Association analysis of -429T/C and -374T/A polymorphisms of receptor of advanced glycation end products (RAGE) gene in Malaysian with type 2 diabetic retinopathy

Mammalian Diaphanous1 signalling in neurovascular complications of diabetes

Over the past few decades, diabetes gradually has become one of the top non-communicable disorders, affecting 476.0 million in 2017 and is predicted to reach 570.9 million people in 2025. It is estimated that 70 to 100% of all diabetic patients will develop some if not all, diabetic complications over the course of the disease. Despite different symptoms, mechanisms underlying the development of diabetic complications are similar, likely stemming from deficits in both neuronal and vascular components supplying hyperglycaemia-susceptible tissues and organs. Diaph1, protein diaphanous homolog 1, although mainly known for its regulatory role in structural modification of actin and related cytoskeleton proteins, in recent years attracted research attention as a cytoplasmic partner of the receptor of advanced glycation end-products (RAGE) a signal transduction receptor, whose activation triggers an increase in proinflammatory molecules, oxidative stressors and cytokines in diabetes and its related complications. Both Diaph1 and RAGE are also a part of the RhoA signalling cascade, playing a significant role in the development of neurovascular disturbances underlying diabetes-related complications. In this review, based on the existing knowledge as well as compelling findings from our past and present studies, we address the role of Diaph1 signalling in metabolic stress and neurovascular degeneration in diabetic complications. In light of the most recent developments in biochemical, genomic and transcriptomic research, we describe current theories on the aetiology of diabetes complications, highlighting the function of the Diaph1 signalling system and its role in diabetes pathophysiology.

Polymorphisms −374 T/A and −429 T/C of the Receptor for Advanced Glycation End-Products (RAGE) and Serum Levels of RAGE (sRAGE) Are Not Associated with Metabolic Syndrome

RAGE is a multi-ligand transmembrane glycoprotein that promotes biological signals associated with inflammatory responses and degenerative diseases. sRAGE is a soluble variant, proposed as an inhibitor of RAGE activity. −374 T/A and −429 T/C polymorphisms of the advanced glycation end products receptor AGER gene are associated with the development of some diseases, such as type of cancer, cardiovascular disease, and micro and macrovascular disease in diabetes among others but their role in metabolic syndrome (MS) is still unknown. We studied 80 healthy men without MS, and 80 men with MS according to the harmonized criteria. −374 T/A and −429 T/C polymorphisms were genotyped by RT-PCR, and sRAGE was measured by ELISA. Allelic and genotypic frequencies did not differ between Non-MS and MS groups (−374 T/A p = 0.48, p = 0.57 and −429 T/C p = 0.36, p = 0.59). Significant differences were found in fasting glucose levels and diastolic blood pressure among the genotypes of the −374 T/A polymorphism in the Non-MS group (p < 0.01 and p = 0.008). Glucose levels were different between −429 T/C genotypes in the MS group (p = 0.02). sRAGE levels were similar in both groups, but in the Non-MS group showed a significant difference between individuals with only 1 or 2 components of the metabolic syndrome (p = 0.047). However, no associations of any SNP with MS were found (recessive model p = 0.48, dominant model p = 0.82 for −374 T/A; recessive model p = 0.48, dominant model p = 0.42 for −429 T/C). −374 T/A and −429 T/C polymorphisms are not associated with MS in Mexican population and have no influence on serum sRAGE levels.

Endogenous advanced glycation end products in the pathogenesis of chronic diabetic complications

Diabetes is a common metabolic illness characterized by hyperglycemia and is linked to long-term vascular problems that can impair the kidney, eyes, nerves, and blood vessels. By increasing protein glycation and gradually accumulating advanced glycation end products in the tissues, hyperglycemia plays a significant role in the pathogenesis of diabetic complications. Advanced glycation end products are heterogeneous molecules generated from non-enzymatic interactions of sugars with proteins, lipids, or nucleic acids via the glycation process. Protein glycation and the buildup of advanced glycation end products are important in the etiology of diabetes sequelae such as retinopathy, nephropathy, neuropathy, and atherosclerosis. Their contribution to diabetes complications occurs via a receptor-mediated signaling cascade or direct extracellular matrix destruction. According to recent research, the interaction of advanced glycation end products with their transmembrane receptor results in intracellular signaling, gene expression, the release of pro-inflammatory molecules, and the production of free radicals, all of which contribute to the pathology of diabetes complications. The primary aim of this paper was to discuss the chemical reactions and formation of advanced glycation end products, the interaction of advanced glycation end products with their receptor and downstream signaling cascade, and molecular mechanisms triggered by advanced glycation end products in the pathogenesis of both micro and macrovascular complications of diabetes mellitus.

