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Background: Diabetic retinopathy (DR) is a leading cause of end-stage blindness globally and is arguably one of the most disabling complications of both Type 1 and Type 2 diabetes. Sodium Glucose Cotransporter-2 (SGLT2) inhibitors have now been successfully introduced to clinical medicine and exert multiple beneficial effects in diabetic patients. Given the broad therapeutic application of SGLT2 inhibitors, we hypothesised that SGLT2 inhibition may alleviate the progression of DR. Therefore, we aimed to compare the effectiveness of two clinically available SGLT2 inhibitors, Empagliflozin and Canagliflozin, on the progression of Retinopathy and DR using well-characterised mouse models, Kimba and Akimba, respectively. Methods: Empagliflozin, Canagliflozin (25 mg/kg/day) or vehicle was administered to 10-week-old mice via drinking water for 8-weeks. Urine glucose levels were measured to ascertain SGLT2 inhibition promoted glucose excretion. Weekly body weight and water intake measurements were obtained. After 8-weeks of treatment, body weight, daily water intake, fasting blood glucose levels were measured and eye tissue was harvested. The retinal vasculature was assessed using immunofluorescence. Results: Empagliflozin treated Akimba mice exhibited metabolic benefits suggested by healthy body weight gain and significantly reduced fasting blood glucose levels. Treatment with Empagliflozin reduced retinal vascular lesions in both Kimba and Akimba mice. Canagliflozin improved body weight gain, reduced blood glucose levels in Akimba mice, and reduced the development of retinal vascular lesions in Kimba mice. Conclusions: Our data demonstrates that Empagliflozin has future potential as a therapeutic for Retinopathy and DR and should now be considered for human trials.

Diabetic kidney disease (DKD) is a chronic disorder characterized by elevated urine albumin excretion, reduced glomerular filtration rate, or both. At present, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers are the standard care for the treatment of DKD, resulting in improved outcomes. However, alternative treatments may be required because although the standard treatments have been found to slow the progression of DKD, they have not been found to halt the disease. In the past decade, sodium glucose co-transporter 2 (SGLT2) inhibitors have been widely researched in the area of cardiovascular disease and diabetes and have been shown to improve cardiovascular outcomes. SGLT2 inhibitors including canagliflozin and dapagliflozin have been shown to slow the progression of kidney disease. There is currently an omission of literature where three SGLT2 inhibitors have been simultaneously compared in a rodent diabetic model. After diabetic Akimba mice were treated with SGLT2 inhibitors for 8 weeks, there was not only a beneficial impact on the pancreas, signified by an increase in the islet mass and increased plasma insulin levels, but also on the kidneys, signified by a reduction in average kidney to body weight ratio and improvement in renal histology. These findings suggest that SGLT2 inhibition promotes improvement in both pancreatic and kidney health. [ABSTRACT FROM AUTHOR]

Background: Diabetic retinopathy (DR) is a major cause of blindness globally. Sodium Glucose Cotransporter-2 (SGLT2) inhibitors have been demonstrated to exert cardiorenal protection in patients with diabetes. However, their potential beneficial effect on DR is less well studied. The aim of the present study was to determine the effects of the SGLT2 inhibition with Dapagliflozin (DAPA) on DR in well-characterised DR mouse models and controls. Methods: Dapagliflozin was administered to mice with and without diabetes for 8 weeks via their drinking water at 25 mg/kg/day. Urine glucose levels were measured weekly and their response to glucose was tested at week 7. After 8 weeks of treatment, eye tissue was harvested under terminal anaesthesia. The retinal vasculature and neural structure were assessed using immunofluorescence, immunohistochemistry and electron microscopy techniques. Results: Dapagliflozin treated DR mice exhibited metabolic benefits reflected by healthy body weight gain and pronounced glucose tolerance. Dapagliflozin reduced the development of retinal microvascular and neural abnormalities, increased the beneficial growth factor FGF21 (Fibroblast Growth Factor 21). We highlight for the first time that SGLT2 inhibition results in the upregulation of SGLT1 protein in the retina and that SGLT1 is significantly increased in the diabetic retina. Conclusions: Blockade of SGLT2 activity with DAPA may reduce retinal microvascular lesions in our novel DR mouse model. In conclusion, our data demonstrates the exciting future potential of SGLT1 and/or SGLT2 inhibition as a therapeutic for DR.

