Association of intercellular adhesion molecule 1 polymorphisms with retinopathy in Chinese patients with Type 2 diabetes

Association between Aldose Reductase Gene C(-106)T Polymorphism and Diabetic Retinopathy: A Systematic Review and Meta-Analysis

Controversial results regarding the associations between aldose reductase (AR) genetic polymorphisms and diabetic retinopathy (DR) have been reported for many years. The present meta-analysis was performed to clarify the effects of the AR gene C(-106)T polymorphism on DR risk. The PubMed, Web of Sciences, Cochrane library, EMBASE, Chinese National Knowledge Infrastructure, and Wan Fang databases were extensively searched in Chinese to select relevant studies with an updated date of April 25, 2018. The Newcastle-Ottawa Scale (NOS) was applied to assess quality. The random-effects model was applied to calculate the pooled OR and 95% CI. This meta-analysis identified 23 studies with an average score of 7.52 for NOS analysis, including 4,313 DR cases and 5,128 diabetes mellitus (DM) control cases. In the overall analysis, a significant association between the AR gene C(-106)T polymorphism and DR susceptibility was found. In subgroups stratified by DM type and ethnicity, significantly increased risks for DR were found in DM type 1, East Asian populations, and Middle Eastern populations. Compared with DR control cases, the following associations were found: T vs. C: OR 0.91, 95% CI 0.85-0.97, I2 = 72.9%; CT + TT vs. CC: OR 0.75, 95% CI 0.68-0.81, I2 = 86.7%; and CT vs. CC: OR 0.86, 95% CI 0.78-0.94, I2 = 70.5%. The results of this meta-analysis showed a significant association between the AR gene C(-106)T polymorphism and susceptibility to DR in DM patients. DM patients with allele T and CT+TT genotype of the AR gene may have a lower risk of DR.

Association between diabetic retinopathy in type 2 diabetes and the ICAM-1 rs5498 polymorphism: a meta-analysis of case-control studies

Background

Genetic studies have reported contradictory results on the association between the intercellular adhesion molecule-1 (ICAM-1) rs5498 polymorphism and diabetic retinopathy (DR) risk in type 2 diabetic patients. We aimed to perform a systematic literature search and conduct random-effects meta-analysis to provide a quantitative evaluation.

Methods

We searched Pubmed, Embase, Scopus, Web of Science and Wanfang databases from inception up to January 2018. Allelic and genotype frequencies of rs5498 was compared between DR cases and controls. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using a random effects model.

Results

Nine studies involving a total of 1792 cases and 1400 controls met our inclusion criteria. We did not find any significant association between rs5498 and DR risk at the dominant model (GG + GA versus AA, OR = 1.00, 95% CI: 0.66–1.50, P = 0.987), the recessive model (GG versus GA + AA, OR = 1.24, 95% CI: 0.86–1.77, P = 0.245), the GG versus AA contrast (OR = 1.14, 95% CI: 0.68–1.92, P = 0.611), and the G allele versus A allele contrast (OR = 1.08, 95% CI: 0.81–1.45, P = 0.592). Subgroup analysis by ethnicity showed no association in Asian populations (G allele versus A allele: OR = 1.05, 95% CI: 0.76–1.44, P = 0.790). Subgroup analysis by DR subtype also did not reveal any association of rs5498 with proliferative DR (G allele versus A allele: OR = 1.34, 95% CI: 0.71–2.52, P = 0.364) and non-proliferative DR (G allele versus A allele: OR = 0.71, 95% CI: 0.43–1.17, P = 0.180).

Conclusion

Our meta-analyses provide no evidence of the association of rs5498 with DR in type 2 diabetic patients.

Electronic supplementary material

The online version of this article (10.1186/s12886-018-0961-5) contains supplementary material, which is available to authorized users.

