glucagon-like-peptide-1 and Diabetic-Retinopathy

Glucagon-like peptide1-receptor agonists (GLP1-RA) decrease major adverse cardiovascular events (MACE) in people with type 2 diabetes mellitus and cardiovascular disease (CVD). Caution is recommended for semaglutide and dulaglutide with risk of exacerbating diabetic retinopathy (DR). Analyses were performed to determine if worsening of DR was dependent on drug class or fall in A1c.. Meta-analyses and meta-regressions (MR) were performed on the 7 major cardiovascular outcome trial (CVOTs) (n = 56004 patients) of GLP1-RA. A second analysis of 11 studies (n = 11894 subjects) with semaglutide documenting DR followed.. Six of the CVOTs evaluated DR. For the GLP1-RA class, there was no increase in the relative rate (rr) for retinopathy (rr = 1.09,95%CI; 0.925,1.289, p = 0.30), with only an increase with parenteral semaglutide (rr = 1.73; 1.10:2.71, p = 0.02). MR showed that decreases in A1c correlated with decreases in MACE (log rr = 0.364∗(Δ A1c), p = 0.014), but increases in DR (log rr= (-0.67∗(ΔA1c), p = 0.076). The change in DR was predominantly found for subcutaneous semaglutide given for >1 year (rr = 1.559,1.068,2.276, p = 0.022) and with decreases in A1c > 1.0% (rr = 1.59; 1.092,2.316, p = 0.016). For the class of GLP1-RA, the rate difference (rd) for worsening retinopathy was = 0.001 (and number needed to harm [NNH] = 1000) compared with rd for MACE = -0.013 (number needed to treat [NNT] = 77). The computation for semaglutide was NNH = 77 and NNT = 43.. This meta-analysis may assist in decisions balancing the relative risk (of existing retinopathy) versus benefits (to existing CVD). There should be close collaboration with ophthalmology to grade the baseline degree of retinopathy when initiating and following patients.

Topics: Cardiovascular Diseases; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Glycated Hemoglobin; Humans; Hypoglycemic Agents

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) exhibit glucose-lowering, weight-reducing, and blood pressure-lowering effects. Nevertheless, a debate exists concerning the association between GLP-1RA treatment and the risk of diabetic retinopathy (DR) in patients diagnosed with type 2 diabetes mellitus (T2DM).. To ascertain the risk of DR in patients with T2DM undergoing GLP-1RA treatment, we conducted a meta-analysis utilizing data derived from randomized placebo-controlled studies (RCTs).. A comprehensive literature search was conducted using PubMed, Cochrane Library, Web of Science, and EMBASE. We focused on RCTs involving the use of GLP-1RAs in patients with T2DM. Utilizing R software, we compared the risk of DR among T2DM patients undergoing GLP-1RA treatment. The Cochrane risk of bias method was employed to assess the research quality.. The meta-analysis incorporated data from 20 RCTs, encompassing a total of 24,832 T2DM patients. Across all included trials, randomization to GLP-1 RA treatment did not demonstrate an increased risk of DR (odds ratio = 1.17; 95% CI 0.98-1.39). Furthermore, no significant heterogeneity or publication bias was detected in the analysis.. The results of this systematic review and meta-analysis indicate that the administration of GLP-1 RA is not associated with an increased risk of DR. PROSPERO REGISTRATION IDENTIFIER: CRD42023413199.

Topics: Diabetes Mellitus, Type 2; Diabetic Retinopathy; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Glucagon-Like Peptide-1 Receptor Agonists; Humans; Hypoglycemic Agents; Randomized Controlled Trials as Topic

For a long time, diabetic retinopathy (DR) has been one of the most severe complications of diabetes. The early treatment of DR is not clearly recognized. The additional benefit of hypoglycemic agents for DR has become a new research field. Glucagon-like peptide-1 receptor (GLP-1R) has been shown to be widely expressed in tissues including retina. Glucagon-like peptide-1 receptor agonists (GLP-1RA) have been generally used in the treatment of diabetic patients. Studies shows that GLP-1RA could inhibit nerve damage by decrease apoptosis of nerve cells and activation of glial cells. In addition, GLP-1RA plays a protective role for tight junction (TJ) and cells of blood retinal barrier (BRB). It also protects retina from BRB damage. In this review, we discuss the potential protective mechanisms of GLP-1RA for DR beyond the hypoglycemic effects.

