Genotype at a promoter polymorphism of the interleukin-6 gene is associated with baseline levels of plasma C-reactive protein

Personalized nutrition: nutritional genomics as a potential tool for targeted medical nutrition therapy

An emerging goal of medical nutrition therapy is to tailor dietary advice to an individual's genetic profile. In the United States and elsewhere, "nutrigenetic" services are available over the Internet without the direct involvement of a health care professional. Among the genetic variants most commonly assessed by these companies are those found in genes that influence cardiovascular disease risk. However, the interpretation of DNA-based data is complex. The goal of this paper is to carefully examine nutritional genomics as a potential tool for targeted medical nutrition therapy. The approach is to use heart health susceptibility genes and their common genetic variants as the model.

C-Reactive Protein Gene Polymorphisms, C-Reactive Protein Blood Levels, and Cardiovascular Disease Risk

C-reactive protein (CRP), a blood marker of inflammation and a hallmark of the acute-phase response, has been shown to be a powerful and specific predictor of cardiovascular event risk in populations of otherwise healthy persons. Here we review what is known about CRP gene polymorphisms, discuss how these might affect the epidemiology of CRP and our understanding of CRP's contribution to cardiovascular disease, and examine their potential clinical usefulness. Evidence shows that certain subtle variations in the CRP gene sequence, mostly single nucleotide polymorphisms, predictably and strongly influence the blood level of CRP. Some of these variations are associated with clinical correlates of cardiovascular disease. If future studies can establish with certainty that CRP influences cardiovascular biology, then CRP gene profiling could have clinical utility.

Psychobiological mechanisms of exercise dependence

Exercise dependence (ED) is characterised by an obsessive and unhealthy preoccupation with exercise. Previous research has focused largely on identifying behavioural aspects of ED, although the biological mechanisms remain unknown and are under researched. We review various ED hypotheses including affect regulation, anorexia analogue, sympathetic arousal and beta-endorphin. We also present a novel hypothesis pertaining to ED and interleukin (IL)-6, which combines previous hypotheses with literature from the field of psycho-neuroimmunology. We explore the notion that IL-6 provides a link from the periphery to the brain, which may mediate the underlying features of ED. We propose a conceptual model indicating that, in individuals prone to ED, exercise results in a transient reduction in negative affect, but concurrently results in excessive production of IL-6 and the activation of neuroendocrine pathways, which are associated with behavioural and psychological disturbances of exercise withdrawal. Our intention is for this model to serve as a basis for further research in the area of ED, which may eventually lead to the development of successful treatment strategies. Recent developments in methods to reliably assess these biological markers from blood and saliva samples should encourage such research to be undertaken in exercise settings.

Impact of serum levels and gene polymorphism of cytokines on chronic hepatitis C infection

The factors leading to clearance or persistent infection of hepatitis C virus (HCV) were not well defined, and the importance of the host immune response has been highlighted. Therefore, the impact of the serum concentration and genetic polymorphism of several cytokines on the outcome of HCV infection warrant additional study. Enzyme-linked immunosorbent assay was employed to measure serum tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-4, and IL-10 concentrations on 72 hepatitis C patients and 180 controls. Furthermore, the association between single nucleotide polymorphism (SNP) of genes of these cytokines and hepatitis C infection was evaluated by polymerase chain reaction- restriction fragment length polymorphism and statistical analysis. These analyzed SNPs of cytokines included TNF-alpha G238A, TNF-alpha G308A, IL-4 C589T, IL-10 A1082G, IL-10 T819C, and IL-10 A592C. Serum levels of TNF-mu alpha, IL-4, and IL-10 were significantly higher in hepatitis C patients than that of controls (P < 0.001). Furthermore, the distribution of TNF-alpha G308A genotypes and alleles, but not others, was statistically different between patients and controls (P < 0.05). These data suggested the distribution of polymorphism at TNF-alpha G308A may be different between normal subjects and patients with chronic infection of hepatitis C.

C-reactive protein gene polymorphism 1009A>G is associated with serum CRP levels in Chinese men: A TCVGHAGE study

BACKGROUND

Increased concentrations of high-sensitivity CRP (hs-CRP) are associated with increased risk of cardiovascular disease. This increase might be caused by low-grade inflammation, but a number of studies have suggested that serum CRP concentrations are under genetic control. Since the relation between CRP concentration and cardiovascular diseases occurs across ethnicities, we determined whether CRP gene variants affect fasting hs-CRP concentrations in a cohort of Chinese men.

METHODS

High-sensitivity CRP concentrations were measured in 369 Chinese men. Six polymorphisms were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and direct sequencing within the CRP gene: 969T>C, 1009A>G, and a 3-allele polymorphism 1440C>A>T in the 5' UTR (promoter region), 2667G>C in exon 2, and 3872A>G and 5992T>A in the 3' UTR.

RESULTS

In a group of participants (n=328) whose fasting serum hs-CRP concentrations were within the 5th to 95th percentile, we found that the genetic polymorphism 1009A>G was significantly associated with fasting serum hs-CRP concentrations (GG vs. AG or AA genotypes, CRP concentrations 0.072+/-0.062 vs. 0.176+/-0.166 and 0.166+/-0.185 mg/dl, mean+/-S.D., both P=0.023). Furthermore, subjects carrying the 1009G bearing haplotype exhibited the lowest CRP concentrations (P=0.05).

CONCLUSION

The CRP 1009A>G genotypes and associated haplotypes were associated with lower fasting serum hs-CRP concentrations in a group of elderly Chinese men.

A locus on chromosome 10 influences C-reactive protein levels in two independent populations

High sensitivity C-reactive protein (hsCRP) is an independent risk factor for cardiovascular disease, such as stroke or coronary artery disease. Genetic factors influence significantly the inter-individual variability of hsCRP. The aim of this study was to identify genomic regions influencing hsCRP levels. A genome scan was performed in two independent studies of Caucasian populations, namely 513 Western-European families ascertained for myocardial infarction (n = 1,406) and 120 French-Canadian families diagnosed with hypertension (n = 758). In the myocardial infarction families, 31% of the inter-individual variation of hsCRP levels was explained by genetic factors (P = 0.0000015) and loci influencing hsCRP were identified on chromosomes 10 (at 141 cM) and 5 (at 150 cM) with multipoint LOD scores of 3.15 and 2.23, respectively. An additional suggestive signal was detected on chromosome 2 in subset analyses. A similar degree of heritability has been observed in a second independent population of French-Canadian hypertensive families for hsCRP (30%) and linkage results for chromosome 10 were confirmed with maximum LOD score of 2.7. We identified a chromosomal region in two independent populations which influences hsCRP in addition to several unique regions. This provides targets for the identification of genes involved in the regulation of hsCRP and the development and progression of vascular disease, including stroke.

Plasma levels of fibrinogen and C-reactive protein are related to interleukin-6 gene −572C>G polymorphism in subjects with and without hypertension

Hypertension is an important risk factor for cardiovascular diseases. There is increasing evidence suggesting that inflammation is involved in the development of hypertension. Interleukin-6 (IL-6) is an important mediator of inflammatory response and the major regulator of hepatic production of acute phase proteins, such as fibrinogen and C-reactive protein (CRP), which have been associated with hypertension and cardiovascular diseases. Therefore, we studied the association of single nucleotide polymorphism (SNP) in the IL-6 gene (IL6) promoter with plasma levels of fibrinogen, CRP and hypertension. Five hundred and two Hong Kong Chinese subjects (282 normotensives and 220 hypertensives) were recruited. IL-6 gene promoter was examined for polymorphism and the study subjects were genotyped for any SNP identified. The IL6 -572C>G polymorphism (rs1800796) was found with a frequency of 0.23 for the minor G allele. Subjects with the -572G allele had significantly higher plasma fibrinogen (3.06+/-0.57 vs 2.83+/-0.60, P=0.002) and CRP (interquartile range 0.33-1.56 vs 0.12-0.93, P=0.003) levels than those without. The -572C>G polymorphism was found to be an independent predictor of fibrinogen and CRP levels after adjusting for confounding factors. Plasma concentrations of fibrinogen and CRP correlated with systolic blood pressure. However, the -572C/G genotype frequencies did not differ between hypertensive and normotensive subjects, and there was no association between -572C>G polymorphism and blood pressure. Our results provide evidence that there is a clear genetic influence of IL6 -572C>G polymorphism on plasma levels of fibrinogen and CRP, but this polymorphism does not lead to elevated blood pressure.

