Rage gene promoter polymorphisms and diabetic retinopathy in a clinic-based population from South India

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.

Nanopore Sequencing of RAGE Gene Polymorphisms and Their Association with Type 2 Diabetes

The receptor for advanced glycation end products (RAGE) is a transmembrane protein that interacts with its ligands, advanced glycation end products (AGEs). AGEs are elevated in diabetes and diabetic complications, leading to increased oxidative stress and activation of pro-inflammatory pathways facilitated by AGE-RAGE signaling. Polymorphisms in the RAGE gene can potentially affect AGE-RAGE interaction and its downstream signaling, which plays a crucial role in the progression of diabetes and its complications. In this study, we used nanopore sequencing for genotyping of RAGE polymorphism and identified a maximum number of 33 polymorphisms, including two previously unreported novel mutations in a cohort of healthy, type 2 diabetics without nephropathy and type 2 diabetics with nephropathy in order to identify associations. Two novel RAGE polymorphisms in the intron 8 and 3'UTR region at genomic locations 32181834 and 32181132, respectively, were detected with a low frequency. For four previously reported polymorphisms, cross-validation by PCR-RFLP showed 99.75% concordance with nanopore sequencing. Analysis of genotype distribution and allele frequencies revealed that five single nucleotide polymorphisms, i.e., rs1800625, rs3131300, rs3134940, rs2070600, and rs9391855, were associated with an increased risk for type 2 diabetes.

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.

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.

Inhibition of Receptor for Advanced Glycation End Products as New Promising Strategy Treatment in Diabetic Retinopathy

BACKGROUND

Extensive intracellular and extracellular formation of advanced glycation end-products (AGEs) is considered a causative factor for vascular injury triggered by hyperglycemia in diabetes. The hyperglycemia will cause accumulation of AGEs, damage to pericytes, nerve growth factor (NGF), glial acid fibrillary protein (GFAP) and increase in vascular endothelial growth factor (VEGF).

AIM

This study aimed to assess the efficacy of RAGE inhibition in suppressing the development and progression of diabetic retinopathy through modulation of the inflammatory pathway involving NGF, GFAP, and VEGF.

METHODS

The design was in vivo experimental study. Thirty white rats were induced with Alloxan monohydrate. Rats were divided into 5 groups, normal, negative control, groups with an anti-RAGE dose of 1 μg/uL, the dose of 10 μg/uL and 100 μg/uL. After 4 weeks of treatment, HbA1c, NGF, and GFAP levels were measured using ELISA. Quantification of VEGF expression was done using the ImageJ® application. Data was expressed with mean ± SD. Independent T-test with ANOVA and Tukey's post hoc was done.

RESULTS

RAGE inhibitors yielded a significant decrease in blood glucose and HbA1c levels. VEGF and RAGE expression were reduced in anti-RAGE groups in various doses. Inhibition of RAGE reduced the damage of retinal pericytes, by reducing GFAP and increasing NGF, and reduced the formation of new blood vessels, by decreasing VEGF expression, in diabetic retinopathy.

CONCLUSION

Inhibition of receptor for advanced glycation end-products (RAGE) was effective in suppressing the development and progression of diabetic retinopathy.

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.

Candidate gene studies of diabetic retinopathy in human

Diabetic retinopathy (DR) is a multifactorial disease with complex pathophysiology. It is the main cause of blindness among the people in productive age. The purpose of this literature review is to highlight recent achievements in the genetics of diabetic retinopathy with particular focus on candidate gene studies. We summarized most of the available published data about candidate genes for diabetic retinopathy with the goal to identify main genetic aspects. We conclude that genetic studies reported contradictory findings and no genetic variants meet criteria of a diagnostic marker, or significantly elucidate the root of DR development. Based on these findings it is important to continue with the research in the field of DR genetics, mainly due to the fact that currently new possibilities and approaches associated with utilization of next-generation sequencing are available.

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.

