Characterization of left ventricular myocardial sodium-glucose cotransporter 1 expression in patients with end-stage heart failure

Recipient Pericardial Apolipoprotein Levels Might Be an Indicator of Worse Outcomes after Orthotopic Heart Transplantation

BACKGROUND

End-stage heart failure (ESHF) leads to hypoperfusion and edema formation throughout the body and is accompanied by neurohormonal and immunological alterations. Orthotopic heart transplantation (HTX) has been used as a beneficial option for ESHF. Due to the shortage of donor hearts, the ideal matching and timing of donors and recipients has become more important.

PURPOSE

In this study, our aim was to explore the relationship between the clinical outcomes of HTX and the cytokine and apolipoprotein profiles of the recipient pericardial fluid obtained at heart transplantation after opening the pericardial sac.

MATERIALS AND METHODS

The clinical data and the interleukin, adipokine, and lipoprotein levels in the pericardial fluid of twenty HTX recipients were investigated. Outcome variables included primer graft dysfunction (PGD), the need for post-transplantation mechanical cardiac support (MCS), International Society for Heart and Lung Transplantation grade ≥2R rejection, and mortality. Recipient risk scores were also investigated.

RESULTS

Leptin levels were significantly lower in patients with PGD than in those without PGD (median: 6.36 (IQR: 5.55-6.62) versus 7.54 (IQR = 6.71-10.44); p = 0.029). Higher ApoCII levels (median: 14.91 (IQR: 11.55-21.30) versus 10.31 (IQR = 10.02-13.07); p = 0.042) and ApoCIII levels (median: 60.32 (IQR: 43.00-81.66) versus 22.84 (IQR = 15.84-33.39); p = 0.005) were found in patients (n = 5) who died in the first 5 years after HTX. In patients who exhibited rejection (n = 4) in the first month after transplantation, the levels of adiponectin (median: 74.48 (IQR: 35.51-131.70) versus 29.96 (IQR: 19.86-42.28); p = 0.039), ApoCII (median: 20.11 (IQR: 13.06-23.54) versus 10.32 (IQR: 10.02-12.84); p = 0.007), and ApoCIII (median: 70.97 (IQR: 34.72-82.22) versus 26.33 (IQR: 17.18-40.17); p = 0.029) were higher than in the nonrejection group. Moreover, the pericardial thyroxine (T4) levels (median: 3.96 (IQR: 3.49-4.46) versus 4.69 (IQR: 4.23-5.77); p = 0.022) were lower in patients with rejection than in patients who did not develop rejection.

CONCLUSION

Our results indicate that apolipoproteins can facilitate the monitoring of rejection and could be a useful tool in the forecasting of early and late complications.

Comparative cardiovascular benefits of individual SGLT2 inhibitors in type 2 diabetes and heart failure: a systematic review and network meta-analysis of randomized controlled trials

Background

In patients with type 2 diabetes (T2D) and a history of heart failure (HF), sodium-glucose cotransporter-2 inhibitors (SGLT2is) have demonstrated cardiovascular (CV) benefits. However, the comparative efficacy of individual SGLT2is remains uncertain. This network meta-analysis (NMA) compared the efficacy and safety of five SGLT2is (canagliflozin, dapagliflozin, empagliflozin, ertugliflozin, and sotagliflozin) on CV outcomes in these patients.

Materials and methods

PubMed, Embase, and the Cochrane Central Register of Controlled Trials were searched up to September 23, 2022, to identify all randomized controlled trials (RCTs) comparing SGLT2is to placebo in T2D patients with HF. The main outcomes included composite CV death/heart failure hospitalization (HFH), HFH, CV death, all-cause mortality, and adverse events. Pairwise and NMA approaches were applied.

Results

Our analysis included 11 RCTs with a total of 20,438 patients with T2D and HF. All SGLT2is significantly reduced HFH compared to standard of care (SoC) alone. "Add-on" SGLT2is, except ertugliflozin, significantly reduced composite CV death/HFH relative to SoC alone. Moreover, canagliflozin had lower composite CV death/HFH compared to dapagliflozin. Based on the surface under the cumulative ranking curve (SUCRA), the top-ranked SGLT2is for reducing HFH were canagliflozin (95.5%), sotagliflozin (66.0%), and empagliflozin (57.2%). Head-to-head comparisons found no significant differences between individual SGLT2is in reducing CV death. "Add-on" SGLT2is reduced all-cause mortality compared with SoC alone, although only dapagliflozin was statistically significant. No SGLT2is were significantly associated with serious adverse events. A sensitivity analysis focusing on HF-specific trials found that dapagliflozin, empagliflozin, and sotagliflozin significantly reduced composite CV death/HFH, consistent with the main analysis. However, no significant differences were identified from their head-to-head comparisons in the NMA. The SUCRA indicated that sotagliflozin had the highest probability of reducing composite CV death/HFH (97.6%), followed by empagliflozin (58.4%) and dapagliflozin (44.0%).

