No evidence for involvement of the toll-like receptor (TLR) 4 gene Asp299Gly and Thr399Ile polymorphisms in susceptibility to primary gouty arthritis

Previous studies demonstrated that toll-like receptor (TLR) 4 was involved in the development of autoinflammatory disease including gouty arthritis (GA). TLR4 functional gene Asp299Gly and Thr399Ile polymorphisms play a role in some autoinflammatory disease susceptibility. We undertook this study to analyze the association between the genetic polymorphisms within TLR4 gene and the susceptibility to GA in Chinese Han people. Two functional variants, Asp299Gly and Thr399Ile, in the TLR4 gene were genotyped using 5′ exonuclease TaqMan^® technology from 218 male GA patients and 226 ethnically matched controls. None polymorphisms of Asp299Gly and Thr399Ile were detected in all GA cases and controls, which indicates that there is no evidence for involvement of the TLR4 gene Asp299Gly and Thr399Ile polymorphisms in susceptibility to primary GA in the Chinese Han population. Further studies with extended single nucleotide polymorphisms should be performed.     

Lack of association of TLR4 gene Asp299Gly and Thr399Ile polymorphisms with rheumatoid arthritis in Chinese Han population of Yunnan Province

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of synovium and subsequent joint destruction. Recently, genetic polymorphisms within the toll-like receptor 4 (TLR4) genes have been reported to be associated with RA. To analyze the association between the genetic polymorphisms within TLR4 gene and the susceptibility to RA in Chinese people, two functional variants, Asp299Gly and Thr399Ile, in the TLR4 gene were genotyped using polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) and direct sequencing techniques from 213 RA patients and 247 ethnically matched controls. None polymorphisms of Asp299Gly and Thr399Ile were detected in all RA cases and controls, which indicates that there is no relevance between these two SNPs and RA in the Chinese Han population. Further studies with extended single nucleotide polymorphisms (SNP) should be performed.     

Variant Toll-like receptor4 (Asp299Gly and Thr399Ile alleles) and Toll-like receptor2 (Arg753Gln and Arg677Trp alleles) in colorectal cancer

The innate immune system recognizes the presence of bacterial products through the expression of a family of membrane receptors known as Toll-like receptors (TLRs). Polymorphisms in TLRs have been shown to be associated with increased susceptibility to diseases such as inflammatory bowel disease. The aim of this study was to determine whether there was a correlation between polymorphisms of TLR4 (Asp299Gly; Thr399Ile) and TLR2 (Arg677Trp; Arg753Gln) genes and risk of colorectal cancer. DNA from 60 colorectal carcinoma patients from 3 major races in Malaysia (22 Malays, 20 Chinese and 18 Indians) and blood from 50 apparently healthy individuals were evaluated. Control group were matched to study group by race and age. The polymorphisms were determined by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). Genotyping results showed two out of sixty tumour specimens (3.3%) harbored both variant TLR4 Asp299Gly and Thr399Ile alleles. In contrast, DNA isolated from blood cells of 50 apparently healthy individuals harbored wild type TLR4. In the case of TLR2 Arg753Gln genotyping, all of the fifty normal and 60 tumours were of the wild type genotype. TLR2 Arg677Trp genotyping showed a heterozygous pattern in all samples. However, this may not be a true polymorphism of the TLR2 gene as it is likely due to a variation of a duplicated ( pseudogene) region. There was only a low incidence (2/60; 3.3%) of TLR4 polymorphism at the Asp299Gly and Thr399Ile alleles in colorectal cancer patients. All normal and tumour samples harbored the wild type TLR2 Arg753 allele. Our study suggests that variant TLR4 (Asp299Gly and Thr399Ile alleles) as well as TLR2 (Arg753Gln allele) are not associated with risk of colorectal cancer.     

