Genetic and environmental influences on IL-6 and TNF-alpha plasma levels in apparently healthy general population

Quantile-Dependent Expressivity of Serum Interleukin-6 Concentrations as a Possible Explanation of Gene-Disease Interactions, Gene-Environment Interactions, and Pharmacogenetic Effects

Interleukin 6 (IL-6) is a moderately heritable pleiotropic cytokine whose elevated concentrations in coronary artery disease, peripheral arterial disease, pulmonary arterial hypertension, Eales' disease, Sjògren's syndrome, osteoarthritis, adenocarcinoma, neuroblastoma, polymyalgia rheumatica, pulmonary tuberculosis, and enterovirus 71 infection, and following coronary artery bypass graft show larger genetic effects than in unaffected low IL-6 controls. We hypothesize that genetic effects may depend upon whether average IL-6 concentrations are high or low, i.e., quantile-dependent expressivity. Quantile-specific offspring-parent (β_OP) and full-sib regression slopes (β_FS) were estimated by applying quantile regression to the age- and sex-adjusted serum IL-6 concentrations in families surveyed in the Framingham Heart Study. Quantile-specific heritabilities were calculated as h² = 2β_OP / (1 + r_spouse) and h² = {(1 + 8r_spouseβ_FS)^0.5 -1} / (2r_spouse)). Heritability (h² ± SE) of IL-6 concentrations increased from 0.01 ± 0.01 at the 10th percentile (NS), 0.02 ± 0.01 at the 25th (P = 0.009), 0.03 ± 0.01 at the 50th (P = 0.007), 0.04 ± 0.02 at the 75th (P = 0.004), and 0.13 ± 0.05 at the 90th percentile (P = 0.03), or 0.0005 ± 0.0002 for each 1% increase in the offspring's phenotype distribution (P_{linear trend} = 0.02) when estimated from β_OP and from 0.02 ± 0.02 at the 10th (NS), 0.02 ± 0.02 at the 25th (NS), 0.06 ± 0.02 at the 50th (P = 0.01), 0.12 ± 0.04 at the 75th (P = 0.001), and 0.30 ± 0.03 at the 90th percentile (P < 10^-16), or 0.0015 ± 0.0007 for each 1% increase in the sibling phenotype distribution (P_{linear trend} = 0.02) when estimated from β_FS. Thus the heritability of serum IL-6 concentrations is quantile dependent, which may contribute in part to the larger genetic effect size reported for diseases and environmental conditions that elevate IL-6 concentrations vis-à-vis unaffected controls.

Family-based analyses reveal novel genetic overlap between cytokine interleukin-8 and risk for suicide attempt

BACKGROUND

Suicide is major public health concern. It is imperative to find robust biomarkers so that at-risk individuals can be identified in a timely and reliable manner. Previous work suggests mechanistic links between increased cytokines and risk for suicide, but questions remain regarding the etiology of this association, as well as the roles of sex and BMI.

METHODS

Analyses were conducted using a randomly-ascertained extended-pedigree sample of 1882 Mexican-American individuals (60% female, mean age = 42.04, range = 18-97). Genetic correlations were calculated using a variance components approach between the cytokines TNF-α, IL-6 and IL-8, and Lifetime Suicide Attempt and Current Suicidal Ideation. The potentially confounding effects of sex and BMI were considered.

RESULTS

159 individuals endorse a Lifetime Suicide Attempt. IL-8 and IL-6 shared significant genetic overlap with risk for suicide attempt (ρg = 0.49, pFDR = 7.67 × 10-03; ρg = 0.53, pFDR = 0.01), but for IL-6 this was attenuated when BMI was included as a covariate (ρg = 0.37, se = 0.23, pFDR = 0.12). Suicide attempts were significantly more common in females (pFDR = 0.01) and the genetic overlap between IL-8 and risk for suicide attempt was significant in females (ρg = 0.56, pFDR = 0.01), but not in males (ρg = 0.44, pFDR = 0.30).

DISCUSSION

These results demonstrate that: IL-8 shares genetic influences with risk for suicide attempt; females drove this effect; and BMI should be considered when assessing the association between IL-6 and suicide. This finding represents a significant advancement in knowledge by demonstrating that cytokine alterations are not simply a secondary manifestation of suicidal behavior, but rather, the pathophysiology of suicide attempts is, at least partly, underpinned by the same biological mechanisms responsible for regulating inflammatory response.

Exploring correlation between bone metabolism markers and densitometric traits in extended families from Spain

Osteoporosis is a common multifactorial disorder characterized by low bone mass and reduced bone strength that may cause fragility fractures. In recent years, there have been substantial advancements in the biochemical monitoring of bone metabolism through the measurement of bone turnover markers. Currently, good knowledge of the genetics of such markers has become an indispensable part of osteoporosis research. In this study, we used the Genetic Analysis of Osteoporosis Project to study the genetics of the plasma levels of 12 markers related to bone metabolism and osteoporosis. Plasma phenotypes were determined through biochemical assays and log-transformed values were used together with a set of covariates to model genetic and environmental contributions to phenotypic variation, thus estimating the heritability of each trait. In addition, we studied correlations between the 12 markers and a wide variety of previously described densitometric traits. All of the 12 bone metabolism markers showed significant heritability, ranging from 0.194 for osteocalcin to 0.516 for sclerostin after correcting for covariate effects. Strong genetic correlations were observed between osteocalcin and several bone mineral densitometric traits, a finding with potentially useful diagnostic applications. In addition, suggestive genetic correlations with densitometric traits were observed for leptin and sclerostin. Overall, the few strong and several suggestive genetic correlations point out the existence of a complex underlying genetic architecture for bone metabolism plasma phenotypes and provide a strong motivation for pursuing novel whole-genome gene-mapping strategies.

Maternal and child cytokine relationship in early life is not altered by cytokine gene polymorphisms

The development of immune responses is influenced by the interaction between environmental and genetic factors. Our previous study showed a close association between maternal and young infant's cytokine responses. The question is how this association evolves over time and the contribution of genetic polymorphisms to this association. Five cytokines in mitogen-stimulated whole blood culture were measured from pregnant mothers and their children aged 2, 5, 12, 24 and 48 months. Cytokine gene polymorphisms were determined in both mothers and children. High production of maternal interleukin (IL)-10, tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) was significantly associated with higher levels of the corresponding cytokines in their children at 2 months (T2), but the association decreased over time. Maternal single-nucleotide polymorphism (SNP) in IFN-γ gene, rs3181032, was found to be associated with child's IFN-γ levels at T2 only, whereas maternal IL-10 rs4579758 and child's TNF-α rs13215091 were associated with child's corresponding cytokines at later ages but not at T2. In the final models including the gene polymorphisms, maternal cytokines were still the strongest determinant of child cytokines. Maternal cytokine during pregnancy, which could be a proxy for child's environmental factors, showed its highest impact at early age, with no or little influence from genetic factors.

Meta-analysis of the correlation between IL-6 -174 G/C polymorphism and polycystic ovarian syndrome

AIM

The correlation between interleukin-6 (IL-6) gene polymorphism and polycystic ovary syndrome (PCOS) has been reported, but the conclusions are controversial. The present study was aimed to evaluate the association between IL-6 -174 G/C polymorphism and susceptibility of PCOS by meta-analysis.