Conclusion

SGLT2is significantly reduce the composite CV death/HFH outcome. Among them, canagliflozin may be considered the preferred treatment for patients with diabetes and a history of heart failure, but it may also be associated with an increased risk of any adverse events compared to other SGLT2is. However, a sensitivity analysis focusing on HF-specific trials identified sotagliflozin as the most likely agent to reduce CV death/HFH, followed by empagliflozin and dapagliflozin.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022353754.

Sodium Glucose Co-Transporter 2 Inhibitors and the Cardiovascular System: Current Knowledge and Future Expectations

Diabetic cardiomyopathy is a well-recognized clinical entity and reflects a complex relationship between metabolic substrates and myocardial function. Sodium glucose co-transporter 2 (SGLT2) inhibitors are antidiabetic agents that are found to exert multiple cardioprotective effects. Large clinical trials showed their beneficial effects on patients with heart failure, reducing the rates of rehospitalizations and improving kidney function. The aim of this review is to summarize the latest evidence in the literature regarding the multiple effects of SGLT2 inhibitors on patients across the spectrum of cardiovascular diseases.

Distinct Effects of Mitochondrial Na+/Ca2+ Exchanger Inhibition and Ca2+ Uniporter Activation on Ca2+ Sparks and Arrhythmogenesis in Diabetic Rats

Background Mitochondrial dysfunction contributes to the cardiac remodeling triggered by type 2 diabetes (T2D). Mitochondrial Ca2+ concentration ([Ca2+]m) modulates the oxidative state and cytosolic Ca2+ regulation. Thus, we investigated how T2D affects mitochondrial Ca2+ fluxes, the downstream consequences on myocyte function, and the effects of normalizing mitochondrial Ca2+ transport. Methods and Results We compared myocytes/hearts from transgenic rats with late-onset T2D (rats that develop late-onset T2D due to heterozygous expression of human amylin in the pancreatic β-cells [HIP] model) and their nondiabetic wild-type (WT) littermates. [Ca2+]m was significantly lower in myocytes from diabetic HIP rats compared with WT cells. Ca2+ extrusion through the mitochondrial Na+/Ca2+ exchanger (mitoNCX) was elevated in HIP versus WT myocytes, particularly at moderate and high [Ca2+]m, while mitochondrial Ca2+ uptake was diminished. Mitochondrial Na+ concentration was comparable in WT and HIP rat myocytes and remained remarkably stable while manipulating mitoNCX activity. Lower [Ca2+]m was associated with oxidative stress, increased sarcoplasmic reticulum Ca2+ leak in the form of Ca2+ sparks, and mitochondrial dysfunction in T2D hearts. MitoNCX inhibition with CGP-37157 reduced oxidative stress, Ca2+ spark frequency, and stress-induced arrhythmias in HIP rat hearts while having no significant effect in WT rats. In contrast, activation of the mitochondrial Ca2+ uniporter with SB-202190 enhanced spontaneous sarcoplasmic reticulum Ca2+ release and had no significant effect on arrhythmias in both WT and HIP rat hearts. Conclusions [Ca2+]m is reduced in myocytes from rats with T2D due to a combination of exacerbated mitochondrial Ca2+ extrusion through mitoNCX and impaired mitochondrial Ca2+ uptake. Partial mitoNCX inhibition limits sarcoplasmic reticulum Ca2+ leak and arrhythmias in T2D hearts, whereas mitochondrial Ca2+ uniporter activation does not.

SGLT1: A Potential Drug Target for Cardiovascular Disease

SGLT1 and SGLT2 are the two main members of the sodium-glucose cotransporters (SGLTs), which are mainly responsible for glucose reabsorption in the body. In recent years, many large clinical trials have shown that SGLT2 inhibitors have cardiovascular protection for diabetic and non-diabetic patients independent of lowering blood glucose. However, SGLT2 was barely detected in the hearts of humans and animals, while SGLT1 was highly expressed in myocardium. As SGLT2 inhibitors also have a moderate inhibitory effect on SGLT1, the cardiovascular protection of SGLT2 inhibitors may be due to SGLT1 inhibition. SGLT1 expression is associated with pathological processes such as cardiac oxidative stress, inflammation, fibrosis, and cell apoptosis, as well as mitochondrial dysfunction. The purpose of this review is to summarize the protective effects of SGLT1 inhibition on hearts in various cell types, including cardiomyocytes, endothelial cells, and fibroblasts in preclinical studies, and to highlight the underlying molecular mechanisms of protection against cardiovascular diseases. Selective SGLT1 inhibitors could be considered a class of drugs for cardiac-specific therapy in the future.

