The -174GG interleukin-6 genotype is protective from retinopathy and nephropathy in juvenile onset type 1 diabetes mellitus

IL-6 gene rs1800795 polymorphism and diabetes mellitus: a comprehensive analysis involving 42,150 participants from a meta-analysis

BACKGROUND

Over the past two decades, several studies have focused on the association between a common polymorphism (rs1800795) from interleukin-6 (IL-6) gene and Diabetes Mellitus (DM) risk. However, the results remain ambiguous and indefinite.

METHODS

A comprehensive analysis was performed to explore this relationship. A search was conducted in the PubMed, Embase, Chinese (CNKI and Wanfang), and GWAS Catalog databases, covering all publications until February 10, 2022. Odds ratios (OR) with 95% confidence intervals (CI) were used to evaluate the strength of the association. Publication bias was assessed using both Begg and Egger tests.

RESULTS

Overall, 34 case-control studies with 7257 T2DM patients and 15,598 controls, and 12 case-control studies (10,264 T1DM patients and 9031 health controls) were included in the analysis. A significantly lower association was observed between the rs1800795 polymorphism and T2DM risk in Asians, mixed population, and hospital-based (HB) subgroups (C-allele vs. G-allele: OR = 0.76, 95% CI  0.58-0.99, P = 0.039 for Asians; CG vs. GG: OR = 0.74, 95% CI  0.58-0.94, P = 0.014 for mixed population; CC vs. GG: OR = 0.61, 95% CI  0.41-0.90, P = 0.014 for HB). However, increased associations were found from total, mixed population, and HB subgroups between rs1800795 polymorphism and T1DM susceptibility (CG vs. GG: OR = 1.32, 95% CI 1.01-1.74, P = 0.043 for total population, CC vs. GG: OR = 2.45, 95% CI 1.18-5.07, P = 0.016 for mixed individuals; C-allele vs. G-allele: OR = 1.29, 95% CI 1.07-1.56, P = 0.0009 for HB subgroup).

CONCLUSIONS

In summary, there is definite evidence to confirm that IL-6 rs1800795 polymorphism is associated with susceptibility to decreased T2DM and increased T1DM.

Association between polymorphisms of cytokine genes and diabetic nephropathy: A comprehensive systematic review and meta-analysis

AIM

Diabetic nephropathy (DN) is one of the microvascular complications of diabetes, leading to renal failure. In this study, we sought to systematically investigate the cytokine gene polymorphisms association with DN.

METHODS

A structured bibliographic search on PubMed, Scopus, and EMBASE databases has been performed to identify related papers. The odds ratio and corresponding 95% confidence intervals (CIs) were calculated to estimate the association.

RESULTS

Overall, the pooled results showed that the dominant models of TNF-α rs1800629, IL-1β rs16944, IL-8 rs4073, and IL-10 rs1800896 were associated with increased susceptibility to DN. Also, the pooled analyses of the mutant allele vs wild allele of TNF-α rs1800629, rs1799964, IL-1β rs16944, and IL-8 rs4073 were associated with increased susceptibility to DN. Rs1800629, rs16944, rs4073, and rs1800896 polymorphisms were significantly associated with DN susceptibility, suggesting its potential use as a genetic risk marker in the population.

Association between diabetic retinopathy and polymorphisms of cytokine genes: a systematic review and meta-analysis

INTRODUCTION

Diabetic retinopathy (DR) is a medical condition caused by damage to the blood vessels of retina tissue due to diabetes mellitus. DR leads to injury in neural and vascular structures and is reported to be significantly influenced by inflammation and inflammatory mediators like cytokines. In this study, a systematic review and meta-analysis were performed to analyze the association between cytokine gene polymorphisms and DR.

METHODS

We identified relevant studies from Scopus, PubMed, and Google scholar databases. Allele and genotype frequencies were pooled. Heterogeneity and publication bias were explored. The odds ratio (OR) and corresponding 95% confidence intervals (CIs) were calculated to estimate the relation.

