the association of CRP genetic variant +1444C>T (rs1130864) with CRP levels and with CHD in five studies and then pooled these analyses (N = 18,637 participants amongst whom there were 4,610 cases). CRP was associated with potential confounding factors (socioeconomic position, physical activity, smoking and body mass) whereas genotype (rs1130864) was not associated with these confounders. The pooled odds ratio of CHD per doubling of circulating CRP level after adjustment for age and sex was 1.13 (95%CI: 1.06, 1.21), and after further adjustment for confounding factors it was 1.07 (95%CI: 1.02, 1.13). Genotype (rs1130864) was associated with circulating CRP; the pooled ratio of geometric means of CRP level among individuals with the TT genotype compared to those with the CT/CC genotype was 1.21 (95%CI: 1.15, 1.28) and the pooled ratio of geometric means of CRP level per additional T allele was 1.14 (95%CI: 1.11, 1.18), with no strong evidence in either analyses of between study heterogeneity (I² = 0%, p>0.9 for both analyses). There was no association of genotype (rs1130864) with CHD: pooled odds ratio 1.01 (95%CI: 0.88, 1.16) comparing individuals with TT genotype to those with CT/CC genotype and 0.96 (95%CI: 0.90, 1.03) per additional T allele (I²<7.5%, p>0.6 for both meta-analyses). An instrumental variables analysis (in which the proportion of CRP levels explained by rs1130864 was related to CHD) suggested that circulating CRP was not associated with CHD: the odds ratio for a doubling of CRP level was 1.04 (95%CI: 0.61, 1.80).

Conclusions

We found no association of a genetic variant, which is known to be related to CRP levels, (rs1130864) and having CHD. These findings do not support a causal association between circulating CRP and CHD risk, but very large, extended, genetic association studies would be required to rule this out.

Inflammation, insulin resistance, and diabetes--Mendelian randomization using CRP haplotypes points upstream

BACKGROUND

Raised C-reactive protein (CRP) is a risk factor for type 2 diabetes. According to the Mendelian randomization method, the association is likely to be causal if genetic variants that affect CRP level are associated with markers of diabetes development and diabetes. Our objective was to examine the nature of the association between CRP phenotype and diabetes development using CRP haplotypes as instrumental variables.

METHODS AND FINDINGS

We genotyped three tagging SNPs (CRP + 2302G > A; CRP + 1444T > C; CRP + 4899T > G) in the CRP gene and measured serum CRP in 5,274 men and women at mean ages 49 and 61 y (Whitehall II Study). Homeostasis model assessment-insulin resistance (HOMA-IR) and hemoglobin A1c (HbA1c) were measured at age 61 y. Diabetes was ascertained by glucose tolerance test and self-report. Common major haplotypes were strongly associated with serum CRP levels, but unrelated to obesity, blood pressure, and socioeconomic position, which may confound the association between CRP and diabetes risk. Serum CRP was associated with these potential confounding factors. After adjustment for age and sex, baseline serum CRP was associated with incident diabetes (hazard ratio = 1.39 [95% confidence interval 1.29-1.51], HOMA-IR, and HbA1c, but the associations were considerably attenuated on adjustment for potential confounding factors. In contrast, CRP haplotypes were not associated with HOMA-IR or HbA1c (p = 0.52-0.92). The associations of CRP with HOMA-IR and HbA1c were all null when examined using instrumental variables analysis, with genetic variants as the instrument for serum CRP. Instrumental variables estimates differed from the directly observed associations (p = 0.007-0.11). Pooled analysis of CRP haplotypes and diabetes in Whitehall II and Northwick Park Heart Study II produced null findings (p = 0.25-0.88). Analyses based on the Wellcome Trust Case Control Consortium (1,923 diabetes cases, 2,932 controls) using three SNPs in tight linkage disequilibrium with our tagging SNPs also demonstrated null associations.

CONCLUSIONS

Observed associations between serum CRP and insulin resistance, glycemia, and diabetes are likely to be noncausal. Inflammation may play a causal role via upstream effectors rather than the downstream marker CRP.