Toll-like receptor 4 gene polymorphisms and preeclampsia: lack of association in a Caucasian population

Preeclampsia is a multifactorial disorder with genetic and environmental components. As Toll-like receptor 4 (TLR4) has an essential role in innate immune response, which is exaggeratedly activated in preeclampsia, our aim was to investigate whether two single nucleotide polymorphisms (SNPs) of the TLR4 gene--Asp299Gly (A896G) and Thr399Ile (C1196T)--are associated with preeclampsia in a Caucasian population from Hungary. In a case-control study, we analyzed blood samples from 180 preeclamptic patients and 172 normotensive, healthy pregnant women with the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method. The linkage disequilibrium (LD) profile of the TLR4 gene was investigated and tag SNPs were identified using data from the International HapMap Project. There were no significant differences in the genotype and allele frequencies of Asp299Gly and Thr399Ile polymorphisms between the two study groups. Additionally, no significant difference was found in the distribution of the estimated haplotypes created by the two polymorphisms between the preeclamptic and the control group. Furthermore, no significant differences were detected in the genotype, allele and haplotype frequencies of Asp299Gly and Thr399Ile TLR4 SNPs between patients with mild and severe preeclampsia, between patients with late and early onset of the disease, or between preeclamptic patients with and without fetal growth restriction. In conclusion, we did not find an association between TLR4 Asp299Gly and Thr399Ile gene polymorphisms and preeclampsia. As the Thr399Ile polymorphism is a highly informative tag SNP of the TLR4 gene, our results suggest that variations in this genomic region are not associated with preeclampsia. Nevertheless, further studies are required with determination of fetal TLR4 genotypes to explore the role of TLR4 gene polymorphisms in the risk of preeclampsia, especially in ethnically different populations.     

Genetic association of TLR4 Asp299Gly,TLR4 Thr399Ile,and CD14 C‐159T polymorphisms with the risk of severe RSV infection: a meta‐analysis

Respiratory syncytial virus (RSV) is the most frequent cause of hospitalization in infants worldwide. It is recognized by Toll‐like receptor 4 (TLR 4) and cluster of differentiation 14 (CD14) in the innate immune response. Previous case–control studies reported the influence of TLR4 Asp299Gly, TLR4 Thr399Ile, and CD14 C‐159T polymorphisms on the risk of severe RSV infection. However, a decisive conclusion has not been achieved. Therefore, we performed this meta‐analysis to examine the association between these three polymorphisms and the development of RSV bronchiolitis. A systematic literature search was performed using the PubMed, EMbase, Google Scholar Search, China National Knowledge Infrastructure, China Biological Medicine, and Wanfang Databases. The data were extracted and pooled odds ratios with 95% confidence intervals were calculated under six genetic models. A total of six studies with 1009 cases and 1348 controls, three studies with 473 cases and 481 controls, or four studies with 325 cases and 650 controls relating to each of the three polymorphisms were included in this meta‐analysis. The analyzed data indicated that all of these polymorphisms were not associated with the risk of severe RSV infection. This is the first meta‐analysis to investigate the relationship of TLR4 Asp299Gly, TLR4 Thr399Ile, and CD14 C‐159T polymorphisms with the risk of severe RSV infection. Although the results of this retrospective analysis indicated a lack of the association, more extensive multicentric studies with large sample sizes are necessary to provide a more reliable estimation of the association between these three polymorphisms and RSV bronchiolitis susceptibility.     

The role of Toll-like receptor 4 Asp299Gly and Thr399Ile polymorphisms and CARD15/NOD2 mutations in the susceptibility and phenotype of Crohn's disease

