Monocyte chemoattractant protein-1 (MCP-1) gene polymorphism as a potential risk factor for diabetic retinopathy in Japanese patients with type 2 diabetes

Genetic associated complications of type 2 Diabetes Mellitus: a review

According to the International Diabetes Federation, the number of adults (age of 20-79) being diagnosed with Diabetes Mellitus (DM) have increased from 285 million in year 2009 to 463 million in year 2019 which comprises of 95% Type 2 DM patient (T2DM). Research have claimed that genetic predisposition could be one of the factors causing T2DM complications. In addition, T2DMcomplications cause an incremental risk to mortality. Therefore, this article aims to discuss some complications of T2DM in and their genetic association. The complications that are discussed in this article are diabetic nephropathy, diabetes induced cardiovascular disease, diabetic neuropathy, Diabetic Foot Ulcer (DFU) and Alzheimer's disease. According to the information obtained, genes associated with diabetic nephropathy (DN) are gene GABRR1 and ELMO1 that cause injury to glomerular. Replication of genes FRMD3, CARS and MYO16/IRS2 shown to have link with DN. The increase of gene THBS2, NGAL, PIP, TRAF6 polymorphism, ICAM-1 encoded for rs5498 polymorphism and C667T increase susceptibility towards DN in T2DM patient. Genes associated with cardiovascular diseases are Adiponectin gene (ACRP30) and Apolipoprotein E (APOE) polymorphism gene with ξ2 allele. Haptoglobin (Hp) 1-1 genotype and Mitochondria Superoxide Dismutase 2 (SOD2) plays a role in cardiovascular events. As for genes related to diabetic neuropathy, Janus Kinase (JAK), mutation of SCN9A and TRPA1 gene and destruction of miRNA contribute to pathogenesis of diabetic neuropathy among T2DM patients. Expression of cytokine IL-6, IL-10, miR-146a are found to cause diabetic neuropathy. Besides, A1a16Va1 gene polymorphism, an oxidative stress influence was found as one of the gene factors. Diabetic retinopathy (DR) is believed to have association with Monocyte Chemoattractant Protein-1 (MCP-1) and Insulin-like Growth Factor 1 (IGF1). Over-expression of gene ENPP1, IL-6 pro-inflammatory cytokine, ARHGAP22's protein rs3844492 polymorphism and TLR4 heterozygous genotype are contributing to significant pathophysiological process causing DR, while research found increases level of UCP1 gene protects retina cells from oxidative stress. Diabetic Foot Ulcer (DFU) is manifested by slowing in reepithelialisation of keratinocyte, persistence wound inflammation and healing impairment. Reepithelialisation disturbance was caused by E2F3 gene, reduction of Tacl gene encoded substance P causing persistence inflammation while expression of MMp-9 polymorphism contributes to healing impairment. A decrease in HIF-1a gene expression leads to increased risk of pathogenesis, while downregulation of TLR2 increases severity of wound in DFU patients. SNPs alleles has been shown to have significant association between the genetic dispositions of T2DM and Alzheimer's disease (AD). The progression of AD can be due to the change in DNA methylation of CLOCK gene, followed with worsening of AD by APOE4 gene due to dyslipidaemia condition in T2DM patients. Insulin resistance is also a factor that contributes to pathogenesis of AD.

The corepressors GPS2 and SMRT control enhancer and silencer remodeling via eRNA transcription during inflammatory activation of macrophages

While the role of transcription factors and coactivators in controlling enhancer activity and chromatin structure linked to gene expression is well established, the involvement of corepressors is not. Using inflammatory macrophage activation as a model, we investigate here a corepressor complex containing GPS2 and SMRT both genome-wide and at the Ccl2 locus, encoding the chemokine CCL2 (MCP-1). We report that corepressors co-occupy candidate enhancers along with the coactivators CBP (H3K27 acetylase) and MED1 (mediator) but act antagonistically by repressing eRNA transcription-coupled H3K27 acetylation. Genome editing, transcriptional interference, and cistrome analysis reveals that apparently related enhancer and silencer elements control Ccl2 transcription in opposite ways. 4C-seq indicates that corepressor depletion or inflammatory signaling functions mechanistically similarly to trigger enhancer activation. In ob/ob mice, adipose tissue macrophage-selective depletion of the Ccl2 enhancer-transcribed eRNA reduces metaflammation. Thus, the identified corepressor-eRNA-chemokine pathway operates in vivo and suggests therapeutic opportunities by targeting eRNAs in immuno-metabolic diseases.