The first association study of Protein Tyrosine Phosphatase, Non-Receptor Type 2 (PTPN2) gene polymorphisms in Malaysian patients with Crohn's disease

Crohn's disease (CD) is one of the sub-entities of Inflammatory Bowel Disease which causes chronic inflammation in the gastrointestinal tract. The development of CD has shown to have a strong genetic association. Therefore, the present study aimed to investigate the association between genetic polymorphisms in a susceptible locus of CD, the protein tyrosine phosphatase, non-receptor type 2 (PTPN2) gene and the development of CD in Malaysian patients. A total of 137 CD patients and 274 matched healthy controls were recruited in the present study. Genomic DNA was extracted from the venous blood of participants and five targeted single nucleotide polymorphisms (SNPs) in the PTPN2 gene were genotyped using polymerase chain reaction. Associations between the SNPs and CD were determined using Fisher's exact test and odds ratio. Findings showed that all five selected SNPs were not significantly associated with the development of CD in Malaysian patients, which was in contrast to studies among the European populations. Malaysian Chinese with rs487273 heterozygous G/T genotype was found to have a lower occurrence of CD (P-value = 0.0253; OR = 0.4396). Patients with rs2542152 homozygous T genotype were associated with stricturing behaviour (P-value = 0.0302, OR = 2.9944). The rs16939895 A/G genotype was associated with inflammation at the ileum site (P-value = 0.0387, OR = 2.2105)while homozygous G genotype was associated with colonic CD (P-value = 0.0164, OR = 2.3917). Functional studies of these SNPs are needed to evaluate their potential use as a biomarker for disease phenotypes among Asian patients.

Single nucleotide variants of receptor for advanced glycation end-products (AGER) gene: is it a new opening in the risk assessment of diabetic retinopathy?-a review

BACKGROUND

Diabetic retinopathy (DR) is a common microvascular complication of diabetes. There is strong evidence suggesting that DR has an inheritable component. The interaction between advanced glycation end products (AGEs) and their receptor is integral in the pathogenesis of diabetic retinopathy and its various complications, retinopathy being one of them.

OVERVIEW AND METHODOLOGY

This review discusses the existing literature on the association between single nucleotide variants (SNV) of AGER gene and the risk of DR. It also discusses the current understanding of the AGE-AGER pathway in diabetic retinopathy. Through our article we have tried to consolidate all the available information about these SNVs associated with diabetic retinopathy in a succinct tabular form. Additionally, a current understanding of the AGE-AGER interaction and its deleterious effects on the cells of the retina has been discussed in detail to provide comprehensive information about the topic to the reader. A literature review was performed on PubMed, Cochrane Library, and Google Scholar for studies to find existing literature on the association between AGER gene SNVs and the risk, progression and severity of developing DR. This article will encourage scientific communication and discussion about possibly devising genetic markers for an important cause of blindness both in developed and developing countries, i.e., diabetic retinopathy.

RESULT

Based on genetic studies done in Indian and Chinese population G82S(rs2070600) was positively associated with Diabetic Retinopathy. Patients of diabetic retinopathy in Caucasian population had -T374A(rs1800624) polymorphism. + 20T/A was found to be associated with the disease in a study done in UK. Association with G1704T(rs184003) was seen in Chinese and Malaysian population. A Chinese study found its association with CYB242T. -T429C(rs1800625) SNV was not associated with DR in any of the studies. G2245A(rs55640627) was positively associated with the disease process in Malaysian population. It was not associated in Malaysian and Chinese population. Promoter variant rs1051993 has also been found to a susceptible SNV in the Chinese population.

CONCLUSION

While providing a comprehensive review of the existing information, we would like to emphasize on a large, multi-centric, trial with a much larger and varied population base to definitely determine these single nucleotide variants predisposing diabetic individuals.

Susceptibility of six polymorphisms in the receptor for advanced glycation end products to type 2 diabetes: a systematic review and meta-analysis

