[Show abstract][Hide abstract] ABSTRACT: Genetic markers associated with disease are often non-functional and generally tag one or more functional "causative" variants in linkage disequilibrium. Markers may not show tight linkage to the causative variants across multiple ethnicities due to evolutionary divergence, and therefore may not be informative across different population groups. Validated markers of disease suggest causative variants exist in the gene and, if the causative variants can be identified, it is reasonable to hypothesize that such variants will be informative across diverse populations. The aim of this study was to test that hypothesis using functional Interleukin-1 (IL-1) gene variations across multiple ethnic populations to replace the non-functional markers originally associated with chronic adult periodontitis in Caucasians.
Adult chronic periodontitis cases and controls from four ethnic groups (Caucasians, African Americans, Hispanics and Asians) were recruited in the USA, Chile and China. Genotypes of IL1B gene single nucleotide polymorphisms (SNPs), including three functional SNPs (rs16944, rs1143623, rs4848306) in the promoter and one intronic SNP (rs1143633), were determined using a single base extension method or TaqMan 5' nuclease assay. Logistic regression and other statistical analyses were used to examine the association between moderate to severe periodontitis and IL1B gene variations, including SNPs, haplotypes and composite genotypes. Genotype patterns associated with disease in the discovery study were then evaluated in independent validation studies.
Significant associations were identified in the discovery study, consisting of Caucasians and African Americans, between moderate to severe adult chronic periodontitis and functional variations in the IL1B gene, including a pattern of four IL1B SNPs (OR = 1.87, p < 0.0001). The association between the disease and this IL1B composite genotype pattern was validated in two additional studies consisting of Hispanics (OR = 1.95, p = 0.04) or Asians (OR = 3.27, p = 0.01). A meta-analysis of the three populations supported the association between the IL-1 genotype pattern and moderate to severe periodontitis (OR 1.95; p < 0.001). Our analysis also demonstrated that IL1B gene variations had added value to conventional risk factors in predicting chronic periodontitis.
This study validated the influence of IL-1 genetic factors on the severity of chronic periodontitis in four different ethnicities.
Journal of Periodontal Research 04/2014; · 1.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective
To assess the influence of pro-inflammatory IL-1 genotype status on the risk of CAD, defined as >50% diameter stenosis, and cardiovascular events mediated by OxPL and Lp(a).
Oxidized phospholipids (OxPL) are pro-inflammatory, circulate on lipoprotein (a) [Lp(a)] and mediate coronary artery disease (CAD). Genetic variations in the interleukin-1 (IL-1) region are associated with increased inflammatory mediators.
IL-1 genotypes, OxPL on apolipoprotein B-100 (OxPL/apoB) and Lp(a) levels were measured in 499 patients undergoing coronary angiography. The composite genotype termed IL-1(+) was defined by three single nucleotide polymorphisms (SNPs) in the IL-1 gene cluster associated with higher levels of pro-inflammatory cytokines. All other IL-1 genotypes were termed IL-1(-).
Among IL-1(+) patients, the highest quartile of OxPL/apoB was significantly associated with a higher risk of CAD compared to the lowest quartile (OR 2.84, P=0.001). This effect was accentuated in patients ≤60 years old (OR 7.03, P<0.001). In IL-1(-) patients, OxPL/apoB levels showed no association with CAD. The interaction was significant for OxPL/apoB (OR 1.99, P=0.004) and Lp(a) (OR 1.96, P<0.001) in IL-1(+) versus IL-1(-) groups for patients ≤60 years old but not for patients >60 years old. In IL-1(+) patients ≤60 years old, after adjusting for established risk factors, high sensitivity C-reactive protein and Lp(a), OxPL/apoB remained an independent predictor of CAD. IL-1(+) patients above the median OxPL/apoB presented to the cardiac catheterization laboratory a mean of 3.9 years earlier (P=0.002) and had worse 4-year event-free survival (death, MI, stroke, and revascularization) compared to other groups (P=0.006).
Our study suggests that IL-1 genotype status can stratify population risk for CAD and cardiovascular events mediated by OxPL. These data suggest a clinically-relevant biological link between pro-inflammatory IL-1 genotypes, oxidation of phospholipids, Lp(a) and genetic predisposition to CAD and cardiovascular events.
