Normalization of glucose entry under the high glucose condition by phlorizin attenuates the high glucose-induced morphological and functional changes of cultured bovine retinal pericytes

Sodium-glucose cotransporter 2 inhibitor therapy reduces the administration frequency of steroid injection in patients with diabetic macular edema: A cohort study using the Japanese health insurance claims database

AIMS/INTRODUCTION

Severe diabetic macular edema (DME) is often resistant to anti-vascular endothelial growth factor therapy. Steroids are particularly effective at reducing edema by suppressing inflammation; they are also used as an alternative to expensive anti-vascular endothelial growth factor therapy in some patients. Therefore, the use of steroids in DME reflects an unmet need for anti-vascular endothelial growth factor therapy. Notably, triamcinolone acetonide (TA) injections are widely used in Japan. Here, we evaluated the frequency of TA as an indicator of the efficacy of sodium-glucose cotransporter 2 inhibitors (SGLT2is) in DME treatment using a health insurance claims database.

MATERIALS AND METHODS

In this cohort study, we retrospectively analyzed the health insurance claims data of 11 million Japanese individuals from 2005 to 2019. The frequency and duration of TA injection after the initiation of SGLT2is or other antidiabetic drugs were analyzed.

RESULTS

Among the 2,412 matched patients with DME, the incidence rate of TA injection was 63.8 times per 1,000 person-years in SGLT2i users and 94.9 times per 1,000 person-years in non-users. SGLT2is reduced the risk for the first (P = 0.0024, hazard ratio 0.66, 95% confidence interval 0.50-0.87), second (P = 0.0019, hazard ratio 0.53, 95% confidence interval 0.35-0.80) and third TA (P = 0.0053, hazard ratio 0.44, 95% confidence interval 0.25-0.80) injections. A subanalysis of each baseline characteristic of the patients showed that SGLT2is were effective regardless of the background factors.

CONCLUSIONS

The use of SGLT2is reduced the frequency of TA injection in patients with DME. Therefore, SGLT2i therapy might be a novel, noninvasive and low-cost adjunctive therapy for DME.

Sodium-glucose co-transporter 2 inhibitor therapy reduces the administration frequency of anti-vascular endothelial growth factor agents in patients with diabetic macular oedema with a history of anti-vascular endothelial growth factor agent use: A cohort study using the Japanese health insurance claims database

AIM

We assessed the effectiveness of sodium-glucose co-transporter 2 inhibitors (SGLT2is) in reducing the administration frequency of anti-vascular endothelial growth factor (VEGF) agents in patients with diabetic macular oedema (DMO) using a health insurance claims database.

MATERIALS AND METHODS

This retrospective cohort study analysed health insurance claims data covering 11 million Japanese patients between 2005 and 2019. We analysed the frequency and duration of intravitreal injection of anti-VEGF agents after initiating SGLT2is or other antidiabetic drugs.

RESULTS

Among 2412 matched patients with DMO, the incidence rates of anti-VEGF agent injections were 230.1 per 1000 person-year in SGLT2i users and 228.4 times per 1000 person-year in non-users, respectively, and the risk ratio for events was unchanged in both groups. Sub-analysis of each baseline characteristic of the patients showed that SGLT2is were particularly effective in patients with a history of anti-VEGF agent use [p = .027, hazard ratio (HR): 0.44, 95% confidence interval (CI): 0.22-0.91]. SGLT2is reduced the risk for the first (p = .023, HR: 0.45, 95% CI: 0.22-0.91) and second (p = .021, HR: 0.39, 95% CI: 0.17-0.89) anti-VEGF agent injections.

CONCLUSIONS

There was no difference in the risk ratio for the addition of anti-VEGF therapy between the two treatment groups. However, the use of SGLT2is reduced the frequency of anti-VEGF agent administration in patients with DMO requiring anti-VEGF therapy. Therefore, SGLT2i therapy may be a novel, non-invasive, low-cost adjunctive therapy for DMO requiring anti-VEGF therapy.

