New Antihyperglycemic Drugs and Heart Failure: Synopsis of Basic and Clinical Data

Empagliflozin protects heart from inflammation and energy depletion via AMPK activation

AIMS

Sodium-glucose co-transporter 2 (SGLT2) were originally developed as kidney-targeting anti-diabetic drugs. However, due to their beneficial cardiac off-target effects (as SGLT2 is not expressed in the heart), these antagonists currently receive intense clinical interest in the context of heart failure (HF) in patients with or without diabetes mellitus (DM). Since the mechanisms by which these beneficial effects are mediated are still unclear yet, inflammation that is present in DM and HF has been proposed as a potential pharmacological intervention strategy. Therefore, we tested the hypothesis that the SGLT2 inhibitor, empagliflozin, displays anti-inflammatory potential along with its glucose-lowering property.

METHODS AND RESULTS

Lipopolysaccharide (LPS) was used to induce inflammation in vitro and in vivo. In cardiomyocytes and macrophages empagliflozin attenuated LPS-induced TNFα and iNOS expression. Analysis of intracellular signalling pathways suggested that empagliflozin activates AMP kinase (AMPK) in both cell types with or without LPS-treatment. Moreover, the SGLT2 inhibitor increased the expression of anti-inflammatory M2 marker proteins in LPS-treated macrophages. Additionally, empagliflozin-mediated AMPK activation prevented LPS-induced ATP/ADP depletion. In vivo administration of LPS in mice impaired cardiac contractility and aortic endothelial relaxation in response to acetylcholine, whereby co-administration of empagliflozin preserved cardiovascular function. These findings were accompanied by improved cardiac AMPK phosphorylation and ATP/ADP, reduced cardiac iNOS, plasma TNFα and creatine kinase MB levels.

CONCLUSION

Our data identify a novel cardio protective mechanism of SGLT2 inhibitor, empagliflozin, suggesting that AMPK activation-mediated energy repletion and reduced inflammation contribute to the observed cardiovascular benefits of the drug in HF.

Rosiglitazone alleviates myocardial apoptosis in rats with acute myocardial infarction via inhibiting TLR4/NF-κB signaling pathway

Influence of rosiglitazone on the myocardial apoptosis in rats with acute myocardial infarction (AMI) via the Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling pathway was explored. A total of 30 healthy male Sprague-Dawley (SD) rats were randomly divided into group A (Sham group, n=10), group B (AMI model group, n=10) and group C (AMI model + rosiglitazone group, n=10) using a random number table. It was observed through H&E staining that group A had myocardial cells with normal morphology and infiltration of few inflammatory factors, while group B had swollen myocardial cells with disorderly and irregular morphology, large and dark-colored nuclei, infiltration of massive inflammatory factors, large amounts of fibrous tissue hyperplasia in the intercellular space, disorderly arranged, thickened and lengthened myocardial fibers with widened gaps. Moreover, group C exhibited infiltration of fewer inflammatory factors and more normal myocardial tissue structure compared with group B. According to the sirius-red staining results, group A had normally arranged myocardial cells with a small amount of collagen hyperplasia, while group B had collagen interstitial hyperplasia and higher content of myocardial collagen than group A. Compared with that in group B, the myocardial collagen deposit was substantially reduced in group C. TUNEL staining results showed that the apoptosis rate of rat myocardial cells in group B was obviously higher than that in group A (40.37 vs. 5.23%), and it was notably lower in group C than that in group B (24.82 vs. 40.37%). According to the western blot results, the protein expression levels of the inflammatory factors TLR-4 and NF-κB in rat myocardial tissues were notably raised in group B compared with those in group A, and they were evidently lower in group C than those in group B. Rosiglitazone inhibits the TLR4/NF-κB signaling pathway to produce a myocardioprotective effect.

The Effect of Glycemic Control on Endothelial and Cardiac Dysfunction Induced by Red Blood Cells in Type 2 Diabetes

Red blood cells (RBCs) from patients with type 2 diabetes mellitus (T2DM) induce endothelial dysfunction and impair cardiac function following ischemia via increase in RBC arginase and oxidative stress. Here, we aimed to elucidate whether the effect of RBC-mediated cardiac impairment following ischemia and endothelial dysfunction in T2DM is dependent on glycemic control. Patients with T2DM at poor glycemic control (T2DM PGC) and at improvement in glycemic control (T2DM IGC) and healthy subjects were recruited. Isolated RBCs from subjects were incubated with aortic rings from healthy wild-type rats with subsequent evaluation of endothelium-dependent relaxation (EDR) using wire myograph. Moreover, RBCs were administered to isolated wild-type rat hearts with subsequent evaluation of left ventricular developed pressure (LVDP) during reperfusion using Langendorff setup. In separate experiments, RBCs were preincubated with an arginase inhibitor before perfusion. Blood glucose and glycated hemoglobin were 33 and 26%, respectively, lower in T2DM IGC compared with those in T2DM PGC. RBCs from T2DM PGC and T2DM IGC impaired EDR to a similar magnitude compared with RBCs from healthy subjects. LVDP was significantly impaired in hearts given RBCs from T2DM PGC as compared with those from healthy subjects. The impairment of LVDP induced by T2DM PGC was attenuated by RBCs from T2DM IGC. Arginase inhibition improved LVDP to a similar extent between T2DM PGC and IGC groups. These observations indicate that glycemic control abrogate the impairment in postischemic recovery but not endothelial dysfunction induced by RBCs from T2DM. Moreover, inhibition of RBC arginase improves cardiac function irrespective of glycemic control.

