SGLT2 knockout prevents hyperglycemia and is associated with reduced pancreatic β-cell death in genetically obese mice

An Overview of the Cardiorenal Protective Mechanisms of SGLT2 Inhibitors

Sodium-glucose co-transporter 2 (SGLT2) inhibitors block glucose reabsorption in the renal proximal tubule, an insulin-independent mechanism that plays a critical role in glycemic regulation in diabetes. In addition to their glucose-lowering effects, SGLT2 inhibitors prevent both renal damage and the onset of chronic kidney disease and cardiovascular events, in particular heart failure with both reduced and preserved ejection fraction. These unexpected benefits prompted changes in treatment guidelines and scientific interest in the underlying mechanisms. Aside from the target effects of SGLT2 inhibition, a wide spectrum of beneficial actions is described for the kidney and the heart, even though the cardiac tissue does not express SGLT2 channels. Correction of cardiorenal risk factors, metabolic adjustments ameliorating myocardial substrate utilization, and optimization of ventricular loading conditions through effects on diuresis, natriuresis, and vascular function appear to be the main underlying mechanisms for the observed cardiorenal protection. Additional clinical advantages associated with using SGLT2 inhibitors are antifibrotic effects due to correction of inflammation and oxidative stress, modulation of mitochondrial function, and autophagy. Much research is required to understand the numerous and complex pathways involved in SGLT2 inhibition. This review summarizes the current known mechanisms of SGLT2-mediated cardiorenal protection.

SGLT2 inhibitors therapy protects glucotoxicity-induced β-cell failure in a mouse model of human KATP-induced diabetes through mitigation of oxidative and ER stress

Progressive loss of pancreatic β-cell functional mass and anti-diabetic drug responsivity are classic findings in diabetes, frequently attributed to compensatory insulin hypersecretion and β-cell exhaustion. However, loss of β-cell mass and identity still occurs in mouse models of human KATP-gain-of-function induced Neonatal Diabetes Mellitus (NDM), in the absence of insulin secretion. Here we studied the temporal progression and mechanisms underlying glucotoxicity-induced loss of functional β-cell mass in NDM mice, and the effects of sodium-glucose transporter 2 inhibitors (SGLT2i) therapy. Upon tamoxifen induction of transgene expression, NDM mice rapidly developed severe diabetes followed by an unexpected loss of insulin content, decreased proinsulin processing and increased proinsulin at 2-weeks of diabetes. These early events were accompanied by a marked increase in β-cell oxidative and ER stress, without changes in islet cell identity. Strikingly, treatment with the SGLT2 inhibitor dapagliflozin restored insulin content, decreased proinsulin:insulin ratio and reduced oxidative and ER stress. However, despite reduction of blood glucose, dapagliflozin therapy was ineffective in restoring β-cell function in NDM mice when it was initiated at >40 days of diabetes, when loss of β-cell mass and identity had already occurred. Our data from mouse models demonstrate that: i) hyperglycemia per se, and not insulin hypersecretion, drives β-cell failure in diabetes, ii) recovery of β-cell function by SGLT2 inhibitors is potentially through reduction of oxidative and ER stress, iii) SGLT2 inhibitors revert/prevent β-cell failure when used in early stages of diabetes, but not when loss of β-cell mass/identity already occurred, iv) common execution pathways may underlie loss and recovery of β-cell function in different forms of diabetes. These results may have important clinical implications for optimal therapeutic interventions in individuals with diabetes, particularly for those with long-standing diabetes.

Empagliflozin protects diabetic pancreatic tissue from damage by inhibiting the activation of the NLRP3/caspase-1/GSDMD pathway in pancreatic β cells: in vitro and in vivo studies