Sodium-Glucose Cotransporter 2 Inhibitors and Risk of Retinopathy in Patients With Type 2 Diabetes

Importance

Diabetic nephropathy and diabetic retinopathy share many similarities in pathophysiological processes. Preclinical studies have shown that sodium-glucose cotransporter 2 inhibitors (SGLT2is) have a protective role in the risk of diabetic retinopathy.

Objective

To compare the risk of sight-threatening retinopathy associated with SGLT2is and other second-line glucose-lowering medications (including pioglitazone, sulfonylureas, and dipeptidyl peptidase-4 inhibitors [DPP-4is]) in patients with type 2 diabetes (T2D).

Design, Setting, and Participants

This cohort study in Taiwan applied a new-user and active-comparator design. Patient demographic and clinical data were obtained from the National Health Insurance Research Database. Adult patients with newly diagnosed T2D from January 1, 2009, to December 31, 2019, were recruited and followed up until December 31, 2020. Propensity score matching was used to identify pairs of patients treated with SGLT2i vs DPP-4i, SGLT2i vs pioglitazone, and SGLT2i vs sulfonylurea from January 1, 2016, to December 31, 2019. Data were analyzed between August 18, 2022, and May 5, 2023.

Exposures

Treatment with SGLT2i, DPP-4i, pioglitazone, and sulfonylureas starting on January 1, 2016.

Main Outcomes and Measures

The main outcome was sight-threatening retinopathy in participants. Cox proportional hazards regression models were used to assess relative hazards of sight-threatening retinopathy between the matched case and control groups.

Results

A total of 3 544 383 patients with newly diagnosed T2D were identified. After 1:1 propensity score matching, 65 930 pairs of patients treated with SGLT2i vs DPP-4i, 93 760 pairs treated with SGLT2i vs pioglitazone, and 42 121 pairs treated with SGLT2i vs sulfonylurea were identified. These matched patients included 236 574 males (58.6%), with a mean (SD) age of 56.9 (11.8) years. In the matched cohorts, SGLT2i had a significantly lower risk of sight-threatening retinopathy than DPP-4i (adjusted hazard ratio [AHR], 0.57; 95% CI, 0.51-0.63), pioglitazone (AHR, 0.75; 95% CI, 0.69-0.81), and sulfonylureas (AHR, 0.62; 95% CI, 0.53-0.71). The Kaplan-Meier curves showed that SGLT2i was associated with a significantly lower cumulative incidence of sight-threatening retinopathy than DPP-4i (3.52 vs 6.13; P < .001), pioglitazone (4.32 vs 5.76; P < .001), and sulfonylureas (2.94 vs 4.67; P < .001).

Conclusions and Relevance

This cohort study found that SGLT2i was associated with a lower risk of sight-threatening retinopathy compared with DPP-4i, pioglitazone, and sulfonylureas. This finding suggests that SGLT2i may play a role not only in reduced risk of diabetic nephropathy but also in the slow progression of diabetic retinopathy in patients with T2D.

The presence of sodium glucose co-transporter 2 in mesangial cells and pericytes and its roles in mesangial lesions and in capillaries under diabetic and ischemic conditions

SGLT2 is expressed in mesangial cells and pericytes, and is upregulated byhigh glucose and ischemia. Upregulated SGLT2 in both cells might directly worsen ischemia in kidney interstitial legion, heart and brain. The overexpression of SGLT2 in these cells could induce various organ failures via damages or loss of capillaries and dysfunctions of mesangial cells, which are attenuated by SGLT2 inhibitors.

Roles of Sodium-Glucose Cotransporter 2 of Mesangial Cells in Diabetic Kidney Disease

We have been studying the presence of sodium-glucose cotransporter 2 (SGLT2) in mesangial cells and pericytes since 1992. Recent large placebo-controlled studies of SGLT2 inhibitors in patients with type 2 diabetes mellitus have reported desirable effects of the inhibitors on the diabetic kidney and the diabetic heart. Most studies have indicated that these effects of SGLT2 inhibitors could be mediated by the tubuloglomerular feedback system. However, a recent study about urine sodium excretion in the presence of an SGLT2 inhibitor did not show any increases in urine sodium excretion. A very small dose of an SGLT2 inhibitor did not inhibit SGLT2 at the S1 segment of proximal tubules. Moreover, SGLT2 inhibition protects against progression in chronic kidney disease with and without type 2 diabetes. In these circumstances, the tubuloglomerular feedback hypothesis involves several theoretical concerns that must be clarified. The presence of SGLT2 in mesangial cells seems to be very important for diabetic nephropathy. We now propose a novel mechanism by which the desirable effects of SGLT2 inhibitors on diabetic nephropathy are derived from the direct effect on SGLT2 expressed in mesangial cells.