Cardiomyopathy Associated with Diabetes: The Central Role of the Cardiomyocyte

The term diabetic cardiomyopathy (DCM) labels an abnormal cardiac structure and performance due to intrinsic heart muscle malfunction, independently of other vascular co-morbidity. DCM, accounting for 50%–80% of deaths in diabetic patients, represents a worldwide problem for human health and related economics. Optimal glycemic control is not sufficient to prevent DCM, which derives from heart remodeling and geometrical changes, with both consequences of critical events initially occurring at the cardiomyocyte level. Cardiac cells, under hyperglycemia, very early undergo metabolic abnormalities and contribute to T helper (Th)-driven inflammatory perturbation, behaving as immunoactive units capable of releasing critical biomediators, such as cytokines and chemokines. This paper aims to focus onto the role of cardiomyocytes, no longer considered as “passive” targets but as “active” units participating in the inflammatory dialogue between local and systemic counterparts underlying DCM development and maintenance. Some of the main biomolecular/metabolic/inflammatory processes triggered within cardiac cells by high glucose are overviewed; particular attention is addressed to early inflammatory cytokines and chemokines, representing potential therapeutic targets for a prompt early intervention when no signs or symptoms of DCM are manifesting yet. DCM clinical management still represents a challenge and further translational investigations, including studies at female/male cell level, are warranted.

Diabetic Cardiomyopathy: Current and Future Therapies. Beyond Glycemic Control

Diabetes mellitus and the associated complications represent a global burden on human health and economics. Cardiovascular diseases are the leading cause of death in diabetic patients, who have a 2–5 times higher risk of developing heart failure than age-matched non-diabetic patients, independent of other comorbidities. Diabetic cardiomyopathy is defined as the presence of abnormal cardiac structure and performance in the absence of other cardiac risk factors, such coronary artery disease, hypertension, and significant valvular disease. Hyperglycemia, hyperinsulinemia, and insulin resistance mediate the pathological remodeling of the heart, characterized by left ventricle concentric hypertrophy and perivascular and interstitial fibrosis leading to diastolic dysfunction. A change in the metabolic status, impaired calcium homeostasis and energy production, increased inflammation and oxidative stress, as well as an accumulation of advanced glycation end products are among the mechanisms implicated in the pathogenesis of diabetic cardiomyopathy. Despite a growing interest in the pathophysiology of diabetic cardiomyopathy, there are no specific guidelines for diagnosing patients or structuring a treatment strategy in clinical practice. Anti-hyperglycemic drugs are crucial in the management of diabetes by effectively reducing microvascular complications, preventing renal failure, retinopathy, and nerve damage. Interestingly, several drugs currently in use can improve cardiac health beyond their ability to control glycemia. GLP-1 receptor agonists and sodium-glucose co-transporter 2 inhibitors have been shown to have a beneficial effect on the cardiovascular system through a direct effect on myocardium, beyond their ability to lower blood glucose levels. In recent years, great improvements have been made toward the possibility of modulating the expression of specific cardiac genes or non-coding RNAs in vivo for therapeutic purpose, opening up the possibility to regulate the expression of key players in the development/progression of diabetic cardiomyopathy. This review summarizes the pathogenesis of diabetic cardiomyopathy, with particular focus on structural and molecular abnormalities occurring during its progression, as well as both current and potential future therapies.

Revisiting the Diabetes-Heart Failure Connection

PURPOSE OF THE REVIEW

To summarize current clinical data investigating the link between diabetes and heart failure pathophysiology, the association of glucose control with heart failure, and the impact of current antihyperglycemic drugs on heart failure.

RECENT FINDINGS

Although heart failure is one of the most prevalent outcomes occurring in real life and cardiovascular outcome trials, insufficient attention was given to this condition in diabetes research over the last decades. With both beneficial and detrimental findings for heart failure hospitalization in the health authority-mandated outcome trials for new antihyperglycemic agents, research on heart failure and its interplay with diabetes mellitus gained momentum. Diabetes mellitus and heart failure are both prevalent and intertwined conditions. While currently available heart failure therapies have a similar degree of effectiveness in patients with and without diabetes, the choice of glucose-lowering agents can substantially affect heart failure-related outcome.

Potential mechanisms responsible for cardioprotective effects of sodium-glucose co-transporter 2 inhibitors

Diabetes mellitus currently affects over 350 million patients worldwide and is associated with many deaths from cardiovascular complications. Sodium-glucose co-transporter 2 (SGLT-2) inhibitors are a novel class of antidiabetic drugs with cardiovascular benefits beyond other antidiabetic drugs. In the EMPA-REG OUTCOME trial, empagliflozin significantly decreases the mortality rate from cardiovascular causes [38% relative risk reduction (RRR)], the mortality rate from all-causes (32% RRR) and the rate of heart failure hospitalization (35% RRR) in diabetic patients with established cardiovascular diseases. The possible mechanisms of SGLT-2 inhibitors are proposed to be systemic effects by hemodynamic and metabolic actions. However, the direct mechanisms are not fully understood. In this review, reports concerning the effects of SGLT-2 inhibitors in models of diabetic cardiomyopathy, heart failure and myocardial ischemia from in vitro, in vivo as well as clinical reports are comprehensively summarized and discussed. By current evidences, it may be concluded that the direct effects of SGLT-2 inhibitors are potentially mediated through their ability to reduce cardiac inflammation, oxidative stress, apoptosis, mitochondrial dysfunction and ionic dyshomeostasis.