Diabetic macular oedema: under-represented in the genetic analysis of diabetic retinopathy

Diabetic retinopathy, a complication of both type 1 and type 2 diabetes, is a complex disease and is one of the leading causes of blindness in adults worldwide. It can be divided into distinct subclasses, one of which is diabetic macular oedema. Diabetic macular oedema can occur at any time in diabetic retinopathy and is the most common cause of vision loss in patients with type 2 diabetes. The purpose of this review is to summarize the large number of genetic association studies that have been performed in cohorts of patients with type 2 diabetes and published in English-language journals up to February 2017. Many of these studies have produced positive associations with gene polymorphisms and diabetic retinopathy. However, this review highlights that within this large body of work, studies specifically addressing a genetic association with diabetic macular oedema, although present, are vastly under-represented. We also highlight that many of the studies have small patient numbers and that meta-analyses often inappropriately combine patient data sets. We conclude that there will continue to be conflicting results and no meaningful findings will be achieved if the historical approach of combining all diabetic retinopathy disease states within patient cohorts continues in future studies. This review also identifies several genes that would be interesting to analyse in large, well-defined cohorts of patients with diabetic macular oedema in future candidate gene association studies.

Serum ICAM-1 level and ICAM-1 gene 1462A>G (K469E) polimorphism on microalbuminuria in nondiabetic, nonhypertensive and normolipidemic obese patients: Genetical background of microalbuminuria in obesity

BACKGROUND

A growing body of evidence suggest that obese individuals are under risk of renal parenchymal disorders when compared to nonobese counterparts. Microalbuminuria is the early marker of renal involvement. Although most of obese patients carries multiple risk factors for microalbuminuria, some obese individuals without risk factor may progress to microalbuminuria. The present study was performed to examine the role of ICAM-1 gene 1462A>G (K469E) polymorphism on microalbuminuria in obese subjects without diabetes mellitus, hypertension, hiperlipidemia and older age.

METHODS

Ninety eight obese and 96 nonobese individuals without a comorbidity enrolled into the study. Serum ICAM-1 level was measured by enzyme linked immunoabsorbent assay (ELISA) method. ICAM-1 gene 1462A>G (K469E) polymorphism was examined by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR). Nepholometric method was used to examine urinary albumin loss, and microalbuminuria was measured by albumin to creatinine ratio.

RESULTS

Obese individuals had significantly higher microalbuminuria and proteinuria level compared to nonobese subjects (p: 0.043 and p: 0.011; respectively). GG genotype of ICAM-1 carriers have significantly higher microalbuminuria compared to individuals with AA or AG genotype carriers (p: 0.042). Serum ICAM-1 level was significantly correlated with creatinine and microalbuminuria (p: 0.002 and p: 0.03; respectively). Logistic regression analysis indicated a 7.39 fold increased risk of microalbuminuria in individuals with GG genotype of ICAM-1 gene 1462A>G (K469E) polymorphism.

CONCLUSIONS

GG genotype of ICAM-1 gene K469E polymorphism is associated with increased microalbuminuria in obese individuals without another metabolic risk factor.

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 ICAM-1 and HMGA1 Gene Variants with Retinopathy in Type 2 Diabetes Mellitus Among Chinese Individuals

PURPOSE

To evaluate the association of intercellular cell-adhesion molecule 1 (ICAM-1) and high-mobility group A1 (HMGA1) gene variants with diabetic retinopathy (DR) in a Chinese type 2 diabetes mellitus (T2DM) cohort.

METHODS

A total of 792 patients with T2DM were enrolled and categorized into two groups: (1) the DR group consisted of 448 patients, which was further subclassified into the proliferative DR (PDR) group with 220 patients and the nonproliferative DR (NPDR) group with 228 patients; (2) the diabetes without retinopathy (DNR) group comprised 344 patients who had no signs of DR. The single-nucleotide polymorphism (SNP) rs5498 in ICAM-1 gene and IVS5-13insC variant in HMGA1 gene were genotyped.

RESULTS

No evident association was found in the allele frequencies between SNP rs5498 in ICAM-1 gene and DR patients; the combined p values for the additive, dominant, and recessive models in genotype were greater than 0.05. No significant association was identified between the IVS5-13insC variant in HMGA1 gene and DR individuals.

CONCLUSIONS

Our results revealed that SNP rs5498 in ICAM-1 gene and IVS5-13insC variant in HMGA1 gene were not associated with the susceptibility of DR in the Chinese T2DM cohort.

Meta-analysis of association between K469E polymorphism of the ICAM-1 gene and retinopathy in type 2 diabetes

AIM

To collectively evaluate the association of intercellular adhesion molecule-1 (ICAM-1) gene K469E polymorphism (rs5498) with diabetic retinopathy (DR) in patients with type 2 diabetic mellitus (T2DM).

