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

Association between carbohydrate quality and inflammatory markers: systematic review of observational and interventional studies

BACKGROUND

Chronic low-grade inflammation is a likely intermediary between quality of carbohydrate and chronic disease risk.

OBJECTIVE

We conducted a systematic literature search to evaluate the relevance of carbohydrate quality on inflammatory markers in observational and intervention studies.

DESIGN

MEDLINE, EMBASE, and the Cochrane Library were searched for studies on associations between glycemic index (GI), glycemic load (GL), dietary fiber or fiber supplements or whole grain intake, and high-sensitivity C-reactive protein (hsCRP) or interleukin 6 (IL-6). Included studies had to be conducted on adults (healthy, overweight, with type 2 diabetes or metabolic syndrome features, but without inflammatory disease) with ≥20 participants and a 3-wk duration.

RESULTS

In total, 22 of the 60 studies that met our inclusion criteria examined GI/GL: 5 of 9 observational studies reported lower concentrations of hsCRP or IL-6 among persons with a lower dietary GI/GL; 3 of 13 intervention studies showed significant antiinflammatory effects of a low-GI/GL diet, and 4 further studies suggested beneficial effects (trends or effects in a subgroup). For fiber intake, 13 of 16 observational studies reported an inverse relation with hsCRP or IL-6, but only 1 of 11 intervention studies showed a significant antiinflammatory effect of fiber intake, and a further trial reported a beneficial trend. For whole-grain intake, 6 of 7 observational studies observed an inverse association with inflammatory markers, but only 1 of 7 intervention studies reported significant antiinflammatory effects, 1 further study was suggestive (in a subgroup) of such, and another study found an adverse effect (trend only).

CONCLUSIONS

Evidence from intervention studies for antiinflammatory benefits is less consistent for higher-fiber or whole-grain diets than for low-GI/GL diets. Benefits of higher fiber and whole-grain intakes suggested by observational studies may reflect confounding.

Mendelian randomization in health research: using appropriate genetic variants and avoiding biased estimates

Mendelian randomization methods, which use genetic variants as instrumental variables for exposures of interest to overcome problems of confounding and reverse causality, are becoming widespread for assessing causal relationships in epidemiological studies. The main purpose of this paper is to demonstrate how results can be biased if researchers select genetic variants on the basis of their association with the exposure in their own dataset, as often happens in candidate gene analyses. This can lead to estimates that indicate apparent "causal" relationships, despite there being no true effect of the exposure. In addition, we discuss the potential bias in estimates of magnitudes of effect from Mendelian randomization analyses when the measured exposure is a poor proxy for the true underlying exposure. We illustrate these points with specific reference to tobacco research.

RVX-208, an inducer of ApoA-I in humans, is a BET bromodomain antagonist

Increased synthesis of Apolipoprotein A-I (ApoA-I) and HDL is believed to provide a new approach to treating atherosclerosis through the stimulation of reverse cholesterol transport. RVX-208 increases the production of ApoA-I in hepatocytes in vitro, and in vivo in monkeys and humans, which results in increased HDL-C, but the molecular target was not previously reported. Using binding assays and X-ray crystallography, we now show that RVX-208 selectively binds to bromodomains of the BET (Bromodomain and Extra Terminal) family, competing for a site bound by the endogenous ligand, acetylated lysine, and that this accounts for its pharmacological activity. siRNA experiments further suggest that induction of ApoA-I mRNA is mediated by BET family member BRD4. These data indicate that RVX-208 increases ApoA-I production through an epigenetic mechanism and suggests that BET inhibition may be a promising new approach to the treatment of atherosclerosis.

Effect of interleukin-6 receptor blockade on surrogates of vascular risk in rheumatoid arthritis: MEASURE, a randomised, placebo-controlled study

Objectives

The interleukin-6 receptor (IL-6R) blocker tocilizumab (TCZ) reduces inflammatory disease activity in rheumatoid arthritis (RA) but elevates lipid concentrations in some patients. We aimed to characterise the impact of IL-6R inhibition on established and novel risk factors in active RA.

Methods

Randomised, multicentre, two-part, phase III trial (24-week double-blind, 80-week open-label), MEASURE, evaluated lipid and lipoprotein levels, high-density lipoprotein (HDL) particle composition, markers of coagulation, thrombosis and vascular function by pulse wave velocity (PWV) in 132 patients with RA who received TCZ or placebo.

Results

Median total-cholesterol, low-density lipoprotein-cholesterol (LDL-C) and triglyceride levels increased in TCZ versus placebo recipients by week 12 (12.6% vs 1.7%, 28.1% vs 2.2%, 10.6% vs −1.9%, respectively; all p<0.01). There were no significant differences in mean small LDL, mean oxidised LDL or total HDL-C concentrations. However, HDL-associated serum amyloid A content decreased in TCZ recipients. TCZ also induced reductions (>30%) in secretory phospholipase A2-IIA, lipoprotein(a), fibrinogen and D-dimers and elevation of paraoxonase (all p<0.0001 vs placebo). The ApoB/ApoA1 ratio remained stable over time in both groups. PWV decreases were greater with placebo than TCZ at 12 weeks (adjusted mean difference 0.79 m/s (95% CI 0.22 to 1.35; p=0.0067)).

Conclusions

These data provide the first detailed evidence for the modulation of lipoprotein particles and other surrogates of vascular risk with IL-6R inhibition. When compared with placebo, TCZ induced elevations in LDL-C but altered HDL particles towards an anti-inflammatory composition and favourably modified most, but not all, measured vascular risk surrogates. The net effect of such changes for cardiovascular risk requires determination.

Metalloproteinases and their natural inhibitors in inflammation and immunity

Over the past 50 years, steady growth in the field of metalloproteinase biology has shown that the degradation of extracellular matrix components represents only a fraction of the functions performed by these enzymes and has highlighted their fundamental roles in immunity. Metalloproteinases regulate aspects of immune cell development, effector function, migration and ligand-receptor interactions. They carry out ectodomain shedding of cytokines and their cognate receptors. Together with their endogenous inhibitors TIMPs (tissue inhibitor of metalloproteinases), these enzymes regulate signalling downstream of the tumour necrosis factor receptor and the interleukin-6 receptor, as well as that downstream of the epidermal growth factor receptor and Notch, which are all pertinent for inflammatory responses. This Review discusses the metalloproteinase family as a crucial component in immune cell development and function.

