Circulating microRNA Biomarkers of Diabetic Retinopathy

Multi-omics reveal disturbance of glucose homeostasis in pregnant rats exposed to short-chain perfluorobutanesulfonic acid

Perfluorobutanesulfonic acid (PFBS), a short-chain alternative to perfluorooctanesulfonic acid (PFOS), is widely used in various products and is increasingly present in environmental media and human bodies. Recent epidemiological findings have raised concerns about its potential adverse health effects, although the specific toxic mechanism remains unclear. This study aimed to investigate the metabolic toxicity of gestational PFBS exposure in maternal rats. Pregnant Sprague Dawley (SD) rats were randomly assigned to three groups and administered either 3% starch gel (control), 5, or 50 mg/kg bw·d PFBS. Oral glucose tolerance tests (OGTT) and lipid profiles were measured, and integrated omics analysis (transcriptomics and non-targeted metabolomics) was employed to identify changes in genes and metabolites and their relationships with metabolic phenotypes. The results revealed that rats exposed to 50 mg/kg bw·d PFBS exhibited a significant decrease in 1-h glucose levels and the area under the curve (AUC) of OGTT compared with the starch group. Transcriptomics analysis indicated significant alterations in gene expression related to cytochrome P450 exogenous metabolism, glutathione metabolism, bile acid secretion, tumor pathways, and retinol metabolism. Differentially expressed metabolites (DEMs) were enriched in pathways such as pyruvate metabolism, the glucagon signaling pathway, central carbon metabolism in cancer, and the citric acid cycle. Co-enrichment analysis and pairwise correlation analysis among genes, metabolites, and outcomes identified several differentially expressed genes (DEGs), including Gstm1, Kit, Adcy1, Gck, Ppp1r3c, Ppp1r3d, and DEMs such as fumaric acid, L-lactic acid, 4-hydroxynonenal, and acetylvalerenolic acid. These DEGs and DEMs may play a role in the modulation of glucolipid metabolic pathways. In conclusion, our results suggest that gestational exposure to PFBS may induce molecular perturbations in glucose homeostasis. These findings provide insights into the potential mechanisms contributing to the heightened risk of abnormal glucose tolerance associated with PFBS exposure.

The link between glycemic control measures and eye microvascular complications in a clinical cohort of type 2 diabetes with microRNA-223-3p signature

BACKGROUND

Type 2 diabetes (T2D) is a critical healthcare challenge and priority in Qatar which is listed amongst the top 10 countries in the world, with its prevalence presently at 17% double the global average. MicroRNAs (miRNAs) are implicated in the pathogenesis of (T2D) and long-term microvascular complications including diabetic retinopathy (DR).

METHODS

In this study, a T2D cohort that accurately matches the characteristics of the general population was employed to find microRNA (miRNA) signatures that are correlated with glycemic and β cell function measurements. Targeted miRNA profiling was performed in (471) T2D individuals with or without DR and (491) (non-diabetic) healthy controls from the Qatar Biobank. Discovery analysis identified 20 differentially expressed miRNAs in T2D compared to controls, of which miR-223-3p was significantly upregulated (fold change:5.16, p = 3.6e-02) and positively correlated with glucose and hemoglobin A1c (HbA1c) levels (p-value = 9.88e-04 and 1.64e-05, respectively), but did not show any significant associations with insulin or C-peptide. Accordingly, we performed functional validation using a miR-223-3p mimic (overexpression) under control and hyperglycemia-induced conditions in a zebrafish model.

RESULTS

Over-expression of miR-223-3p alone was associated with significantly higher glucose (42.7 mg/dL, n = 75 vs 38.7 mg/dL, n = 75, p = 0.02) and degenerated retinal vasculature, and altered retinal morphology involving changes in the ganglion cell layer and inner and outer nuclear layers. Assessment of retinal angiogenesis revealed significant upregulation in the expression of vascular endothelial growth factor and its receptors, including kinase insert domain receptor. Further, the pancreatic markers, pancreatic and duodenal homeobox 1, and the insulin gene expressions were upregulated in the miR-223-3p group.

CONCLUSION

Our zebrafish model validates a novel correlation between miR-223-3p and DR development. Targeting miR-223-3p in T2D patients may serve as a promising therapeutic strategy to control DR in at-risk individuals.

Downregulation of plasma microRNA-29c-3p expression may be a new risk factor for diabetic retinopathy

BACKGROUND

Circulation miRNAs have emerged as new biomarkers for identifying and monitoring the microvascular complications of diabetes. The aim of this study is to evaluate the levels of five candidate miRNAs (miR-29c-3p, miR-18a, miR-31, miR-181 and miR-20a) in patients with diabetic retinopathy (DR) and their relationship with disease severity.

METHODS

The study included 31 diabetes patients without DR (NDR group), 68 patients with DR (DR group) and 30 healthy controls (HC group). Twenty-five of patients with DR were proliferative DR (PDR group) and 43 were non-proliferative DR (NPDR group) patients. Metabolic parameters and serum vascular endothelial growth factor (VEGF) levels of all participants were measured. Circulating miRNAs levels were determined by quantitative real-time PCR. Fundus examinations of all patients were performed by a single ophthalmologist.

RESULTS

VEGF levels were significantly higher in the NDR, and DR groups compared to HC group (P=0.011 and P=0.014, respectively). Plasma miR-29c-3p was downregulated in diabetic patients with retinopathy and without retinopathy. This downregulation was more prominent in diabetic patients without retinopathy compared to those with retinopathy (P=0.016). There was no significant difference in plasma levels of miR-18a, miR-20a, miR-18a and miR-31 between diabetic subjects with and without retinopathy (P>0.05). There was no correlation between DR severity and the levels of miRNAs (P>0.05). In multivariate logistic regression analysis, it was found that changes in plasma miR-29c-3p expression of diabetic patients increased DR risk independent of other risk factors.

CONCLUSIONS

Plasma miR-29c-3p expression is downregulated in diabetic patients with and without retinopathy, and changes in this miRNA are an independent risk factor for the development of DR.

Diabetic Retinopathy: Soluble and Imaging Ocular Biomarkers

Diabetic retinopathy (DR), the most common microvascular complication of diabetes mellitus, represents the leading cause of acquired blindness in the working-age population. Due to the potential absence of symptoms in the early stages of the disease, the identification of clinical biomarkers can have a crucial role in the early diagnosis of DR as well as for the detection of prognostic factors. In particular, imaging techniques are fundamental tools for screening, diagnosis, classification, monitoring, treatment planning and prognostic assessment in DR. In this context, the identification of ocular and systemic biomarkers is crucial to facilitate the risk stratification of diabetic patients; moreover, reliable biomarkers could provide prognostic information on disease progression as well as assist in predicting a patient's response to therapy. In this context, this review aimed to provide an updated and comprehensive overview of the soluble and anatomical biomarkers associated with DR.

MicroRNA Profiling from Tears as a Potential Non-invasive Method for Early Detection of Diabetic Retinopathy

Diabetic retinopathy (DR) is a vascular complication of diabetes that can lead to partial or complete loss of vision. Early detection and treatment of DR can prevent blindness. Regular clinical examination is recommended for DR diagnosis; however, it is not always possible or feasible due to limited resources, expertise, time, and infrastructure. Several clinical and molecular biomarkers are proposed for the prediction of DR including microRNAs. MicroRNAs are a class of small non-coding RNAs that are found in biofluids and can be measured using reliable and sensitive methods. The most commonly used biofluid for microRNA profiling is plasma or serum; however, tear fluid (tears) is also demonstrated to contain microRNAs. MicroRNAs isolated from tears present a non-invasive source for DR detection. Different methods of microRNA profiling are available including digital PCR-based methods that can detect up to a single copy of microRNA in the biofluids. Here, we describe microRNA isolation from tears using manual method as well as using a high-throughput automated platform followed by microRNA profiling using digital PCR system.

MicroRNA-150 (miR-150) and Diabetic Retinopathy: Is miR-150 Only a Biomarker or Does It Contribute to Disease Progression?