METHODS

Overall review of available literatures relating K469E polymorphism to the risk of DR was conducted on 4 electronic databases. Meta-analysis was performed by Stata 12.0 to calculate pooled odds ratios (ORs). Potential sources of heterogeneity and bias were explored.

RESULTS

Seven studies with genotype frequency data including 1120 cases with DR and 956 diabetic controls free of DR were included. Meta-analysis did not show significant association of K469E polymorphism with DR (P>0.05). A statistically significant association was detected between the K469E polymorphism and proliferative diabetic retinopathy (PDR) in Asians only in dominant model (GG+AG vs AA) with pooled OR of 0.729 (95%CI: 0.564-0.942, P=0.016, P heterogeneity=0.143), however, this association was not detected in recessive model (GA+AA vs GG; OR=1.178, 95%CI: 0.898-1.545, P=0.236, P heterogeneity=0.248) or allelic model (G vs A; OR=0.769, 95% CI: 0.576-1.026, P=0.074, P heterogeneity=0.094). No publication bias was found by Funnel plot, Begg's and Egger's test.

CONCLUSION

This research found no statistically significant association between ICAM-1 gene K469E polymorphism and DR in patients with T2DM, but showed significant association of the K469E polymorphism with PDR in Asian diabetic patients only in dominant model. Further investigation would be required to consolidate the conclusion.

High prevalence of diabetic retinopathy and lack of association with integrin α2 gene polymorphisms in patients with type 2 diabetes from Northeastern Mexico

Diabetic retinopathy (DR) is one of the primary causes of blindness in the working age population and is characterized by angiogenesis in the retina. Platelets have been suggested to be involved in the pathogenesis of diabetic microvascular complications. The integrin receptor for collagen/laminin, α2β1, mediates platelet primary adhesion to subendothelial tissues, which is an essential first step in thrombus formation. The gene encoding the α2 subunit of α2β1 integrin has ≥8 polymorphisms, including a BglII/NdeI restriction fragment length polymorphism. To explore the prevalence of DR in a population from Northeastern Mexico, unrelated, hospitalized patients who had received a diagnosis of type 2 diabetes mellitus (DM2) at least 10 years previously were recruited (n=177). DR was diagnosed in a masked manner by independent ophthalmologists using fundus images captured using a non-mydriatic retinal camera. A total of 121 patients with DM2 (68%) had some degree of DR development (DR patients), and 56 patients with DM2 (32%) did not exhibit any sign of DR (No-DR patients). The results showed that after 15 years of DM2 progression, there is an increased risk of DR (P=0.0497; odds ratio, 1.993). In addition, insulin therapy and family history of DM2 were significantly associated with DR. In order to detect a possible association between DR and BglII/NdeI α2 gene polymorphisms, a comparative cross-sectional study between DR and No-DR patients was conducted. The α2 gene was genotyped by polymerase chain reaction-restriction fragment length polymorphism assay. Statistical analysis revealed no association between BglII/NdeI genotypes and the development of DR in this group of patients. In conclusion, the present data indicate a high prevalence of DR in the Mexican population and suggest that the damage in DR is due to other factors, such as the duration of the DM2, and is not linked to BglII/NdeI α2 gene polymorphisms.

Association between the ICAM-1 K469E polymorphism and diabetic retinopathy in Type 2 diabetes mellitus: a meta-analysis

A meta-analysis was conducted to evaluate the association of ICAM-1 K469E gene polymorphism with diabetic retinopathy susceptibility in Type 2 diabetes mellitus. Seven studies involving 1094 cases and 909 controls were included. Current studies suggest that K469E polymorphism in ICAM-1 gene might not affect individual susceptibility to DR.

Candidate genes for proliferative diabetic retinopathy

Several candidate genes have been so far implicated in the pathogenesis of proliferative diabetic retinopathy (PDR) in subjects with type 2 diabetes. Since the principal pathogenetic mechanisms for diabetic retinopathy (DR) and PDR are different, the main pathogenetic mechanism in DR is increased vascular permeability, whereas in PDR the crucial pathogenetic mechanisms are fibrosis and neoangiogenesis. Due to that fact, different candidate genes are expected to be involved in the development of either DR or PDR. None of the candidate genes, however, can be fully and solely responsible for the development of PDR and for DR progression into PDR. Epigenetic mechanisms are expected to be involved in the pathogenesis of PDR as well. Gene polymorphisms responsible for PDR and epigenetic mechanisms responsible for PDR are reviewed in this paper.