Effects of 6 months of abatacept treatment on aortic stiffness in patients with rheumatoid arthritis

BACKGROUND

Systemic inflammation plays an important role in the increased cardiac risk observed in rheumatoid arthritis (RA). Effective control of inflammation and disease activity may be of benefit in reducing cardiovascular risk in RA patients.

OBJECTIVE

Our study was conducted in patients with active RA to investigate the effects of 24-week abatacept treatment on aortic stiffness measured by pulse wave velocity (PWV).

RESULTS

The study included 21 patients, of whom 17 were females, with a mean age of 65.2±13.7 years. Ten patients had positive rheumatoid factors, 16 positive anti-citrullinated protein antibodies, and 19 presented an erosive form of RA. Sixteen patients were nonresponders to anti-tumor necrosis factor-alpha treatments. After 6 months of abatacept treatment, there was a significant increase in PWV levels (9.8±2.9 versus 8.5±3.9 m/second; P=0.02). A nonsignificant increase in total cholesterol and low-density lipoprotein cholesterol was observed. There was also a significant increase in high-density lipoprotein cholesterol levels, which led to a nonsignificant decrease in atherogenic index. The improvement in disease activity was significant, and there was a decrease of systemic inflammatory parameters, but without reaching statistical significancy. Changes in PWV were significantly correlated with changes in Disease Activity Score on 28 joints based on erythrocyte sedimentation rate (r=0.46; P=0.035) and in high-density lipoprotein cholesterol (r=-0.38; P=0.046). No correlation was observed with changes in C-reactive protein and in other parameters of lipid profile or in steroid dose.

CONCLUSION

The worsening of aortic stiffness found after 6 months of abatacept therapy might be due to an insufficient decrease in systemic inflammation.

Interleukin-6 receptor pathways in abdominal aortic aneurysm

METHODS

We conducted a systematic review and meta-analysis of studies reporting circulating IL-6 in AAA, and new investigations of the association between a common non-synonymous functional variant (Asp358Ala) in the IL-6R gene (IL6R) and AAA, followed the analysis of the variant both in vitro and in vivo. Inflammation may play a role in the development of abdominal aortic aneurysms (AAA). Interleukin-6 (IL-6) signalling through its receptor (IL-6R) is one pathway that could be exploited pharmacologically. We investigated this using a Mendelian randomization approach.

RESULTS

Up to October 2011, we identified seven studies (869 cases, 851 controls). Meta-analysis demonstrated that AAA cases had higher levels of IL-6 than controls [standardized mean difference (SMD) = 0.46 SD, 95% CI = 0.25-0.66, I(2) = 70%, P = 1.1 × 10-5 random effects]. Meta-analysis of five studies (4524 cases/15 710 controls) demonstrated that rs7529229 (which tags the non-synonymous variant Asp358Ala, rs2228145) was associated with a lower risk of AAA, per Ala358 allele odds ratio 0.84, 95% CI: 0.80-0.89, I(2) = 0%, P = 2.7 × 10-11). In vitro analyses in lymphoblastoid cell lines demonstrated a reduction in the expression of downstream targets (STAT3, MYC and ICAM1) in response to IL-6 stimulation in Ala358 carriers.

CONCLUSIONS

A Mendelian randomization approach provides robust evidence that signalling via the IL-6R is likely to be a causal pathway in AAA. Drugs that inhibit IL-6R may play a role in AAA management.

Role of maca (Lepidium meyenii) consumption on serum interleukin-6 levels and health status in populations living in the Peruvian Central Andes over 4000 m of altitude

Lepidium meyenii (Maca) is a plant that grows at over 4,000 m above sea level in the central Peruvian Andes. The hypocotyls of this plant are traditionally consumed for their nutritional and medicinal properties. The aim of this study was to determine the health status based on a health related quality of life (HRQL) questionnaire (SF-20) and serum levels of interleukin 6 (IL-6) in subjects that are maca consumers. For this, a cross-sectional study was designed to be performed in 50 subjects from Junin (4,100 m): 27 subjects were maca consumers and 23 were non-consumers. The SF-20 survey is used to obtain a summary measure of health status. The stand up from a chair and sit down (SUCSD) test (to assess lower-extremity function), hemoglobin measurement, blood pressure, sexual hormone levels, serum IL-6 levels and the score of chronic mountain sickness (CMS) were evaluated. Testosterone/estradiol ratio (P <0.05), IL-6 (P < 0.05) and CMS score were lower, whereas the health status score was higher, in maca consumers when compared to non-consumers (P < 0.01). A greater proportion of maca consumers successfully completed the SUCSD test compared to non-consumers (P < 0.01), showing a significant association with lower values of serum IL-6 (P < 0.05). In conclusion, consumption of maca was associated with low serum IL-6 levels and in turn with better health status scores in the SF-20 survey and low chronic mountain sickness scores.

Taking up physical activity in later life and healthy ageing: the English longitudinal study of ageing

Background

Physical activity is associated with improved overall health in those people who survive to older ages, otherwise conceptualised as healthy ageing. Previous studies have examined the effects of mid-life physical activity on healthy ageing, but not the effects of taking up activity later in life. We examined the association between physical activity and healthy ageing over 8 years of follow-up.

Methods

Participants were 3454 initially disease-free men and women (aged 63.7±8.9 years at baseline) from the English Longitudinal Study of Ageing, a prospective study of community dwelling older adults. Self-reported physical activity was assessed at baseline (2002–2003) and through follow-up. Healthy ageing, assessed at 8 years of follow-up (2010-2011), was defined as those participants who survived without developing major chronic disease, depressive symptoms, physical or cognitive impairment.