Diabetic retinopathy (DR) is a chronic disease associated with diabetes mellitus and is a leading cause of visual impairment among the working population in the US. Clinically, DR has been diagnosed and treated as a vascular complication, but it adversely impacts both neural retina and retinal vasculature. Degeneration of retinal neurons and microvasculature manifests in the diabetic retina and early stages of DR. Retinal photoreceptors undergo apoptosis shortly after the onset of diabetes, which contributes to the retinal dysfunction and microvascular complications leading to vision impairment. Chronic inflammation is a hallmark of diabetes and a contributor to cell apoptosis, and retinal photoreceptors are a major source of intraocular inflammation that contributes to vascular abnormalities in diabetes. As the levels of microRNAs (miRs) are changed in the plasma and vitreous of diabetic patients, miRs have been suggested as biomarkers to determine the progression of diabetic ocular diseases, including DR. However, few miRs have been thoroughly investigated as contributors to the pathogenesis of DR. Among these miRs, miR-150 is downregulated in diabetic patients and is an endogenous suppressor of inflammation, apoptosis, and pathological angiogenesis. In this review, how miR-150 and its downstream targets contribute to diabetes-associated retinal degeneration and pathological angiogenesis in DR are discussed. Currently, there is no effective treatment to stop or reverse diabetes-caused neural and vascular degeneration in the retina. Understanding the molecular mechanism of the pathogenesis of DR may shed light for the future development of more effective treatments for DR and other diabetes-associated ocular diseases.

miR-145, miR-92a and miR-375 Show Differential Expression in Serum from Patients with Diabetic Retinopathies

Diabetic retinopathies are important disabling conditions. Micro-RNAs (miRNAs) are regulators of gene expression and diseases can change their expression. Our aim was to analyze the expression of miRNAs in serum and vitreous samples from patients with diabetic retinopathies. The following groups and number of individuals were included: proliferative diabetic retinopathy (PDR) (n = 16), diabetic macular edema (DME) (n = 17), and idiopathic epiretinal membrane (IEM) as non-diabetic controls (n = 23). The initial miRNA expression was explored using TaqMan low-density arrays (TLDAs) with subsequent validation through a quantitative polymerase chain reaction (qPCR). Target genes were identified through bioinformatic tools for enrichment analysis. The TLDAs revealed the following miRNAs with differential expression in terms of PDR vs. IEM: miR-320a-3p, miR-92a-3p, and miR-375-3p in the serum, with miR-541-5p and miR-223-5p in the vitreous samples. DME vs IEM: miR-486-5p, miR-145-5p, miR-197-3p, and miR-125b-5p in the serum, and miR-212-3p in vitreous samples. PDR vs. DME: miR-486-5p, miR-100-5p, miR-328-3p, miR-660-5p, and miR-145 in the serum and none in the vitreous samples. Validation was confirmed only for miR-145, miR-92a, and miR-375 in the serum. The relevant enriched pathways for these three validated miRNAs, miR-145, miR-92a, and miR-375 were the vascular endothelial growth factor and its receptor, hepatocyte growth factor receptor, epidermal growth factor, focal adhesion, and phosphoinositide 3-kinase. Our results support the involvement of miRNAs in the pathophysiology of diabetic retinopathies and reinforce their potential as biomarkers or therapeutic resources.

Investigation of Influencing Factors on the Prevalence of Retinopathy in Diabetic Patients Based on Medical Big Data

As one of the most important organs of human beings, the eyes can receive external visual information and play an important role in perception. Therefore, the method of maintaining eye health is a problem that people pay attention to. Omental disease is one of the most serious microvascular complications in diabetic patients, and it is also the main cause of blindness in patients. The purpose of this article is to investigate the main factors that influence the prevalence of retinopathy in diabetic patients based on medical big data. In this article, a method for investigating the causes of the incidence of retinopathy in diabetic patients based on medical big data is proposed, and a questionnaire survey method and other methods are used for experimental investigation. Combining the data in the figure in the experiment in this article, it can be seen that among diabetic patients, the prevalence of diabetes in men is 12.4%, and the prevalence of diabetes in women is 8.4%. From the data in the figure, it can be known that the rate of retinopathy caused by various factors is between 5% and 7%, and the total prevalence of retinopathy is 47.5%. There are many factors affecting the prevalence of retinopathy in diabetic patients, such as the duration of diabetes, urinary albumin index, glycosylated hemoglobin index, and fasting blood glucose level; various factors lead to an increase in the prevalence of retinopathy in diabetic patients. The results show that there are many factors affecting the prevalence of retinopathy in diabetic patients, so patients should pay attention to exercise, control their diet, and prevent retinopathy.

Involvement of miR-126 rs4636297 and miR-146a rs2910164 polymorphisms in the susceptibility for diabetic retinopathy: a case-control study in a type 1 diabetes population

BACKGROUND AND PURPOSE

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression. MiRNA-126 and miRNA-146a have been described as having abnormal expressions in diabetic retinopathy (DR) patients. Polymorphisms in genes codifying miRNAs (miRSNPs) may alter the expression of the corresponding miRNA and, thus, interfere with susceptibility to DR. Therefore, miRSNPs in miR-126 and miR-146a genes could be associated with DR susceptibility. The purpose of this study was to investigate the association between miR-126 rs4636297 (G/A) and miR-146a rs2910164 (G/C) miRSNPs and DR.

METHODS

This case-control study included 195 type 1 diabetes mellitus (T1DM) patients with DR (cases) and 215 patients without DR and with ≥10 years of T1DM (controls). MiRSNPs were genotyped by real-time PCR.

RESULTS

Genotype distributions of two analysed miRSNPs were in Hardy-Weinberg equilibrium in controls (p > 0.050). Frequencies of the miR-126 rs4636297 miRSNP were not significantly different between case and control groups (p = 0.169). However, after adjustment for age, glycated haemoglobin, triglycerides, estimated glomerular filtration rate and ethnicity, the A allele of this miRSNP was associated with protection for DR under additive [OR: 0.444 (95% CI: 0.211-0.936), p = 0.033] and dominant [OR: 0.512 (95% CI: 0.303-0.865), p = 0.012] inheritance models. Genotype and allele frequencies of miR-146a rs2910164 miRSNP did not differ between groups (p = 0.368 and p = 0.957), and this polymorphism was not associated with DR when assuming different inheritance models.

CONCLUSION

Our results suggest an association between the A allele of miR-126 rs4636297 miRSNP and protection for DR in a Southern Brazilian population.

Plasma miR-26a-5p is a biomarker for retinal neurodegeneration of early diabetic retinopathy

PURPOSE

Retinal neurodegeneration is an early pathological change in diabetic retinopathy (DR). Early-stage retinal neurodegeneration is usually asymptomatic. This study aims to identify circulating microRNAs (miRNAs) as sensitive biomarkers for early retinal neurodegeneration.

METHODS

We profiled the plasma miRNA expression in three mild nonproliferative diabetic retinopathy (NPDR) cases and three matched non-DR patients using RNA sequencing. The differential miRNAs were validated with qRT-PCR. The retinal nerve fibre layer (RNFL) thickness of the eyes was measured using spectral-domain Optical coherence tomography (SD-OCT). The association between differential miRNAs and RNFL thickness was analysed using the Pearson correlation analysis. Bioinformatics tools were used to predict potential targets of miRNA associated with RNFL thickness and investigate the functions of the potential target genes.

RESULTS

RNA sequencing identified 69 differential miRNAs and eight of them were reported to be associated with DR. The qRT-PCR for these eight miRNAs validated the down-regulation of circulating miR-26a-5p and miR-126-5p in a larger validating cohort. A positive correlation between plasma miR-26a-5p level and the RNFL thickness of the superior quadrant of both eyes was identified in another cohort, including 33 mild NPDR cases, 33 matched non-DR patients and 20 healthy controls. Furthermore, 367 candidate targets of miR-26a-5p were predicted. The functional studies revealed that these target genes are profoundly involved in various cellular functions and signalling pathways.

CONCLUSIONS

Circulating miR-26a-5p is a potential biomarker for early-stage retinal neurodegeneration and it may be involved in the development of DR via profoundly influencing the functions of retinal cells.