Inflammatory Biomarkers Levels in T2DM Emirati Patients with Diabetic Neuropathy

INTRODUCTION

Previous studies have suggested the involvement of chronic low-grade inflammation in the pathogenesis of diabetic neuropathy (DNP). However, none of these studies have examined the levels of monocyte chemoattractant protein-1 (MCP-1) in type 2 diabetes mellitus (T2DM) patients with confirmed diagnosis of neuropathy. Therefore, the present study aims to investigate the levels of MCP-1 along with IL-6, IL-8 and TGF-β in patients with T2DM and confirmed neuropathy and identify correlations, if any, between MCP-1 and other parameters.

METHODS

A single center cross-sectional clinical study was conducted at University Hospital Sharjah (UHS) and University of Sharjah. One hundred and two patients with T2DM were recruited from diabetes clinics at UHS and were stratified into different groups based on diagnosis of DNP and other parameters. Several analyses were conducted to evaluate and compare the levels of MCP-1, IL-6, IL-8, and TGF-β across these groups of patients and identify correlations, if any, between MCP-1 and other variables.

RESULTS

A significant increase was found in the levels of MCP-1 in T2DM patients with DNP compared to the patients without DNP (p=0.002, p-adj=0.007). Further analysis has shown that levels of IL-8 (p=0.008) and TGF-β (p=0.06) were increased and decreased, respectively, in patients with DNP compared to patients without DNP. Moreover, strong correlations were found between MCP-1, IL-8 and TGF-β levels.

CONCLUSION

The key finding of the present study is the significant elevation in levels of MCP-1 in T2DM patients with DNP compared to the patients without DNP and IL-8 and TGF-β were strong predictors of MCP-1 increased levels.

Molecular and Pathophysiological Mechanisms of Diabetic Retinopathy in Relation to Adhesion Molecules

Diabetic Retinopathy (DR) is considered as a most common microvascular complication of diabetes affected by one in three people who are suffered for diabetes. Several pathophysiological mechanisms and adhesion molecules may play an etiologic role in the development of diabetes and its complications. The adhesion molecules located on both leucocytes and endothelial cells and considered as important molecules which can assessed the endothelial function. The functions of adhesion molecules involved in the cellular margination, slow rolling and transmigration of leukocytes. Hyperglycemia and its immediate biochemical sequelae or the low-grade inflammation directly alter endothelial function or influence endothelial cell functioning indirectly by induce oxidative stress and activates leukocytosis and leukocyte-endothelial cell interactions by the increased expression of adhesion molecules, growth factors, inflammatory factors, chemokines etc. and results DR. This review summarized the several pathophysiological mechanisms and role of adhesion molecules in disruption of homeostasis of vasculature by leukocytes in the development of diabetic retinopathy.

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.

Diabetic macular oedema: clinical risk factors and emerging genetic influences

Diabetic macular oedema is the major cause of visual impairment in type 1 and type 2 diabetes. As type 2 diabetes becomes more prevalent worldwide, the prevalence of diabetic macular oedema is also expected to rise. Current management of diabetic macular oedema is challenging, expensive and not optimal in a subset of patients. Therefore, it is important to increase our understanding of the risk factors involved and develop preventative strategies. While clinical risk factors for diabetic macular oedema have been identified, few studies have addressed potential genetic risk factors. Epidemiology and family studies suggest genetic influences are of importance. In this review, we summarise known clinical risk factors, as well as discuss the small number of genetic studies that have been performed for diabetic macular oedema.

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 monocyte chemoattractant protein-1 gene 2518A/G polymorphism with diabetic retinopathy in type 2 diabetes mellitus: A meta-analysis

AIMS

The relationship between monocyte chemoattractant protein-1 (MCP-1) 2518 A/G polymorphism and diabetic retinopathy (DR) attracted intense interest recently, but the reported results are controversial. A meta-analysis was performed to assess the MCP-1 polymorphism associated with DR susceptibility in type 2 diabetes mellitus.