Topics: Apoptosis; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Humans; Nerve Degeneration; Retina

Type 2 diabetes is now a pandemic and shows no signs of abatement. In this Seminar we review the pathophysiology of this disorder, with particular attention to epidemiology, genetics, epigenetics, and molecular cell biology. Evidence is emerging that a substantial part of diabetes susceptibility is acquired early in life, probably owing to fetal or neonatal programming via epigenetic phenomena. Maternal and early childhood health might, therefore, be crucial to the development of effective prevention strategies. Diabetes develops because of inadequate islet β-cell and adipose-tissue responses to chronic fuel excess, which results in so-called nutrient spillover, insulin resistance, and metabolic stress. The latter damages multiple organs. Insulin resistance, while forcing β cells to work harder, might also have an important defensive role against nutrient-related toxic effects in tissues such as the heart. Reversal of overnutrition, healing of the β cells, and lessening of adipose tissue defects should be treatment priorities.

Topics: Adipose Tissue; Animals; Blood Glucose; Diabetes Mellitus, Type 2; Diabetes, Gestational; Diabetic Retinopathy; Epigenesis, Genetic; Female; Fetal Development; Genetic Predisposition to Disease; Glucagon; Glucagon-Like Peptide 1; Homeostasis; Humans; Incretins; Insulin Resistance; Insulin-Secreting Cells; Life Style; Liver; Muscle, Skeletal; Myocardium; Obesity; Prediabetic State; Pregnancy

Accelerated atherosclerosis and microvascular complications are the leading causes of coronary heart disease, end-stage renal failure, acquired blindness and a variety of neuropathies, which could account for disabilities and high mortality rates in patients with diabetes. Glucagon-like peptide-1 (GLP-1) belongs to the incretin hormone family. L cells in the small intestine secrete GLP-1 in response to food intake. GLP-1 not only enhances glucose-evoked insulin release from pancreatic β-cells, but also suppresses glucagon secretion from pancreatic α-cells. In addition, GLP-1 slows gastric emptying. Therefore, enhancement of GLP-1 secretion is a potential therapeutic target for the treatment of type 2 diabetes. Dipeptidyl peptidase-4 (DPP-4) is a responsible enzyme that mainly degrades GLP-1, and the half-life of circulating GLP-1 is very short. Recently, DPP-4 inhibitors and DPP-4-resistant GLP-1 receptor (GLP-1R) agonists have been developed and clinically used for the treatment of type 2 diabetes as a GLP-1-based medicine. GLP-1R is shown to exist in extra-pancreatic tissues such as vessels, kidney and heart, and could mediate the diverse biological actions of GLP-1 in a variety of tissues. So, in this paper, we review the pleiotropic effects of GLP-1-based therapies and its clinical utility in vascular complications in diabetes.

Topics: Animals; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Diabetic Nephropathies; Diabetic Neuropathies; Diabetic Retinopathy; Dipeptidyl Peptidase 4; Dipeptidyl-Peptidase IV Inhibitors; Glucagon; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Humans; Insulin; Insulin Secretion; Insulin-Secreting Cells; Receptors, Glucagon

Hyperglycemia is the major risk factor for microvascular complications in type 2 diabetes mellitus (T2DM) patients. This randomized controlled clinical trial aimed to investigate T2DM patients with microvascular complications with regard to possible relations among serum clusterin (CLU), amylin, secreted frizzled-related protein-4 (SFRP-4), glucagon-like peptide-1 (GLP-1) and dipeptidyl peptidase-4 (DPP-4) activities.. Subject groups were defined as follows: T2DM without complications (n=25, F/M=9/16, age 53.9±11.1 years); T2DM+Retinopathy (n=25, F/M=13/12, age 63.8±7.1 years); T2DM+Nephropathy (n=25, F/M=13/12, age 58.7±14.4 years); T2DM+Neuropathy (n=25, F/M=15/10, age 63.2±9.6 years); and healthy control subjects (HC) (n=25). CLU, amylin, SFRP-4, DPP-4 and GLP-1 (total and active) activities were measured and compared in blood samples from type 2 diabetic patients with and without microvascular complications.. Significantly lower levels of DPP-4 and GLP-1total (P.