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

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

n-3 Polyunsaturated fatty acids, inflammation and obesity-related disease

Obese individuals are at increased risk from a range of metabolic diseases, including insulin resistance, dyslipidaemia and hypertension. Adipose tissue is an important endocrine organ, secreting a range of inflammatory mediators, including tumour necrosis factor a and interleukin 6. Circulating concentrations of these cytokines are increased in obesity and may contribute to the pathogenesis of metabolic diseases. The present review considers the evidence linking inflammation and obesity-related disease. The data show that an inflammatory phenotype, measured by serum sialic acid concentration, identifies individuals with insulin resistance, dyslipidaemia and hypertension. Serum sialic acid concentration increases progressively in obese individuals with none, one or multiple features of the metabolic syndrome, independent of BMI. Supplementation with long-chain n-3 polyunsaturated fatty acids has shown anti-inflammatory effects in studies of both healthy populations and in models of chronic inflammatory conditions. The effect on insulin sensitivity has been varied, with both positive and negative effects. This variability may relate to the metabolic characteristics of the study population; individuals with high background inflammation may derive greater benefits from n-3 polyunsaturated fatty acid supplements, suggesting a possible interaction between diet and phenotype. Future research is needed to fully evaluate the role of anti-inflammatory strategies in the dietary management of obesity.

C-reactive protein, an 'intermediate phenotype' for inflammation: human twin studies reveal heritability, association with blood pressure and the metabolic syndrome, and the influence of common polymorphism at catecholaminergic/beta-adrenergic pathway loci

BACKGROUND

C-reactive protein (CRP) both reflects and participates in inflammation, and its circulating concentration marks cardiovascular risk. Here we sought to understand the role of heredity in determining CRP secretion.

METHODS

CRP, as well as multiple facets of the metabolic syndrome, were measured in a series of 229 twins, both monozygotic (MZ) and dizygotic (DZ), to estimate trait heritability (h2). Single nucleotide polymorphism (SNP) genotyping was done at adrenergic pathway loci. Haplotypes were inferred from genotypes by likelihood methods. Association of CRP with hypertension and the metabolic syndrome was studied in a larger series of 732 individuals, including 79 with hypertension.

RESULTS

MZ and DZ twin variance components indicated substantial h2 for CRP, at approximately 56 +/- 7% (P < 0.001). CRP was significantly associated (P < 0.05) with multiple features of the metabolic syndrome in twins, including body mass index (BMI), blood pressure (BP), leptin and lipids. In established hypertension, elevated CRP was associated with increased BP, BMI, insulin, HOMA (index of insulin resistance), leptin, triglycerides and norepinephrine. Twin correlations indicated pleiotropy (shared genetic determination) for CRP with BMI (P = 0.0002), leptin (P < 0.001), triglycerides (P = 0.002) and systolic blood pressure (SBP) (P = 0.042). Approximately 9800 genotypes (43 genetic variants at 17 loci) were scored within catecholaminergic pathways: biosynthetic, receptor and signal transduction. Plasma CRP concentration in twins was predicted by polymorphisms at three loci in physiological series within the catecholamine biosynthetic/beta-adrenergic pathway: TH (tyrosine hydroxylase), ADRB1 (beta1-adrenergic receptor) and ADRB2 (beta2-adrenergic receptor). In the TH promoter, common allelic variation accounted for up to approximately 6.6% of CRP inter-individual variance. At ADRB1, variation at Gly389Arg predicted approximately 2.8% of CRP, while ADRB2 promoter variants T-47C and T-20C also contributed. Particular haplotypes and diplotypes at TH and ADRB1 also predicted CRP, though typically no better than single SNPs alone. Epistasis (gene-by-gene interaction) was demonstrated for particular combinations of TH and ADRB2 alleles, consistent with their actions in a pathway in series. In an illustration of pleiotropy, not only CRP but also plasma triglycerides were predicted by polymorphisms at TH (P = 0.0053) and ADRB2 (P = 0.027).

CONCLUSIONS

CRP secretion is substantially heritable in humans, demonstrating pleiotropy (shared genetic determination) with other features of the metabolic syndrome, such as BMI, triglycerides or BP. Multiple, common genetic variants in the catecholaminergic/beta-adrenergic pathway contribute to CRP, and these variants (especially at TH and ADRB2) seem to interact (epistasis) to influence the trait. The results uncover novel pathophysiological links between the adrenergic system and inflammation, and suggest new strategies to probe the role and actions of inflammation within this setting.

C-Reactive Protein Distribution and Correlates among Men and Women with Chronic Coronary Heart Disease

BACKGROUND

C-reactive protein (CRP) elevated in inflammation is associated with atherosclerotic disease. We describe the distribution of CRP and its association with coronary heart disease (CHD) risk factors in a large CHD patient group.

METHODS

This analysis comprises 2,723 male and 256 female CHD patients, included in the Bezafibrate Infarction Prevention (BIP) study. High sensitive CRP levels were determined in frozen plasma samples.

RESULTS

CRP distribution, was normalized upon log transformation. Levels among women were higher than in men in the entire group (4.4 vs. 3.5 mg/l) and in each age group. Co-morbidities, smoking, lower education level, and use of cardiovascular drugs, were associated with elevated CRP levels in both sexes. The correlation between CRP and body mass index (BMI), insulin and glucose was stronger among women. The explained variability in CRP level was larger in women (20%) compared to men (13%). Among women, BMI explained 10% of CRP variability, whereas the contribution of each variable among men was significantly smaller.

CONCLUSIONS

Among men and women with CHD, CRP level was correlated with traditional risk factors and to a lesser degree to manifestation of CHD. BMI is the main contributor to CRP variability, explained by these factors among women.

Systemic inflammation in COPD: is genetic susceptibility a key factor?

COPD is a multicomponent disease characterized by abnormal inflammatory response of the lungs to noxious particles that is accompanied by systemic effects like weight loss, muscle wasting, reduced functional capacity and impaired health status. A persistent low-grade systemic inflammatory response reflected by enhanced levels of acute phase proteins like C-reactive protein (CRP) and pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha, is present in part of the COPD population. The production of inflammatory proteins is partly genetically determined. Several studies have shown that polymorphisms within genes coding for these inflammatory mediators may modulate systemic inflammatory responses. Among all of these genes, the TNF family (TNF-alpha, lymphotoxin (LT)-alph and their receptors TNF-R55 and TNF-R75), interleukin (IL)-6 and CRP gene polymorphisms are the most prominent candidates. However, large carefully designed studies in well-characterized COPD cohorts are required to unravel the exact role of genetic background in the systemic component of this disease.

The impact of long chain n-3 polyunsaturated fatty acid supplementation on inflammation, insulin sensitivity and CVD risk in a group of overweight women with an inflammatory phenotype

BACKGROUND

Inflammation is strongly related to obesity and the risk of cardiovascular disease (CVD). The metabolic benefits of long chain (LC) n-3 polyunsaturated fatty acid (PUFA) may be attributable to its anti-inflammatory properties.

OBJECTIVE

To investigate whether an individual's habitual inflammatory status influences the impact of a LC n-3 PUFA intervention on CVD risk.

DESIGN

The study was a randomized crossover design. Subjects received LC n-3 PUFA capsules or a placebo for 12 weeks, with 4-week washout between phases. Thirty women, in the top and bottom tertiles of baseline sialic acid concentration, formed raised inflammatory status (top, n = 12) and reference (bottom, n = 18) groups. Baseline data were analysed using one-way anova, differences between treatment phases were calculated at each timepoint and analysed using a random effects model.

RESULTS

At baseline, the raised inflammatory status group had significantly higher body mass index and area under the curve (AUC) insulin than the reference group. With LC n-3 PUFA supplementation, both groups showed significantly higher plasma eicosapentaenoic acid and docosahexaenoic acid at 4 and 12 weeks (p < 0.001), and lower triacylglycerols (4 weeks p < 0.01 and 12 weeks p < 0.05). The difference in AUC insulin between the two treatment phases at 12 weeks was significantly greater in the raised inflammatory status group compared to the reference group (p < 0.05). Inflammatory markers were significantly lower after 12 weeks LC n-3 PUFA supplementation compared to baseline (C-reactive protein p < 0.05 and interleukin-6 p < 0.01), but there was no significant group effect.