Results

At follow-up, 19.3% of the sample was defined as healthy ageing. In comparison with inactive participants, moderate (OR, 2.67, 95% CI 1.95 to 3.64), or vigorous activity (3.53, 2.54 to 4.89) at least once a week was associated with healthy ageing, after adjustment for age, sex, smoking, alcohol, marital status and wealth. Becoming active (multivariate adjusted, 3.37, 1.67 to 6.78) or remaining active (7.68, 4.18 to 14.09) was associated with healthy ageing in comparison with remaining inactive over follow-up.

Conclusions

Sustained physical activity in older age is associated with improved overall health. Significant health benefits were even seen among participants who became physically active relatively late in life.

Inflammation and atherosclerosis: disease modulating therapies

OPINION STATEMENT

Advances in the mechanistic understanding of atheroma initiation, repair, progression, and rupture have solidified the pivotal role played by the immune system in the pathophysiology of atherosclerotic vascular disease. These mechanistic findings have been extended into humans, with a strong evidence basis for the independent association between elevated blood markers of inflammation and future cardiovascular (CV) events. Investigations with statins as well as more conventional anti-inflammatory medications provide indirect evidence to support the concept that modifying immune responses can improve CV outcomes; however, robust evidence to support the use of anti-inflammatory treatment strategies to manage atherosclerotic vascular disease is still lacking. Such evidence may emerge from a new wave of clinical trials directly exploring the effects of targeted immune modulation on CV risk. These trials will provide key additional insights into atherosclerosis and will help determine the fate of immune modulation as a new treatment strategy in atherosclerotic vascular disease.

Increased basal and alum-induced interleukin-6 levels in geriatric patients are associated with cardiovascular morbidity

BACKGROUND/AIM OF THE STUDY

Low-grade systemic inflammation was suggested to participate to the decline of physiological functions and increased vulnerability encountered in older patients. Geriatric syndromes encompass various features such as functional dependence, polymorbidity, depression and malnutrition. There is a strong prevalence of cardiovascular diseases and related risk factors and chronic cytomegalovirus infections in the geriatric population. As these underlying conditions were proposed to influence the inflammatory state, the aim of this study was to assess their potential contribution to the association of geriatric syndromes with inflammatory parameters.

METHODOLOGY

We recruited 100 subjects in the general population or hospitalized for chronic medical conditions (age, 23-96 years). We collected information on clinical status (medical history, ongoing comorbidities, treatments and geriatric scales), biological parameters (hematological tests, cytomegalovirus serology) and cytokines production (basal and alum-induced interleukin (IL)-1β and IL-6 levels). Using stepwise backward multivariate analyses, we defined which set of clinical and biological variables could be predictive for increased inflammatory markers.

PRINCIPAL FINDINGS

We confirmed the age-associated increase of circulating IL-6 levels. In contrast to geriatric scales, we found history of cardiovascular diseases to be strongly associated for this parameter as for high IL-6 production upon ex vivo stimulation with alum.

CONCLUSIONS

Association between low-grade inflammation and geriatric conditions could be linked to underlying cardiovascular diseases.

Molecular sources of residual cardiovascular risk, clinical signals, and innovative solutions: relationship with subclinical disease, undertreatment, and poor adherence: implications of new evidence upon optimizing cardiovascular patient outcomes

Residual risk, the ongoing appreciable risk of major cardiovascular events (MCVE) in statin-treated patients who have achieved evidence-based lipid goals, remains a concern among cardiologists. Factors that contribute to this continuing risk are atherogenic non-low-density lipoprotein (LDL) particles and atherogenic processes unrelated to LDL cholesterol, including other risk factors, the inherent properties of statin drugs, and patient characteristics, ie, genetics and behaviors. In addition, providers, health care systems, the community, public policies, and the environment play a role. Major statin studies suggest an average 28% reduction in LDL cholesterol and a 31% reduction in relative risk, leaving a residual risk of about 69%. Incomplete reductions in risk, and failure to improve conditions that create risk, may result in ongoing progression of atherosclerosis, with new and recurring lesions in original and distant culprit sites, remodeling, arrhythmias, rehospitalizations, invasive procedures, and terminal disability. As a result, identification of additional agents to reduce residual risk, particularly administered together with statin drugs, has been an ongoing quest. The current model of atherosclerosis involves many steps during which disease may progress independently of guideline-defined elevations in LDL cholesterol. Differences in genetic responsiveness to statin therapy, differences in ability of the endothelium to regenerate and repair, and differences in susceptibility to nonlipid risk factors, such as tobacco smoking, hypertension, and molecular changes associated with obesity and diabetes, may all create residual risk. A large number of inflammatory and metabolic processes may also provide eventual therapeutic targets to lower residual risk. Classically, epidemiologic and other evidence suggested that raising high-density lipoprotein (HDL) cholesterol would be cardioprotective. When LDL cholesterol is aggressively lowered to targets, low HDL cholesterol levels are still inversely related to MCVE. The efflux capacity, or ability to relocate cholesterol out of macrophages, is believed to be a major antiatherogenic mechanism responsible for reduction in MCVE mediated in part by healthy HDL. HDL cholesterol is a complex molecule with antioxidative, anti-inflammatory, anti-thrombotic, antiplatelet, and vasodilatory properties, among which is protection of LDL from oxidation. HDL-associated paraoxonase-1 has a major effect on endothelial function. Further, HDL promotes endothelial repair and progenitor cell health, and supports production of nitric oxide. HDL from patients with cardiovascular disease, diabetes, and autoimmune disease may fail to protect or even become proinflammatory or pro-oxidant. Mendelian randomization and other clinical studies in which raising HDL cholesterol has not been beneficial suggest that high plasma levels do not necessarily reduce cardiovascular risk. These data, coupled with extensive preclinical information about the functional heterogeneity of HDL, challenge the "HDL hypothesis", ie, raising HDL cholesterol per se will reduce MCVE. After the equivocal AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides: Impact on Global Health Outcomes) study and withdrawal of two major cholesteryl ester transfer protein compounds, one for off-target adverse effects and the other for lack of efficacy, development continues for two other agents, ie, anacetrapib and evacetrapib, both of which lower LDL cholesterol substantially. The negative but controversial HPS2-THRIVE (the Heart Protection Study 2-Treatment of HDL to Reduce the Incidence of Vascular Events) trial casts further doubt on the HDL cholesterol hypothesis. The growing impression that HDL functionality, rather than abundance, is clinically important is supported by experimental evidence highlighting the conditional pleiotropic actions of HDL. Non-HDL cholesterol reflects the cholesterol in all atherogenic particles containing apolipoprotein B, and has outperformed LDL cholesterol as a lipid marker of cardiovascular risk and future mortality. In addition to including a measure of residual risk, the advantages of using non-HDL cholesterol as a primary lipid target are now compelling. Reinterpretation of data from the Treating to New Targets study suggests that better control of smoking, body weight, hypertension, and diabetes will help lower residual risk. Although much improved, control of risk factors other than LDL cholesterol currently remains inadequate due to shortfalls in compliance with guidelines and poor patient adherence. More efficient and greater use of proven simple therapies, such as aspirin, beta-blockers, angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, combined with statin therapy, may be more fruitful in improving outcomes than using other complex therapies. Comprehensive, intensive, multimechanistic, global, and national programs using primordial, primary, and secondary prevention to lower the total level of cardiovascular risk are necessary.