Diabetic kidney disease (DKD) is a chronic disorder characterized by elevated urine albumin excretion, reduced glomerular filtration rate, or both. At present, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers are the standard care for the treatment of DKD, resulting in improved outcomes. However, alternative treatments may be required because although the standard treatments have been found to slow the progression of DKD, they have not been found to halt the disease. In the past decade, sodium glucose co-transporter 2 (SGLT2) inhibitors have been widely researched in the area of cardiovascular disease and diabetes and have been shown to improve cardiovascular outcomes. SGLT2 inhibitors including canagliflozin and dapagliflozin have been shown to slow the progression of kidney disease. There is currently an omission of literature where three SGLT2 inhibitors have been simultaneously compared in a rodent diabetic model. After diabetic Akimba mice were treated with SGLT2 inhibitors for 8 weeks, there was not only a beneficial impact on the pancreas, signified by an increase in the islet mass and increased plasma insulin levels, but also on the kidneys, signified by a reduction in average kidney to body weight ratio and improvement in renal histology. These findings suggest that SGLT2 inhibition promotes improvement in both pancreatic and kidney health.

Diabetic retinopathy (DR) develops due to hyperglycemia and inflammation-induced vascular disruptions in the retina with connexin43 expression patterns in the disease still debated. Here, the effects of hyperglycemia and inflammation on connexin43 expression in vitro in a mouse model of DR and in human donor tissues were evaluated. Primary human retinal microvascular endothelial cells (hRMECs) were exposed to high glucose (HG; 25 mM) or pro-inflammatory cytokines IL-1β and TNF-α (10 ng/mL each) or both before assessing connexin43 expression. Additionally, connexin43, glial fibrillary acidic protein (GFAP), and plasmalemma vesicular associated protein (PLVAP) were labeled in wild-type (C57BL/6), Akita (diabetic), and Akimba (DR) mouse retinas. Finally, connexin43 and GFAP expression in donor retinas with confirmed DR was compared to age-matched controls. Co-application of HG and cytokines increased connexin43 expression in hRMECs in line with results seen in mice, with no significant difference in connexin43 or GFAP expression in Akita but higher expression in Akimba compared to wild-type mice. On PLVAP-positive vessels, connexin43 was higher in Akimba but unchanged in Akita compared to wild-type mice. Connexin43 expression appeared higher in donor retinas with confirmed DR compared to age-matched controls, similar to the distribution seen in Akimba mice and correlating with the in vitro results. Although connexin43 expression seems reduced in diabetes, hyperglycemia and inflammation present in the pathology of DR seem to increase connexin43 expression, suggesting a causal role of connexin43 channels in the disease progression. [ABSTRACT FROM AUTHOR]

