Genetic influence on inflammation variables in the elderly

Heritability of carotid intima-media thickness and inflammatory factors of atherosclerosis in a Chinese population

Carotid intima-media thickness (cIMT), a marker of subclinical atherosclerosis, has been found to be associated with incident stroke. High-sensitivity C-reactive protein (CRP) and fibrinogen have been demonstrated to be associated with atherosclerosis. Previous studies on heritability estimates of IMT, CRP, and fibrinogen among Chinese populations are limited. This study aims to estimate the heritability of these risk factors in residents who participated in the Taichung Community Health Study (TCHS) and their family members. A total of 2671 study subjects from 805 families were enrolled in the study, selected from a random sample of TCHS participants and their family members. CRP, and fibrinogen were obtained from each participant, and a questionnaire interview was conducted. cIMT was measured by high-resolution B-mode ultrasound and expressed as the mean of the maximum. Heritability estimates and the familial correlation of cIMT, CRP, and fibrinogen among family pairs were determined with SAGE software. With multivariate adjustments, significant heritability was found for cIMT (h2 = 0.26, P < 0.001), CRP (h2 = 0.34, P < 0.001), and fibrinogen (h2 = 0.48, P < 0.001). The intrafamilial correlation coefficients for the three indexes in the parent-offspring pairs were significant (P < 0.001) and ranged from 0.17 to 0.41. The full sibship correlations were also significant (P < 0.001) for the three indexes and ranged from 0.19 to 0.47. This study indicates that a moderate proportion of the variability in CRP, fibrinogen, and cIMT can be attributed to genetic factors in Chinese populations. The findings suggest that CRP is associated with cIMT, whereas no significant association exists between fibrinogen and cIMT.

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 (βOP) and full-sib regression slopes (βFS) 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 = 2βOP / (1 + rspouse) and h2 = {(1 + 8rspouseβFS)0.5 -1} / (2rspouse)). 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 (Plinear trend = 0.02) when estimated from βOP 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 (Plinear trend = 0.02) when estimated from βFS. 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.

Quantile-specific heritability of plasma fibrinogen concentrations

Background

Fibrinogen is a moderately heritable blood protein showing different genetic effects by sex, race, smoking status, pollution exposure, and disease status. These interactions may be explained in part by “quantile-dependent expressivity”, where the effect size of a genetic variant depends upon whether the phenotype (e.g. plasma fibrinogen concentration) is high or low relative to its distribution.

Purpose

Determine whether fibrinogen heritability (h²) is quantile-specific, and whether quantile-specific h² could account for fibrinogen gene-environment interactions.

Methods

Plasma fibrinogen concentrations from 5689 offspring-parent pairs and 1932 sibships from the Framingham Heart Study were analyzed. Quantile-specific heritability from offspring-parent (β_OP, h² = 2β_OP/(1+r_spouse)) and full-sib regression slopes (β_FS, h² = {(1+8r_spouseβ_FS)^0.05–1}/(2r_spouse)) were robustly estimated by quantile regression with nonparametric significance assigned from 1000 bootstrap samples.

Results

Quantile-specific h² (±SE) increased with increasing percentiles of the offspring’s age- and sex-adjusted fibrinogen distribution when estimated from β_OP (P_trend = 5.5x10^-6): 0.30±0.05 at the 10^th, 0.37±0.04 at the 25^th, 0.48±0.05 at the 50^th, 0.61±0.06 at the 75^th, and 0.65±0.08 at the 90^th percentile, and when estimated from β_FS (P_trend = 0.008): 0.28±0.04 at the 10^th, 0.31±0.04 at the 25^th, 0.36±0.03 at the 50^th, 0.41±0.05 at the 75^th, and 0.50±0.06 at the 90^th percentile. The larger genetic effect at higher average fibrinogen concentrations may contribute to fibrinogen’s greater heritability in women than men and in Blacks than Whites, and greater increase from smoking and air pollution for the FGB -455G>A A-allele. It may also explain greater fibrinogen differences between: 1) FGB -455G>A genotypes during acute phase reactions than usual conditions, 2) GTSM1 and IL-6 -572C>G genotypes in smokers than nonsmokers, 3) FGB -148C>T genotypes in untreated than treated diabetics, and LPL PvuII genotypes in macroalbuminuric than normoalbuminuric patients.

Conclusion

Fibrinogen heritability is quantile specific, which may explain or contribute to its gene-environment interactions. The analyses do not disprove the traditional gene-environment interpretations of these examples, rather quantile-dependent expressivity provides an alternative explanation that warrants consideration.

Quantile-Specific Heritability of Inflammatory and Oxidative Stress Biomarkers Linked to Cardiovascular Disease

PURPOSE

Heritability (h2 , the proportion of the phenotypic variance attributable to additive genetic effects) is traditionally assumed to be constant throughout the distribution of the phenotype. However, the heritabilities of circulating C-reactive protein, interleukin-6, plasminogen activator inhibitor type-1 (PAI-1), and monocyte chemoattractant protein-1 (MCP-1) concentrations depend upon whether the phenotype is high or low relative to their distributions (quantile-dependent expressivity), which may account for apparent gene-environment interactions. Whether the heritabilities of other inflammatory biomarkers linked to cardiovascular disease are quantile-dependent remain to be determined.

PATIENTS AND METHODS

Quantile-specific offspring-parent (βOP) and full-sib regression slopes (βFS) were estimated by applying quantile regression to the age- and sex-adjusted phenotypes of families surveyed as part of the Framingham Heart Study. Quantile-specific heritabilities were calculated as: h2 =2βOP/(1+rspouse) and h2 ={(1+8rspouseβFS)0.5-1}/(2rspouse).

RESULTS

Heritability (h2 ± SE) of lipoprotein-associated phospholipase A2 (Lp-PLA2) mass concentrations increased from 0.11 ± 0.03 at the 10th percentile, 0.08 ± 0.03 at the 25th, 0.12 ± 0.03 at the 50th, 0.20 ± 0.04 at the 75th, and 0.26 ± 0.06 at the 90th percentile, or 0.0023 ± 0.0006 per each one-percent increase in the phenotype distribution (Plinear trend= 0.0004). Similarly, h2 increased 0.0029 ± 0.0011 (Plinear trend= 0.01) for sP-selectin, 0.0032 ± 0.0009 (Plinear trend= 0.0001) for soluble intercellular adhesion molecule 1 (sICAM-1), and 0.0026 ± 0.0006 for tumor necrosis factor receptor 2 (TNFR2) (Plinear trend= 5.0 × 10-6) per each one-percent increase in their distributions when estimated from βOP. Osteoprotegerin and soluble ST2 heritability also increased significantly with increasing percentiles of their distributions when estimated from βFS. Lp-PLA2 activity, CD40 ligand, TNFα, interleukin-18, and myeloperoxidase heritability showed no significant quantile-dependence.