Interleukin 6 stimulates endothelial binding and transport of high-density lipoprotein through induction of endothelial lipase

OBJECTIVE

In the reverse cholesterol transport pathway, high-density lipoprotein (HDL) passes the endothelial cell barrier by mechanisms involving the scavenger receptor class B type I and the ATP-binding cassette G1. However, little is known on how inflammation influences this transendothelial transport.

APPROACH AND RESULTS

On stimulation with interleukin-6, cultivated primary endothelial cells showed increased binding and transport of (125)I-HDL without changing the expression of scavenger receptor class B type I and ATP-binding cassette G1. Therefore, we analyzed the involvement of endothelial lipase (EL), a known HDL-binding protein expressed by endothelial cells. Here, we show an increased EL expression after interleukin-6 stimulation. Moreover, using pharmacological inhibitors or RNA interference against EL, we demonstrated its participation in HDL binding and transport through the endothelium. Furthermore, adenovirus-mediated transfection of endothelial cells with either catalytically active or nonactive EL revealed that EL facilitates the endothelial binding and transport by both bridging and lipolysis of HDL. EL was also found responsible for the reduction of HDL particle size occurring during the specific transport through a monolayer of endothelial cells. Finally, pharmacological inhibition of EL reversed the inducing effect of interleukin-6 on HDL binding and transport.

CONCLUSIONS

Interleukin-6 stimulates the translocation of HDL through the endothelium, the first step in reverse cholesterol transport pathway, by enhancing EL expression. In addition, we demonstrated the role of EL in the transendothelial transport of HDL.

Interleukin-6 cytokine: a multifunctional glycoprotein for cancer

Interleukin 6 is a multifunctional cytokine. Its increased levels have been associated with elevated cancer risk, and also these levels have been found to be a prognostic factor for several cancer types. In addition, increased levels have been found in coronary heart disease, insulin resistant patients, advance stage cancer patients, atopy/asthma and in patients with blood circulating micrometastasis. Additionally several studies with different types of cancers have been performed to identify the correlation between interleukin-6 levels, stage, treatment response and severity of symptoms. The influence of interleukin-6 is performed mainly through the janus kinase-signal transducer and activator of transcription-zinc finger protein 1-2 signaling pathway. As a result, the increased levels of interleukin-6 are responsible for enhanced neo-angiogenesis, inhibition of cancer cell apoptosis and deregulation of the control mechanisms in the microenvironment. In addition, increased levels of inteleukin-6 have been found to increase the production of collagen and a-actin which induce interstitial lung disease. In the current mini review we will present information regarding the interleukin-6 and published results in several cancer studies and finally we will comment in future treatment approaches blocking this cytokine in cancer patients.

Mendelian randomization analysis with multiple genetic variants using summarized data

Genome-wide association studies, which typically report regression coefficients summarizing the associations of many genetic variants with various traits, are potentially a powerful source of data for Mendelian randomization investigations. We demonstrate how such coefficients from multiple variants can be combined in a Mendelian randomization analysis to estimate the causal effect of a risk factor on an outcome. The bias and efficiency of estimates based on summarized data are compared to those based on individual-level data in simulation studies. We investigate the impact of gene–gene interactions, linkage disequilibrium, and ‘weak instruments’ on these estimates. Both an inverse-variance weighted average of variant-specific associations and a likelihood-based approach for summarized data give similar estimates and precision to the two-stage least squares method for individual-level data, even when there are gene–gene interactions. However, these summarized data methods overstate precision when variants are in linkage disequilibrium. If the P-value in a linear regression of the risk factor for each variant is less than , then weak instrument bias will be small. We use these methods to estimate the causal association of low-density lipoprotein cholesterol (LDL-C) on coronary artery disease using published data on five genetic variants. A 30% reduction in LDL-C is estimated to reduce coronary artery disease risk by 67% (95% CI: 54% to 76%). We conclude that Mendelian randomization investigations using summarized data from uncorrelated variants are similarly efficient to those using individual-level data, although the necessary assumptions cannot be so fully assessed.

