Cardioprotective effect of empagliflozin in acute myocardial infarction: the role of ketone bodies availability

Background

The cardio-renal benefits of SGLT2i have been clearly established by clinical trials. Of interest, despite not having any effect on the incidence of classic atherothrombotic events (MI and strokes), patients receiving SGLT2i treatment had a higher chance of surviving myocardial infarction (MI).

Purpose

We aim to evaluate the cardioprotective potential of empagliflozin on acute myocardial infarction.

We postulate that the benefits of SGLT2-I are mediated via an increase in circulating ketone bodies (KBs) induced by SGLT2i, and its preferential myocardial utilization energetically benefits the heart to better withstand an ischemic event.

Methods

The study was undertaken in our non-diabetic porcine model of ischemia/reperfusion. Animals were allocated to either one-week pre-treatment with empagliflozin or placebo before MI-induction. A third group received IV infusion of KBs at the time of the MI- induction to serve as positive-control. The acute effects of the treatments were studied 24 hours after MI-induction by Cardiac Magnetic Resonance (CMR). Immediately post-CMR, animals were sacrificed and heart samples collected for molecular analysis.

Results

(see Table and Figure): Despite similar initial ischemic injury (area at risk) in all groups, empagliflozin was associated with a significantly higher myocardial salvage (MSI 23.7±9.7 vs 4.5±3.6%, p<0.001) and better preserved cardiac function (LVEF 41.3±3.1 vs 33±5.5%, p<0.009) compared with placebo. The infusion of KBs replicated in part the beneficial profile of the empagliflozin group (MSI 16.7±8.8 and LVEF 39.1±3.6%). Histological analysis showed less cardiomyocyte apoptosis and less oxidative stress

Conclusions

To the best of our knowledge, this is the first study evaluating in vivo the cardioprotective potential of a SGLT2 inhibitor in a well-stablished porcine translational model. Furthermore, effects are evaluated using the gold standard for visualization and quantification of MI, Cardiac Magnetic Resonance (CMR). Three are the main conclusions:

1. One-week treatment with empagliflozin raises circulating KBs levels and confers significant cardio-protection during a myocardial infarction. Acute post-MI benefits (greater myocardial salvage and better preserved cardiac function) are already seen within 24 hours as compared with placebo.

2. Periprocedural IV infusion of KBs induces similar benefits than the SGLT2-I group.

3. These observations strongly support our hypothesis that SGLT2 inhibition is associated with increased circulating KBs and its selective use as preferential myocardial source of energy as a potential mechanism of action involved in the cardio-renal benefits observed with SGLT2i.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Spanish Society of Cardiology. Research Fellowship Grant.

Complement C5 plasma levels are associated to abdominal aortic aneurysm prevalence and progression

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Complemento II-CM

La Caixa

Aim

Previous human and experimental studies have suggested a role of complement activation in abdominal aortic aneurysm (AAA).  We recently described an increase in complement C5 levels in plasma of subjects with subclinical atherosclerosis (1). Our aim was to investigate the potential association of C5 with AAA presence and progression.

Material and methods

Tissue and tissue-conditioned media from AAA (thrombus and wall) or healthy samples were obtained from surgical repair or brain-deceased organ donors, respectively. Blood samples from 490 AAA patients (maximal aortic diameter ≥30 mm) were obtained within a population-based ultrasound-screening trial in Danish men and from 176 age-matched screened negative controls. C5 protein levels were assessed by immunohistochemistry and ELISA.

Results

High C5 positive immunostaining was observed in AAA thrombus and media, while the staining in healthy arteries was faint. C5 levels were higher in tissue-conditioned media from AAA thrombus and AAA media as compared to healthy arteries (7.1±1 vs 2.9 ±0.5 vs 1.2±0.2ug/ml, p<0.0001 for both). C5 plasma levels in AAA patients were higher than in controls (116±8 vs 61±7 ug/ml, P<0.001). AAA patients at the upper tertile of C5 at baseline had a 25% higher risk of needing surgical repair during the follow-up (Hazard Ratio=1.25, 95% confidence interval, 1.045;1.511, P<0.05).

Conclusions

C5 is associated to AAA presence and progression suggesting its potential use as a prognostic marker. Future studies are needed to clarify the pathogenic role of C5 in AAA.

Sitagliptin improved glucose assimilation in detriment of fatty-acid utilization in experimental type-II diabetes: role of GLP-1 isoforms in Glut4 receptor trafficking

BACKGROUND

The distribution of glucose and fatty-acid transporters in the heart is crucial for energy consecution and myocardial function. In this sense, the glucagon-like peptide-1 (GLP-1) enhancer, sitagliptin, improves glucose homeostasis but it could also trigger direct cardioprotective actions, including regulation of energy substrate utilization.

METHODS

Type-II diabetic GK (Goto-Kakizaki), sitagliptin-treated GK (10 mg/kg/day) and wistar rats (n = 10, each) underwent echocardiographic evaluation, and positron emission tomography scanning for [¹⁸F]-2-fluoro-2-deoxy-D-glucose (¹⁸FDG). Hearts and plasma were isolated for biochemical approaches. Cultured cardiomyocytes were examined for receptor distribution after incretin stimulation in high fatty acid or high glucose media.

RESULTS

Untreated GK rats exhibited hyperglycemia, hyperlipidemia, insulin resistance, and plasma GLP-1 reduction. Moreover, GK myocardium decreased ¹⁸FDG assimilation and diastolic dysfunction. However, sitagliptin improved hyperglycemia, insulin resistance, and GLP-1 levels, and additionally, enhanced ¹⁸FDG uptake and diastolic function. Sitagliptin also stimulated the sarcolemmal translocation of the glucose transporter-4 (Glut4), in detriment of the fatty acyl translocase (FAT)/CD36. In fact, Glut4 mRNA expression and sarcolemmal translocation were also increased after GLP-1 stimulation in high-fatty acid incubated cardiomyocytes. PI3K/Akt and AMPKα were involved in this response. Intriguingly, the GLP-1 degradation metabolite, GLP-1(9-36), showed similar effects.