MATERIAL AND METHODS

A systematic search on Medline, Embase, CNKI, Wanfang Data and VIP databases containing Chinese and English studies was conducted electronically using specific eligibility criteria. Meta-analysis was performed using Review Manager 5.2 software after Hardy-Weinberg equilibrium test. Effect sizes of odds ratio and 95% confidence interval (CI) were calculated and combined appropriately. To verify the reliability of the results, subgroup analyses and sensitivity analyses were performed.

RESULTS

Four selected studies containing 351 cases and 464 control participants were included. The pooled odds ratio between IL-6 -174 G/C polymorphism and susceptibility of PCOS under allele (C/G), dominant (CC+GC/GG) and recessive (CC/GG+GC) models were 0.63 (95%CI, 0.41-0.96), 0.53 (95%CI, 0.26-1.08) and 0.67 (95%CI, 0.39-1.16), respectively. The result under allele model was unstable in sensitivity analysis. Subgroup analysis showed that the correlation between IL-6 -174 G/C polymorphism and susceptibility of PCOS was not statistically significant in the studies that conformed to the Hardy-Weinberg equilibrium.

CONCLUSION

IL-6 -174 G/C polymorphism may be not related to susceptibility of PCOS. Nevertheless, further studies with large samples and studies considering other single-nucleotide polymorphisms of the IL-6 gene are needed to confirm our findings.

Duffy antigen receptor genetic variant and the association with Interleukin 8 levels

The aim of this study is to identify loci associated with circulating levels of Interleukin 8 (IL8). We investigated the associations of 121,445 single nucleotide polymorphisms (SNPs) from the Illumina 200K CardioMetabochip with IL8 levels in 1077 controls from the Stockholm Heart Epidemiology Program (SHEEP) study, using linear regression under an additive model of inheritance. Five SNPs (rs12075A/G, rs13179413C/T, rs6907989T/A, rs9352745A/C, rs1779553T/C) reached the pre-defined threshold of genome-wide significance (p<1.0×10(-5)) and were tested for in silico replication in three independent populations, derived from the PIVUS, MDC-CC and SCARF studies. IL8 was measured in serum (SHEEP, PIVUS) and plasma (MDC-CC, SCARF). The strongest association was found with the SNP rs12075 A/G, Asp42Gly (p=1.6×10(-6)), mapping to the Duffy antigen receptor for chemokines (DARC) gene on chromosome 1. The minor allele G was associated with 15.6% and 10.4% reduction in serum IL8 per copy of the allele in SHEEP and PIVUS studies respectively. No association was observed between rs12075 and plasma IL8.

CONCLUSION

rs12075 was associated with serum levels but not with plasma levels of IL8. It is likely that serum IL8 represents the combination of levels of circulating plasma IL8 and additional chemokine liberated from the erythrocyte DARC reservoir due to clotting. These findings highlight the importance of understanding IL8 as a biomarker in cardiometabolic diseases.

Electrochemical bioassay for the detection of TNF-α using magnetic beads and disposable screen-printed array of electrodes

BACKGROUND

In this study we have developed an electrochemical bioassay for the analysis of TNF-α, coupling magnetic beads with disposable electrochemical platforms. TNF-α is a pro inflammatory cytokine that participates in the regulation of immune defense against various pathogens and the recovery from injury. It plays a central role in the development of many inflammatory diseases. The bioassay was based on a sandwich format using alkaline phosphatase as an enzymatic label and an eight-sensor screen-printed array as an electrochemical transducer.

RESULTS

The modified magnetic beads were captured by a magnet on the surface of each graphite working electrode of the array and the electrochemical detection was thus achieved through the addition of the alkaline phosphatase substrate (1-naphthylphosphate); 1-naphthol produced during the enzymatic reaction was detected using differential pulse voltammetry. The parameters influencing the different steps of the assay were optimized in order to reach the best sensitivity and specificity.

CONCLUSION

The proposed strategy offers great promise for analysis of clinical diagnostics, considering also that arrays allow the simultaneous analysis of different samples.

Interleukin-6 promoter polymorphisms and susceptibility to atrial fibrillation in elderly Han Chinese patients with essential hypertension

There is an accumulating body of evidence indicating a strong association between inflammation and the pathogenesis of atrial fibrillation (AF). Interleukin-6 (IL-6) is a pleiotropic cytokine, functions as a mediator of inflammatory response, and has both proinflammatory and anti-inflammatory properties. The aim of the present study was to investigate the association of the -634C/G polymorphism of the IL-6 gene with AF in elderly Han Chinese patients with essential hypertension (EH). A total of 169 elderly patients with EH were eligible for this study. Patients with AF (n=75) were allocated to the AF group, and 94 subjects without AF to the control group. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used to assess the genotype frequencies. The distribution of the IL-6 -634C/G genotypes (CC, CG, and GG) was 67.02%, 30.85%, and 2.13% in the controls, and 50.67%, 40.00%, and 9.33% in AF subjects, respectively (P=0.0312). The frequency of the G allele in the AF group was significantly higher than that in the control group (29.33% vs. 17.55%, P=0.0103). Compared with the CC and CG genotypes, the GG homozygote had a 4.7353-fold increased risk of AF [95% confidence interval (CI)=0.9537-23.5116, P=0.0382]. These findings suggest that the IL-6 -634C/G polymorphism is associated with AF, and the G allele has increased risk of AF in elderly Han Chinese patients with EH.

The Association of Interleukin 6−634C/G Polymorphism With Left Atrial Thrombus and Severe Spontaneous Echocontrast in Patients With Atrial Fibrillation

Atrial fibrillation (AF) not only is an independent risk factor for death but also confers significant risk of morbidity from stroke associated with left atrial thrombus. The association of interleukin 6 ( IL-6) polymorphism with thrombus in AF has not been investigated before. We carried out a case–control study in Han Chinese. The IL-6 −634C/G genotypes of 31 patients with thrombus and 45 patients without thrombus were detected by polymerase chain reaction and restriction fragment length polymorphism. The frequencies of the IL-6 genotypes (CC, CG, and GG) were 29.03%, 54.54%, and 16.13% for the patients with thrombus, and 55.56%, 40.00%, and 4.44% for the patients without thrombus, respectively ( P = .0391). Compared with the CC genotype, the G allele carriers (CG + GG) had a 2.79-fold increased risk of thrombus or severe spontaneous echocontrast (SEC). These results suggest that IL-6 −634C/G polymorphism is associated with thrombus and severe SEC, and the G allele is an independent risk for thrombus and severe SEC in Han Chinese patients with AF.

Effects of genetic variation on chromatin structure and the transcriptional machinery: analysis of the IL6 gene locus

The presence of functional regulatory polymorphism at the interleukin 6 (IL6) locus is uncertain, with many conflicting in vitro findings. To examine the in vivo effect of the three putative functional IL6 promoter variants, -174G>C, -572G>C and -6331T>C, two complementary techniques, allele-specific chromatin immunoprecipitation and allele-specific formaldehyde-assisted isolation of regulatory elements, were carried out using unrelated lymphoblast cell lines of known genotype. There were no allele-specific effects for all three single-nucleotide polymorphisms (SNPs) under basal conditions. Upon IL-1β stimulation, however, allele-specific effects were seen for the -6331 allele, which showed both increased RNA polymerase II loading (56%, P=0.001) and increased open chromatin (59%, P=0.004) for the T allele, which is in line with previous reports of this SNP and the effects from acute inflammation. These studies highlight the importance of examining chromatin under different environmental conditions when studying the functionality of regulatory polymorphisms.