We did a systematic review and meta-analysis, aiming to examine the association of available polymorphisms in the receptor for advanced glycation end products (AGER) gene with the risk of type 2 diabetes. Literature search, eligibility assessment, and data extraction were independently performed by two authors. Risk was expressed as by odds ratio (OR) and 95% confidence interval (CI) under the random-effects model. A total of 26 publications, involving 29 independent studies (8,318 patients with type 2 diabetes and 5,589 healthy or orthoglycemic controls) were included in this meta-analysis. Six polymorphisms in AGER gene, rs2070600, rs1800624, rs1800625, rs184003, rs3134940, and rs55640627, were eligible for inclusion. Overall analyses indicated that the mutations of rs1800624 (-374A) and rs55640627 (2245A) were associated with a significantly increased risk of type 2 diabetes (OR = 1.17 and 1.55, 95% CI: 1.00 to 1.38 and 1.21 to 1.98, respectively). Subsidiary analyses revealed that the mutation of rs2070600 was associated with 2.13-folded increased risk of type 2 diabetes in Caucasians (95% CI: 1.28 to 3.55), and the mutation of rs1800624 was associated with 1.57-folded increased risk in South Asians (95% CI: 1.09 to 2.25), with no evidence of heterogeneity (I²: 42.5% and 44.5%). There were low probabilities of publication bias for all studied polymorphisms. Taken together, our findings indicate an ethnicity-dependent contribution of AGER gene in the pathogenesis of type 2 diabetes, that is, rs2070600 was a susceptibility locus in Caucasians, yet rs1800624 in South Asians.

Genetics of Diabetic Retinopathy, a Leading Cause of Irreversible Blindness in the Industrialized World

Diabetic retinopathy (DR) is a chronic complication of diabetes and a leading cause of blindness in the industrialized world. Traditional risk factors, such as glycemic control and duration of diabetes, are unable to explain why some individuals remain protected while others progress to a more severe form of the disease. Differences are also observed in DR heritability as well as the response to anti-vascular endothelial growth factor (VEGF) treatment. This review discusses various aspects of genetics in DR to shed light on DR pathogenesis and treatment. First, we discuss the global burden of DR followed by a discussion on disease pathogenesis as well as the role genetics plays in the prevalence and progression of DR. Subsequently, we provide a review of studies related to DR’s genetic contribution, such as candidate gene studies, linkage studies, and genome-wide association studies (GWAS) as well as other clinical and meta-analysis studies that have identified putative candidate genes. With the advent of newer cutting-edge technologies, identifying the genetic components in DR has played an important role in understanding DR incidence, progression, and response to treatment, thereby developing newer therapeutic targets and therapies.

Association analysis of 374T/A (rs1800624) receptor for advanced glycation end-products (RAGE) gene polymorphism with diabetic retinopathy in Pakistani patients

OBJECTIVES

to determine the relationship of 374T/A (rs1800624) polymorphism in the gene encoding RAGE with Type-2 diabetes mellitus (T2DM), diabetic retinopathy (DR) and serum soluble RAGE (sRAGE) level in Pakistani patients.

METHODS

A case-control study, conducted from January 2017 to December 2018, involving 150 healthy controls (HC), 150 T2DM patients with no retinopathy (DNR) and 150 DR patients diagnosed by coloured fundus photography. Tetra-primer amplification refractory mutation system - polymerase chain reaction (T-ARMS-PCR) was used for genotyping. Serum sRAGE levels were measured by enzyme-linked immunosorbent assays (ELIZA).

RESULTS

The frequency of TT, TA and AA genotypes of rs1800624 polymorphism were: 92.7%, 6%, 1.3% in HC, 80%, 17.3%, 2.7% in DNR and 76.7%, 19.3%, 4.3% in DR groups. Heterozygous TA genotype and mutant A allele showed significant association with diabetes and DR vs HC. In dominant model, mutant allele showed significant association with DNR and DR vs HC. No significant association of rs1800624 was detected with DR and its sub-groups, non-proliferative DR (NPDR) and proliferative DR (PDR) vs DNR. Dividing NPDR into mild, moderate and severe, heterozygous TA genotype showed significant association with moderate and severe NPDR vs DNR. In DNR and DR groups, TA genotype was significantly associated with raised sRAGE.

CONCLUSION

rs1800624 RAGE gene polymorphism might be a risk factor for T2DM and NPDR in Pakistani patients. Raised sRAGE levels have a positive correlation with PDR and are associated with heterozygosity of rs1800624 polymorphism in DNR and DR groups.

Polymorphisms of the receptor for advanced glycation end products as vasculopathy predictor in sickle cell disease

BACKGROUND

The genetic variants of the receptor for advanced glycation end products (RAGE) gene have been associated with vascular disease risk. The objective of this work was to explore the association of three single-nucleotide polymorphisms (SNPs) of RAGE gene (374T/A, 429T/C, and G82S) with vascular complications in SCD.

METHODS

The study was conducted on 40 children with SCD and 40 healthy children served as controls. All participants were genotyped for the three studied RAGE polymorphisms by polymerase chain reaction (PCR).