METHODS

Eligible studies were identified from PubMed, Embase, Web of science, Chinese Biomedical database, and references of retrieved articles. Pooled odds ratios (ORs) with their 95% confidence intervals (95%CI) were calculated by fixed or random-effects models.

RESULTS

Six studies involving 3415 patients without DR and 3468 with any DR were included in the final meta-analysis. Each 5 studies evaluated the associations of MCP-1 polymorphism and any DR and proliferative DR (PDR), respectively. Meta-analysis in fixed model demonstrated a significant association between MCP-1 polymorphism and any DR under the homozygous model (OR=1.36; 95%CI: 1.15-1.62, P<0.001), heterozygous model (OR=1.20; 95%CI: 1.02-1.42, P=0.031), dominant model (OR=1.28; 95%CI: 1.10-1.50, P=0.002), recessive model (OR=1.17; 95%CI: 1.05-1.31, P=0.004), and allelic model (OR=1.16; 95%CI: 1.07-1.25, P<0.001). Furthermore, a significant association of MCP-1 polymorphism and DR progression from non-proliferative DR to proliferative DR was identified under heterozygous model (OR=1.45; 95%CI: 1.04-2.02, P=0.030). Sensitivity analyses did not draw different findings.

CONCLUSIONS

Meta-analysis of existing data suggested that MCP-1 2518 A/G polymorphism affected the risk of presence and progression of DR in type 2 diabetes mellitus.

The role of pharmacogenetics and advances in gene therapy in the treatment of diabetic retinopathy

Diabetic retinopathy (DR) and its complications such as diabetic macular edema continue to remain a major cause for legal blindness in the developed world. While the introduction of anti-tVEGF agents has significantly improved visual outcomes of patients with DR, unpredictable response, largely due to genetic polymorphisms, appears to be a challenge with this therapy. With advances in identification of various genetic biomarkers, novel therapeutic strategies consisting of gene transfer are being developed and tested for patients with DR. Application of pharmacogenetic principles appears to be a promising futuristic strategy to attenuate diabetes-mediated retinal vasculopathy. In this comprehensive review, data from recent studies in the field of pharmacogenomics for the treatment of DR have been provided.

Elevated serum monocyte chemoattractant protein-1 levels and its genetic polymorphism is associated with diabetic retinopathy in Chinese patients with Type 2 diabetes

AIM

Previous studies have reported that monocyte chemoattractant protein-1 (MCP-1) is involved in inflammatory and metabolic diseases. The purpose of this study is to investigate the role of MCP-1 in the pathogenesis of diabetic retinopathy (DR) in Han Chinese patients with Type 2 diabetes.

METHODS

Serum levels of MCP-1 protein in patients classified as diabetic without retinopathy (DWR) and DR, including NPDR and PDR, were assayed by enzyme-linked immunosorbent assay. Genomic DNA from 198 DWR patients, 176 NPDR patients and 143 PDR patients were genotyped by using a PCR restriction fragment length polymorphism (PCR-RFLP) assay.

RESULTS

MCP-1 serum levels were significantly higher in NPDR and PDR patients than in the DWR patients. The frequencies of the GG genotype and G allele of the single nucleotide polymorphism (SNP) were significantly increased in DR patients compared with DWR patients. Further subgroup analysis was performed to test whether there was an association between the PDR or NPDR and DWR groups. Significantly higher frequencies of the GG genotype and G allele were observed in PDR and NPDR patients compared with DWR patients. Furthermore, the 25 patients with PDR were divided into three groups according to the genotype of the tested SNP. The expression of the MCP-1 gene was higher in the GG genotype group compared with the other two groups.

CONCLUSIONS

The results suggested that the -2518 GG genotype and G allele of MCP-1 are associated with an increased risk of PDR in the Chinese Han population. This polymorphism may influence the expression of the MCP-1 gene, which may play an important role in the pathogenesis of DR.

The MCP-1 Gene A-2518G Polymorphism Confers an Increased Risk of Vascular Complications in Type 2 Diabetes Mellitus Patients

OBJECTIVE

We aimed to evaluate the correlation of the monocyte chemoattractant protein 1 (MCP-1) A-2518G polymorphism with type 2 diabetes mellitus (T2DM) and vascular complications in T2DM, to aid in understanding its role in pathogenesis.