The age-dependency of genetic and environmental influences on serum cytokine levels: a twin study

Previous epidemiologic studies have evaluated the use of immunological markers as possible tools for measuring ageing and predicting age-related pathology. The importance of both genetic and environmental influences in regulation of these markers has been emphasized. In order to further evaluate this relationship, the present study aims to investigate the relative influence of genetic and environmental factors on four key cytokines involved in the human immune response (Interleukin (IL)-1β, IL-6, IL-10 and Tumor Necrosis Factor (TNF)-α). In addition, the role of age as a possible moderator on these influences was evaluated.

METHODS

The study was conducted in 1603 females from the Twins UK registry, with mean age ± SD of 60.4 ± 12.2 years, including 863 monozygotic twins (385 pairs and 93 singletons) and 740 dizygotic twins (321 pairs and 98 singletons). Heritability was estimated using structural equation modeling. The role of age as a moderator was evaluated using gene-age interaction models.

RESULTS

Heritabilities were moderate for IL-1β (range: 0.27-0.32) and IL-10 (0.30) and low for IL-6 (range: 0.15-0.16) and TNF-α (range: 0.17-0.23). For IL-1β, heritability declines with age due to an increase in unique environmental factors. For TNF-α, heritability increases with age due to a decrease in unique environmental factors.

CONCLUSION

The current findings illustrate the importance of genetic and environmental influences on four cytokines involved in the human immune response. For two of these there is evidence that heritability changes with age owing to changes in environmental factors unique to the individual.

Polymorphisms of -174G>C and -572G>C in the interleukin 6 (IL-6) gene and coronary heart disease risk: a meta-analysis of 27 research studies

OBJECTIVE

Elevated serum IL-6 level is a risk factor for coronary heart disease (CHD). The -174 G>C and -572 G>C polymorphisms in the IL-6 gene have previously been shown to modulate IL-6 levels. But the association between the -174 G>C and -572 G>C polymorphisms and the risk of CHD is still unclear. A meta-analysis of all eligible studies was carried out to clarify the role of IL-6 gene polymorphisms in CHD.

METHODS AND RESULTS

PubMed, EMBASE, Vip, CNKI and CBM-disc were searched for eligible articles in English and Chinese that were published before October 2010. 27 studies involving 11580 patients with CHD and 17103 controls were included. A meta-analysis was performed for the included articles using the RevMan 5.0 and Stata 10.0 softwares. Overall, the -174 C allele was not significantly associated with CHD risk (ORs = 1.04, 95%CI = 0.98 to 1.10) when compared with the -174 G allele in the additive model, and meta-analysis under other genetic models (dominant, recessive, CC versus GG, and GC versus GG) also did not reveal any significant association. On the contrary, the -572 C allele was associated with a decreased risk of CHD when compared with the -572 G allele (ORs = 0.79, 95%CI = 0.68 to 0.93). Furthermore, analyses under the recessive model (ORs = 0.69, 95% = 0.59 to 0.80) and the allele contrast model (genotype of CC versus GG, ORs = 0.49, 95% = 0.35 to 0.70) yielded similar results. However, statistical significance was not found when the meta-analysis was restricted to studies focusing on European populations, studies with large sample size, and cohort studies by using subgroup analysis.

CONCLUSIONS

The -174 G>C polymorphism in the IL-6 gene is not significantly associated with increased risks of CHD. However, The -572 G>C polymorphism may contribute to CHD development. Future investigations with better study design and large number of subjects are needed.

Effects of aging and menopause on serum interleukin-6 levels and peripheral blood mononuclear cell cytokine production in healthy nonobese women

Inappropriate interleukin-6 production is thought to play a role in the development of several age-related conditions including atherosclerosis. This study aimed to determine whether aging affects circulating interleukin-6 (IL-6) levels. Healthy, nonobese women (n = 208, 44.5 ± 0.70 years, 22.4 ± 0.17 kg/m(2)) were categorized into four age groups (22-31, 32-41, 42-51, and 52-63 years; cross-sectional study). Cytokine levels in serum and those produced from peripheral blood mononuclear cell (PBMC) were measured. The oldest group had the highest circulating levels of IL-6 and oxidized low-density lipoprotein (ox-LDL) and higher PBMC production of IL-6, tumor necrosis factor-α (TNF-α), and interleukin-1 alpha (IL-1β). Additionally, significant interactions between age and menopause were found for serum IL-6 (P = 0.024), and TNF-α (P = 0.011) and IL-1β (P < 0.001) produced from PBMCs. Serum IL-6 levels positively correlated with age, waist-hip ratio (WHR), systolic blood pressure, circulating levels of TNF-α, IL-1β, and ox-LDL, and urinary 8-epi-prostaglandin F(2)α. Multiple stepwise regression models identified the following factors for contributing to serum IL-6 levels: serum IL-1β, menopause status, WHR, and serum TNF-α in mode I (R(2) = 0.302); serum IL-1β, age, serum TNF-α, and WHR (β = 0.197; P = 0.006) in model II (R(2) = 0.283). Sub-analysis was performed according to menopausal status. Serum IL-6 levels were positively associated with levels of IL-6, TNF-α, and IL-1β in PBMC supernatants (unstimulated) from postmenopausal women, whereas these were negatively associated in premenopausal women. In conclusion, circulating IL-6 levels may be interactively influenced by age and menopause. Additionally, estrogen deprivation after menopause may enhance PBMC cytokine production in postmenopausal women, resulting in increased IL-6 levels which are closely related to oxidative stress.

Factors associated with inflammation markers, a cross-sectional analysis

Epidemiological studies have reported associations between circulating inflammation markers and risk of chronic diseases. It is of interest to examine whether risk factors for these diseases are associated with inflammation. We conducted a cross-sectional analysis to evaluate whether reproductive and lifestyle factors and circulating vitamin D were associated with inflammation markers, including C-reactive protein, cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p40, IL-12p70, IL-13, TNFα), and cytokine modulators (IL-1RA, sIL-1RII, sIL-2Ra, sIL-4R, sIL-6R, sTNF-R1/R2), among 616 healthy women. We confirmed associations of several inflammation markers with age and BMI. We also observed significantly higher levels of certain inflammation markers in postmenopausal vs. premenopausal women (TNFα, sIL-1RII, sIL-2Ra), with increasing parity (IL-12p40), and with higher circulating 25(OH) vitamin D (IL-13) and lower levels among current users of non-steroidal anti-inflammatory drugs (NSAIDs) (IL-1β, IL-2, IL-10, IL-12p70, and IL-12p40), current smokers (IL-4, IL-13, IL-12p40), and women with a family history of breast or ovarian cancer (IL-4, IL-10, IL-13). Our findings suggest that risk factors for chronic diseases (age, BMI, menopausal status, parity, NSAID use, family history of breast and ovarian cancer, and smoking) are associated with inflammation markers in healthy women.

Pro-inflammatory cytokine levels in postmenopausal women with the metabolic syndrome

BACKGROUND

Prevalence of the metabolic syndrome (METS) and its components significantly increase after the menopause. Related increased cardiovascular risk may partially be explained by a pro-inflammatory state.

OBJECTIVE

To assess pro-inflammatory cytokine serum levels in postmenopausal women with and without the METS.