Regulatory microRNAs in Brown, Brite and White Adipose Tissue

MicroRNAs (miRNAs) constitute a class of short noncoding RNAs which regulate gene expression by targeting messenger RNA, inducing translational repression and messenger RNA degradation. This regulation of gene expression by miRNAs in adipose tissue (AT) can impact on the regulation of metabolism and energy homeostasis, particularly considering the different types of adipocytes which exist in mammals, i.e., white adipocytes (white AT; WAT), brown adipocytes (brown AT; BAT), and inducible brown adipocytes in WAT (beige or brite or brown-in-white adipocytes). Indeed, an increasing number of miRNAs has been identified to regulate key signaling pathways of adipogenesis in BAT, brite AT, and WAT by acting on transcription factors that promote or inhibit adipocyte differentiation. For example, MiR-328, MiR-378, MiR-30b/c, MiR-455, MiR-32, and MiR-193b-365 activate brown adipogenesis, whereas MiR-34a, MiR-133, MiR-155, and MiR-27b are brown adipogenesis inhibitors. Given that WAT mainly stores energy as lipids, whilst BAT mainly dissipates energy as heat, clarifying the effects of miRNAs in different types of AT has recently attracted significant research interest, aiming to also develop novel miRNA-based therapies against obesity, diabetes, and other obesity-related diseases. Therefore, this review presents an up-to-date comprehensive overview of the role of key regulatory miRNAs in BAT, brite AT, and WAT.

MicroRNA-15b Targets VEGF and Inhibits Angiogenesis in Proliferative Diabetic Retinopathy

BACKGROUND

Vascular endothelial growth factor (VEGF)-induced angiogenesis is a critical compensatory response to microvascular rarefaction in the diabetic retina that contributes to proliferative diabetic retinopathy (PDR). In this study, we sought to determine the role of specific micro ribonucleic acids (RNAs) (miRs) associated with VEGF in patients with PDR pathology.

METHODS

RNA sequencing was employed to detect differentially circulating miR associated with VEGF in patients with diabetes mellitus (DM), nonproliferative diabetic retinopathy (NPDR) and PDR. Quantitative real-time polymerase chain reaction was performed to measure the concentration of miR-15b in the serum of patients with DM (n = 115), NPDR (n = 47), or PDR (n = 76). The effects of miR-15b on DR and regulation of VEGF and endothelial cell function were also characterized.

RESULTS

We demonstrated that circulating miR-15b was directly associated with VEGF compared with other miRs in patients with PDR. We found a significant inverse relationship between low levels of miR-15b and high levels of VEGF in patients with PDR when compared with the DM or NPDR groups. We found that miR-15b regulates the expression of VEGF by targeting the 3'-untranslated regions to inhibit its transcription. Similarly, overexpression of miR-15b suppressed vascular abnormalities in vivo in diabetic GK rats, inhibiting endothelial tube formation and VEGF expression.

CONCLUSION

Circulating miR-15b is associated with PDR and may be targeted to regulate VEGF expression and angiogenesis.

Emerging Roles of microRNAs as Biomarkers and Therapeutic Targets for Diabetic Neuropathy

Diabetic neuropathy (DN) is the most prevalent chronic complication of diabetes mellitus. The exact pathophysiological mechanisms of DN are unclear; however, communication network dysfunction among axons, Schwann cells, and the microvascular endothelium likely play an important role in the development of DN. Mounting evidence suggests that microRNAs (miRNAs) act as messengers that facilitate intercellular communication and may contribute to the pathogenesis of DN. Deregulation of miRNAs is among the initial molecular alterations observed in diabetics. As such, miRNAs hold promise as biomarkers and therapeutic targets. In preclinical studies, miRNA-based treatment of DN has shown evidence of therapeutic potential. But this therapy has been hampered by miRNA instability, targeting specificity, and potential toxicities. Recent findings reveal that when packaged within extracellular vesicles, miRNAs are resistant to degradation, and their delivery efficiency and therapeutic potential is markedly enhanced. Here, we review the latest research progress on the roles of miRNAs as biomarkers and as potential clinical therapeutic targets in DN. We also discuss the promise of exosomal miRNAs as therapeutics and provide recommendations for future research on miRNA-based medicine.

Decreased miR-150 in obesity-associated type 2 diabetic mice increases intraocular inflammation and exacerbates retinal dysfunction

INTRODUCTION

Diabetic retinopathy (DR) is the leading cause of blindness among the working population in the USA. Current therapies, including anti-vascular endothelial growth factor treatments, cannot completely reverse the visual defects induced by DR. MicroRNA-150 (miR-150) is a regulator that suppresses inflammation and pathological angiogenesis. In patients with diabetes, miR-150 is downregulated. As chronic inflammation is a major contributor to the pathogenesis of DR, whether diabetes-associated decrease of miR-150 is merely associated with the disease progression or decreased miR-150 causes retinal inflammation and pathological angiogenesis is still unknown.

RESEARCH DESIGN AND METHODS

We used high-fat diet (HFD)-induced type 2 diabetes (T2D) in wild type (WT) and miR-150 knockout (miR-150^-/-) mice for this study and compared retinal function and microvasculature morphology.

RESULTS

We found that WT mice fed with an HFD for only 1 month had a significant decrease of miR-150 in the blood and retina, and retinal light sensitivity also decreased. The miR-150^-/- mice on the HFD developed diabetes similar to that of the WT. At 7-8 months old, miR-150^-/- mice under normal diet had increased degeneration of retinal capillaries compared with WT mice, indicating that miR-150 is important in maintaining the structural integrity of retinal microvasculature. Deletion of miR-150 worsened HFD-induced retinal dysfunction as early as 1 month after the diet regimen, and it exacerbated HFD-induced T2DR by further increasing retinal inflammation and microvascular degeneration.

CONCLUSION

These data suggest that decreased miR-150 caused by obesity or diabetic insults is not merely correlated to the disease progression, but it contributes to the retinal dysfunction and inflammation, as well as the development of DR.

MiR-221-3p regulates the microvascular dysfunction in diabetic retinopathy by targeting TIMP3

Diabetic retinopathy is one of the major complications of diabetes and the main cause to lead to blindness for diabetic patients. However, the exact mechanisms involved in the progression of diabetic retinopathy are not completely known. Herein, we demonstrated a novel role of miR-221-3p in the microvascular dysfunction in diabetic retinopathy. MiR-221-3p expression was found to be substantially upregulated in the retina samples of diabetic rats. Besides, ganglion cell layer, inner nuclear layer, outer nuclear layer, and retinal pigment epithelium layer of diabetic rats expressed higher miR-221-3p than the matched areas of normal rats. High glucose-treated retinal microvascular endothelial cells RF/6A and HRECs exhibited higher miR-221-3p than that in normal condition. MiR-221-3p inhibition could alleviate the retinal vascular leakage induced by diabetes in vivo as evaluated by Evans blue leakage assay, and reduce the proliferation, accelerate the apoptosis development, and inhibit the migration capacity of high glucose-treated RF/6A cells in vitro, while miR-221-3p overexpression partially enhanced the detrimental effects. By bioinformatics analysis and luciferase reporter assay, we identified that TIMP3 is the direct target of miR-221-3p. TIMP3 overexpression counteracted the effect of miR-221-3p on the vessel leakage and endothelial cell function. In conclusion, this study highlights the negative role of miR-221-3p in the microvascular dysfunction in diabetic retinopathy by targeting TIMP3, representing a potential therapeutic target for human diabetic retinopathy.

Identification of potential molecular targets associated with proliferative diabetic retinopathy

BACKGROUND

This study aimed to identify and evaluate potential molecular targets associated with the development of proliferative diabetic retinopathy (DR).

METHODS

The microarray dataset "GSE60436" generated from fibrovascular membranes (FVMs) associated with proliferative DR was downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) from the active FVMs and control or inactive FVMs and control were evaluated and co-DEGs were identified using VEEN analysis. Functional enrichment analysis, and protein-protein interactions (PPI) network and module analyses were performed on the upregulated and downregulated coDEGs. Finally, several predictions regarding microRNAs (miRNAs) and transcription factors (TFs) were made to construct a putative TF-miRNA-target network.

