The interleukin-6 receptor as a target for prevention of coronary heart disease: a mendelian randomisation analysis

Association between serum interleukin-6 concentration and mortality in patients with coronary artery disease

Objectives. To evaluate whether serum interleukin-6 (IL-6) is associated with increased risk of mortality in coronary artery disease (CAD) patients. Methods. We performed a prospective cohort study of 718 CAD patients from the Guangzhou Cardiovascular Disease Cohort (GCDC) study. Multivariable-adjusted Cox proportional hazards regression analyses were used to examine the association between serum IL-6 with all-cause and cardiovascular mortality. Results. During the 1663 person-years of followup, the cumulative all-cause mortality and cardiovascular mortality were 6.5% (n = 47) and 3.3% (n = 24), respectively. The mean length of followup was 2.32 ± 0.81 years. In the multivariable analyses, a one-SD increment in log-transformed serum IL-6 was positively associated with an increased risk of all-cause and cardiovascular mortality, with hazard ratios (HR) of 2.93 (95% CI, 2.11–4.08) and 2.04 (95% CI, 1.34–3.68) within the patients combined and 2.98 (95% CI, 2.12–4.18) and 3.10 (95% CI, 1.98–4.85) within males, respectively. Patients in the highest serum IL-6 tertile versus the lowest tertile were at higher risk of all-cause and cardiovascular mortality, with HR of 17.12 (95% CI 3.11–71.76) and 8.68 (95% CI, 1.88–37.51), respectively. Conclusions. In hospitalized patients with CAD, serum IL-6 is significantly associated with all-cause and cardiovascular mortality.

Pro-atherogenic lipid changes and decreased hepatic LDL receptor expression by tocilizumab in rheumatoid arthritis

OBJECTIVES

Blocking the interleukin-6 pathway by tocilizumab (TCZ) has been associated with changes in the lipoprotein profile, which could adversely impact cardiovascular (CV) risk in patients with rheumatoid arthritis (RA). In the present study, we addressed the effect of TCZ on lipoproteins in both fasting and non-fasting state in RA patients and tested the effect of TCZ on LDL receptor (LDLr) expression in vitro.

METHODS

Twenty patients with active RA and an inadequate response to TNF blockers received monthly TCZ intravenously. On week 0, 1 and 6 blood was drawn before and after an oral fat load, the lipid profiles and HDL antioxidative capacity were measured. Effects of TCZ on LDLr expression in transfected HepG2 cells were subjected.

RESULTS

After 6 weeks of TCZ, total cholesterol increased by 22% (4.8 ± 0.9 to 5.9 ± 1.3 mmol/L; p < 0.001), LDLc by 22% (3.0 ± 0.6 to 3.6 ± 0.8 mmol/L; p < 0.001) and HDLc by 17% (1.4 ± 0.4 to 1.7 ± 0.7 mmol/L; p < 0.016). Fasting triglycerides (TG) increased by 48% (1.0 ± 0.4 to 1.4 ± 0.8 mmol/L; p = 0.011), whereas postprandial incremental area under the curve TG increased by 62% (p = 0.002). Lipid changes were unrelated to the change in disease activity or inflammatory markers. No difference in HDL antioxidative capacity was found. In vitro, LDLr expression in cultured liver cells was significantly decreased following TCZ incubation (P < 0.001).

CONCLUSIONS

TCZ adversely impacts on both LDLc as well as fasting and postprandial TG in patients with RA. The changes in hepatic LDLr expression following TCZ imply that adverse lipid changes may be a direct hepatic effect of TCZ. The net effect of TCZ on CV-morbidity has to be confirmed in future clinical trials.

Functional IL6R 358Ala allele impairs classical IL-6 receptor signaling and influences risk of diverse inflammatory diseases