SGLT2 Inhibitor-Induced Low-Grade Ketonemia Ameliorates Retinal Hypoxia in Diabetic Retinopathy-A Novel Hypothesis

Diabetic retinopathy (DR) is a well-recognized microvascular complication of diabetes. Growing evidence suggests that, in addition to retinal vascular damage, there is significant damage to retinal neural tissue in DR. Studies reveal neuronal damage before clinically evident vascular lesions and DR is now classified as a neurovascular complication. Hyperglycemia causes retinal damage through complex metabolic pathways leading to oxidative stress, inflammation, vascular damage, capillary ischemia, and retinal tissue hypoxia. Retinal hypoxia is further worsened by high oxygen consumption in the rods. Persistent hypoxia results in increases in vascular endothelial growth factor (VEGF) and other pro-angiogenic factors leading to proliferative DR/macular edema and progressive visual impairment. Optimal glucose control has favorable effects in DR. Other treatments for DR include laser photocoagulation, which improves retinal oxygenation by destroying the high oxygen consuming rods and their replacement by low oxygen consuming glial tissue. Hypoxia is a potent stimulator of VEGF, and intravitreal anti-VEGF antibodies are effective in regressing macular edema and in some studies, retinal neovascularization. In this review, we highlight the complex pathophysiology of DR with a focus on retinal oxygen/fuel consumption and hypoxic damage to retinal neurons. We discuss potential mechanisms through which sodium-glucose cotransporter 2 (SGLT2) inhibitors improve retinal hypoxia-through ketone bodies, which are energetically as efficient as glucose and yield more ATP per molecule of oxygen consumed than fat, with less oxidative stress. Retinal benefits would occur through improved fuel energetics, less hypoxia and through the anti-inflammatory/oxidative stress effects of ketone bodies. Well-designed studies are needed to explore this hypothesis.

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.

Lessons from the Trials for the Desirable Effects of Sodium Glucose Co-Transporter 2 Inhibitors on Diabetic Cardiovascular Events and Renal Dysfunction

Recent large placebo-controlled trials of sodium glucose co-transporter 2 (SGLT2) inhibitors revealed desirable effects on heart failure (HF) and renal dysfunction; however, the mechanisms underlying these effects are unknown. The characteristic changes in the early stage of diabetic cardiomyopathy (DCM) are myocardial and interstitial fibrosis, resulting in diastolic and subsequent systolic dysfunction, which leads to clinical HF. Pericytes are considered to play crucial roles in myocardial and interstitial fibrosis. In both DCM and diabetic retinopathy (DR), microaneurysm formation and a decrease in capillaries occur, triggered by pericyte loss. Furthermore, tubulointerstitial fibrosis develops in early diabetic nephropathy (DN), in which pericytes and mesangial cells are thought to play important roles. Previous reports indicate that pericytes and mesangial cells play key roles in the pathogenesis of DCM, DR and DN. SGLT2 is reported to be functionally expressed in pericytes and mesangial cells, and excessive glucose and Na+ entry through SGLT2 causes cellular dysfunction in a diabetic state. Since SGLT2 inhibitors can attenuate the high glucose-induced dysfunction of pericytes and mesangial cells, the desirable effects of SGLT2 inhibitors on HF and renal dysfunction might be explained by their direct actions on these cells in the heart and kidney microvasculature.