Association of parental hypertension with concentrations of select biomarkers in nonhypertensive offspring

Children of parents with hypertension are at increased risk of developing high blood pressure. We hypothesize that circulating concentrations of putative biomarkers (that may play a role in development of high blood pressure) are higher in nonhypertensive offspring of parents with hypertension. We compared concentrations of 4 different biomarkers (urinary albumin:creatinine ratio, circulating C-reactive protein, aldosterone:renin ratio, and plasminogen activator inhibitor-1) in nonhypertensive Framingham offspring study participants with none (n=233), 1 (n=474), or both (n=322) parents with hypertension. Parental hypertension was defined as onset before age 60 years, based on longitudinal observations of the original Framingham cohort. Serum C-reactive protein concentrations were higher in nonhypertensive offspring with 1 (median: 1.7; Q1 to Q3: 0.8 to 3.6 mg/L) or both parents with hypertension (median: 1.8; Q1 to Q3: 0.7 to 3.6 mg/L) compared with offspring without parental hypertension (median: 1.4; Q1 to Q3: 0.7 to 3.2 mg/L). In multivariable analyses, parental hypertension was associated with higher serum C-reactive protein concentration in offspring (15% increase per parent with hypertension; P=0.004). Prospectively, the relation of parental hypertension to longitudinal changes in blood pressure in the nonhypertensive offspring was attenuated on adjustment for C-reactive protein (P=0.04 for attenuation). The levels of the other biomarkers evaluated did not significantly differ in offspring according to parental hypertension status. In conclusion, serum C-reactive protein concentrations are higher in nonhypertensive offspring of parents with hypertension. These data suggest that inflammation may partly mediate the familial influences on hypertension risk.

Fine-mapping the genetic basis of CRP regulation in African Americans: a Bayesian approach

Basal levels of C-reactive protein (CRP) have been associated with disease, particularly future cardiovascular events. Twin studies estimate 50% CRP heritability, so the identification of genetic variants influencing CRP expression is important. Existing studies in populations of European ancestry have identified numerous cis-acting variants but leave significant ambiguity over the identity of the key functional polymorphisms. We addressed this issue by typing a dense map of CRP single-nucleotide polymorphisms (SNPs), and quantifying serum CRP in 594 unrelated African Americans. We used Bayesian model choice analysis to select the combination of SNPs best explaining basal CRP and found strong support for triallelic rs3091244 alone, with the T allele acting in an additive manner (Bayes factor > 100 vs. null model), with additional support for a model incorporating both rs3091244 and rs12728740. Admixture analysis suggested SNP rs12728740 segregated with haplotypes predicted to be of recent European origin. Using a cladistic approach we confirmed the importance of rs3091244(T) by demonstrating a significant partition of haplotype effect based on the rs3091244(C/T) mutation (F = 8.91, P = 0.006). We argue that weaker linkage disequilibrium across the African American CRP locus compared with Europeans has allowed us to establish an unambiguous functional role for rs3091244(T), while also recognising the potential for additional functional mutations present in the European genome.

C-reactive protein genotypes associated with circulating C-reactive protein but not with angiographic coronary artery disease: the LURIC study

AIMS

Circulating C-reactive protein is associated with future cardiovascular events. The causal role of C-reactive protein in the development of atherosclerosis remains controversial.

METHODS AND RESULTS

We analysed the association between three genetic polymorphisms (PM) (-717C>T, rs2794521; +1059G>C, rs1800947; +1444C>T, rs1130864) at the C-reactive protein locus and related haplotypes with both circulating C-reactive protein and angiographic coronary artery disease (CAD). The concentration of C-reactive protein was similar in patients with stable CAD and in controls, but increased in patients presenting with acute coronary syndromes. In models adjusting for the main confounding variables, the minor alleles of the +1059G>C (rs1800947) and the +1444C>T PM (rs1130864) were associated with decreased and increased concentrations of C-reactive protein, respectively. Haplotypes 1 and 4 decreased, and haplotype 2 increased C-reactive protein, whereas haplotype 3 had no appreciable effect. None of the genetic variants affecting circulating C-reactive protein was consistently associated with the prevalence of angiographic CAD.

CONCLUSION

A causal role of C-reactive protein in the development of CAD would require that genetic PM resulting in long-term modulation of the concentration of C-reactive protein be themselves associated with CAD. We were not able to detect such a relationship, which can be attributed to either a very small genetic effect size or the relationship between C-reactive protein and cardiovascular events may reflect confounding and reverse causation.