RESULTS

A total of 3337 cases and 4945 controls in 19 eligible studies were included in the meta-analysis. Overall, results indicated the negative association between the cytokine gene polymorphisms and DR susceptibility in the allelic model (IFN-γ (rs2430561): OR 0.64, [CI]: 0.5 to 0.82; and TGF-β (rs1800471): [OR] = 0.15, [CI]: 0.03 to 0.79); and also, in the dominant model (IFN-γ (rs2430561): OR = 0.4, [CI]: 0.22 to 0.75; and TGF-β (rs1800471): OR = 0.14, [CI]: 0.05 to 0.4).

CONCLUSION

The present study suggests that IFN-γ (rs2430561) and TGF-β (rs1800471) polymorphisms are associated with decreased susceptibility to DR.

The association of interieukin-6 polymorphism (rs1800795) with microvascular complications in Type 2 diabetes mellitus

Objectives: To evaluate the effects of the single-nucleotide polymorphism (SNP) rs1800795 in interieukin-6 (IL-6) gene on diabetic microvascular complications of Type 2 diabetes mellitus (T2DM), using statistical meta-analysis.

Methods: Literature pertaining to the relationship between the SNP rs1800795 and microvascular complications of T2DM including diabetic retinopathy, diabetic nephropathy, diabetic neuropathy and foot disease was retrieved from PubMed, Web of Science Knowledge and SinoMed databases. Original information was analyzed using Stata 12.0, including meta-analysis statistics, test for heterogeneity, evaluation of publication bias and sensitivity. Subgroup analysis was conducted to assess the effect of specific factors on the corresponding results.

Results: In total, 14 eligible articles were obtained. The SNP rs1800795 in IL-6 gene is not correlated with risk of microvascular complications in T2DM. Among the original literature, a genetic model (OR = 1.071, 95% CI: 0.681–1.685, P=0.767), an allelic genetic model (OR = 1.010, 95% CI: 0.959–1.063, P=0.703), a heterozygote genetic model (OR = 1.107, 95% CI: 0.916–1.339, P=0.292), a dominant genetic model (OR = 1.108, 95% CI: 0.885–1.387, P=0.372), and a recessive genetic model (OR = 0.978, 95% CI: 0.646–1.478, P=0.917) were included respectively. In the subgroup analysis by types of diabetic microvascular complications, we found no correlation between the SNP rs1000795 polymorphism and complications of T2DM in either the homozygote genetic model or the allelic genetic model (P<0.05).

Conclusion: Our results demonstrate that rs1800795 polymorphism in IL-6 gene is not correlated with the susceptibility of microvascular complications of T2DM.

The role of IL-6-174 G/C polymorphism and intraocular IL-6 levels in the pathogenesis of ocular diseases: a systematic review and meta-analysis

Interleukin-6 (IL-6) is one of the key regulators behind the inflammatory and pathological process associated with ophthalmic diseases. The role of IL-6-174 G/C polymorphism as well as intraocular IL-6 levels among various eye disease patients differ across studies and has not been systematically reviewed. Thus, this study aims to provide a summary to understand the relationship between IL-6 and ophthalmic disease. In total, 8,252 and 11,014 subjects for IL-6-174 G/C and intraocular levels of IL-6, respectively, were retrieved from PubMed, Scopus and Web of Science. No association was found between IL-6-174 G/C polymorphisms with ocular diseases. Subgroup analyses revealed a suggestive association between the GC genotype of IL-6-174 G/C with proliferative diabetic retinopathy (PDR). Further, the level of intraocular IL-6 among ocular disease patients in general was found to be higher than the control group [standardized mean difference (SMD) = 1.41, 95% confidence interval (CI) 1.24-1.58, P < 0.00001]. Closer examination through subgroup analyses yielded similar results in several ocular diseases. This study thus indicates that the IL-6-174 G/C polymorphism does not predispose patients to ocular disease, although the GC genotype is likely to be a genetic biomarker for PDR. Moreover, intraocular IL-6 concentrations are related to the specific manifestations of the ophthalmic diseases. Further studies with larger sample sizes are warranted to confirm this conclusion.