BACKGROUND: We investigated the influence of 2 common Toll-like receptor 4 (TLR4) polymorphisms on susceptibility and disease characteristics of Crohn's disease (CD). METHODS: Genomic DNA from 204 patients with CD and 199 unrelated controls was analyzed for the presence of 2 single nucleotide polymorphisms in the TLR4 gene, resulting in the amino acid substitutions Asp299Gly and Thr399Ile. In addition, the carrier status for the 3 common CD-associated CARD15/NOD2 gene mutations, Arg702Trp, Gly908Arg, and 1007fs, was determined. The frequency of the different genotypes was compared, and a detailed genotype-phenotype correlation was performed. RESULTS: An almost 2-fold increase in the frequency of the TLR4 Asp299Gly phenotype was observed in patients with CD (14.2%) compared with healthy controls (7.5%, P = 0.038, odds ratio = 2.03). The prevalence of a stricturing phenotype was increased in patients heterozygous for 1 of the TLR4 polymorphisms studied (Asp299Gly, 34.5%; Thr399Ile, 36.7%) compared with patients with wild-type TLR4 (17.1% and 16.7%; P = 0.04 and 0.02, respectively). The presence of the Asp299Gly polymorphism in the absence of CARD15/NOD2 mutations was a particularly strong predictor of the stricturing disease phenotype that was present in 47.4% of the patients with Asp299Gly+/NOD2- compared with 10.1% of the patients with the Asp299Gly-/NOD2+ status (P = 0.0009; P = 0.0004 for Thr399Ile+/NOD2- versus Thr399Ile-/NOD2+). In contrast, there was a trend toward a higher prevalence of the penetrating phenotype in the TLR4-/NOD2+ group (71.6%) compared with the TLR4+/NOD2- group (47.4%, P = 0.059). CONCLUSIONS: The TLR4 Asp299Gly polymorphism is a risk factor for CD. TLR4 and CARD15/NOD2 mutations may contribute to distinct disease phenotypes.     

Lack of association of single nucleotide polymorphisms in toll-like receptors 2 and 4 with enthesitis-related arthritis category of juvenile idiopathic arthritis in Indian population

Toll-like receptors 2 and 4 are over expressed in patients with enthesitis-related arthritis and cause increased production of pro-inflammatory cytokines. This aberrant functioning could be due to polymorphisms in TLR2 and TLR4. Hence, we genotyped ERA patients for Arg753Gln and Arg677Trp polymorphism in TLR2 gene and Asp299Gly and Thr399Ile polymorphism in TLR4 gene. DNA was extracted from blood from ERA patients and healthy controls. All four polymorphisms were studied by PCR–RFLP method. 200 healthy controls and 97 ERA patients were enrolled. All healthy controls and patients had wild-type allele for Arg753Gln and Arg677Trp TLR2 polymorphism. Regarding TLR4, Asp299Gly polymorphism A allele frequency was 90 % in controls and 96 % in patients (OR 2.7, 95 % CI 0.81–8.8). GG homozygous genotype was detected in one healthy control and was absent from patients. The TLR4 Thr399Ileu variant was not detected in patients. Out of 200 healthy controls, 10 were heterozygous (5 %) and only one was homozygous for rare variant (0.5 %). Polymorphisms in TLR2 and TLR4 are not associated with ERA.     

Association between Toll-like receptor 4 and inflammatory bowel disease

BACKGROUND: The human Toll-like receptor 4 (TLR4) participates in the innate response. Recently, the TLR4 variant Asp299Gly has been described to affect the response of this receptor to lipopolysaccharide. As such, there is a potentially important role of TLR4 in the pathogenesis of inflammatory bowel disease (IBD). We studied the involvement of TLR4 in IBD in a large population of Dutch patients with IBD and in family-based controls. METHODS: In 781 IBD cases and 315 controls, genotyping was performed forAsp299Gly and Thr399Ile variants and for 4 microsatellite markers flanking TLR4. Association analysis and the were applied. In addition, interaction of TLR4 with the caspase recruitment domain containing protein 15 gene (CARD15) was studied in patients with Crohn's disease (CD). RESULTS: The haplotype sharing statistic showed association at microsatellite marker D9S1864 with IBD (P = 0.0019), and in particular with CD (P = 0.0025) and at TLR406 with ulcerative colitis (UC; P = 0.027). No association was found for Asp299Gly and Thr399Ile. However, the frequencies of both variant allele carriers were higher among CD cases with a disease onset > or = 40 years than among controls. No evidence for interaction between TLR4 and CARD15 was found. CONCLUSIONS: Haplotype analysis shows that TLR4 is associated with both CD and UC. The Asp299Gly and Thr399Ile variants do not show an association with CD, UC, or IBD as a group, indicating that these polymorphisms are likely not the causal ones. We propose that the 2 polymorphisms are in linkage with (the) disease susceptibility variant(s) located elsewhere on TLR4.     