METHODS

Serum of 90 postmenopausal women who previously participated in a METS screening programme was analysed for tumour necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6). Cytokine levels were compared among those with and without the syndrome, and for each of its components. Linear relationships were also assessed between cytokine levels and several continuous variables including each diagnostic METS criteria and menopausal symptoms assessed with the Menopause Specific Quality of Life tool (MENQOL).

RESULTS

For all studied women mean age was 55.1 ± 7.3 years with 63.3% having abdominal obesity, 15.6% hyperglycaemia, 58.9% high triglycerides, 44.4% hypertension and 25.6% high total cholesterol levels. Women with the METS (n = 45) significantly had higher body mass index values, and higher rates of abdominal obesity, hyperglycaemia, hypertriglyceridemia, hypertension and lower HDL-C levels. Cytokine levels did not differ among women with or without the METS; however, independent of METS diagnosis those with abdominal obesity displayed significantly higher IL-6 levels and those with hypertension higher levels of both cytokines. Levels of both cytokines positively correlated with age and time since menopause, IL-6 positively correlating with waist circumference values and TNF-α positively with both systolic and diastolic blood pressure levels. A significant positive correlation was also found between the number of positive METS criteria (0-5) and both cytokine levels. Cytokine levels did not correlate with vasomotor and psycho-social MENQOL scores.

CONCLUSION

Pro-inflammatory cytokine levels in this postmenopausal series positively correlated with age, time since the menopause, abdominal circumference, blood pressures levels and the number of positive METS diagnostic criteria. There is a need for more research in this regard.

The G to A polymorphism at -597 of the interleukin-6 gene is extremely rare in southern Han Chinese

Interleukin-6 (IL-6) is a cytokine involved in different physiologic and pathophysiologic processes including essential hypertension (EH). Associations of the IL-6 promoter region polymorphisms with circulating level of IL-6 have been reported in various studies. We detected the IL-6-597G/A polymorphism in 246 EH patients and 194 healthy controls from Jiangsu area (south of China). Individuals all carried the GG wild genotype, no GA or AA genotypes were found. Our results suggest that IL-6-597G/A polymorphism is extremely rare and unlikely to be contributing significantly to disease susceptibility in southern Han Chinese.

Association between radiographic hand osteoarthritis and RANKL, OPG and inflammatory markers

OBJECTIVE

The aim of the study was to evaluate the association between prevalence and severity of radiographic hand osteoarthritis (OA) and serum levels of systemic inflammatory markers in a community-based population sample.

DESIGN

A cross-sectional observational study was conducted on a population comprised 1452 Chuvashians (763 males, aged 49.23 ± 17.43; and 689 females, aged 50.37 ± 17.47 years). OA was evaluated in 14 joints of each hand using Kellgren and Lawrence (K-L), joint space narrowing (JSN) and osteophyte (OS) scores. Serum levels of systemic inflammatory and osteoclastogenic cytokines were measured by an enzyme-linked immunosorbent assay (ELISA). Statistical analyses included descriptive statistics, correlation analysis and multiple linear regressions.

RESULTS

Monocyte chemotactic protein-1 (MCP-1) and osteoprotegerin (OPG) levels were associated with OA traits, but the statistically significant correlations were weak and/or moderate. In particular, the MCP-1 inflammation marker showed a statistically significant association with JSN (β=0.077, P=0.022) and OS (β=0.067, P=0.024) scores, but not with the number of affected joints (K-L ≥ 2). OPG was significantly correlated with the scores as to the number of affected joints (β=0.063, P=0.035) and OS (β=0.077, P=0.028). No significant associations were found between levels of other inflammatory [interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-17] and osteoclastogenic [receptor activator for nuclear factor κ B ligand (RANKL), macrophage colony-stimulating factor (M-CSF)] cytokines and OA characteristics.

CONCLUSIONS

This study strengthens the premise that OPG might be a valid biomarker of hand OA. Confirmation of these results in larger cohorts of patients will reinforce our theory that the RANKL/OPG pathway is a suitable target for developing novel agents against OA.

Preliminary evidence of an association between a functional interleukin-6 polymorphism and fatigue and sleep disturbance in oncology patients and their family caregivers

CONTEXT

Fatigue and sleep disturbance are common problems in oncology patients and their family caregivers (FCs). However, little is known about factors that contribute to interindividual variability in these symptoms or to their underlying biologic mechanisms.

OBJECTIVES

An evaluation was done on whether genetic variation in a prominent proinflammatory cytokine, interleukin-6 (IL-6 c.-6101A>T [rs4719714]), was associated with mean ratings of evening fatigue, morning fatigue, and sleep disturbance, as well as with the trajectories of these symptoms.

METHODS

Over six months, participants completed standardized measures of fatigue and sleep disturbance. Linear regression was used to assess the effect of the IL-6 genotype and other covariates on mean fatigue and sleep disturbance scores. Hierarchical linear modeling was used to determine the effect of the IL-6 genotype on symptom trajectories.

RESULTS

Common allele homozygotes reported higher levels of evening fatigue (P=0.003), morning fatigue (P=0.09), and sleep disturbance (P=0.003) than minor allele carriers. Predictors of baseline level and trajectories of evening fatigue included age, gender, and genotype (intercepts) and baseline level of evening fatigue (slope). Predictors of baseline level and trajectories of morning fatigue included age and genotype (intercept) and age and baseline level of morning fatigue (slope). Predictors of baseline level and trajectories of sleep disturbance included age and genotype (intercept) and baseline level of sleep disturbance (slope).

CONCLUSIONS

Findings provide preliminary evidence of a genetic association between a functional promoter polymorphism in the IL-6 gene and severity of evening fatigue, morning fatigue, and sleep disturbance in oncology patients and their FCs.

Relationship between circulating tumor necrosis factor system and bone mass before and after estrogen plus progestogen therapy

OBJECTIVE

The aim of his study was to investigate the relationship between the circulating tumor necrosis factor (TNF) system and bone mineral density (BMD) before and after estrogen plus progestogen therapy (EPT).

METHODS

Serum levels of TNF-alpha, TNF-beta, soluble TNF receptor (sTNFR) 1, sTNFR2, and bone turnover markers and BMDs at the lumbar spine and proximal femur were measured in 192 postmenopausal Korean women. Among all women, 70 were treated with sequential EPT for 1 year.

RESULTS

BMDs at all skeletal sites and bone turnover markers were not correlated with serum TNF and sTNFR. After adjustment for age, years since menopause, and body mass index, serum TNF-beta levels were significantly lower in osteoporotic women than in normal women, whereas serum levels of TNF-alpha and sTNFR did not differ among normal, osteopenic, and osteoporotic postmenopausal women. After 6 months of EPT, serum TNF-beta levels increased significantly (P < 0.05), whereas serum TNF-alpha, sTNFR1, and sTNFR2 levels were unchanged. The 1-year changes in BMD at the lumbar spine and proximal femur after EPT were not correlated with the basal levels of serum TNF-alpha and sTNFR and their changes 6 months after EPT.

CONCLUSIONS

In the circulating TNF system, only serum TNF-beta levels were lower in osteoporotic postmenopausal women compared with normal postmenopausal women and increased after EPT, but changes in circulating TNF and sTNFR after EPT had no association with changes in bone markers and BMD. The circulating TNF system may not be clinically useful for predicting BMD and bone response after EPT.