Lack of an association between interleukin-6 -174G/C polymorphism and circulating interleukin-6 levels in normal population: a meta-analysis

Interleukin-6 (IL-6) signaling may play a causal role in the development of coronary heart disease. However, the relationship between IL-6 genotypes and plasma levels of IL-6 appears to be complex. To help clarify the inconsistent findings, we conducted a meta-analysis of the published genetic association studies of the -174 G/C polymorphisms in the IL-6 gene and the circulating IL-6 levels in a normal population. In this meta-analysis, no significant association of IL-6 -174G/C polymorphism and circulating IL-6 levels in a normal population was observed. However, when compared among GG, GC, and CC genotypes, heterogeneity existed among the studies. Sensitivity analysis revealed that, the independent study by Shen et al. influenced the heterogeneity in the homozygous and heterozygous comparison. Although Shen et al.'s study was excluded, no significant association was observed between IL-6 -174G/C polymorphism and circulating IL-6 levels in a normal population [homozygous comparison (GG vs. CC): the pooled standard mean difference (SMD) was -0.01, 95% confidence interval (CI): -0.1-0.08; heterozygous comparison (GC vs. GG or CC): the pooled SMD (GG vs. GC) was -0.05, 95%CI: -0.11-0.01, and the pooled SMD (CC vs. GC) was 0.03, 95%CI: -0.03-0.1]. Under the dominant model, the pooled SMD was -0.05, 95%CI: -0.11-0.01). The meta-analysis provides evidence that the -174G/C polymorphism in the IL-6 gene is not significantly associated with circulating IL-6 levels in a normal population.

Chitin enhances obese inflammation ex vivo

Infection has been implicated as a co-risk factor for obesity, but the mechanism remains uncertain. Elevated levels of plasma chitinase 3-like 1 (CHI3L1) are found in obese individuals. Since CHI3L1 is produced by activated immune cells including macrophages and recognizes microbial N-acetylglucosamine polymer (chitin), we asked whether the plasma CHI3L1 protein change in obese individuals might alter their innate immune response to chitin. Thirty-six subjects (15 obese and 21 non-obese), ages 18-30 years, were recruited. Peripheral blood mononuclear cells (PBMCs) were cultured with chitin microparticles (CMP; 1-10 μm) for 24h; tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and CHI3L1 in the culture supernatants were measured. We chose CMP, since neither large chitin beads (40-100 μm), chitosan microparticles (1-10 μm), nor soluble chitin induced the cytokine/CHI3L1 production by PBMCs isolated from non-obese PBMCs ex vivo. We found that the quantity of IL-6, but not TNF-α or CHI3L1, induced by CMP was significantly correlated with plasma IL-6, BMI, waist/hip circumferences, fasting plasma insulin, and insulin resistance. These findings suggest that chitin, a substrate of CHI3L1, further promotes obese inflammation in a size- and chemical composition- dependent manner.

Chronic inflammation as a determinant of future aging phenotypes

BACKGROUND

The importance of chronic inflammation as a determinant of aging phenotypes may have been underestimated in previous studies that used a single measurement of inflammatory markers. We assessed inflammatory markers twice over a 5-year exposure period to examine the association between chronic inflammation and future aging phenotypes in a large population of men and women.

METHODS

We obtained data for 3044 middle-aged adults (28.2% women) who were participating in the Whitehall II study and had no history of stroke, myocardial infarction or cancer at our study's baseline (1997-1999). Interleukin-6 was measured at baseline and 5 years earlier. Cause-specific mortality, chronic disease and functioning were ascertained from hospital data, register linkage and clinical examinations. We used these data to create 4 aging phenotypes at the 10-year follow-up (2007-2009): successful aging (free of major chronic disease and with optimal physical, mental and cognitive functioning), incident fatal or nonfatal cardiovascular disease, death from noncardiovascular causes and normal aging (all other participants).

RESULTS

Of the 3044 participants, 721 (23.7%) met the criteria for successful aging at the 10-year follow-up, 321 (10.6%) had cardiovascular disease events, 147 (4.8%) died from noncardiovascular causes, and the remaining 1855 (60.9%) were included in the normal aging phenotype. After adjustment for potential confounders, having a high interleukin-6 level (> 2.0 ng/L) twice over the 5-year exposure period nearly halved the odds of successful aging at the 10-year follow-up (odds ratio [OR] 0.53, 95% confidence interval [CI] 0.38-0.74) and increased the risk of future cardiovascular events (OR 1.64, 95% CI 1.15-2.33) and noncardiovascular death (OR 2.43, 95% CI 1.58-3.80).

INTERPRETATION

Chronic inflammation, as ascertained by repeat measurements, was associated with a range of unhealthy aging phenotypes and a decreased likelihood of successful aging. Our results suggest that assessing long-term chronic inflammation by repeat measurement of interleukin-6 has the potential to guide clinical practice.

Associations between change in sleep duration and inflammation: findings on C-reactive protein and interleukin 6 in the Whitehall II Study

Cross-sectional evidence suggests associations between sleep duration and levels of the inflammatory markers, C-reactive protein and interleukin-6. This longitudinal study uses data from the London-based Whitehall II study to examine whether changes in sleep duration are associated with average levels of inflammation from 2 measures 5 years apart. Sleep duration (≤5, 6, 7, 8, ≥9 hours on an average week night) was assessed in 5,003 middle-aged women and men in 1991/1994 and 1997/1999. Fasting levels of C-reactive protein and interleukin-6 were measured in 1997/1999 and 2002/2004. Cross-sectional analyses indicated that shorter sleep is associated with higher levels of inflammatory markers. Longitudinal analyses showed that each hour per night decrease in sleep duration between 1991/1994 and 1997/1999 was associated with higher levels of C-reactive protein (8.1%) and interleukin-6 (4.5%) averaged across measures in 1997/1999 and 2002/2004. Adjustment for longstanding illness and major cardiometabolic risk factors indicated that disease processes may partially underlie these associations. An increase in sleep duration was not associated with average levels of inflammatory markers. These results suggest that both short sleep and reductions in sleep are associated with average levels of inflammation over a 5-year period.

Inflammatory cytokines and risk of coronary heart disease: new prospective study and updated meta-analysis

AIMS

Because low-grade inflammation may play a role in the pathogenesis of coronary heart disease (CHD), and pro-inflammatory cytokines govern inflammatory cascades, this study aimed to assess the associations of several pro-inflammatory cytokines and CHD risk in a new prospective study, including meta-analysis of prospective studies.