Intracellular adhesion molecule-1 K469E gene polymorphism and risk of diabetic microvascular complications: a meta-analysis

BACKGROUND

A number of studies evaluated the association of intracellular adhesion molecule-1 (ICAM-1) K469E (rs5498, A/G) gene polymorphism with diabetic microvascular complications (DMI) including diabetic nephropathy (DN) and diabetic retinopathy (DR) in different populations. However, the results of individual studies remain conflicting.

METHODS

A comprehensive search was conducted to identify all eligible studies of the above-mentioned associations. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were assessed using the fixed or random effect model.

RESULTS

Seven studies involving 3411 subjects were included. Overall, the meta-analysis showed a significant association of the A allele with increased risk of DMI susceptibility in a recessive model (OR = 1.37, 95% CI 1.04-1.80, P = 0.02). In the subgroup analysis stratified by ethnicity, significant association was found in Asians but not in Caucasians (OR = 1.78, 95% CI 1.13-2.81, P = 0.01; OR = 1.10, 95% CI 0.79-1.54, P = 0.58, respectively). Moreover, it showed a significant association between the A allele and risk of DN in a recessive model (OR = 1.25, 95% CI 1.02-1.55, P = 0.04).

CONCLUSIONS

This meta-analysis suggested that the K469E polymorphism in ICAM-1 gene might affect individual susceptibility to DMI and showed a discrepancy in different ethnicities. Further investigations are needed to validate the association.

ICAM-1 K469E polymorphism is a genetic determinant for the clinical risk factors of T2D subjects with retinopathy in Indians: a population-based case-control study

OBJECTIVE

Elevated levels of intercellular adhesion molecule-1 (ICAM-1) are demonstrated in diabetes complications. The current study aims to understand association of K469E (rs5498) in ICAM-1 gene, in type 2 diabetic (T2D) subjects with retinopathy.

DESIGN

Case-control study.

SETTING

Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetic Study, an epidemiology study (on prevalence of diabetic retinopathy in T2D subjects (T2DR) from south India) and outpatient department of Sankara Nethralaya, a tertiary care hospital, in Chennai, India.

PARTICIPANTS

A total of 356 T2D subjects of >15 years of diabetes duration, with (n=199) and without (n=157) retinopathy.

METHODS

The rs5498 polymorphism was genotyped by direct sequencing. Multivariate analysis for various clinical covariates was done using SPSS V.14. Comparative assessment of structure stability, folding rate of the variants were assessed using bioinformatics tools like STRIDE, MuPro, ModellerV97, fold rate server, etc.

RESULTS

The AA genotype of rs5498 was seen at a higher frequency in the retinopathy group (p=0.012). The risk for diabetic retinopathy (DR) increased in the presence of AA genotype (OR=1.89-4.82) after the sequential addition of various clinical covariates. Multivariate logistic regression analysis showed 8.26 times high risk for developing DR in the AG genotype (p=0.003). Structural superimposition of ICAM-1 wild type (K469) and variant (E469) showed 0.943 Å of backbone root mean square deviation as calculated by PYMOL software. A difference in the fold rate time was also observed between the wild type (5.4/s) and variant (3.3/s).

CONCLUSIONS

This study shows that allele A of rs5498 in ICAM-1 is a putative risk predisposing allele for T2D retinopathy and its clinical covariates in Indian population. The folding rate of the protein decreases for the A allele implicating a potential effect on the structure and function of ICAM-1.

Association of intercellular adhesion molecule 1 (ICAM1) with diabetes and diabetic nephropathy

Diabetes and diabetic nephropathy are complex diseases affected by genetic and environmental factors. Identification of the susceptibility genes and investigation of their roles may provide useful information for better understanding of the pathogenesis and for developing novel therapeutic approaches. Intercellular adhesion molecule 1 (ICAM1) is a cell surface glycoprotein expressed on endothelial cells and leukocytes in the immune system. The ICAM1 gene is located on chromosome 19p13 within the linkage region of diabetes. In the recent years, accumulating reports have implicated that genetic polymorphisms in the ICAM1 gene are associated with diabetes and diabetic nephropathy. Serum ICAM1 levels in diabetes patients and the icam1 gene expression in kidney tissues of diabetic animals are increased compared to the controls. Therefore, ICAM1 may play a role in the development of diabetes and diabetic nephropathy. In this review, we present genomic structure, variation, and regulation of the ICAM1 gene, summarized genetic and biological studies of this gene in diabetes and diabetic nephropathy and discussed about the potential application using ICAM1 as a biomarker and target for prediction and treatment of diabetes and diabetic nephropathy.