CONCLUSIONS

Habitual inflammatory status influences the impact of LC n-3 PUFA supplementation, but it is not clear whether the effect of LC n-3 PUFA on AUC insulin is mediated through inflammatory mechanisms.

Effects of the Interaction between Interleukin-6-634C/G Polymorphism and Smoking on Serum C-Reactive Protein Concentrations

Smoking and interleukin-6 (IL-6) are major factors in inflammation. The aim of this study was to investigate whether or not the IL6 -634C/G polymorphism (rs1800796) and its interaction with smoking influence serum C-reactive protein (CRP) concentrations. The subjects were 347 Japanese male employees of a transit company. CRP and conventional cardiovascular risk factors were evaluated. IL6 -634C/G polymorphisms were genotyped by allelic discrimination using fluorogenic probes and the 5' nuclease assay. The mean values of CRP were significantly higher in current smokers than in nonsmokers after adjustment for age, body mass index (BMI), systolic blood pressure, total cholesterol, log triglycerides, high-density lipoprotein cholesterol (HDL-C), fasting glucose, and drinking habit (p=0.011). Comparison of three genotypes revealed significant interaction between smoking and the IL6 -634C/G genotype manifested by CRP concentrations (p=0.007) after the adjustments cited above. After stratification by smoking status, CRP differed significantly among IL6 -634C/G genotypes groups in nonsmokers (p=0.010, p for trend=0.007), whereas no significant difference was found in current smokers. Comparison between -634C/C and C/G+G/G groups revealed also a significant interaction between smoking and the IL6 -634C/G genotype (p=0.007). These findings suggest that the impact of the -634G allele on CRP elevation is greater in nonsmokers than in current smokers. Since gene-environment interactions have been insufficiently examined, further studies are required to clarify their effect on inflammation, including CRP elevation.

Heritability and expression of C-reactive protein in type 2 diabetes in the Diabetes Heart Study

Elevated C-reactive protein (CRP) levels are associated with both prevalent and incident cardiovascular disease. In this study, familial aggregation was estimated, and we tested for association between serum CRP levels and polymorphisms within the CRP and APOE genes in sib-ships with type 2 diabetes mellitus, a population at increased risk for cardiovascular disease. CRP levels were determined in 461 diabetes-affected subjects from 224 sibships from the Diabetes Heart Study (DHS). Heritability estimates of CRP levels were obtained using variance component models. Genetic influence on serum CRP levels by single nucleotide polymorphisms (SNPs) in the CRP and APOE genes was evaluated by association analysis using mixed models. Subjects were Caucasian American (84%) and African-American (16%), 53% female, and had an average age of 62.2 +/- 9.2 years. The median CRP level was 3.3 mg/L (range 0 to 59.3 mg/L), and estimated heritability for CRP was approximately 40%. Estimates of heritability were significantly greater than zero (P < 0.0001) and relatively constant, despite adjustments for important modifiers (age, sex, ethnicity, diabetes duration, statin-use and anti-inflammatory use) of CRP. There was no significant evidence for association of CRP levels with CRP gene SNPs; however, consistent with previous reports, there was significant evidence of association of CRP levels with polymorphisms within the APOE gene. These data indicate CRP levels are significantly influenced by genetic (and/or environmental) factors that are shared within DHS families. While the APOE locus shows evidence of contributing to CRP levels, no evidence of CRP gene polymorphism association with CRP levels was observed.

Association study of CRP gene polymorphisms with serum CRP level and cardiovascular risk in the NHLBI Family Heart Study

Recent epidemiological studies have indicated that baseline C-reactive protein (CRP) levels may have value in prediction of cardiovascular risk. Using six tag single-nucleotide polymorphisms (SNPs) selected from our complete list of SNPs on the CRP gene, we investigated the association of CRP genotypes with plasma CRP levels and cardiovascular risk in the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study cohort (1,296 Caucasians, 48.5% male, 54.7 ± 12.8 yr old). There was a significant trend toward association of CRP haplotypes with CRP levels ( P = 0.045). SNP analysis indicated a highly significant association of SNP −757 (rs3093059, P = 0.0004) and SNP −286 (rs3091244, P = 0.0065) and a borderline association of SNP −7180 (rs1341665, P = 0.06) with CRP levels. Neither CRP haplotypes nor individual SNP genotypes were associated with intima-media thickness of the common carotid or internal carotid artery or the bifurcation of the carotid arteries. These results indicated a strong impact of local SNPs of the CRP gene on plasma CRP levels, but there was no direct evidence that these genetically controlled CRP elevations by local CRP SNPs contributed to cardiovascular disease phenotypes.

Association between aldosterone production and variation in the 11beta-hydroxylase (CYP11B1) gene

CONTEXT

Variation in the region of chromosome 8 including the genes steroid 11beta-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) influences mineralocorticoid and glucocorticoid metabolism. However, the relative importance of polymorphisms in CYP11B1 and CYP11B2 in determining these phenotypes is unknown.

OBJECTIVE

Our objective was to investigate genetic influences of the CYP11B1 and CYP11B2 genes on mineralocorticoid metabolism.

DESIGN

We measured 24-h urinary excretion of the key metabolites of the principal mineralocorticoids, glucocorticoids and androgens secreted by the adrenal cortex. We genotyped polymorphisms spanning the CYP11B1 and CYP11B2 genes, which together capture all common variations at the locus.

PARTICIPANTS

Participants included 573 members of 105 British Caucasian families ascertained on a hypertensive proband.

MAIN OUTCOME MEASURES

We assessed heritability of urinary tetrahydroaldosterone (THAldo) excretion and association of THAldo excretion with genotype.

RESULTS

The heritability of THAldo excretion was 52% (P < 10(-6)). There was significant association between THAldo and genotype at several of the CYP11B1/B2 polymorphisms. The strongest association was observed at the rs6387 (2803A/G) polymorphism in intron 3 of CYP11B1 (P = 0.0004). Association followed a codominant model with a 21% higher THAldo excretion per G allele. Genotype at rs6387 accounted for 2.1% of the total population variability of THAldo. We found significant association between THAldo excretion and urinary total androgen excretion, urinary tetrahydrodeoxycortisol level, and urinary cortisol metabolites (all P < 0.001).

CONCLUSIONS

Aldosterone synthesis is highly heritable and is affected by genotype at CYP11B1. Our findings support the hypothesis that genetically determined differences in 11-hydroxylation efficiency can have downstream effects on mineralocorticoid synthesis. Such effects may be of relevance to the development of low-renin essential hypertension.

INSIG-2 promoter polymorphism and obesity related phenotypes: association study in 1428 members of 248 families

Background

Obesity is a major public health problem. Body mass index (BMI) is a highly heritable phenotype but robust associations of genetic polymorphisms to BMI or other obesity-related phenotypes have been difficult to establish. Recently a large genetic association study showed evidence for association of the single nucleotide polymorphism (SNP) rs7566605, which lies 10 Kb 5' to the first exon of the insulin-induced gene 2 (INSIG-2), with obesity in several cohorts. We tested this polymorphism for association with body mass related phenotypes in a large family study whose mean BMI was consistent with moderate overweight.

Methods

We studied 1428 members of 248 British Caucasian families who had been ascertained through a proband with hypertension. We measured BMI, waist and hip circumference, and plasma levels of leptin. We genotyped the rs7566605 SNP using a restriction fragment length polymorphism assay, and carried out a family-based association test for quantitative traits related to obesity using the statistical programs MERLIN and QTDT.

Results

We observed no significant association between genotype at rs7566605 and covariate-adjusted (for age, sex, alcohol consumption, smoking and exercise habit) log-transformed BMI, waist measurement, hip measurement, waist-to-hip ratio, or plasma levels of leptin.

Conclusion

There was no association between genotype at rs7566605 and obesity-related phenotypes in this British Caucasian population. These families were in general moderately overweight, few members being severely obese. Our result indicates that this polymorphism has little if any effect on BMI within the normal to moderately overweight range. The effects of this polymorphism on body mass may be restricted to those already predisposed to at least moderate obesity as a result of environmental factors and other predisposing genotypes.