Variation in CHI3LI in relation to type 2 diabetes and related quantitative traits

Background

CHI3LI encoding the inflammatory glycoprotein YKL-40 is located on chromosome 1q32.1. YKL-40 is involved in inflammatory processes and patients with Type 2 Diabetes (T2D) have elevated circulating YKL-40 levels which correlate with their level of insulin resistance. Interestingly, it has been reported that rs10399931 (−329 G/A) of CHI3LI contributes to the inter-individual plasma YKL-40 levels in patients with sarcoidosis, and that rs4950928 (−131 C/G) is a susceptibility polymorphism for asthma and a decline in lung function. We hypothesized that single nucleotide polymorphisms (SNPs) or haplotypes thereof the CHI3LI locus might influence risk of T2D. The aim of the present study was to investigate the putative association between SNPs and haplotype blocks of CHI3LI and T2D and T2D related quantitative traits.

Methods/Principal Findings

Eleven SNPs of CHI3LI were genotyped in 6514 individuals from the Inter99 cohort and 2924 individuals from the outpatient clinic at Steno Diabetes Center. In cas-control studies a total of 2345 T2D patients and 5302 individuals with a normal glucose tolerance test were examined.

We found no association between rs10399931 (OR, 0.98 (CI, 0.88–1.10), p = 0.76), rs4950928 (0.98 (0.87–1.10), p = 0.68) or any of the other SNPs with T2D. Similarly, we found no significant association between any of the 11 tgSNPs and T2D related quantitative traits, all p>0.14. None of the identified haplotype blocks of CHI3LI showed any association with T2D, all p>0.16.

Conclusions/Significance

None of the examined SNPs or haplotype blocks of CHI3LI showed any association with T2D or T2D related quantitative traits. Estimates of insulin resistance and dysregulated glucose homeostasis in T2D do not seem to be accounted for by the examined variations of CHI3LI.

Pre-analytical and biological variability in circulating interleukin 6 in healthy subjects and patients with rheumatoid arthritis

Interleukin (IL)-6, a key player in the inflammatory response, may be a useful biomarker in rheumatoid arthritis (RA). The aim was to determine analytical variability, a reference interval in healthy subjects, and long- and short-term variation in serum and plasma IL-6 in healthy subjects and RA patients. An enzyme-linked immunosorbent assay from R&D was used for determination of serum and plasma IL-6. The IL-6 concentration did not depend on the type of anticoagulant used or the 3-h time delay between sampling and processing or repeated freeze-thaw cycles. The median plasma and serum IL-6 in 318 healthy subjects were 1.3 pg ml(-1) (range 0.33-26) and 1.4 pg ml(-1) (range 0.25-23), respectively. The median coefficient of variation in plasma IL-6 in 27 healthy subjects during 1 month, and repeated after 6 and 12 months were 27%, 31% and 26%, respectively. No significant long-term changes were observed in serum IL-6 over a 3-year period (14%, p = 0.33). Exercise (cycling) increased serum IL-6 in healthy subjects but not in RA patients. In conclusion, circulating IL-6 is stable regarding sample handling and shows little variation over time. Changes in IL-6 concentrations > 60% (2 times the biological variation) are likely to reflect changes in disease activity and not only pre-analytical or normal biological variability.

Cytokines and coronary artery disease: the state of the art

Initiation and progression of coronary atherosclerosis has been associated with inflammation and cytokines balance. The objective of this study is to understand the role of cytokines in the pathophysiology and management of coronary artery disease. Coronary artery disease has been revisited with revision of the pertinent published articles in the Medline, Scopus, and EBSCO Host research from 1987 to 2007. The 2 groups of cytokines (proinflammatory and anti-inflammatory) have been detected in human atherosclerotic plaques. The balance between the 2 groups may reflect the intensity of occult plaque inflammation and the vulnerability to rupture. Multiple studies have determined that a diverse set of proinflammatory biomarkers can furnish prognostic information beyond the traditional risk factors. Inflammatory responses after coronary revascularization are known to play key role in vascular lesion formation early in atherosclerosis and restenosis. Clinical utilization of cytokines remains promising yet incompletely explored and need more studies.

Genome-wide linkage analysis for circulating levels of adipokines and C-reactive protein in the Quebec family study (QFS)

Adipose tissue synthesizes and secretes a wide range of biologically active molecules considered as inflammatory markers whose dysregulation in obesity plays a role in the development of insulin resistance and vascular disorders. Thus, finding genes that influence circulating levels of inflammatory biomarkers may provide insights into the genetic determinants of obesity-related metabolic diseases. We performed linkage analyses for fasting plasma levels of adiponectin, C-reactive protein (CRP), interleukin-6 (IL-6) and tumor-necrosis factor-alpha (TNF-alpha) in 764 subjects enrolled in the Quebec family study (QFS). A maximum of 393 pairs of siblings from 211 nuclear families were available for analyses. A total of 443 markers spanning the 22 autosomal chromosomes with an average inter-marker distance of 6.24 Mb were genotyped. Linkage was tested using both allele-sharing (SIBPAL) and variance component linkage methods (MERLIN). We showed suggestive evidence of linkage for plasma adiponectin levels on chromosome 15q21.1 [D15S659; logarithm of the odds (LOD) score = 2.23], 3q13.33 (D3S3023; LOD = 2.09), 20q13.2 (D20S197; LOD = 1.96) and 14q32.2 (D14S1426; LOD = 1.79). Evidence of linkage (SIBPAL) was also found for CRP on 12p11.23 (P = 0.001) and 12q15 (P = 0.0005) and for IL-6 on 14q12 (P = 0.002). None of these linkages remained significant after adjustment for body mass index. No evidence of linkage was found for TNF-alpha plasma levels. These results suggest that several QTLs can influence plasma levels of adiponectin and CRP, partly via their effects on adiposity.

Association of serum interleukin-6 concentration with a functional IL6 -6331T>C polymorphism

BACKGROUND

Interleukin-6 (IL-6) concentrations vary substantially among individuals. This study aimed to identify novel genetic markers to explain these differences.

METHODS

We sequenced a region 6-kb upstream of the IL6 [interleukin 6 (interferon, beta 2)] transcription start site in a search for functional variants and detected 3 common variants: -6331T>C, -6101A>T, and -5617/-5616C/A>T/G. IL6 -6331T>C (C allele frequency, 0.20; 95% confidence interval, 0.16-0.24) showed strong negative linkage disequilibrium with -174G>C (D' = -0.97) and was studied further in 309 individuals who underwent coronary artery bypass grafting.

RESULTS

Patients with the TT genotype had higher IL-6 concentrations 6 h after surgery than those with the CC genotype (mean, 199.4 ng/L vs 114.9 ng/L; P = 0.02). A similar association was seen in a cohort of 173 patients who underwent intensive periodontal therapy: Individuals with the CC genotype had significantly lower IL-6 concentrations 24 h after therapy than TT patients (mean, 0.78 ng/L vs 5.00 ng/L; P < 0.0001). A similar trend was observed in 203 healthy individuals from northern Europe (1.29 ng/L for the TT genotype vs 0.89 ng/L for the CC genotype; P = 0.07). Reporter assays that used a sequence flanking the -6331 single-nucleotide polymorphism spliced upstream to the IL-6 minimal promoter driving luciferase gene expression demonstrated a 1.3-fold increase in promoter activity (P < 0.01) for constructs containing -6331T. Electrophoretic mobility shift assays revealed enhanced binding of transcription factor Oct-1 to the T allele.