Loci related to metabolic-syndrome pathways including LEPR,HNF1A, IL6R, and GCKR associate with plasma C-reactive protein: the Women's Genome Health Study

Although elevated levels of C-reactive protein (CRP) independently predict increased risk of development of metabolic syndrome, diabetes, myocardial infarction, and stroke, comprehensive analysis of the influence of genetic variation on CRP is not available. To address this issue, we performed a genome-wide association study among 6345 apparently healthy women in which we evaluated 336,108 SNPs as potential determinants of plasma CRP concentration. Overall, seven loci that associate with plasma CRP at levels achieving genome-wide statistical significance were found (range of p values for lead SNPs within the seven loci: 1.9 x 10(-)(8) to 6.2 x 10(-)(28)). Two of these loci (GCKR and HNF1A) are suspected or known to be associated with maturity-onset diabetes of the young, one is a gene-desert region on 12q23.2, and the remaining four loci are in or near the leptin receptor protein gene, the apolipoprotein E gene, the interleukin-6 receptor protein gene, or the CRP gene itself. The protein products of six of these seven loci are directly involved in metabolic syndrome, insulin resistance, beta cell function, weight homeostasis, and/or premature atherothrombosis. Thus, common variation in several genes involved in metabolic and inflammatory regulation have significant effects on CRP levels, consistent with CRP's identification as a useful biomarker of risk for incident vascular disease and diabetes.

Ethnic differences in C-reactive protein concentrations

BACKGROUND

Limited data exist regarding the ethnic differences in C-reactive protein (CRP) concentrations, an inflammatory marker associated with risk of cardiovascular disease (CVD). We hypothesized that known CVD risk factors, including anthropometric characteristics, would explain much of the observed ethnic variation in CRP.

METHODS

We performed a cross-sectional analysis of 3154 women, without known CVD and not receiving hormone therapy, enrolled in the Study of Women's Health Across the Nation (SWAN), a multiethnic prospective study of pre- and perimenopausal women.

RESULTS

The study population was 47.4% white, 27.7% African-American, 8.5% Hispanic, 7.7% Chinese, and 8.6% Japanese; mean age was 46.2 years. African-American women had the highest median CRP concentrations (3.2 mg/L), followed by Hispanic (2.3 mg/L), white (1.5 mg/L), Chinese (0.7 mg/L), and Japanese (0.5 mg/L) women (all pairwise P < 0.001 compared with white women). Body mass index (BMI) markedly attenuated the association between ethnicity and CRP. After adjusting for age, socioeconomic status, BMI, and other risk factors, African-American ethnicity was associated with CRP concentrations >3 mg/L (odds ratio 1.37, 95% CI 1.07-1.75), whereas Chinese and Japanese ethnicities were inversely related (0.58, 0.35-0.95, and 0.43, 0.26-0.72, respectively).

CONCLUSIONS

Modifiable risk factors, particularly BMI, account for much but not all of the ethnic differences in CRP concentrations. Further study is needed of these ethnic differences and their implications for the use of CRP in CVD risk prediction.

Single nucleotide polymorphisms in inflammation-related genes and mortality in a community-based cohort in Washington County, Maryland

The purpose of this study was to examine the associations between single nucleotide polymorphisms (SNPs) in genes controlling inflammatory processes and mortality. Data were analyzed from 9,933 individuals who participated in two large community-based cohort studies conducted in Washington County, Maryland, in 1974 and 1989, designated "CLUE I" and "CLUE II," respectively. DNA from blood collected in 1989 was genotyped for 47 SNPs in 23 inflammation-related genes, including interferon-gamma (IFNgamma), lymphotoxin-alpha (LTalpha), tumor necrosis factor-alpha (TNFalpha), C-reactive protein (CRP), peroxisome proliferator-activated receptor (PPAR), and the human endothelial nitric oxide synthase (eNOS). All participants were followed from 1989 to the date of death or to June 20, 2005. The results showed no observable patterns of association for the SNPs and the all-cause and cause-specific mortality outcomes, although statistically significant associations were observed between at least one mortality outcome and SNPs in eNOS (reference SNP (rs) 1799983), PPARG (rs4684847), CRP (rs2794521), IFNgamma (rs2069705), TNFalpha (rs1799964), and LTalpha (rs2229094). Additionally, three of the four examined CRP SNPs were strongly associated with CRP serum concentration among those with CRP measurements. The authors' findings from this community-based prospective cohort study suggest that the selected SNPs are not associated with overall or cause-specific death, although CRP genotypes may be associated with systemic inflammation.

