[Roles of Sodium-Glucose Cotransporter 1 (SGLT1) in the Induction of Cardiac Remodeling]

The Off-Target Cardioprotective Mechanisms of Sodium-Glucose Cotransporter 2 Inhibitors: An Overview

Sodium-glucose cotransporter 2 inhibitors (SGLT2i), a novel class of glucose-lowering drugs, have revolutionized the management of heart failure with reduced and preserved ejection fraction, regardless of the presence of diabetes, and are currently incorporated in the heart failure guidelines. While these drugs have consistently demonstrated their ability to decrease heart failure hospitalizations in several landmark clinical trials, their cardioprotective effects are far from having been completely elucidated. In the past decade, a growing body of experimental research has sought to address the molecular and cellular mechanisms of SGLT2i in order to provide a better understanding of the off-target acute and chronic cardiac benefits, beyond the on-target renal effect responsible for blood glucose reduction. The present narrative review addresses the direct cardioprotective effects of SGLT2i, delving into the off-target mechanisms of the drugs currently approved for heart failure therapy, and provides insights into future perspectives.

Canagliflozin and Dapagliflozin Attenuate Glucolipotoxicity-Induced Oxidative Stress and Apoptosis in Cardiomyocytes via Inhibition of Sodium-Glucose Cotransporter-1

Sodium-dependent glucose cotransporter 2 inhibitors (SGLT2) are recently approved drugs for the treatment of diabetes that regulate blood glucose levels by inhibiting reabsorption of glucose and sodium in the proximal tubules of the kidney. SGLT2 inhibitors have also shown cardiovascular (CV) benefits in diabetic patients. However, the therapeutic efficacy of SGLT2 inhibitors with respect to CV disease needs further investigation. Thus, the aim of the present study was to examine the effects of SGLT2 inhibitors, canagliflozin (CANA) and dapagliflozin (DAPA) in vitro under glucolipotoxic condition by treating cultured cardiomyocytes (H9C2) with high glucose (HG) and high lipid, palmitic acid (PA), to investigate whether inhibition of sodium glucose cotransporter could prevent any harmful effects of glucolipotoxicity in these cells. SGLT1 expression was measured by immunofluorescence staining and quantitative polymerase chain reaction. Oxidative stress and apoptosis were measured by flow cytometry. Hypertrophy was measured by hematoxylin and eosin (H&E) and crystal violet staining. A significant increase in SGLT1 expression was observed in HG- and PA-treated cardiomyocytes. Also, a significant increase in reactive oxygen species generation and apoptosis was observed in HG+PA-treated cultured cardiomyocytes. HG- and PA-treated cardiomyocytes developed significant structural alterations. All these effects of HG and PA were attenuated by CANA and DAPA. In conclusion, our study demonstrates upregulation of SGLT1 induces oxidative stress and apoptosis in cultured cardiomyocytes. Thus, inhibition of SGLT1 may be used as a possible approach for the treatment of CVD in diabetic patients.

SGLT1 Knockdown Attenuates Cardiac Fibroblast Activation in Diabetic Cardiac Fibrosis

Background: Cardiac fibroblast (CF) activation is a hallmark feature of cardiac fibrosis in diabetic cardiomyopathy (DCM). Inhibition of the sodium-dependent glucose transporter 1 (SGLT1) attenuates cardiomyocyte apoptosis and delays the development of DCM. However, the role of SGLT1 in CF activation remains unclear.

Methods: A rat model of DCM was established and treated with si‐SGLT1 to examine cardiac fibrosis. In addition, in vitro experiments were conducted to verify the regulatory role of SGLT1 in proliferation and collagen secretion in high-glucose– (HG–) treated CFs.

Results: SGLT1 was found to be upregulated in diabetic cardiac tissues and HG-induced CFs. HG stimulation resulted in increased proliferation and migration, increased the expression of transforming growth factor-β1 and collagen I and collagen III, and increased phosphorylation of p38 mitogen-activated protein kinase and extracellular signal-regulated kinase (ERK) 1/2. These trends in HG-treated CFs were significantly reversed by si-SGLT1. Moreover, the overexpression of SGLT1 promoted CF proliferation and collagen synthesis and increased phosphorylation of p38 mitogen-activated protein kinase and ERK1/2. SGLT1 silencing significantly alleviated cardiac fibrosis, but had no effect on cardiac hypertrophy in diabetic hearts.

Conclusion: These findings provide new information on the role of SGLT1 in CF activation, suggesting a novel therapeutic strategy for the treatment of DCM fibrosis.

SGLT1 Inhibition Attenuates Apoptosis in Diabetic Cardiomyopathy via the JNK and p38 Pathway

Background: Recent studies have revealed that a novel selective sodium-glucose cotransporter 1 (SGLT1) inhibiton has shown beneficial effects in cardiovascular diseases. However, the question of whether SGLT1 inhibition influences diabetic cardiomyopathy (DCM) remains unanswered. In this study, we investigated the influence and underlying mechanism of SGLTI inhibition on DCM. Methods: SGLT1 levels were measured in diabetic patients with similar conditions who visited our hospital from January to December 2019. Wistar male rats (n = 50) were divided into five groups: control, diabetes induced by streptozotocin infusion, and diabetes treated with 0.5, 1.0, or 1.5 mg/kg mizagliflozin via stomach gavage for 12 weeks. H9C2 cardiomyocytes were treated with mizagliflozin and then exposed to a high glucose concentration (30 mmol/L). TUNEL assays were performed, and bcl2, bax, p-p38, p-Erk, p-JNK and caspase-3 levels were measured. We used siRNA and an SGLT1 overexpression plasmid to detect the effects of SGLT1. Results: SGLT1 levels were significantly elevated in DCM patients, and receiver operating characteristic (ROC) curve analysis identified SGLT1 as influencing DCM. The area under the curve (AUC) was 0.705 (p < 0.05), with 65.8% sensitivity, and 62.2% specificity. SGLT1 inhibition appeared to attenuate apoptosis in DCM via the JNK and p38 pathway. Conclusion: SGLT1 can be used as a marker for the diagnosis of DCM, and SGLT1 inhibition can attenuate apoptosis, thereby suppressing DCM development via the JNK and p38 pathway.

Synthesis and Structure-Activity Relationship of C-Phenyl D-Glucitol (TP0454614) Derivatives as Selective Sodium-Dependent Glucose Cotransporter 1 (SGLT1) Inhibitors

Sodium-glucose cotransporter 1 (SGLT1) is the primary transporter for glucose absorption from the gastrointestinal tract. While C-phenyl D-glucitol derivative SGL5213 has been reported to be a potent intestinal SGLT1 inhibitor for use in the treatment of type 2 diabetes, no SGLT1 selectivity was found in vitro (IC₅₀ 29 nM for hSGLT1 and 20 nM for hSGLT2). In this study we found a new method of synthesizing key intermediates 12 by a one-pot three-component condensation reaction and discovered C-phenyl D-glucitol 41j (TP0454614), which has >40-fold SGLT1 selectivity in vitro (IC₅₀ 26 nM for hSGLT1 and 1101 nM for hSGLT2). The results of our study have provided new insights into the structure-activity relationships (SARs) of the SGLT1 selectivity of C-glucitol derivatives.