Additive effect of interleukin-6 and C-reactive protein (CRP) single nucleotide polymorphism on serum CRP concentration and other cardiovascular risk factors

BACKGROUND

Serum C-reactive protein (CRP) levels, closely associated with cardiovascular disease (CVD) risk are influenced by CRP or interleukin-6 (IL-6) single nucleotide polymorphism (SNPs). However, it is still controversial. Therefore, we investigated the association of IL-6/CRP SNPs and serum CRP levels or other CVD risk factors in healthy adult Korean men.

METHODS

In healthy adult men (age>or=20 years, n=677), we genotyped IL-6-572C>G and CRP SNPs (-717G>A, 1444C>T, 2147A>G) and measured anthropometric parameters, lipid profile, serum levels of CRP and IL-6 and insulin resistance.

RESULTS

At IL-6-572C>G (n=677), subjects with G/G genotype (n=42) showed higher concentrations of CRP (P=0.027) and IL-6 (P=0.028) as compared with C allele carriers after age-adjustment (C/C: n=371, C/G: n=264). Fasting insulin and homeostatis model assessment insulin resistance (HOMA-IR) were also higher in G/G genotype. However, there were no significant differences in other metabolic biomarkers. Among 677 study subjects, 676 were genotyped at CRP-717G>A (G/G: n=513, G/A: n=150, A/A: n=13), 672 at CRP+1444C>T (C/C: n=580, C/T: n=85, T/T: n=7), and 668 at CRP+2147A>G (A/A: n=273, A/G: n=296, G/G: n=99). There were no significant differences in CRP concentrations and other markers related to CVD risk according to each CRP SNP genotype. However, we could find the additive gene-gene interaction between IL-6-572C>G and CRP SNPs on CRP concentration; subjects with the 'G/G' at IL-6-572 showed the highest CRP levels when they have variant allele at CRP SNPs after adjusted for age, body mass index, cigarette smoking and alcohol drinking (-717G>A: F=7.806, P=0.005; CRP+1444C>T: F=8.398, P=0.004; and CRP+2147A>G: F=7.564, P=0.006, respectively) Particularly, G allele carriers at CRP+2147A>G in subjects with IL-6-572G/G showed highest HOMA-IR (F=9.092, P=0.003).

CONCLUSION

The present data showed that serum CRP levels and other CVD risk factors appeared more influenced by IL-6-572C>G rather than CRP SNPs (-717G>A, 1444C>T, and 2147A>G), however CRP levels and insulin resistance may be additively affected by IL-6-572 and CRP SNP, particularly when subjects with G/G genotype at IL-6-572 have allele variant at CRP SNPs.

Genetic variation is associated with C-reactive protein levels in the Third National Health and Nutrition Examination Survey

BACKGROUND

Increased serum C-reactive protein (CRP) is an independent risk factor for cardiovascular disease. Previous studies have suggested that genetic variation within the CRP gene is associated with serum CRP.

METHODS AND RESULTS

We genotyped CRP genetic variants in 7159 individuals from the Third National Health and Nutrition Examination Survey (NHANES III). NHANES III is American population-based sample linked to hundreds of phenotypes, including CRP; however, the CRP assay used in this survey is not a high-sensitivity CRP assay, and 65% of participants (n=4679) had CRP measurements at or below the level of detection. Despite these limitations, we identified specific CRP single-nucleotide polymorphisms (SNPs) and haplotypes associated with serum CRP levels in the general population. Two variants were associated with increased levels of serum CRP: SNP rs3093058 (in linkage disequilibrium with a CRP promoter SNP rs3093062) in the non-Hispanic black sample and the triallelic promoter SNP rs3091244 in the non-Hispanic black and Mexican American samples. Two other SNPs were associated with decreased levels of serum CRP in either the non-Hispanic black (rs1205 and rs2808630) or Mexican American (rs1205) samples. Three haplotypes inferred from 7 SNPs (ATTGCGA, TTAGCGA, and AAAGAGA) were associated (P < or = 0.01) with increased levels of serum CRP in the non-Hispanic black sample; 2 haplotypes (ATTGCGA and AAAGCGA) were associated (P < 0.05) with increased levels in the Mexican American sample; and 1 haplotype (AAAGCGA) was associated (P < 0.03) with increased levels in the non-Hispanic white sample. Post hoc analysis suggests that the AA genotype of the triallelic SNP rs3091244, after adjustment for covariates, was associated with prevalent coronary heart disease in the non-Hispanic white population sample.

CONCLUSIONS

Genetic variation within CRP is associated with serum CRP levels in the general population and may be associated with prevalent coronary heart disease.

Host cytokine genotype is related to adverse prognosis and systemic inflammation in gastro-oesophageal cancer

BACKGROUND

Systemic inflammation has been linked with reduced survival in cancer, however, the role of the host cytokine genotype versus tumour phenotype in the generation of this response is not clearly established. This study examined the relationship between cytokine polymorphisms (IL-1beta 511, IL-6 174, IL-10 1082, TNFalpha 308 and LTalpha +252) and serum cytokine concentrations, serum CRP concentration and survival duration in patients with gastro-oesophageal malignancy.

METHODS

Two hundred and three newly diagnosed patients with gastric or oesophageal cancer had serum CRP and cytokine concentrations determined by ELISA. SNP genotyping was performed by Taqman allelic discrimination genotyping and compared with the genotype observed in 266 healthy volunteers. Clinico-pathological information was collected prospectively and survival duration was recorded.

RESULTS

Distribution of the cytokine genotypes was similar between patients and controls. The IL-6 174 CC and IL-10 1082 GG genotypes were associated with elevated serum CRP (P = .03, P = .01, respectively; Mann-Whitney U test) and sTNF-R (P = .015, P = .02) concentrations. These genotypes were also associated with reduced survival duration (P = .01, P = .047; log-rank test). TNFalpha AA genotype was also associated with reduced survival duration on univariate (P = .032) and multivariate analysis (P = .006, multivariate model), but not with inflammatory markers. No other cytokine polymorphisms were associated with systemic inflammatory markers or prognosis.

CONCLUSIONS

There is a pro-inflammatory cytokine haplotype (IL-6 CC, IL-10 GG, TNFalpha AA) that is associated with adverse prognosis that may act, at least in part, through an inflammatory mediated mechanism. Determining patients' cytokine haplotype may improve prognostication and allow stratification for intervention studies.

Quantitative trait locus on chromosome 20q13 for plasma levels of C-reactive protein in healthy whites: the HERITAGE Family Study

C-reactive protein (CRP) is a sensitive marker of systemic low-grade inflammation. Increased plasma levels of CRP predict the risk of cardiovascular and metabolic diseases. Although genetic factors account for 30-40% of individual differences in plasma CRP levels, genomic regions contributing to CRP levels remain unknown. We performed a genome-wide linkage scan for plasma CRP levels in healthy whites from the HERITAGE Family Study. CRP was measured with a high-sensitivity assay. Multipoint linkage analyses were performed in 280 sibling pairs with 654 markers using regression and variance components-based methods. Data were adjusted for independent correlates of plasma CRP. We showed the strongest evidence of linkage for plasma CRP levels on chromosome 20q13. Markers which gave suggestive linkages in this region were D20S52 [logarithm of odds (LOD) score 3.18, P = 0.00006], D20S857 (LOD score 2.87, P = 0.00014), D20S869 (LOD score 2.75, P = 0.0002), D20S480 (LOD score 2.59, P = 0.0003), D20S501 (LOD score 2.55, P = 0.0003), D20S840 (LOD score 2.18, P = 0.0008), and D20S876 (LOD score 2.07, P = 0.001). We also detected suggestive linkage on chromosome 5p13 for marker D5S1470 (LOD score 2.23, P = 0.0007). Chromosome 20q13 may contribute to plasma CRP levels in healthy whites. This region contains genes that are important in the inflammatory process and may play a role in the development of chronic inflammatory diseases. The present findings may be useful in the ongoing effort to search for genes contributing to inflammation and to identify individuals at an increased risk of chronic inflammatory diseases.