CONCLUSION

The heritabilities of circulating Lp-PLA2-mass, sP-selectin, sICAM-1, TNFR2, osteoprotegerin and soluble ST2 concentrations are quantile-dependent, which may contribute to purported genetic modulations of: 1) sP-selectin's relationships to venous thrombosis, pulmonary hypertension, type 2 diabetes and atorvastatin treatment; 2) sICAM-I's relationships to brain abscess and atorvastatin treatment; and 3) Lp-PLA2's relationships to myocardial infarction and preeclampsia.

Sexual Dimorphism in Innate Immunity: The Role of Sex Hormones and Epigenetics

Sexual dimorphism refers to differences between biological sexes that extend beyond sexual characteristics. In humans, sexual dimorphism in the immune response has been well demonstrated, with females exhibiting lower infection rates than males for a variety of bacterial, viral, and parasitic pathogens. There is also a substantially increased incidence of autoimmune disease in females compared to males. Together, these trends indicate that females have a heightened immune reactogenicity to both self and non-self-molecular patterns. However, the molecular mechanisms driving the sexually dimorphic immune response are not fully understood. The female sex hormones estrogen and progesterone, as well as the male androgens, such as testosterone, elicit direct effects on the function and inflammatory capacity of immune cells. Several studies have identified a sex-specific transcriptome and methylome, independent of the well-described phenomenon of X-chromosome inactivation, suggesting that sexual dimorphism also occurs at the epigenetic level. Moreover, distinct alterations to the transcriptome and epigenetic landscape occur in synchrony with periods of hormonal change, such as puberty, pregnancy, menopause, and exogenous hormone therapy. These changes are also mirrored by changes in immune cell function. This review will outline the evidence for sex hormones and pregnancy-associated hormones as drivers of epigenetic change, and how this may contribute to the sexual dimorphism. Determining the effects of sex hormones on innate immune function is important for understanding sexually dimorphic autoimmune diseases, sex-specific responses to pathogens and vaccines, and how innate immunity is altered during periods of hormonal change (endogenous or exogenous).

Association of CRP genetic variation with symptomatology, cognitive function, and circulating proinflammatory markers in civilian women with PTSD

BACKGROUND

Posttraumatic stress disorder (PTSD) has been associated with increased inflammation. C-reactive protein (CRP) is a marker of systemic inflammation, and recently, single nucleotide polymorphisms (SNPs) in the CRP gene have been associated with increased blood CRP protein levels and illness severity in PTSD patients. However, the mechanism by which the CRP SNPs are involved in PTSD remains unclear. Here we investigated the association of CRP genetic variation with blood proinflammatory protein levels, symptomatology, and cognitive function, and further explored the moderating effect of childhood maltreatment history, in adult patients with PTSD.

METHODS

Fifty-seven Japanese civilian women with PTSD and 73 healthy control women were enrolled. Three SNPs in the CRP gene, namely rs2794520, rs1130864, and rs3093059, were genotyped, and analyses focused on rs2794520 (T/C). Serum levels of high-sensitivity CRP (hsCRP), high-sensitivity tumor necrosis factor-α (hsTNF-α), and interleukin-6 were measured. PTSD symptoms were evaluated by the Posttraumatic Diagnostic Scale. Cognitive function was assessed by the Repeatable Battery for the Assessment of Neuropsychological Status. Childhood maltreatment history was assessed by the Childhood Trauma Questionnaire.

RESULTS

Patients with the rs2794520 CC/CT genotype, compared to those with the TT genotype, showed significantly higher levels of hsCRP (p=0.009) and hsTNF-α (p=0.001), more severe PTSD symptoms (p=0.036), and poorer cognitive function (p=0.018). A two-way analysis of variance revealed a significant genotype-by-maltreatment interaction for more severe PTSD avoidance symptom (p=0.012).

LIMITATIONS

The relatively small sample size limited our findings.

CONCLUSIONS

These findings may provide an insight into the etiology of PTSD from the inflammatory perspective.

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.

Genetic Variants Associated with Cancer Pain and Response to Opioid Analgesics: Implications for Precision Pain Management

OBJECTIVE

To review the current knowledge on the association of genetic variants with cancer pain.

DATA SOURCES

Data-based publications and review articles retrieved from PubMed, CINAHL, and Web of Science, as well as an additional search in Google Scholar.

CONCLUSION

Genetic variability can influence differential pain perception and response to opioids in cancer patients, which will have implications in the optimal personalized treatment of cancer pain. More studies are warranted to replicate findings.

IMPLICATIONS FOR NURSING PRACTICE

Nurses are poised to educate patients on biomarker testing and interpretation and to use precision pain management strategies based on this information.

Joint effect of gene-physical activity and the interactions among CRP, TNF-α, and LTA polymorphisms on serum CRP, TNF-α levels, and handgrip strength in community-dwelling elders in Taiwan - TCHS-E

This study assesses interactions of tumor necrosis factor α (TNF-α) gene polymorphisms with C-reactive protein (CRP) or lymphotoxin α (LTA) gene on serum CRP and TNF-α levels and handgrip strength. Eleven single nucleotide polymorphisms (SNPs), including rs2794520, rs1205, rs1130864, rs1800947, and rs3093059 in CRP; rs1799964, rs1800629, and rs3093662 in TNF-α; and rs2239704, rs909253, and rs1041981 in LTA, were genotyped in 472 unrelated elders (mean age 73.8 years). Among elders with TNF-α rs1799964 AA genotype, adjusted mean difference for handgrip strength decreased by -2.60 (-4.82, -0.38) and -2.51 kg (-4.75, -0.28) for LTA rs909253 and rs1041981 in women and by -2.39 kg (-3.98, -0.81) for CRP rs3093059 in men. Among elders with TNF-α rs1799964 AA genotype, adjusted mean ratios for hs-CRP levels increased by 2.32 (1.38, 3.90) and 2.27 (1.35, 3.84) for both CRP rs909253 and rs1041981 in women. The A-A-C LTA haplotype was associated with TNF-α levels that were 1.55 times higher than those of the C-G-A haplotype (P = 0.005). The joint effects of SNPs (the rs1800947 or rs3093059 of CRP, rs1799964 or rs1800629 of TNF-α, and rs909253 or rs1041981 of LTA) and physical inactivity appeared to have greater magnitude of decreased handgrip strength than main effects of these SNPs and physical inactivity. Our data showed that significant interactions of TNF-αrs1799964 and LTA rs909253 were observed. Moreover, joint effects of these CRP, TNF-α, and LTA risk alleles with physical inactivity in elders were observed, suggesting that physical activity may modulate effects of genotypes on handgrip strength.