RESULTS

Regarding 374T/A polymorphism, the frequency of TA, TT genotypes and T allele were higher in patients (p < 0.001). T allele was associated with higher incidence of sickling crisis and stroke (p < 0.05). In the subgroup analyses of 429T/C polymorphism, an association between C allele and SCD vascular complications was observed (p < 0.05). Concerning the frequency of G82S genotypes of RAGE, GG variant was detected in 39 (97.5%) of the patients, as compared with 40 (100%) of controls (p = 0.3). A regression analysis proved that HbS%, serum ferritin, and the -374T and 429C alleles were significant independent predictors of frequent sickling episodes (p < 0.05).

CONCLUSIONS

The C allele of -429T/C and T allele of 374T/A RAGE polymorphisms may be considered as predictors for vascular dysfunction in SCD.

IMPACT

The C allele of -429T/C and T allele of 374T/A RAGE polymorphisms may be considered as predictors for vascular dysfunction in SCD patients. To our knowledge, our study is the first exploring the association of three single-nucleotide polymorphisms of RAGE gene (374T/A, 429T/C, and G82S) with vascular complications in SCD. Early identification of patients carrying these genetic variants might be of great importance not only to identify subjects at risk of vasculopathy but also to direct them to RAGE-targeted treatments.

Oxidative Stress as the Main Target in Diabetic Retinopathy Pathophysiology

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus (DM) causing vision impairment even at young ages. There are numerous mechanisms involved in its development such as inflammation and cellular degeneration leading to endothelial and neural damage. These mechanisms are interlinked thus worsening the diabetic retinopathy outcome. In this review, we propose oxidative stress as the focus point of this complication onset.

Pathological Implications of Receptor for Advanced Glycation End-Product (AGER) Gene Polymorphism

The receptor for advanced glycation end-products (RAGE) is a cell surface transmembrane multiligand receptor, encoded by the AGER gene. RAGE presents many transcripts, is expressed mainly in the lung, and involves multiple pathways (such as NFκB, Akt, p38, and MAP kinases) that initiate and perpetuate an unfavorable proinflammatory state. Due to these numerous functional activities, RAGE is implicated in multiple diseases. AGER is a highly polymorphic gene, with polymorphisms or SNP (single-nucleotide polymorphism) that could be responsible or co-responsible for disease development. This review was designed to shed light on the pathological implications of AGER polymorphisms. Five polymorphisms are described: rs2070600, rs1800624, rs1800625, rs184003, and a 63 bp deletion. The rs2070600 SNP may be associated with the development of human autoimmune disease, diabetes complications, cancer, and lung diseases such as chronic obstructive pulmonary disease and acute respiratory distress syndrome. The rs1800624 SNP involves AGER gene regulation and may be related to reduced risk of heart disease, cancer, Crohn's disease, and type 1 diabetes complications. The rs1800625 SNP may be associated with the development of diabetic retinopathy, cancer, and lupus but may be protective against cardiovascular risk. The rs184003 SNP seems related to coronary artery disease, breast cancer, and diabetes. The 63 bp deletion may be associated with reduced survival from heart diseases during diabetic nephropathy. Here, these potential associations between AGER polymorphisms and the development of diseases are discussed, as there have been conflicting findings on the pathological impact of AGER SNPs in the literature. These contradictory results might be explained by distinct AGER SNP frequencies depending on ethnicity.

Association between the RAGE (receptor for advanced glycation end-products) -374T/A gene polymorphism and diabetic retinopathy in T2DM

OBJECTIVE

Interaction between advanced glycation end-products (AGEs) and receptor for AGEs (RAGE) in cells could affect both extracellular and intracellular structure and function, which plays a pivotal role in diabetic microvascular complications. The results from previous epidemiological studies on the association between RAGE gene -374T/A polymorphism and diabetic retinopathy (DR) risk were inconsistent. Thus, we conducted this meta-analysis to summarize the possible association between RAGE -374T/A polymorphism and DR risk.

METHOD

We searched all relevant articles on the association between RAGE -374T/A polymorphism and DR risk from PubMed, Cochrane Library, ScienceDirect, Wanfang, VIP and Chinese National Knowledge Infrastructure (CNKI) web databases up to August 2016. Odds ratio (OR) with 95% confidence interval (CI) were calculated to assess those associations. All analyses were performed using the Review Manager software.

RESULTS

Nine case-control studies, including 1,705 DR cases and 2,236 controls were enrolled, and the results showed that the A allele of RAGE -374T/A polymorphism was significantly associated with increased DR risk in dominant model (TA/AA vs. TT: OR=1.22, 95CI 1.05-1.41, p=0.006) and heterozygote model (TA vs. TT: OR=1.26, 95CI 1.07-1.47, p=0.005). The subgroup analysis by ethnicity showed that significantly increased DR risk was found in both Asian and Caucasian populations.

