Do SGLT2 inhibitors prevent preclinical diabetic retinopathy? A Prospective Pilot Optical Coherence Tomography Angiography Study

Investigating the impact of empagliflozin on the retina of diabetic mice

BACKGROUND

Diabetic retinopathy (DR) frequently results in compromised visual function, with hyperglycemia-induced disruption of the blood-retinal barrier (BRB) through various pathways as a critical mechanism. Existing DR treatments fail to address early and potentially reversible microvascular alterations. This study examined the effects of empagliflozin (EMPA), a selective Sodium-glucose transporter 2 (SGLT2) inhibitor, on the retina of db/db mice. The objective of this study is to investigate the potential role of EMPA in the prevention and delay of DR.

METHODS

db/db mice were randomly assigned to either the EMPA treatment group (db/db + Emp) or the model group (db/db), while C57 mice served as the normal control group (C57). Mice in the db/db + Emp group received EMPA for eight weeks. Body weight, fasting blood glucose (FBG), and blood VEGF were subsequently measured in all mice, along with the detection of specific inflammatory factors and BRB proteins in the retina. Retinal SGLT2 protein expression was compared using immunohistochemical analysis, and BRB structural changes were observed via electron microscopy.

RESULTS

EMPA reduced FBG, blood VEGF, and retinal inflammatory factors TNF-α, IL-6, and VEGF levels in the eye tissues of db/db mice. EMPA also increased Claudin-1, Occludin-1, and ZO-1 levels while decreasing ICAM-1 and Fibronectin, thereby preserving BRB function in db/db mice. Immunohistochemistry revealed that EMPA reduced SGLT2 expression in the retina of diabetic mice, and electron microscopy demonstrated that EMPA diminished tight junction damage between retinal vascular endothelial cells and prevented retinal vascular basement membrane thickening in diabetic mice.

CONCLUSION

EMPA mitigates inflammation and preserves BRB structure and function, suggesting that it may prevent DR or serve as an effective early treatment for DR.

Glucose transport, transporters and metabolism in diabetic retinopathy

Diabetic retinopathy (DR) is the most common reason for blindness in working-age individuals globally. Prolonged high blood glucose is a main causative factor for DR development, and glucose transport is prerequisite for the disturbances in DR caused by hyperglycemia. Glucose transport is mediated by its transporters, including the facilitated transporters (glucose transporter, GLUTs), the "active" glucose transporters (sodium-dependent glucose transporters, SGLTs), and the SLC50 family of uniporters (sugars will eventually be exported transporters, SWEETs). Glucose transport across the blood-retinal barrier (BRB) is crucial for nourishing the neuronal retina in the context of retinal physiology. This physiological process primarily relies on GLUTs and SGLTs, which mediate the glucose transportation across both the cell membrane of retinal capillary endothelial cells and the retinal pigment epithelium (RPE). Under diabetic conditions, increased accumulation of extracellular glucose enhances the retinal cellular glucose uptake and metabolism via both glycolysis and glycolytic side branches, which activates several biochemical pathways, including the protein kinase C (PKC), advanced glycation end-products (AGEs), polyol pathway and hexosamine biosynthetic pathway (HBP). These activated biochemical pathways further increase the production of reactive oxygen species (ROS), leading to oxidative stress and activation of Poly (ADP-ribose) polymerase (PARP). The activated PARP further affects all the cellular components in the retina, and finally resulting in microangiopathy, neurodegeneration and low-to-moderate grade inflammation in DR. This review aims to discuss the changes of glucose transport, glucose transporters, as well as its metabolism in DR, which influences the retinal neurovascular unit (NVU) and implies the possible therapeutic strategies for treating DR.

Evaluation of the effect of sodium-glucose cotransporter-2 inhibitor treatment on choroidal vascular parameters in patients with type 2 diabetes mellitus

BACKGROUND

To evaluate the effect of sodium-glucose cotransporter-2 inhibitor treatment on choroidal vascular parameters in patients with type 2 diabetes mellitus (T2DM).

METHODS

Twenty eyes of 20 patients with T2DM without diabetic retinopathy and 20 eyes of 20 age- and sex-matched patients as the control group were included in the study. The patients were evaluated using enhanced depth imaging optic coherence tomography before treatment and at the third month of treatment. The choroidal images were binarized into luminal areas (LAs) and stromal areas (SAs). The choroidal vascularity index (CVI) was defined as the ratio of the LA to the total circumscribed choroid area (TCA).