Lack of association between genetic variation in 9 innate immunity genes and baseline CRP levels

It is well-known that baseline levels of C-reactive protein (CRP) are an independent cardiovascular risk factor. We hypothesized that genetic variation with significant influence on CRP levels might be found in genes of the innate immunity system. We performed a candidate gene association study examining common single nucleotide polymorphisms in 9 innate immunity genes (CARD15, IRAK1, IRAK4, LBP, LY86, MEFV, TLR2, TLR4 and NFKB1) in relation to CRP levels. Seven hundred and seventeen subjects from the Women's Health Study population were studied: 359 and 358 samples with extremely low (<0.2 mg/liter) and high (>5 mg/liter) CRP levels, respectively. SNPs were identified from publicly available resequencing data, using a minor allele frequency threshold of >5% and a linkage disequilibrium (LD)-based strategy (r(2) > 0.8) to select 63 LD-independent markers. One non-synonymous SNP in TLR4 and two non-synonymous SNPs in CARD15, previously associated with atherosclerosis and Crohn's disease, respectively, were also studied. Univariate, haplotype and gene-gene interaction analyses all indicated no significant association with CRP levels. Although this work excludes a significant association of common SNPs in these nine genes with CRP levels, it is possible that rarer alleles in these genes, or variation in other innate immunity genes, could be associated with variation in CRP.

The +1059G/C polymorphism in the C-reactive protein (CRP) gene is associated with involvement of the terminal ileum and decreased serum CRP levels in patients with Crohn's disease

BACKGROUND

Serum C-reactive protein (CRP) levels influence the response to anti-tumour necrosis factor (TNF) therapies.

AIM

To analyse the influence of the +1059G/C CRP polymorphism on CRP serum levels and disease susceptibility in patients with Crohn's disease (CD).

METHODS

Using restriction fragment length polymorphism (RFLP) analysis, genomic DNA from 241 CD patients and 199 unrelated controls was analysed for the +1059G/C substitution in the CRP gene and the common caspase-activation recruitment domain 15 (CARD15) variants.

RESULTS

Homozygous C/C carriers were detected only among CD patients (P = 0.066). Patients with ileal involvement (L1 and L3 phenotype) were found in only 58.4% of patients with the wildtype G/G genotype but in 88.2% of the heterozygous G/C carriers (OR 5.26; 95% CI 1.19-23.92) and four of the five C/C homozygous carriers (80%; OR 4.55; 95% CI 1.64-16.67; P = 0.008 for hetero- and homozygous carriers vs. wildtype) which was independent of the presence of CARD15 variants. Increased CD activity was associated with increased CRP serum levels (P < 0.005). For Crohn's disease activity index (CDAI) < 150, C/C homozygosity for the +1059 G/C polymorphism was associated with significantly lower CRP serum levels (P < 0.01).

CONCLUSIONS

The C allele of the CRP +1059G/C polymorphism is associated with decreased serum CRP levels and increased likelihood of disease involvement of the terminal ileum in CD patients.

Relation between common polymorphisms in genes related to inflammatory response and colorectal cancer

AIM: To investigate the association between common single nucleotide polymorphisms (SNPs) in inflammatory response-related genes such as interleukin (IL)-6, IL-8, tumor necrosis factor α (TNFα), peroxisome proliferators-activated receptor γ (PPARγ), intercellular adhesion molecule-1 (ICAM-1) and the risk of colorectal cancer (CRC) in a group of Greek patients.

METHODS: The study group consisted of 222 CRC patients and 200 healthy controls. Genotyping was performed using allele-specific PCR of PRC-RFLP and the results were confirmed by sequencing. We studied the association of SNPs in the IL-6 (-174G > C), IL-8 (-251T > A), TNFα (-308G > A), ICAM-1 (R241G and K469E), and PPARγ (Pro12Ala) genes and the risk of CRC.

RESULTS: The IL-6 -174G, R241 and K469 alleles of ICAM-1 were associated with increased risk of CRC (OR = 1.77, 95% CI: 1.34-2.34; OR = 1.83, 95% CI: 1.23-2.72; and OR = 1.35, 95% CI: 1.03-1.77 respectively). The IL-8 and TNFα polymorphisms had no effect. Whereas the PPARγ Pro12 genotype was associated with increased risk of disease (OR = 1.78, 95% CI: 1.25-2.49).

CONCLUSION: The association between common SNPs in immunologic response-related genes and CRC is reported in the present study. Apart from shedding light on the mechanisms of malignancy initiation and progression, SNPs may improve appropriate screening for sub-populations at risk.

Genetic and environmental contributions to plasma C-reactive protein and interleukin-6 levels – a study in twins

Elevated baseline levels of acute-phase proteins such as C-reactive protein (CRP) or cytokines like interleukin-6 (IL-6) are known risk factors for atherosclerosis and cardiovascular disease (CVD) events. However, until today, there is only controversial information about the contribution of genetic and environmental factors. Therefore, we performed an open prospective study in 108 monozygotic (MZ) and 60 same-sex dizygotic (DZ) twin pairs to analyse the genetic and environmental contributions to plasma CRP and IL-6 levels. Heritability of IL-6 was 0.61, indicating that plasma IL-6 levels are to a major part influenced by genetic determinants; however, for CRP, heritability was only 0.22, pointing to a moderate genetic influence. Plasma CRP levels were strongly influenced by female gender, older age and especially the body mass index. Our data underline the central role of IL-6 in low-grade inflammation contributing to atherosclerosis and CVD.

Serum C-Reactive Protein Concentration and Genotype in Relation to Ischemic Stroke Subtype

BACKGROUND AND PURPOSE

C-reactive protein (CRP) has evolved as an inflammatory risk marker of cardiovascular disease. Several single-nucleotide polymorphisms at the CRP locus have been found to be associated with CRP levels. The aim of the present study was to investigate CRP levels and genetic variants in etiological subtypes of ischemic stroke.

METHODS

The Sahlgrenska Academy Study on Ischemic Stroke (SAHLSIS) comprises 600 consecutive ischemic stroke cases (18 to 69 years) and 600 matched controls from western Sweden. Stroke subtypes were defined by the TOAST classification. Serum CRP levels were determined by a high-sensitivity immunometric assay.

RESULTS

CRP levels were significantly higher for all ischemic stroke subtypes compared with controls, both in the acute phase and at the 3-month follow-up. After adjustment for traditional risk factors, CRP at follow-up was related to higher odds ratios (ORs) of overall ischemic stroke (OR, 1.25; 95% CI, 1.09 to 1.43) and large-vessel disease (OR, 1.48; 95% CI, 1.09 to 2.00). The CRP -286C>T>A, 1059G>C, and 1444C>T single-nucleotide polymorphisms showed significant associations with CRP levels. However, neither CRP genotypes nor haplotypes showed an association to overall ischemic stroke.

CONCLUSIONS

This is the first large study on CRP in different TOAST subtypes in a young ischemic stroke population. CRP levels differed between etiological subtypes of ischemic stroke both in the acute phase and at the 3-month follow-up. CRP at follow-up was associated with overall ischemic stroke and the large-vessel disease subtype. Genetic variants at the CRP locus were associated with CRP levels, but no association was detected for overall ischemic stroke.

Case-control study in basal cell carcinoma of the skin: single nucleotide polymorphisms in three interleukin promoters pre-analysed in pooled DNA

BACKGROUND

Basal cell carcinoma (BCC) is one of the most common neoplasms in the world. Development of BCC is associated with environmental factors (especially sun exposure) as well as heritable factors.

OBJECTIVES

To analyse three single nucleotide polymorphisms (SNPs) in the promoter regions of interleukin (IL) genes in genomic DNA from 527 cases of BCC and 530 matched controls and to examine if DNA pooling is a useful method on which to base decisions regarding further SNP analysis.

METHODS

The SNPs analysed were IL6-597, IL10-1082 and IL1B-511. The SNPs were first analysed from pooled DNA and afterwards from individual samples. The DNA pools resulted from a division of the samples into cases and controls, female and male, and three age groups. In these pools the allele frequencies were estimated by two methods, real-time polymerase chain reaction with allele-specific primers, and quantitative sequencing.

RESULTS

No significant association was found when the allele frequencies in cases and controls were compared. However, by analysis of the individual genotypes we found SNP IL6-597 G/A to be significantly associated with BCC risk (P =0.007). Hereby the heterozygous genotype 'GA' had a protective effect (odds ratio 0.64, 95% confidence interval 0.49-0.84). No significant association was found for IL10-1082 and IL1B-511.