RESULTS

A total of 1475 co-DEGs were screened in active/inactive FVM samples, including 461 upregulated and 1014 downregulated genes, which were enriched for angiogenesis [Hypoxia Inducible Factor 1 Subunit Alpha (HIF1A) and Placental Growth Factor (PGF)] and visual perception, respectively. In the case of the upregulated co-DEGs, Kinesin Family Member 11 (KIF11), and BUB1 Mitotic Checkpoint Serine/Threonine Kinase (BUB1) exhibited the highest values in both the PPI network and module analyses, as well as the genes related to mitosis. In the case of downregulated co-DEGs, several G protein subunits, including G Protein Subunit Beta 3 (GNB3), exhibited the highest values in both the PPI network and module analyses. The genes identified in the module analysis were found to be from the signal transduction-related pathways. In addition, we were able to identify four miRNAs and five TFs, including miR-136 and miR-374.

CONCLUSIONS

In brief, HIF1A, PGF, KIF11, G protein subunits, and miR-136, miR-374 may all be involved in angiogenesis, retinal endothelial cell proliferation, and visual signal transduction in proliferative DR. This study provides a number of novel insights that may aid the development of future studies dedicated to discovering novel therapeutic targets in proliferative DR.

Glucagon-like Peptide 1 Receptor Agonists, Diabetic Retinopathy and Angiogenesis: The AngioSafe Type 2 Diabetes Study

AIMS

Recent trials provide conflicting results on the association between glucagon-like peptide 1 receptor agonists (GLP-1RA) and diabetic retinopathy (DR). The aim of the AngioSafe type 2 diabetes (T2D) study was to determine the role of GLP-1RA in angiogenesis using clinical and preclinical models.

METHODS

We performed two studies in humans. In study 1, we investigated the effect of GLP-1RA exposure from T2D diagnosis on the severity of DR, as diagnosed with retinal imaging (fundus photography). In study 2, a randomized 4-week trial, we assessed the effect of liraglutide on circulating hematopoietic progenitor cells (HPCs), and angio-miRNAs.We then studied the experimental effect of Exendin-4, on key steps of angiogenesis: in vitro on human endothelial cell proliferation, survival and three-dimensional vascular morphogenesis; and in vivo on ischemia-induced neovascularization of the retina in mice.

RESULTS

In the cohort of 3154 T2D patients, 10% displayed severe DR. In multivariate analysis, sex, disease duration, glycated hemoglobin (HbA1c), micro- and macroangiopathy, insulin therapy and hypertension remained strongly associated with severe DR, while no association was found with GLP-1RA exposure (o 1.139 [0.800-1.622], P = .47). We further showed no effect of liraglutide on HPCs, and angio-miRNAs. In vitro, we demonstrated that exendin-4 had no effect on proliferation and survival of human endothelial cells, no effect on total length and number of capillaries. Finally, in vivo, we showed that exendin-4 did not exert any negative effect on retinal neovascularization.

CONCLUSIONS

The AngioSafe T2D studies provide experimental and clinical data confirming no effect of GLP-1RA on angiogenesis and no association between GLP-1 exposure and severe DR.

Downregulation of circulating miR-320a and target gene prediction in patients with diabetic retinopathy

Objective

To evaluate the expression of a set of miRNAs to identify differentially expressed miRNAs that might be considered reliable biomarkers on Diabetic Retinopathy (DR) blood samples.

Results

Expression levels of MiR-320a, MiR-342-3p, MiR-155, MiR-99a, MiR-29a and MiR-27b were analyzed in 60 healthy controls, 48 Diabetes Melitus (DM) without DR patients and 62 DR patients by qRT-PCR. MiR-320a was shown to be downregulated in the plasma of DR patients compared with DM patients without DR and healthy subjects. Target genes were predicted using miRWalk3.0, miR targeting data and target gene interaction data were imported to Cytoscape to visualize and merge networks and top ranked predicted genes were run through Ontology Genes to perform enrichment analysis on gene sets and classification system to identify biological processes and reactome pathways associated with DR. Highly scored target genes of miR-320a were categorized for various biological processes, including negative regulation of cell aging, negative regulation of cellular protein metabolic process and regulation of cellular response to stress that are critical to the development of DR. Our findings suggest that MiR-320a may have a role in the pathogenesis of DR and may represent novel biomarkers for this disease.

Blood Co-Circulating Extracellular microRNAs and Immune Cell Subsets Associate with Type 1 Diabetes Severity

Immune cell subsets and microRNAs have been independently proposed as type 1 diabetes (T1D) diagnostic and/or prognostic biomarkers. Here, we aimed to analyze the relationships between peripheral blood circulating immune cell subsets, plasmatic microRNAs, and T1D. Blood samples were obtained from both children with T1D at diagnosis and age-sex matched healthy controls. Then, immunophenotype assessed by flow cytometry was coupled with the quantification of 60 plasmatic microRNAs by quantitative RT-PCR. The associations between immune cell frequency, plasmatic microRNAs, and the parameters of pancreatic loss, glycemic control, and diabetic ketoacidosis were assessed by logistic regression models and correlation analyses. We found that the increase in specific plasmatic microRNAs was associated with T1D disease onset (let-7c-5p, let-7d-5p, let-7f-5p, let-7i-5p, miR-146a-5p, miR-423-3p, and miR-423-5p), serum C-peptide concentration (miR-142-5p and miR-29c-3p), glycated hemoglobin (miR-26a-5p and miR-223-3p) and the presence of ketoacidosis (miR-29c-3p) more strongly than the evaluated immune cell subset frequency. Some of these plasmatic microRNAs were shown to positively correlate with numbers of blood circulating B lymphocytes (miR-142-5p) and CD4⁺CD45RO⁺ (miR-146a-5p and miR-223-3p) and CD4⁺CD25⁺ cells (miR-423-3p and miR-223-3p) in children with T1D but not in healthy controls, suggesting a disease-specific microRNA association with immune dysregulation in T1D. In conclusion, our results suggest that, while blood co-circulating extracellular microRNAs and immune cell subsets may be biologically linked, microRNAs may better provide powerful information about T1D onset and severity.

Integrated analysis of gene modulation profile identifies pathogenic factors and pathways in the liver of diabetic mice

Purpose

Type-2 diabetes mellitus (T2D) is a metabolic disorder that can progress to a serious chronic disease and frequently develops in obese individuals in association with various pathogenic complications that shorten the lifespan of these patients. The liver is an important organ regulating lipid metabolism, which is damaged in both obesity and T2D; however, the specific pathways involved in these pathogenic effects remain unclear. Establishing a suitable animal model that effectively mimics the human biological condition is a critical factor to allow for precise identification of T2D-related genes.

Methods

The KK.Cg-A^y mouse strain is one such model that has offered insight into obesity-related T2D pathogenesis. To comprehensively assess the association between obesity and T2D, in the present study, we performed microarray analysis on liver tissue samples of KK.Cg-A^y and KK-α/α wild-type mice to examine differences in gene expression and methylation patterns and their related biological processes and pathways.

Results

We found that inflammation accompanied by abnormal lipid metabolism led to the spontaneous mechanism of obesity-induced diabetes, resulting in differential expression of some genes related to the terms of insulin resistance and glucose tolerance. Surprisingly, disruption of steroid biosynthesis strongly facilitated the diabetic pathogenesis. To support these findings, we highlighted some candidate genes and determined their relationships in biological networks of obesity-induced T2D.

Conclusion

These findings provide valuable reference data that can facilitate further detailed investigations to elucidate the pathogenic mechanism of obesity-induced diabetes in mice, which can be associated with the human condition to inform new prevention and treatment strategies.

