Focusing on Sodium Glucose Cotransporter-2 and the Sympathetic Nervous System: Potential Impact in Diabetic Retinopathy

Recent advances in the treatment and delivery system of diabetic retinopathy

Diabetic retinopathy (DR) is a highly tissue-specific neurovascular complication of type 1 and type 2 diabetes mellitus and is among the leading causes of blindness worldwide. Pathophysiological changes in DR encompass neurodegeneration, inflammation, and oxidative stress. Current treatments for DR, including anti-vascular endothelial growth factor, steroids, laser photocoagulation, and vitrectomy have limitations and adverse reactions, necessitating the exploration of novel treatment strategies. This review aims to summarize the current pathophysiology, therapeutic approaches, and available drug-delivery methods for treating DR, and discuss their respective development potentials. Recent research indicates the efficacy of novel receptor inhibitors and agonists, such as aldose reductase inhibitors, angiotensin-converting enzyme inhibitors, peroxisome proliferator-activated receptor alpha agonists, and novel drugs in delaying DR. Furthermore, with continuous advancements in nanotechnology, a new form of drug delivery has been developed that can address certain limitations of clinical drug therapy, such as low solubility and poor penetration. This review serves as a theoretical foundation for future research on DR treatment. While highlighting promising therapeutic targets, it underscores the need for continuous exploration to enhance our understanding of DR pathogenesis. The limitations of current treatments and the potential for future advancements emphasize the importance of ongoing research in this field.

Sodium-glucose co-transporter 2 inhibitor add-on therapy for metformin delays diabetic retinopathy progression in diabetes patients: a population-based cohort study

To investigate how sodium-glucose co-transporter 2 inhibitors (SGLT2is) add-on therapy for metformin affects diabetic retinopathy (DR) progression in patients with type 2 diabetes mellitus (T2DM). This nationwide population-based study conducted from January 1, 2016, to December 31, 2018 involved 3,432,911 adults with T2DM in Taiwan. To adjust for potential confounders, data on sex, age, income, comorbidities, diabetes complication severity index score, staging of kidney disease, anti-diabetic medications, and index year were included. The outcome was DR progression, determined by procedure codes or the addition of ICD-9-CM or ICD-10-CM codes to the medical records of the patients during the study. Sensitivity analyses were performed to validate the findings. The adjusted hazard ratio (aHR) of DR progression was 0.89 for the SGLT2is add-on group, relative to the control group [95% confidence interval (CI) 0.81-0.99, P = 0.026]. The Kaplan-Meier curve of the cumulative incidence rate showed that the cumulative incidence of DR progression was considerably decreased in the SGLT2is cohort (log-rank P = 0.0261). The use of SGLT2is for less than 1 year and 1-2 years were associated with a significant increase in the risk of DR progression (aHR 1.56 and 1.88, respectively); however, the risk markedly reduced if the SGLT2is regimen was used for more than 2 years (aHR 0.41, 95% Cl 0.35-0.48; P < 0.001). The serial sensitivity analysis showed consistent findings. The aHR of DR progression was 0.82 for the SGLT2is cohort relative to the non-SGLT2is cohort based on the fundoscopy or indirect ophthalmoscopy findings within 1 year before the outcome date (95% Cl 0.71-0.95; P = 0.009). Co-administration of metformin and SGLT2is may reduce the risk of DR progression. Short-term use of SGLT2is may markedly increase the risk of DR, whereas prolonged use SGLT2is may significantly decrease it.

The Impact of SGLT2 Inhibitors in the Heart and Kidneys Regardless of Diabetes Status

Chronic Kidney Disease (CKD) and Cardiovascular Disease (CVD) are two devastating diseases that may occur in nondiabetics or individuals with diabetes and, when combined, it is referred to as cardiorenal disease. The impact of cardiorenal disease on society, the economy and the healthcare system is enormous. Although there are numerous therapies for cardiorenal disease, one therapy showing a great deal of promise is sodium-dependent glucose cotransporter 2 (SGLT2) inhibitors. The SGLT family member, SGLT2, is often implicated in the pathogenesis of a range of diseases, and the dysregulation of the activity of SGLT2 markedly effects the transport of glucose and sodium across the luminal membrane of renal cells. Inhibitors of SGLT2 were developed based on the antidiabetic action initiated by inhibiting renal glucose reabsorption, thereby increasing glucosuria. Of great medical significance, large-scale clinical trials utilizing a range of SGLT2 inhibitors have demonstrated both metabolic and biochemical benefits via numerous novel mechanisms, such as sympathoinhibition, which will be discussed in this review. In summary, SGLT2 inhibitors clearly exert cardio-renal protection in people with and without diabetes in both preclinical and clinical settings. This exciting class of inhibitors improve hyperglycemia, high blood pressure, hyperlipidemia and diabetic retinopathy via multiple mechanisms, of which many are yet to be elucidated.