CONCLUSIONS

The association of SNP IL6-597 with BCC could be found only by individual genotyping, but would have been missed if only data from the pooling analysis had been known.

Inflammatory cytokine gene polymorphisms, nonsteroidal anti-inflammatory drug use, and risk of adenoma polyp recurrence in the polyp prevention trial

BACKGROUND

Pro- and anti-inflammatory cytokine genes may be important in the maintenance and progression of colorectal cancer. It is possible that single-nucleotide polymorphisms in inflammatory genes may play a role in chronic colonic inflammation and development of colorectal adenomas. Furthermore, common variants in cytokine genes may modify the anti-inflammatory effect of nonsteroidal anti-inflammatory drugs (NSAIDs) in the prevention of colorectal cancer.

METHODS

We examined the association between cytokine gene polymorphisms and risk of recurrent adenomas among 1,723 participants in the Polyp Prevention Trial. We used logistic regression to calculate odds ratios (OR) for the association between genotype, NSAID use, and risk of adenoma recurrence.

RESULTS

Cytokine gene polymorphisms were not statistically significantly associated with risk of adenoma recurrence in our study. We observed statistically significant interactions between NSAID use, IL-10 -1082 G>A genotype, and risk of adenoma recurrence (P = 0.01) and multiple adenoma recurrence (P = 0.01). Carriers of the IL-10 -1082 G>A variant allele who were non-NSAID users had a statistically significant decreased risk of multiple adenoma recurrence (OR, 0.43; 95% confidence interval, 0.24-0.77) as well as a nonsignificant 30% decreased risk of any adenoma recurrence. In contrast, NSAID users who were carriers of the IL-10 -1082 G>A variant allele were at an increased risk of any adenoma recurrence (OR, 1.55; 95% confidence interval, 1.00-2.43).

CONCLUSION

These findings suggest that individuals who are carriers of the IL-10 -1082 G>A variant allele may not benefit from the chemoprotective effect of NSAIDs on adenoma polyp recurrence.

Interleukin 6 G−174 C polymorphism and breast cancer risk

Interleukin-6 (IL-6) is a growth factor involved in many processes including carcinogenesis. The C allele of the G-174 C promoter single nucleotide polymorphism (SNP) in the IL-6 gene decreases levels of IL-6 expression and it has been studied in the context of breast cancer progression yielding contradicting results. Furthermore a recent study found that carriers of the C allele were at an increased risk for this disease. We aim to evaluate the association between this variant and breast cancer risk in Caucasian postmenopausal women. Women participating in the Rotterdam Study (N=3822), including 171 patients with breast cancer were genotyped for this polymorphism. In order to assess the relationship between this SNP and breast cancer we carried out a logistic regression in relation to the incidence of breast cancer. The C allele frequency was 41.3% and the genotypes followed Hardy-Weinberg distribution (p=0.3). The logistic regression analysis showed a slight increase of risk for C allele carriers (odds ratio=1.24, 95% CI: 0.8-1.9), compared to non-carriers of this allele. This increased risk was not statistically significant. Our data suggest that the IL-6 G-174 C polymorphism does not seem to play a role in breast cancer risk, although its role as a prognostic factor remains to be studied.

Common genetic vulnerability to depressive symptoms and coronary artery disease: a review and development of candidate genes related to inflammation and serotonin

OBJECTIVE

Although it is well established that depressive symptoms are associated with recurrent cardiac events among cardiac patients and novel cardiac events among participants with no known coronary artery disease (CAD), the nature of this association remains unclear. In this regard, little attention has been paid to the possibility that common genetic vulnerability contributes to both depressive symptoms and CAD. In this paper, we review the existing evidence for common genetic contributions to depression and CAD, primarily using evidence from twin and family studies, followed by a review of two major pathophysiological mechanisms thought to underlie covariation between depressive symptoms and CAD: inflammation and serotonin. We conclude with an overview of select candidate genes within these pathways.

METHODS

Literature review.

RESULTS

In twin studies, both depression and CAD appear heritable. In the only twin study to consider depression and CAD jointly, the correlation across heritabilities was 0.42, suggesting that nearly 20% of variability in depressive symptoms and CAD was attributable to common genetic factors. In addition, although it is plausible that genetic variation related to inflammation and serotonin may be associated with both depression and CAD, genetic variation related to inflammation has been primary examined in relation to CAD, whereas genetic variation in the serotonin system has been primarily examined in relation to depression.

CONCLUSIONS

It appears that the covariation of depressive symptoms and CAD may be attributable, in part, to a common genetic vulnerability. Although several pathways may be involved, genes within the inflammation and serotonin pathways may serve as good candidates for the first steps in identifying genetic variation important for depression, CAD or both.

IL-6 haplotypes, inflammation, and risk for cardiovascular disease in a multiethnic dialysis cohort

It is unknown whether IL-6, a central regulator of inflammation, is a cause of or just a marker of atherosclerosis. Studies of genetic susceptibility to inflammation, however, avoid the potential for reverse causality. Variation in IL6 gene was studied as a predictor of cardiovascular disease (CVD) risk in a cohort of 775 incident dialysis patients, in whom IL-6 levels are elevated. On the basis of published resequencing data on the IL6 gene, a phylogenetic tree with three main branches (clades 1 to 3) was constructed. Two "clade tag" polymorphisms, -174G/C and 1888G/T, and two missense variants, Pro32Ser and Asp162Val, were genotyped. Circulating IL-6 and albumin were measured a median of 5 mo after the start of dialysis. CVD events were ascertained from medical records. During a median follow-up of 2.5 yr, 294 CVD events occurred. The two coding variants, Pro32Ser (present only in black patients, 10% Ser allele) and Asp162Val (present only in white patients, 1% Val), were associated with lower levels of IL-6 and higher levels of albumin. The common variant in the promoter region, -174G/C, was strongly associated with higher CVD risk and weakly with IL-6 levels. Clade 3 (-174C carriers in the absence of 162 Val allele) was associated with higher IL-6 levels (P=0.03) and higher CVD risk (hazard ratio 1.44, P=0.006) after adjustment for covariates. The IL6 gene has functional variants that affect inflammation and risk for CVD among dialysis patients, supporting a causal role for IL6 in CVD.

Lipoprotein(a), lipids and proinflammatory cytokines in patients undergoing major abdominal surgery

Background

The aims were to investigate whether surgical stress can induce a positive or negative lipoprotein(a) acute response, to determine any association with apolipoprotein(a) phenotypes, and to establish whether any such response is dependent on changes in lipids and proinflammatory cytokines. In addition, the impact of interleukin (IL) 6 genetic variability on the cytokine response to surgery was examined.

Methods

This prospective, observational study included 41 patients with cancer referred for abdominal surgery. Preoperative (T0) plasma concentrations of lipoprotein(a), IL-6, tumour necrosis factor α, and serum concentrations of transforming growth factor β1 and lipids, were compared with values obtained 5 h (T1), 24 h (T2) and 5 days (T3) after surgery. Apolipoprotein(a) Kringle IV (KIV)-VNTR (variable-number tandem repeat) and IL-6 − 174 G/C polymorphisms were analysed.

Results

Lipoprotein(a) was found to act as a negative acute-phase reactant (30·0 per cent reduction at T2) (P = 0·009). Surgery had a more profound impact on subjects with low KIV-VNTR. After surgery, lipoprotein(a) correlated significantly with corrected low-density lipoprotein (LDL)-cholesterol (r = 0·408 at T2). IL-6 inversely correlated with lipoprotein(a) (r = −0·321 at T1) and LDL-cholesterol (r = −0·418 at T1). The IL-6 response could be predicted from a combination of the surgical severity and −174 G/C genotype.

Conclusion

Although temporal associations did not indicate causality, these data provide a hypothesis to explain the inverse relationship between lipoprotein(a) and IL-6.

What does minor elevation of C-reactive protein signify?