CONCLUSION

This meta-analysis reveals that the A allele of RAGE -374T/A polymorphism probably increase DR risk.

Association of RAGE gene polymorphism with Type-2 diabetes mellitus in local population

Objectives:

Type-2 diabetes mellitus (T2DM) is an endocrine disease having a significant genetic component. Polymorphisms of many genes may affect hereditary vulnerability of the disease that is characterized by insulin resistance and islet disorder. As the genetic basis of T2DM can vary between ethnic groups, it is important to investigate the genetic link of T2DM in Pakistani populace. This study was aimed to assess the association of receptor for advanced glycation end product (RAGE) gene polymorphism (-429T>C) with Type-2 diabetes mellitus within local populace.

Methods:

Genomic DNA was isolated by following kit protocol. Genotyping of the RAGE gene was studied by PCR-RFLP on genomic DNA. All research work was done in molecular biochemistry laboratory (MBL), University of Agriculture Faisalabad and Postgraduate Laboratory, The University of Faisalabad, Pakistan from December 2016 to July 2017.

Results:

We found distribution of -429T>C genotypes between T2DM and healthy controls as 24.7% (tt), 24.7% (Tt) and 50.7% (TT). The outcomes were highly compatible statistically.

Conclusion:

The techniques of PCR and RFLP when performed simultaneously can be helpful in tracing vital information regarding polymorphism of AGE receptor.

Association of genetic variants in the receptor for advanced glycation end products gene with diabetic retinopathy: A meta-analysis

BACKGROUND

Diabetic retinopathy (DR) is a major sight-threatening diabetic complication. Previous studies have examined the association of DR with multiple genetic variants in the receptor for advanced glycation end products (RAGE) gene, with inconsistent results.

OBJECTIVE

To perform a systematic literature search and conduct meta-analyses to examine the association of genetic variants in RAGE with DR.

DATA SOURCES

PubMed, Cochrane Library, Embase, Google Scholar, and HuGE.

STUDY ELIGIBILITY CRITERIA AND PARTICIPANTS

Studies were on human subjects; the studies were case-control ones and included subjects who had DR and those who did not have DR; and the studies provided genotype data for genetic variants in RAGE, separately for subjects who had and did not have DR, or provided odds ratios (ORs) and the 95% confidence intervals (CIs), or provided sufficient data for the calculation of OR and the 95% CI.

STUDY APPRAISAL AND SYNTHESIS METHODS

We used OR as a measure of association, and used random-effects model in all the meta-analyses. Between-study heterogeneity was assessed using I, and publication bias was evaluated using Egger test.

RESULTS

A total of 13 studies met the eligibility criteria and were included in our analyses. We found that Gly82Ser was significantly associated with DR (OR = 2.40, 95% CI: 1.46-3.97; P = 0.001) using a recessive model. -374T/A also showed significant association with DR under a dominant model (OR = 1.21, 95% CI: 1.03-1.43; P = 0.023). We did not find a significant association of DR with other genetic variants in RAGE.

LIMITATIONS

The number of included studies is small for some genetic variants; duration of diabetes varied across studies; most studies were conducted in Asia; and it is not clear whether the observed association can be generalized to other ethnicities; and we could not control for other potential confounding factors.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

We found that Gly82Ser in RAGE showed significant association with DR. More studies with larger sample sizes that control for important risk factors, such as duration of diabetes, are needed to validate our findings.

Polymorphism 2184A/G in the AGER gene is not associated with diabetic retinopathy in Han Chinese patients with type 2 diabetes

OBJECTIVE

To assess the association between the 2184A/G polymorphism in the advanced glycosylation end product-specific receptor (AGER) gene and the susceptibility to diabetic retinopathy (DR) in Han Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

This cross-sectional genotyping study included patients with T2DM with and without DR. Genotype and allele frequencies of the 2184A/G polymorphism were detected using polymerase chain reaction-restriction fragment-length polymorphism analysis.

RESULTS

This study included 943 patients with T2DM (285 with DR [DR group] and 658 without DR [NDR group]). There were no significant differences in age, sex, body mass index, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, diastolic blood pressure, glycosylated haemoglobin, fasting blood glucose, postprandial 2-hour blood glucose, and triglycerides between the two groups. The duration of T2DM and systolic blood pressure were significantly increased in the DR group compared with the NDR group. No significant differences were found in allele (A and G) and genotype (AA, AG and GG) frequencies of the 2184A/G polymorphism between the two groups.

CONCLUSION

The 2184A/G polymorphism in the AGER gene is not associated with DR in Han Chinese patients with T2DM.