Novel Genetic Actors of Diabetes-Associated Microvascular Complications: Retinopathy, Kidney Disease and Neuropathy

Both type 1 and type 2 diabetes mellitus can lead to the common microvascular complications of diabetic retinopathy, kidney disease, and neuropathy. Diabetic patients do not universally develop these complications. Long duration of diabetes and poor glycemic control explain a lot of the variability in the development of microvascular complications, but not all. Genetic factors account for some of the remaining variability because of the heritability and familial clustering of these complications. There have been a large number of investigations, including linkage studies, candidate gene studies, and genome-wide association studies, all of which have sought to identify the specific variants that increase susceptibility. For retinopathy, several genome-wide association studies have been performed in small or midsize samples, but no reproducible loci across the studies have been identified. For diabetic kidney disease, genome-wide association studies in larger samples have been performed, and loci for this complication are beginning to emerge. However, validation of the existing discoveries, and further novel discoveries in larger samples is ongoing. The amount of genetic research into diabetic neuropathy has been very limited, and much is dedicated to the understanding of genetic risk factors only. Collaborations that pool samples and aim to detect phenotype classifications more precisely are promising avenues for a better explanation of the genetics of diabetic microvascular complications.

Regulatory SNPs Alter the Gene Expression of Diabetic Retinopathy Associated Secretary Factors

OBJECTIVES

Diabetic retinopathy (DR) is a common microvascular complication in both type I and type II diabetes. Several previous reports indicated the serum centration of some secretary factors were highly associated with DR. Therefore, we hypothesis regulatory SNPs (rSNPs) genotype in secretary factors may alter these gene expression and lead to DR.

METHODS

At first, pyrosequencing were applying to screen the SNPs which present allele frequency different in DR and DNR. Then individual genotyping was processed by Taqman assays in Taiwanese DR and DNR patients. To evaluate the effect of SNP allele on transcriptional activity, we measured promoter activity using luciferase reporter constructs.

RESULTS

We found the frequencies of the CC, CG, and GG genotype of the rs2010963 polymorphism were 15.09%, 47.14%, and 37.74% in DR and 12.90%, 19.35%, and 67.74% in DNR, respectively (p = 0.0205). The prevalence of DR was higher (p = 0.00793) in patients with the CC or CG genotype (62.26% and 32.26% for DR and DNR, respectively) compared with the patients with the GG genotype. To evaluate the effect of rs2010963-C allele on transcriptional activity, we measured promoter activity using luciferase reporter constructs. The rs2010963-C reporter showed 1.6 to 2-fold higher luciferase activity than rs2010963-G in 3 cell lines.

CONCLUSION

Our data proposed rs2010963-C altered the expression level of VEGFA in different tissues. We suggested small increase but long term exposure to VEGFA may lead to DR finally.

Functional promoter polymorphisms of the receptor for advanced glycation end products in children and adolescents with type 1 diabetes

RAGE promoter polymorphisms are associated with increases in RAGE expression. A case-control association study was conducted involving a Euro-Brazilian population of children and adolescents with type 1 diabetes (n = 90) and healthy controls (n = 105), which were matched by sex and age. Genotyping by PCR-RFLP the -429T>C (rs1800625), -374T>A (rs1800624), and 63 bp deletion/insertion (-407 to -345 bp) showed no significant differences (P > 0.05) between the groups.

Emerging Targets for Therapeutic Development in Diabetes and Its Complications: The RAGE Signaling Pathway

Types 1 and 2 diabetes are on the rise worldwide. Although the treatment of hyperglycemia has benefited from recent advances, aggressive efforts to maintain euglycemia may be fraught with risk, especially in older subjects or in subjects vulnerable to hypoglycemic unawareness. Hence, strategies to prevent and treat the complications of hyperglycemia are essential. In this review we summarize recent updates on the biology of the receptor for advanced glycation endproducts (RAGE) in the pathogenesis of both micro- and macrovascular complications of diabetes, insights from the study of mouse models of obesity and diabetic complications, and from associative studies in human subjects. The study of the mechanisms and consequences of the interaction of the RAGE cytoplasmic domain with the formin, mDia1, in RAGE signal transduction, will be discussed. Lastly, we review the "state-of-the-art" on RAGE-directed therapeutics. Tackling RAGE/mDia1 may identify a novel class of therapeutics preventing diabetes and its complications.