METHODS

A total of 150 T2DM patients and 50 healthy controls (group A) were enrolled. The T2DM patients were divided into three groups based on the absence of complications (group B) presence of microvascular disease (group C) or macrovascular disease (group D). DNA of all enrolled subjects was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for the MCP-1 A-2518G polymorphism. Serum MCP-1 levels were measured by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Participants in group D had increased serum MCP-1 levels relative to group B, group C, and group A (all p<0.01). Compared with group A, the frequencies of the MCP-1 A-2518G G/G genotype and G allele were significantly higher in group C and group D (all p<0.05). In contrast to group B, group C had higher frequencies of the G/G genotype and G allele, while group D had higher G allele frequencies (all p<0.05). Logistic regression analysis showed that lower body-mass index (BMI) and free cholesterol (FC), as well as higher high-density lipoprotein cholesterol (HDL-C) levels may be the protective factors for T2DM, while higher levels of triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and G/G genotype frequency were independent risk factors for T2DM.

CONCLUSIONS

Our data indicates a correlation between the MCP-1 A-2518G polymorphism with macrovascular complications in T2DM patients; lower BMI and FC, as well as higher HDL-C levels may be the protective factors for T2DM, while higher levels of TG, LDL-C, and G/G genotype frequency were independent risk factors for T2DM.

Association between new onset diabetic retinopathy and monocyte chemoattractant protein-1 (MCP-1) polymorphism in Japanese type 2 diabetes

We longitudinally evaluated the association between monocyte chemoattractant protein-1 (MCP-1) A-2518G polymorphism and new onset of diabetic retinopathy in 758 type 2 diabetic patients. The new onset of retinopathy increased with the increase of the number of G alleles, even after adjustment for age, HbA1c levels, and duration of diabetes.

Diabetic retinopathy: variations in patient therapeutic outcomes and pharmacogenomics

Diabetes and its microvascular complications in patients poses a significant challenge and constitutes a major health problem. When it comes to manifestations in the eye, each case of diabetic retinopathy (DR) is unique, in terms of the phenotype, genotype, and, more importantly, the therapeutic response. It is therefore important to identify factors that distinguish one patient from another. Personalized therapy in DR is a new trend aimed at achieving maximum therapeutic response in patients by identifying genotypic and phenotypic factors that may result in less than optimal response to conventional therapy, and consequently, lead to poorer outcome. With advances in the identification of these genetic markers, such as gene polymorphisms and human leucocyte antigen associations, as well as development of drugs that can target their effects, the future of personalized medicine in DR is promising. In this comprehensive review, data from various studies have been analyzed to present what has been achieved in the field of pharmacogenomics thus far. An insight into future research is also provided.

Chemokine mediated monocyte trafficking into the retina: role of inflammation in alteration of the blood-retinal barrier in diabetic retinopathy

Inflammation in the diabetic retina is mediated by leukocyte adhesion to the retinal vasculature and alteration of the blood-retinal barrier (BRB). We investigated the role of chemokines in the alteration of the BRB in diabetes. Animals were made diabetic by streptozotocin injection and analyzed for gene expression and monocyte/macrophage infiltration. The expression of CCL2 (chemokine ligand 2) was significantly up-regulated in the retinas of rats with 4 and 8 weeks of diabetes and also in human retinal endothelial cells treated with high glucose and glucose flux. Additionally, diabetes or intraocular injection of recombinant CCL2 resulted in increased expression of the macrophage marker, F4/80. Cell culture impedance sensing studies showed that purified CCL2 was unable to alter the integrity of the human retinal endothelial cell barrier, whereas monocyte conditioned medium resulted in significant reduction in cell resistance, suggesting the relevance of CCL2 in early immune cell recruitment for subsequent barrier alterations. Further, using Cx3cr1-GFP mice, we found that intraocular injection of CCL2 increased retinal GFP⁺ monocyte/macrophage infiltration. When these mice were made diabetic, increased infiltration of monocytes/macrophages was also present in retinal tissues. Diabetes and CCL2 injection also induced activation of retinal microglia in these animals. Quantification by flow cytometry demonstrated a two-fold increase of CX3CR1⁺/CD11b⁺ (monocyte/macrophage and microglia) cells in retinas of wildtype diabetic animals in comparison to control non-diabetic ones. Using CCL2 knockout (Ccl2^−/−) mice, we show a significant reduction in retinal vascular leakage and monocyte infiltration following induction of diabetes indicating the importance of this chemokine in alteration of the BRB. Thus, CCL2 may be an important therapeutic target for the treatment of diabetic macular edema.