Quantification of the genetic component of basal C-reactive protein expression in SLE nuclear families

C-reactive protein (CRP) is a heritable acute-phase plasma protein also expressed at low, basal, levels in healthy individuals. Elevated basal CRP has been associated with increased cardiovascular risk, while CRP dysregulation may be a feature of systemic lupus erythematosus (SLE). In this cohort of 496 Caucasian SLE families we estimated basal CRP heritability, h(2)= 27.7%. We typed a dense map of CRP single nucleotide polymorphisms (SNPs) and found that seven were associated with basal CRP using both a regression approach and an orthogonal family-based test (P = 0.001-0.011), as were haplotypes carrying the minor allele of these SNPs. SNPs in the interleukin-1beta and interleukin-6 genes were associated with basal CRP. No association was seen between CRP genotype and SLE. Using a variance components approach we estimated that the CRP genotype accounted for only 15% of the total genetic component of basal CRP variation, perhaps explaining the limited evidence of association between CRP and disease. Most of the genetic determinants of basal CRP variation therefore remain unknown. Multiple genes may be involved and identifying them will provide an insight into pathways regulating CRP expression, highlight potential cardiovascular disease and SLE candidates and improve the ability of basal CRP to predict cardiovascular risk.

Relation of smoking status to a panel of inflammatory markers: the framingham offspring

AIMS

We sought to investigate the hypothesis that smoking is accompanied by systemic inflammation.

METHODS AND RESULTS

We examined the relation of smoking to 11 systemic inflammatory markers in Framingham Study participants (n=2944, mean age 60 years, 55% women, 12% ethnic minorities) examined from 1998-2001. The cohort was divided into never (n=1149), former (n=1424), and current smokers with last cigarette >6h (n=134) or < or =6h (n=237) prior to phlebotomy. In multivariable-adjusted models there were significant overall between-smoking group differences (defined as p<0.0045 to account for multiple testing) for every inflammatory marker tested, except for serum CD40 ligand (CD40L), myeloperoxidase (MPO) and tumor necrosis factor receptor-2 (TNFR2). With multivariable-adjustment, pair-wise comparisons with never smokers revealed that former smokers had significantly lower concentrations of plasma CD40L (p<0.0001) and higher concentrations of (CRP) C-reactive protein (p=0.002).

CONCLUSIONS

As opposed to never smokers, those with acute cigarette smoke exposure (< or =6h) had significantly higher concentrations of all markers (p<0.0001) except serum CD40L, MPO, and TNFR2; plasma CD40L were significantly lower. Compared with never smokers, cigarette smokers have significantly elevated concentrations of most circulating inflammatory markers, consistent with the hypothesis that smoking is associated with a systemic inflammatory state.

Genetic determinants of basal C-reactive protein expression in Filipino systemic lupus erythematosus families

Basal C-reactive protein (CRP) is a heritable trait associated with long-term cardiovascular disease risk. Existing studies leave ambiguity over the key functional polymorphisms and fail to adjust for trans-acting effects. In a novel cohort of 285 Filipino systemic lupus erythematosus probands and their first-degree relatives, we quantified serum CRP and typed a dense map of CRP single-nucleotide polymorphisms (SNPs), along with SNPs in the interleukin-1 beta, interleukin-6 and apolipoprotein E genes. Ten CRP SNPs demonstrated association with basal CRP in a regression model (P=0.011-0.002). These delineated two haplotypes associated with high and low basal CRP expression (P=0.002). Differences in allele frequency were seen compared with Caucasian populations, enabling us to argue for an independent genetic effect from a phylogenetically distinct haplotype tagged by SNP rs1800947. We demonstrated an association between Apo epsilon 2 and higher basal CRP. Interleukin-6 genotype was associated with basal CRP, highlighting a role for acute-phase cytokines even in basal expression. Identifying these trans-acting variants may improve the use of basal CRP as a predictor cardiovascular risk, and increase our power to detect associations between CRP and disease.

1059G/C polymorphism within the exon 2 of the C-reactive protein gene: relationship to C-reactive protein levels and prognosis in unstable angina

OBJECTIVE

Patients with unstable angina (UA) and high C-reactive protein (CRP) have increased cardiovascular risk. Whether genetic factors such as the synonymous 1059G/C polymorphism within the exon 2 of the human CRP gene determine CRP levels and outcome is unclear.