METHODS AND RESULTS

Interleukin-6 (IL-6), IL-18, matrix metalloproteinase-9 (MMP-9), soluble CD40 ligand (sCD40L), and tumour necrosis factor-α (TNF-α) were measured at baseline in a case-cohort study of 1514 participants and 833 incident CHD events within population-based prospective cohorts at the Danish Research Centre for Prevention and Health. Age- and sex-adjusted hazard ratios (HRs) for CHD per 1-SD higher log-transformed baseline levels were: 1.37 (95% CI: 1.21-1.54) for IL-6, 1.26 (1.11-1.44) for IL-18, 1.30 (1.16-1.46) for MMP-9, 1.01 (0.89-1.15) for sCD40L, and 1.13 (1.01-1.27) for TNF-α. Multivariable adjustment for conventional vascular risk factors attenuated the HRs to: 1.26 (1.08-1.46) for IL-6, 1.12 (0.95-1.31) for IL-18, 1.21 (1.05-1.39) for MMP-9, 0.93 (0.78-1.11) for sCD40L, and 1.14 (1.00-1.31) for TNF-α. In meta-analysis of up to 29 population-based prospective studies, adjusted relative risks for non-fatal MI or CHD death per 1-SD higher levels were: 1.25 (1.19-1.32) for IL-6; 1.13 (1.05-1.20) for IL-18; 1.07 (0.97-1.19) for MMP-9; 1.07 (0.95-1.21) for sCD40L; and 1.17 (1.09-1.25) for TNF-α.

CONCLUSIONS

Several different pro-inflammatory cytokines are each associated with CHD risk independent of conventional risk factors and in an approximately log-linear manner. The findings lend support to the inflammation hypothesis in vascular disease, but further studies are needed to assess causality.

Interleukin-6 and activin A are independently associated with cardiovascular events and mortality in type 2 diabetes: the prospective Asker and Bærum Cardiovascular Diabetes (ABCD) cohort study

Background

Novel and robust cardiovascular (CV) markers are needed to improve CV morbidity and mortality risk prediction in type 2 diabetes (T2D). We assessed the long term predictive value of 4 novel CV risk markers for major CV events and mortality.

Methods

We included patients with T2D who had cytokines (interleukin [IL]-6 and activin A [actA]), a maximum stress ECG test (evaluated by the normalization pattern in early recovery phase) and echocardiography (evaluated by a measure of the left ventricular filling pressure - E/Em) assessed at baseline. The primary endpoint was time to first of any of the following events: myocardial infarction, stroke, hospitalization for unstable angina pectoris and death. All outcomes were adjudicated by independent experts. We used Cox proportional hazard modeling, Harrell C-statistic and the net reclassification improvement (NRI) to assess the additional value beyond conventional markers (age, gender, prior CV disease, HDL, creatinine, diastolic BP, microalbuminuria).

Results

At baseline the study cohort (n = 135, mean age/diabetes duration/HbA1c: 59 yrs/7 yrs/7.6% [59 mmol/mol], 26% females) had moderate elevated CV risk (42% microalbuminuria, mean Framingham 10 year CV-risk 9.6%). During 8.6 yrs/1153.7 person years, 26 patients experienced 36 events. All 4 novel risk markers were significantly associated with increased risk of the primary endpoint, however, only IL-6 and actA improved C-statistic and NRI (+0.119/43.2%, +0.065/20.3% respectively) compared with the conventional CV risk factors.

Conclusions

IL-6 and actA may provide prognostic information on CV events and mortality in T2D beyond conventional CV risk factors.

Trial registration

ClinicalTrials.gov: NCT00133718

Imbalanced frequencies of Th17 and Treg cells in acute coronary syndromes are mediated by IL-6-STAT3 signaling

Aims

Extensive evidence suggests inflammatory components participate in the pathogenic processes of acute coronary syndromes (ACS). In this study, we aimed to elucidate the role and mechanism underlying the imbalance of Th17 and Treg cell peripheral populations in the pathogenesis of ACS.

Methods and Results

Using a flow cytometric analysis, we observed a significantly increased frequency of Th17 cells and a concurrently decreased CD4⁺CD25⁺Foxp3⁺ Treg cells in patients with ACS. To elucidate the mechanism of Th17/Treg imbalance in ACS, 22 inflammatory cytokines were measured using multiplexed immunobead-based assays. Of six elevated cytokines in ACS patients, only IL-6 was positively correlated with a higher Th17 cell level (r = 0.39, P<0.01). Relying on IL-6 stimulating and neutralizing studies, we demonstrated a direct role for IL-6 in sera from ACS patients with an increased frequency of Th17 cells. IL-6 induces the differentiation of Th17 cells from naïve CD4⁺ T cells through STAT3 activation and RORγt induction. However, we observed that high levels of TGF-β1 inhibited IL-6-dependent Th17 cell differentiation, indicating a complex interplay between the two cytokines in the control of Th17 and Treg cell populations.

Conclusions

Our results demonstrate the role of IL-6-STAT3 signaling in ACS through increased Th17 cell differentiation. These findings indicate that IL-6 neutralizing strategies could present novel therapeutic avenues in the treatment of ACS.

High-sensitivity C-reactive protein and atherosclerotic disease: from improved risk prediction to risk-guided therapy

There is compelling experimental and clinical evidence suggesting a crucial role for inflammation in the initiation and also the progression of atherosclerosis. Numerous biomarkers involved at various levels of the inflammation cascade have been shown to be associated with adverse cardiovascular outcomes. Yet, to date, it is not clear whether inflammation simply accompanies the atherosclerotic process or represents a major driver. Among all blood biomarkers, C-reactive protein (CRP), the classical acute phase reactant that can be measured with high-sensitivity (hs) assays seems to be the most promising candidate. It has already found its way into the guidelines in primary prevention. Hs-CRP can also be used to identify a high-risk group for recurrent events in patients with manifest atherosclerosis. Several post hoc analyses of large-scale randomized clinical trials testing various statins have indicated that, besides low density lipoprotein (LDL) cholesterol, hs-CRP levels might also further aid in tailoring statin treatment. The large JUPITER trial has prospectively confirmed these findings in primary prevention in patients with elevated hs-CRP but normal LDL cholesterol levels. Still, statin therapy is not a specific anti-inflammatory regime acting on the inflammation cascade. Thus, to directly test the inflammation hypothesis, a novel, more proximally located cytokine-based approach is needed. Canakinumab, a fully human monoclonal antibody against interleukin-1β, might represent a promising compound in this regard and provide a proof of concept. If successful, this may become a novel strategy to treat high-risk patients with stable atherosclerotic disease to prevent recurrent events on top of standard medical care.