Postpartum Circulating Markers of Inflammation and the Systemic Acute-Phase Response After Early-Onset Preeclampsia

Preeclampsia is an inflammatory-mediated hypertensive disorder of pregnancy and seems to be an early indicator of increased cardiovascular risk, but mechanisms underlying this association are unclear. In this study, we identified levels of circulating inflammatory markers and dynamic changes in the systemic acute-phase response in 44 women with a history of severe early-onset preeclampsia, compared with 29 controls with only uneventful pregnancies at 1.5 to 3.5 years postpartum. Models used were in vivo seasonal influenza vaccination and in vitro whole-blood culture with T-cell stimulants and the toll-like receptor-4 ligand lipopolysaccharide. Outcome measures were C-reactive protein, interleukin-6 (IL-6), IL-18, fibrinogen, myeloperoxidase, and a panel of 13 cytokines representative of the innate and adaptive inflammatory response, in addition to established cardiovascular markers. The in vivo acute-phase response was higher for women with previous preeclampsia than that for controls without such a history, although only significant for C-reactive protein (P=0.04). Preeclampsia was associated with higher IL-1β (P<0.05) and IL-8 (P<0.01) responses to T-cell activation. Hierarchical clustering revealed 2 distinct inflammatory clusters associated with previous preeclampsia: an adaptive response cluster associated with increased C-reactive protein and IL-6 before and after vaccination, increased weight, and low high-density lipoprotein cholesterol; and a toll-like receptor-4 mediated the cluster associated with increased IL-18 before and after vaccination but not associated with other cardiovascular markers. Furthermore, we found interactions between previous preeclampsia, common TLR4 gene variants, and the IL-18 response to vaccination. In conclusion, preeclampsia is associated with alterations in the inflammatory response postpartum mostly independent of other established cardiovascular risk markers.

Genetic and environmental determinants of population variation in interleukin-6, its soluble receptor and C-reactive protein: insights from identical and fraternal twins

Interleukin-6 and C-reactive protein are commonly assessed biomarkers linked to illness, obesity, and stressful life events. However, relatively little is known about their heritability. By comparing Caucasian twins from the Midlife in the US project (MIDUS), we estimated the heritability of IL-6, its soluble receptor, and CRP. Based on the hypothesis that adiposity might contribute more to IL-6 than to sIL-6r, we fit heritability models quantifying the extent to which each reflected genetic and environmental factors shared with obesity. Genetic influences on IL-6 and its receptor proved to be distinct. Further, the appearance of a heritable basis for IL-6 was mediated largely via shared paths with obesity. Supporting this conclusion, we confirmed that when unrelated adult controls are carefully matched to twin participants on BMI, age, gender and socioeconomic indices, their IL-6 is similar to the corresponding twins. In contrast, the effect of BMI on CRP was split between shared genetics and environmental influences. In conclusion, IL-6 is strongly affected by factors associated with obesity accounting for its lability and responsiveness to diet, life style and contemporaneous events.

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.

Genetic and environmental influences on the prospective correlation between systemic inflammation and coronary heart disease death in male twins

OBJECTIVE

Because of lack of evidence, we aimed to examine to what degree low-grade systemic inflammation and coronary heart disease (CHD) death shared common genetic and environmental substrates.

APPROACH AND RESULTS

From the 41-year prospective National Heart, Lung, and Blood Institute Twin Study, we included 950 middle-aged male twins at baseline (1969-1973). Low-grade systemic inflammation was measured with plasma levels of interleukin-6 (IL-6) and C-reactive protein. Univariate and bivariate structural equation models were used, adjusted for a risk score for CHD death. The score-adjusted heritability was 19% for IL-6, 27% for C-reactive protein, and 22% for CHD death. The positive phenotypic correlation of IL-6 with CHD death (radjusted=0.27; 95% confidence interval [CI], 0.08-0.43) was driven by additive genetic factors (contribution [relative contribution], 0.30 [111%]) but attenuated by unique environment (-0.03 [-11%]). The genetic correlation between IL-6 and CHD death was 0.74 (95% CI, 0.21-1.00), whereas the unique environmental correlation was -0.05 (95% CI, -0.35 to 0.25). The proportion of genetic variance for CHD death shared with that for IL-6 was 74%. The phenotypic correlation of C-reactive protein with CHD death (radjusted=0.10; 95% CI, -0.02 to 0.22) was explained by additive genetic factors (0.20 [149%]) but was attenuated by the unique environment (-0.09 [-49%]). The genetic correlation of C-reactive protein with CHD death was 0.63 (95% CI, -0.07 to 1.00), whereas the unique environmental correlation was -0.07 (95% CI, -0.29 to 0.17).

CONCLUSIONS

Low-grade systemic inflammation, measured by IL-6, and long-term CHD death share moderate genetic substrates that augment both traits.

TNF-α, IL6, and IL10 polymorphisms and the effect of physical exercise on inflammatory parameters and physical performance in elderly women

High levels of inflammatory mediators are associated with reduced physical capabilities and muscle function in the elderly. Single nucleotide polymorphisms (SNPs) may affect the expression and synthesis of these molecules, thus influencing the intensity of the inflammatory response and susceptibility to certain diseases. Physical exercise may attenuate age-related chronic inflammation and improve physical performance. This study evaluated the interaction between the SNP rs1800629 in TNF-α, rs1800795 in IL6, and rs1800896 in IL10 and the effect of physical exercise on physical performance and inflammation in elderly women. There was a significant interaction between rs1800629 and the effect of exercise on physical performance and between the combined 3-SNP genotype and changes in physical performance in response to exercise. These SNPs did not influence the effect of exercise on inflammatory parameters. Elderly women with a combination of genotypes associated with an anti-inflammatory profile (low TNF-α and IL-6 production, high IL-10 production) showed better physical performance independent of exercise modality, evidence of an interactive influence of genetic and environmental factors on improving physical performance in elderly women.

Novel gene variants predict serum levels of the cytokines IL-18 and IL-1ra in older adults

Activation of inflammatory pathways measured by serum inflammatory markers such as interleukin-18 (IL-18) and interleukin-1 receptor antagonist (IL-1ra) is strongly associated with the progression of chronic disease states in older adults. Given that these serum cytokine levels are in part a heritable trait, genetic variation may predict increased serum levels. Using the Cardiovascular Health Study and InCHIANTI cohorts, a genome-wide association study was performed to identify genetic variants that influence IL-18 and IL-1ra serum levels among older adults. Multiple linear regression models characterized the association between each SNP and log-transformed cytokine values. Tests for multiple independent signals within statistically significant loci were performed using haplotype analysis and regression models conditional on lead SNP in each region. Multiple SNPs were associated with these cytokines with genome-wide significance, including SNPs in the IL-18-BCO gene region of chromosome 2 for IL-18 (top SNP rs2250417, P=1.9×10(-32)) and in the IL-1 gene family region of chromosome 2 for IL-1ra (rs6743376, P=2.3×10(-26)). Haplotype tests and conditional linear regression models showed evidence of multiple independent signals in these regions. Serum IL-18 levels were also associated with a region on chromosome 2 containing the NLRC4 gene (rs12989936, P=2.7×10(-19)). These data characterize multiple robust genetic signals that influence IL-18 and IL-1ra cytokine production. In particular, the signal for serum IL-18 located on chromosome two is novel and potentially important in inflammasome triggered chronic activation of inflammation in older adults. Replication in independent cohorts is an important next step, as well as molecular studies to better understand the role of NLRC4.