Inflammation, which is directly regulated by interleukin-6 (IL-6) signaling, is implicated in the etiology of several chronic diseases. Although a common, non-synonymous variant in the IL-6 receptor gene (IL6R Asp358Ala; rs2228145 A>C) is associated with the risk of several common diseases, with the 358Ala allele conferring protection from coronary heart disease (CHD), rheumatoid arthritis (RA), atrial fibrillation (AF), abdominal aortic aneurysm (AAA), and increased susceptibility to asthma, the variant's effect on IL-6 signaling is not known. Here we provide evidence for the association of this non-synonymous variant with the risk of type 1 diabetes (T1D) in two independent populations and confirm that rs2228145 is the major determinant of the concentration of circulating soluble IL-6R (sIL-6R) levels (34.6% increase in sIL-6R per copy of the minor allele 358Ala; rs2228145 [C]). To further investigate the molecular mechanism of this variant, we analyzed expression of IL-6R in peripheral blood mononuclear cells (PBMCs) in 128 volunteers from the Cambridge BioResource. We demonstrate that, although 358Ala increases transcription of the soluble IL6R isoform (P = 8.3×10⁻²²) and not the membrane-bound isoform, 358Ala reduces surface expression of IL-6R on CD4+ T cells and monocytes (up to 28% reduction per allele; P≤5.6×10⁻²²). Importantly, reduced expression of membrane-bound IL-6R resulted in impaired IL-6 responsiveness, as measured by decreased phosphorylation of the transcription factors STAT3 and STAT1 following stimulation with IL-6 (P≤5.2×10⁻⁷). Our findings elucidate the regulation of IL-6 signaling by IL-6R, which is causally relevant to several complex diseases, identify mechanisms for new approaches to target the IL-6/IL-6R axis, and anticipate differences in treatment response to IL-6 therapies based on this common IL6R variant.

Interleukin-6 (IL-6) is a complex cytokine, which plays a critical role in the regulation of inflammatory responses. Genetic variation in the IL-6 receptor gene is associated with the risk of several human diseases with an inflammatory component, including coronary heart disease, rheumatoid arthritis, and asthma. A common non-synonymous single nucleotide polymorphism in this gene (Asp358Ala) has been suggested to be the causal variant in this region by affecting the circulatory concentrations of soluble IL-6R (sIL-6R). In this study we extend the genetic association of this variant to type 1 diabetes and provide evidence that this variant exerts its functional mechanism by regulating the balance between sIL-6R (generated through cleavage of the surface receptor and by alternative splicing of a soluble IL6R isoform) and membrane-bound IL-6R. These data show for the first time that the minor allele of this non-synonymous variant (Ala358) directly controls the surface levels of IL-6R on individual immune cells and that these differences in protein levels translate into a functional impairment in IL-6R signaling. These findings may have implications for clinical trials targeting inflammatory mechanisms involving IL-6R signaling and may provide tools for identifying patients with specific benefit from therapeutic intervention in the IL-6R signaling pathway.

IL-6 polymorphisms: a useful genetic tool for inflammation research?

In 1998, we described a novel polymorphism in the promoter (G>C, rs1800795) of the IL-6 (IL6) gene. The common allele, G, exhibited higher transcriptional activity in gene reporter assays and was associated with higher serum IL-6 levels in a small cohort of healthy subjects. We explored the ethnic distribution of these alleles and found significant differences among people of mixed European descent, Africans, and Gujarati Asians. Disease association was established in a cohort of 92 children of mixed European descent from the United Kingdom with systemic juvenile idiopathic arthritis (sJIA), with the GG genotype being significantly increased in sJIA cases compared with that in 383 controls, especially in those under 6 years old (P = 0.01). This polymorphism has since been used as a functional variant to explore the role of elevated IL-6 levels in many common disease states, confirming the key causal role of IL-6 in human health and disease.

Gene-centric analysis identifies variants associated with interleukin-6 levels and shared pathways with other inflammation markers

BACKGROUND- Inflammatory cytokine interleukin-6 (IL-6), a possible risk factor for coronary heart disease, has an estimated heritability of >60%, but to date few genetic variants influencing IL-6 levels are known. METHODS AND RESULTS- We used the ITMAT-Broad-Care (IBC) HumanCVD disease BeadChip in the Whitehall II study (N=4911) and British Women's Heart and Health Study (N=3445) to identify single-nucleotide polymorphisms associated with circulating IL-6 levels. Twenty-two single-nucleotide polymorphisms from 7 loci (IL6R/TDRD10, HLA-DRB1, BUD13, SEZ6L, IL1RN, TRIB3, and ABO) were associated with IL-6 (P<10(-5)), although none were associated with the IL6 gene itself. With the exception of TRIB3, all loci have been previously reported in genome-wide association studies for autoimmune and cardiovascular diseases. Fourteen single-nucleotide polymorphisms in the IL6R region in high-linkage disequilibrium (r(2)>0.9) with a nonsynonymous variant, rs2228145, were also associated with IL-6 and C-reactive protein concentration (P<10(-5)). An IL-6-specific weighted allele score explained 2% of the variance of log IL-6 levels (P=2.4410(-22)) in Whitehall II and 1% (P=1.910(-8)) in British Women's Heart and Health Studies. CONCLUSIONS- Multiple common genetic variants of modest effect influence IL-6 concentration. Several loci contain single-nucleotide polymorphisms, exhibiting overlapping associations with autoimmune and cardiovascular disorders and other circulating biomarkers. Genetic variants associated with IL-6 provide important tools for probing the causal relevance of IL-6 signaling in a range of cardiometabolic diseases.