Targeting inflammation in diabetes: Newer therapeutic options

Inflammation has been recognised to both decrease beta cell insulin secretion and increase insulin resistance. Circulating cytokines can affect beta cell function directly leading to secretory dysfunction and increased apoptosis. These cytokines can also indirectly affect beta cell function by increasing adipocyte inflammation.The resulting glucotoxicity and lipotoxicity further enhance the inflammatory process resulting in a vicious cycle. Weight reduction and drugs such as metformin have been shown to decrease the levels of C-Reactive Protein by 31% and 13%, respectively. Pioglitazone, insulin and statins have anti-inflammatory effects. Interleukin 1 and tumor necrosis factor-α antagonists are in trials and NSAIDs such as salsalate have shown an improvement in insulin sensitivity. Inhibition of 12-lipo-oxygenase, histone de-acetylases, and activation of sirtuin-1 are upcoming molecular targets to reduce inflammation. These therapies have also been shown to decrease the conversion of pre-diabetes state to diabetes. Drugs like glicazide, troglitazone, N-acetylcysteine and selective COX-2 inhibitors have shown benefit in diabetic neuropathy by decreasing inflammatory markers. Retinopathy drugs are used to target vascular endothelial growth factor, angiopoietin-2, various proteinases and chemokines. Drugs targeting the proteinases and various chemokines are pentoxifylline, inhibitors of nuclear factor-kappa B and mammalian target of rapamycin and are in clinical trials for diabetic nephropathy. Commonly used drugs such as insulin, metformin, peroxisome proliferator-activated receptors, glucagon like peptide-1 agonists and dipeptidyl peptidase-4 inhibitors also decrease inflammation. Anti-inflammatory therapies represent a potential approach for the therapy of diabetes and its complications.

CNS inflammation and bone marrow neuropathy in type 1 diabetes

By using pseudorabies virus expressing green fluorescence protein, we found that efferent bone marrow-neural connections trace to sympathetic centers of the central nervous system in normal mice. However, this was markedly reduced in type 1 diabetes, suggesting a significant loss of bone marrow innervation. This loss of innervation was associated with a change in hematopoiesis toward generation of more monocytes and an altered diurnal release of monocytes in rodents and patients with type 1 diabetes. In the hypothalamus and granular insular cortex of mice with type 1 diabetes, bone marrow-derived microglia/macrophages were activated and found at a greater density than in controls. Infiltration of CD45(+)/CCR2(+)/GR-1(+)/Iba-1(+) bone marrow-derived monocytes into the hypothalamus could be mitigated by treatment with minocycline, an anti-inflammatory agent capable of crossing the blood-brain barrier. Our studies suggest that targeting central inflammation may facilitate management of microvascular complications.

Association of monocyte chemoattractant protein-1 (MCP-1)2518A/G polymorphism with proliferative diabetic retinopathy in northern Chinese type 2 diabetes

BACKGROUND

The pathogenesis of proliferative diabetic retinopathy (PDR) remains poorly understood. Recent studies have implicated that monocyte chemoattractant protein-1 (MCP-1) is associated with diabetic microvascular or macrovascular complications. However, the relationship between single nucleotide polymorphism(SNP)c.2518A/G -rs1024611 in the MCP-1 gene with diabetic retinopathy remains controversial. In the present study, we evaluated the association of SNP in the MCP-1 gene with diabetic retinopathy (DR) and diabetic macular edema (DME) in a Chinese population from Northern China with type 2 diabetes.

METHODS

We conducted a case-control study, which enrolled 1,043 subjects with type 2 diabetes (528 with DR, including 277PDR; 515 without DR), and SNP genotyping of c.2518A/G in the MCP-1 gene was performed using the polymerase chain reaction. Genomic DNA was isolated from 3 ml samples of whole blood using a modified conventional DNA extraction method. The genotype and allele frequencies of 2518A/G were studied by using an automated DNA sequencer (ABI PRISM 3730 DNA Sequencer).