CONCLUSIONS

IL6 -6331T is associated with increased IL-6 concentrations in an acute inflammatory state via a mechanism involving binding of the Oct-1 transcription factor. This finding may help resolve conflicting studies based on the IL6 -174G>C variant.

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

OBJECTIVE

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

RESEARCH DESIGN AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Une étude prospective de la prévalence du syndrome métabolique dans des familles françaises supposées saines

Metabolic syndrome (MS) is a cluster of synergistically interacting cardiovascular risk factors which may have serious consequences for the development of cardiovascular disease and diabetes. In this study, we aimed to estimate the prevalence of MS within presumably healthy French families of the STANISLAS cohort, and to observe biological parameters involved in cardiovascular diseases among the offspring of MS subjects. 371 apparently healthy families (1366 individuals) were examined at two visits with a five-year interval (t0 and t+5). MS prevalence was assessed among parents following the ATP-III definition. Our results show that MS is present in presumably healthy adults of the STANISLAS cohort and increases with age. Moreover, low HDL-C and TNF-alpha may play an important role in the development of MS in childhood, at least in our population. Therefore, a systematic tracking of MS appears to be all the more important as it will permit early management of MS in parents and the installation of efficient preventive measures in children including specific advice for diet and physical activity.

Genetic and environmental determinants of circulating resistin level in a community-based sample

OBJECTIVE

Resistin is a hormone secreted by adipose tissue, monocytes, bone marrow, and other tissues. It was also proclaimed as an important link between obesity and diabetes. The main objective of this study was to elucidate the contribution of a number of endogenous factors, such as sex, age, obesity characteristics, and genetic effects to the production of resistin in apparently healthy individuals. We also tested the possible relationships between circulating levels of resistin and other adipokines (leptin, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha)).

MEASUREMENTS

The plasma levels of studied adipokines were determined by enzyme-linked immunoassay in pedigree-based sample (n = 616), and subjected to model-based quantitative genetic analysis.

RESULTS

Resistin levels were significantly higher in women than in men (3.60 +/- 2.53 vs 3.15 +/- 2.48 ng/ml, P < 0.001), and varied independently of age in either sex. Statistical-genetic analysis revealed significant familial correlations (P < 0.01) for resistin. Adjusted for covariates, 66.38 +/- 10.28% of the resistin variation was attributable to putative genetic factors. A relatively small portion of the resistin variation (11.54 +/- 5.77%) was attributable to sharing a common household environment. The remaining variation, 22.12 +/- 17.69% was due to random environmental (i.e., unmeasured non-additive genetic) effects. The results of our analysis showed modest significant correlation of resistin with TNF-alpha and IL-6, and only in some groups; thus, while resistin was correlated with TNF-alpha in men, the correlation with IL-6 was significant only in the post-menopausal women group.

CONCLUSIONS

Our observations indicate that resistin is strongly influenced by genetic factors. The high heritability estimates for resistin concentrations clearly suggest the continuing need for further molecular genetic investigations.

Genetic and environmental determinants of variation of soluble adhesion molecules

In our research we examined the contribution of putative genetic sources on interindividual variation and cross-sectional correlations of several adhesion molecules, including intracellular (ICAM-1) and vascular cell adhesion molecules (VCAM-1) and E-selectin, in a population-based sample of ethnically homogeneous families of European origin. The plasma levels of these molecules were measured in 947 apparently healthy individuals from 217 nuclear families. Quantitative statistical-genetic analysis implementing the model fitting technique revealed significant parent/offspring and sibling correlations (p < 0.01) for all three molecules. The putative genetic effects explained 55.2 +/- 7.2% (VCAM-1), 63.3 +/- 7.5% (ICAM) and 63.8 +/- 8.1% (E-selectin) of the variation. Common family environmental factors also significantly influenced the variation of E-selectin (13%) and VCAM-1 (28.6%). The main results of our bivariate analysis showed that the observed phenotypic correlations between ICAM-1 and VCAM-1, and between ICAM-1 and E-selectin, were mostly attributable to shared environmental factors (r(E)= 0.896 and 0.737, respectively; p < 0.01). However, the correlation between VCAM-1 and E-selectin was likely caused by common genetic effects (r(G)= 0.334, p < 0.05). Our results show that familial clustering of adhesion molecules is likely due to strong genetic effects, supplemented with shared environmental factors.

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

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

Peripheral tissue release of interleukin-6 in patients with chronic kidney diseases: effects of end-stage renal disease and microinflammatory state

To examine if uremia influences muscle interleukin-6 (IL-6) metabolism we studied the exchange of IL-6 across the forearm in 16 patients with chronic kidney disease (CKD) (stages 3 and 4), in 15 hemodialysis (HD)-treated end-stage renal disease (ESRD) patients (n=15), and in six healthy controls. In addition, we performed an analysis of both IL-6 protein and IL-6 mRNA expression in muscle of CKD (stage 4) patients showing evidence of inflammation and in controls. A release of IL-6 from the forearm was observed in patients with elevated IL-6 plasma levels. Arterial IL-6 was directly related to released IL-6 (r=0.69; P<0.004) in HD patients. Both IL-6 protein and IL-6 mRNA expression were increased in muscle of inflamed CKD patients vs controls (P<0.05). Although muscle net protein balance was similar in all patients, it was significantly more negative in HD patients with high than in those with low IL-6 plasma levels (P<0.05). In addition, net protein balance was related to the forearm release of IL-6 in HD patients only (r=0.47; P<0.038). These data demonstrate that IL-6 expression is upregulated in muscle, and that muscle tissue, by releasing this cytokine, may contribute to the inflammatory response in HD patients. The release of IL-6 from peripheral tissues is associated with an increase in muscle protein loss in HD patients, suggesting that muscle release of IL-6 is linked to protein catabolism in these patients. The release of IL-6 from peripheral tissues may act as a signal for the inflammatory response and contribute to functional dysregulation in uremia.

Genetic and environmental determinants of circulating levels of angiogenin in community-based sample

BACKGROUND

Measurement of angiogenin in plasma provides important prognostic and diagnostic information in variety of malignancies and may even correlate with cancer's progression. Nevertheless, nowadays, specific physiological mechanisms of this protein action as well as major factors regulating its circulating levels normally and in pathology are still poorly understood. The main objectives of this study were to examine the contribution of a number of endogenous factors, such as sex, age, body size and genetic effects on the production of angiogenin in apparently healthy individuals, and to assess the correlations in circulating levels between angiogenin and other molecules involved in angiogenesis.

METHODS

The plasma levels of angiogenin and each of the additional cytokines [interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), macrophage-colony stimulating factor (M-CSF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), soluble intercellular adhesion molecule-1 (sICAM)] were determined by enzyme-linked immunoassay in a large family based sample.

RESULTS

Angiogenin levels were significantly higher in man than in women (360.64 +/- 104.04 ng/ml vs. 322.15 +/- 100.34 ng/ml, P < 0.01) and significantly correlated with age (P < 0.01) in both sexes. Genetic analysis showed that adjusted for potential covariates, 37.4 +/- 7.1% of angiogenin variation was attributable to putative genetic factors. The results of our study revealed that angiogenin concentrations were positively and significantly (P < 0.05) associated with sICAM, IL-6, TNF-alpha and M-CSF levels in the female cohort.