Topics: Adult; Aged; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Diabetic Retinopathy; Dipeptidyl Peptidase 4; Female; Glucagon-Like Peptide 1; Humans; Hyperglycemia; Male; Middle Aged

Regulatory guidance specifies the need to establish cardiovascular safety of new diabetes therapies in patients with type 2 diabetes in order to rule out excess cardiovascular risk. The cardiovascular effects of semaglutide, a glucagon-like peptide 1 analogue with an extended half-life of approximately 1 week, in type 2 diabetes are unknown.. We randomly assigned 3297 patients with type 2 diabetes who were on a standard-care regimen to receive once-weekly semaglutide (0.5 mg or 1.0 mg) or placebo for 104 weeks. The primary composite outcome was the first occurrence of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. We hypothesized that semaglutide would be noninferior to placebo for the primary outcome. The noninferiority margin was 1.8 for the upper boundary of the 95% confidence interval of the hazard ratio.. At baseline, 2735 of the patients (83.0%) had established cardiovascular disease, chronic kidney disease, or both. The primary outcome occurred in 108 of 1648 patients (6.6%) in the semaglutide group and in 146 of 1649 patients (8.9%) in the placebo group (hazard ratio, 0.74; 95% confidence interval [CI], 0.58 to 0.95; P<0.001 for noninferiority). Nonfatal myocardial infarction occurred in 2.9% of the patients receiving semaglutide and in 3.9% of those receiving placebo (hazard ratio, 0.74; 95% CI, 0.51 to 1.08; P=0.12); nonfatal stroke occurred in 1.6% and 2.7%, respectively (hazard ratio, 0.61; 95% CI, 0.38 to 0.99; P=0.04). Rates of death from cardiovascular causes were similar in the two groups. Rates of new or worsening nephropathy were lower in the semaglutide group, but rates of retinopathy complications (vitreous hemorrhage, blindness, or conditions requiring treatment with an intravitreal agent or photocoagulation) were significantly higher (hazard ratio, 1.76; 95% CI, 1.11 to 2.78; P=0.02). Fewer serious adverse events occurred in the semaglutide group, although more patients discontinued treatment because of adverse events, mainly gastrointestinal.. In patients with type 2 diabetes who were at high cardiovascular risk, the rate of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke was significantly lower among patients receiving semaglutide than among those receiving placebo, an outcome that confirmed the noninferiority of semaglutide. (Funded by Novo Nordisk; SUSTAIN-6 ClinicalTrials.gov number, NCT01720446 .).

Topics: Aged; Cardiovascular Diseases; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Diabetic Retinopathy; Female; Gastrointestinal Diseases; Glucagon-Like Peptide 1; Glucagon-Like Peptides; Glycated Hemoglobin; Humans; Kaplan-Meier Estimate; Male; Middle Aged

The ability of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) to decrease certain microvascular events has called for the investigation of GLP-1 RAs against diabetic retinopathy (DR), but the evidence is limited. By combining data from observational and Mendelian randomization (MR) studies, we aimed to investigate whether GLP-1 RAs decrease the risk of DR.. We combined data from several Swedish Registers and identified patients with incident type 2 diabetes being treated with GLP-1 RAs between 2006 and 2015, and matched them to diabetic patients who did not use GLP-1 RAs as the comparisons. The Cox proportional hazards models were applied to assess the risk of DR. We further performed the summary-data-based MR (SMR) analyses based on the Genotype-Tissue Expression databases and the Genome-Wide Association Study of DR from the FinnGen consortium.. A total of 2390 diabetic patients were treated with GLP-1 RAs and the incidence of DR was 5.97 per 1000 person-years. Compared with diabetic patients who did not use GLP-1 RAs having an incidence of 12.85 per 1000 person-years, the adjusted hazard ratio (HR) of DR was 0.42 [95% confidence interval (CI), 0.29-0.61]. Genetically-predicted GLP1R expression (the target of GLP-1 RAs) showed an inverse association with background [odds ratio (OR)=0.83, 95% CI, 0.71-0.97] and severe nonproliferative DR (OR=0.72, 95% CI, 0.53-0.98), and a non-significant association with overall (OR=0.97, 95% CI, 0.92-1.03) and proliferative DR (OR=0.98, 95% CI, 0.91-1.05).. Both observational and mendelian randomization analyses showed a significantly lower risk of DR for patients treated with GLP-1 RAs, which calls for further studies to validate these findings.