Reports of the predictive value of minor elevation of serum C-reactive protein (CRP) levels (between 3 and 10 mg/L) for atherosclerotic events have generated considerable interest, as well as a degree of controversy and confusion. CRP concentrations in this range are found in about one third of the American population. To better understand the mechanisms underlying minor elevation of CRP, we have surveyed its reported associations with a variety of states and conditions. It has become clear that even minimal environmental irritants and inflammatory stimuli elicit a minor CRP response. Minor CRP elevation has been found associated with a number of genetic polymorphisms, with membership in different demographic and socioeconomic groups, with a variety of dietary patterns and with many medical conditions that are not apparently inflammatory. Finally, minor CRP elevation bears negative prognostic implications for many conditions, particularly age-related diseases, and predicts mortality in both diseased and apparently healthy individuals. In sum, minor CRP elevation is associated with a great many diverse conditions, some of which are, or may prove to be, causal. Many of these reported associations imply a mild degree of tissue stress or injury, suggesting the hypothesis that the presence of distressed cells, rather than a resulting inflammatory response, is commonly the stimulus for CRP production.

Data-mining analysis suggests an epigenetic pathogenesis for type 2 diabetes

The etiological origin of type 2 diabetes mellitus (T2DM) has long been controversial. The body of literature related to T2DM is vast and varied in focus, making a broad epidemiological perspective difficult, if not impossible. A data-mining approach was used to analyze all electronically available scientific literature, over 12 million Medline records, for “objects” such as genes, diseases, phenotypes, and chemical compounds linked to other objects within the T2DM literature but were not themselves within the T2DM literature. The goal of this analysis was to conduct a comprehensive survey to identify novel factors implicated in the pathology of T2DM by statistically evaluating mutually shared associations. Surprisingly, epigenetic factors were among the highest statistical scores in this analysis, strongly implicating epigenetic changes within the body as causal factors in the pathogenesis of T2DM. Further analysis implicates adipocytes as the potential tissue of origin, and cytokines or cytokine-like genes as the dysregulated factor(s) responsible for the T2DM phenotype. The analysis provides a wealth of literature supporting this hypothesis, which—if true—represents an important paradigm shift for researchers studying the pathogenesis of T2DM.

Association of interferon-gamma +874A polymorphism with reduced long-term inflammatory response in haemodialysis patients

BACKGROUND

We have studied the effects of interferon (IFN)-gamma allelic variations on expression levels of pro- and anti-inflammatory cytokines and on long-term inflammatory status in haemodialysis patients.

METHODS

Genotyping was performed in 123 patients for single nucleotide polymorphisms in the first intron of the IFN-gamma gene (+874 T/A). They were prospectively followed for 2 years. Cytokine mRNA levels in whole blood cells (detected by real time (RT)-PCR technique) and serum C-reactive protein (CRP) concentrations were compared in patient groups with different IFN-gamma genotypes. Serum CRP was evaluated every month and inflammatory state was defined as percent of abnormal values (above 5 mg/l) over total determinations. Of the total, 102 patients survived and completed 24+/-1 monthly CRP determinations. The IFN-gamma +/-874 A/A, 'low-producer' genotype was associated with decreased (P<0.05) mRNA levels of IFN-gamma and of interleukin-6 and with a lower (P<0.05) frequency of CRP elevation (37+/-6%) than the +/-874 A/T and T/T, 'intermediate and high-producer' genotypes (59+/-6%, and 60+/-5%, respectively). The mRNA levels of tumor necrosis factor-alpha, IL-10 and of transforming growth factor-beta1 were not different in the three groups of patients. Pooled analysis in deceased (10+/-3 monthly CRP determinations) and survived patients confirmed the results obtained in the patients who completed the follow-up period.

CONCLUSIONS

The 'low-producer' IFN-gamma +874 A/A genotype was associated with a preventive effect on long-term CRP elevation in haemodialysis patients possibly mediated by decreased gene expression of IFN-gamma and IL-6.

Interleukin 6 −174 G/C Promoter Polymorphism and Risk of Coronary Heart Disease

OBJECTIVE

Inflammation plays a pivotal role in the pathogenesis of atherosclerosis. Interleukin (IL) 6 has many inflammatory functions, and the IL-6 -174 G/C promoter polymorphism appears to influence IL-6 levels. Findings of previous studies on the relation between this polymorphism and risk of cardiovascular diseases are inconsistent. We investigated this polymorphism in relation to risk of coronary heart disease (CHD) in a population-based study and meta-analysis.

METHODS AND RESULTS

Participants (6434) of the Rotterdam Study were genotyped. Analyses on the relation between genotype and CHD were performed using Cox proportional hazards tests, and the association between genotype and plasma levels of IL-6 and C-reactive protein was investigated. All of the analyses were adjusted for age, sex, and common cardiovascular risk factors. A meta-analysis was performed, using a random effects model. No association between genotype and risk of CHD was observed. The polymorphism was not associated with IL-6 levels, but the C-allele was associated with higher C-reactive protein levels (P<0.01). Our meta-analysis did not show a significant association between the genotype and risk of CHD.

CONCLUSIONS

We conclude that the polymorphism is not a suitable genetic marker for increased risk of CHD in subjects > or =55 years of age.

Interleukin-1 and interleukin-6 gene polymorphisms and the risk of breast cancer in caucasian women

PURPOSE

Genetic polymorphisms of cytokine-encoding genes are known to predispose to malignant disease. Interleukin (IL)-1 and IL-6 are crucially involved in breast carcinogenesis. Whether polymorphisms of the genes encoding IL-1 (IL1) and IL-6 (IL6) also influence breast cancer risk is unknown.

EXPERIMENTAL DESIGN

In the present case-control study, we ascertained three polymorphisms of the IL1 gene cluster [-889 C/T polymorphism of the IL1alpha gene (IL1A), -511 C/T polymorphism of the IL1beta promoter (IL1B promoter), a polymorphism of IL1beta exon 5 (IL1B exon 5)], an 86-bp repeat in intron 2 of the IL1 receptor antagonist gene (IL1RN), and the -174 G/C polymorphism of the IL6 gene (IL6) in 269 patients with breast cancer and 227 healthy controls using PCR and pyrosequencing.

RESULTS

Polymorphisms within the IL1 gene cluster and the respective haplotypes were not associated with the presence and the phenotype of breast cancer. The IL6 polymorphism was significantly associated with breast cancer. Odds ratios for women with one or two high-risk alleles versus women homozygous for the low-risk allele were 1.5 (95% confidence interval, 1.04-2.3; P = 0.04) and 2.0 (95% confidence interval, 1.1-3.6; P = 0.02), respectively. No association was ascertained between presence of the IL6 polymorphism and various clinicopathologic variables.

CONCLUSIONS

Although polymorphisms within the IL1 gene cluster do not seem to influence breast cancer risk or phenotype, presence of the -174C IL6 allele increases the risk of breast cancer in Caucasian women in a dose-dependent fashion.

Association of CommonCRPGene Variants with CRP Levels and Cardiovascular Events

C-reactive protein (CRP) is a well-documented marker of atherosclerotic cardiovascular disease risk. We resequenced CRP to identify a comprehensive set of common SNP variants, then studied and replicated their association with baseline CRP level among apparently healthy subjects in the Women's Health Study (WHS; n = 717), Pravastatin Inflammation/CRP Evaluation trial (PRINCE; n = 1,110) and Physicians' Health Study (PHS; n = 509) cohorts. The minor alleles of four SNPs were consistently associated in all three cohorts with higher CRP, while the minor alleles of two SNPs were associated with lower CRP (p < 0.05 for each). Single marker and haplotype analysis in all three cohorts were consistent with functional roles for the 5'-flanking triallelic SNP -286C>T>A and the 3'-UTR SNP 1846G>A. None of the SNPs associated with higher CRP were associated with risk of incident myocardial infarction (MI) or ischemic stroke in a prospective, nested case-control study design from the PHS cohort (610 case-control pairs). One SNP, -717A>G, was unrelated to CRP levels but associated with decreased risk of MI (p = 0.001). Taken together, these data imply significant interactions between both genetic and environmental contributions to the increased CRP levels that predict a greater risk of future atherothrombotic events in epidemiological studies.

Effect of genetic variability on the inflammatory response to periodontal infection

AIM

To review the association between genetic variability and the inflammatory response induced by periodontal infection.

MATERIAL AND METHODS

A search of MEDLINE-PubMed was performed from January 2000 up to and including March 2005. The search included all types of publications, published in English without other limitations. The following search terms were used: "cytokine polymorphism", "gene polymorphism", "periodontitis", "gingivitis", "inflammation" and "host-response". The papers resulting from the above search were used as an additional source for relevant articles.