Identification of miR-328-3p as an endogenous reference gene for the normalization of miRNA expression data from patients with Diabetic Retinopathy

Diabetic Retinopathy, the main cause of visual loss and blindness among working population, is a complication of Diabetes mellitus (DM), which has been described as a major public health challenge, so it is important to identify biomarkers to predict and to stratify patient´s possibility for developing DR. MicroRNAs (miRNAs) are small non-coding RNA molecules that have showed to be promising disease biomarkers and association of miRNAs with the possibility to develop DR has been reported. However, evaluating miRNA expression involves normalization of RT-qPCR data using internal reference genes that should be properly determined, considering their impact on expression levels calculation and, until date, there is no unanimity on reference miRNAs for the investigation of circulating miRNAs in DR. We aimed to estimate the appropriateness of a group of miRNAs as normalizers to identify which might be considered steady internal reference genes in expression studies on DR plasma samples. Expression levels of candidates were analyzed in 60 healthy controls, 48 DM without DR patients and 62 DR patients with two statistical tools: NormFinder and RefFinder. MiR-328-3p was the most stable gene and we also investigated the effect of gene normalization, demonstrating that different normalization strategies have important implications for accurate data interpretation.

Identification of Diagnostic and Prognostic microRNAs for Recurrent Vitreous Hemorrhage in Patients with Proliferative Diabetic Retinopathy

MicroRNAs (miRNAs) can provide insight into the pathophysiological states of ocular tissues such as proliferative diabetic retinopathy (PDR). In this study, differences in miRNA expression in vitreous from PDR patients with and without incidence of recurrent vitreous hemorrhage (RVH) after the initial pars-plana vitrectomy (PPV) were analyzed, with the aim of identifying biomarkers for RVH. Fifty-four consented vitreous samples were analyzed from patients undergoing PPV for PDR, of which eighteen samples underwent a second surgery due to RVH. Ten of the sixty-six expressed miRNAs (miRNAs-19a, -20a, -22, -27a, -29a, -93, -126, -128, -130a, and -150) displayed divergences between the PDR vitreous groups and to the control. A significant increase in the miRNA-19a and -27a expression was determined in PDR patients undergoing PPV as compared to the controls. miRNA-20a and -93 were significantly upregulated in primary PPV vitreous samples of patients afflicted with RVH. Moreover, this observed upregulation was not significant between the non-RVH and control group, thus emphasizing the association with RVH incidence. miRNA-19a and -27a were detected as putative vitreous biomarkers for PDR, and elevated levels of miRNA-20a and -93 in vitreous with RVH suggest their biomarker potential for major PDR complications such as recurrent hemorrhage incidence.

Gene polymorphism and plasma levels of miR-155 in diabetic retinopathy

Circulating microRNA-155 (miR-155) is associated with type 2 diabetes mellitus (T2DM) and the rs767649 polymorphism in the pre-MIR155 gene is associated with miR-155 expression. However, their relationship with diabetic retinopathy (DR) is still unknown. Therefore, the aim of this case-control study was to test the hypothesis that the rs767649 polymorphism in the pre-MIR155 gene is associated with DR in South Brazilians with T2DM. We also evaluated the association of plasma levels of miR-155 with DR and the rs767649 polymorphism in a subgroup of subjects. The rs767649 polymorphism was genotyped in 139 blood donors and 546 T2DM patients (244 had no DR, 161 had non-proliferative DR and 141 had proliferative DR). miR-155 expression was quantified in 20 blood donors and 60 T2DM patients (20 from each group). Among T2DM patients, the carriership of the A allele and the A allele were more frequent in subjects with DR than in those without it (P < 0.05), and the A allele was independently associated with an increased risk of DR (adjusted OR = 2.12, 95% CI = 1.12-4.01). The plasma levels of miR-155 were lower in T2DM patients than in blood donors (P < 0.001). However, the miR-155 levels did not differ according to the presence and severity of DR or according to rs767649 genotypes among T2DM patients. These findings support that the rs767649 polymorphism in the pre-MIR155 gene is associated with DR in T2DM and that the miR-155 plasma levels might be associated with T2DM. Additional studies are needed to further investigate their clinical significance in DR and T2DM.

MicroRNAs as biomarkers of diabetic retinopathy and disease progression

Diabetes mellitus, together with its complications, has been increasing in prevalence worldwide. Its complications include cardiovascular disease (e.g., myocardial infarction, stroke), neuropathy, nephropathy, and eye complications (e.g., glaucoma, cataracts, retinopathy, and macular edema). In patients with either type 1 or type 2 diabetes mellitus, diabetic retinopathy is the leading cause of visual impairment or blindness. It is characterized by progressive changes in the retinal microvasculature. The progression from nonproliferative diabetic retinopathy to a more advanced stage of moderate to severe nonproliferative diabetic retinopathy and proliferative diabetic retinopathy occurs very quickly after diagnosis of mild nonproliferative diabetic retinopathy. The etiology of diabetic retinopathy is unclear, and present treatments have limited effectiveness. Currently diabetic retinopathy can only be diagnosed by a trained specialist, which reduces the population that can be examined. A screening biomarker of diabetic retinopathy with high sensitivity and specificity would aid considerably in identifying those individuals in need of clinical assessment and treatment. The majority of the studies reviewed identified specific microRNAs in blood serum/plasma able to distinguish diabetic patients with retinopathy from those without retinopathy and for the progresion of the disease from nonproliferative diabetic retinopathy to proliferative diabetic retinopathy. In addition, certain microRNAs in vitreous humor were dysregulated in proliferative diabetic retinopathy compared to controls. A very high percentage of patients with diabetic retinopathy develop Alzheimer's disease. Thus, identifying diabetic retinopathy by measurement of suitable biomarkers would also enable better screening and treatment of those individuals at risk of Alzheimer's disease.

Circulatory miR-98-5p levels are deregulated during diabetes and it inhibits proliferation and promotes apoptosis by targeting PPP1R15B in keratinocytes

Although deregulated circulatory miRNA signatures during diabetes have been identified for some years now, the effects of such miRNAs on several target tissues are not yet thoroughly investigated. The skin that is nourished by components present in the circulation exhibits several notable abnormal features during diabetes. We, therefore, hypothesized that such altered circulatory miRNA levels might be critical in the onset and progression of impaired skin health during diabetes. RNA sequencing from blood samples of normal and type 2 diabetic human subjects identified 9 upregulated and 19 downregulated miRNAs. miR-98-5p was significantly downregulated and its overexpression down-regulated PPP1R15B levels in HaCaT cells and this was prevented by the miR-98-5p inhibitor. This was validated in human primary epidermal keratinocytes and further supported by a dual reporter luciferase assay of the PPP1R15B 3'UTR where miR-98-5p significantly decreased the luciferase activity which was prevented in the presence of the miRNA inhibitor and by mutation in the miRNA binding site. By targeting PPP1R15B, miR-98-5p increases levels of p-eIF2α, BiP and CHOP. Consequently, there was induction of apoptosis accompanied with decreased proliferation in the presence of miR-98-5p. Conversely, miR-98-5p inhibition alone inhibited apoptosis and promoted proliferation. Taken together, our data suggest that by targeting PPP1R15B, miR-98-5p induces apoptosis and decreases proliferation. As opposed to this since circulatory miR-98-5p levels are decreased in diabetes, we believe that this decrease in the circulation that feeds the skin layers might be a major contributor of hyperproliferation as seen in the skin during diabetes.Abbreviations: miRNAs: MicroRNAs; PPP1R15B: PPP1R15B: Protein Phosphatase 1 Regulatory Subunit 15B; TGFβR1: Transforming Growth Factor Beta Receptor 1; ER: Endoplasmic Reticulum; Bip: Binding Immunoglobulin Protein; Chop: CCAAT-enhancer-binding protein homologous protein; p-eIF2α: Eukaryotic Translation Initiation Factor 2a; Bax: Bcl2-associated X protein; Bcl-2: B-cell CLL/lymphoma 2; PCNA: Proliferating Cell Nuclear Antigen; K5: Cytokeratin 5; qRT-PCR: Quantitative Real-Time PCR; ESCC: Oesophageal squamous cell carcinoma; HCC: Hepatocellular carcinoma; CTHRC1: Collagen triple helix repeat containing 1; SALL4: Sal-like protein 4; TNFα: Tumour Necrosis Factor alpha; PGC-1β: Peroxisome Profilerator-activated receptor-γ coactivator-1β; IGF2BP1: Insulin-like growth factor 2 mRNA binding protein 1.