Genetic determinant for amino acid metabolites and changes in body weight and insulin resistance in response to weight-loss diets: the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial

BACKGROUND

Circulating branched-chain amino acids and aromatic amino acids were recently related to insulin resistance and diabetes mellitus in prospective cohorts. We tested the effects of a genetic determinant of branched-chain amino acid/aromatic amino acid ratio on changes in body weight and insulin resistance in a 2-year diet intervention trial.

METHODS AND RESULTS

We genotyped the branched-chain amino acid/aromatic amino acid ratio-associated variant rs1440581 near the PPM1K gene in 734 overweight or obese adults who were assigned to 1 of 4 diets varying in macronutrient content. At 6 months, dietary fat significantly modified genetic effects on changes in weight, fasting insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) after adjustment for the confounders (all P for interaction ≤0.006). Further adjustment for weight change did not appreciably change the interactions for fasting insulin and HOMA-IR. In the high-fat diet group, the C allele was related to less weight loss and smaller decreases in serum insulin and HOMA-IR (all P ≤ 0.02 in an additive pattern), whereas an opposite genotype effect on changes in insulin and HOMA-IR was observed in the low-fat diet group (P=0.02 and P=0.04, respectively). At 2 years, the gene-diet interactions remained significant for weight loss (P=0.008) but became null for changes in serum insulin and HOMA-IR resulting from weight regain.

CONCLUSIONS

Individuals carrying the C allele of the branched-chain amino acid/aromatic amino acid ratio-associated variant rs1440581 may benefit less in weight loss and improvement of insulin sensitivity than those without this allele when undertaking an energy-restricted high-fat diet.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00072995.

Systemic inflammation is associated with differential gene expression and airway neutrophilia in asthma

Systemic inflammation is reported to be associated with neutrophilic airway inflammation in asthma, but mechanisms underlying this finding are not well understood. This study aimed to examine the molecular mechanisms of the airway neutrophilia that are associated with systemic inflammation in asthma. Fifty stable nonsmoking adults with asthma had plasma high sensitivity C-reactive protein (hsCRP) and interleukin 6 (IL-6) assayed. Subjects with an elevation of both hsCRP and IL-6 were grouped as asthmatics with systemic inflammation, and those with both hsCRP and IL-6 within the normal ranges were grouped as asthmatics without systemic inflammation. Clinical characteristics and sputum inflammatory cell counts were compared between the two groups. Gene expression profiles from sputum were analyzed and altered expression of four genes (CCL8, IL8RA, SELL, and PI3) was confirmed using quantitative PCR. Asthmatics with systemic inflammation (n=18, 36%) had a higher BMI, greater history of cigarette smoking, lower FVC% predicted, and increased sputum neutrophils compared to those without systemic inflammation (n=16, 32%). Microarray analysis identified 449 genes that were significantly altered in sputum between the two groups. Altered genes were involved in IL-1, TNF-α/nuclear factor-κB, and Kit receptor pathways, and were related to innate immune response, defense and inflammatory response, in particular neutrophilic inflammation. Systemic inflammation was associated with airway neutrophilia in asthma, and was related to a group of differentially expressed genes in the lung involving multiple cytokine pathways. Our findings suggest that targeting systemic inflammation might provide a novel therapeutic strategy for neutrophilic asthma.

Antibodies to citrullinated peptides and risk of coronary heart disease

OBJECTIVE

Increased cardiovascular risk has been associated with high levels of serum antibodies to citrullinated proteins (ACPA) in patients with rheumatoid arthritis (RA). Citrullination is part of many chronic inflammatory processes and we therefore investigated whether ACPA might be associated with coronary artery disease, in the absence of RA.

METHODS

To maximize the potential predictive value of this retrospective study we included sera from a cohort of 3052 healthy male individuals, subsequently followed for the development of coronary artery disease, and documented for other disease risk factors. With each case event (myocardial infarction; n = 144), 2 matched controls were assigned.

RESULTS

We found 10.4% of cases were ACPA positive compared to 3.8% of controls (odds ratio (95% CI) = 3.26 (1.36-7.80), p = 0.008), remaining significant after adjustment for classical risk factors including smoking and CRP (4.23 (1.22-14.61) p = 0.02).

CONCLUSION

The genesis and fine specificity of ACPA in patients with atherosclerosis, in the absence of Rheumatoid arthritis, may prove worthy of further investigation.