Association between diabetic retinopathy and interleukin-related gene polymorphisms: a machine learning aided meta-analysis

BACKGROUND

Diabetic retinopathy (DR) is a severe complication of diabetes and a common cause of visual loss in adults. We aimed to assess the correlation between IL gene-related SNPs and the incidence of DR and attempted to predict DR with combined mutation site detection.

METHODS

A systematic search of databases was performed up to August 2019. Five genetic models were used to analyze associations. Machine learning methods were implemented to improve SNP-related disease prediction.

RESULTS

Sixteen trials assessing a total of 7221 patients were included in our meta-analysis. IL6/rs1800795, rs1800796, and IL10/rs1800896 were analyzed. For the IL-6 gene, there was no significant association between rs1800795 and the incidence of DR (allelic model: OR, 1.091; 95% CI, 0.892-1.334; p = .396). There was no significant correlation between rs1800796 (allelic model: OR, 1.135; 95% CI, 0.678-1.901; p = .63), rs1800896 (allelic model: OR, 1.047; 95% CI, 0.788-1.392; p = .752) and the incidence of DR. Unfortunately, the machine learning results also showed that the combined detection of two SNPs could not accurately predict DR occurrence.

CONCLUSION

rs1800795 and rs1800796 in the IL-6 gene and rs1800896 in IL-10 gene are not related to the incidence of DR. Mutations in multiple SNPs for each DR patient still need to be specifically assessed to increase prediction accuracy.

Association Between IL-6 Polymorphisms and Diabetic Nephropathy Risk: A Meta-analysis

BACKGROUND

The objective of this work was to evaluate the relevance of frequent interleukin-6 (IL-6) polymorphisms and diabetic nephropathy (DN) susceptibility by a systematic meta-analysis.

MATERIALS AND METHODS

The included studies related to the relationship between IL-6 and DN risk were searched from Pubmed, Embase and the Cochrane Library, and the Newcastle-Ottawa Scale was used to evaluate the study quality. A heterogeneity test was performed to determine the appropriate effect models based on the Q test and I² statistic. Odds ratios with 95% confidence intervals were used to determine the strength of associations. Afterwards, subgroup analysis was conducted to assess the effect of specific factors on the corresponding results. Additionally, publication bias and sensitivity analysis were also undertaken.

RESULTS

In total, 11 eligible articles were obtained. The meta-analysis revealed that the "C"allele of IL-6 rs1800795 was related to the decreased risk of DN (C versus G: P = 0.0471). The "G"allele of IL-6 rs1800796 was predominately associated with higher DN risks (GG versus CC: P = 0.0194; GG versus CC + GC: P = 0.0196). The "C"allele of IL-6 rs1800797 was implicated with higher prevalence of DN (C versus G: P = 0.0001; CC versus GG: P = 0.0003; CC versus GG + CG: P = 0.0227; CC + CG versus GG: P = 0.0001) while IL-6 rs2069837 and rs2069840 were not correlated with the susceptibility to DN.

CONCLUSIONS

This meta-analysis indicated that IL-6 rs1800795, rs1800796 and rs1800797 played important roles in DN development while IL-6 rs2069837 and rs2069840 might not be related to DN.

Association of Interleukin-6 -174G/C Polymorphism with the Risk of Diabetic Nephropathy in Type 2 Diabetes: A Meta-analysis

Previous studies reported the association between interleukin-6 (IL-6) -174G/C gene polymorphism and the risk of diabetic nephropathy in type 2 diabetes mellitus (T2DN). However, the results remain controversial. In the present study, we conducted a meta-analysis to further examine this relationship between IL-6-174G/C gene polymorphism and T2DN. Three databases (PubMed, SinoMed and ISI Web of Science) were used to search clinical case-control studies about IL-6-174G/C polymorphism and T2DN published until Apr. 14, 2018. Fixed- or random-effects models were used to calculate the effect sizes of odds ratio (OR) and 95% confidence intervals (95% CI). Moreover, subgroup analysis was performed in terms of the excretion rate of albuminuria. All the statistical analyses were conducted using Stata 12.0. A total of 11 case-control studies were included in this study, involving 1203 cases of T2DN and 1571 cases of T2DM without DN. Meta-analysis showed that there was an association between IL-6-174G/C polymorphism and increased risk of T2DN under the allelic and recessive genetic models (G vs. C: OR=1.10, 95%CI 1.03-1.18, P=0.006; GG vs. CC+GC: OR=1.11, 95%CI 1.02-1.21 P=0.016). In the subgroup analysis by albuminuria, a significant association of IL-6-174G/C polymorphism with risk of T2DN was noted in the microalbuminuria group under the recessive model (OR=1.54, 95% CI 1.02-2.32, _P=0.038). In conclusion, this meta-analysis suggests that IL-6-174G/C gene polymorphism is associated with the risk of T2DN.