Background: Diabetic retinopathy (DR) is a leading cause of end-stage blindness globally and is arguably one of the most disabling complications of both Type 1 and Type 2 diabetes. Sodium Glucose Cotransporter-2 (SGLT2) inhibitors have now been successfully introduced to clinical medicine and exert multiple beneficial effects in diabetic patients. Given the broad therapeutic application of SGLT2 inhibitors, we hypothesised that SGLT2 inhibition may alleviate the progression of DR. Therefore, we aimed to compare the effectiveness of two clinically available SGLT2 inhibitors, Empagliflozin and Canagliflozin, on the progression of Retinopathy and DR using well-characterised mouse models, Kimba and Akimba, respectively., Methods: Empagliflozin, Canagliflozin (25 mg/kg/day) or vehicle was administered to 10-week-old mice via drinking water for 8-weeks. Urine glucose levels were measured to ascertain SGLT2 inhibition promoted glucose excretion. Weekly body weight and water intake measurements were obtained. After 8-weeks of treatment, body weight, daily water intake, fasting blood glucose levels were measured and eye tissue was harvested. The retinal vasculature was assessed using immunofluorescence., Results: Empagliflozin treated Akimba mice exhibited metabolic benefits suggested by healthy body weight gain and significantly reduced fasting blood glucose levels. Treatment with Empagliflozin reduced retinal vascular lesions in both Kimba and Akimba mice. Canagliflozin improved body weight gain, reduced blood glucose levels in Akimba mice, and reduced the development of retinal vascular lesions in Kimba mice., Conclusions: Our data demonstrates that Empagliflozin has future potential as a therapeutic for Retinopathy and DR and should now be considered for human trials., Competing Interests: MS has received research support from Boehringer Ingelheim. The other authors declare no conflicts of interests., (© 2023 The Author(s). Published by IMR Press.)

Diabetic retinopathy (DR) develops due to hyperglycemia and inflammation-induced vascular disruptions in the retina with connexin43 expression patterns in the disease still debated. Here, the effects of hyperglycemia and inflammation on connexin43 expression in vitro in a mouse model of DR and in human donor tissues were evaluated. Primary human retinal microvascular endothelial cells (hRMECs) were exposed to high glucose (HG; 25 mM) or pro-inflammatory cytokines IL-1β and TNF-α (10 ng/mL each) or both before assessing connexin43 expression. Additionally, connexin43, glial fibrillary acidic protein (GFAP), and plasmalemma vesicular associated protein (PLVAP) were labeled in wild-type (C57BL/6), Akita (diabetic), and Akimba (DR) mouse retinas. Finally, connexin43 and GFAP expression in donor retinas with confirmed DR was compared to age-matched controls. Co-application of HG and cytokines increased connexin43 expression in hRMECs in line with results seen in mice, with no significant difference in connexin43 or GFAP expression in Akita but higher expression in Akimba compared to wild-type mice. On PLVAP-positive vessels, connexin43 was higher in Akimba but unchanged in Akita compared to wild-type mice. Connexin43 expression appeared higher in donor retinas with confirmed DR compared to age-matched controls, similar to the distribution seen in Akimba mice and correlating with the in vitro results. Although connexin43 expression seems reduced in diabetes, hyperglycemia and inflammation present in the pathology of DR seem to increase connexin43 expression, suggesting a causal role of connexin43 channels in the disease progression.

As the prevalence of diabetes has reached epidemic proportions worldwide, diabetic retinopathy incidence is increasing rapidly. An advanced diabetic retinopathy (DR) stage can lead to a sight-threatening form. There is growing evidence showing diabetes causes a range of metabolic changes that subsequently lead to pathological modifications in the retina and retinal blood vessels. To understand the complex mechanism of the pathophysiology of DR, a precise model is not readily available. By crossbreeding the Akita and Kimba strains, a suitable proliferative DR model was acquired. This new Akimba strain manifests marked hyperglycemia and vascular changes, which resemble the early and advanced stage of DR.Here, we describe the breeding method, colony screening for experiments, and imaging techniques widely used to investigate the DR progression in this model. We elaborate step-by-step protocols to set up and perform fundus, fluorescein angiography, optical coherence tomography, and optical coherence tomography-angiogram to study retinal structural changes and vascular abnormalities. In addition, we show a method to label the leukocytes with fluorescence and laser speckle flowgraphy to examine the inflammation in the retina and retinal vessel blood flow speed, respectively. Lastly, we describe electroretinogram to evaluate the functional aspect of the DR transformations., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