Will GLP-1 Analogues and SGLT-2 Inhibitors Become New Game Changers for Diabetic Retinopathy?

Diabetic retinopathy (DR) is the most frequent microvascular complication of diabetes mellitus (DM), estimated to affect approximately one-third of the diabetic population, and the most common cause of preventable vision loss. The available treatment options focus on the late stages of this complication, while in the early stages there is no dedicated treatment besides optimizing blood pressure, lipid and glycemic control; DR is still lacking effective preventive methods. glucagon-like peptide 1 receptor agonists (GLP-1 Ras) and sodium-glucose cotransporter 2 (SGLT-2) inhibitors have a proven effect in reducing risk factors of DR and numerous experimental and animal studies have strongly established its retinoprotective potential. Both drug groups have the evident potential to become a new therapeutic option for the prevention and treatment of diabetic retinopathy and there is an urgent need for further comprehensive clinical trials to verify whether these findings are translatable to humans.

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.

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.

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

PURPOSE

To evaluate the effects of metformin alone and combined treatment with metformin and an SGLT2 inhibitor on retinal microvascular morphology using optical coherence tomography angiography (OCTA) in isolated type 2 diabetes mellitus (DM) patients with HbA1c above the expected target (>7%).

METHODS

Fifty patients with isolated DM, 7%<HbA1c<8%, without diabetic retinopathy (DR) using 500mg metformin ×2 for glycemic control were included in the study. OCTA and BMI measurements were obtained at the first evaluation. Treatment was changed to metformin 1000mg ×2. Patients who did not develop side effects due to the metformin were defined as the metformin-tolerant group (group-1). Patients who developed side effects were defined as the metformin-intolerant group (group-2), and their treatment was changed to metformin 500mg ×2 and empagliflozin 10mg. The second evaluation was performed three months after the last treatment change.

RESULTS

HbA1c was lower on the second evaluation in both groups (P<0.001, in both). On the second evaluation in group-1, a decrease was found in superficial perifoveal and deep parafoveal macular vascular plexus densities (P: 0.040 and P: 0.020, respectively). No statistically significant difference was observed in group-2.

CONCLUSION

SGLT2 inhibitors may contribute to preventing the development of preclinical DR. In patients with metformin intolerance, adding SGLT2 inhibitors may be a reasonable choice to protect the retina.

The Safety of Pharmacological and Surgical Treatment of Diabetes in Patients with Diabetic Retinopathy-A Review

BACKGROUND

Diabetes mellitus (DM) is a non-infectious pandemic of the modern world; it is estimated that in 2045 it will affect 10% of the world's population. As the prevalence of diabetes increases, the problem of its complications, including diabetic retinopathy (DR), grows. DR is a highly specific neurovascular complication of diabetes that occurs in more than one third of DM patients and accounts for 80% of complete vision loss cases in the diabetic population. We are currently witnessing many groundbreaking studies on new pharmacological and surgical methods of treating diabetes.

AIM

The aim of the study is to assess the safety of pharmacological and surgical treatment of DM in patients with DR.

MATERIAL AND METHODS

An analysis of the data on diabetes treatment methods currently available in the world literature and their impact on the occurrence and progression of DR.

RESULTS

A rapid decrease in glycaemia leads to an increased occurrence and progression of DR. Its greatest risk accompanies insulin therapy and sulfonylurea therapy. The lowest risk of DR occurs with the use of SGLT2 inhibitors; the use of DPP-4 inhibitors and GLP-1 analogues is also safe. Patients undergoing pancreatic islet transplants or bariatric surgeries require intensive monitoring of the state of the eye, both in the perioperative and postoperative period.