Genetic Architecture of the Pro-Inflammatory State in an Extended Twin-Family Design

In this study we examined the genetic architecture of variation in the pro-inflammatory state, using an extended twin-family design. Within the Netherlands Twin Register Biobank, fasting Tumor Necrosis Factor-α (TNF-α), Interleukin-6 (IL-6), C-Reactive Protein (CRP), and fibrinogen levels were available for 3,534 twins, 1,568 of their non-twin siblings, and 2,227 parents from 3,095 families. Heritability analyses took into account the effects of current and recent illness, anti-inflammatory medication, female sex hormone status, age, sex, body mass index, smoking status, month of data collection, and batch processing. Moderate broad-sense heritability was found for all inflammatory parameters (39%, 21%, 45%, and 46% for TNF-α, IL-6, CRP and fibrinogen, respectively). For all parameters, the remaining variance was explained by unique environmental influences and not by environment shared by family members. There was no resemblance between spouses for any of the inflammatory parameters, except for fibrinogen. Also, there was no evidence for twin-specific effects. A considerable part of genetic variation was explained by non-additive genetic effects for TNF-α, CRP, and fibrinogen. For IL-6, all genetic variance was additive. This study may have implications for future genome-wide association studies by setting a clear numerical target for genome-wide screens that aim to find genetic variants regulating the levels of these pro-inflammatory markers.

Variability in the immune system: of vaccine responses and immune states

System-wide approaches are now being applied to study vaccine responses, whose mechanisms of action, and failure, are not well understood. These works have repeatedly shown vaccine response to be an orchestrated process involving multiple arms of immunity most noticeable sensing and innate components. Prediction of vaccine responses based on system-wide measures is achievable, but challenges remain for robust population wide predictions based only on pre-vaccination measures, especially in partially efficacious vaccines such as influenza. This is especially true in older adults, who are often less responsive to vaccination and exhibit high level of variation compared to young in many components of immunity. Despite this increase in variation, most of the studies on aging use group averages of immune phenotypes to model immune system behavior. Using systems approaches, it is possible to exploit this variation to form distinguishable clusters of phenotypes within and across individuals to discover underlying immune states.

Aging and airway inflammation

BACKGROUND

Since little is known of airways inflammation in the elderly, we have carried out a study to explore the presence of some inflammatory markers in the airways of healthy subjects of different ages using a non-invasive method which is particularly suitable for aged people.

OBJECTIVE

The aim of this work was to investigate whether parameters, including (1) pH, IL-8 and TNF-α in exhaled breath condensate (EBC), (2) exhaled nitric oxide levels (NO), and (3) inflammatory cell profile in induced sputum, are age-related.

MATERIALS AND METHODS

Thirty healthy adults (10 subjects below the age of 30 [A], 10 subjects between 30 and 60 years [B], and 10 subjects over 60 years of age [C]), were enrolled in the study. IL-8 and TNF-α levels were measured in breath condensate. Exhaled pH was measured after deaeration/decarbonation by means of a pH-meter. A rapid-response chemiluminescence NO analyzer was used to quantify NO. Induced sputum was collected, homogenized with dithiothreitol, and cytospins for differential cell were produced.

RESULTS

The levels of IL-8 and TNF-α in EBC, the levels of exhaled NO, and the percentage of neutrophils in induced sputum were significantly elevated in C and B compared with A; the EBC pH level was significantly reduced in C and B compared with A. The EBC levels of IL-8, TNF-α, pH, the level of exhaled NO, and the percentage of neutrophils correlated significantly with age.

CONCLUSION

This study has shown the presence of age-related airways inflammation in healthy subjects.

Interaction between cytokine gene polymorphisms and the effect of physical exercise on clinical and inflammatory parameters in older women: study protocol for a randomized controlled trial

Background

Aging is associated with chronic low-grade inflammatory activity with an elevation of cytokine levels. An association between regular physical activity and reduction of blood levels of anti-inflammatory cytokines is demonstrated in the literature pointing to an anti-inflammatory effect related to exercise. However, there is no consensus regarding which type of exercise and which parameters are the most appropriate to influence inflammatory markers. Evidence indicates that the single nucleotide polymorphism (SNP) can influence the synthesis of those cytokines affecting their production.

Methods/Design

The design of this study is a randomized controlled trial. The aim of this study is to investigate the interaction between the cytokine genes SNP and the effect of physical activity on older women. The main outcomes are: serum levels of sTNFR-1, sTNFR-2, interleukin (IL)-6, IL-10, measured by the ELISA method; genotyping of tumor necrosis factor- (TNF)-alpha (rs1800629), IL6 (rs1800795), IL10 (rs1800896) by the TaqMan Method (Applied Biosystems, Foster City, CA, USA); and physical performance assessed by Timed Up and Go and 10-Meter Walk Tests. Secondary outcomes include: Geriatric Depression Scale, Perceived Stress Scaleand aerobic capacity, assessed by the six-minute walk; and lower limb muscle strength, using an isokinetic dinamometer (Biodex Medical Systems, Inc., Shirley, NY,USA). Both exercise protocols will be performed three times a week for 10 weeks, 30 sessions in total.

Discussion

Investigating the interaction between genetic factors and exercise effects of both protocols of exercise on the levels of inflammatory cytokine levels can contribute to guide clinical practice related to treatment and prevention of functional changes due to chronic inflammatory activity in older adults. This approach could develop new perspectives on preventive and treatment proposals in physical therapy and in the management of the older patient.

Trial registration

(ReBEC) RBR9v9cwf

Blood fibrinogen as a biomarker of chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is a multicomponent condition that is characterised by airflow obstruction that is not fully reversible and is a major global cause of morbidity and mortality. The most widely used marker of disease severity and progression is FEV₁. However, FEV₁ correlates poorly with both symptoms and other measures of disease progression and thus there is an urgent need for other biological markers to better characterise individuals with COPD. Fibrinogen is an acute phase plasma protein that has emerged as a promising biomarker in COPD. Here we review the current clinical evidence linking fibrinogen with COPD and its associated co-morbidities and discuss its potential utility as a biomarker.

Methods

Searches for appropriate studies were undertaken on PubMed using search terms fibrinogen, COPD, emphysema, chronic bronchitis, FEV₁, cardiovascular disease, exacerbation and mortality.

Results

There is strong evidence of an association between fibrinogen and the presence of COPD, the presence and frequency of exacerbations and with mortality. Fibrinogen is associated with disease severity but does not predict lung function decline, a measure used as a surrogate for disease activity. The role of fibrinogen in identifying inflammatory co morbidities, particularly cardiovascular disease, remains unclear. Fibrinogen is reduced by p38 mitogen-activated protein kinase inhibitors in individuals with stable disease and by oral corticosteroids during exacerbations.

Conclusions

Fibrinogen is likely to be a useful biomarker to stratify individuals with COPD into those with a high or low risk of future exacerbations and may identify those with a higher risk of mortality.

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.