RESULTS

The demographic and clinical characteristics did not differ among genotype subgroups. The MCP-1(-2518) GG genotype was significantly associated with DR susceptibility with OR of 1.481 (95 % CI, 1.019-2.153) (P = 0.046). There were no significant differences in the MCP-1(-2518) G allele frequencies in DR compared to non-diabetic retinopathy (DNR) (P > 0.05, OR = 0.841, 95 % CI, 0.705-1.002). The MCP-1(-2518) GG genotype was significantly associated with high-risk PDR susceptibility with OR of 2.656 (95 % CI, 1.222-5.775) (P = 0.014). The MCP-1(-2518) G allele was significantly increased in high-risk PDR patients (P = 0.020, OR = 1.481, 95 % CI, 1.070-2.051) compared with A allele. Genotype and allele frequencies of various DME of the DR patients were compared, but there were no significant associations established (P > 0.05).

CONCLUSIONS

It is likely that the MCP-1 c.2518G/G genotype is a susceptibility gene for DR in Chinese type 2 diabetic patients, especially the high-risk PDR. There is no association with DME and c.2518G/G.

Obesity and its metabolic complications: the role of adipokines and the relationship between obesity, inflammation, insulin resistance, dyslipidemia and nonalcoholic fatty liver disease

Accumulating evidence indicates that obesity is closely associated with an increased risk of metabolic diseases such as insulin resistance, type 2 diabetes, dyslipidemia and nonalcoholic fatty liver disease. Obesity results from an imbalance between food intake and energy expenditure, which leads to an excessive accumulation of adipose tissue. Adipose tissue is now recognized not only as a main site of storage of excess energy derived from food intake but also as an endocrine organ. The expansion of adipose tissue produces a number of bioactive substances, known as adipocytokines or adipokines, which trigger chronic low-grade inflammation and interact with a range of processes in many different organs. Although the precise mechanisms are still unclear, dysregulated production or secretion of these adipokines caused by excess adipose tissue and adipose tissue dysfunction can contribute to the development of obesity-related metabolic diseases. In this review, we focus on the role of several adipokines associated with obesity and the potential impact on obesity-related metabolic diseases. Multiple lines evidence provides valuable insights into the roles of adipokines in the development of obesity and its metabolic complications. Further research is still required to fully understand the mechanisms underlying the metabolic actions of a few newly identified adipokines.

Association of monocyte chemoattractant protein-1 (MCP-1) 2518A/G polymorphism with proliferative diabetic retinopathy in Korean type 2 diabetes

PURPOSE

Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that can increase adhesion molecule expression on monocytes and produce superoxide anions. Hyperglycemia induces MCP-1 production in vascular endothelial cells and retinal pigmented epithelial cells, and has been implicated as a causal factor in the facilitation of vascular complications in diabetes. In the present study, we evaluated the association of a single nucleotide polymorphism (SNP) in the MCP-1 gene with proliferative diabetic retinopathy (PDR) in a Korean population with type 2 diabetes.

MATERIALS AND METHODS

We conducted a case-control study, which enrolled 590 subjects with type 2 diabetes, and SNP genotyping of c.2518A/G in the MCP-1 gene was performed using polymerase chain reaction followed by digestion with PvuII restriction enzyme.

RESULTS

The prevalence of c.2518A/G polymorphism in diabetic patients was 13.2% (A/A), 47.1% (A/G) and 39.7% (G/G). In patients with diabetic retinopathy, the prevalence of PDR was significantly higher (p=0.009) in diabetic subjects with the c.2518A/A genotype (35.9%; n=78) compared to those with either the A/G or G/G genotype (22.3%, n=512). The prevalence of any other micro and macro-complications, including nephropathy and cerebrovascular events, were not different according to the c.2518A/G genotype.

CONCLUSION

Our new genetic findings suggest that the c.2518A/A genotype in MCP-1 could be used as a susceptibility gene to predispose Koreans exhibiting type 2 diabetes for the development of PDR.