Genome-wide association study of diabetic retinopathy in a Taiwanese population

PURPOSE

Diabetic retinopathy (DR) is a microvascular complication of diabetes with a complex multifactorial pathogenesis. The aim of this study was to identify the susceptibility genes that increase the risk of DR in type 2 diabetes (T2D) and to further elucidate the underlying mechanism of DR pathogenesis.

DESIGN

A case-control study.

PARTICIPANTS

We included 749 unrelated individuals with T2D (174 with DR and 575 without DR) and 100 nondiabetic controls.

METHODS

We conducted a genome-wide association study using Illumina HumanHap550-Duo BeadChips.

MAIN OUTCOME MEASURES

Compared with the genotypic distribution of single nucleotide polymorphisms (SNPs) between subjects with DR and without DR.

RESULTS

Using statistical models, we selected a total of 12 SNPs with P-values <1 × 10(-6) that were associated with DR. After controlling for diabetes duration and hemoglobin A(1C), 9 of the 12 SNPs located on 5 chromosomal regions were found to be associated with DR. Five loci not previously associated with DR susceptibility were identified in and around the following genes: MYSM1 (Myb-like, SWIRM, and MPN domains 1) located on chromosome 1p (odds ratio [OR], 1.50; 95% confidence interval [CI], 1.03-2.20); PLXDC2 (plexin domain-containing 2) located on the chromosome 10p (OR, 1.67; 95% CI, 1.06-2.65); ARHGAP22 (Rho GTPase-activating protein 22) located on chromosome 10q (OR, 1.65; 95% CI, 1.05-2.60); and HS6ST3 (heparan sulfate 6-O-sulfotransferase 3) located on chromosome 13q (OR, 2.33; 95% CI, 1.13-4.77). The SNPs rs13163610 and rs17376456 located in the unknown gene on chromosome 5q were also associated with DR (OR, 3.63; 95% CI, 1.38-9.58).

CONCLUSIONS

We identified a genetic association for susceptibility to DR in 5 novel chromosomal regions and PLXDC2 and ARHGAP22, the latter 2 of which are genes implicated in endothelial cell angiogenesis and increased capillary permeability. These findings suggest unsuspected pathways in the pathogenesis of DR.

Association analysis of nine candidate gene polymorphisms in Indian patients with type 2 diabetic retinopathy

Background

Diabetic retinopathy (DR) is classically defined as a microvasculopathy that primarily affects the small blood vessels of the inner retina as a complication of diabetes mellitus (DM).It is a multifactorial disease with a strong genetic component. The aim of this study is to investigate the association of a set of nine candidate genes with the development of diabetic retinopathy in a South Indian cohort who have type 2 diabetes mellitus (T2DM).

Methods

Seven candidate genes (RAGE, PEDF, AKR1B1, EPO, HTRA1, ICAM and HFE) were chosen based on reported association with DR in the literature. Two more, CFH and ARMS2, were chosen based on their roles in biological pathways previously implicated in DR. Fourteen single nucleotide polymorphisms (SNPs) and one dinucleotide repeat polymorphism, previously reported to show association with DR or other related diseases, were genotyped in 345 DR and 356 diabetic patients without retinopathy (DNR). The genes which showed positive association in this screening set were tested further in additional sets of 100 DR and 90 DNR additional patients from the Aravind Eye Hospital. Those which showed association in the secondary screen were subjected to a combined analysis with the 100 DR and 100 DNR subjects previously recruited and genotyped through the Sankara Nethralaya Hospital, India. Genotypes were evaluated using a combination of direct sequencing, TaqMan SNP genotyping, RFLP analysis, and SNaPshot PCR assays. Chi-square and Fisher exact tests were used to analyze the genotype and allele frequencies.