Diabetes mellitus is an important public health problem worldwide. Insulin deficiency caused by pancreatic β cell dysfunction is an important pathogenic factor of diabetes mellitus. This study evaluated whether empagliflozin (EMPA) protects the pancreas from diabetes mellitus-induced injury by downregulating the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3)/caspase-1/Gasdermin D (GSDMD) pyroptosis-related inflammasome pathway in vitro and in vivo. In vivo, animals were separated into blank control (control, C57/bl6j wild-type mice), diabetes model (db/db mice, BKS-Leprem2Cd479/Gpt mice), and db/db mice+EMPA (db/db+EMPA) groups. In vitro, pancreatic β cells were separated into low glucose (control), high glucose (HG), and HG+EMPA groups. The db/db+EMPA group were administered empagliflozin at 10 mg/(kg·day) by gavage for six months. Histological changes in the pancreatic tissues were observed by hematoxylin-eosin staining, and levels of the pyroptosis-related inflammatory factors NLPR3, caspase-1, and GSDMD were measured by immunohistochemistry and immunofluorescence staining methods. The Cell Counting Kit-8 assay was used to detect the effect of different concentrations of glucose and empagliflozin on the proliferation of mouse insulinoma islet β (β TC-6) cells. NLRP3/caspase-1/GSDMD expression was assessed by western blotting and immunofluorescent labeling in the β TC-6 cells. The results showed that empagliflozin reduced the pathological changes and inflammatory cell infiltration in the pancreatic tissues of db/db mice. Furthermore, empagliflozin not only reduced the expression levels of NLRP3/caspase-1/GSDMD in vitro, but also reduced their expression levels in vivo. In summary, our data suggested that empagliflozin protects the pancreatic tissues from diabetes mellitus-induced injury by downregulating the NLRP3/caspase-1/GSDMD pyroptosis-related inflammasome pathway.

Sodium-Glucose Cotransporter-2 Inhibitors Improve Cardiovascular Dysfunction in Type 2 Diabetic East Asians

In East Asians, the incidence of type 2 DM (T2DM) has increased as a result of major alterations in life. Cardiovascular problems are more likely in those with T2DM. Sodium-glucose cotransporter-2 (SGLT2) inhibitors are novel insulin-independent antihyperglycemic drugs that limit renal glucose reabsorption and thereby improve glycemic control. They are used alone or in combination with insulin and other antihyperglycemic medications to treat diabetes, and they are also helpful in protecting against the progression of complications. This review has evaluated the available evidence not only on the efficacy of SGLT2 inhibitors in T2DM, but also on their favourable cardiovascular events in East Asians. DM is an independent risk factor for cardiovascular diseases. As a result, in addition to glycemic control in diabetes management, the therapeutic goal in East Asian diabetic patients should be to improve adverse cardiovascular outcomes. Besides establishing antidiabetic effects, several studies have reported cardioprotective benefits of SGLT2 inhibitors via numerous pathways. SGLT2 inhibitors show promising antidiabetic drugs with potential cardiovascular advantages, given that a high number of diabetic patients in East Asia have co-existing cardiovascular disorders. Despite significant positive results in favour of SGLT2, more research is needed to determine how SGLT2 inhibitors exert these impressive cardiovascular effects.

Sodium-Glucose Cotransporter-2 Inhibitors in Vascular Biology: Cellular and Molecular Mechanisms

Sodium-glucose cotransporter-2 (SGLT2) inhibitors are new antidiabetic drugs that reduce hyperglycemia by inhibiting the glucose reabsorption in renal proximal tubules. Clinical studies have shown that SGLT2 inhibitors not only improve glycemic control but also reduce major adverse cardiovascular events (MACE, cardiovascular and total mortality, fatal or nonfatal myocardial infarction or stroke) and hospitalization for heart failure (HF), and improve outcome in chronic kidney disease. These cardiovascular and renal benefits have now been confirmed in both diabetes and non-diabetes patients. The precise mechanism(s) responsible for the protective effects are under intensive investigation. This review examines current evidence on the cardiovascular benefits of SGLT2 inhibitors, with a special emphasis on the vascular actions and their potential mechanisms.

Novel Approaches to Restore Pancreatic Beta-Cell Mass and Function

Beta-cell dysfunction and beta-cell death are critical events in the development of type 2 diabetes mellitus (T2DM). Therefore, the goals of modern T2DM management have shifted from merely restoring normoglycemia to maintaining or regenerating beta-cell mass and function. In this review we summarize current and novel approaches to achieve these goals, ranging from lifestyle interventions to N-methyl-D-aspartate receptor (NMDAR) antagonism, and discuss the mechanisms underlying their effects on beta-cell physiology and glycemic control. Notably, timely intervention seems critical, but not always strictly required, to maximize the effect of any approach on beta-cell recovery and disease progression. Conventional antidiabetic medications are not disease-modifying in the sense that the disease does not progress or reoccur while on treatment or thereafter. More invasive approaches, such as bariatric surgery, are highly effective in restoring normoglycemia, but are reserved for a rather small proportion of obese individuals and sometimes associated with serious adverse events. Finally, we recapitulate the broad range of effects mediated by peripheral NMDARs and discuss recent evidence on the potential of NMDAR antagonists to be developed as a novel class of antidiabetic drugs. In the future, a more refined assessment of disease risk or disease subtype might enable more targeted therapies to prevent or treat diabetes.