Protective effect of apple phlorizin on hydrogen peroxide-induced cell damage in HepG2 cells

Apple phlorizin has many biological activities, such as antioxidant and liver protection. The present study aimed to evaluate the roles of apple phlorizin against hydrogen peroxide (H₂ O₂ )-induced oxidative damage in HepG2 cells. In this study, treatment with apple phlorizin (100 and 150 μg/ml) decreased the production of reactive oxygen species and alleviated apoptosis as well as DNA damage in H₂ O₂ -induced HepG2 cells. These effects were associated with the increased activity of antioxidant enzymes, enhanced the ARE-driven phase II antioxidant gene expression and its upstream Nrf2 protein expression, and decreased apoptosis-related gene expression. However, the phase II antioxidant gene expression and Nrf2 protein expression upregulated by phlorizin were reversed by Nrf2 shRNA transfection. These results showed that phlorizin relieves oxidative stress, DNA damage, and apoptosis in H₂ O₂ -induced HepG2 cells, at least partially, by regulating the expression of Nrf2 protein and apoptosis-related genes. PRACTICAL APPLICATIONS: Apple phlorizin is a polyphenol compound extracted from apple or apple juice. This report highlighted a protective effect of phlorizin on antioxidant stress, DNA damage, and apoptosis in H₂ O₂ -induced HepG2 cells. These results suggested that phlorizin may be developed for functional foods.

The Efficacy of Sodium-Glucose Cotransporter 2 (SGLT2) inhibitors for the treatment of chronic diabetic macular oedema in vitrectomised eyes: a retrospective study

Objective

To investigate the change of chronic diabetic macular oedema (DMO) in vitrectomised eyes when the administration of sodium–glucose cotransporter 2 (SGLT2) inhibitors is initiated as a systemic medical treatment.

Methods and analysis

This study involved 10 eyes of five patients with chronic DMO lasting more than 6 months who had previously undergone vitrectomy and whose systemic medical treatments were newly changed to SGLT2 inhibitors. In this study, chronic DMO was defined as persistent diffuse macular oedema despite ophthalmic treatment in patients with diabetes. Patients who received antivascular endothelial growth factor therapy or steroids administration, or change of eye-drop medication from at 3 months before and after the initiation of SGLT2 inhibitors, were excluded. In this study, visual acuity (VA) and central retinal thickness (CRT, μm) prior to and at 3, 6 and 12 months after the initiation of SGLT2 inhibitors were retrospectively compared. The Wilcoxon signed-rank test was used for statistical analysis.

Results

In the 10 treated eyes, from at baseline to at 3, 6 and 12 months after the initiation of SGLT2 inhibitor, median VA (logMAR) improved from 0.35 to 0.15 (p=0.038), 0.2 (p=0.157) and 0.2 (p=0.096), respectively, and median CRT significantly reduced from 500.5 µm to 410 µm (p<0.01), 378 µm (p<0.01) and 339 µm (p<0.01), respectively.

Conclusion

Although this study involved only five patients, our findings indicate that SGLT2 inhibitors might have structural efficacy for chronic DMO in vitrectomised eyes.

Recovery from Diabetic Macular Edema in a Diabetic Patient After Minimal Dose of a Sodium Glucose Co-Transporter 2 Inhibitor

BACKGROUND Diabetic macular edema (DME) causes serious visual impairments in diabetic patients. The standard treatments of DME are intra-vitreous injections of corticosteroids or anti-vascular endothelial growth factor antibodies and pan-photocoagulation. These treatments are unsatisfactory in their effects and impose considerable physical and economic burdens on the patients. CASE REPORT A 63-year-old woman was diagnosed as type 2 diabetes with retinopathy 7 years ago. Before the initiation of an SGLT2 inhibitor, the dipeptidyl peptidase-4 inhibitor, sitagliptin (50 mg daily), and metformin (250 mg dai- ly) were used for her glycemic control. The level of her hemoglobin A1c had been controlled around 7%. She began to feel decreased visual acuity and blurred vision of her left eye 8 months before the visit to our clin- ic. She was diagnosed as DME, which turned out to be corticosteroid-resistant. Her visual acuity further de- creased to 20/50. Metformin was changed to ipraglifl (25mg/day). Her left visual acuity started to improve after 4 weeks of treatment with ipragliflozin and improved to 20/22 after 24 weeks. The macular edema did not change until 12 weeks of the treatment, however, it decreased prominently after 16 weeks. CONCLUSIONS In our patient with steroid-resistant DME, her visual symptoms and macular edema recovered after the initiation of an SGLT2 inhibitor. SGLT2 inhibitors might be a potential candidate for the DME treatment.