The mouse retina is a commonly used animal model for the study of pathogenesis and treatment of blinding retinal vascular diseases such as diabetic retinopathy. In this study, we aimed to characterize normal and pathological variations in vascular anatomy in the mouse retina using fluorescein angiography visualized with scanning laser ophthalmoscopy and optical coherence tomography (SLO-OCT). We examined eyes from C57BL/6J wild type mice as well as the Ins2Akita and Akimba mouse models of diabetic retinopathy using the Heidelberg Retinal Angiography (HRA) and OCT system. Angiography was performed on three focal planes to examine distinct vascular layers. For comparison with angiographic data, ex vivo analyses, including Indian ink angiography, histology and 3D confocal scanning laser microscopy were performed in parallel. All layers of the mouse retinal vasculature could be readily visualized during fluorescein angiography by SLO-OCT. Blood vessel density was increased in the deep vascular plexus (DVP) compared with the superficial vascular plexus (SVP). Arteriolar and venular typologies were established and structural differences were observed between venular types. Unexpectedly, the hyaloid artery was found to persist in 15% of C57BL/6 mice, forming anastomoses with peripheral retinal capillaries. Fluorescein leakage was easily detected in Akimba retinae by angiography, but was not observed in Ins2Akita mice. Blood vessel density was increased in the DVP of 6 month old Ins2Akita mice, while the SVP displayed reduced branching in precapillary arterioles. In summary, we present the first comprehensive characterization of the mouse retinal vasculature by SLO-OCT fluorescein angiography. Using this clinical imaging technique, we report previously unrecognized variations in C57BL/6J vascular anatomy and novel features of vascular retinopathy in the Ins2Akita mouse model of diabetes. [ABSTRACT FROM AUTHOR]

Background: Diabetic retinopathy (DR) is a major cause of blindness globally. Sodium Glucose Cotransporter-2 (SGLT2) inhibitors have been demonstrated to exert cardiorenal protection in patients with diabetes. However, their potential beneficial effect on DR is less well studied. The aim of the present study was to determine the effects of the SGLT2 inhibition with Dapagliflozin (DAPA) on DR in well-characterised DR mouse models and controls., Methods: Dapagliflozin was administered to mice with and without diabetes for 8 weeks via their drinking water at 25 mg/kg/day. Urine glucose levels were measured weekly and their response to glucose was tested at week 7. After 8 weeks of treatment, eye tissue was harvested under terminal anaesthesia. The retinal vasculature and neural structure were assessed using immunofluorescence, immunohistochemistry and electron microscopy techniques., Results: Dapagliflozin treated DR mice exhibited metabolic benefits reflected by healthy body weight gain and pronounced glucose tolerance. Dapagliflozin reduced the development of retinal microvascular and neural abnormalities, increased the beneficial growth factor FGF21 (Fibroblast Growth Factor 21). We highlight for the first time that SGLT2 inhibition results in the upregulation of SGLT1 protein in the retina and that SGLT1 is significantly increased in the diabetic retina., Conclusions: Blockade of SGLT2 activity with DAPA may reduce retinal microvascular lesions in our novel DR mouse model. In conclusion, our data demonstrates the exciting future potential of SGLT1 and/or SGLT2 inhibition as a therapeutic for DR., Competing Interests: The authors declare no conflict of interest., (© 2022 The Author(s). Published by IMR Press.)