Results

Among the nine loci (15 polymorphisms) screened, SNP rs2070600 (G82S) in the RAGE gene, showed significant association with DR (allelic P = 0.016, dominant model P = 0.012), compared to DNR. SNP rs2070600 further showed significant association with DR in the confirmation cohort (P = 0.035, dominant model P = 0.032). Combining the two cohorts gave an allelic P < 0.003 and dominant P = 0.0013). Combined analysis with the Sankara Nethralaya cohort gave an allelic P = 0.0003 and dominant P = 0.00011 with an OR = 0.49 (0.34 - 0.70) for the minor allele. In HTRA1, rs11200638 (G>A), showed marginal significance with DR (P = 0.055) while rs10490924 in LOC387715 gave a P = 0.07. No statistical significance was observed for SNPs in the other 7 genes studied.

Conclusions

This study confirms significant association of one polymorphism only (rs2070600 in RAGE) with DR in an Indian population which had T2DM.

K469E polymorphism of the intracellular adhesion molecule 1 gene is associated with proliferative diabetic retinopathy in Caucasians with type 2 diabetes

BACKGROUND

In proliferative diabetic retinopathy (PDR) increased levels of cytokines, inflammatory cells and angiogenic factors are present.These factors increase the expression of cellular adhesion molecules (CAMs)The objective of this study was to investigate the association between the polymorphisms of the ICAM-1 gene (K469E, G241A) and the development of PDR among patients with type 2 diabetes in the Slovenian population (Caucasians).

METHODS

For the purpose, 195 subjects with type 2 diabetes with PDR were compared with 143 subjects with type 2 diabetes of duration of more than 10 years who had no clinical signs of diabetic retinopathy. We analysed serum ICAM levels in 54 subjects with type 2 diabetes and 25 subjects without diabetes.

RESULTS

A significantly higher frequency of the EE genotype of the K469E polymorphism of the ICAM-1 was found in the patients with PDR compared with those without diabetic retinopathy (OR = 2.0, 95% confidence interval [CI] = 1.1-3.5; P = 0.013), whereas the G241A polymorphism of the ICAM-1 gene failed to yield an association with PDR. Moreover, significantly higher sICAM-1 serum levels were demonstrated in diabetics with the EE genotype compared with those with the other (EK + KK) genotypes (918 +/-104 vs. 664 +/-209 microg/L; P = 0.001). The G241A polymorphism of the ICAM-1 gene, on the hand, failed to affect sICAM-1 serum levels in diabetics.

CONCLUSIONS

We may conclude that the EE genotype of the K469E polymorphism of the ICAM-1 might be a risk factor for PDR in the Slovenian population (Caucasians) with type 2 diabetes.

No association found between the promoter variants of TNF-alpha and diabetic retinopathy in Chinese patients with type 2 diabetes

PURPOSE

Necrosis tumor factor (TNF) is known to be associated with diabetic retinopathy (DR). The objective of this study was to examine the genetic variations of TNF-alpha and assess their possible relationship to DR in type 2 diabetic patients in the Chinese population.

MATERIALS AND METHODS

We conducted a case-control association study between the promoter variants of TNF-alpha and diabetic retinopathy in Chinese patients with type 2 diabetes. We selected three variants in the promoter region of TNF-alpha, namely rs1800629, rs1041981, and rs2857713.

RESULTS

No individual SNP nor any haplotype was found to be associated with DR in our study.

CONCLUSION

This is the first study to report TNF-alpha polymorphisms in patients with DR in the Chinese population. The results suggest that the variants among the promoter of TNF-alpha are unlikely to play a major role in the susceptibility to DR in Chinese patients with type 2 diabetes.

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.

Targeting the retinal microcirculation to treat diabetic sight problems

Diabetic retinopathy is a secondary complication of hyperglycemia caused by diabetes mellitus. The damage to the retina can ultimately cause vision loss as a result of increased capillary permeability and angiogenesis. Recent progress in the understanding of the mediators that drive angiogenesis, as well as the phenotypes of cells that are involved in this process, has provided a multitude of targets for pharmacologic intervention. This review presents the inhibitors of the biochemical processes that are at the root of diabetic retinopathy (i.e., non-enzymatic glycosylation of biomolecules, oxidative stress, activation of aldose reductase and activation of protein kinase C by formation of diacylglycerol) in addition to the inhibitors of the mechanical damage (i.e., increased vascular permeability, capillary occlusion and neovascularization).