Oxidative stress-related genes in type 2 diabetes: association analysis and their clinical impact

Worldwide prevalence of diabetes mellitus motivates a number of association studies to be conducted throughout the world. Eleven polymorphisms from nine candidate genes in oxidative stress pathway have been analyzed in eastern Indian type 2 diabetic patients (n = 145) and healthy controls (n = 100). Different biochemical parameters were also analyzed for their association with the disease. Significant associations were observed for rs2070424 A>G SOD1 (OR 3.91, 95% CI 2.265-8.142, P < 0.001), rs854573 A>G PON1 (OR 3.415, 95% CI 2.116-5.512, P < 0.001), rs6954345 G>C PON2 (OR 3.208, 95% CI 2.071-4.969, P < 0.001), RAGE rs1800624 -374 T>A (OR 3.58, 95% CI 2.218-5.766, P < 0.001), and NOS3 -786 T>C (OR 3.75, 95% CI 2.225-6.666, P < 0.001). Haplotype containing two risk alleles of PON1 and PON2 genes was significantly associated with disease (OR 8.34, 95% CI 1.554-44.804, P < 0.002). Our results suggest that carriers of major and efficient alleles of oxidative stress genes are more likely to survive the comorbid complications and single copy of risk allele is sufficient for developing the disease.

Human genetics of diabetic retinopathy

There is evidence demonstrating that genetic factors contribute to the risk of diabetic retinopathy (DR). Genetics variants, structural variants (copy number variation, CNV) and epigenetic changes play important roles in the development of DR. Genetic linkage and association studies have uncovered a number of genetic loci and common genetic variants susceptibility to DR. CNV and interactions of gene by environment have also been detected by association analysis. Apart from nucleus genome, mitochondrial DNA plays critical roles in regulation of development of DR. Epigenetic studies have indicated epigenetic changes in chromatin affecting gene transcription in response to environmental stimuli, which provided a large body of evidence of regulating development of diabetes mellitus. Identification of genetic variants and epigenetic changes contributed to risk or protection of DR will benefit uncovering the complex mechanism underlying DR. This review focused on the current knowledge of the genetic and epigenetic basis of DR.

Genetics of diabetic retinopathy

Multiple studies have shown that genetic factors may play an important role in determining an individual's risk for the development of diabetic retinopathy (DR) and progression to proliferative DR. However, consistent and definitive genetic associations with DR across broad populations have been not been established. Numerous genes have been studied for their association with DR and the results of these investigations have most specifically pointed to three specific genes that are likely involved in DR development and progression. The gene coding for vascular endothelial growth factor, aldose reductase, and the receptor for advanced glycation end products have been extensively evaluated, and specific polymorphisms of these genes have been suggested to potentially increase the risk of DR development. In this paper, we have reviewed the published literature on the genetics of DR and the potential implications for DR development and progression.

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.

Challenges in elucidating the genetics of diabetic retinopathy

IMPORTANCE

In the past decade, significant progress in genomic medicine and technologic developments has revolutionized our approach to common complex disorders in many areas of medicine, including ophthalmology. A disorder that still needs major genetic progress is diabetic retinopathy (DR), one of the leading causes of blindness in adults.

OBJECTIVE

To perform a literature review, present the current findings, and highlight some key challenges in DR genetics.

DESIGN, SETTING, AND PARTICIPANTS

We performed a thorough literature review of the genetic factors for DR, including heritability scores, twin studies, family studies, candidate gene studies, linkage studies, and genome-wide association studies (GWASs).

MAIN OUTCOME MEASURES

Environmental and genetic factors for DR.

RESULTS

Although there is clear demonstration of a genetic contribution in the development and progression of DR, the identification of susceptibility loci through candidate gene approaches, linkage studies, and GWASs is still in its infancy. The greatest obstacles remain a lack of power because of small sample size of available studies and a lack of phenotype standardization.

CONCLUSIONS AND RELEVANCE

The field of DR genetics is still in its infancy and is a challenge because of the complexity of the disease. This review outlines some strategies and lessons for future investigation to improve our understanding of this complex genetic disorder.