Associations between inflammatory markers, candidate polymorphisms and physical performance in older Danish twins

Inflammation may play an essential role in the decline of physical performance. In this study we investigated the associations between inflammatory markers, candidate polymorphisms and physical performance in elderly people. Plasma levels of TNF-α, IL-6, CRP, fibrinogen, sICAM-1 and candidate polymorphisms were measured in 600 twin individuals aged 73 years and older participating in the Longitudinal Study of Aging Danish Twins. Physical performance was assessed using a self-reported measure. The inclusion of twins allowed both traditional and within-twin-pair analysis which permitted control for shared environment and genetic factors. Higher levels of inflammatory markers were generally associated with a lower level of physical performance. The TNFα-238G/A polymorphism was significantly associated with physical performance in men, with A allele carriers having significantly better performance than GG homozygotes. However, this gene variation seems to have only a minor role in explaining the associations between the levels of inflammatory markers and physical performance. When using twin pair analysis to test whether genetic factors in general account for this association, results showed that the association between the level of fibrinogen and physical performance could be caused by genetic factors. Also the association between the level of TNF-α and physical performance in males could be caused by genetic factors. However, other gene variations than the candidate gene polymorphisms studied here seem to explain the major part of the genetic proportion of this association.

Serum C-reactive protein concentrations in healthy Miniature Schnauzer dogs

BACKGROUND

C-reactive protein (CRP) is a sensitive marker for inflammation in people and dogs. In people, an association between CRP concentration and atherosclerosis has been reported. Atherosclerosis is rare in dogs, but the Miniature Schnauzer breed may be at increased risk for developing this vascular disease. It is not known if CRP concentrations in Miniature Schnauzer dogs differ from those in other dog breeds.

OBJECTIVES

Our objectives were to validate an automated human CRP assay for measuring CRP in dogs and compare CRP concentrations in healthy Miniature Schnauzer dogs with those in non-Miniature Schnauzer breeds.

METHODS

Sera from 37 non-Miniature Schnauzer dogs with inflammatory disease were pooled and used to validate a human CRP immunoturbidimetric assay for measuring canine CRP. Blood was collected from 20 healthy Miniature Schnauzer dogs and 41 healthy dogs of other breeds. Median serum CRP concentration of healthy Miniature Schnauzer dogs was compared with that of healthy non-Miniature Schnauzer dogs.

RESULTS

The human CRP assay measured CRP reliably with linearity between 0 and 20 mg/L. CRP concentration for healthy Miniature Schnauzer dogs (median 4.0 mg/L, minimum-maximum 0-18.2 mg/L) was significantly higher than for the healthy non-Miniature Schnauzer dogs (median 0.1 mg/L, minimum-maximum 0-10.7 mg/L); 17 of the 20 Miniature Schnauzer dogs had values that overlapped with those of the non-Miniature Schnauzer dogs.

CONCLUSIONS

Median CRP concentration of Miniature Schnauzer dogs was slightly higher than that of other breeds of dogs. A relationship between higher CRP concentration in Miniature Schnauzer dogs and idiopathic hyperlipidemia, pancreatitis, and possible increased risk for atherosclerosis remains to be determined.

Associations of gene sequence variation and serum levels of C-reactive protein and interleukin-6 with Alzheimer's disease and dementia

Inflammatory mechanisms have been implicated in Alzheimer's disease (AD) and dementia. We therefore sought to study DNA sequence variation and serum levels of the potent inflammatory mediators Interleukin-6 (IL6) and C-reactive protein (CRP) in relation to AD and dementia. Tagging single nucleotide polymorphisms (tagSNPs) were chosen to capture most variation in and around CRP and IL6 in 3937 elderly Swedish men and women (1,265 AD cases). A sub-set of the population (n = 723) with serum measurements of CRP and IL6 was included in 1) a nested case-control study of incident dementia cases, and 2) a case-control study of prevalent dementia cases. None of the SNPs or haplotypes was significantly associated with AD or dementia after correcting for multiple testing nor were elevated baseline levels of hsCRP or IL6 (measured on average 4.3 years before dementia onset) significantly associated with risk of future AD or dementia. However, prevalent AD cases had higher levels of IL6 (measured on average 5.5 years after dementia onset) than age- and gender-matched controls, OR 2.24 (95% CI 1.27-3.95), p-value 0.006. In summary, this data suggests that AD patients have an altered immune profile with higher circulating levels of IL6 than age- and gender-matched controls. However, neither variation in the CRP and IL6 genes nor circulating levels of their respective protein products were associated with an increased risk of developing late-life dementias.

Effect of the rs2259816 polymorphism in the HNF1A gene on circulating levels of c-reactive protein and coronary artery disease (the ludwigshafen risk and cardiovascular health study)

Background

C-reactive protein is a well established marker of inflammation and has been used to predict future cardiovascular disease. It is still controversial if it plays an active role in the development of cardiovascular disease. Recently, polymorphisms in the gene for HNF1α have been linked to the levels of C-reactive protein and coronary artery disease.

Methods

We investigated the association of the rs2259816 polymorphism in the HNF1A gene with the circulating level of C-reactive protein and the hazard of coronary artery disease in the LURIC Study cohort.

Results

Compared to CC homozygotes, the level of C-reactive protein was decreased in carriers of at least one A-allele. Each A-allele decreased CRP by approximately 15%. The odds ratio for coronary artery disease was only very slightly increased in carriers of the A-allele and this association did not reach statistical significance.

Conclusions

In the LURIC Study cohort the A-allele of rs2259816 is associated with decreased CRP but not with coronary artery disease.

Relationship between cytokine gene single nucleotide polymorphisms and symptom burden and quality of life in lung cancer survivors

BACKGROUND

Previous research has demonstrated that many lung cancer survivors report difficulties with symptom control and experience a poor quality of life (QOL). Although recent studies have suggested a relationship of single nucleotide polymorphisms (SNPs) in several cytokine genes with cancer susceptibility and prognosis, associations with symptom burden and QOL have not been examined. The current study was conducted to identify SNPs related to symptom burden and QOL outcomes in lung cancer survivors.

METHODS

All participants were enrolled in the Mayo Clinic Lung Cancer Cohort following diagnosis of lung cancer. A total of 1149 Caucasian lung cancer survivors completed questionnaires and had genetic samples available. The main outcome measures were symptom burden as measured by the Lung Cancer Symptom Scale and health-related QOL as measured by the Short-Form General Health Survey.

RESULTS

Twenty-one SNPs in cytokine genes were associated with symptom burden and QOL outcomes. Our results suggested both specificity and consistency of cytokine gene SNPs in predicting outcomes.

CONCLUSIONS

These results provide support for genetic predisposition to QOL and symptom burden and may aid in identification of lung cancer survivors at high risk for symptom management and QOL difficulties.

Low innate production of interleukin-1beta and interleukin-6 is associated with the absence of osteoarthritis in old age

OBJECTIVE

We investigated whether innate differences in cytokine response were associated with the absence of osteoarthritis (OA) in old age.