Toll-like receptor 4 gene polymorphisms and susceptibility to juvenile idiopathic arthritis

OBJECTIVES: To determine if polymorphisms within the Toll-like receptor 4 (TLR4) gene are associated and linked with juvenile idiopathic arthritis (JIA). To investigate any possible gene-gene (epistatic) interaction between TLR4 and macrophage migration inhibitory factor (MIF) gene polymorphisms. METHODS: 313 simplex families (each containing one affected JIA proband) were genotyped. Two known functionally important single nucleotide polymorphisms (SNPs) within the TLR4 gene (Asp299Gly and Thr399Ile) were typed by SNaPshot ddNTP primer extension and capillary electrophoresis.Single point and multipoint transmission disequilibrium tests (TDT) were carried out through the extended TDT and TDT phase packages for the two TLR4 SNPs. Epistatic interaction between TLR4 haplotypes and the previously JIA associated MIF CATT(7)-MIF-173*C promoter haplotype was investigated by chi(2) test and unconditional logistic regression in Stata version 7. RESULTS: No distortion from random inheritance was observed by single point analysis for TLR4 Asp299Gly (p = 0.89) or TLR4 Thr399Ile (p = 0.40). Similarly, no distortion in transmission was seen when the TLR4 haplotypes were studied (p = 0.54). Additionally, no evidence for gene-gene interaction between TLR4 polymorphisms and the previously associated MIF gene polymorphisms was found (p = 0.40). CONCLUSIONS: No linkage or association was seen for Asp299Gly or Thr399Ile SNPs of TLR4 with JIA susceptibility. No evidence of an epistatic interaction between these TLR4 polymorphisms and MIF polymorphisms was found.     

Functional polymorphisms of CD14 and toll-like receptor 4 in Taiwanese Chinese with Helicobacter pylori-related gastric malignancies

BACKGROUND/AIMS: Interindividual differences in degrees and extent of gastritis are responsible for the divergent outcomes after H. pylori infection. Cellular responses in gastric inflammation are mediated by lipopolysaccharide of H. pylori, which activate monocytes to express cytokine expression and growth factors via CD14 and toll-like receptor 4 (TLR4). Whether functional polymorphisms of TLR 4 and CD14 account for H. pylori-related gastric malignancies remains unknown. This study aimed to investigate the contribution of CD14 and TLR4 genotypes to the risk of H. pylori-related gastric malignancies in a Chinese population. METHODOLOGY: Genotyping for CD14 (-159C/T) and TLR4 (Asp 299Gly and Thr 399Ile) was performed in 70 patients with gastric mucosa-associated lymphoid tissue lymphoma (MALToma), 204 patients with non-cardia gastric adenocarcinoma (GAC), and 210 unrelated healthy controls. Distribution of genotype and allele frequencies among three groups was compared. RESULTS: The seropositive rate of H. pylori was significantly higher for non-cardia GAC (164/204, 80.4%) and MALToma (66/70, 94.3%) than controls (120/210, 57.5%, p<0.001). A complete absence of Gly or Ile variants was noted for all the studied subjects. The genotype frequencies of CD14 in controls were C/C, 25.7%, C/T, 48.6%, and T/T, 25.7%, and did not deviate from the Hardy-Weinberg equilibrium. The distribution of CD14 genotype did not differ significantly among GAC, MALToma patients, and controls. CONCLUSIONS: These data suggest no apparent association of CD14 polymorphisms with H. pylori-related gastric malignancy and provide evidence for race-specific distribution of TLR4 alleles in Chinese population.     