Topics: Diabetes Mellitus, Type 2; Diabetic Retinopathy; Genome-Wide Association Study; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Humans; Hypoglycemic Agents; Mendelian Randomization Analysis

To compare risk of diabetic retinopathy (DR) between patients taking sodium-glucose cotransporter-2 inhibitors (SGLT2is) and those taking glucagon-like peptide-1 receptor agonists (GLP1-RAs) in routine care.. This retrospective cohort study emulating a target trial included patient data from the multi-institutional Chang Gung Research Database in Taiwan. Totally, 33,021 patients with type 2 diabetes mellitus using SGLT2is and GLP1-RAs between 2016 and 2019 were identified. 3,249 patients were excluded due to missing demographics, age <40 years, prior use of any study drug, a diagnosis of retinal disorders, a history of receiving vitreoretinal procedure, no baseline glycosylated hemoglobin, or no follow-up data. Baseline characteristics were balanced using inverse probability of treatment weighting with propensity scores. DR diagnoses and vitreoretinal interventions served as the primary outcomes. Occurrence of proliferative DR and DR receiving vitreoretinal interventions were regarded as vision-threatening DR.. There were 21,491 SGLT2i and 1,887 GLP1-RA users included for the analysis. Patients receiving SGLT2is and GLP-1 RAs exhibited comparable rate of any DR (subdistribution hazard ratio [SHR], 0.90; 95% confidence interval [CI], 0.79 to 1.03), whereas the rate of proliferative DR (SHR, 0.53; 95% CI, 0.42 to 0.68) was significantly lower in the SGLT2i group. Also, SGLT2i users showed significantly reduced risk of composite surgical outcome (SHR, 0.58; 95% CI, 0.48 to 0.70).. Compared to those taking GLP1-RAs, patients receiving SGLT2is had a lower risk of proliferative DR and vitreoretinal interventions, although the rate of any DR was comparable between the SGLT2i and GLP1-RA groups. Thus, SGLT2is may be associated with a lower risk of vision-threatening DR but not DR development.

Topics: Adult; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Glucose; Humans; Hypoglycemic Agents; Retrospective Studies; Sodium; Sodium-Glucose Transporter 2 Inhibitors

Newer hypoglycemics such as dipeptidyl peptidase 4 (DPP-4) inhibitors, sodium-glucose cotransporter-2 (SGLT-2) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists have been increasingly used in diabetes. This study aimed to assess the relationship between usage of these hypoglycemic agents and effect on diabetic retinopathy (DR).. Using the Vestrum Health Retina Database, patients with DR with 1 year follow-up after use of a hypoglycemic agent were included and stratified by agent, including no pharmacotherapy.. Of 60,649 eyes, in 1 year after hypoglycemic agent usage, progression rates from severe nonproliferative diabetic retinopathy (NPDR) to proliferative diabetic retinopathy (PDR) were the following: DPP-4 (17%), SGLT-2 (12%), GLP-1 (21%), metformin (18%), and none (20%). Progression rates from moderate NPDR to severe NPDR or PDR were the following: DPP-4 (11%), SGLT-2 (10%), GLP-1 (11%), metformin (10%), none (13%). Progression rates from mild NPDR to moderate/severe NPDR or PDR were the following: DPP-4 (6%), SGLT-2 (9%), GLP-1 (9%), metformin (7%), and none (10%).. Within a large real-world database, patients prescribed GLP-1 agonists were found to have DR progression rates comparable to those of patients receiving no hypoglycemic agents.