MiR-34c Participates in Diabetic Corneal Neuropathy Via Regulation of Autophagy

Purpose

To investigate the contribution and mechanism of miRNAs and autophagy in diabetic peripheral neuropathy.

Methods

In this study, we used streptozotocin (STZ)-induced type I diabetes C57 mice as animal models, and we detected the expression of miR-34c and autophagic intensity in trigeminal ganglion (TG) tissue. The bioinformatics software was used to predict and analyze the potential targets of miR-34c. Primary trigeminal ganglion neurons were cultured in vitro to investigate the effect of miR-34c on axon growth and survival of TG cells. A corneal epithelial damage-healing model was established on the diabetic mice, then miR-34c antagomir was injected subconjunctivally. The condition of corneal epithelial healing was observed through sodium fluorescein staining, and the peripheral nerve degeneration of the cornea was evaluated by β-tublin corneal nerve staining.

Results

The expression of miR-34c was significantly increased in TG tissue of type I diabetic mice by real-time PCR. Western blot showed that autophagy-related proteins Atg4B and LC3-II were significantly down-regulated in diabetes TG compared with normal control. Trigeminal neuron immunofluorescence showed that the length of the trigeminal ganglion cell synapses was significantly increased after miR-34c antagomir treatment compared with normal cultures. Subconjunctival injection of miR-34c antagomir can significantly promote corneal epithelium healing of diabetic mice and appreciably promote the regeneration of corneal nerve. At the same time, it can significantly increase the expression of autophagy in TG tissue of type I diabetic mice.

Conclusions

In this study , miR-34c was found to affect the growth of trigeminal sensory neurons and the repair of diabetic corneal nerve endings by acting directly on Atg4B.

RNA-Seq Revealed Novel Non-proliferative Retinopathy Specific Circulating MiRNAs in T2DM Patients

Background: Diabetic retinopathy (DR) is a common diabetes complication and was considered as the major cause of blindness among young adults. MiRNAs are a group of small non-coding RNAs regulating the expression of target genes and have been reported to be associated with the development of DR in a variety of molecular mechanisms. In this study, we aimed to identify miRNAs that are differentially expressed (DE) in the serum of DR patients. Methods: We recruited 21 type 2 diabetes mellitus (T2DM) inpatients of Chinese Han ancestry, consisting of 10 non-proliferative DR patients (DR group) and 11 non-DR T2DM patients (NDR group). MiRNA was extracted from fasting peripheral serum and quantified by RNA-seq. The expression levels of miRNA were evaluated and compared between the two groups, with adjustments made for age differences. The validated target genes of miRNAs were subjected to a pathway analysis. We also constructed a weighted polygenic risk score using the DE miRNA and evaluated its predictive power. Results: Five miRNAs were DE between DR and NDR groups (p-Value ≤ 0.01, LFC ≥ 2 or LFC ≤-2). These included miR-4448, miR-338-3p, miR-190a-5p, miR-485-5p, and miR-9-5p. In total, these miRNAs were validated to regulate 55 target genes. Four target genes were found to overlap with the NAD metabolism, sirtuin, and aging pathway, which was thought to control the vascular growth and morphogenesis. The predictive power of our polygenic risk score was apparently high (AUC = 0.909). However, it needs to be interpreted with caution. Conclusion: In this study, we discovered novel DR-specific miRNAs in human serum samples. These circulating miRNAs may represent the pathological changes in the retina in response to diabetes and may serve as non-invasive biomarkers for early DR risk prediction.

Plasma metabolomic profiling of proliferative diabetic retinopathy

Background

Proliferative diabetic retinopathy (PDR), a sight-threatening retinopathy, is the leading cause of irreversible blindness in adults. Despite strict control of systemic risk factors, a fraction of patients with diabetes develop PDR, suggesting the existence of other potential pathogenic factors underlying PDR. This study aimed to investigate the plasma metabotype of patients with PDR and to identify novel metabolite markers for PDR. Biomarkers identified from this study will provide scientific insight and new strategies for the early diagnosis and intervention of diabetic retinopathy.

Methods

A total of 1024 patients with type 2 diabetes were screened. To match clinical parameters between case and control subjects, patients with PDR (PDR, n = 21) or those with a duration of diabetes of ≥10 years but without diabetic retinopathy (NDR, n = 21) were assigned to the present case-control study. Distinct metabolite profiles of serum were examined using liquid chromatography-mass spectrometry (LC-MS).

Results

The distinct metabolites between PDR and NDR groups were significantly enriched in 9 KEGG pathways (P < 0.05, impact > 0.1), namely, alanine, aspartate and glutamate metabolism, caffeine metabolism, beta-alanine metabolism, purine metabolism, cysteine and methionine metabolism, sulfur metabolism, sphingosine metabolism, and arginine and proline metabolism. A total of 63 altered metabolites played important roles in these pathways. Finally, 4 metabolites were selected as candidate biomarkers for PDR, namely, fumaric acid, uridine, acetic acid, and cytidine. The area under the curve for these biomarkers were 0.96, 0.95, 1.0, and 0.95, respectively.

Conclusions

This study suggested that impairment in the metabolism of pyrimidines, arginine and proline were identified as metabolic dysregulation associated with PDR. And fumaric acid, uridine, acetic acid, and cytidine might be potential biomarkers for PDR. Fumaric acid was firstly reported as a novel metabolite marker with no prior reports of association with diabetes or diabetic retinopathy, which might provide insights into potential new pathogenic pathways for diabetic retinopathy.

MMP targeting in the battle for vision: Recent developments and future prospects in the treatment of diabetic retinopathy

Matrix metalloproteinases (MMPs) are enzymes capable of degrading nearly all types of extracellular matrix. They perform a wide range of roles in physiological processes, which is the reason for their strict regulation by numerous mechanisms including natural tissue inhibitors of metalloproteinases (TIMP). Research only started to shed light on more troublesome aspects of MMPs function, like cancer progression, Alzheimer's disease, atherosclerosis, ageing. Moreover, their profound role in diabetes is being carefully investigated including one of its most debilitating complications - diabetic retinopathy (DR), the leading cause of acquired blindness worldwide. Traditional treatment of this condition seems to be only mildly satisfactory, which elicited substantial interest in the field of new therapeutic methods including MMP targeting. So far, significant roles of MMP-2 and MMP-9 in the development of retinopathy have been established, with special attention given to the process of blood-retinal barrier impairment. Further exploration revealed MMP-10 and MMP-14 involvement as well as changes in MMP/TIMP ratio. In this review, we provide insight into MMPs role in diabetic retinopathy with a clarification of various mechanisms regulating MMP activity in the light of the recent studies. We conclude with an overview of novel DR therapies targeting MMPs and point to the need of further examination of their usefulness in clinical setting, with an eye towards future research.

Mitochondrial Stability in Diabetic Retinopathy: Lessons Learned From Epigenetics

Diabetic retinopathy remains the leading cause of acquired blindness in working-age adults. While the cutting-edge research in the field has identified many molecular, functional, and structural abnormalities, the exact molecular mechanism of this devastating disease remains obscure. Diabetic environment drives dysfunction of the power generator of the cell and disturbs the homeostasis of mitochondrial dynamic. Mitochondrial DNA (mtDNA) is damaged, the transcription of mtDNA-encoded genes is impaired, and the electron transport chain is compromised, fueling into a vicious cycle of free radicals. The hyperglycemic milieu also alters the epigenetic machinery, and mtDNA and other genes associated with mitochondrial homeostasis are epigenetically modified, further contributing to the mitochondrial damage. Thus, mitochondria appear to have a significant role in the development of diabetic retinopathy, and unraveling the mechanism responsible for their damage as well as the role of epigenetic modifications in mitochondrial homeostasis should identify novel therapeutic targets. This will have a major impact on inhibiting/halting diabetic retinopathy and preventing the loss of vision.