Anti-cytokine therapies in T1D: Concepts and strategies

Therapeutic targeting of proinflammatory cytokines is clinically beneficial in several autoimmune disorders. Several of these cytokines are directly implicated in the pathogenesis of type 1 diabetes, suggesting opportunities for design of clinical trials in type 1 diabetes that incorporate selective cytokine blockade as a component of preventative or interventional immunotherapy. The rationale and status of inhibitory therapy directed against IL-1, TNF, IL-12, IL-23, and IL-6 are discussed, towards a goal of using cytokine inhibition as a therapeutic platform to establish an in vivo milieu suitable for modulating the immune response in T1D.

Soluble Glycoprotein 130 Predicts Fatal Outcomes in Chronic Heart Failure

Background—

Glycoprotein 130 (gp130) is the common signal-transducing receptor subunit of the interleukin-6 (IL-6) family, which may be involved in the progression of heart failure (HF). We hypothesized that soluble gp130 would provide prognostic information beyond that of IL-6 in a population with HF from the Controlled Rosuvastatin Multinational Trial in Heart Failure (CORONA).

Methods and Results—

The associations of soluble gp130 and IL-6 with morbidity, mortality, and mode of death were assessed by immunoassays in a subset of 1452 patients enrolled in the CORONA trial, which included patients with HF, aged ≥60 years, in New York Heart Association classes II to IV, who had ischemic heart disease and a reduced left ventricular ejection fraction. In multivariable analyses, including C-reactive protein, IL-6, troponin T, and N-terminal pro-B-type natriuretic peptide, elevated soluble gp130 (fifth quintile versus all lower quintiles) was associated with all-cause mortality (hazard ratio, 1.47 [1.11–1.93]; P =0.006), cardiovascular mortality (hazard ratio, 1.38 [1.01–1.87]; P =0.042), and death from worsening HF (hazard ratio, 1.85 [1.09–3.14]; P =0.002), but not with the primary end point (composite of death from cardiovascular causes, nonfatal myocardial infarction, and nonfatal stroke; hazard ratio, 1.12 [0.84–1.50]; P =0.44). Plasma IL-6 was not associated with outcomes in multivariable analyses.

Conclusions—

Marked elevations in soluble gp130 are associated with total and cardiovascular mortality, as well as deaths from worsening HF, in elderly patients with HF of ischemic cause

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00206310.

Closing the loop on inflammation and atherothrombosis: why perform the CIRT and CANTOS trials?

Inflammation contributes to all phases of the atherothrombotic process, patients with elevated inflammatory biomarkers such as high-sensitivity C-reactive protein (hsCRP) have increased cardiovascular risk, and recent work directly implicates the interleukin-1 (IL-1) and interleukin-6 (IL-6) pathways in atherogenesis. Yet, it remains unknown whether targeted inhibition of inflammation will reduce cardiovascular event rates. To address directly this fundamental hypothesis, our research group has initiated two large-scale, randomized, placebo-controlled trials using targeted anti-inflammatory agents for the secondary prevention of myocardial infarction. The first trial, the Cardiovascular Inflammation Reduction Trial (CIRT), has been funded by the NHLBI and will evaluate whether low-dose methotrexate (target dose, 20 mg/wk) as compared to placebo will reduce major vascular events among a group of post-myocardial infarction patients with either diabetes or metabolic syndrome, groups known to have high risk on the basis of a persistent pro-inflammatory response. CIRT is based, in part, on observational evidence of reduced vascular event rates among those treated with methotrexate in the setting of rheumatoid arthritis or psoriatic arthritis and on the ability of methotrexate to reduce TNF, IL-6, and CRP levels. The second trial, the Canakinumab Anti-Inflammatory Thrombosis Outcomes Study (CANTOS), will evaluate whether interleukin-1β (IL-1β) inhibition as compared to placebo can reduce rates of recurrent myocardial infarction, stroke, and cardiovascular death among stable coronary artery disease patients who remain at high vascular risk due to persistent elevations of hsCRP (_2 mg/L) despite contemporary secondary prevention strategies. Canakinumab is a human monoclonal antibody that selectively neutralizes IL-1β, a pro-inflammatory cytokine that plays multiple roles in the atherothrombotic process and that undergoes activation by the NLRP3 inflammasome, a process promoted by cholesterol crystals that in turn leads directly to increased production of IL-1 and IL-6. Together, CIRT and CANTOS will enroll more than 25,000 patients worldwide and provide a fundamental test of the inflammatory hypothesis of atherothrombosis.

Effects of Interleukin-1β Inhibition With Canakinumab on Hemoglobin A1c, Lipids, C-Reactive Protein, Interleukin-6, and Fibrinogen

Background—

To test formally the inflammatory hypothesis of atherothrombosis, an agent is needed that reduces inflammatory biomarkers such as C-reactive protein, interleukin-6, and fibrinogen but that does not have major effects on lipid pathways associated with disease progression.