Update on genetics and diabetic retinopathy

Clinical risk factors for diabetic retinopathy (DR), such as duration of disease and degree of glucose control, do not adequately predict disease progression in individual patients, suggesting the presence of a genetic component. Multiple smaller studies have investigated genotype–phenotype correlations in genes encoding vascular endothelial growth factor, aldose reductase, the receptor for advanced glycation end products, and many others. In general, reported results have been conflicting, due to factors including small sample sizes, variations in study design, differences in clinical end points, and underlying genetic differences between study groups. At this time, there is no confirmed association with any risk allele reported. As we continue to collect data from additional studies, the role of genetics in DR may become more apparent.

Rs1800625 in the receptor for advanced glycation end products gene predisposes to sepsis and multiple organ dysfunction syndrome in patients with major trauma

Introduction

The receptor for advanced glycation end products (RAGE) is a transmembrane receptor of the immunoglobulin superfamily, it plays pivotal roles in the pathogenesis of sepsis in several ways. Our previous study showed that rs1800625 (−429T/C) revealed a strong clinical relevance with sepsis morbidity rate and multiple organ dysfunction syndrome (MODS) in patients with major trauma. In this study, we enlarged the sample size, added two validation populations and examined the expression of RAGE on the surface of peripheral leukocytes to ex vivo lipopolysaccharide (LPS) stimulation in subjects with different genotypes.

Methods

Rs1800625 was genotyped using pyrosequencing in 837 Chinese Han patients with major trauma in Chongqing. We then validated the clinical relevance in 340 Zhejiang and 347 Yunnan patients. The expression of RAGE on the surface of peripheral blood mononuclear cells was measured by flow cytometric analysis.

Results

The results indicated that rs1800625 was significantly associated with sepsis morbidity rate and MODS in patients with major trauma in the Chongqing, Zhejiang and Yunnan districts. Patients with CC genotype had lower sepsis morbidity rate and MODS after major trauma. Furthermore, patients with CC genotype had significantly higher RAGE expression (P = 0.009).

Conclusions

The rs1800625 polymorphism is a functional single nucleotide polymorphism and confers host susceptibility to sepsis and MODS in patients with major trauma.

Association of 2184AG Polymorphism in the RAGE Gene with Diabetic Nephropathy in Chinese Patients with Type 2 Diabetes

OBJECTIVE

The interaction between advanced glycation end products and their cellular receptor (RAGE) has an important role in the pathogenesis of diabetic microvascular complications. The aim of this study was to investigate the relationship between the 2184A/G polymorphism in the RAGE gene and diabetic nephropathy in Chinese Han patients with type 2 diabetes mellitus.

METHODS

A total of 868 patients with type 2 diabetes mellitus (486 without and 382 with diabetic nephropathy) were enrolled in this study. The genotype and allele frequencies of the 2184A/G polymorphism were detected using the polymerase chain reaction-restriction fragment-length polymorphism method.

RESULTS

The G allele and AG + GG genotype frequencies in patients with diabetic nephropathy were significantly lower than those in patients without diabetic nephropathy (P = 0.001 and P = 0.005, resp.). After adjustments for possible confounders, multivariate logistic regression analyses showed that the 2184A/G polymorphism was independently associated with diabetic nephropathy (OR = 0.46, 95% CI: 0.22-0.92, P = 0.028).

CONCLUSIONS

Our study indicated that the 2184A/G polymorphism in the RAGE gene was significantly associated with diabetic nephropathy in Chinese Han patients with type 2 diabetes.

Genetics of diabetes complications

Chronic hyperglycemia and duration of diabetes are the major risk factors associated with development of micro- and macrovascular complications of diabetes. Although it is believed that hyperglycemia induces damage to the particular cell subtypes, e.g., mesangial cells in the renal glomerulus, capillary endothelial cells in the retina, and neurons and Schwann cells in peripheral nerves, the exact mechanisms underlying these damaging defects are not yet well understood. Clustering of micro- and macrovascular complications in families of patients with diabetes suggests a strong genetic susceptibility. However, until now only a handful number of genetic variants were reported to be associated with either nephropathy (ACE, ELMO1, FRMD3, and AKR1B1) or retinopathy (VEGF, AKR1B1, and EPO), and only a few studies were carried out for genetic susceptibility to cardiovascular diseases (ADIPOQ, GLUL) in patients with diabetes. It is, therefore, obvious that the accumulation of more data from larger studies and better phenotypically characterized cohorts is needed to facilitate genetic discoveries and unravel novel insights into the pathogenesis of diabetic complications.

Association of RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms with diabetic retinopathy in T2DM patients from north India

AIMS

The present study aimed to examine the association of RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms with diabetic retinopathy (DR) in north Indian T2DM patients.