Topics: Diabetes Mellitus, Type 2; Diabetic Retinopathy; Dipeptidyl-Peptidase IV Inhibitors; Glucagon-Like Peptide 1; Humans; Hypoglycemic Agents; Metformin

GLP-1 receptor agonists (GLP-1RA) are common clinical agents that are clinically protective against diabetic complications, such as diabetic retinopathy (DR). Previous studies have shown that the RhoA/ROCK pathway plays an important role in the development of DR. However, the specific mechanism of action between GLP-1RA and DR remains unclear. The aim of this study was thus to investigate the main mechanism involved in the protective effect of GLP-1RA on DR.. Type 2 diabetic mice were fed a high-sugar, high-fat diet. Changes in the retinal structure were observed via HE staining and transmission electron microscopy. The expression of retinal GLP-1R, blood-retinal barrier- (BRB-) related proteins, inflammatory factors, and related pathway proteins were studied via Western blot or immunohistochemistry/immunofluorescence analysis.. GLP-1RA treatment reduced the blood glucose and lipid levels as well as the body weight of the diabetic mice while also improving retinal thickness, morphology, and vascular ultrastructure. Moreover, restored GLP-1R expression, increased Occludin and ZO-1 levels, and decreased albumin expression led to reduced retinal leakage and improved the BRB by inhibiting the RhoA/ROCK pathway.. We found that the protective effect of GLP-1RA on the retina may be realized through the GLP-1R-ROCK-p-MLC signaling pathway.

Topics: Animals; Blood-Retinal Barrier; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Mice; Signal Transduction; Transcription Factors

Retinal pericyte migration represents a novel mechanism of pericyte loss in diabetic retinopathy (DR), which plays a crucial role in the early impairment of the blood-retinal barrier (BRB). Glucagon-like peptide-1 (GLP-1) has been shown to protect the diabetic retina in the early stage of DR; however, the relationship between GLP-1 and retinal pericytes has not been discussed. In this study, advanced glycation end products (AGEs) significantly increased the migration of primary bovine retinal pericytes without influencing cell viability. AGEs also significantly enhanced phosphatidylinositol 3-kinase (PI3K)/Akt activation, and changed the expressions of migration-related proteins, including phosphorylated focal adhesion kinase (p-FAK), matrix metalloproteinase (MMP)-2 and vinculin. PI3K inhibition significantly attenuated the AGEs-induced migration of retinal pericytes and reversed the overexpression of MMP-2. Glucagon-like peptide-1 receptor (Glp1r) was expressed in retinal pericytes, and liraglutide, a GLP-1 analog, significantly attenuated the migration of pericytes by Glp1r and reversed the changes in p-Akt/Akt, p-FAK/FAK, vinculin and MMP-2 levels induced by AGEs, indicating that the protective effect of liraglutide was associated with the PI3K/Akt pathway. These results provided new insights into the mechanism underlying retinal pericyte migration. The early use of liraglutide exerts a potential bebefical effect on regulating pericyte migration, which might contribute to mechanisms that maintain the integrity of vascular barrier and delay the development of DR.

Topics: Animals; Apoptosis; Blood-Retinal Barrier; Cattle; Cell Movement; Cell Survival; Diabetic Retinopathy; Focal Adhesion Kinase 1; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Glycation End Products, Advanced; Humans; Liraglutide; Matrix Metalloproteinase 2; Pericytes; Retina

Linagliptin has protective effects on the retinal neurovascular unit but, in proliferative retinopathy, dipeptidyl peptidase 4 (DPP-4) inhibition could be detrimental. The aim of this study was to assess the effect of linagliptin on ischaemia-induced neovascularisation of the retina.. Systemic treatment with linagliptin demonstrated GLP-1R-independent anti-angiogenic effects mediated by an inhibition of VEGF receptor downstream signalling. The specific effects of linagliptin on diabetic retinopathy are of potential benefit for individuals with diabetes, independent of metabolic effects.