Polymorphisms in inflammation-related genes and the risk of primary varicose veins in ethnic Russians

Inflammation was shown to be activated in varicose veins, although its role in the development of vein wall transformation remains inconclusive. We aimed to investigate the influence of 13 inflammation-related single nucleotide polymorphisms (SNPs) TNF rs1800629 and rs3093661, IL1A rs1800587, IL1RN rs4251961, IL6 rs1800795 and rs1800796, IFNG rs2430561, IL10 rs1800896, TGFB1 rs1800469, HIF1A rs11549465, NFKB1 rs28362491, and rs4648068 on the risk of primary varicose veins (PVVs) in ethnic Russians. We genotyped 709 patients with PVVs and 278 individuals without a history of chronic venous disease and performed a single SNP and a haplotype analysis. Several associations with P < 0.05 were revealed in our study. Variant allele HIF1A rs11549465 T, TNF rs3093661 A, and NFKB1 rs28362491 ATTG deletion showed the reverse association with PVV risk, and allele IL6 rs1800795 C was associated with the increased risk of the studied pathology. Haplotype analysis revealed associations of TNF haplotypes rs3093661 A-rs1800629 G and IL6 rs1800795 C-rs1800796 G with the decreased and the increased risk of PVVs, correspondingly. However, all the observed associations failed to reach statistical significance after the correction for multiple testing, which was set at a level of 10^-3 due to many tests performed. Our study therefore provides evidence that investigated polymorphisms do not play a major role in susceptibility to PVVs.

Neurodegeneration and Neuroinflammation in Diabetic Retinopathy: Potential Approaches to Delay Neuronal Loss

In spite of the extensive research the complex pathogenesis of diabetic retinopathy (DR) has not been fully elucidated. For many years it has been thought that diabetic retinopathy manifests only with microangiopathic lesions, which are totally responsible for the loss of vision in diabetic patients. In view of the current knowledge on the microangiopathic changes in the fundus of the eye, diabetic retinopathy is perceived as a neurodegenerative disease. Several clinical tools are available to detect neuronal dysfunction at early stages of diabetes. Many functional changes in the retina can be identified before vascular pathology develops, suggesting that they result from a direct effect of diabetes on the neural retina. In the course of diabetes there is a chronic loss of retinal neurons due to increased frequency of apoptosis. The neuronal apoptosis begins very early in the course of diabetes. This observation has led to suggestions that precautions against DR should be implemented immediately after diabetes is diagnosed. Neurodegeneration cannot be reversed; therefore treatments preventing neuronal cell loss in the retina need to be developed to protect diabetic patients. This review is an attempt to summarize what is currently known about the mechanisms of neuronal apoptosis in the context of diabetic retinopathy and vascular degeneration as well as about potential treatments of DR

Interleukin-6 gene polymorphisms correlate with the progression of nephropathy in Chinese patients with type 2 diabetes: A prospective cohort study

AIMS

Interleukin-6 (IL-6), an inflammatory cytokine, is considered a candidate gene possibly involved in susceptibility to nephropathy in diabetes. This study aimed to examine whether IL-6 polymorphisms predict the progression of nephropathy in a prospective Chinese cohort of patients with type 2 diabetes.