Journal of the American College of Cardiology 01/2014; · 14.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objectives: Variations in genes for IL-1a and IL-1b (IL1B) have been associated with increased IL-1b levels and periodontitis severity or progression in >15 studies. Utility in non-Caucasians has been less well characterized partly due to different allele frequencies. Since elevated IL-1b is associated with periodontitis severity, we sought to identify IL1B single-nucleotide polymorphisms (SNPs) that are common in all major ethnicities and to determine if those variations were predictive of periodontitis in multiple ethnicities. Methods: Allelic and haplotypic frequencies for IL1 SNPs were compared across major ethnic groups: Caucasians (DARIC, N=767); African Americans (DARIC, N=156); Chinese 1 (N=300); Chinese 2 (N=1,000); and Indian (N=644). SNPs and haplotypes with high multi-ethnic frequency were identified. Single SNPs, haplotypes, and composite genotypes were then analyzed for association with periodontitis severity in Caucasians by logistic regression models adjusted for smoking. Patterns associated with disease in Caucasians were then evaluated in African-Americans. Results: SNPs with high frequency in all ethnic groups included the previously identified functional SNPs in the IL1B promoter (rs16944, rs1143623, rs4848306) and another IL1B SNP (rs1143633). Four IL1B promoter haplotypes (B1-B4) predominated with B3 and B4 having very different frequencies across ethnicities. Multiple composite genotypes in the IL1B gene were associated with severe periodontitis and elevated gingival fluid IL1b in Caucasians. When further tested in African Americans, the composite genotypes B1B1/(B1B4 and IL1B3877=1.1)/B2B3/B2B4/B3B3/B3B4/B4B4 were also significantly associated with severe periodontitis (p=0.003 and 0.043 for Caucasians and African Americans, respectively). Conclusion: These studies have identified IL1 SNPs and haplotypes that are highly prevalent in all major ethnic populations. Specific composite genotypes were significantly associated with more severe periodontitis in Caucasians and African-Americans. Studies in Chinese are in progress. These findings suggest a pattern of IL1B gene variations may be valuable predictors of periodontitis severity independent of ethnicity.
[Show abstract][Hide abstract] ABSTRACT: The objective was to investigate whether genotypes, haplotypes and haplotype-pairs of interleukin (IL) gene cluster are associated with risk of Myocardial Infarction (MI) at young age and with the release of IL-1B and expression of tissue factor pro-coagulant activity (TFPCA), after stimulation in vitro with lipopolysaccharide (LPS) of human peripheral blood mononuclear cells (PBMCs). Patients with MI at young age, frequency-matched for age, sex and recruitment centre, with healthy population-based controls and PBMCs from healthy volunteers were studied. Five single nucleotide polymorphisms (SNPs), identifying two haplotype-blocks, in IL-1B gene and one SNP in IL-1A and IL-RA genes were genotyped. In multivariate analyses, haplotype A2 (122) and A4 (112) were associated with decreased risk of MI [OR = 0.62 (95% CI = 0.40-0.95), p = 0.01; OR = 0.69 (95% CI = 0.51-0.92), p = 0.03, respectively]. Haplotype-pair A2/A2 showed significant reduction in the risk of MI [OR = 0.38 (95% CI = 0.18-0.81); p = 0.01]. Haplotype A2 and A4 were associated with lower levels of IL-1B (respectively p = 0.01; p = 0.04, multivariate analysis) and haplotype-pair A2/A4 showed decreased levels of IL-1beta (p = 0.02). No association was found between block "B" IL-1B haplotypes or IL-1A and IL-RA polymorphisms and risk of MI. IL-1B haplotypes influence the inflammatory response of human mononuclear cells to LPS and affect the risk of MI at young age.
[Show abstract][Hide abstract] ABSTRACT: Interleukin-1beta (IL-1beta) activates inflammatory mediator cascades and has been implicated in the pathogenesis of several diseases. Single nucleotide polymorphisms (SNPs) of the IL1B promoter have been associated with various inflammatory diseases. We recently reported that IL1B gene transcription was influenced by four promoter SNPs, and that individual SNP function in vitro was governed by haplotype context. In the present study we tested the in vivo relevance of this observation by comparing IL1B promoter haplotype-pairs with IL-1beta protein levels in 900 gingival tissue fluid samples. Three SNPs (-511, -1464, -3737) defined four IL1B promoter haplotypes that occurred in the study population and could be assigned unambiguously to each chromosome. The four haplotypes defined ten haplotype-pairs of which four pairs, representing 57% of the population, were associated with 28-52% higher IL-1beta protein levels in vivo. Two of these pairs, characterized by homozygosity for the common allele at -3737, were also associated with raised serum levels of C-reactive protein (p = 0.02). We validated these findings in stimulated peripheral blood mononuclear cells (PBMCs) from a separate population (N = 70). PBMCs with IL1B haplotype-pairs associated with higher in vivo levels of IL-1beta produced 86-287% more IL-1beta in vitro than the reference group. We believe that this is the first demonstration of a relationship between in vivo levels of an inflammatory mediator and gene promoter haplotypes on both chromosomes. These findings may apply to other inducible genes and could provide a logical framework for exploring disease risk related to genetic variability in pathogenic mediators.