Topics: Animals; Diabetic Retinopathy; Dipeptidyl-Peptidase IV Inhibitors; Disease Models, Animal; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Human Umbilical Vein Endothelial Cells; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Linagliptin; Male; Mice; Mice, Inbred C57BL; Oxygen; Retina; Retinal Neovascularization; Signal Transduction; Vascular Endothelial Growth Factor A

Retinal neurodegeneration is an early event in the pathogenesis of diabetic retinopathy (DR). Since glucagon-like peptide 1 (GLP-1) exerts neuroprotective effects in the central nervous system and the retina is ontogenically a brain-derived tissue, the aims of the current study were as follows: 1) to examine the expression and content of GLP-1 receptor (GLP-1R) in human and db/db mice retinas; 2) to determine the retinal neuroprotective effects of systemic and topical administration (eye drops) of GLP-1R agonists in db/db mice; and 3) to examine the underlying neuroprotective mechanisms. We have found abundant expression of GLP-1R in the human retina and retinas from db/db mice. Moreover, we have demonstrated that systemic administration of a GLP-1R agonist (liraglutide) prevents retinal neurodegeneration (glial activation, neural apoptosis, and electroretinographical abnormalities). This effect can be attributed to a significant reduction of extracellular glutamate and an increase of prosurvival signaling pathways. We have found a similar neuroprotective effect using topical administration of native GLP-1 and several GLP-1R agonists (liraglutide, lixisenatide, and exenatide). Notably, this neuroprotective action was observed without any reduction in blood glucose levels. These results suggest that GLP-1R activation itself prevents retinal neurodegeneration. Our results should open up a new approach in the treatment of the early stages of DR.

Topics: Administration, Ophthalmic; Aged; Animals; Apoptosis; Blotting, Western; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Electroretinography; Exenatide; Female; Glial Fibrillary Acidic Protein; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Humans; Immunohistochemistry; Liraglutide; Male; Mice; Middle Aged; Neuroprotective Agents; Peptides; Real-Time Polymerase Chain Reaction; Retina; Retinal Neurons; Venoms

This study was aimed to further investigate the possible mechanisms by which the glucagon like peptide 1 analogue, exendin-4 (EX4), protects rat retinal cells at the early stage of diabetes. EX4 was injected intravitreally into normal and early-stage streptozotocin-diabetic rats. Cell death, reactive oxygen species (ROS), and electroretinogram (ERG) were measured. Sirtuin (Sirt) mRNA and protein were analyzed. In retinas of diabetic rats 1 month after diabetes onset, cell death and ROS level increased significantly, and the b-wave amplitudes and OPs were significantly reduced. Four days after intravitreal EX4 treatment, retinal cell death and ROS level in retinas reduced significantly, and visual function was recovered. In the retinas of early-stage diabetic rats, the expressions of Sirt1 and Sirt3 were also found to be significantly decreased, and both were back to normal levels after intravitreal injection of EX4. In R28 cells, hydrogen peroxide (H2O2) treatment increased ROS and cell death and decreased Sirt1 and Sirt3. With the addition of EX4 into the culture system, the expressions of Sirt1 and Sirt3 were increased, and the H2O2-induced ROS and cell death were significantly reduced. These results confirm a mechanism for EX4 to protect retinal cells from diabetic damage and oxidative injury. EX4 reduces retinal cell death and ROS generation by upregulating Sirt1 and Sirt3 expressions in the retina of early-stage diabetic rats as well as in H2O2-treated R28 cells.

Topics: Animals; Cell Death; Cells, Cultured; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Electroretinography; Exenatide; Gene Expression Regulation; Glucagon-Like Peptide 1; Hypoglycemic Agents; Immunoblotting; In Situ Nick-End Labeling; Male; Oxidative Stress; Peptides; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Retinal Ganglion Cells; RNA, Messenger; Sirtuin 1; Sirtuins; Time Factors; Venoms