METHODS

In this case-control association study, 758 T2DM patients were recruited. 446 with retinal neovascularization, microneurysms and hemorrhages were considered as cases (DR) and 312 patients with T2DM and no clinical signs of retinopathy (DNR), were recruited as controls. Genotypes for RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms were generated by direct sequencing of amplified products.

RESULTS

Genotype distribution of p.Gly82Ser (RAGE) and p.Val16Ala (MnSOD) polymorphisms were significantly different between DR and DNR (p<0.05) whereas distribution of allele frequency did not differ significantly (p>0.05). A significantly higher frequency of homozygous Ser82 genotype in DR patients was detected compared with DNR (2.4% vs 0.64%) for p.Gly82Ser (RAGE) polymorphism whereas there was a higher frequency of homozygous Ala16 genotype for p.Val16Ala (MnSOD) polymorphism in DR patients compared with DNR (22.6% vs 19.3%). Binary logistic analyses showed an association of homozygous recessive genotype Ser82 with DR (OR: 2.63%, 95% CI: 0.16-15.88, p<0.033) for p.Gly82Ser (RAGE) polymorphism. However, we did not find a significant association of p.Val16Ala polymorphism in MnSOD with retinopathy.

CONCLUSIONS

The findings indicate a statistically significant association of p.Gly82Ser polymorphism in RAGE with DR in T2DM patients.

Association of RAGE gene polymorphism with vascular complications in Indian type 2 diabetes mellitus patients

AIMS

The study was designed to evaluate the association of -374T/A and -429T/C polymorphism in the promoter region and Gly82Ser polymorphism in exon 3 region of RAGE gene with diabetic vascular complications in Indian population.

METHODS

We screened 603 subjects which includes 176 healthy controls, 140 type 2 diabetes mellitus (T2DM) subjects without any vascular complications (DM), 152 T2DM subjects with microvascular complications (DM-micro) and 135 T2DM subjects with macrovascular complications (DM-macro) for -374T/A, -429T/C and Gly82Ser polymorphisms of RAGE gene. DNA isolated from the enrolled subjects were genotyped by PCR-RFLP. Logistic regression analysis was used to evaluate the association of single nucleotide polymorphisms (SNPs).

RESULTS

The -429 T/C and Gly82Ser RAGE polymorphisms were found to be significantly associated with the development of macrovascular and microvascular complications, respectively, in T2DM subjects while -374A allele showed reduced risk towards the development of macrovascular complications. Further, -429T/C, -374T/A and Gly82Ser haplotype analysis revealed association of CTG haplotype with development of macrovascular complications while haplotype TAG was observed to be significantly protective towards development of macrovascular complications in T2DM subjects (OR=0.617, p=0.0202).

CONCLUSIONS

Our data indicates significant association of RAGE SNPs and haplotypes with vascular complications in North Indian T2DM subjects.

Insight into gene polymorphisms involved in toll-like receptor/interferon signalling pathways for systemic lupus erythematosus in South East Asia

Polymorphisms in genes involved in toll-like receptor/interferon signalling pathways have been reported previously to be associated with SLE in many populations. This study aimed to investigate the role of seven single nucleotide polymorphisms within TNFAIP3, STAT4, and IRF5, which are involved in upstream and downstream pathways of type I interferon production, in SLE in the South East Asian populations. Genotyping of 360 Malaysian SLE patients and 430 normal healthy individuals revealed that minor alleles of STAT4 rs7574865 and rs10168266 were associated with elevated risk of SLE in the Chinese and Malay patients, respectively (P = 0.028, odds ratio (OR) = 1.42; P = 0.035, OR = 1.80, respectively). Polymorphisms in TNFAIP3 and IRF5 did not show significant associations with SLE in any of the ethnicities. Combined analysis of the Malays, Chinese, and Indians for each SNP indicated that STAT4 rs10168266 was significantly associated with the Malaysian SLE as a whole (P = 0.014; OR = 1.435). The meta-analysis of STAT4 rs10168266, which combined the data of other studies and this study, further confirmed its importance as the risk factor for SLE by having pooled OR of 1.559 and P value of <0.001.