METHODS

In 105 consecutive patients with UA, we assessed the CRP 1059G/C polymorphism, CRP plasma levels and interleukin-6 production after in-vitro stimulation of whole blood with lipopolysaccharide (1 ng/ml). Coronary events during a 24-month follow-up were recorded.

RESULTS

CRP levels (median, range) were significantly lower among C-allele carriers (2.3 mg/l, 0.5-26.9) than among GG homozygotes (5.9 mg/l, 0.8-72.12, P=0.009). Interleukin-6 production was lower in C-allele carriers (1645 pg/ml, 832.0-9522) than in GG homozygotes (3929 pg/ml, 670.8-10 582), (P=0.085). At follow-up, 1059C-allele carriers experienced fewer coronary events than 1059GG homozygotes (13 vs. 47%, P=0.021). At multivariable analysis, a CRP level >3 mg/l, but not the 1059G/C polymorphism, was an independent predictor of coronary events (odds ratio 10.04, 95% confidence interval 2.84-35.44, P=0.0002).

CONCLUSION

This study shows that the CRP synonymous 1059G/C polymorphism affects CRP levels. No independent association was, however, observed between this polymorphism and clinical outcome in UA.

C-reactive protein (CRP) gene polymorphisms, CRP levels, and risk of incident coronary heart disease in two nested case-control studies

BACKGROUND

C-reactive protein (CRP), an acute phase reactant and marker of inflammation, has been shown to predict risk of incident cardiovascular events. However, few studies have comprehensively examined six common single-nucleotide polymorphisms (SNPs) in the CRP gene, haplotypes, and plasma CRP levels with risk of coronary heart disease (CHD).

METHODS AND FINDINGS

We conducted parallel nested case-control studies within two ongoing, prospective cohort studies of U.S. women (Nurses' Health Study) and men (Health Professionals Follow-up Study). Blood samples were available in a subset of 32,826 women and 18,225 men for biomarker and DNA analyses. During 8 and 6 years of follow-up, 249 women and 266 men developed incident nonfatal myocardial infarction or fatal CHD, and controls (498 women, 531 men) were matched 2:1 on age, smoking, and date of blood draw from participants free of cardiovascular disease at the time the case was diagnosed. Among both women and men, minor alleles were significantly associated with higher CRP levels for SNPs 1919A>T and 4741G>C, but associated with lower CRP levels for SNPs 2667G>C and 3872C>T. SNP 2667G>C was individually associated with increased risk of CHD in both women [OR 1.57 (95% CI 1.01-2.44); p = 0.047] and men [1.93 (95% CI 1.30-2.88); p = 0.001]. Two of the five common haplotypes were associated with lower CRP levels, and Haplotype 4 which included minor alleles for 2667 and 3872 was associated with significantly lower CRP levels and an elevated risk of CHD. The remaining SNPs or haplotypes were not associated with CHD in both populations.

CONCLUSIONS

Common variation in the CRP gene was significantly associated with plasma CRP levels; however, the association between common SNPs and CRP levels did not correspond to a predicted change in CHD risk. The underlying inflammatory processes which predict coronary events cannot be captured solely by variation in the CRP gene.

Genetics of the Framingham Heart Study population

This chapter provides an introduction to the Framingham Heart Study and the genetic research related to cardiovascular diseases conducted in this unique population. It briefly describes the origins of the study, the risk factors that contribute to heart disease, and the approaches taken to discover the genetic basis of some of these risk factors. The genetic architecture of several biological risk factors has been explained using family studies, segregation analysis, heritability, and phenotypic and genetic correlations. Many quantitative trait loci underlying cardiovascular diseases have been discovered using different molecular markers. Additionally, initial results from genome-wide association studies using 116,000 markers and the prospects of using 550,000 markers for association studies are presented. Finally, the use of this unique sample to study genotype and environment interactions is described.

Mendelian randomization: Using genes as instruments for making causal inferences in epidemiology

Observational epidemiological studies suffer from many potential biases, from confounding and from reverse causation, and this limits their ability to robustly identify causal associations. Several high-profile situations exist in which randomized controlled trials of precisely the same intervention that has been examined in observational studies have produced markedly different findings. In other observational sciences, the use of instrumental variable (IV) approaches has been one approach to strengthening causal inferences in non-experimental situations. The use of germline genetic variants that proxy for environmentally modifiable exposures as instruments for these exposures is one form of IV analysis that can be implemented within observational epidemiological studies. The method has been referred to as 'Mendelian randomization', and can be considered as analogous to randomized controlled trials. This paper outlines Mendelian randomization, draws parallels with IV methods, provides examples of implementation of the approach and discusses limitations of the approach and some methods for dealing with these.