METHODS

A total of 568 type 2 diabetic patients with normoalbuminuria at baseline were followed up for a mean of 5.3±1.5years. Urinary albumin-to-creatinine ratio (ACR) ⩾30mg/g in two consecutive urine tests were defined as progression to diabetic nephropathy (n=143). Five polymorphisms of IL-6 gene, rs1800795, rs1800796, rs1524107, rs2069837, and rs2069840, were genotyped. Cox proportional hazard models were used to estimate hazard ratio (HR) and 95% CI of progression to diabetic nephropathy under different genetic models.

RESULTS

Almost all patients (99.6%) carried the rs1800795 GG homozygous genotypes. In the Cox proportional models adjusted for multiple covariates, the HR under recessive model was 2.02 for rs1800796 GG (vs. CC+CG, 95% CI: 1.08-3.75, p=0.027), 2.37 for rs2069837 GG (vs. AA+AG, 95% CI: 1.15-4.87, p=0.019), and 2.08 for rs1524107 CC (vs. TT+TC, 95% CI: 1.12-3.89, p=0.021). These associations remained significant for rs1800796 and rs1524107 after correction for multiple testing (α=0.017). Overall, our results suggest that rs1800796 GG and rs1524107 CC homozygous genotypes may confer a greater risk for development of nephropathy in type 2 diabetes.

CONCLUSIONS

IL-6 gene polymorphisms rs1800796 and rs1524107 may serve as predictors of progression of nephropathy in Chinese patients with type 2 diabetes.

Circulating interleukin-6 and rheumatoid arthritis: A Mendelian randomization meta-analysis

Interleukin-6 (IL-6), as a pleiotropic cytokine, has been demonstrated to be closely associated with the pathogenisis of rheumatoid arthritis (RA). However, whether this association is causal or not remains unclear, because of the multifactorial role of IL-6 and related confounding factors. We aimed to evaluate the causal relevance between circulating IL-6 levels and the risk of RA through meta-analytical Mendelian randomization approach. IL-6 gene -174G/C variant was selected as an instrument in this Mendelian randomization meta-analysis. Article identification and data collection were conducted in duplicate and independently by 2 authors. The STATA software was used for data analysis. In total, 15 and 5 articles on the association of the -174G/C variant with RA risk and circulating IL-6 level, respectively, were included. The overall analysis showed that C allelic and GC+CC genotype were significantly with 1.59-fold (95% CI: 1.19-2.14) and 1.63-fold (95% CI: 1.17-2.26) increased risk of developing RA, respectively. Asian populations showed stronger association with 4.55-fold (95% CI: 1.62-12.75), 1.84-fold (95% CI: 1.13-2.99), and 4.69-fold (95% CI: 1.68-13.14) increased RA risk in carriers of -174C allelic, CC, and GC+CC genotype, respectively. Carriers of GC+CC genotype showed significant reduction in the circulating IL-6 level compared with GG carriers (WMD = -0.77; 95% CI: -1.16 to -0.38; P = 0.000) in overall populations. Mendelian randomization presented 6% and 22% increased risk of RA with 0.1 pg/mL reduction of circulating IL-6 level in overall and Asian populations, respectively. This Mendelian randomization meta-analysis demonstrated that the long-term genetically reduced circulating IL-6 level might be causally related to a higher risk of RA, especially in Asian populations.

Association of polymorphisms in IL6 gene promoter region with type 1 diabetes and increased albumin-to-creatinine ratio

BACKGROUND

Pro-inflammatory cytokines, such as interleukin-6 (IL-6), have been considered as key factors in type 1 diabetes mellitus (T1DM) and diabetic nephropathy, thus, our aim was to investigate the association of IL6-174G>C (rs1800795) and -634C>G (rs1800796) polymorphisms with T1DM susceptibility and diabetic nephropathy.

METHODS

These polymorphisms were analyzed in 144 children and adolescents with T1DM and 173 normoglycemic control subjects. Glycemic control, laboratory parameters of kidney function and serum lipids were evaluated. By studying only T1DM patients, we evaluated the polymorphisms associated with relevant biochemical parameters in various genetic models.