Methods and Results—

We conducted a double-blind, multinational phase IIb trial of 556 men and women with well-controlled diabetes mellitus and high cardiovascular risk who were randomly allocated to subcutaneous placebo or to subcutaneous canakinumab at doses of 5, 15, 50, or 150 mg monthly and followed over 4 months. Compared with placebo, canakinumab had modest but nonsignificant effects on the change in hemoglobin A1c, glucose, and insulin levels. No effects were seen for low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, or non–high-density lipoprotein cholesterol, although triglyceride levels increased ≈10% in the 50-mg ( P =0.02) and 150-mg ( P =0.03) groups. By contrast, the median reductions in C-reactive protein at 4 months were 36.4%, 53.0%, 64.6%, and 58.7% for the 5-, 15-, 50-, and 150-mg canakinumab doses, respectively, compared with 4.7% for placebo (all P values ≤0.02). Similarly, the median reductions in interleukin-6 at 4 months across the canakinumab dose range tested were 23.9%, 32.5%, 47.9%, and 44.5%, respectively, compared with 2.9% for placebo (all P ≤0.008), and the median reductions in fibrinogen at 4 months were 4.9%, 11.7%, 18.5%, and 14.8%, respectively, compared with 0.4% for placebo (all P values ≤0.0001). Effects were observed in women and men. Clinical adverse events were similar in the canakinumab and placebo groups.

Conclusions—

Canakinumab, a human monoclonal antibody that neutralizes interleukin-1β, significantly reduces inflammation without major effect on low-density lipoprotein cholesterol or high-density lipoprotein cholesterol. These phase II trial data support the use of canakinumab as a potential therapeutic method to test directly the inflammatory hypothesis of atherosclerosis.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00900146.

Novel anti-inflammatory strategies in atherosclerosis

PURPOSE OF REVIEW

Inflammation has been widely acknowledged to contribute throughout all stages of atherogenesis. However, these recent advances in our understanding have not been translated into clinical practice in which the mainstay of treatment is still lipid-targeted therapy. This review provides an overview of promising anti-inflammatory therapies in atherosclerosis, and discusses potential drawbacks and clinical benefits.

RECENT FINDINGS

Immunosuppressive drugs are likely to beneficially affect atherogenesis. Several novel anti-inflammatory targets have been scrutinized, of which some have reached clinical development stage, such as cytokine targets interleukin-1 and interleukin-6, CCR2 antagonist, selective phospholipase, and leukotriene inhibitors. Novel imaging modalities such as MRI and PET-computed tomography provide valuable surrogate inflammatory endpoints for risk stratification and testing anti-inflammatory agents in cardiovascular randomized trials.

SUMMARY

Anti-inflammatory therapies hold great promise in cardiovascular prevention regimens; however, atherosclerosis is a chronic disease, and systemic long-term use of anti-inflammatory agents carries the risk of complications arising from immunosuppression. In order to successfully add immunosuppressive drugs to our routine armament, we need to identify high-risk patients who benefit from anti-inflammatory treatment, increase our insight into the inflammatory pathogenesis of atherogenesis, and find safe and effective compounds capable of directly suppressing plaque inflammation.

High-density genetic mapping identifies new susceptibility loci for rheumatoid arthritis

Using the Immunochip custom SNP array, which was designed for dense genotyping of 186 loci identified through genome-wide association studies (GWAS), we analyzed 11,475 individuals with rheumatoid arthritis (cases) of European ancestry and 15,870 controls for 129,464 markers. We combined these data in a meta-analysis with GWAS data from additional independent cases (n = 2,363) and controls (n = 17,872). We identified 14 new susceptibility loci, 9 of which were associated with rheumatoid arthritis overall and five of which were specifically associated with disease that was positive for anticitrullinated peptide antibodies, bringing the number of confirmed rheumatoid arthritis risk loci in individuals of European ancestry to 46. We refined the peak of association to a single gene for 19 loci, identified secondary independent effects at 6 loci and identified association to low-frequency variants at 4 loci. Bioinformatic analyses generated strong hypotheses for the causal SNP at seven loci. This study illustrates the advantages of dense SNP mapping analysis to inform subsequent functional investigations.

An MBPhD programme in the UK: the UCL experience

Traditionally, clinician scientists in the UK have been trained by a sequence of medical school, junior hospital posts, MRCP and research leading to a PhD. Thereafter they undertake a mixture of more senior middle-grade jobs leading to senior or lecturer consultant posts and beyond. Experience in the USA has shown how it is possible for young doctors to complete a PhD successfully while still at medical school, giving the graduate a combined MBBS and PhD qualification earlier in their career. UCL instituted such an 'MBPhD' scheme 18 years ago. The first graduates are now attaining chairs. Here, we review the experience of such a course in the UK context.