When do social inequalities in C-reactive protein start? A life course perspective from conception to adulthood in the Cardiovascular Risk in Young Finns Study

BACKGROUND

It is unclear when in the life course do social inequalities in inflammation emerge. We examined whether the association between socioeconomic position (SEP) and C-reactive protein (CRP) is determined at conception, in childhood, adolescence or adulthood in 1484 participants from the population-based Cardiovascular Risk in Young Finns Study.

METHODS

Five variants of the CRP gene were used to investigate whether SEP differences in CRP levels are determined at conception. SEP and serum CRP were assessed in childhood (age 3-9), adolescence (age 12-18) and in adulthood (age 24-39). SEP was measured using parental education and occupational status in childhood and adolescence, and participants' own education and occupational status in adulthood. Participants with CRP > 10 mg/l were excluded.

RESULTS

All CRP gene variants were associated with circulating CRP concentrations in childhood, but there were no differences in the distribution of these variants by SEP. No strong evidence was found of associations between parental SEP and CRP. A graded association between higher SEP and lower CRP was observed in adulthood for education (P = 0.0005) but not for occupational status. Trajectories that led to high educational achievement both in the participants and their parents were associated with lower (P <or= 0.047) CRP levels in adulthood. Excluding participants with infectious diseases, pregnant or lactating women and women using oral contraceptives did not change the findings.

CONCLUSION

In this cohort, SEP differences in CRP concentrations seen in adulthood appear not to be determined at conception or evident in childhood or adolescence.

C-reactive protein, inflammatory conditions, and cardiovascular disease risk

BACKGROUND

It is uncertain to what extent high C-reactive protein (CRP) concentrations reflect the presence of inflammatory conditions in the community.

METHODS

We evaluated 3782 Framingham Offspring Study participants (mean age 55 years; 52% women) free of baseline cardiovascular disease. Logistic regression models examined the prevalence of common inflammatory conditions by CRP categories, while a separate matched case-referent analysis evaluated the prevalence of uncommon inflammatory conditions. Cox models were used to assess the influence of common inflammatory conditions on relations between CRP and incident cardiovascular disease.

RESULTS

Common inflammatory conditions were reported by nearly half of the participants; these individuals were more likely to have markedly high CRP concentrations (>10 mg/L, P for trend=.001). In multivariable models, there were increased odds of having at least one common inflammatory condition with CRP concentrations of 1-3.0, 3.01-10, and >10 mg/L, compared with the referent category (<1 mg/L); the respective odds ratios with 95% confidence intervals were 1.41 (1.07-1.86), 1.45 (1.07-1.98), and 1.64 (1.09-2.47) in men, and 1.08 (0.82-1.43), 1.07 (0.80-1.44), and 1.38 (0.97-1.96) in women. In case-referent analyses, uncommon inflammatory conditions were more common in individuals with CRP >10 mg/L compared with those with CRP <1 mg/L (12.1% vs 6.6%; P=.0001). In multivariable models, higher CRP categories were not associated with incident cardiovascular disease, and with additional adjustment for inflammatory conditions, results remained unchanged.

CONCLUSION

There is high prevalence of common and uncommon inflammatory conditions in individuals with high CRP concentrations. Higher CRP concentrations should be interpreted with caution in cardiovascular disease risk assessment.

Interleukin-6 receptor gene variations, plasma interleukin-6 levels, and type 2 diabetes in U.S. Women

OBJECTIVE

To examine the associations between common variations in the IL6R gene and circulating interleukin (IL)-6 levels and diabetes risk.

RESEARCH DESIGN AND METHODS

We determined 10 linkage disequilibrium (LD)-tagging single nucleotide polymorphisms (SNPs) (SNP1 to SNP10) for the IL6R gene in a nested case-control study of 672 diabetic and 1,058 healthy European Caucasian women (IL-6 levels were measured in a subgroup of 1,348 women).