DESIGN

In 82 participants from a cross-sectional birth cohort, radiographs of hands, hips and knees were taken at the age of 90 years. OA was defined as a Kellgren-Lawrence score of at least two. "Free from OA" was defined at patient level as absence of hip and knee OA, and presence of OA in maximally two hand joints. The innate cytokine response was determined in whole-blood samples upon stimulation with lipopolysaccharide. Logistic regression analyses were used to investigate associations between absence of OA in relation to tertiles of interleukin (IL)-1beta, IL-6, tumor necrosis factor (TNF)-alpha, IL-1 receptor antagonist (RA) and IL-10. Adjustments were made for gender and body mass index.

RESULTS

Sixteen percent of the participants were "free from OA". Subjects in the lowest tertile of Il-1beta production had a 11-fold increased chance to be free of OA [odds ratio (OR) 11.3, confidence intervals (CI) 95% 1.1-115.9], subjects in the lowest tertile of IL-6 production had an almost 7-fold increased chance to be free of OA (OR 6.7, 95% CI 1.1-41.2). Absence of hand OA was associated with low innate production of IL-6 and IL-1RA, absence of hip OA was associated with low innate IL-1beta production. No associations were found for TNF-alpha and IL-10.

CONCLUSIONS

Low innate capacity to produce the pro-inflammatory cytokines IL-1beta and IL-6 is associated with the absence of OA in old age.

Genetic effects on postprandial variations of inflammatory markers in healthy individuals

Circulating levels of inflammatory markers predict the risk of cardiovascular disease (CVD), mediated perhaps in part by dietary fat intake, through mechanisms only partially understood. To evaluate post-fat load changes in inflammatory markers and genetic influences on these changes, we administered a standardized high-fat meal to 838 related Amish subjects as part of the Heredity and Phenotype Intervention (HAPI) Heart Study and measured a panel of inflammatory markers, including C-reactive protein (CRP), interleukin-1beta (IL-1beta), matrix metalloproteinase-1 and -9 (MMP-1 and MMP-9), and white blood cell (WBC) count, before and 4 h after fat challenge (CRP prechallenge only). Heritabilities (h(2) +/- s.d.) of basal inflammatory levels ranged from 16 +/- 8% for MMP-9 (P = 0.02) to 90 +/- 7% for MMP-1 (P < 0.0001). Post-fat load, circulating levels of WBC, MMP-1, and MMP-9 increased by 16, 32, and 43% (all P < 0.0001), with no significant changes in IL-1beta. Postprandial changes over the 4-h period were modestly heritable for WBC (age- and sex-adjusted h(2) = 14 +/- 9%, P = 0.04), but the larger MMP-1 and MMP-9 changes appeared to be independent of additive genetic effects. These results reveal that a high-fat meal induces a considerable inflammatory response. Genetic factors appear to play a significant role influencing basal inflammatory levels but to have minimal influence on post-fat intake inflammatory changes.

High habitual dietary alpha-linolenic acid intake is associated with decreased plasma soluble interleukin-6 receptor concentrations in male twins

BACKGROUND

alpha-Linolenic acid (ALA) is associated with a low risk of cardiovascular disease; however, the underlying mechanism is not completely known.

OBJECTIVE

The objective was to examine whether habitual dietary ALA intake is associated with plasma concentrations of inflammatory biomarkers after control for shared genetic and common environmental factors.

DESIGN

We cross-sectionally studied 353 middle-aged male twins. Habitual diet was assessed with the Willett food-frequency questionnaire. Fasting plasma concentrations of interleukin-6 (IL-6) and its soluble receptor (sIL-6R), high-sensitivity C-reactive protein (hsCRP), and tumor necrosis factor-alpha (TNF-alpha) were measured. Linear mixed-effect regression analysis was used to partition the overall association into within- and between-pair associations.

RESULTS

A 1-g increment in habitual dietary ALA intake was associated with 11.0% lower concentrations of sIL-6R (P = 0.004) but not of IL-6 (P = 0.31), TNF-alpha (P = 0.16), or hsCRP (P = 0.36) after adjustment for energy intake, nutritional factors, known cardiovascular disease risk factors, and medications. After further control for shared genetic and common environmental factors by comparison of brothers within a twin pair, a twin with a 1-g higher ALA intake was likely to have 10.9% (95% CI: 3.7%, 17.6%; P = 0.004) lower sIL-6R concentrations than his co-twin with a low intake, whereas ALA intake was not significantly associated with plasma concentrations of IL-6, TNF-alpha, or hsCRP. These results were validated by using 1000 bootstrap samples.

CONCLUSIONS

Habitual dietary ALA intake is inversely associated with plasma sIL-6R concentrations independent of shared genetic and common environmental influences. Lowering sIL-6R may be a mechanism underlying the cardioprotective properties of habitual dietary ALA. This study was registered at clinicaltrials.gov as NCT00017836.

Metabolic syndrome-related composite factors over 5 years in the STANISLAS family study: genetic heritability and common environmental influences

BACKGROUND

We estimated genetic heritability and common environmental influences for various traits related to metabolic syndrome in young families from France.

METHODS

At entrance and after 5 years, nineteen traits related to metabolic syndrome were measured in a sample of families drawn from the STANISLAS study. In addition, 5 aggregates of these traits were identified using factor analysis.

RESULTS

At entrance, genetic heritability was high (20 to 44%) for plasma lipids and lipoproteins, uric acid, fasting glucose, and the related clusters "risk lipids" and "protective lipids". Intermediate or low genetic heritability (less than 20%) was shown for triglycerides, adiposity indices, blood pressure, hepatic enzyme activity, inflammatory makers and the related clusters: "liver enzymes", "adiposity/blood pressure" and "inflammation". Moreover, common environmental influences were significant for all the parameters. With regard to 5-year changes, polygenic variance was low and not statistically significant for any of the individual variables or clusters whereas shared environment influence was significant.

CONCLUSIONS

In these young families, genetic heritability of metabolic syndrome-related traits was generally lower than previously reported while the common environmental influences were greater. In addition, only shared environment contributed to short-term changes of these traits.

Interaction between fibrinogen and IL-6 genetic variants and associations with cardiovascular disease risk in the Cardiovascular Health Study

The inflammatory cytokine interleukin-6 (IL-6) is a main regulator of fibrinogen synthesis, though its interaction with fibrinogen genes (FGA, FGB, FGG) and subsequent impact on cardiovascular disease (CVD) risk is not well-studied. We investigated joint associations of fibrinogen and IL6 tagSNPs with fibrinogen concentrations, carotid intima-media thickness, and myocardial infarction or ischemic stroke in 3900 European-American Cardiovascular Health Study participants. To identify combinations of genetic main effects and interactions associated with outcomes, we used logic regression. We also evaluated whether the relationship between fibrinogen SNPs and fibrinogen level varied by IL-6 level using linear regression models with multiplicative interaction terms. Combinations of fibrinogen and IL6 SNPs were significantly associated with fibrinogen level (p < 0.005), but not with other outcomes. Fibrinogen levels were higher in individuals having FGB1437 (rs1800790) and lacking FGA6534 (rs6050) minor alleles; these SNPs interacted with IL6 rs1800796 to influence fibrinogen level. Marginally significant (p= 0.03) interactions between IL-6 level and FGA and FGG promoter SNPs associated with fibrinogen levels were detected. We identified potential gene-gene interactions influencing fibrinogen levels. Although IL-6 responsive binding sites are present in fibrinogen gene promoter regions, we did not find strong evidence of interaction between fibrinogen SNPs and IL6 SNPs or levels influencing CVD.