Relationship among circulating inflammatory proteins, platelet gene expression, and cardiovascular risk

OBJECTIVE

Cardiovascular disease is a complex disorder influenced by interactions of genetic variants with environmental factors. However, there is no information from large community-based studies examining the relationship of circulating cell-specific RNA to inflammatory proteins. In light of the associations among inflammatory biomarkers, obesity, platelet function, and cardiovascular disease, we sought to examine the relationships of C-reactive protein (CRP) and interleukin-6 (IL-6) to the expression of key inflammatory transcripts in platelets.

APPROACH AND RESULTS

We quantified circulating levels of CRP and IL-6 in 1625 participants of the Framingham Heart Study (FHS) Offspring cohort examination 8 (mean age, 66.6 ± 6.6 years; 46% men). We measured the expression of 15 relevant genes by high-throughput quantitative reverse transcriptase polymerase chain reaction from platelet-derived RNA and used multivariable regression to relate serum concentrations of CRP and IL-6 with gene expression. Levels of CRP and IL-6 were associated with 10 of the 15 platelet-derived inflammatory transcripts, ALOX5, CRP, IFIT1, IL6, PTGER2, S100A9, SELENBP1, TLR2, TLR4, and TNFRSF1B (P<0.001). Associations between platelet mRNA expression with CRP and IL-6 persisted after multivariable adjustment for potentially confounding factors. Six genes positively associated with CRP or IL-6 in the FHS sample were also upregulated in megakaryocytes in response to CRP or IL-6 exposure.

CONCLUSIONS

Our data highlight the strong connection between the circulating inflammatory biomarkers CRP and IL-6 and platelet gene expression, adjusting for cardiovascular disease risk factors. Our results also suggest that body weight may directly influence these associations.

IL-6 pathway-driven investigation of response to IL-6 receptor inhibition in rheumatoid arthritis

OBJECTIVES

To determine whether heterogeneity in interleukin-6 (IL-6), IL-6 receptor and other components of the IL-6 signalling pathway/network, at the gene, transcript and protein levels, correlate with disease activity in patients with rheumatoid arthritis (RA) and with clinical response to tocilizumab.

DESIGN

Biomarker samples and clinical data for five phase 3 trials of tocilizumab were analysed using serum (3751 samples), genotype (927 samples) and transcript (217 samples) analyses. Linear regression was then used to assess the association between these markers and either baseline disease activity or treatment response.

RESULTS

Higher baseline serum IL-6 levels were significantly associated (p<0.0001) with higher baseline DAS28, erythrocyte sedimentation rate, C reactive protein and Health Assessment Questionnaire in patients whose responses to disease-modifying antirheumatic drugs (DMARD-IR) and to antitumour necrosis factor (aTNF-IR) were inadequate and patients who were naive/responders to methotrexate (MTX). Higher baseline serum IL-6 levels were also significantly associated with better clinical response to tocilizumab (versus placebo) measured by cDAS28 in the pooled DMARD-IR (p<0.0001) and MTX-naive populations (p=0.04). However, the association with treatment response was weak. A threefold difference in baseline IL-6 level corresponded to only a 0.17-unit difference in DAS28 at week 16. IL-6 pathway single nucleotide polymorphisms and RNA levels also were not strongly associated with treatment response.

CONCLUSIONS

Our analyses illustrate that the biological activity of a disease-associated molecular pathway may impact the benefit of a therapy targeting that pathway. However, the variation in pathway activity, as measured in blood, may not be a strong predictor. These data suggest that the major contribution to variability in clinical responsiveness to therapeutics in RA remains unknown.

A new regulatory variant in the interleukin-6 receptor gene associates with asthma risk

The main genetic determinant of soluble interleukin 6 receptor (sIL-6R) levels is the missense variant rs2228145 that maps to the cleavage site of IL-6R. For each Ala allele, sIL-6R serum levels increase by ≈ 20 ng ml(-1) and asthma risk by 1.09-fold. However, this variant does not explain the total heritability for sIL-6R levels. Additional independent variants in IL6R may therefore contribute to variation in sIL-6R levels and influence asthma risk. We imputed 471 variants in IL6R and tested these for association with sIL-6R serum levels in 360 individuals. An intronic variant (rs12083537) was associated with sIL-6R levels independently of rs4129267 (P=0.0005), a proxy single-nucleotide polymorphism for rs2228145. A significant and consistent association for rs12083537 was observed in a replication panel of 354 individuals (P=0.033). Each rs12083537:A allele increased sIL-6R serum levels by 2.4 ng ml(-1). Analysis of mRNA levels in two cohorts did not identify significant associations between rs12083537 and IL6R transcription levels. On the other hand, results from 16,705 asthmatics and 30,809 controls showed that the rs12083537:A allele increased asthma risk by 1.04-fold (P=0.0419). Genetic risk scores based on IL6R regulatory variants may prove useful in explaining variation in clinical response to tocilizumab, an anti-IL-6R monoclonal antibody.