RESULTS

In both control and diabetic patients, polymorphisms within an LD block spanning approximately 42 kb were significantly associated with plasma IL-6 levels. A missense variant SNP7 in exon 9 (rs8192284, Asp358Ala) showed the strongest association (P = 0.0005 in control and P = 0.004 in case subjects). The corresponding false-discovery rates, which accounts for multiple testing, were 0.008 and 0.02, respectively. We inferred five common haplotypes to capture 94% allele variance of the LD block using SNP5, -7, -8, -9, and -10. Compared with the most common haplotype 12111 (one codes the common and two codes the minor alleles), haplotypes 11211 [difference in log(IL-6) = -0.11 (95% CI -0.23 to -0.01); P = 0.01] and 21122 (-0.15 [-0.27 to -0.03]; P = 0.01) were associated with significantly lower IL-6 levels (global test, P = 0.01). However, IL6R genotypes were not significantly associated with the risk of type 2 diabetes.

CONCLUSIONS

IL6R genetic variations, especially SNP7 (rs8192284, Asp358Ala), were significantly associated with plasma IL-6 levels but not with diabetes risk in women. The strong associations between IL6R genetic variability and IL-6 concentrations deserve further investigation.

DNA variants, plasma levels and variability of C-reactive protein in myocardial infarction survivors: results from the AIRGENE study

AIMS

C-reactive protein represents the classical acute-phase protein produced in the liver in response to inflammatory stimuli. This study evaluated the association of gene polymorphisms with differences in C-reactive protein concentrations and assessed its intra-individual variability as a marker of individual response.

METHODS AND RESULTS

One thousand and three myocardial infarction (MI) survivors were recruited in six European cities, and C-reactive protein concentrations were measured repeatedly during a 6-month period. We investigated 114 polymorphisms in 13 genes, all involved in the innate inflammatory pathway. We found two polymorphisms within the C-reactive protein (CRP) gene rs1800947 and rs1205, of which the minor alleles were strongly associated with lower levels of C-reactive protein (P < 10(-6)). A haplotype, identified by those two polymorphisms, was associated with the lowest C-reactive protein concentrations (P < 10(-6)). Additionally, the minor alleles of several variants were significantly associated with greater individual variability of C-reactive protein concentrations (P < 10(-3)).

CONCLUSION

The present study investigated the association of polymorphisms with inter- and intra-individual variability of C-reactive protein levels. Two minor alleles of C-reactive protein variants were associated with lower C-reactive protein concentrations. Regarding intra-individual variability, we observed associations with the minor alleles of several variants in selected candidate genes, including the CRP gene itself.

Multiple-polymorphism associations of 7 matrix metalloproteinase and tissue inhibitor metalloproteinase genes with myocardial infarction and angiographic coronary artery disease

BACKGROUND

Single nucleotide polymorphisms (SNPs) in matrix metalloproteinase (MMP) genes may be associated with myocardial infarction (MI) and coronary artery disease (CAD), but studies of multiple MMP genes and their tissue inhibitors (TIMPs) are scarce. Furthermore, differentiation of predictive ability by end point (MI vs CAD) has not been addressed. This study evaluated the association with MI of SNPs in genes encoding MMPs 1, 2, 3, and 9 and TIMPs 1, 2, and 3.

METHODS

Genotypes of patients (N = 5148) with MI (n = 1693) and angiographically defined CAD (> or = 1 lesion of > or = 70% stenosis, n = 1967) were compared with MI-free (n = 3455) and non-CAD patients (n = 1122), respectively. Because of linkage disequilibrium, MMP-1 and MMP-3 SNPs (chromosome 11) were combined, as were the 2 MMP-9 SNPs.

RESULTS

For MI, only MMP-9 group CT/RQ (odds ratio [OR] 1.25, P = .007 vs wild-type CC/RR) had greater MI risk, with TT/QQ having a weak trend (OR 1.43, P = .10). These findings remained (CT/RQ) or were strengthened (TT/QQ) after full adjustment. For CAD, association was found for MMP-1/MMP-3 groups 2G1G/6A6A (OR 1.45, P = .022), 2G1G/6A5A (OR = 1.49, P = .001), 2G1G/5A5A (OR 1.64, P = .003), and 1G1G/5A5A (OR 1.35, P = .035) compared to wild type.

CONCLUSIONS

Composite MMP-9 genotypes but not other SNPs were associated with MI, whereas MMP-1/MMP-3 genotypes were CAD-associated. The largest MMP/TIMP gene study to date, this study suggests care in selection and definition of clinical phenotypes. Furthermore, this suggests that the evaluated SNPs only approximately account for intragenic variation in these genes and that comprehensive evaluation of all variations in these genes should better elucidate associations with MI and CAD phenotypes.