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.

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.

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.

A meta-analysis of receptor for advanced glycation end products gene: four well-evaluated polymorphisms with diabetes mellitus

Genetic association studies on the gene encoding receptor for advanced glycation end products (RAGE) and diabetes mellitus have reported conflicting results. To evaluate the association of RAGE gene four widely-evaluated polymorphisms (T-429C, T-374A, Gly82Ser and G1704T) and diabetes mellitus, a meta-analysis was conducted. A random-effects model was applied irrespective of between-study heterogeneity. There were a total of 5808/3742 (n=14) case-patients/controls (studies) for T-429C, 8259/6935 (n=19) for T-374A, 7029/5266 (n=19) for Gly82Ser, and 2843/3302 (n=13) for G1704T. Overall results detected no significant association of polymorphisms T-429C, T-374A and Gly82Ser with diabetes risk. There was a trend toward an increased risk for alleles 1704T relative to 1704G (odds ratio [OR]=1.09; 95% confidence interval [CI]: 0.98-1.22; I(2)=0). Subgroup analysis by ethnicity indicated that allele 1704T conferred a significantly increased risk in East Asians (OR=1.21; 95% CI: 1.04-1.4; I(2)=0) but not in Caucasians (OR=0.8; 95% CI: 0.6-1.07; I(2)=0), and that by type of diabetes mellitus indicated that association was potentiated exclusively for G1704T with diabetic retinopathy (OR=1.24; 95% CI: 1.01-1.51; I(2)=0). No publication bias was observed. Our results provide convincing evidence regarding the association of RAGE gene 1704T allele with an increased risk of diabetes mellitus, especially diabetic retinopathy. Notably, this effect was more pronounced in East Asians.

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

Conflicting results have been reported in different populations on the association between two particular RAGE gene polymorphisms (-429T/C and -374T/A) and retinopathy in diabetic patients. Therefore this study was designed to assess the association between both gene polymorphisms with retinopathy in Malaysian diabetic patients. A total of 342 type 2 diabetic patients [171 without retinopathy (DNR) and 171 with retinopathy (DR)] and 235 healthy controls were included in this study. Genomic DNA was obtained from blood samples and the screening for the gene polymorphisms was done using polymerase chain reaction-restriction fragment length polymorphism approach. Overall, the genotype distribution for both polymorphisms was not statistically different (p>0.05) among the control, DNR and DR groups. The -429C minor allele frequency of DR group (12.0%) was not significantly different (p>0.05) when compared to DNR group (16.1%) and healthy controls (11.3%). The -374A allele frequency also did not differ significantly between the control and DNR (p>0.05), control and DR (p>0.05) as well as DNR and DR groups (p>0.05). This is the first study report on RAGE gene polymorphism in Malaysian DR patients. In conclusion, -429T/C and -374T/A polymorphisms in the promoter region of RAGE gene were not associated with Malaysian type 2 DR patients.

Association of the receptor for advanced glycation end products gene polymorphisms with diabetic retinopathy in type 2 diabetes: a meta-analysis

AIMS

To investigate the association between diabetic retinopathy (DR) in type 2 diabetes mellitus and three polymorphisms of the receptor for advanced glycation end products (RAGE) gene, -429T/C, -374T/A and Gly82Ser.

METHODS

A literature search was conducted through PubMed and Web of Science (up to August 31, 2011). Pooled odds ratios (ORs) were estimated using fixed-effects (FE) and random-effects (RE) models in co-dominant, recessive and dominant models. A sensitivity analysis was performed by excluding invalid studies.

RESULTS

Six articles investigated the -429T/C polymorphism, 7 publications were associated with the -374T/A polymorphism and 5 studies were associated with Gly82Ser in DR. For the -429T/C variant, we found no significant difference between DR patients and those with diabetes without retinopathy. A significant association of allele A with DR was found in the recessive model for the -374T/A variant (RE OR = 0.64, 95% CI = 0.42-0.99, p = 0.05, p heterogeneity = 0.55). In the recessive and co-dominant models for the Gly82Ser polymorphism, the pooled ORs were positive in the fixed-effects model (FE OR = 2.89, 95% CI = 1.49-5.60, p = 0.002, p heterogeneity = 0.20; and FE OR = 3.45, 95% CI = 1.76-6.67, p = 0.0003, p heterogeneity = 0.07, respectively), but in the random-effects model the results were negative.