CONCLUSIONS

Our data provide reliable evidence for the substantial role of genetic factors in the determination of the phenotypic variability of angiogenin plasma levels. These findings of our study, including circulating angiogenin reference limits in healthy population and its correlation with angiogenic cytokines, may be of importance in determination of early stages of pathological angiogenesis.

A genetic basis for IFN-gamma production and T-bet expression in humans

Th1 and Th2 cytokines secreted by polarized effector T cells play a pivotal role in the development of autoimmune and allergic diseases. However, the genetic basis of cytokine production by T lymphocytes in humans is poorly understood. In this study, we investigated the genetic contribution to cytokine production and regulation of T cell-specific transcription factors in a prospective twin study. We found a substantial genetic contribution to the production of Th1 cytokines such as IFN-gamma and TNF-alpha with heritabilities of 0.85 (95% confidence intervals, 0.74-0.95) and 0.72 (0.50-0.93), respectively, whereas no genetic influence on production of the Th2 signature cytokine IL-4 was observed. Furthermore, the intrapair variability in IFN-gamma production by isolated T cells was lower in monozygotic than in dizygotic twins. In contrast to GATA-3, NFAT, and NF-kappaB, intrapair variability of T-bet, the master transcription factor of Th1 cells, was very low among monozygotic and high among dizygotic twins, indicative of a strong genetic influence on T-bet (heritability 0.93, 95% confidence interval, 0.84-1.0). Our data provide novel insights into the genetic regulation of human Th cell polarization. These data suggest that signature cytokines and cytokine signaling events of Th1 rather than Th2 cells are genetically determined and implicate that Th2-associated diseases in humans might be due to genetic variations in Th1 cytokine regulation via T-bet. This concept is highlighted by the recent finding that inactivation of the T-bet gene in mice results in development of clinical hallmark features of asthma.

Inter-individual variation of inflammatory markers of cardiovascular risks and diseases

Cardiovascular diseases are a real public health problem and have multifactorial origin. Full comprehension of these diseases is very difficult because of their clinical and biological heterogeneity. The best way to understand the development of these diseases is to first investigate each biological system involved in the diseases and secondly, interactions between them. Studying intermediate phenotype variation for these biological systems is a new and promising approach for their elucidation. Among these metabolic systems, inflammation is known to be implicated in the occurrence and worsening of cardiovascular diseases. For this review, we chose to report the most important results concerning environmental, genetic and epigenetic determinants that influence intermediate phenotypes (protein and RNA levels) of inflammation. Indeed, numerous studies have investigated these determinants in healthy populations, in other words, without the influence of either disease or medication. This new approach will help to better understand the regulation of these intermediate phenotypes and to identify a panel of risk markers, which may be useful in predicting and warning those at risk and in giving adequate treatment to each patient.

Genetic variation in selenoprotein S influences inflammatory response

Chronic inflammation has a pathological role in many common diseases and is influenced by both genetic and environmental factors. Here we assess the role of genetic variation in selenoprotein S (SEPS1, also called SELS or SELENOS), a gene involved in stress response in the endoplasmic reticulum and inflammation control. After resequencing SEPS1, we genotyped 13 SNPs in 522 individuals from 92 families. As inflammation biomarkers, we measured plasma levels of IL-6, IL-1beta and TNF-alpha. Bayesian quantitative trait nucleotide analysis identified associations between SEPS1 polymorphisms and all three proinflammatory cytokines. One promoter variant, -105G --> A, showed strong evidence for an association with each cytokine (multivariate P = 0.0000002). Functional analysis of this polymorphism showed that the A variant significantly impaired SEPS1 expression after exposure to endoplasmic reticulum stress agents (P = 0.00006). Furthermore, suppression of SEPS1 by short interfering RNA in macrophage cells increased the release of IL-6 and TNF-alpha. To investigate further the significance of the observed associations, we genotyped -105G --> A in 419 Mexican American individuals from 23 families for replication. This analysis confirmed a significant association with both TNF-alpha (P = 0.0049) and IL-1beta (P = 0.0101). These results provide a direct mechanistic link between SEPS1 and the production of inflammatory cytokines and suggest that SEPS1 has a role in mediating inflammation.

Contribution of the familial and genetic factors on monocyte chemoattractant protein-1 variation in healthy human pedigrees

Monocyte chemoattractant protein-1 (MCP-1) is a chemokine whose circulating levels have been detected in the lesions of several diseases such as pulmonary fibrosis, rheumatoid arthritis and atherosclerosis. However, the factors involved in the regulation of its production remain largely unknown. The main aim of the present paper was to ascertain the contribution of the familial/genetic factors on the production of MCP-1 in apparently healthy individuals. We also tested the possible relationships between the plasma levels of MCP-1 and other cytokines involved in bone metabolism (receptor activator NF-kB ligand (RANKL), osteoprotegerin (OPG), interleukin-6, macrophage-colony stimulating factor, tumor necrosis factor-alpha). Using ELISA assays the cytokine levels were measured in 570 apparently healthy individuals belonging to ethnically homogeneous Caucasian families. We found that MCP-1 levels were significantly (P<0.01) correlated with RANKL (in both sexes) and with OPG only in women. The study showed that adjusted for potential covariates, 72% of the MCP-1 variance, was attributable to familial effects. About 49% was due to potential genetic factors and the rest was explained by common environmental sources shared by spouses within each family. In conclusion, our data provide reliable evidence for the substantial role of genetic factors in the determination of the phenotypic variability of MCP-1 plasma levels. The association between the osteoclastogenic cytokines and MCP-1 levels in healthy pedigrees is of special interest and might shed light on MCP-1 involvement in bone remodeling.

Genome scan of systemic biomarkers of vascular inflammation in the Framingham Heart Study: evidence for susceptibility loci on 1q

Vascular inflammation plays a central role in atherosclerosis and inflammatory biomarkers predict risk of cardiovascular disease (CVD). Thus, finding genes that influence systemic levels of inflammatory biomarkers may provide insights into genetic determinants of vascular inflammation and CVD. We conducted variance-component linkage analyses of blood levels of four biomarkers of vascular inflammation [C-reactive protein (CRP), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), soluble intercellular adhesion molecule-1 (sICAM-1)] in 304 extended families from the Framingham Heart Study, using data from a 10cM genome scan. We computed p-values by a permutation approach. Heritability estimates ranged from 14% (IL-6) to 44% (MCP-1) after log transforming and adjusting for covariates. Significant linkage to MCP-1 was found on chromosome 1 (LOD=4.27 at 186cM; genome-wide p=0.005), in a region containing inflammatory candidate genes such as SELE, SELP (E- and P-selectin) and CRP. Other linkage peaks with LOD scores >2 were found for MCP-1 on chromosome 1 (LOD=2.04 at 16cM; LOD=2.34 at 70cM) and chromosome 17 (LOD=2.44 at 22cM) and for sICAM-1 on chromosome 1 at 229cM (LOD=2.09) less than 5cM from the interleukin-10 (IL10) gene. Multiple genes on chromosome 1 may influence inflammatory biomarker levels and may have a potential role in development of CVD.

