Analysis of the genetic variants associated with circulating levels of sgp130. Results from the IMPROVE study.

The genes regulating circulating levels of soluble gp130 (sgp130), the antagonist of the inflammatory response in atherosclerosis driven by interleukin 6, are largely unknown. Aims of the present study were to identify genetic loci associated with circulating sgp130 and to explore the potential association between variants associated with sgp130 and markers of subclinical atherosclerosis. The study is based on IMPROVE (n = 3703), a cardiovascular multicentre study designed to investigate the determinants of carotid intima media thickness, a measure of subclinical atherosclerosis. Genomic DNA was genotyped by the CardioMetaboChip and ImmunoChip. About 360,842 SNPs were tested for association with log-transformed sgp130, using linear regression adjusted for age, gender, and population stratification using PLINK v1.07. A p value of 1 × 10-5 was chosen as threshold for significance value. In an exploratory analysis, SNPs associated with sgp130 were tested for association with c-IMT measures. We identified two SNPs significantly associated with sgp130 levels and 24 showing suggestive association with sgp130 levels. One SNP (rs17688225) on chromosome 14 was positively associated with sgp130 serum levels (ß = 0.03 SE = 0.007, p = 4.77 × 10-5) and inversely associated with c-IMT (c-IMTmean-max ß = -0.001 SE = 0.005, p = 0.0342). Our data indicate that multiple loci regulate sgp130 levels and suggest a possible common pathway between sgp130 and c-IMT measures.

IgM antibodies against malondialdehyde and phosphorylcholine are together strong protection markers for atherosclerosis in systemic lupus erythematosus: Regulation and underlying mechanisms.

OBJECTIVES: Phosphorylcholine (PC) and malondialdehyde (MDA) are generated during lipid peroxidation and form adducts with proteins as albumin as studied herein. Atherosclerosis and cardiovascular disease (CVD) are increased in systemic lupus erythematosus (SLE). We here investigate the role and regulation of IgM antibodies against PC (anti-PC) and MDA (anti-MDA). METHODS: IgM anti-PC and anti-MDA in SLE patients (n=114) were compared with age- and sex-matched population-based controls (n=108). Common carotid intima-media thickness (IMT) and plaque occurrence were determined by B-mode ultrasound. Plaques were graded according to echogenicity (potentially vulnerability). Production of IgM anti-PC and anti-MDA by B cells was determined by ELISA and ELISPOT. The effect of anti-PC and anti-MDA on macrophage uptake of apoptotic cells and oxidative stress was studied by flow cytometry. RESULTS: Above 66rd percentile together, IgM anti-PC and anti-MDA were striking protection markers for plaque prevalence and echolucency in SLE (OR: 0.08, CI: 0.01-0.46 and OR: 0.10, CI: 0.01-0.82), respectively, and risk markers for plaque prevalence when below 33rd percentile: OR: 3.79, CI: (1.10-13.00). In vitro, IgM anti-PC and anti-MDA were much higher when B cells were co-cultured with CD3 T cells. Anti-HLA-, anti-CD40 antibody or CD40 silencing abolished these effects. Uptake of apoptotic cells was increased by IgM anti-PC and anti-MDA. MDA induced increased oxidative stress, which was inhibited by IgM anti-MDA. CONCLUSIONS: Unexpectedly, both IgM anti-MDA and IgM anti-PC are T-cell dependent and especially together, are strong protection markers for atherosclerosis in SLE. Underlying mechanisms include increased phagocytosis of apoptotic cells and decrease of oxidative stress.

Circulating levels of interleukin 6 soluble receptor and its natural antagonist, sgp130, and the risk of myocardial infarction.

OBJECTIVE: To investigate the association between circulating levels of the soluble interleukin 6 receptor (sIL6R) and the soluble gp130 (sgp130) with myocardial infarction (MI) and to explore the potential interaction between sIL6R and sgp130 in this association. METHODS: Study population is the Stockholm Heart Epidemiology Program (SHEEP), a population-based case-control study. SIL6R (ng/mL) and sgp130 (ng/mL) levels were measured in serum samples from 682 and 664 MI cases and 1103 and 1062 controls, respectively. Odds ratios (with 95% CIs) for MI were calculated using unconditional logistic regression. We adjusted for age, sex, hospital catchment area (crude) and for hypertension, diabetes, hypercholesterolemia, body mass index and smoking (adjusted model). Synergy index (S) and attributable proportion (AP) were estimated as measures of biological interaction. RESULTS: Elevated concentrations of sIL6R (>75th percentile value) were associated with an increased occurrence of MI (compared to ≤75th percentile), with an adjusted OR of 1.4 (95% CI, 1.1-1.8). Very high (>90th percentile value) levels of sgp130 were associated with a reduced occurrence of MI [OR 0.7 (95% CI, 0.5-0.9)] (adjusted). There was an indication of a possible interaction between high sIL6R and low sgp130 (adjusted S score 1.7, 95% CI = 0.5-6.1; AP 0.19, 95% CI = -0.2-0.5), suggesting that low sgp130 levels may synergize with high sIL6R levels to increase risk of MI. CONCLUSIONS: sIL6R and sgp130 had opposing associations with MI. Indeed, circulating sgp130 levels may modify the association of elevated sIL6R levels with MI.

Analysis of the role of interleukin 6 receptor haplotypes in the regulation of circulating levels of inflammatory biomarkers and risk of coronary heart disease.

Variants at the interleukin 6 receptor (IL6R) gene regulate inflammation and are associated with risk of coronary heart disease (CHD). The aim of the present study was to investigate the effects of IL6R haplotypes on circulating levels of inflammatory biomarkers and risk of CHD. We performed a discovery analysis in SHEEP, a myocardial infarction (MI) case control study (n = 2,774) and replicated our results in two large, independent European populations, PROCARDIS, a CHD case control study (n = 7,998), and IMPROVE (n = 3,711) a prospective cardiovascular cohort study. Two major haplotype blocks (rs12083537A/G and rs4075015A/T--block 1; and rs8192282G/A, rs4553185T/C, rs8192284A/C, rs4240872T/C and rs7514452T/C--block 2) were identified in the IL6R gene. IL6R haplotype associations with C-reactive protein (CRP), fibrinogen, IL6, soluble IL6R (sIL6R), IL6, IL8 and TNF-α in SHEEP, CRP and fibrinogen in PROCARDIS and CRP in IMPROVE as well as association with risk of MI and CHD, were analyzed by THESIAS. Haplotypes in block 1 were associated neither with circulating inflammatory biomarkers nor with the MI/CHD risk. Haplotypes in block 2 were associated with circulating levels of CRP, in all three study populations, with fibrinogen in SHEEP and PROCARDIS, with IL8 and sIL6Rin SHEEP and with a modest, non significant, increase (7%) in MI/CHD risk in the three populations studied. Our results indicate that IL6R haplotypes regulate the circulating levels of inflammatory biomarkers. Lack of association with the risk of CHD may be explained by the combined effect of SNPs with opposite effect on the CHD risk, the sample size as well as by structural changes affecting sIL6R stability in the circulation.