Micro-RNAs 518d-3p and 618 Are Upregulated in Individuals With Type 1 Diabetes With Multiple Microvascular Complications

Objective: To compare the serum micro-RNAs (miRNAs) profile of individuals with type 1 diabetes without microvascular complications vs. those with multiple severe microvascular complications, in order to identify epigenetically modulated pathways in these two groups of individuals. Research Design and Methods: A total of 10 subjects were selected among individuals followed in the Diabetes Outpatient Clinic and sorted according to the absence or presence of all microvascular complications. Samples from these participants were used for evaluation of serum miRNA expression profile employing a qRT-PCR assay with hydrolysis probes based on the Taqman Low Density Arrays (TLDA) system. The top six most differentially expressed miRNAs between the aforementioned groups were validated by qRT-PCR in additional 47 type 1 diabetes individuals sorted according to the absence or presence of all microvascular complications and matched for age, sex, degree of metabolic control, diabetes duration, and age at diagnosis. Results: Twenty one out of three hundred and seventy seven miRNAs were upregulated in the group of individuals with all microvascular complications vs. the group without complications. The following miRs were validated: 518-3p, 34a-5p, 126-5p, 425-5p, 618, and 139-5p and logistic regression analyses showed that miRNA-518-3p and miRNA-618 were positively associated with multiple microvascular complications after adjustment for age, sex, diabetes duration, HbA₁c and use of statin, angiotensin-converting enzyme inhibitors and amlodipine. Conclusions: In this cohort of type 1 diabetes individuals, serum miR-518d-3p and miR-618 were upregulated in those with diabetes kidney disease, diabetes retinopathy, peripheral neuropathy, and cardiovascular autonomic neuropathy in comparison to individuals with no microvascular complications.

Long Non-Coding RNA of Myocardial Infarction Associated Transcript (LncRNA-MIAT) Promotes Diabetic Retinopathy by Upregulating Transforming Growth Factor-β1 (TGF-β1) Signaling

Background

Long non-coding RNA of myocardial infarction associated transcript (lncRNA-MIAT) has a reported role in microvascular dysfunction. This study aimed to investigate the role of lncRNA-MIAT and its effects on transforming growth factor-β1 (TGF-β1) signaling in patients with diabetic retinopathy and in ARPE-19 adult retinal pigment epithelial cells in vitro.

Material/Methods

Study participants provided plasma samples and included patients with non-proliferative diabetic retinopathy (n=52), patients with diabetes without diabetic retinopathy (n=63), and healthy controls (n=56). Plasma levels of lncRNA-MIAT and TGF-β1 were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Pearson correlation analysis was performed on the plasma data, and the diagnostic relevance of plasma levels of lncRNA-MIAT for diabetic retinopathy was evaluated by receiver operating characteristic (ROC) curve analysis. Cells of the human retinal pigment epithelial cell line, ARPE-19, were cultured in high glucose with construction and transfection of a MIAT expression plasmid vector. Viability of ARPE-19 cells was detected by the MTT assay and Western blot measured the expression levels of TGF-β1.

Results

Plasma levels of lncRNA-MIAT were significantly increased in patients with diabetic retinopathy compared with patients with diabetes without diabetic retinopathy and with healthy controls. ARPE-19 cells cultured in a high glucose environment showed reduced cell viability and upregulation of lncRNA-MIAT expression.

Conclusions

Increased plasma levels of lncRNA-MIAT were significantly associated with the presence of diabetic retinopathy, and increased expression of lncRNA-MIAT reduced the viability of ARPE-19 cells in vitro by upregulating TGF-β1 signaling.

Association between microRNAs expression and signaling pathways of inflammatory markers in diabetic retinopathy

Diabetic retinopathy is one of the common and serious microvascular complications of diabetes mellitus, as hyperglycemia has metabolic effects on the retina. Hyperglycemia induces increased oxidative stress, which stimulates inflammation pathways and promotes vascular dysfunction of the retina that leads to increased capillary permeability and vascular leakage. One of the main factors involving diabetic retinopathy is the inflammation signaling pathways. In contemporary times, microRNAs (miRNAs) are identified as functional biomarkers for early detection and treatment of numerous diseases specifically diabetic retinopathy. MiRNAs can modulate gene expression through regulation of transcriptional and posttranscriptional of target genes. With that, miRNAs can regulate almost every cellular and developmental process, including the regulation of instinct immune responses and inflammation. The aim of this study is to investigate the role of miRNAs in inflammation pathways and the pathogenesis of diabetic retinopathy.

RNA Biology in Retinal Development and Disease

For decades, RNA has served in a supporting role between the genetic carrier (DNA) and the functional molecules (proteins). It is finally time for RNA to take center stage in all aspects of biology. The retina provides a unique opportunity to dissect the molecular underpinnings of neuronal diversity and disease. Transcriptome profiles of the retina and its resident cell types have unraveled unique features of the RNA landscape. The discovery of distinct RNA molecules and the recognition that RNA processing is a major cause of retinal neurodegeneration have prompted the design of biomarkers and novel therapeutic paradigms. We review here RNA biology as it pertains to the retina, emphasizing new avenues for investigations in development and disease.

Connexins and microRNAs: Interlinked players in regulating islet function?

Pancreatic β-cells are connected to neighboring endocrine cells through the adherin proteins and gap junctions. Connexin 36 (Cx36) is one of the most well-studied and abundantly expressed gap-junction proteins within rodent islets, which is important in coordinated insulin secretion. The expression of connexins is regulated at various levels and by several mechanisms; one of which is via microRNAs. In past 2 decades, microRNAs (miRNAs) have emerged as key molecules in developmental, physiologic and pathological processes. However, very few studies have demonstrated miRNA-mediated regulation of connexins. Even though there are no reports yet on miRNAs and Cx36; we envisage that considering the important role of connexins and microRNAs in insulin secretion, there would be common pathways interlinking these biomolecules. Here, we discuss the current literature on connexins and miRNAs specifically with reference to islet function.

Diabetic retinopathy: reversibility of epigenetic modifications and new therapeutic targets

In recent years, considerable progress has been made in the molecular mechanisms of epigenetics in disease development and progression, the reversible characteristics of epigenetic modification provide new insights for the treatment of such diseases. The pathogenesis of diabetic retinopathy (DR) has not yet been fully understood, treatment of refractory and recurrent diabetic macular edema remains a big change in clinical practice. This review emphasizes that reversibility of epigenetic modification could provide a new strategy for the prevention and treatment of diseases.

Role of MicroRNAs in Type 2 Diabetes and Associated Vascular Complications

Type 2 diabetes mellitus (T2DM) has become a major health threat worldwide. MicroRNAs (miRNAs) are a group of non-coding RNAs known to regulate various biological processes including the pathogenesis of T2DM. Recent studies have pointed out that specific miRNAs play a critical role in controlling β cell activities and the development of diabetic vascular complications. Their association with the disease pathogenesis and omnipresence in body fluids have made them important players for prognosis, diagnosis and management of T2DM. Owing to the limitations of classical biomarkers of diabetes such as fasting plasma glucose, glycosylated haemoglobin (HbA_1c) lack in predicting the risk of development of diabetes complications in a susceptible population. The miRNAs can act as ideal biomarkers for diabetes associated complications. Identification of specific miRNA signatures to detect diabetes and ideally to find out the risk of development of diabetes-associated complications in susceptible population is the essential requirement of the present clinical strategies for controlling diabetes worldwide. In this article, we summarize the potential miRNAs and miRNA signatures involved in the β cell activities and diabetes associated macrovascular and microvascular complications.

Cost-effectiveness of switching to insulin degludec from other basal insulins: evidence from Swedish real-world data

OBJECTIVES

Health economic analysis from a healthcare and societal point of view was conducted to assess the cost-effectiveness of insulin degludec (IDeg) after switching from other basal insulins in people with type 1 diabetes.