Abstract: The molecular mechanisms of vascular leakage in diabetic macular edema and proliferative retinopathy are poorly understood, mainly due to the lack of reliable in vivo models. The Akimba (Ins2AkitaVEGF+/−) mouse model combines retinal neovascularization with hyperglycemia, and in contrast to other models, displays the majority of signs of advanced clinical diabetic retinopathy (DR). To study the molecular mechanism that underlies the breakdown of the blood-retinal barrier (BRB) in diabetic macular edema and proliferative diabetic retinopathy, we investigated the retinal vasculature of Akimba and its parental mice Kimba (trVEGF029) and Akita (Ins2Akita). Quantitative PCR, immunohistochemistry and fluorescein angiography were used to characterize the retinal vasculature with special reference to the inner BRB. Correlations between the degree of fluorescein leakage and retinal gene expression were tested by calculating the Spearman's correlation coefficient. Fluorescein leakage demonstrating BRB loss was observed in Kimba and Akimba, but not in Akita or wild type mice. In Kimba and Akimba mice fluorescein leakage was associated with focal angiogenesis and correlated significantly with Plvap gene expression. PLVAP is an endothelial cell-specific protein that is absent in intact blood-retinal barrier, but its expression significantly increases in pathological conditions such as DR. Furthermore, in Akimba mice BRB disruption was linked to decreased expression of endothelial junction proteins, pericyte dropout and vessel loss. Despite fluorescein leakage, no alteration in BRB protein levels or pericyte coverage was detected in retinas of Kimba mice. In summary, our data not only demonstrate that hyperglycemia sensitizes retinal vasculature to the effects of VEGF, leading to more severe microvascular changes, but also confirm an important role of PLVAP in the regulation of BRB permeability. [Copyright &y& Elsevier]

Background: Type 1 diabetes (T1D) is associated with major chronic microvascular complications which contribute significantly to diabetes associated morbidity. The protein primarily responsible for glucose reabsorption in the kidney is sodium glucose co-transporter 2 (SGLT2). Presently, SGLT2 inhibitors are widely used in diabetic patients to improve blood glucose levels and prevent cardiovascular and renal complications. Given the broad therapeutic application of SGLT2 inhibitors, we hypothesised that SGLT2 inhibition may exert its protective effects via alterations of the gut microbiome and tested this in a type 1 diabetic mouse model of diabetic retinopathy., Aim: To determine whether the treatment with two independent SGLT2 inhibitors affects gut health in a type 1 diabetic mouse model., Methods: The SGLT2 inhibitors empagliflozin or dapagliflozin (25 mg/kg/d) or vehicle dimethylsulfoxide (DMSO) were administered to C57BL/6J, Akita, Kimba and Akimba mice at 10 wk of age for 8 wk via their drinking water. Serum samples were collected and the concentration of succinate and the short chain fatty acid (SCFA) butyric acid was measured using gas chromatography-mass spectrometry. Enzyme-linked immunosorbent assay (ELISA) was performed to determine the concentration of insulin and leptin. Furthermore, the norepinephrine content in kidney tissue was determined using ELISA. Pancreatic tissue was collected and stained with haematoxylin and eosin and analysed using brightfield microscopy., Results: Due to the presence of the Akita allele, both Akita and Akimba mice showed a reduction in insulin production compared to C57BL/6J and Kimba mice. Furthermore, Akita mice also showed the presence of apoptotic bodies within the pancreatic islets. The acinar cells of Akita and Akimba mice showed swelling which is indicative of acute injury or pancreatitis. After 8 wk of SGLT2 inhibition with dapagliflozin, the intermediate metabolite of gut metabolism known as succinate was significantly reduced in Akimba mice when compared to DMSO treated mice. In addition, empagliflozin resulted in suppression of succinate levels in Akimba mice. The beneficial SCFA known as butyric acid was significantly increased in Akita mice after treatment with dapagliflozin when compared to vehicle treated mice. The norepinephrine content in the kidney was significantly reduced with both dapagliflozin and empagliflozin therapy in Akita mice and was significantly reduced in Akimba mice treated with empagliflozin. In non-diabetic C57BL/6J and Kimba mice, serum leptin levels were significantly reduced after dapagliflozin therapy., Conclusion: The inhibition of SGLT2 reduces the intermediate metabolite succinate, increases SCFA butyric acid levels and reduces norepinephrine content in mouse models of T1D. Collectively, these improvements may represent an important mechanism underlying the potential benefits of SGLT2 inhibition in T1D and its complications., Competing Interests: Conflict-of-interest statement: Prof. Schlaich is supported by a National Health and Medical Research Council Research Fellowship and has received research support from Medtronic, Abbott, Novartis, Servier, Pfizer, and Boehringer Ingelheim. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. No potential conflicts of interest exist from other authors., (©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.)