RESULTS

Type 1 diabetes mellitus patients showed poor glycemic control and albumin-to-creatinine ratio, total cholesterol and LDL-cholesterol levels increased when compared with normoglycemic subjects (p < 0.001, p = 0.004 and p < 0.001, respectively). IL6-174C allele was associated with an increased risk of developing T1DM (OR = 1.53, CI = 1.01-2.31, p = 0.044). In the T1DM group, IL6-174CC carriers showed higher concentrations of glycated hemoglobin (p = 0.029), albumin-to-creatinine ratio (p = 0.021), total cholesterol (p = 0.010), and LDL-cholesterol (p = 0.002), when compared with GG+GC carriers. No association was found for the IL6-634C>G polymorphism.

CONCLUSIONS

These results suggest that IL6-174G>C may contribute to T1DM and increased albumin-to-creatinine ratio as well as to poor glycemic control and hyperlipidemia.

Lack of an association between interleukin-6 -174G/C polymorphism and circulating interleukin-6 levels in normal population: a meta-analysis

Interleukin-6 (IL-6) signaling may play a causal role in the development of coronary heart disease. However, the relationship between IL-6 genotypes and plasma levels of IL-6 appears to be complex. To help clarify the inconsistent findings, we conducted a meta-analysis of the published genetic association studies of the -174 G/C polymorphisms in the IL-6 gene and the circulating IL-6 levels in a normal population. In this meta-analysis, no significant association of IL-6 -174G/C polymorphism and circulating IL-6 levels in a normal population was observed. However, when compared among GG, GC, and CC genotypes, heterogeneity existed among the studies. Sensitivity analysis revealed that, the independent study by Shen et al. influenced the heterogeneity in the homozygous and heterozygous comparison. Although Shen et al.'s study was excluded, no significant association was observed between IL-6 -174G/C polymorphism and circulating IL-6 levels in a normal population [homozygous comparison (GG vs. CC): the pooled standard mean difference (SMD) was -0.01, 95% confidence interval (CI): -0.1-0.08; heterozygous comparison (GC vs. GG or CC): the pooled SMD (GG vs. GC) was -0.05, 95%CI: -0.11-0.01, and the pooled SMD (CC vs. GC) was 0.03, 95%CI: -0.03-0.1]. Under the dominant model, the pooled SMD was -0.05, 95%CI: -0.11-0.01). The meta-analysis provides evidence that the -174G/C polymorphism in the IL-6 gene is not significantly associated with circulating IL-6 levels in a normal population.

Cytokines in diabetic nephropathy

Diabetic nephropathy (DN), the most common cause of end-stage renal disease (ESRD), is increasingly considered an inflammatory process characterized by leukocyte infiltration at every stage of renal involvement. Cytokines act as pleiotropic polypeptides that regulate inflammatory and immune responses, providing important signals in the pathologic and physiologic processes. Inflammation and activation of the immune system are closely involved in the pathogenesis of diabetes and its microvascular complications. Proinflammatory, Th1, Th2, and Th17 cytokines, as well as TGF-beta, all take part in the development and progression of DN. Gene polymorphism of cytokines and their receptors may have functional variations and can be applied to predict the susceptibility and progression to DN. Improved knowledge on recognizing cytokines as significant pathogenic mediators in DN leaves opens the possibility of new potential therapeutic agents for future clinical treatments.

Increased spontaneous production of VEGF by CD4+ T cells in type 1 diabetes

In the present study we report that CD4(+) T cells from patients with type 1 diabetes produce significantly higher amounts of VEGF than respective cells from the healthy individuals. Among CD4(+) T cells memory subsets were the main source of VEGF. In addition, memory CD4(+) T subsets were the most numerous in patients with diabetic retinopathy (DR). DR was also characterized by significant increase of VEGF concentration in serum and culture supernatants. Hence, these data indicate that there is a sustained spontaneous production of VEGF by CD4(+) T cells in type 1 diabetes, which is additionally exacerbated in DR. In our opinion alterations in the proportions of CD4(+) T cell subsets and their VEGF production may be a useful tool for early assessment of the risk of DR onset and progression.