Association of toll-like receptor 4 variants and ankylosing spondylitis: a case-control study

OBJECTIVE: Functional single nucleotide polymorphisms within the ectoplasmic domain of the Toll-like receptor 4 (TLR4) gene have been shown to result in an endotoxin-hyporesponsive phenotype and aberrant signal transduction for bacterial agonists. TLR4 is in proximity to a genome-wide linkage peak in 9q32-33. Given the proposed function and location of TLR4, we examined the association of 2 functional variants of TLR4 in patients with ankylosing spondylitis (AS) in Newfoundland. METHODS: In total, 101 AS patients and 100 ethnically matched controls were genotyped, using the Sequenom MassArray platform, for 2 functional variants in the TLR4 gene: Asp299Gly (A/G polymorphism) and Thr399Ile (C/T polymorphism). RESULTS: The minor allele frequency for the Asp299Gly variant (G) was significantly higher in AS cases compared to controls (7.5% vs 2.6%, respectively; OR 3.10, p = 0.037). The minor allele frequency for the Thr399Ile variant (T) for cases and controls was 7.4% vs 3.0% (OR 2.59, p = 0.071). Haplotype analysis using Haploview noted a higher proportion of GT in the cases (for GT, chi-squared p = 0.023). CONCLUSION: Given the functional role of TLR4 variants in the innate immune system, larger studies are now warranted to elucidate the association of TLR4 variants in AS.     

CD14 -550 C/T, which is related to the serum level of soluble CD14, is associated with the development of respiratory syncytial virus bronchiolitis in the Japanese population

BACKGROUND: The contribution that genetic polymorphisms of Toll-like receptor (TLR) 4 and of CD14--both of which recognize respiratory syncytial virus (RSV) in the innate immune response--make to RSV bronchiolitis in the Japanese population has not yet been clarified. METHODS: This study genotyped 2 TLR4 mutations, Asp299Gly and Thr399Ile, and 2 single-nucleotide polymorphisms (SNPs) of CD14, -550 C/T and -159 C/T, in 54 children with RSV bronchiolitis and in 203 control subjects. CD14 SNPs and the serum level of soluble CD14 (sCD14) also were examined in 67 cord-blood specimens and in serum samples from 73 6-year-old children. RESULTS: No TLR4 mutations were found. The frequencies of both the CC genotype and the C allele of CD14 -550 C/T were significantly higher in children with RSV bronchiolitis than in the control subjects. The serum level of sCD14 was significantly higher in children with the CC genotype of CD14 -550 C/T than in those with the CT and TT genotypes. CONCLUSIONS: CD14 -550 C/T, which is related to the serum level of sCD14, is associated with the development of RSV bronchiolitis in the Japanese population. This study's results indicate that, in different ethnic groups, different genetic factors contribute to the development of RSV bronchiolitis.     

Has toll-like receptor 4 been prematurely dismissed as an inflammatory bowel disease gene? Association study combined with meta-analysis shows strong evidence for association

OBJECTIVES: Published association studies of the TLR4 Asp299Gly polymorphism and inflammatory bowel disease (IBD) in caucasian populations have inconsistent results. We tested two TLR4 variants for association with IBD in the New Zealand caucasian population and assessed the cumulative evidence for association of TLR4 Asp299Gly and IBD. METHODS: The TLR4 Asp299Gly and Thr399Ile polymorphisms were genotyped and tested for case-control frequency differences in a New Zealand white cohort of 389 Crohn's disease (CD) patients, 405 ulcerative colitis (UC) patients, and 416 population controls. Meta-analysis using a random effects model was performed to test whether 299Gly carriage was associated with UC, CD, or phenotypes of CD patients. RESULTS: There were no significant allele or genotype frequency differences between cases and controls or between CD phenotypes in our New Zealand data. Meta-analysis did not identify any significant associations between CD phenotypes and 299Gly carriage. However, meta-analysis demonstrated significantly higher 299Gly carrier frequencies in CD patients (odds ratio 1.45, 95% CI 1.11-1.90) and in IBD patients (odds ratio 1.36, 95% CI 1.01-1.84) compared to controls. CONCLUSIONS: The meta-analysis provides evidence that Asp299Gly is associated with CD and IBD in whites. Only the Asp299Gly polymorphism has been consistently genotyped in previous TLR4 studies with IBD patients, therefore other TLR4 variants with stronger associations with IBD may exist. Additional well-powered studies of Asp299Gly and other TLR4 variants are urgently needed.     