An Overview of Similarities and Differences in Metabolic Actions and Effects of Central Nervous System Between Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) and Sodium Glucose Co-Transporter-2 Inhibitors (SGLT-2is)

GLP-1 receptor agonists (GLP-1RAs) and SGLT-2 inhibitors (SGLT-2is) are novel antidiabetic medications associated with considerable cardiovascular benefits therapying treatment of diabetic patients. GLP-1 exhibits atherosclerosis resistance, whereas SGLT-2i acts to ameliorate the neuroendocrine state in the patients with chronic heart failure. Despite their distinct modes of action, both factors share pathways by regulating the central nervous system (CNS). While numerous preclinical and clinical studies have demonstrated that GLP-1 can access various nuclei associated with energy homeostasis and hedonic eating in the CNS via blood-brain barrier (BBB), research on the activity of SGLT-2is remains limited. In our previous studies, we demonstrated that both GLP-1 receptor agonists (GLP-1RAs) liraglutide and exenatide, as well as an SGLT-2i, dapagliflozin, could activate various nuclei and pathways in the CNS of Sprague Dawley (SD) rats and C57BL/6 mice, respectively. Moreover, our results revealed similarities and differences in neural pathways, which possibly regulated different metabolic effects of GLP-1RA and SGLT-2i via sympathetic and parasympathetic systems in the CNS, such as feeding, blood glucose regulation and cardiovascular activities (arterial blood pressure and heart rate control). In the present article, we extensively discuss recent preclinical studies on the effects of GLP-1RAs and SGLT-2is on the CNS actions, with the aim of providing a theoretical explanation on their mechanism of action in improvement of the macro-cardiovascular risk and reducing incidence of diabetic complications. Overall, these findings are expected to guide future drug design approaches.

Durability of glycaemic control in type 2 diabetes: A systematic review and meta-analysis for its association with body weight changes

AIMS

To analyse quantitatively the association between the durability of glycaemic control and body weight changes during treatment.

MATERIALS AND METHODS

This study adhered to an appropriate methodology according to Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. Studies with follow-ups >12 months, and final and intermediate assessments of haemoglobin A1c (HbA1c) and body weight were included. Four outcomes assessing therapeutic durability were extracted and synthesized using Stata statistical software, including changes in HbA1c, goal-achievement rate, failure rate and coefficient of failure (CoF).

RESULTS

After 8.9 months of treatment, HbA1c levels declined from 8.03% [95% confidence interval (CI), 7.91-8.15; I² = 99.2%] to 7.15% (95% CI, 7.02-7.27; I² = 99.4%) and then gradually increased up to 7.72% (95% CI, 7.50-7.94; I² = 99.0%) 5 years later. The goal-achievement rate decreased from 54.8% (after 1 year of treatment) to 19.4% 5 years later. The CoF was 0.123 ± 0.022%/year (P < .001). After stratification, the CoFs were 0.224 ± 0.025%/year (P < .001) for weight gain, 0.137 ± 0.034%/year (P < .001) for neutral weight and -0.024 ± 0.032%/year (P = .450) for weight loss. After stratification by treatment approaches, the CoFs were 0.45%/year for insulin, 0.43%/year for sulphonylurea, 0.34%/year for thiazolidinediones, 0.29%/year for metformin, 0.16% for glucagon-like polypeptide-1 receptor agonists, 0.12% for surgery, -0.03% for sodium-glucose cotransporter-2 inhibitors and -0.21% for dipeptidyl peptidase-IV inhibitors.

CONCLUSION

Modest weight loss with a goal of 2-3% of body weight should be recommended to improve therapeutic durability and prevent beta-cell deterioration.