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.

Inflammation and stress-related candidate genes, plasma interleukin-6 levels, and longevity in older adults

Interleukin-6 (IL-6) is an inflammatory cytokine that influences the development of inflammatory and aging-related disorders and ultimately longevity. In order to study the influence of variants in genes that regulate inflammatory response on IL-6 levels and longevity, we screened a panel of 477 tag SNPs across 87 candidate genes in >5000 older participants from the population-based Cardiovascular Health Study (CHS). Baseline plasma IL-6 concentration was first confirmed as a strong predictor of all-cause mortality. Functional alleles of the IL6R and PARP1 genes were significantly associated with 15%-20% higher baseline IL-6 concentration per copy among CHS European-American (EA) participants (all p<10(-4)). In a case/control analysis nested within this EA cohort, the minor allele of PARP1 rs1805415 was nominally associated with decreased longevity (p=0.001), but there was no evidence of association between IL6R genotype and longevity. The PARP1 rs1805415--longevity association was subsequently replicated in one of two independent case/control studies. In a pooled analysis of all three studies, the "risk" of longevity associated with the minor allele of PARP1 rs1805415 was 0.79 (95%CI 0.62-1.02; p=0.07). These findings warrant further study of the potential role of PARP1 genotype in inflammatory and aging-related phenotypes.

The relation of genetic and environmental factors to systemic inflammatory biomarker concentrations

BACKGROUND

Environmental and genetic correlates of inflammatory marker variability are incompletely understood. In the family-based Framingham Heart Study, we investigated heritability and candidate gene associations of systemic inflammatory biomarkers.

METHODS AND RESULTS

In offspring participants (n=3710), we examined 11 inflammatory biomarkers (CD40 ligand, C-reactive protein, intercellular adhesion molecule-1, interleukin-6, urinary isoprostanes, monocyte chemoattractant protein-1, myeloperoxidase, P-selectin, tumor necrosis factor-alpha, tumor necrosis factor receptor II, fibrinogen). Heritability and bivariate genetic and environmental correlations were assessed by Sequential Oligogenic Linkage Analysis routines in 1012 family members. We examined 1943 tagging single-nucleotide polymorphisms in 233 inflammatory pathway genes with >or=5 minor allele carriers using a general genetic linear model. Clinical correlates explained 2.4% (CD40 ligand) to 28.5% (C-reactive protein) of the variability in inflammatory biomarkers. Estimated heritability ranged from 10.9% (isoprostanes) to 44.8% (P-selectin). Most correlations between biomarkers were weak although statistically significant. A total of 45 single-nucleotide polymorphism-biomarker associations met the q-value threshold of 0.25. Novel top single-nucleotide polymorphisms were observed in ICAM1 gene in relation to intercellular adhesion molecule-1 concentrations (rs1799969, P=1.32 x 10(-8)) and MPO in relation to myeloperoxidase (rs28730837, P=1.9 x 10(-5)). Lowest P values for trans-acting single-nucleotide polymorphisms were observed for APCS with monocyte chemoattractant protein-1 concentrations (rs1374486, P=1.01 x 10(-7)) and confirmed for IL6R with interleukin-6 concentrations (rs8192284, P=3.36 x 10(-5)). Novel potential candidates (APCS, MPO) need to be replicated.

CONCLUSIONS

Our community-based data support the relevance of clinical and genetic factors for explaining variation in inflammatory biomarker traits.

IL6 and CRP haplotypes are associated with COPD risk and systemic inflammation: a case-control study

Background

Elevated circulating levels of C-reactive protein (CRP), interleukin (IL)-6 and fibrinogen (FG) have been repeatedly associated with many adverse outcomes in patients with chronic obstructive pulmonary disease (COPD). To date, it remains unclear whether and to what extent systemic inflammation is primary or secondary in the pathogenesis of COPD.

The aim of this study was to examine the association between haplotypes of CRP, IL6 and FGB genes, systemic inflammation, COPD risk and COPD-related phenotypes (respiratory impairment, exercise capacity and body composition).

Methods

Eighteen SNPs in three genes, representing optimal haplotype-tagging sets, were genotyped in 355 COPD patients and 195 healthy smokers. Plasma levels of CRP, IL-6 and FG were measured in the total study group. Differences in haplotype distributions were tested using the global and haplotype-specific statistics.

Results

Raised plasma levels of CRP, IL-6 and fibrinogen were demonstrated in COPD patients. However, COPD population was very heterogeneous: about 40% of patients had no evidence of systemic inflammation (CRP < 3 mg/uL or no inflammatory markers in their top quartile). Global test for haplotype effect indicated association of CRP gene and CRP plasma levels (P = 0.0004) and IL6 gene and COPD (P = 0.003). Subsequent analysis has shown that IL6 haplotype H2, associated with an increased COPD risk (p = 0.004, OR = 4.82; 1.64 to 4.18), was also associated with very low CRP levels (p = 0.0005). None of the genes were associated with COPD-related phenotypes.

Conclusion

Our findings suggest that common genetic variation in CRP and IL6 genes may contribute to heterogeneity of COPD population associated with systemic inflammation.

A QTL on 12q influencing an inflammation marker and obesity in white women: the NHLBI Family Heart Study

It has been recognized that obese individuals are intrinsically in a state of chronic inflammation, as indicated by positive correlations between serum levels of C-reactive protein (CRP) and various anthropometric measures of obesity. To explore the hypothesis that a gene(s) may underlie this relationship, we conducted bivariate linkage analyses of BMI and CRP in white and African-American (AA) families of the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study (FHS). Variance components linkage analysis as implemented in SOLAR was performed in 1,825 whites (840 men and 985 women) and 548 AAs (199 men and 351 women). CRP exhibited significant genetic correlations with BMI in women (0.54 +/- 0.10 for white and 0.53 +/- 0.14 for AA) and the combined samples (0.37 +/- 0.09 for white and 0.56 +/- 0.13 for AA), but not in men. We detected a maximum bivariate lod score of 3.86 on chromosome 12q24.2-24.3 at 139 cM and a suggestive linkage signal (lod = 2.19) on chromosome 19p13.1 (44 cM) in white women. Both bivariate peaks were substantially higher than their respective univariate lods at the same locus for each trait. No significant lod scores were detected in AAs. Our results indicate that chromosome 12q may harbor quantitative trait loci (QTLs) jointly regulating BMI and CRP in white women.