CONCLUSIONS

Our research confirmed an association between the RAGE -374T/A polymorphism and retinopathy in subjects with type 2 diabetes and the -374AA allele was found to be a protective factor for type 2 diabetes. Otherwise, the RAGE Gly82Ser polymorphism might be considered a significant risk for DR in Asian populations.

Diabetic retinopathy: Validation study of ALR2, RAGE, iNOS and TNFB gene variants in a south Indian cohort

PURPOSE

We previously reported the association of the Z-2 allele of the promoter dinucleotide repeat in the Aldose reductase (ALR2) gene, the (CCTTT)₁₅ allele in the promoter of inductible nitric oxide synthase (iNOS) gene, and the (GT)₁₃ promoter polymorphism in the tumor necrosis factor β (TNFB) gene with an increased risk for diabetic retinopathy (DR), and the Gly82Ser polymorphism in the receptor for advanced glycation end products (RAGE) gene and the (GT)₉ allele of the TNFB gene with low-risk for DR in a hospital-based self-reported type 2 diabetes mellitus (T2DM) patients. We have repeated the study in a population-based south Indian cohort to validate the same variations in these genes.

MATERIALS AND METHODS

Type 2 diabetic patients with and without retinopathy (DR+ and DR- respectively) were recruited. (CA)(n) repeat, Gly82Ser, (CCTTT)(n) repeat and (GT)(n) repeat in ALR2, RAGE, iNOS and TNFB genes respectively were genotyped and their frequencies were analyzed using the relevant statistical tests.

RESULTS

Different allelic associations were observed in the present study as compared to our previous reports. Z+2 allele of ALR2, 13-repeat genotype of iNOS, 15-repeat genotype of TNF-β, genes were associated with susceptibility to DR. Gly82Ser polymorphisms of the RAGE gene were not associated with DR in the present study.

CONCLUSION

The present data show a difference in the association of variations in ALR2, iNOS and TNFB genes with DR, when compared to our previous reports; this could be attributed to differences between the study populations of the past and present report.

The association between the -374T/A polymorphism of the receptor for advanced glycation endproducts gene and blood pressure and arterial stiffness is modified by glucose metabolism status: the Hoorn and CoDAM studies

OBJECTIVES

Receptor for advanced glycation endproducts (RAGE)-ligand interaction may lead to vascular complications. Genetic variation in RAGE has been shown to alter expression, activity of RAGE or both. We, therefore, investigated whether RAGE single-nucleotide polymorphisms (SNPs) and haplotypes were associated with vascular disease.

METHODS

Nine tag SNPs that cover the common RAGE gene variation were genotyped in 1291 individuals from two Dutch population-based cohort studies, aged 64.5 +/- 8.6 years, with normal glucose metabolism (44%), impaired glucose metabolism (23%) or type 2 diabetes mellitus (33%). We used multiple regression analyses to compare prevalent cardiovascular disease and markers of atherosclerosis, blood pressure and arterial stiffness across genotypes, and examine effect modification by glucose metabolism status.

RESULTS

In unstratified analyses, no consistent associations between RAGE SNPs and prevalent cardiovascular disease and markers of atherosclerosis were found. However, the AA genotype of SNP rs1800624 (-374T/A) was consistently associated with lower SBP [-5.0 mmHg (95% confidence interval -10.4 to 0.3)] and DBP [-4.2 (-7.2 to -1.3)], pulse pressure [-0.8 (-5.0 to 3.4)] as well as with less arterial stiffness [-0.56 SD (-1.04 to -0.09)] in individuals with normal glucose metabolism, but with higher SBP [6.2 (0.9-11.5)], DBP [2.1 (-0.7 to 5.0)] and pulse pressure [4.1 (-0.2 to 8.4)] in individuals with impaired glucose metabolism or type 2 diabetes mellitus (P for interaction <or=0.05 in all analyses). Similar results were found for a haplotype that includes the -374A allele.