Soluble interleukin-6 receptor-mediated innate immune response to DNA and RNA viruses

The interleukin-6 (IL-6) receptor, which exists as membrane-bound and soluble forms, plays critical roles in the immune response. The soluble IL-6 receptor (sIL6R) has been identified as a potential therapeutic target for preventing coronary heart disease. However, little is known about the role of this receptor during viral infection. In this study, we show that sIL6R, but not IL-6, is induced by viral infection via the cyclooxygenase-2 pathway. Interestingly, sIL6R, but not IL-6, exhibited extensive antiviral activity against DNA and RNA viruses, including hepatitis B virus, influenza virus, human enterovirus 71, and vesicular stomatitis virus. No synergistic effects on antiviral action were observed by combining sIL6R and IL-6. Furthermore, sIL6R mediated antiviral action via the p28 pathway and induced alpha interferon (IFN-α) by promoting the nuclear translocation of IFN regulatory factor 3 (IRF3) and NF-κB, which led to the activation of downstream IFN effectors, including 2',5'-oligoadenylate synthetase (OAS), double-stranded RNA-dependent protein kinase (PKR), and myxovirus resistance protein (Mx). Thus, our results demonstrate that sIL6R, but not IL-6, plays an important role in the host antiviral response.

Relationship of CRP, IL-6, and fibrinogen with right ventricular structure and function: the MESA-Right Ventricle Study

BACKGROUND/OBJECTIVES

Inflammation contributes to the pathogenesis of disease associated with the left ventricle (LV); yet, our understanding of the effect of inflammation on the right ventricle (RV) is quite limited.

METHODS AND RESULTS

The relationships of C-reactive protein (CRP), interleukin-6 (IL-6) and fibrinogen with RV morphology and function (from cardiac MRI) were examined in participants free of clinical cardiovascular disease (n=4009) from the Multi-Ethnic Study of Atherosclerosis (MESA)-RV study. Multivariable regressions (linear, quantile [25th and 75th] and generalized additive models [GAM]) were used to examine the independent association of CRP, IL-6 and fibrinogen with RV mass, RV end-diastolic volume (RVEDV), RV end-systolic volume (RVESV), RV stroke volume (RVSV) and RV ejection fraction (RVEF). Unadjusted and adjusted analyses revealed strong inverse associations between both CRP and IL-6 with RV mass, RVEDV, RVESV and RVSV (all p<0.01); there were no associations with RVEF. These relationships remained significant after adjustment for the respective LV parameters and lung function. However, GAM models suggested that extreme values of CRP and IL-6 might have positive associations with RV parameters. Fibrinogen showed significant associations in unadjusted models, but no associations after adjustment or in sensitivity analyses.

CONCLUSION

Levels of CRP and IL-6 are independently associated with RV morphology even after adjustment for the respective LV measure in this multi-ethnic population free of clinical cardiovascular disease. Systemic inflammation may contribute to RV structural changes independent of effects on the LV.

Validating therapeutic targets through human genetics

More than 90% of the compounds that enter clinical trials fail to demonstrate sufficient safety and efficacy to gain regulatory approval. Most of this failure is due to the limited predictive value of preclinical models of disease, and our continued ignorance regarding the consequences of perturbing specific targets over long periods of time in humans. 'Experiments of nature' - naturally occurring mutations in humans that affect the activity of a particular protein target or targets - can be used to estimate the probable efficacy and toxicity of a drug targeting such proteins, as well as to establish causal rather than reactive relationships between targets and outcomes. Here, we describe the concept of dose-response curves derived from experiments of nature, with an emphasis on human genetics as a valuable tool to prioritize molecular targets in drug development. We discuss empirical examples of drug-gene pairs that support the role of human genetics in testing therapeutic hypotheses at the stage of target validation, provide objective criteria to prioritize genetic findings for future drug discovery efforts and highlight the limitations of a target validation approach that is anchored in human genetics.

Job strain and cardiovascular disease risk factors: meta-analysis of individual-participant data from 47,000 men and women

BACKGROUND

Job strain is associated with an increased coronary heart disease risk, but few large-scale studies have examined the relationship of this psychosocial characteristic with the biological risk factors that potentially mediate the job strain - heart disease association.

METHODOLOGY AND PRINCIPAL FINDINGS

We pooled cross-sectional, individual-level data from eight studies comprising 47,045 participants to investigate the association between job strain and the following cardiovascular disease risk factors: diabetes, blood pressure, pulse pressure, lipid fractions, smoking, alcohol consumption, physical inactivity, obesity, and overall cardiovascular disease risk as indexed by the Framingham Risk Score. In age-, sex-, and socioeconomic status-adjusted analyses, compared to those without job strain, people with job strain were more likely to have diabetes (odds ratio 1.29; 95% CI: 1.11-1.51), to smoke (1.14; 1.08-1.20), to be physically inactive (1.34; 1.26-1.41), and to be obese (1.12; 1.04-1.20). The association between job strain and elevated Framingham risk score (1.13; 1.03-1.25) was attributable to the higher prevalence of diabetes, smoking and physical inactivity among those reporting job strain.

CONCLUSIONS

In this meta-analysis of work-related stress and cardiovascular disease risk factors, job strain was linked to adverse lifestyle and diabetes. No association was observed between job strain, clinic blood pressure or blood lipids.

Changes in lipid levels with inflammation and therapy in RA: a maturing paradigm

Dyslipidaemia is commonly observed in patients with active rheumatoid arthritis (RA), with lower total cholesterol levels as well as lower levels of high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) reported in these patients than in individuals without RA. This pattern is mirrored in sepsis and other inflammatory states, suggesting systemic inflammation has the general effect of lowering circulating lipid levels. In line with such observations, suppressing inflammation with DMARDs, biologic therapies and small-molecule Janus kinase inhibitors seems to elevate levels of lipid fractions in RA, albeit in a variable manner dependent presumably upon the mechanism of action of the different agents. In addition, limited epidemiological data in patients with RA suggest increased cardiovascular disease (CVD) risk at relatively low cholesterol levels, a pattern contrasting with that observed in the population without RA. Our understanding of the potential mechanisms behind these inflammation-associated lipid changes remains suboptimal and requires further study. In clinical terms, however, use of the total cholesterol to HDL-C ratio as the lipid component of CVD risk scoring in patients with RA would seem appropriate given that these lipid parameters generally change in parallel with inflammation and suppression of inflammation. Whether alternative lipid or lipoprotein measures (or simple markers of inflammation) could improve stratification of CVD risk in RA beyond the established risk factors requires future investigation.

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.