Dipeptidyl peptidase 4 (DPP4) inhibitors improve glycemic control in type 2 diabetes, however, their influence on the retinal neurovascular unit remains unclear.. Vasculo- and neuroprotective effects were assessed in experimental diabetic retinopathy and high glucose-cultivated C. elegans, respectively. In STZ-diabetic Wistar rats (diabetes duration of 24 weeks), DPP4 activity (fluorometric assay), GLP-1 (ELISA), methylglyoxal (LC-MS/MS), acellular capillaries and pericytes (quantitative retinal morphometry), SDF-1a and heme oxygenase-1 (ELISA), HMGB-1, Iba1 and Thy1.1 (immunohistochemistry), nuclei in the ganglion cell layer, GFAP (western blot), and IL-1beta, Icam1, Cxcr4, catalase and beta-actin (quantitative RT-PCR) were determined. In C. elegans, neuronal function was determined using worm tracking software.. Linagliptin decreased DPP4 activity by 77% and resulted in an 11.5-fold increase in active GLP-1. Blood glucose and HbA1c were reduced by 13% and 14% and retinal methylglyoxal by 66%. The increase in acellular capillaries was diminished by 70% and linagliptin prevented the loss of pericytes and retinal ganglion cells. The rise in Iba-1 positive microglia was reduced by 73% with linagliptin. In addition, the increase in retinal Il1b expression was decreased by 65%. As a functional correlate, impairment of motility (body bending frequency) was significantly prevented in C. elegans.. Our data suggest that linagliptin has a protective effect on the microvasculature of the diabetic retina, most likely due to a combination of neuroprotective and antioxidative effects of linagliptin on the neurovascular unit.

Topics: Animals; Blood Glucose; Caenorhabditis elegans; Diabetic Retinopathy; Dipeptidyl Peptidase 4; Dipeptidyl-Peptidase IV Inhibitors; Glucagon-Like Peptide 1; Hypoglycemic Agents; Linagliptin; Male; Pericytes; Pyruvaldehyde; Rats; Rats, Wistar; Retinal Ganglion Cells

Rapid improvement in glycaemic control with GLP-1 receptor agonist (RA) therapy has been reported to be associated with significant progression of diabetic retinopathy. This deterioration is transient, and continuing GLP-1 RA treatment is associated with reversal of this phenomenon. Pre-existent maculopathy, higher grade of retinopathy and longer duration of diabetes may be risk factors for persistent deterioration.

Topics: Blood Glucose; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Disease Progression; Exenatide; Follow-Up Studies; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Glycated Hemoglobin; Humans; Hypoglycemic Agents; Middle Aged; Peptides; Receptors, Glucagon; Risk Factors; Venoms

To evaluate the protective effect of intravitreal injection of exendin-4 analogue (E4a) in early diabetic retinopathy (DR) and to explore its possible mechanism.. Forty Sprague-Dawley rats were divided into three groups: normal (N), diabetic (D), and E4a-treated diabetic rats (E4a). Diabetes was induced by streptozotocin. Rats in the E4a group were treated with E4a (0.1 μg/2μL/eye), whereas the N and D groups were treated with the equivalent volume of normal saline. Electroretinography was performed at 1 month and 3 months after diabetes onset. Thicknesses and cell counts in each layer of the retina were evaluated. The concentration of glutamate was measured by high-performance liquid chromatography (HPLC). Expressions of glucagon-like peptide-1 receptor (GLP-1R) and GLAST (excitatory amino acid transporter) were detected at mRNA and protein levels and verified by immunohistochemistry in vitro and in vivo. The rMc-1 cells were cultured under high-glucose medium (25 mM), which mimicked diabetic conditions. Effects of E4a (10 μg/mL) were also tested in the rMc-1 culture system.. E4a prevented the reduction in b-wave amplitude and oscillatory potential amplitude caused by diabetes. It also prevented the cell loss of outer nuclear layer and inner nuclear layer; the thickness and cell count in the outer nuclear layer were decreased in 1-month diabetic rats. The concentration of glutamate in the retina was higher in diabetic rats and was significantly reduced in the E4a-treated group. Consistent with such changes, retinal GLP-1R and GLAST expression were reduced in the diabetic retina but upregulated in E4a-treated rats. No improvement was found in the retina in both functional and morphologic parameters 3 months after treatment.. Intravitreal administration of E4a can prevent the retina, functionally and morphologically, from the insults of diabetes in rats. GLP-1R and GLAST were proved to exist in the rat retina, and their lowered expressions in the diabetic retina might be related to retinal damage by increasing the retinal glutamate. E4a might protect the retina by reducing the glutamate level through upregulating GLP-1R and GLAST, as observed in retinal Müller cells in this study, but this protective effect was transient. Thus, this could be a potential approach for the treatment of DR.