RESULTS

The mean age of the patients was 56.65±8.41 years. The patients' mean disease duration was 6.65±5.72 years, the mean HbA1c level was 8.89±1.62%, and the mean body mass index was 33.13±4.84 kg/m2. The subfoveal TCA, subfoveal LA, subfoveal SA, total TCA, total LA, and total SA values ​​of the patient group were found to be significantly lower than those of the control group (p = 0.006, p = 0.003, p = 0.028, p = 0.001, p = 0.001, and p = 0.006, respectively). There was a significant increase in the subfoveal TCA, subfoveal LA, subfoveal SA, subfoveal CVI, total TCA, total LA, and total SA values ​​after empagliflozin treatment compared to before empagliflozin treatment (p = 0.005, p = 0.003, p = 0.021, p = 0.032, p < 0.001, p < 0.001, and p = 0.001 respectively).

CONCLUSIONS

Empagliflozin provides an improvement in diabetic choroidal changes through its effect on choroidal vascularity parameters.

Mechanisms of Diabetic Nephropathy Not Mediated by Hyperglycemia

Diabetes mellitus (DM) is characterized by the appearance of progressive kidney damage, which may progress to end-stage kidney disease. The control of hyperglycemia is usually not sufficient to halt this progression. The kidney damage is quantitatively and qualitatively different in the two forms of diabetes; the typical nodular fibrosis (Kimmelstiel Wilson nodules) appears mostly in type 1 DM, whereas glomerulomegaly is primarily present in type 2 obese DM. An analysis of the different metabolites and hormones in type 1 and type 2 DM and their differential pharmacological treatments might be helpful to advance the hypotheses on the different histopathological patterns of the kidneys and their responses to sodium/glucose transporter type 2 inhibitors (SGLT2i).

The association between the use of sodium glucose cotransporter 2 inhibitor and the risk of diabetic retinopathy and other eye disorders: a systematic review and meta-analysis

OBJECTIVE

To assess the association between the use of sodium-glucose cotransporter 2 inhibitor (SGLT2i) and the incidence of diabetic retinopathy (DR).

RESEARCH DESIGN AND METHODS

Pubmed, Medline, Embase, the Cochrane Central Register of Controlled Trials and Clinicaltrial.gov were searched from inception to October 2021. Randomized controlled trials (RCTs) with reports of incidence of DR and other eye disorders between SGLT2i users and non-SGLT2i users with type 2 diabetes mellitus were included.

RESULTS

In general, the incidences of DR were comparable between SGLT2i users and non-SGLT2i users (OR=0.80, 95%CI 0.61 to 1.06, P=0.12). However, compared with non-SGLT2i users, the incidence of DR was significantly reduced in SGLT2i users with diabetes duration less than 10 years (OR=0.32, 95%CI 0.13 to 0.76, P=0.01). Weight reduction in SGLT2i users was associated with the decreased risk of retinal detachment. Moreover, longer study duration was associated with lower incidence of cataract and retinal vasculopathy in SGLT2i users.

CONCLUSIONS

In general, the use of SGLT2i was not associated with the incidence of DR. However, a reduced risk of DR was observed in SGLT2i users with diabetes duration less than 10 years. An early initiation of SGLT2i might be more likely to provide with ocular benefits.

Dapagliflozin protects neural and vascular dysfunction of the retina in diabetes

INTRODUCTION

Dapagliflozin, a sodium-glucose transporter inhibitor, effectively reduces blood glucose and is indicated for individuals with kidney diseases and cardiovascular disorders. In this study, we further expand the therapeutic benefit of dapagliflozin in the neural and vascular retina, with the potential to effectively manage diabetic retinopathy (DR), the most common complication of diabetes.

RESEARCH DESIGN AND METHODS

Db/db mice, an animal model of type 2 diabetes, were treated with dapagliflozin orally, and the electroretinogram (ERG) response and acellular capillary numbers were assessed. Messenger RNA levels of inflammatory cytokines were studied using real-time quantitative (q)PCR. We assessed endothelial cell migration in a scratch wound assay and retinal glucose uptake using human retinal endothelial cells.

RESULTS

The dapagliflozin treatment improved the ERG b-wave amplitude and decreased acellular capillary numbers. The scratch wound assay demonstrated a reduction in wound closure after dapagliflozin treatment. Retinal glucose uptake reduced after dapagliflozin treatment compared with the respective controls.