Mendelian randomization: how genetics is pushing the boundaries of epidemiology to identify new causes of heart disease

The past 10 years have seen a remarkable revolution in the genetics of cardiovascular (CV) disease. Although much work remains to bring these discoveries to the bedside, genetics has opened up remarkable possibilities in understanding the causes of CV disease through a relatively novel study design known as "Mendelian randomization." Akin to a randomized trial, Mendelian randomization is a genetic study design that takes advantage of the "randomization" of genetic information at birth to evaluate a potential causal relationship between a genetically determined biomarker and an outcome. By providing evidence for causal relationships, Mendelian randomization can improve our understanding of fundamental mechanisms in human disease, potentially accelerate the identification of bona fide drug targets, and ultimately improve the care of patients with CV disease. This review describes the concept and design of Mendelian randomization genetic studies, discusses their strengths and weaknesses, and presents recent examples of Mendelian randomization studies in the CV literature that have helped clarify the causal role of selected biomarkers in CV medicine.

Association between interleukin-6 levels and first-ever cerebrovascular events in patients with vascular risk factors

OBJECTIVE

The objective of this study was to examine the association of inflammatory markers with risk of first-ever cerebrovascular events (CVEs), while simultaneously evaluating subclinical vascular disease.

METHODS AND RESULTS

We enrolled 464 outpatients who had vascular risk factors without any preexisting cardiovascular disease. We examined the presence of silent lacunar infarction (SLI) by magnetic resonance imaging; carotid intima-media thickness by ultrasound; and measured high-sensitivity C-reactive protein, interleukin (IL)-6, and IL-18 at baseline, and assessed their associations with CVEs using Cox proportional hazards models of 4.8±2.6 years follow-up. We further calculated measures of reclassification and discrimination. In age- and sex-adjusted analysis, IL-6, but neither high-sensitivity C-reactive protein nor IL-18, was associated with CVEs. The association remained significant after adjustment for conventional risk factors, intima-media thickness, and SLI (hazard ratios: 1.80, per 1-SD increase in log IL-6, P=0.03). Compared with the patients with below median IL-6 without SLI, those with above median IL-6 and SLI had a higher risk of CVEs (hazard ratios: 4.14, P=0.0014). The combination of IL-6 and SLI resulted in the net reclassification improvement of 14.3% (P=0.04), and the integrated discrimination improvement gain of 2.1% (P=0.05).

CONCLUSIONS

IL-6 levels were independently associated with CVEs and could improve reclassification in those with SLI.

Cohort profile: the English longitudinal study of ageing

The English Longitudinal Study of Ageing (ELSA) is a panel study of a representative cohort of men and women living in England aged ≥50 years. It was designed as a sister study to the Health and Retirement Study in the USA and is multidisciplinary in orientation, involving the collection of economic, social, psychological, cognitive, health, biological and genetic data. The study commenced in 2002, and the sample has been followed up every 2 years. Data are collected using computer-assisted personal interviews and self-completion questionnaires, with additional nurse visits for the assessment of biomarkers every 4 years. The original sample consisted of 11 391 members ranging in age from 50 to 100 years. ELSA is harmonized with ageing studies in other countries to facilitate international comparisons, and is linked to financial and health registry data. The data set is openly available to researchers and analysts soon after collection (http://www.esds.ac.uk/longitudinal/access/elsa/l5050.asp).

IL-6 trans-signaling via the soluble IL-6 receptor: importance for the pro-inflammatory activities of IL-6

Interleukin-6 (IL-6) is a cytokine with many activities. It has functions in the regulation of the immune system and the nervous system. Furthermore, IL-6 is involved in liver regeneration and in the metabolic control of the body. On target cells, IL-6 binds to an 80 kDa IL-6 receptor (IL-6R). The complex of IL-6 and IL-6R associates with a second protein, gp130, which thereupon dimerizes and initiates intracellular signaling. Whereas gp130 is expressed on all cells, IL-6R is only present on few cells in the body including hepatocytes and some leukocytes. Cells, which do not express IL-6R cannot respond to the cytokine, since gp130 alone has no measurable affinity for IL-6. Interestingly, a soluble form of IL-6R (sIL-6R) comprising the extracellular portion of the receptor can bind IL-6 with a similar affinity as the membrane bound IL-6R. The complex of IL-6 and sIL-6R can bind to gp130 on cells, which do not express the IL-6R, and which are unresponsive to IL-6. This process has been called trans-signaling. Here I will review published evidence that IL-6 trans-signaling is pro-inflammatory whereas classic IL-6 signaling via the membrane bound IL-6R is needed for regenerative or anti-inflammatory activities of the cytokine. Furthermore, the detailed knowledge of IL-6 biology has important consequences for therapeutic strategies aimed at the blockade of the cytokine IL-6.