CONCLUSIONS

Besides of its anti-hyperglycemic effect, sitagliptin-enhanced GLP-1 may ameliorate diastolic dysfunction in type-II diabetes by shifting fatty acid to glucose utilization in the cardiomyocyte, and thus, improving cardiac efficiency and reducing lipolysis.

Updating experimental models of diabetic cardiomyopathy

Diabetic cardiomyopathy entails a serious cardiac dysfunction induced by alterations in structure and contractility of the myocardium. This pathology is initiated by changes in energy substrates and occurs in the absence of atherothrombosis, hypertension, or other cardiomyopathies. Inflammation, hypertrophy, fibrosis, steatosis, and apoptosis in the myocardium have been studied in numerous diabetic experimental models in animals, mostly rodents. Type I and type II diabetes were induced by genetic manipulation, pancreatic toxins, and fat and sweet diets, and animals recapitulate the main features of human diabetes and related cardiomyopathy. In this review we update and discuss the main experimental models of diabetic cardiomyopathy, analysing the associated metabolic, structural, and functional abnormalities, and including current tools for detection of these responses. Also, novel experimental models based on genetic modifications of specific related genes have been discussed. The study of specific pathways or factors responsible for cardiac failures may be useful to design new pharmacological strategies for diabetic patients.

Proteome changes in the myocardium of experimental chronic diabetes and hypertension: role of PPARα in the associated hypertrophy

Diabetes with or without the presence of hypertension damages the heart. However, there is currently a lack of information about these associated pathologies and the alteration of linked proteins. For these reasons, we were interested in the potential synergistic interaction of diabetes and hypertension in the heart, focusing on the proteome characterization of the pathological phenotypes and the associated hypertrophic response. We treated normotensive and spontaneously hypertensive (SHR) rats with either streptozotocin or vehicle. After 22weeks, type-I diabetic (DM1), SHR, SHR/DM1 and control left-ventricles were studied using proteomic approaches. Proteomics revealed that long-term DM1, SHR and SHR/DM1 rats exhibited 24, 53 and 53 altered proteins in the myocardia, respectively. DM1 myocardium showed over-expression of apoptotic and cytoskeleton proteins, and down-regulation of anti-apoptotic and mitochondrial metabolic enzymes. In both SHR and SHR/DM1 these changes were exacerbated and free fatty-acid (FFA) ß-oxidation enzymes were additionally decreased. Furthermore, SHR/DM1 hearts exhibited a misbalance of specific pro-hypertrophic, anti-apoptotic and mitochondrial ATP-carrier factors, which could cause additional damage. Differential proteins were validated and then clustered into different biological pathways using bioinformatics. These studies suggested the implication of FFA-nuclear receptors and hypertrophic factors in these pathologies. Although key ß-oxidation enzymes were not stimulated in DM1 and hypertensive hearts, peroxisome proliferator-activated receptors-α (PPARα) were potentially activated for other responses. In this regard, PPARα stimulation reduced hypertrophy and pro-hypertrophic factors such as annexin-V in high-glucose and angiotensin-II induced cardiomyocytes. Thus, activation of PPARα could reflect a compensatory response to the metabolic-shifted, apoptotic and hypertrophic status of the hypertensive-diabetic cardiomyopathy.

Myocardial fibrosis and apoptosis, but not inflammation, are present in long-term experimental diabetes

The aim of this paper is to study the myocardial damage secondary to long-term streptozotocin-induced type 1 diabetes mellitus (DM1). Normotensive and spontaneously hypertensive rats (SHR) received either streptozotocin injections or vehicle. After 22 or 6 wk, DM1, SHR, DM1/SHR, and control rats were killed, and the left ventricles studied by histology, quantitative PCR, Western blot, ELISA, and electromobility shift assay. Cardiomyocyte cultures were also performed. The expression of profibrotic factors, transforming growth factor-β (TGF-β1), connective tissue growth factor, and matrix proteins was increased, and the TGF-β1-linked transcription factors phospho-Smad3/4 and activator protein-1 were activated in the DM1 myocardium. Proapoptotic molecules FasL, Fas, Bax, and cleaved caspase-3 were also augmented. Myocardial injury in long-term hypertension shared these features. In addition, hypertension was associated with activation of NF-κB, increased inflammatory cell infiltrate, and expression of the mediators [interleukin-1β (IL-1β), tumor necrosis factor-α, monocyte chemoattractant protein 1, vascular cell adhesion molecule 1, angiotensinogen, and oxidants], which were absent in long-term DM1. At this stage, the combination of DM1 and hypertension resulted in nonsignificant additive effects. Moreover, the coexistence of DM1 blunted the inflammatory response to hypertension. Anti-inflammatory IL-10 and antioxidants were induced in long-term DM1 and DM1/SHR hearts. Myocardial inflammation was, however, observed in the short-term model. In cultured cardiomyocytes, IL-10, TGF-β1, and catalase blocked the glucose-stimulated expression of proinflammatory genes. Fibrosis and apoptosis are features of long-term myocardial damage in experimental DM1. Associated hypertension does not induce additional changes. Myocardial inflammation is present in hypertension and short-term DM1, but is not a key feature in long-term DM1. Local reduction of proinflammatory factors and expression of anti-inflammatory and antioxidant molecules may underlie this effect.