Diabetic retinopathy and inflammation: novel therapeutic targets

Most anti-vascular endothelial growth factor (VEGF) therapies in diabetic macular edema are not as robust as in proliferative diabetic retinopathy. Although the VEGF appears to be a good target in diabetic macular edema, the anti-VEGF therapies appear to be of transient benefit as the edema recurs within a few weeks, and repeated injections are necessary. There is new evidence that indicates 'retinal inflammation' as an important player in the pathogenesis of diabetic retinopathy. There are common sets of inflammatory cytokines that are upregulated in both the serum and vitreous and aqueous samples, in subjects with diabetic retinopathy, and these cytokines can have multiple interactions to impact the pathogenesis of the disease. The key inflammatory events involved in the blood retinal barrier (BRB) alteration appear to be: (1) Increased expression of endothelial adhesion molecules such as ICAM1, VCAM1, PECAM-1, and P-selectin, (2) adhesion of leukocytes to the endothelium, (3) release of inflammatory chemokines, cytokines, and vascular permeability factors, (4) alteration of adherens and tight junctional proteins between the endothelial cells, and (5) infiltration of leukocytes into the neuro-retina, resulting in the alteration of the blood retinal barrier (diapedesis). VEGF inhibition itself may not achieve neutralization of other inflammatory molecules involved in the inflammatory cascade of the breakdown of the BRB. It is possible that the novel selective inhibitors of the inflammatory cascade (like angiopoietin-2, TNFα, and chemokines) may be useful therapeutic agents in the treatment of diabetic macular edema (DME), either alone or in combination with the anti-VEGF drugs.

Monocyte Chemoattractant Protein 1 (MCP-1) in obesity and diabetes

Monocyte Chemoattractant Protein-1 (MCP-1) is the first discovered and most extensively studied CC chemokine, and the amount of studies on its role in the etiologies of obesity- and diabetes-related diseases have increased exponentially during the past two decades. This review attempted to provide a panoramic perspective of the history, regulatory mechanisms, functions, and therapeutic strategies of this chemokine. The highlights of this review include the roles of MCP-1 in the development of obesity, diabetes, cardiovascular diseases, insulitis, diabetic nephropathy, and diabetic retinopathy. Therapies that specifically or non-specifically inhibit MCP-1 overproduction have been summarized.

Role of intravitreal inflammatory cytokines and angiogenic factors in proliferative diabetic retinopathy

OBJECTIVE

Inflammatory reaction has been shown to involve the progress of type 2 (non-insulin-dependent) diabetes. We, therefore, examined the effects of inflammatory cytokines and angiogenic factors in the pathogenesis of proliferative diabetic retinopathy (PDR) in type 2 diabetes.

PATIENTS AND METHODS

Vitreous fluid samples were obtained by vitrectomy from 62 eyes of PDR patients with type 2 diabetes and from 20 eyes of age-matched non-diabetic patients. The concentrations of interleukin 1 beta (IL1B), IL6, IL8, IL10, chemokine (C-C motif) ligand 2 (CCL2), endothelin 1 (EDN1), vascular endothelial growth factor (VEGF), and tumor necrosis factor (TNF) in the vitreous samples were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The concentrations of LI1B, IL6, IL8, CCL2, EDN1, VEGF, and TNF in the vitreous samples were considerably higher in PDR patients in comparison with the controls. However, the level of IL10 in PDR patients was similar to that obtained in the controls. Analysis of the correlations of the studied factors revealed the correlation of VEGF and IL6, VEGF and EDN1, IL8 and CCL2, and EDN1 and TNF in PDR patients. In addition, a significant positive correlation was observed between vitreous TNF as well as EDN1 and serum HbA(1)c levels in PDR patients.

CONCLUSIONS

The inflammatory cytokines and angiogenic factors IL1B, IL6, IL8, CCL2, EDN1, VEGF, and TNF are increased in the vitreous of PDR patients without an increase in IL-10. These results add support to the role of inflammatory cytokines and angiogenic factors in the genesis of PDR. Understanding the implication of these cytokines may provide diagnostic tools and therapeutic targets for treatment and prevention of PDR.

The -2518A/G polymorphism in the monocyte chemoattractant protein-1 (MCP-1) gene and diabetes risk: a meta-analysis

We conducted a meta-analysis to investigate the association between the -2518A/G polymorphism in the MCP-1 gene and the risk of diabetes. Ten case-control studies were included in this meta-analysis. Results indicated this polymorphism may be a risk factor for diabetes in Caucasians. Future studies are needed to validate our conclusions.