Sodium glucose cotransporter 2 in mesangial cells and retinal pericytes and its implications for diabetic nephropathy and retinopathy

Retinopathy and nephropathy are life-threatening diabetic complications that decrease patient quality of life. Although the mechanisms underlying these conditions have been extensively studied, they remain unknown. Recent reports have demonstrated the presence of sodium glucose cotransporter 2 (SGLT2) in retinal pericytes and mesangial cells. Hyperglycemia results in functional and morphological changes in these cells, but these effects are attenuated by phlorizin, a nonselective SGLT inhibitor. Based on these findings, we hypothesized that SGLT2 plays a pivotal role in the development of diabetic nephropathy and retinopathy and that SGLT2 inhibitors may directly protect against these complications.

Sodium Glucose Cotransporter 2 (SGLT2) Plays as a Physiological Glucose Sensor and Regulates Cellular Contractility in Rat Mesangial Cells

PURPOSE

Mesangial cells play an important role in regulating glomerular filtration by altering their cellular tone. We report the presence of a sodium glucose cotransporter (SGLT) in rat mesangial cells. This study in rat mesangial cells aimed to evaluate the expression and role of SGLT2.

METHODS

The SGLT2 expression in rat mesangial cells was assessed by Western blotting and reverse transcription-polymerase chain reaction (RT-PCR). Changes in the mesangial cell surface area at different glucose concentrations and the effects of extracellular Na+ and Ca2+ and of SGLT and Na+/Ca2+ exchanger (NCX) inhibitors on cellular size were determined. The cellular sizes and the contractile response were examined during a 6-day incubation with high glucose with or without phlorizin, an SGLT inhibitor.

RESULTS

Western blotting revealed an SGLT2 band, and RT-PCR analysis of SGLT2 revealed the predicted 422-bp band in both rat mesangial and renal proximal tubular epithelial cells. The cell surface area changed according to the extracellular glucose concentration. The glucose-induced contraction was abolished by the absence of either extracellular Na+ or Ca2+ and by SGLT and NCX inhibitors. Under the high glucose condition, the cell size decreased for 2 days and increased afterwards; these cells did not contract in response to angiotensin II, and the SGLT inhibitor restored the abolished contraction.

CONCLUSIONS

These data suggest that SGLT2 is expressed in rat mesangial cells, acts as a normal physiological glucose sensor and regulates cellular contractility in rat mesangial cells.

Connection of pericyte-angiopoietin-Tie-2 system in diabetic retinopathy: friend or foe?

Pericytes are distinctive regulators of vascular morphologenesis and function during vascular development and homeostasis. Pericytes have recently come into focus as implications of aberrant interactions between pericytes and endothelial cells in number of pathological angiogenesis conditions, including diabetic retinopathy and tumor angiogenesis. Pericyte dropout is a hallmark of early diabetic retinopathy. Abnormal angiopoietin (Ang)-Tie-2 signaling is one principal system participating in pericyte/endothelial cell dissociation during early stages of diabetic retinopathy. Angiopoietin 2 (Ang-2) is among the relevant growth factors induced by hypoxia and plays an important role in the initiation of retinal neovascularization and cause pericyte loss. Furthermore, high levels of VEGF synergize Ang-Tie-2 signaling during the development of diabetic retinopathy. An accelerated rate of clinical development Ang-Tie-2-manipulating drugs requests a better mechanistic understanding the connection between pericytes and Ang-Tie-2 systems both under normal and disease conditions. We summarize recent advances in pericyte study in conjunction with Ang-Tie-2 signaling and also discuss possible therapeutic strategies for diabetic retinopathy by targeting pericytes through manipulating Ang-Tie-2 signaling.