CONCLUSIONS

Our studies suggest that dapagliflozin treatment effectively corrects neural and vascular dysfunction of the retina in diabetes. This effect is mediated by a decrease in inflammation and improved glycemic control. In addition, dapagliflozin exhibits decreased wound healing and glucose uptake, which could benefit the retina. Thus, dapagliflozin could be helpful in the management of DR, with multimodal therapeutic effects.

Sodium Glucose Cotransporter-2 Inhibitors: Spotlight on Favorable Effects on Clinical Outcomes beyond Diabetes

Sodium glucose transporter type 2 (SGLT2) molecules are found in proximal tubules of the kidney, and perhaps in the brain or intestine, but rarely in any other tissue. However, their inhibitors, intended to improve diabetes compensation, have many more beneficial effects. They improve kidney and cardiovascular outcomes and decrease mortality. These benefits are not limited to diabetics but were also found in non-diabetic individuals. The pathophysiological pathways underlying the treatment success have been investigated in both clinical and experimental studies. There have been numerous excellent reviews, but these were mostly restricted to limited aspects of the knowledge. The aim of this review is to summarize the known experimental and clinical evidence of SGLT2 inhibitors' effects on individual organs (kidney, heart, liver, etc.), as well as the systemic changes that lead to an improvement in clinical outcomes.

Relationship Between SGLT-2i and Ocular Diseases in Patients With Type 2 Diabetes Mellitus: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

This meta-analysis was conducted to explore the association between sodium-glucose cotransporter 2 inhibitors (SGLT-2is) and ocular diseases in type 2 diabetes mellitus (T2DM) patients.

METHODS

PubMed, Cochrane Central Registry of Controlled Trials, Web of Science and Springer were searched for articles on randomized controlled trials (RCTs) involving T2DM patients treated with SGLT-2i versus placebo or other hypoglycemic agents published prior to August 2021. The primary outcome of this meta-analysis was incidence of ocular diseases, which was assessed using risk ratios (RR) and 95% confidence intervals (CI). We reviewed 47 papers and compared the effect of SGLT-2i with the effect of the control groups (placebo and other hypoglycemic drugs) on the incidence of ocular diseases.

RESULTS

Compared with controls, overall SGLT-2i use in T2DM patients was not associated with incidences of cataract, glaucoma, retinal disease and vitreous disease. Ertugliflozin (RR=0.47, P=0.01) reduced the risk for retinal disease, while empagliflozin (RR=0.44, P=0.05) reduced the risk for diabetic retinopathy (DR) compared with controls. SGLT-2i (RR=0.50, P=0.02), perhaps empagliflozin (RR=0.47, P=0.06), reduced the risk of retinal disease compared with active hypoglycemic agents. Canagliflozin (RR=4.50, P=0.03) increased the risk for vitreous disease compared with placebo.

CONCLUSIONS

There was no significant correlation between overall SGLT-2i and ocular diseases (cataract, glaucoma, retinal disease, vitreous disease, corneal disease, conjunctival disease, uveal disease, eye haemorrhage and vision problems) in T2DM patients. Ertugliflozin and empagliflozin may protect against ocular diseases, but canagliflozin may promote ocular diseases.

Dapagliflozin increases retinal thickness in type 2 diabetic patients as compared with glibenclamide: A randomized controlled trial

AIM

In patients with type 2 diabetes mellitus (T2DM) a progressive thinning in the central retinal thickness (CRT) is mainly related to neuroretinal degeneration and occurs before the decline in visual acuity or capillary density. We investigated the change in CRT by optical coherence tomography (OCT) in T2DM patients after 12 weeks of treatment with dapagliflozin or glibenclamide.

METHODS

Ninety-seven patients (57 ± 7 years) with T2DM and clinical or subclinical atherosclerosis were randomized 1:1 to dapagliflozin (10 mg/day) or glibenclamide (5 mg/day) on top of metformin XR 1.5 g/day. OCT was obtained in all patients enrolled in the study, both at the time of randomization and at the end of the study.

RESULTS

Baseline and post-treatment values of fasting glucose and glycated hemoglobin were equivalent in the two arms. There was no difference in change in diabetic retinopathy status after therapy. The center subfield thickness changed by +2(6)μm in the dapagliflozin group and by -1(7) μm in the glibenclamide group (P = 0.001).

CONCLUSION

A short-term treatment with dapagliflozin may increase CRT as compared with equivalent glycemic control with glibenclamide.