CONCLUSIONS

It is of utmost importance to individualize therapy in diabetic patients, in order to gradually achieve treatment goals with the use of safe methods and minimize the risk of development and progression of DR.

Sodium-Glucose Cotransporter 2 Inhibitors Improve Chronic Diabetic Macular Edema

Purpose

Diabetic macular edema (DME) is a vision-threatening condition that develops in diabetic patients. The first-line therapy for DME is intravitreal injections of antivascular endothelial growth factor (anti-VEGF) agents; however, the high frequency of repeat injections, invasiveness of the procedure, and high cost are drawbacks for this treatment. The purpose of this report is to present our findings in 3 patients with chronic DME whose edema was resolved soon after oral doses of sodium-glucose cotransporter-2 (SGLT2) inhibitors were used. Case Presentation. Case 1 was a 66-year-old woman diagnosed with moderate nonproliferative diabetic retinopathy (DR) with DME that had developed a decade earlier. The DME persisted for 4 years in the left eye. The addition of oral empagliflozin, a SGLT2 inhibitor, led to a marked improvement of the DME after one month, and this improvement continued over two years. Case 2 was a 68-year-old woman who was diagnosed with preproliferative DR with bilateral DME. The addition of oral dapagliflozin led to the improvement of the DME after two months, and this improvement continued over one year. Case 3 was a 61-year-old woman who was diagnosed with moderate nonproliferative DR with DME. Oral luseogliflozin was given which led to better glycemic control, and her left central retinal thickness (CRT) was markedly reduced after only two weeks. This reduction was maintained in her left eye for six months without any additional ophthalmic procedures.

Conclusions

Although this study involved only three cases, our findings indicate that SGLT2 inhibitors might have possible efficacy for chronic DME.

Metabolomic profile of diabetic retinopathy: a GC-TOFMS-based approach using vitreous and aqueous humor

AIM

To identify the potential metabolite markers in diabetic retinopathy (DR) by using gas chromatography coupled with time-of-flight mass spectrometry (GC-TOFMS).

METHODS

GC-TOFMS spectra were acquired from vitreous and aqueous humor (AH) samples of patients with DR and non-diabetic participants. Comparative analysis was used to elucidate the distinct metabolites of DR. Metabolic pathway was employed to explicate the metabolic reprogramming pathways involved in DR. Logistic regression and receiver-operating characteristic analyses were carried out to select and validate the biomarker metabolites and establish a therapeutic model.

RESULTS

Comparative analysis showed a clear separation between disease and control groups. Eight differentiating metabolites from AH and 15 differentiating metabolites from vitreous were highlighted. Out of these 23 metabolites, 11 novel metabolites have not been detected previously. Pathway analysis identified nine pathways (three in AH and six in vitreous) as the major disturbed pathways associated with DR. The abnormal of gluconeogenesis, ascorbate-aldarate metabolism, valine-leucine-isoleucine biosynthesis, and arginine-proline metabolism might weigh the most in the development of DR. The AUC of the logistic regression model established by D-2,3-Dihydroxypropanoic acid, isocitric acid, fructose 6-phosphate, and L-Lactic acid in AH was 0.965. The AUC established by pyroglutamic acid and pyruvic acid in vitreous was 0.951.

CONCLUSIONS

These findings have expanded our understanding of identified metabolites and revealed for the first time some novel metabolites in DR. These results may provide useful information to explore the mechanism and may eventually allow the development of metabolic biomarkers for prognosis and novel therapeutic strategies for the management of DR.

The Role of SGLT2 Inhibitor on the Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most serious complications of diabetic microangiopathy. DR has an early onset and is not easy to detect. When visual impairment occurs, the optimal period for therapy is often missed. Therefore, the prevention and treatment of DR should start from the early stage of diabetes. Sodium-dependent glucose transporter 2 inhibitor (SGLT2i) is a new antidiabetic drug which is mainly used in clinical practice to control blood glucose of patients with type 2 diabetes prone to develop chronic heart failure. Recent studies have found that SGLT2 is also expressed in the human retina. Now, the prevention and treatment of diabetic retinopathy with SGLT2i while reducing blood sugar has become a new research field. Hence, this article reviewed the recent therapeutic and research progress of SGLT2 in the treatment of diabetic retinopathy.