Solute Carrier Transporters as Potential Targets for the Treatment of Metabolic Disease

The solute carrier (SLC) superfamily comprises more than 400 transport proteins mediating the influx and efflux of substances such as ions, nucleotides, and sugars across biological membranes. Over 80 SLC transporters have been linked to human diseases, including obesity and type 2 diabetes (T2D). This observation highlights the importance of SLCs for human (patho)physiology. Yet, only a small number of SLC proteins are validated drug targets. The most recent drug class approved for the treatment of T2D targets sodium-glucose cotransporter 2, product of the SLC5A2 gene. There is great interest in identifying other SLC transporters as potential targets for the treatment of metabolic diseases. Finding better treatments will prove essential in future years, given the enormous personal and socioeconomic burden posed by more than 500 million patients with T2D by 2040 worldwide. In this review, we summarize the evidence for SLC transporters as target structures in metabolic disease. To this end, we identified SLC13A5/sodium-coupled citrate transporter, and recent proof-of-concept studies confirm its therapeutic potential in T2D and nonalcoholic fatty liver disease. Further SLC transporters were linked in multiple genome-wide association studies to T2D or related metabolic disorders. In addition to presenting better-characterized potential therapeutic targets, we discuss the likely unnoticed link between other SLC transporters and metabolic disease. Recognition of their potential may promote research on these proteins for future medical management of human metabolic diseases such as obesity, fatty liver disease, and T2D. SIGNIFICANCE STATEMENT: Given the fact that the prevalence of human metabolic diseases such as obesity and type 2 diabetes has dramatically risen, pharmacological intervention will be a key future approach to managing their burden and reducing mortality. In this review, we present the evidence for solute carrier (SLC) genes associated with human metabolic diseases and discuss the potential of SLC transporters as therapeutic target structures.

Sodium-glucose cotransporter-2 inhibitors: Understanding the mechanisms for therapeutic promise and persisting risks

In a healthy person, the kidney filters nearly 200 g of glucose per day, almost all of which is reabsorbed. The primary transporter responsible for renal glucose reabsorption is sodium-glucose cotransporter-2 (SGLT2). Based on the impact of SGLT2 to prevent renal glucose wasting, SGLT2 inhibitors have been developed to treat diabetes and are the newest class of glucose-lowering agents approved in the United States. By inhibiting glucose reabsorption in the proximal tubule, these agents promote glycosuria, thereby reducing blood glucose concentrations and often resulting in modest weight loss. Recent work in humans and rodents has demonstrated that the clinical utility of these agents may not be limited to diabetes management: SGLT2 inhibitors have also shown therapeutic promise in improving outcomes in heart failure, atrial fibrillation, and, in preclinical studies, certain cancers. Unfortunately, these benefits are not without risk: SGLT2 inhibitors predispose to euglycemic ketoacidosis in those with type 2 diabetes and, largely for this reason, are not approved to treat type 1 diabetes. The mechanism for each of the beneficial and harmful effects of SGLT2 inhibitors-with the exception of their effect to lower plasma glucose concentrations-is an area of active investigation. In this review, we discuss the mechanisms by which these drugs cause euglycemic ketoacidosis and hyperglucagonemia and stimulate hepatic gluconeogenesis as well as their beneficial effects in cardiovascular disease and cancer. In so doing, we aim to highlight the crucial role for selecting patients for SGLT2 inhibitor therapy and highlight several crucial questions that remain unanswered.

Endocrine-Exocrine Signaling Drives Obesity-Associated Pancreatic Ductal Adenocarcinoma

Obesity is a major modifiable risk factor for pancreatic ductal adenocarcinoma (PDAC), yet how and when obesity contributes to PDAC progression is not well understood. Leveraging an autochthonous mouse model, we demonstrate a causal and reversible role for obesity in early PDAC progression, showing that obesity markedly enhances tumorigenesis, while genetic or dietary induction of weight loss intercepts cancer development. Molecular analyses of human and murine samples define microenvironmental consequences of obesity that foster tumorigenesis rather than new driver gene mutations, including significant pancreatic islet cell adaptation in obesity-associated tumors. Specifically, we identify aberrant beta cell expression of the peptide hormone cholecystokinin (Cck) in response to obesity and show that islet Cck promotes oncogenic Kras-driven pancreatic ductal tumorigenesis. Our studies argue that PDAC progression is driven by local obesity-associated changes in the tumor microenvironment and implicate endocrine-exocrine signaling beyond insulin in PDAC development.