TLR4 Asp299Gly and Thr399Ile polymorphisms are very rare in the Chinese population

Endotoxin is an important component of bio-aerosols that contribute to airway inflammation and airflow obstruction. Toll-like receptor 4 (TLR4) mediates the host response to bacterial lipopolysaccharide (LPS), and the Asp299Gly and Thr399Ile polymorphisms have been associated with the development of respiratory diseases. We hypothesized that TLR4 polymorphisms may be associated with a decline of lung function in cotton workers who were exposed continuously to endotoxin. We investigated these two polymorphisms in our 20-year longitudinal cohort of Han Chinese cotton and silk textile workers. The two polymorphisms were genotyped using TaqMan and PCR-restriction fragment length polymorphism methods. No homozygous or heterozygous variant genotypes of the Asp299Gly and Thr339Ile polymorphisms were detected in 491 samples of this population. Our results suggest that the TLR4 Asp299Gly and Thr339Ile polymorphisms are very rare in the Chinese population.     

Association of hypo-responsive toll-like receptor 4 variants with risk of myocardial infarction.

AIM: Toll-like receptor 4 (TLR4) is a receptor for bacterial lipopolysaccharide (LPS) and heat shock protein essential for innate immunity. Recent studies imply that TLR4 polymorphisms might affect atherogenesis. In this study we investigated the impact of LPS-hypo-responsive TLR4 variants on the risk of myocardial infarction (MI). METHODS AND RESULTS: Using TaqMan PCR technology, we determined the prevalence of the Asp299Gly and Thr399Ile polymorphisms in the TLR4 gene, and their association with MI in a study of 1213 survivors of a first MI and 1561 controls from the Stockholm region. The frequency was 0.096 for carriers of both 299Gly and 399Ile, and 0.006 for carriers of 399Ile alone. Carriers of both 299Gly and 399Ile were more frequent among the male cases than the male controls (10.7% vs 7.9%, p = 0.004). Compared with wild-type carriers, men with the 299Gly and the 399Ile TLR4 genotype had an increased risk of MI (OR [95% CI]: 1.4 [1.0;1.9]) whereas no association was observed for women. Furthermore a synergistic interaction was found between the TLR4 polymorphism and smoking in men. CONCLUSION: The association found between TLR4 genotype and risk of MI suggests that TLR4 genetic variants could potentially affect the susceptibility to MI and that TLR4-mediated innate immunity is implicated in the pathogenesis of MI.     

TLR4 mutations (Asp299Gly and Thr399Ile) are not associated with ankylosing spondylitis

BACKGROUND: Immunoregulatory genes and Gram negative gut bacteria are thought to be important in disease expression in ankylosing spondylitis (AS). OBJECTIVE: To compare the frequency of two common and functional TLR4 mutations (Asp299Gly, and Thr399Ile) between patients with AS and HLA-B27 healthy controls. METHODS: The TLR4 genotypes of patients and healthy HLA-B27 controls were determined using allele-specific PCR and restriction fragment length polymorphism analysis. Asp299Gly genotype was determined in 193 patients and 125 HLA-B27 positive controls and Thr399Ile genotype in 184 patients and 113 HLA-B27 controls. Allele frequencies were compared using a chi(2) test of association. RESULTS: 29/193 (15%) patients with AS had a polymorphism in the Asp299 site compared with 18/125 (14.4%) healthy HLA-B27 controls. Of the patients genotyped for the Thr399Ile allele, 29/184 (15.8%) carried the polymorphism compared with 19/113 (16.8%) HLA-B27 controls. No significant difference between the frequencies of the Asp299Gly genotype or the Thr399Ile genotype between patients with AS and healthy HLA-B27 controls was found. No significant difference in allele frequency was found at either site. CONCLUSION: Two common TLR4 polymorphisms, which cause a functional deficiency in host immune response to Gram negative bacteria, are not overrepresented in patients with AS.     