RESULTS

Genetic variability was examined for the correlation to clinical indicators of inflammation such as bleeding on probing (BOP), gingival inflammation, cytokine in gingival crevicular fluid (GCF) and cytokine production by inflammatory cells. According to the current literature, most of the studies found no association between genetic variability and BOP, gingival inflammation or cytokine concentrations in the GCF. These studies were hampered by inappropriate study designs and the use of inflammatory parameters as secondary rather than primary outcome variables. The data suggest that the production of inflammatory mediators by inflammatory cells may be affected by different genetic traits but further studies are needed in order to establish this association.

CONCLUSIONS

To date, there is no clear correlation between any of the gene polymorphisms and clinical indicators of inflammation. The powering of studies to reveal associations between single or multiple nucleotide polymorphisms and inflammatory parameters will need to involve a much larger number of subjects than were used in the past. The available data (including the interleukin-1 composite genotype) do not currently support the utility of such tests in the diagnosis and prognostic assessments of periodontal diseases.

Genotype at the −174G/C Polymorphism of the Interleukin-6 Gene Is Associated With Common Carotid Artery Intimal-Medial Thickness

BACKGROUND AND PURPOSE

Studies in unrelated individuals have produced conflicting findings concerning the putative association between the interleukin-6 (IL-6) -174G/C polymorphism and carotid intimal-medial thickness (IMT). We have used a family-based genetic association design to assess the heritability of carotid IMT and to investigate the hypothesized association of carotid IMT with the IL-6 to -174G/C polymorphism.

METHODS

We studied 854 members of 224 white British families. The heritability of carotid IMT was determined using Multipoint Engine for Rapid Likelihood Inference. Genetic association analyses were carried out using ANOVA and family-based tests of association implemented in Quantitative Transmission Disequilibrium Test. A meta-analysis of previous studies of the association was conducted to place our result in context.

RESULTS

The heritability of carotid IMT was 24%. Under a recessive model (GG+GC versus CC), there was significant evidence of association between IL-6 to the -174G/C genotype and adjusted log(e) maximal carotid IMT (F=5.469; P=0.02). Family-based analyses using Quantitative Transmission Disequilibrium Test showed no evidence of population stratification as a cause of the observed association (chi2(1)=0.469; P=0.4934). The CC genotype was associated with a 4.8% increase in maximal carotid IMT and accounted for 0.6% of the observed variation in the trait, which is equivalent to 2.5% of the heritable component. A meta-analysis of the present and 2 previous large studies, which enrolled a total of 2930 subjects, confirmed the recessive effect of the C allele on carotid IMT (P=0.0014).

CONCLUSIONS

The genotype at the IL-6 to -174G/C polymorphism is associated with common carotid artery IMT, although the size of the genetic effect is small.

Physical activity and modulation of systemic low-level inflammation

It has been recognized for some time that cardiovascular disease and type 2 diabetes are, to a major extent, inflammatory disorders associated with an environment characterized by a sedentary lifestyle together with abundant intakes of calories. Systemic low-level inflammation is suggested to be a cause as well as consequence of pathological processes with local tumor necrosis factor alpha production as an important biological driver. It is hypothesized that physical inactivity contributes to an enhanced proinflammatory burden independently of obesity, as regular muscle contractions mediate signals with myokines/cytokines as important messengers, which suppress proinflammatory activity at distant sites as well as within skeletal muscle. Muscle-derived interleukin (IL)-6 is considered to possess a central role in anti-inflammatory activities and health beneficial effects in relation to physical exercise. It is discussed how this fits the consistent observation that enhanced plasma levels of IL-6 represent a strong risk marker in chronic disorders associated with systemic low-level inflammation and all-cause mortality.

Epistatic effect of C-reactive protein (CRP) single nucleotide polymorphism (SNP) +1059 and interleukin-1B SNP +3954 on CRP concentration in healthy male blood donors

Baseline C-reactive protein (CRP) concentrations are indicative of persons prone to cardiovascular diseases and are about 40-50% heritable. We have previously shown that interleukin (IL)-1B +3954 allele T is associated with lower CRP concentration. In this study, we aimed to examine the effect of this polymorphism together with the CRP +1059 gene polymorphism on baseline CRP concentrations, and genotyped 336 healthy blood donors for CRP +1059 (G-->C) and IL-1B +3954 (C-->T) polymorphisms. In men, the carriers of the CRP +1059 C-allele had significantly lower CRP values than GG homozygotes (0.66 versus 0.43 mg l(-1), up to -35%, P = 0.009). No significant difference was found in women. When the data were stratified for both of these polymorphisms in men, CRP +1059 GG homozygotes had low CRP concentrations only if they were allele-T carriers of IL-1B +3954 simultaneously (0.93 versus 0.50 mg l(-1), P = 0.013). Genotype CRP +1059 GG/IL-1B +3954 CC was associated with an almost 3-fold risk of a higher baseline CRP value [odds ratio (OR) 2.84 (CI 1.03-6.07)]. Thus, both IL-1B +3954 (C-->T) and CRP +1059 (G-->C) polymorphisms influence baseline CRP values and act independently of each other in male subjects. These polymorphisms might be predictive markers of persons prone to cardiovascular diseases.

Evaluation of C-Reactive Protein Measurement for Assessing the Risk and Prognosis in Ischemic Stroke

Background and Purpose— Several studies have shown, in different populations, that modest elevation of plasma C-reactive protein (CRP) in the range seen in apparently healthy individuals is a strong predictor of future vascular events. Elevated plasma CRP concentrations are also associated with an increased risk of cerebrovascular events and an increased risk of fatal and nonfatal cardiovascular events in ischemic stroke patients. These epidemiological and clinical observations suggest that determination of plasma CRP concentrations could be used as an adjunct for risk assessment in primary and secondary prevention of cerebrovascular disease and be of prognostic value. The aim of this review is to summarize the evidence for CRP as an independent predictor of cerebrovascular events in at-risk individuals and ischemic stroke patients and to consider its usefulness in evaluating prognosis after stroke.

Summary of Review— CRP fulfils most of the requirements of a new risk and prognostic predictor, but several issues await further confirmation and clarification before this marker can be included in the routine evaluation of stroke patients and subjects at risk for cerebrovascular disease. Potentially important associations have been established between elevated plasma CRP concentrations and increased efficacy of established therapies, particularly lipid-lowering therapy with statins.

Conclusion— At present, there is not sufficient evidence to recommend measurement of CRP in the routine evaluation of cerebrovascular disease risk in primary prevention, because there is insufficient evidence as to whether early detection, or intervention based on detection, improves health outcomes, although shared risk of cardiovascular disease indicates this may be of value. In secondary prevention of stroke, elevated CRP adds to existing prognostic markers, but it remains to be established whether specific therapeutic options can be derived from this.

Genetic determination of acute phase reactant levels: the strong heart study

OBJECTIVE

C-reactive protein (CRP), fibrinogen and plasminogen activating inhibitor-1 (PAI-1) are acute phase reactants (APRs); and high levels are indicative of physiologic inflammatory responses. Basal (non-stimulated) APR levels have also been shown to predict atherosclerotic complications in a number of populations. We sought to determine the relative contributions of genetic and environmental factors influencing basal serum levels of APRs.

METHODS

This study used univariate quantitative genetic analyses to partition the phenotypic variance of these APRs into their additive genetic and environmental components using maximum likelihood variance decomposition methods. Bivariate analyses were done to detect genetic correlation between APRs. The computer program SOLAR was used to perform these analyses.

RESULTS

The Strong Heart Study (SHS) includes information on approximately 1,294 American Indian relative pairs. The proportion of variance due to environmental and acquired covariates affecting these APRs was modest, ranging from 16-20%. The proportion of variance due to genetic factors (heritability) ranged from 24-46%. In addition, there were significant genetic correlations between CRP/fibrinogen (rho=0.41 +/- 0.12) and CRP/PAI-1 (rho=0.46 +/- 0.19); but not between fibrinogen/PAI-1.

CONCLUSION

In the SHS cohort, the levels of APRs are determined to a substantial degree by genetic influences, and CRP shares common genetic determinants with fibrinogen and PAI-1.