CONCLUSION

In individuals with normal glucose metabolism, the -374A allele of the RAGE gene is protectively associated with blood pressure and arterial stiffness, whereas in individuals with impaired glucose metabolism or type 2 diabetes mellitus, it is adversely associated with these variables.

RAGE: a novel biological and genetic marker for vascular disease

RAGE [receptor for AGEs (advanced glycation end-products)] plays an important role in the development and progression of vascular disease. Studies in cultured cells and small animal models of disease have clearly demonstrated that RAGE is central to the pathogenesis of vascular disease of the macro- and micro-vessels in both the diabetic and non-diabetic state. Emerging results from human clinical studies have revealed that levels of circulating soluble RAGE in the plasma may reflect the presence and/or extent of vascular disease state. Additionally, genetic variants of the RAGE gene (AGER in HUGO nomenclature) have been associated with vascular disease risk. Combining RAGE circulating protein levels and the presence of particular RAGE polymorphisms may be a useful clinical tool for the prediction of individuals at risk for vascular disease. Therapeutic intervention targeted at the RAGE gene may therefore be a useful means of treating pathologies of the vasculature.

Genetic susceptibility of diabetic retinopathy

Diabetes continues to be a major source of -morbidity and mortality among working-age adults nationally and internationally. The microvascular complications of diabetes, including diabetic retinopathy, account for a major proportion of disease-associated morbidity and likely contribute to macrovascular complications. Although glycemic control contributes to -susceptibility for diabetic complications, some people with strict control develop these complications, whereas -others with poor control remain complication free. This suggests a genetic contribution to disease development. Although many genes and proteins of vascular growth have been studied in association with diabetic retinopathy, no definitive major predisposing genes or functional consequences of genetic variants have been identified for microvascular complications of the disease. In this article, we review the studies done on candidate genes.

Association between sorbitol dehydrogenase gene polymorphisms and type 2 diabetic retinopathy

Diabetic retinopathy (DR) may affect 98% of diabetic patients, but its aetiology is poorly understood. Besides glycaemic exposure, genetic factors likely contribute to the onset of DR. The polyol pathway, including aldose reductase and sorbitol dehydrogenase (SDH), can be activated under hyperglycaemic conditions. In our work we searched for an association between the C-1214G and G-888C polymorphisms of the SDH gene promoter and the occurrence and progression of type 2 DR. Two hundred and fifteen unrelated individuals with type 2 diabetes mellitus (T2DM) were divided into three groups: without DR, with non-proliferative diabetic retinopathy (NPDR) and with proliferative diabetic retinopathy (PDR). Genotypes of the C-1214G (rs2055858) and G-888C (rs3759890) polymorphisms of the SDH gene were determined with DNA from the peripheral blood lymphocytes of patients by restriction fragment length polymorphism and allele-specific PCR, respectively. The genotype distributions were contrasted by the chi(2) test and the significance of the polymorphism was assessed by multiple logistic regression producing odds ratios (ORs) and 95% confidence intervals (CIs). We found an association (OR 1.73, 95% CI 1.06-2.83) between NPDR and the G allele of the G-888C polymorphism. There was no association between NPDR and the other polymorphisms of the SDH gene. No differences were found in the distributions of these polymorphisms between patients with PDR and those with NPDR. A weak association (OR 2.0, 95% CI 1.29-3.07) was found between DR and the G allele of the G-888C polymorphism. Analysis of the combined genotypes (haplotypes) of both polymorphisms revealed associations between the C/G-C/G genotype and NPDR (OR 2.95, 95% CI 1.07-8.13) as well as DR in general (OR 2.91, 95% CI 1.15-7.36). The G-888C polymorphism of the SDH gene may be associated with the onset of DR rather than with its progression, and its effect may be strengthened by the interaction with the C-1214G polymorphism, but this association is rather weak and requires further study.