MATERIAL AND METHODS

This was a prospective, open-label, single arm, observational follow-up from August 2013 to October 2015 of 476 consecutive patients at Danderyd Hospital (Stockholm, Sweden) who switched to IDeg from other basal insulins (99% basal insulin analogs). The IMS CORE Diabetes Model (CDM) was used to predict the cost-effectiveness of life-long treatment with IDeg vs. other basal insulins, based on a Swedish setting.

RESULTS

Mean (SD) duration of follow-up was 21.7 (6.0) weeks. Mean HbA_1c decreased by 2.7 mmol/mol, mean basal insulin dose decreased by 13.1% (p < .0001), and mean bolus insulin dose decreased by 7.5% (p < .0001) after switching. Frequencies of non-severe daytime hypoglycemia and non-severe nocturnal hypoglycemia decreased by 12% (p = .0127) and 53% (p < .0001) respectively and severe hypoglycemia was reduced by 62% (p = .0225). The CDM predicted a gain in life expectancy of 0.33 years, a discounted gain in quality-adjusted life-years (QALYs) of 0.54, and lower estimated direct lifetime healthcare costs of SEK 22,757 for patients switching to IDeg. The incremental cost-effectiveness ratio (ICER) showed IDeg as dominant (i.e. higher effectiveness with a lower cost). Sensitivity analyses confirmed the results.

CONCLUSION

Based on this prospective, real-world, follow-up and using the CDM, it was estimated that switching to IDeg from other basal insulins translated into QALY gains including improved life expectancy and health-related quality of life, as well as dominant ICER, meaning cost-savings for the healthcare system. However, the study is limited by its observational design. Extrapolation into the future is only estimated since the actual treatment effect cannot be projected with certainty.

Comparisons of serum miRNA expression profiles in patients with diabetic retinopathy and type 2 diabetes mellitus

OBJECTIVES:

The aim of this study was to compare the expression levels of serum miRNAs in diabetic retinopathy and type 2 diabetes mellitus.

METHODS:

Serum miRNA expression profiles from diabetic retinopathy cases (type 2 diabetes mellitus patients with diabetic retinopathy) and type 2 diabetes mellitus controls (type 2 diabetes mellitus patients without diabetic retinopathy) were examined by miRNA-specific microarray analysis. Quantitative real-time polymerase chain reaction was used to validate the significantly differentially expressed serum miRNAs from the microarray analysis of 45 diabetic retinopathy cases and 45 age-, sex-, body mass index- and duration-of-diabetes-matched type 2 diabetes mellitus controls. The relative changes in serum miRNA expression levels were analyzed using the 2-ΔΔCt method.

RESULTS:

A total of 5 diabetic retinopathy cases and 5 type 2 diabetes mellitus controls were included in the miRNA-specific microarray analysis. The serum levels of miR-3939 and miR-1910-3p differed significantly between the two groups in the screening stage; however, quantitative real-time polymerase chain reaction did not reveal significant differences in miRNA expression for 45 diabetic retinopathy cases and their matched type 2 diabetes mellitus controls.

CONCLUSION:

Our findings indicate that miR-3939 and miR-1910-3p may not play important roles in the development of diabetic retinopathy; however, studies with a larger sample size are needed to confirm our findings.

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.

Differentially Expressed MicroRNAs in the Development of Early Diabetic Retinopathy

The pathological mechanisms of diabetic retinopathy (DR), a leading cause of blindness in adults with diabetes mellitus, remain incompletely understood. Because microRNAs (miRNAs) represent effective DR therapeutic targets, we identified aberrantly expressed miRNAs associated with cellular dysfunction in early DR and detected their potential targets. We exposed human retinal endothelial cells (HRECs) and a cell line of retinal pigment epithelial (RPE) cells to high glucose (25 mmol/L, 1-7 days) to mimic DR progression and used streptozotocin-injected rats (4-8 weeks) for an in vivo diabetes model. HREC/RPE viability decreased after 24 h incubation and diminished further over 6 days, and Hoechst staining revealed hyperglycemia-induced HREC/RPE apoptosis. Although miR-124/-125b expression decreased with DR progression in vitro and in vivo, miR-135b/-199a levels decreased in retinal cells under hyperglycemia exposure, but increased in diabetic retinas. Moreover, miR-145/-146a expression decreased gradually in high-glucose-treated HRECs, but increased in hyperglycemia-exposed RPE cells and in diabetic rats. Our findings suggested that aberrant miRNA expression could be involved in hyperglycemia-induced retinal-cell dysfunction, and the identified miRNAs might vary in different retinal layers, with expression changes associated with DR development. Therefore, miRNA modulation and the targeting of miRNA effects on transcription factors could represent novel and effective DR-treatment strategies.

miRNA-124 in Immune System and Immune Disorders

In recent years, miR-124 has emerged as a critical modulator of immunity and inflammation. Here, we summarize studies on the function and mechanism of miR-124 in the immune system and immunity-related diseases. They indicated that miR-124 exerts a crucial role in the development of immune system, regulation of immune responses, and inflammatory disorders. It is evident that miR-124 may serve as an informative diagnostic biomarker and therapeutic target in the future.

MiR-375 and miR-200c as predictive biomarkers of islet isolation and transplantation in total pancreatectomy with islet autotransplantation

BACKGROUND

Total pancreatectomy with islet autotransplantation (TPIAT) is a promising treatment for refractory chronic pancreatitis. Predictable biomarkers for the endocrine function after transplantation would be helpful in selecting patients for TPIAT. This study aims to identify novel biomarkers for predicting the outcome of islet isolation and transplantation in TPIAT patients.

METHODS

This paper studied microRNA of 31 TPIAT patients and 11 deceased donors from plasma samples before TPIAT. MiR-7, miR-200a, miR-200c, miR-320, and miR-375 were analyzed along with patient characteristics and the outcomes of islet isolation and transplantation via univariate and multivariate regression analysis.

RESULTS

MiR-375 before TPIAT showed a significant correlation with ∆C-peptide (r = -0.396, P = 0.03) and post-digestion islet count (r = -0.372, P = 0.04). And also miR-200c was significantly correlated with insulin requirement, C-peptide, and SUITO index at 1 year after transplantation. Moreover it was confirmed that miR-200c was a predictable factor of endocrine outcome in multi regression analysis (coefficient = -7.081, P = 0.001).

CONCLUSIONS

We concluded that miR-375 and miR-200c could potentially serve as novel biomarkers in predicting the islet yield in islet isolation and the metabolic function after transplantation for chronic pancreatitis patients.

Molecular Markers of Diabetic Retinopathy: Potential Screening Tool of the Future?

Diabetic retinopathy (DR) is among the leading causes of new onset blindness in adults. Effective treatment may delay the onset and progression of this disease provided it is diagnosed early. At present retinopathy can only be diagnosed via formal examination of the eye by a trained specialist, which limits the population that can be effectively screened. An easily accessible, reliable screening biomarker of diabetic retinopathy would be of tremendous benefit in detecting the population in need of further assessment and treatment. This review highlights specific biomarkers that show promise as screening markers to detect early diabetic retinopathy or even to detect patients at increased risk of DR at the time of diagnosis of diabetes. The pathobiology of DR is complex and multifactorial giving rise to a wide array of potential biomarkers. This review provides an overview of these pathways and looks at older markers such as advanced glycation end products (AGEs), inflammatory markers, vascular endothelial growth factor (VEGF) as well as other newer proteins with a role in the pathogenesis of DR including neuroprotective factors such as brain derived neurotrophic factor (BDNF) and Pigment Epithelium Derived Factor (PEDF); SA100A12, pentraxin 3, brain natriuretic peptide, apelin 3, and chemerin as well as various metabolites such as lipoprotein A, folate, and homocysteine. We also consider the possible role of proteins identified through proteomics work whose levels are altered in the sera of patients with DR as screening markers though their role in pathophysiology remains to be characterized. The role of microRNA as a promising new screening marker is also discussed.

Direct visualization of sub-femtomolar circulating microRNAs in serum based on the duplex-specific nuclease-amplified oriented assembly of gold nanoparticle dimers

The combination of DSNSA and oriented assembly of AuNPs was used for direct visualization of sub-femtomolar circulating microRNAs in serum.