TLR-2 Arg753Gln, TLR-4 Asp299Gly, and TLR-4 Thr399Ile polymorphisms in Henoch Schonlein purpura with and without renal involvement

Infections may trigger or aggravate glomerulonephritidis and renal vasculitis like Henoch Schonlein purpura (HSP). HSP is seen more frequently in patients with familial Mediterranean fever in which TLR-2 Arg753Gln polymorphism frequency is increased. Although renal involvement is the most important factor affecting the prognosis in HSP, it is not known which patients will have renal disease or why some patients have severe renal involvement while some others have mild renal disease. We investigated the role of TLR-2 and TLR-4 polymorphisms on the incidence and severity of renal involvement in HSP patients. We studied HSP patients with and without nephritis (n = 15 for each group) and healthy controls (n = 100). TLR-2 Arg753Gln and TLR-4 Asp299Gly/Thr399Ile polymorphisms were analyzed with polymerase chain reaction–restriction fragment length polymorphism method. The frequency of TLR-2 Arg753Gln, TLR-4 Asp299Gly, and Thr399Ile polymorphisms in healthy controls were 1, 3, and 2%, respectively. The frequencies of these polymorphisms were not different in HSP patients with or without nephritis compared to healthy controls. TLR-3 Arg753Gln, TLR-4 Asp299Gly, and Thr399Ile polymorphisms are not increased in HSP or HSP nephritis patients.     

Toll-like receptor 4 and inducible nitric oxide synthase gene polymorphisms are associated with Type 2 diabetes

BackgroundThe toll-like receptor 4 (TLR4) and inducible nitric oxide synthase are proteins from the innate immune system that, when activated, can induce insulin resistance. Polymorphisms in these genes, TLR4 and NOS2, respectively, could affect the immune response, as well as the prevalence of Type 2 diabetes (T2DM).ObjectiveThe aim of the present study was to investigate the contribution of four polymorphisms (two from TLR4 and two from NOS2) to susceptibility to T2DM in a southeast Brazilian population.DesignA total of 211 patients with T2DM and 200 unrelated controls were genotyped for the Asp299Gly and Thr399Ile polymorphisms of the TLR4 gene and for the insertion (I)/deletion (D) AAAT and (CCTTT)n polymorphisms of the NOS2 promoter gene.ResultsWith regard to the NOS2 promoter region, the data showed that the I allele of the I/D AAAT polymorphism was more prevalent in the T2DM group and that the L/L genotype of the (CCTTT)n polymorphism was also more frequent in the same group. In contrast, the 299Gly allele and the 399Ile allele from the Asp299Gly and Thr399Ile TLR4 gene polymorphisms, respectively, were associated with protection of T2DM. It is believed that the persistence of these genetic variations in human populations may be indicative of a selective advantage in the face of different environmental pressures.ConclusionsGenetic variations in the NOS2 gene promoter and TLR4 coding sequence may lead to deleterious and protective effects, respectively, arising from altered function of the innate immune system in patients with T2DM.     

TLR4 polymorphisms, infectious diseases, and evolutionary pressure during migration of modern humans

Infectious diseases exert a constant evolutionary pressure on the genetic makeup of our innate immune system. Polymorphisms in Toll-like receptor 4 (TLR4) have been related to susceptibility to Gram-negative infections and septic shock. Here we show that two polymorphisms of TLR4, Asp299Gly and Thr399Ile, have unique distributions in populations from Africa, Asia, and Europe. Genetic and functional studies are compatible with a model in which the nonsynonymous polymorphism Asp299Gly has evolved as a protective allele against malaria, explaining its high prevalence in subSaharan Africa. However, the same allele could have been disadvantageous after migration of modern humans into Eurasia, putatively because of increased susceptibility to severe bacterial infections. In contrast, the Asp299Gly allele, when present in cosegregation with Thr399Ile to form the Asp299Gly/Thr399Ile haplotype, shows selective neutrality. Polymorphisms in TLR4 exemplify how the interaction between our innate immune system and the infectious pressures in particular environments may have shaped the genetic variations and function of our immune system during the out-of-Africa migration of modern humans.