Genetic epidemiology in aging research

Over the last two decades, aging research has expanded to include not only age-related disease models, and conversely, longevity and disease-free models, but also focuses on biological mechanisms related to the aging process. By viewing aging on multiple research frontiers, we are rapidly expanding knowledge as a whole and mapping connections between biological processes and particular age-related diseases that emerge. This is perhaps most true in the field of genetics, where variation across individuals has improved our understanding of aging mechanisms, etiology of age-related disease, and prediction of therapeutic responses. A close partnership between gerontologists, epidemiologists, and geneticists is needed to take full advantage of emerging genome information and technology and bring about a new age for biological aging research. Here we review current genetic findings for aging across both disease-specific and aging process domains. We then highlight the limitations of most work to date in terms of study design, genomic information, and trait modeling and focus on emerging technology and future directions that can partner genetic epidemiology and aging research fields to best take advantage of the rapid discoveries in each.

Population-Based Genomewide Genetic Analysis of Common Clinical Chemistry Analytes

Background: Recent technologies enable genetic association studies of common clinical analytes on a genomewide basis in populations numbering thousands of individuals. The first publications using these technologies are already revealing novel biological functions for both genic and nongenic loci, and are promising to transform knowledge about the biological networks underlying disease pathophysiology. These early studies have also led to development of a set of principles for conducting a successful genomewide association study (GWAS).

Content: This review focuses on these principles with emphasis on the use of GWAS for plasma-based analytes to better understand human disease, with examples from cardiovascular biology.

Conclusions: The correlation of common genetic variation on a genomewide basis with clinical analytes, or any other outcome of interest, promises to reveal how parts of the genome work together in human physiology. Nonetheless, performing a genomewide association study demands an awareness of very specific epidemiologic and analytic principles.

Association of major depressive disorder with serum myeloperoxidase and other markers of inflammation: a twin study

BACKGROUND

Major depressive disorder (MDD) has been linked to inflammation, but this association may be due to common precursors to both depression and inflammation. Myeloperoxidase (MPO) is an inflammatory enzyme produced by activated leukocytes that predicts risk of coronary heart disease. We sought to examine whether MPO and other markers of inflammation are associated with MDD and whether the association is confounded by genetic or other shared familial factors.

METHODS

We examined 178 monozygotic and dizygotic middle-aged male twin pairs. We assessed MDD with the Structured Clinical Interview for DSM-IV. Blood markers of inflammation included MPO, interleukin-6, white blood cell count, C-reactive protein, tumor necrosis factor (TNF)-alpha, the TNF-alpha soluble receptor II, and fibrinogen. Analyses were conducted in the overall sample and among 67 twin pairs discordant for MDD using mixed effects regression.

RESULTS

Twins with a history of MDD had 32% higher levels of MPO (p < .0001); this difference persisted after adjusting for other risk factors. Among dizygotic MDD-discordant twin pairs, twins with MDD had 77% higher MPO than their brothers without MDD, after adjusting for other factors (p < .0001). In contrast, no significant association was found in monozygotic twins (p = .13). Similar, but weaker, associations were found between MDD and other inflammatory biomarkers.

CONCLUSIONS

Myeloperoxidase is a useful biomarker of immune activation in MDD. However, the association between inflammation and MDD is largely due to common genetic liability. Our results are consistent with the hypothesis that genes promoting inflammation are involved in the pathogenesis of MDD.

Association of parental hypertension with concentrations of select biomarkers in nonhypertensive offspring

Children of parents with hypertension are at increased risk of developing high blood pressure. We hypothesize that circulating concentrations of putative biomarkers (that may play a role in development of high blood pressure) are higher in nonhypertensive offspring of parents with hypertension. We compared concentrations of 4 different biomarkers (urinary albumin:creatinine ratio, circulating C-reactive protein, aldosterone:renin ratio, and plasminogen activator inhibitor-1) in nonhypertensive Framingham offspring study participants with none (n=233), 1 (n=474), or both (n=322) parents with hypertension. Parental hypertension was defined as onset before age 60 years, based on longitudinal observations of the original Framingham cohort. Serum C-reactive protein concentrations were higher in nonhypertensive offspring with 1 (median: 1.7; Q1 to Q3: 0.8 to 3.6 mg/L) or both parents with hypertension (median: 1.8; Q1 to Q3: 0.7 to 3.6 mg/L) compared with offspring without parental hypertension (median: 1.4; Q1 to Q3: 0.7 to 3.2 mg/L). In multivariable analyses, parental hypertension was associated with higher serum C-reactive protein concentration in offspring (15% increase per parent with hypertension; P=0.004). Prospectively, the relation of parental hypertension to longitudinal changes in blood pressure in the nonhypertensive offspring was attenuated on adjustment for C-reactive protein (P=0.04 for attenuation). The levels of the other biomarkers evaluated did not significantly differ in offspring according to parental hypertension status. In conclusion, serum C-reactive protein concentrations are higher in nonhypertensive offspring of parents with hypertension. These data suggest that inflammation may partly mediate the familial influences on hypertension risk.

C-reactive protein genotypes associated with circulating C-reactive protein but not with angiographic coronary artery disease: the LURIC study

AIMS

Circulating C-reactive protein is associated with future cardiovascular events. The causal role of C-reactive protein in the development of atherosclerosis remains controversial.

METHODS AND RESULTS

We analysed the association between three genetic polymorphisms (PM) (-717C>T, rs2794521; +1059G>C, rs1800947; +1444C>T, rs1130864) at the C-reactive protein locus and related haplotypes with both circulating C-reactive protein and angiographic coronary artery disease (CAD). The concentration of C-reactive protein was similar in patients with stable CAD and in controls, but increased in patients presenting with acute coronary syndromes. In models adjusting for the main confounding variables, the minor alleles of the +1059G>C (rs1800947) and the +1444C>T PM (rs1130864) were associated with decreased and increased concentrations of C-reactive protein, respectively. Haplotypes 1 and 4 decreased, and haplotype 2 increased C-reactive protein, whereas haplotype 3 had no appreciable effect. None of the genetic variants affecting circulating C-reactive protein was consistently associated with the prevalence of angiographic CAD.

CONCLUSION

A causal role of C-reactive protein in the development of CAD would require that genetic PM resulting in long-term modulation of the concentration of C-reactive protein be themselves associated with CAD. We were not able to detect such a relationship, which can be attributed to either a very small genetic effect size or the relationship between C-reactive protein and cardiovascular events may reflect confounding and reverse causation.

Polymorphisms of the HNF1A gene encoding hepatocyte nuclear factor-1 alpha are associated with C-reactive protein

Data from the Pharmacogenomics and Risk of Cardiovascular Disease (PARC) study and the Cardiovascular Health Study (CHS) provide independent and confirmatory evidence for association between common polymorphisms of the HNF1A gene encoding hepatocyte nuclear factor-1 alpha and plasma C-reactive protein (CRP) concentration. Analyses with the use of imputation-based methods to combine genotype data from both studies and to test untyped SNPs from the HapMap database identified several SNPs within a 5 kb region of HNF1A intron 1 with the strongest evidence of association with CRP phenotype.

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.