Genetic epidemiology of skeletal system aging in apparently healthy human population

The study of our team was driven by a clinical problem of age-dependent chronic degenerative disease of skeleton that includes osteoporosis (OP) and osteoarthritis (OA)-related phenotypes. The major aims of the study included evaluation of the putative genetic factors determining the rate and pattern of the bone and cartilage loss and identification of the specific genes involved in this process. In addition, we examined genetic effects on circulating molecular factors involved in bone and cartilage metabolism. The skeletal phenotypes were assessed from hand radiographs, in total on about 1200 individuals belonging to ethnically homogeneous nuclear and complex three-generational pedigrees of European origin. The results obtained until now can be divided into three sections: (1) genetic analysis of bone mass/size/geometry characteristics (OP) and traits related to hand OA; (2) pedigree-based investigation of circulating levels of calciotropic hormones, growth factors, cytokines, and biochemical indices of bone and cartilage remodelling; (3) linkage and linkage disequilibrium study of several candidate genes, such as estrogen receptor alpha, collagen type I alpha 1, genes related to extracellular inorganic pyrophosphate transport and OP/OA phenotypes, including biochemical variables. The study provides compelling evidence to suggest strong involvement of the genetic factors in determination of variation of the majority of the examined OP- and OA-related phenotypes.

Detection of a single nucleotide polymorphism in the IL-6 promoter region of ancient nuclear DNA

In the current study a method was developed to examine the G/C single nucleotide polymorphism (SNP) at position -174 in the IL-6 promoter from nuclear DNA samples isolated from human skeletal remains from Manitoba, Canada, dating to as early as 3500 years ago. The IL-6 (-174) SNP was detected in three ancient samples and determined, as expected, in three out of three to be homozygous G/G. The analysis of cytokine SNPs of ancient nuclear DNA may provide novel insights into the genetic basis of autoimmune diseases and the susceptibility/resistance to infectious agents.

Biological variations, genetic polymorphisms and familial resemblance of TNF-α and IL-6 concentrations: STANISLAS cohort

Cytokines are involved in the development of several inflammatory diseases and atherosclerosis. Their variations in healthy individuals are not well defined. The aims of this study were: firstly, to identify factors affecting biological variation of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha); secondly, to study their family resemblance; and thirdly, to evaluate the effect of two TNF-alpha (-308G/A and -238G/A) and two IL-6 polymorphisms (174G/C and -572G/C) on their corresponding circulating levels. A total of 171 healthy families selected from the STANISLAS cohort were studied. Age was negatively related to TNF-alpha concentrations in offspring only (both sons and daughters). Additionally, IL-6 and TNF-alpha levels were differently influenced by gender, white blood cells, tobacco consumption, and HDL-cholesterol level. A weak significant familial resemblance for TNF-alpha concentration was observed in siblings only. There was no significant familial resemblance for IL-6 levels. The TNF-alpha -308A allele was associated with decreased TNF-alpha concentrations in both offspring aged less than 18 and males without overweight (BMI<25 kg/m(2)). Fathers carrying the IL-6 -174CC genotype had higher IL-6 levels than those with the IL-6 -174G allele. Parents with the IL-6 -572GG genotype had higher IL-6 concentrations than the C allele carriers. In this sample of healthy families, plasma levels of IL-6 and TNF-alpha were differently affected by biological parameters including age, gender and smoking, and the impact of their respective polymorphisms was influenced by gender, age and BMI.

Genetic influence on inflammation variables in the elderly

BACKGROUND

Inflammation variables (C-reactive protein [CRP], fibrinogen, and soluble intercellular adhesion molecule-1 [sICAM-1]) have been identified as risk factors for cardiovascular disease. It is still not known how much the regulation of inflammatory risk factors is determined by genetic factors, and the aim of this study was to determine the heritability of these inflammation variables and of the acute phase regulating cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) at older ages.

METHODS AND RESULTS

The heritability of CRP, fibrinogen, sICAM-1, IL-6, and TNF-alpha was determined in a twin study consisting of 129 monozygotic twin pairs and 153 dizygotic same-sex twins aged 73 to 94 years who participated in the Longitudinal Study of Aging of Danish Twins. Furthermore, we determined the influence of selected genetic polymorphisms on the plasma level variations. Genetic factors accounted for 20% to 55% of the variation in plasma levels of the inflammation variables. The highest heritability was found for sICAM-1. The genetic polymorphisms we studied explained only a small, insignificant part of the heritability.

CONCLUSIONS

This study in elderly twins provides evidence for a substantial genetic component of inflammatory cardiovascular risk factors among the elderly.

Tumor necrosis factor-alpha-induced apoptosis of human coronary artery endothelial cells: modulation by the peroxisome proliferator-activated receptor-gamma ligand pioglitazone

The cytokine tumor necrosis factor-alpha (TNF-alpha) plays an important role in endothelial injury, which is associated with the release of reactive oxygen species and the induction of apoptosis. We report on our study of TNF-alpha-induced apoptosis in human coronary artery endothelial cells and its modulation by the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand pioglitazone. Treatment of cells with TNF-alpha (40 ng/mL) resulted in apoptosis as measured by DNA laddering and caspase-3 activation. TNF-alpha treatment decreased the expression of antiapoptotic protein Bcl-2 (P <.05 vs control), but not the expression of Fas or FLIP, in human coronary artery endothelial cells. Treatment of cells with TNF-alpha also enhanced lipid peroxidation (P <.01 vs control). Pretreatment of cells with the PPAR-gamma ligand pioglitazone blocked TNF-alpha-mediated apoptosis, caspase-3 activation, expression of Bcl-2, and lipid peroxidation (P <.01 vs TNF-alpha alone). These results indicate that TNF-alpha induces oxidative stress in human coronary artery endothelial cells, resulting in apoptosis through a reduction in Bcl-2 expression and the subsequent activation of caspase-3. The PPAR-gamma ligand pioglitazone modulates lipid peroxidation, alters Bcl-2 expression and caspase-3 activation, and finally reduces apoptosis. The antioxidant and antiapoptotic effects of pioglitazone may be the mechanism by which this agent reduces endothelial injury.

Evidence for a Proinflammatory and Proteolytic Environment in Plaques From Endarterectomy Segments of Human Carotid Arteries

Objectives Based on previous observations on apolipoprotein(a), apo(a), in human unstable carotid plaques, we explored whether in the inflammatory environment of human atheroma, proteolytic events affect other hepatic and topically generated proteins in relation to the issue of plaque stability.

Methods and Results Forty unstable and 24 stable plaques from endarterectomy segments of affected human carotid arteries were extracted with buffered saline (PBS) and then 6 mol/L guanidine-hydrochloride (GdHCl) to identify loosely and tightly bound products, respectively. The extracts were studied before and after ultracentrifugation at d 1.21 g/mL. In the extracts, the concentrations of interleukin (IL)-6, −8, and −18 were significantly higher in the unstable plaques and correlated to those of MMP-2 and MMP-9. By Western blots, both apoB and apo(a) were highly fragmented and mostly present in the d 1.21 bottom that also contained fragments of apoE (10 and 22 kDa), decorin, biglycan, and versican. Fragmentation was higher in the unstable plaques. In baseline plasmas, concentrations of lipids, lipoproteins, and ILs did not differ between patients with unstable and stable plaques.

Conclusions In unstable and to a lesser extent in stable plaques, there is a proinflammatory and proteolytic microenvironment with the generation of fragments with potential pathobiological significance that requires investigation.