Phlorizin prevents glomerular hyperfiltration but not hypertrophy in diabetic rats

The relationships of renal and glomerular hypertrophies to development of hyperfiltration and proteinuria early in streptozotocin-induced diabetes were explored. Control, diabetic, phlorizin-treated controls, and diabetic male Fischer rats were used. Phlorizin (an Na⁺-glucose cotransport inhibitor) was given at a dose sufficient to normalize blood glucose. Inulin clearance (C_inulin) and protein excretion rate (PER) were measured. For morphometry, kidney sections were stained with periodic acid Schiff. At one week, diabetes PER increased 2.8-folds (P < .001), C_inulin increased 80% (P < .01). Kidney wet and dry weights increased 10%–12% (P < .05), and glomerular tuft area increased 9.3% (P < .001). Phlorizin prevented proteinuria, hyperfiltration, and kidney hypertrophy, but not glomerular hypertrophy. Thus, hyperfiltration, proteinuria, and whole kidney hypertrophy were related to hyperglycemia but not to glomerular growth. Diabetic glomerular hypertrophy constitutes an early event in the progression of glomerular pathology which occurs in the absence of mesangial expansion and persists even after changes in protein excretion and GFR are reversed through glycemic control.

High glucose and advanced glycation end products induce phospholipid hydrolysis and phospholipid enzyme inhibition in bovine retinal pericytes

In the present study, we investigated the possible role of oxidative stress and the modulation of phospholipid turnover in two related models of pericyte injury, i.e., treatment with high glucose or advanced glycation end products (AGEs). Growing microcapillary pericytes from bovine retinas in culture were incubated, for 3 weeks, with 20-50 mM glucose or 2-20 microM AGEs, and peroxidation parameters (malondialdehyde, conjugated diene, hydroperoxide, glutathione (GSH) levels and lactate dehydrogenase (LDH) release) were evaluated. Arachidonate (AA) and choline release from membrane phospholipids was determined in pericytes prelabeled with [1-(14)C]arachidonate and [Me-(3)H]choline, respectively, and stimulated with elevated glucose or AGEs for 30 min or 2 h. [1-(14)C]arachidonate and [Me-(3)H]choline incorporation into phospholipids, for 2 h and 3 h respectively, was also studied in conditioned and serum-starved cultures. Finally, lysates of treated and control cells were assayed for cytosolic phospholipase A(2) (cPLA(2)), acyl-CoA:1-acyl-sn-glycero-3-phosphocholine O-acyltransferase (AT), CTP:phosphocholine cytidylyltransferase (CT) and microsomal choline phosphotransferase (CPT) enzyme activities. We found that high glucose and AGEs caused neither significant production of reactive oxygen species nor cell toxicity or death, unlike other cell types. Both agents had no significant effect on the cellular ultrastructure, evaluated by light and electron microscopy, AA incorporation and release, cytosolic phospholipase A(2) (cPLA(2)) and AT activities. On the contrary, choline incorporation into phosphatidylcholine, CT and CPT activities were significantly reduced either by 50 mM glucose or 20 microM AGEs. Simultaneously, [Me-(3)H]choline release was significantly stimulated by both agents. We conclude that prolonged treatments with high glucose or AGEs are not able to induce oxidative injury in bovine retinal capillary pericytes. Nevertheless, they do induce phospholipid hydrolysis and phospholipid enzyme activity inhibition.

Sodium-coupled glucose transporter as a functional glucose sensor of retinal microvascular circulation

