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

Effect of metformin and insulin combination on monocyte chemoattractant protein-1 and cathepsin-D in type 2 diabetes mellitus

BACKGROUND AND AIMS

Monocyte chemoattractant protein-1 (MCP-1) and cathepsin-D are progressively raised in type 2 diabetes mellitus (T2DM) with both non proliferative and proliferative retinal disease. This study aimed to evaluate the effect of antidiabetic medications on MCP-1 and cathepsin-D.

METHODS

60 patients of T2DM without retinopathy and 60 of diabetic retinopathy were enrolled to receive metformin (500 mg-1000 mg) combined with either glimepiride (1 mg-2 mg) or insulin. The effect of antidiabetic medications on serum MCP-1 and cathepsin-D was assessed.

RESULTS

Mean MCP-1 (pg/ml) and cathepsin-D (ng/ml) levels were significantly lower in patients of T2DM with and without retinopathy treated with metformin + insulin (468.52 ± 272.84 vs 234.30 ± 180.58; p < 0.01 and 460.15 ± 128.52 vs 517.33 ± 213.49; p = 0.214) as compared to patients treated with metformin + glimepiride (1434.02 ± 105.27 vs 1256.27 ± 76.76; p < 0.01 and 1689.36 ± 752.57 vs 919.69 ± 675.05; p = < 0.01). No significant correlation of MCP-1 and cathepsin-D with HbA1c, fasting and post prandial blood glucose were found.

CONCLUSION

Patients treated with metformin and insulin combination had lower serum MCP-1 and cathepsin-D levels which suggests that this combination may be more effective in reducing the progression of diabetic retinopathy. (CTRI/2018/05/013601).

Chemokines and their receptors promoting the recruitment of myeloid-derived suppressor cells into the tumor

Myeloid-derived suppressor cells (MDSCs) expand in tumor-bearing host. They suppress anti-tumor immune response and promote tumor growth. Chemokines play a vital role in recruiting MDSCs into tumor tissue. They can also induce the generation of MDSCs in the bone marrow, maintain their suppressive activity, and promote their proliferation and differentiation. Here, we review CCL2/CCL12-CCR2, CCL3/4/5-CCR5, CCL15-CCR1, CX3CL1/CCL26-CX3CR1, CXCL5/2/1-CXCR2, CXCL8-CXCR1/2, CCL21-CCR7, CXCL13-CXCR5 signaling pathways, their role in MDSCs recruitment to tumor tissue, and their correlation with tumor development, metastasis and prognosis. Targeting chemokines and their receptors may serve as a promising strategy in immunotherapy, especially combined with other strategies such as chemotherapy, cyclin-dependent kinase or immune checkpoints inhibitors.

Identification of core genes and pathways in type 2 diabetes mellitus by bioinformatics analysis

Type 2 diabetes mellitus (T2DM) is a metabolic disorder. Numerous proteins have been identified that are associated with the occurrence and development of T2DM. This study aimed to identify potential core genes and pathways involved in T2DM, through exhaustive bioinformatic analyses using GSE20966 microarray profiles of pancreatic β-cells obtained from healthy controls and patients with T2DM. The original microarray data were downloaded from the Gene Expression Omnibus database. Data were processed by the limma package in R software and the differentially expressed genes (DEGs) were identified. Gene Ontology functional analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis were carried out to identify potential biological functions and pathways of the DEGs. Key transcription factors were identified using the WEB-based GEne SeT AnaLysis Toolkit (WebGestalt) and Enrichr. The Search Tool for the Retrieval of Interacting Genes (STRING) database was used to establish a protein-protein interaction (PPI) network for the DEGs. In total, 329 DEGs were involved in T2DM, with 208 upregulated genes enriched in pancreatic secretion and the complement and coagulation cascades, and 121 downregulated genes enriched in insulin secretion, carbohydrate digestion and absorption, and the Toll-like receptor pathway. Furthermore, hepatocyte nuclear factor 1-alpha (HNF1A), signal transducer and activator of transcription 3 (STAT3) and glucocorticoid receptor (GR) were key transcription factors in T2DM. Twenty important nodes were detected in the PPI network. Finally, two core genes, serpin family G member 1 (SERPING1) and alanyl aminopeptidase, membrane (ANPEP), were shown to be associated with the development of T2DM. On the whole, the findings of this study enhance our understanding of the potential molecular mechanisms of T2DM and provide potential targets for further research.

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.

Association of increased levels of MCP-1 and cathepsin-D in young onset type 2 diabetes patients (T2DM-Y) with severity of diabetic retinopathy

AIM

Young onset type 2 diabetes patients (T2DM-Y) have been shown to possess an increased risk of developing microvascular complications particularly diabetic retinopathy. However, the molecular mechanisms are not clearly understood. In this study, we investigated the serum levels of monocyte chemotactic protein 1 (MCP-1) and cathepsin-D in patients with T2DM-Y without and with diabetic retinopathy.

METHODS

In this case-control study, participants comprised individuals with normal glucose tolerance (NGT=40), patients with type 2 diabetes mellitus (T2DM=35), non-proliferative diabetic retinopathy (NPDR=35) and proliferative diabetic retinopathy (PDR=35). Clinical characterization of the study subjects was done by standard procedures and MCP-1 and cathepsin-D were measured by ELISA.

RESULTS

Compared to control individuals, patients with T2DM-Y, NPDR and PDR exhibited significantly (p<0.001) higher levels of MCP-1. Cathepsin-D levels were also significantly (p<0.001) higher in patients with T2DM-Y without and with diabetic retinopathy. Correlation analysis revealed a positive association (p<0.001) between MCP-1 and cathepsin-D levels. There was also a significant negative correlation of MCP1/cathepsin-D with C-peptide levels. The association of increased levels of MCP-1/cathepsin-D in patients with DR persisted even after adjusting for all the confounding factors.

CONCLUSION

As both MCP-1 and cathepsin-D are molecular signatures of cellular senescence, we suggest that these biomarkers might be useful to predict the development of retinopathy in T2DM-Y patients.

Gene therapy for diabetic retinopathy: Are we ready to make the leap from bench to bedside?

Diabetic retinopathy (DR), a chronic and progressive complication of diabetes mellitus, is a sight-threatening disease characterized in the early stages by neuronal and vascular dysfunction in the retina, and later by neovascularization that further damages vision. A major contributor to the pathology is excess production of vascular endothelial growth factor (VEGF), a growth factor that induces formation of new blood vessels and increases permeability of existing vessels. Despite the recent availability of effective treatments for the disease, including laser photocoagulation and therapeutic VEGF antibodies, DR remains a significant cause of vision loss worldwide. Existing anti-VEGF agents, though generally effective, are limited by their short therapeutic half-lives, necessitating frequent intravitreal injections and the risk of attendant adverse events. Management of DR with gene therapies has been proposed for several years, and pre-clinical studies have yielded enticing findings. Gene therapy holds several advantages over conventional treatments for DR, such as a longer duration of therapeutic effect, simpler administration, the ability to intervene at an earlier stage of the disease, and potentially fewer side-effects. In this review, we summarize the current understanding of the pathophysiology of DR and provide an overview of research into DR gene therapies. We also examine current barriers to the clinical application of gene therapy for DR and evaluate future prospects for this approach.

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.

Update on genetics and diabetic retinopathy

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