Topics: Animals; Blotting, Western; Cell Count; Cells, Cultured; Chromatography, High Pressure Liquid; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Electroretinography; Excitatory Amino Acid Transporter 1; Exenatide; Fluorescent Antibody Technique, Indirect; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Glutamic Acid; Hypoglycemic Agents; Intravitreal Injections; Male; Microscopy, Fluorescence; Peptides; Rats; Rats, Sprague-Dawley; Receptors, Glucagon; Retina; RNA, Messenger; Venoms

Rapid improvement in glycaemic control induced by GLP-1 agonist therapy could be yet another illustration of transient or permanent progression of diabetic retinopathy, similar to documented examples such as pregnancy and continuous subcutaneous insulin infusion. Specific guidelines would be needed to monitor this paradoxical phenomenon during treatment with GLP-1 agonists.

Topics: Adult; Aged; Diabetes Complications; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Female; Glucagon-Like Peptide 1; Humans; Insulin Infusion Systems; Male; Mass Screening; Middle Aged; Pregnancy; Pregnancy in Diabetics; Prognosis; Retrospective Studies

Diabetic retinopathy (DR) is one of the leading causes of blindness, affecting over 90% of diabetics. Exendin-4 (E4) is a potent and long-acting agonist of the glucagon-like peptide-1 (GLP-1) receptor. GLP-1 is an insulinotropic gut peptide, which normalizes blood glucose level and is now being tested in clinical trials as a treatment for diabetes. The purpose of our study was to explore the protective effect of subcutaneous (sc.) exendin-4 analogue (E4a) on early DR.. Expression of GLP-1R was detected at both mRNA and protein levels and verified by immunohistochemistry. Thirty-six Sprague-Dawley (SD) rats were included in the experiment. Diabetes was induced by intraperitoneal injection (ip) of streptozotocin (STZ). The rats were divided into three groups: normal control (N), diabetic control (D) and E4a-treated diabetic (E4a) group. For the E4a group, the rats were treated with E4a (sc.0.05 microg/g BW/day); for the N and D groups, the rats were treated with normal saline (NS, sc). Blood glucose levels and body weight were measured weekly. Electroretinogram (ERG) was performed 1 and 3 months after diabetes onset. The retinal thickness and cell counts in each layer were evaluated under light microscopy after ERG examination.. GLP-1R was expressed at both mRNA and protein levels in the retina of SD rats. Immunostaining of the rat retina revealed that GLP-1R was predominantly expressed in the inner layer of the retina. E4a can reduce the blood glucose level of diabetic rats to the normal control level. B-wave amplitudes and OPs decreased with the progress of diabetes, and E4a prevents the loss of b-wave amplitude and OPs caused by diabetes. The retinal thickness was reduced in a diabetes-duration-dependent fashion. The cell counts of both ONL and INL were reduced accordingly in the diabetic rats. E4a prevented cell loss and maintained a normal thickness.. GLP-1R is expressed in rat retina. Apoptosis is an important constituent of retinal cell death in early DR. E4a administration can reverse the changes of ERG, prevent the retinal cell death and maintain normal retinal thickness in diabetic rats. Therefore, this is a potent approach for treatment of early DR.

Topics: Animals; Blood Glucose; Blotting, Western; Cell Count; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Electroretinography; Exenatide; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Hypoglycemic Agents; Immunoenzyme Techniques; Injections, Subcutaneous; Male; Peptides; Polymerase Chain Reaction; Rats; Rats, Sprague-Dawley; Receptors, Glucagon; Retina; Retinal Photoreceptor Cell Inner Segment; Retinal Photoreceptor Cell Outer Segment; RNA, Messenger; Venoms