Effects of sodium-glucose cotransporter-2 inhibitors and dipeptidyl peptidase-4 inhibitors on diabetic retinopathy and its progression: A real-world Korean study

The sodium-glucose cotransporter-2 inhibitors (SGLT2is) reduce the incidence of macrovascular complications of diabetes, while their effect on diabetic retinopathy has not been clarified. We compared the effects of SGLT2is with those of dipeptidyl peptidase-4 inhibitors (DPP4is) on the risk of diabetic retinopathy and its progression in people with type 2 diabetes. We performed a retrospective cohort study among people with type 2 diabetes who started on a SGLT2i or DPP4i from 2014 to 2016 according to the Korean National Health Insurance Service database. Subjects initiated on a SGLT2i or DPP4i were matched on a 1:1 basis according to their propensity scores, and Cox proportional hazards regression models were used to calculate the hazard ratios for the risk of diabetic retinopathy and its progression. After propensity score-matching, 41,430 patients without a history of diabetic retinopathy were identified as new users of a SGLT2i (n = 20,175) or DPP4i (n = 20,175). The hazard ratio (95% CI) for diabetic retinopathy was 0.89 (0.83–0.97) for SGLT2i initiators compared with DPP4i initiators. In patients with a history of diabetic retinopathy (n = 4,663 pairs), there was no significant difference in diabetic retinopathy progression between SGLT2i initiators and DPP4i initiators (hazard ratio 0.94, 95% CI 0.78–1.13). This real-world cohort study showed that SGLT2is might be associated with lower risk of diabetic retinopathy compared with DPP4is. Randomized controlled trials are needed to investigate the long-term effect of SGLT2is in diabetic retinopathy in people with diabetes.

Diabetic retinopathy and age-related macular degeneration: a survey of pharmacoutilization and cost in Calabria, Italy

The aged population is constantly growing, thus fostering an increase in age-dependent diseases. Among these, diabetic retinopathy (DR) along with age-related macular degeneration entails progressive vision loss. Since such conditions are associated with the proliferation of novel vessels, their pharmacotherapeutic management consists of the intravitreal injection of anti-vascular endothelial growth factor drugs, able to hinder the driving of vascular proliferation prompted by vascular endothelial growth factor. The humanized anti-vascular endothelial growth factor monoclonal antibody ranibizumab provided evidence for efficacy in several trials, hence earning approval by the US Food and Drug Administration for therapeutic use in all the stages of DR. Due to the lack of epidemiologic and pharmacoeconomic evaluation in the local Calabria Region context, the present retrospective observational study focused on prevalence of DR and age-related macular degeneration, treatment and cost of therapy with ranibizumab in 870 patients arriving to clinical observation at the "Mater Domini" University Hospital in Calabria, Italy from January 2014 to June 2017. Data were extracted from the database of ophthalmology ward and subjected to statistical analysis. The results suggest that the most frequent retinal diseases are age-related macular degeneration and DR and that the use of ranibizumab has been decreasing over the 4-year study period together with the associated cost per patient which was similar for both disorders. Therefore, appropriateness of treatment with drugs other than ranibizumab needs to be assessed in this setting and deep monitoring of pharmacologic treatment for retinal diseases is necessary to prevent or delay visual acuity decrease and complete vision loss. Study procedures were performed in accordance with the "Mater Domini" University Hospital ethical standards of the responsible committee on human experimentation.

How and why SGLT2 inhibitors should be explored as potential treatment option in diabetic retinopathy: clinical concept and methodology

Patients suffering from type 2 diabetes are at an increased risk of developing classical microvascular complications such as retinopathy, neuropathy, and nephropathy, which represent a significant health burden. Tight control of blood glucose, blood pressure, and serum cholesterol reduce the risk of microvascular complications but effective pharmacologically targeted treatment options for the treatment and prevention of diabetic microangiopathy are still lacking. Pharmacological inhibition of sodium glucose cotransporter 2 (SGLT2) might have the potential to directly protect against microvascular complications and could represent a potential treatment option. Randomized controlled clinical proof of concept trials are needed to investigate a potential central role of SGLT2 inhibitors in the prevention of diabetic microangiopathy and its classical clinical complications of retinopathy, neuropathy, and nephropathy.