Association of polymorphisms of the receptor for advanced glycation end products gene with COPD in the Chinese population

The receptor for advanced glycation end products (RAGE) is a cell surface molecule of the immunoglobulin superfamily that binds diverse endogenous ligands involved in the development of chronic diseases and inflammatory damage. A growing body of evidence has suggested that RAGE is involved in the development and progression of chronic obstructive pulmonary disease (COPD). The present study investigated the existence of an association among three polymorphisms (-374T/A, -429T/C, and G82S) of the RAGE gene with the risk of COPD in the Chinese population. The RAGE genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism in 216 patients with COPD and 239 age-matched healthy individuals. Our study demonstrated that the frequencies of the GS genotype and the S allele in the G82S mutation were significantly higher in COPD patients than in controls (odds ratios [OR]=1.70, 95% confidence interval [CI]: 1.15-2.50, p=0.0098 and OR=1.42, 95% CI: 1.06-1.91, p=0.023, respectively). Further stratification analysis by smoking status revealed that the presence of the GS genotype conferred a higher risk of developing COPD in current smokers (p=0.044). In contrast, mutations at -374T/A and -429T/C did not demonstrate any association with COPD, even after taking into account the patients' smoking history. Our study provides preliminary evidence that the G82S polymorphism in the RAGE gene is associated with an increased risk of COPD and that the GS genotype of the G82S variant is a risk factor for COPD in the Chinese population.

Genetics in diabetic retinopathy: current concepts and new insights

There is emerging evidence which indicates the essential role of genetic factors in the development of diabetic retinopathy (DR). In this regard it should be highlighted that genetic factors account for 25-50% of the risk of developing DR. Therefore, the use of genetic analysis to identify those diabetic patients most prone to developing DR might be useful in designing a more individualized treatment. In this regard, there are three main research strategies: candidate gene studies, linkage studies and Genome-Wide Association Studies (GWAS). In the candidate gene approach, several genes encoding proteins closely related to DR development have been analyzed. The linkage studies analyze shared alleles among family members with DR under the assumption that these predispose to a more aggressive development of DR. Finally, Genome-Wide Association Studies (GWAS) are a new tool involving a massive evaluation of single nucleotide polymorphisms (SNP) in large samples. In this review the available information using these three methodologies is critically analyzed. A genetic approach in order to identify new candidates in the pathogenesis of DR would permit us to design more targeted therapeutic strategies in order to decrease this devastating complication of diabetes. Basic researchers, ophthalmologists, diabetologists and geneticists should work together in order to gain new insights into this issue.

Investigation of SLC2A1 26177A/G gene polymorphism via high resolution melting curve analysis in Malaysian patients with diabetic retinopathy

PURPOSE

In this study, we aimed to investigate the possible association between SLC2A1 26177A/G polymorphism and diabetic retinopathy (DR) in Malaysian patients with type 2 diabetes.

METHODS

Genomic DNA was extracted from 211 Malaysian type 2 diabetic patients (100 without retinopathy [DNR], 111 with retinopathy) and 165 healthy controls. A high resolution melting assay developed in this study was used to detect SLC2A1 26177A/G polymorphism followed by statistical analysis.

RESULTS

A statistically significant difference in 26177G minor allele frequency between healthy controls (19.7 %) and total patient group (26.1 %) (p<0.05, Odd ratio = 1.437, 95% Confidence interval = 1.015-2.035) as well as between healthy controls (19.7 %) and DNR patients (27.5%) (p<0.05, Odd ratio = 1.546, 95% Confidence interval = 1.024-2.336) was shown in this study. However, when compared between DR and DNR patients, there was no significant difference (p>0.05).

CONCLUSIONS

This is the first study which shows that SLC2A1 26177G allele is associated with type 2 diabetes in Malaysian population but not with DR.

Identification of haplotype tag single nucleotide polymorphisms within the receptor for advanced glycation end products gene and their clinical relevance in patients with major trauma

INTRODUCTION

The receptor for advanced glycation end products (RAGE) has been considered as one of the major pattern recognition receptors and plays an important role in the development of sepsis and multiple organ dysfunction in critical illnesses. Although genetic variants of the RAGE gene have been shown to be well associated with susceptibility to some inflammatory diseases, little is known about their clinical relevance in the development of sepsis in critical ill patients.

METHODS

Four genetic variants were selected from the entire RAGE gene and genotyped using pyrosequencing and polymerase chain reaction-length polymorphism methods. Association studies were performed in two independent Chinese Han populations.

RESULTS

Among the four genetic variants, only the rs1800625 polymorphism was significantly associated with sepsis morbidity rate and multiple organ dysfunction (MOD) scores in patients with major trauma both in Chongqing (n = 496) and Zhejiang (n = 232) districts, respectively. Results from ex vivo responsiveness of peripheral blood leukocytes indicated that the rs1800625 polymorphism was well associated with decreased production of TNFα. In addition, the rs1800625 polymorphism could significantly inhibit the promoter activities of the RAGE gene.

CONCLUSIONS

The rs1800625 polymorphism is a functional variant, which might be used as a relevant risk estimate for the development of sepsis and multiple organ dysfunction syndrome in patients with major trauma.