Targeting interleukin-6: all the way to treat autoimmune and inflammatory diseases

Interleukin (IL)-6, a cytokine featuring redundancy and pleiotropic activity, contributes to host defense against acute environmental stress, while dysregulated persistent IL-6 production has been demonstrated to play a pathological role in various autoimmune and chronic inflammatory diseases. Targeting IL-6 is thus a rational approach to the treatment of these diseases. Indeed, clinical trials of tocilizumab, a humanized anti-IL-6 receptor antibody have verified its efficacy and tolerable safety for patients with rheumatoid arthritis, Castleman's disease and systemic juvenile idiopathic arthritis, resulting in approval of this innovative biologic for treatment of these diseases. Moreover, a considerable number of case reports and pilot studies of off-label use of tocilizumab point to the beneficial effects of tocilizumab for a variety of other phenotypically different autoimmune and chronic inflammatory diseases. Elucidation of the source of IL-6 and of mechanisms through which IL-6 production is dysregulated can thus be expected to lead to clarification of the pathogenesis of various diseases.

Association of two variants in the interleukin-6 receptor gene and premature coronary heart disease in a Chinese Han population

Two novel single nucleotide polymorphisms (SNPs; rs7529229 and rs2228145) in the interleukin-6 receptor (IL6R) gene have recently been associated with coronary heart disease (CHD) in a European population. We sought to replicate this finding and to investigate associations of these two SNPs with the severity and clinical phenotypes of premature CHD in a Chinese Han population. A total of 418 patients were studied, including 187 cases with coronary stenosis ≥50 % or acute myocardial infarction (males < 55 years and females < 65 years) and 231 controls without documented CHD. A ligase detection reaction was performed to detect rs7529229 and rs2228145. There were no differences between the controls and premature CHD groups in the frequencies for the three genotypes and alleles of rs7529229 and rs2228145 (all P > 0.05), nor did they differ between the two groups when grouped by gender (all P > 0.05). There were also no associations between these two SNPs and the severity of coronary lesions or clinical phenotypes of premature CHD (all P > 0.05). Our results do not support an association between rs7529229 or rs2228145 with premature CHD in the Chinese Han population. Further studies are warranted to elucidate the role of these two SNPs in the development of atherosclerosis and CHD.

Genome-wide association and population genetic analysis of C-reactive protein in African American and Hispanic American women

C-reactive protein (CRP) is a systemic inflammation marker that predicts future cardiovascular risk. CRP levels are higher in African Americans and Hispanic Americans than in European Americans, but the genetic determinants of CRP in these admixed United States minority populations are largely unknown. We performed genome-wide association studies (GWASs) of 8,280 African American (AA) and 3,548 Hispanic American (HA) postmenopausal women from the Women's Health Initiative SNP Health Association Resource. We discovered and validated a CRP-associated variant of triggering receptors expressed by myeloid cells 2 (TREM2) in chromosomal region 6p21 (p = 10(-10)). The TREM2 variant associated with higher CRP is common in Africa but rare in other ancestral populations. In AA women, the CRP region in 1q23 contained a strong admixture association signal (p = 10(-17)), which appears to be related to several independent CRP-associated alleles; the strongest of these is present only in African ancestral populations and is associated with higher CRP. Of the other genomic loci previously associated with CRP through GWASs of European populations, most loci (LEPR, IL1RN, IL6R, GCKR, NLRP3, HNF1A, HNF4A, and APOC1) showed consistent patterns of association with CRP in AA and HA women. In summary, we have identified a common TREM2 variant associated with CRP in United States minority populations. The genetic architecture underlying the CRP phenotype in AA women is complex and involves genetic variants shared across populations, as well as variants specific to populations of African descent.

Physical activity and inflammatory markers over 10 years: follow-up in men and women from the Whitehall II cohort study

BACKGROUND

Inflammatory processes are putative mechanisms underlying the cardioprotective effects of physical activity. An inverse association between physical activity and inflammation has been demonstrated, but no long-term prospective data are available. We therefore examined the association between physical activity and inflammatory markers over a 10-year follow-up period.