To clarify the function of the Na(+)-coupled glucose transporter in the regulation of cellular tone of cultured retinal pericytes, we investigated the effects of extracellular glucose concentration on cell size. The surface area and diameter of cultured bovine retinal pericytes under different glucose concentrations were measured by using a light microscope with a digital camera. We also examined the effects of extracellular Na(+) and Ca(2+), inhibitors of the Na(+)-coupled glucose transporter and Na(+)-Ca(2+) exchanger, a Ca(2+) channel blocker, and nonmetabolizable sugars on cell size. The surface area and diameter of the cells changed according to extracellular glucose concentrations. alpha-Methyl glucoside, which enters the cell through the Na(+)-coupled glucose transporter, induced cellular contraction. However, the cells did not contract in response to 2-deoxyglucose, which enters the cell through a facilitated glucose transporter. Glucose-induced cellular contraction was abolished in the absence of extracellular Na(+) and Ca(2+). Moreover, phlorizin, an inhibitor of the Na(+)-coupled glucose transporter, and 2',4'-dichlorobenzamil-HCl, an inhibitor of the Na(+)-Ca(2+) exchanger, also abolished glucose-induced cellular contraction, whereas nicardipine, a Ca(2+) channel blocker, did not. Our results indicate that high extracellular glucose concentrations induce contraction of bovine retinal pericytes via Na(+) entry through a Na(+)-coupled glucose transporter, suggesting that the Na(+)-coupled glucose transporter may act as a functional glucose sensor of retinal microvascular circulation.>

Diversity within pericytes

1. Pericytes are cells of microvessels (arterioles, capillaries and venules) that wrap around endothelial cells. They are most abundant on venules and are common on capillaries. 2. The pericyte population is highly variable between different tissues and organs, probably in a manner reflecting postarteriolar hydrostatic pressures. Pericytes are more abundant in the distal legs and feet, again suggesting a hydrostatic pressure-driven mechanical role for pericytes as protectors of microvessel wall integrity. 3. Pericyte alteration or degeneration is linked directly with microangiopathy in diabetes, scleroderma, hypertension, dementias and, possibly, inappropriate calcification of blood vessels. 4. Pericytes are functionally codependent on endothelial cells. Each cell type influences each others' mitotic rate and probably phenotypic expression. 5. Pericytes are not randomly located around microvessels. Instead, they are located adjacent to or over endothelial cell junctions of venules and especially over gaps between endothelial cells during inflammation. Pericytes are emerging as essential components of the microvessel wall, with metabolic, signalling and mechanical roles to support the endothelial cell.

Troglitazone enhances glycolysis and improves intracellular glucose metabolism in rat mesangial cells

To clarify the action of the new antidiabetic agent, troglitazone, on rat mesangial cells, we assessed its effect on the uptake and intracellular metabolism of glucose. Troglitazone increased the uptake of 2-deoxyglucose (2DOG) in a dose-dependent manner with an upregulation of glucose transporter 1 (GLUT1) mRNA, whereas it had no effect on the uptake of alpha-methyl glucoside (AMG). This troglitazone-induced glucose uptake was not suppressed by phlorizin. In 5 mmol/L glucose, 2 microg/mL (4.5 micromol/L) troglitazone increased glucose consumption 2.9-fold, similar to that in 20 mmol/L glucose. Troglitazone increased the production of pyruvate and lactate as a consequence of the increase in glycolysis, but did not increase the cellular ATP content. Troglitazone improved the high-glucose-induced accumulation of intracellular sorbitol and fructose and elevation of the cellular redox potential. These data suggest that troglitazone enhances glucose uptake through GLUT1 with an acceleration of glycolysis, and improves the abnormal intracellular glucose metabolism under high-glucose conditions in rat mesangial cells.

Suppression of sodium-dependent glucose uptake by captopril improves high-glucose-induced morphological and functional changes of cultured bovine retinal pericytes

The effects of captopril on glucose uptake, as well as morphological and functional changes of retinal pericytes, in a high-glucose medium were examined. Retinal pericytes were incubated in medium with 5 and 30 mM glucose and 30 mM glucose with 10(-6) to 10(-3) M captopril. Captopril decreased the cellular uptakes of d-glucose and alpha-methyl glucoside in the presence, but not in the absence, of sodium. The cellular size and contents of glucose, sorbitol, and fructose were increased in 30 mM glucose concomitant with the decreased thymidine, cellular DNA content, and ratios in glucose to sorbitol and to fructose, compared with those in 5 mM glucose. These changes observed in 30 mM glucose were reversed by 10(-4) M captopril. These data suggest that the suppression of d-glucose uptake through a sodium-coupled glucose transporter by captopril may attenuate the swelling and loss of pericytes observed in the early stage of diabetic retinopathy.