Human Genetics 06/2008; 123(4):387-98. · 4.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although observational studies have shown that genotype may influence nutritional effects on target outcomes, there are few reported studies that stratified subjects by genotype before a nutritional intervention. This proof-of-concept trial determined whether specifically formulated botanical mixtures reduced inflammation in individuals with genetic variations that predispose to overexpression of interleukin-1beta (IL-1beta) and early heart disease.
Healthy adults with elevated C-reactive protein (CRP) were stratified into genetic groups based on being positive (IL1(Pos)) or negative (IL1(Neg)) for the at-risk IL-1 gene variations. IL1(Pos) (n = 39) and IL1(Neg) (n = 40) subjects were then randomized to the candidate botanical formulation or placebo. The botanical formulation included rose hips, a blueberry and blackberry mixture, and a grapevine extract.
At 12 wk of dosing with the botanical formulation, IL-1beta gene expression by stimulated peripheral blood mononuclear cells was significantly lower than at baseline and significantly lower than placebo in IL1(Pos) and IL1(Neg) subjects. Mean IL-1beta gene expression treatment effect over the 12-wk period was greater in IL1(Pos) than in IL1(Neg) subjects. At 12 wk of dosing the botanical mixture produced no mean change in serum CRP levels. However, in IL1(Pos) subjects, significantly more subjects achieved a reduction in CRP with the botanical mixture than with placebo. No CRP effect was observed in the IL1(Neg) subjects.
This study represents one of a few prospective clinical trials in which genetic variations were shown to differentially influence nutrient effects on outcomes.
[Show abstract][Hide abstract] ABSTRACT: We questioned the significance of haplotype structure in gene regulation by testing whether individual single nucleotide polymorphisms (SNPs) within a gene promoter region [interleukin-1-beta (IL1B)] might affect promoter function and, if so, whether function was dependent on haplotype context. We sequenced genomic DNA from 25 individuals of diverse ethnicity, focusing on exons and upstream flanking regions of genes of the cluster. We identified four IL1B promoter region SNPs that were active in transient transfection reporter gene assays. To substantiate allelic differences found in reporter gene assays, we also examined nuclear protein binding to promoter sequence oligonucleotides containing different alleles of the SNPs. The effect of individual SNPs on reporter gene transcription varied according to which alleles of the three other SNPs were present in the promoter construct. The SNP patterns that influenced function reflected common haplotypes that occur in the population, suggesting functionally significant interactions between SNPs according to haplotype context. Of the haplotypes that include the four functional IL1B promoter SNPs (-3737, -1464, -511, -31), the four haplotypes that showed different contextual effects on SNP function accounted for >98% of the estimated haplotypes in Caucasian and African-American populations. This finding underlines the importance of understanding the haplotype structure of populations used for genetic studies and may be especially important in the functional analysis of genetic variation across gene regulatory regions.
Human Molecular Genetics 02/2006; 15(4):519-29. · 7.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In humans and in animal models, susceptibility to arthritis is under complex genetic control, reflecting influences on the immunological processes that initiate autoimmunity and on subsequent inflammatory mechanisms in the joints. The effector phases are conveniently modeled by the K/BxN serum transfer system, a robust model well suited for genetic analysis where arthritis is initiated by pathogenic Ig. Here, we mapped the genetic loci distinguishing the high-responder BALB/c vs. low-responder SJL strains. After computational modeling of potential breeding schemes, we adapted a stepwise selective breeding strategy, with a whole-genome scan performed on a limited number of animals. Several genomic regions proved significantly associated with high sensitivity to arthritis. One of these regions, on distal chr2, was centered on the interleukin 1 gene family. Quantitation of transcripts of the Il1a and Il1b candidate genes revealed a 10-fold greater induction of Il1b mRNA in BALB/c than in SJL splenocytes after injection of LPS, whereas Il1a showed much less difference. The differential activity of the Il1b gene was associated with a particular sequence haplotype of noncoding polymorphisms. The BALB/c haplotype was found in 75% of wild-derived strains but was rare among conventional inbred strains (4/33 tested, one of which is DBA/1, the prototype arthritis-susceptible strain) and was associated with vigorous Il1b responses in a panel of inbred strains. Inbred strains carrying this allele were far more responsive to serum-transferred arthritis, confirming its broad importance in controlling arthritis severity.
Proceedings of the National Academy of Sciences 09/2005; 102(35):12489-94. · 9.81 Impact Factor