METHODS AND RESULTS

Participants were 4289 men and women (mean age, 49.2 years) from the Whitehall II cohort study. Self-reported physical activity and inflammatory markers (serum high-sensitivity C-reactive protein and interleukin-6) were measured at baseline (1991) and follow-up (2002). Forty-nine percent of the participants adhered to standard physical activity recommendations for cardiovascular health (2.5 h/wk moderate to vigorous physical activity) across all assessments. Physically active participants at baseline had lower C-reactive protein and interleukin-6 levels, and this difference remained stable over time. Compared with participants who rarely adhered to physical activity guidelines over the 10-year follow-up, the high-adherence group displayed lower log(e) C-reactive protein (β=-0.07; 95% confidence interval, -0.12 to -0.02) and log(e) interleukin-6 (β=-0.07; 95% confidence interval, -0.10 to -0.03) at follow-up after adjustment for a range of covariates. Compared with participants who remained stable, those who reported an increase in physical activity of at least 2.5 h/wk displayed lower log(e) C-reactive protein (β coefficient=-0.05; 95% confidence interval, -0.10 to -0.001) and log(e) interleukin-6 (β coefficient=-0.06; 95% confidence interval, -0.09 to -0.03) at follow-up.

CONCLUSIONS

Regular physical activity is associated with lower markers of inflammation over 10 years of follow-up and thus may be important in preventing the proinflammatory state seen with aging.

Does interleukin-6 link explain the link between tumour necrosis, local and systemic inflammatory responses and outcome in patients with colorectal cancer?

Cancer-associated inflammation has been identified as a key determinant of disease progression and survival in colorectal cancer. In particular, it has been consistently reported that both the local and systemic inflammatory responses play an important role in determining outcome in colorectal cancer. Given the importance of cancer-associated inflammation, up-regulation or attenuation of these respective inflammatory responses may be important for progression and survival in colorectal cancer. Recent work has focused on the inter-relationships between the tumour and these key inflammatory processes. In particular, tumour necrosis has been reported to be associated with decreased local inflammatory infiltrate and with elevated markers of systemic inflammation in colorectal cancer and has been proposed as a potential link between the systemic and local inflammatory responses. Thus there is increasing interest in the potential biochemical mediators of this link. In this review we examine the evidence for IL-6 in the natural history of colorectal cancer and its relationship with tumour necrosis and the local and systemic inflammatory responses. There is now good evidence that tumour concentrations of IL-6 have been directly associated with increased necrosis, proliferation, differentiation and vascular invasion, while circulating concentrations of IL-6 are directly associated with T-stage, CRP concentrations and poorer survival. Also, interleukin-6 and down-stream pathways, such as the JAK/STAT pathway, have emerged as important factors in the modulation of cancer-associated inflammation. Therefore, IL-6 has emerged as a key mediator of the relationship between tumour necrosis, local and systemic inflammatory responses and outcome in patients with colorectal cancer.

JAK and STAT signaling molecules in immunoregulation and immune-mediated disease

The discovery of the Janus kinase (JAK)-signal transducer and activator of transcripton (STAT) signaling pathway, a landmark in cell biology, provided a simple mechanism for gene regulation that dramatically advanced our understanding of the action of hormones, interferons, colony-stimulating factors, and interleukins. As we learn more about the complexities of immune responses, new insights into the functions of this pathway continue to be revealed, aided by technology that permits genome-wide views. As we celebrate the 20(th) anniversary of the discovery of this paradigm in cell signaling, it is particularly edifying to see how this knowledge has rapidly been translated to human immune disease. Not only have genome-wide association studies demonstrated that this pathway is highly relevant to human autoimmunity, but targeting JAKs is now a reality in immune-mediated disease.

Stress and cardiovascular disease

The physiological reaction to psychological stress, involving the hypothalamic-pituitary-adrenocortical and sympatho-adrenomedullary axes, is well characterized, but its link to cardiovascular disease risk is not well understood. Epidemiological data show that chronic stress predicts the occurrence of coronary heart disease (CHD). Employees who experience work-related stress and individuals who are socially isolated or lonely have an increased risk of a first CHD event. In addition, short-term emotional stress can act as a trigger of cardiac events among individuals with advanced atherosclerosis. A stress-specific coronary syndrome, known as transient left ventricular apical ballooning cardiomyopathy or stress (Takotsubo) cardiomyopathy, also exists. Among patients with CHD, acute psychological stress has been shown to induce transient myocardial ischemia and long-term stress can increase the risk of recurrent CHD events and mortality. Applications of the 'stress concept' (the understanding of stress as a risk factor and the use of stress management) in the clinical settings have been relatively limited, although the importance of stress management is highlighted in European guidelines for cardiovascular disease prevention.