Anti-Diabetic Therapy and Heart Failure: Recent Advances in Clinical Evidence and Molecular Mechanism

Diabetic patients have a two- to four-fold increase in the risk of heart failure (HF), and the co-existence of diabetes and HF is associated with poor prognosis. In randomized clinical trials (RCTs), compelling evidence has demonstrated the beneficial effects of sodium-glucose co-transporter-2 inhibitors on HF. The mechanism includes increased glucosuria, restored tubular glomerular feedback with attenuated renin-angiotensin II-aldosterone activation, improved energy utilization, decreased sympathetic tone, improved mitochondria calcium homeostasis, enhanced autophagy, and reduced cardiac inflammation, oxidative stress, and fibrosis. The RCTs demonstrated a neutral effect of the glucagon-like peptide receptor agonist on HF despite its weight-reducing effect, probably due to it possibly increasing the heart rate via increasing cyclic adenosine monophosphate (cAMP). Observational studies supported the markedly beneficial effects of bariatric and metabolic surgery on HF despite no current supporting evidence from RCTs. Bromocriptine can be used to treat peripartum cardiomyopathy by reducing the harmful cleaved prolactin fragments during late pregnancy. Preclinical studies suggest the possible beneficial effect of imeglimin on HF through improving mitochondrial function, but further clinical evidence is needed. Although abundant preclinical and observational studies support the beneficial effects of metformin on HF, there is limited evidence from RCTs. Thiazolidinediones increase the risk of hospitalized HF through increasing renal tubular sodium reabsorption mediated via both the genomic and non-genomic action of PPARγ. RCTs suggest that dipeptidyl peptidase-4 inhibitors, including saxagliptin and possibly alogliptin, may increase the risk of hospitalized HF, probably owing to increased circulating vasoactive peptides, which impair endothelial function, activate sympathetic tones, and cause cardiac remodeling. Observational studies and RCTs have demonstrated the neutral effects of insulin, sulfonylureas, an alpha-glucosidase inhibitor, and lifestyle interventions on HF in diabetic patients.

Donor Pericardial Interleukin and Apolipoprotein Levels May Predict the Outcome after Human Orthotopic Heart Transplantation

The proinflammatory cascade that is activated at the time of brain death plays a crucial role in organ procurement. Our aim of this study was to explore the relationship between the clinical outcome of orthotopic heart transplantation, as well as cytokine and apolipoprotein profiles of the pericardial fluid obtained at donation. Interleukin, adipokine and lipoprotein levels in the pericardial fluid, as well as clinical data of twenty donors after brain death, were investigated. Outcome variables included primary graft dysfunction, the need for posttransplantation mechanical cardiac support and International Society for Heart and Lung Transplantation grade ≥ 2R rejection. Hormone management and donor risk scores were also investigated. Lower levels of IL-6 were observed in primary graft dysfunction (median: 36.72 [IQR: 19.47–62.90] versus 183.67 [41.21–452.56]; p = 0.029) and in the need for mechanical cardiac support (44.12 [20.12–85.70] versus 247.13 [38.51–510.38]; p = 0.043). Rejection was associated with lower ApoAII (p = 0.021), ApoB100 (p = 0.032) and ApoM levels (p = 0.025). Lower adipsin levels were detected in those patients receiving desmopressin (p = 0.037); moreover, lower leptin levels were found in those patients receiving glucocorticoid therapy (p = 0.045), and higher T3 levels were found in those patients treated with L-thyroxine (p = 0.047) compared to those patients not receiving these hormone replacement therapies. IL-5 levels were significantly associated with UNOS-D score (p = 0.004), Heart Donor Score (HDS) and Adapted HDS (p < 0.001). The monitoring of immunological and metabolic changes in donors after brain death may help in the prediction of potential complications after heart transplantation, thus potentially optimizing donor heart allocation.

SGLT2 inhibitors: role in protective reprogramming of cardiac nutrient transport and metabolism

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce heart failure events by direct action on the failing heart that is independent of changes in renal tubular function. In the failing heart, nutrient transport into cardiomyocytes is increased, but nutrient utilization is impaired, leading to deficient ATP production and the cytosolic accumulation of deleterious glucose and lipid by-products. These by-products trigger downregulation of cytoprotective nutrient-deprivation pathways, thereby promoting cellular stress and undermining cellular survival. SGLT2 inhibitors restore cellular homeostasis through three complementary mechanisms: they might bind directly to nutrient-deprivation and nutrient-surplus sensors to promote their cytoprotective actions; they can increase the synthesis of ATP by promoting mitochondrial health (mediated by increasing autophagic flux) and potentially by alleviating the cytosolic deficiency in ferrous iron; and they might directly inhibit glucose transporter type 1, thereby diminishing the cytosolic accumulation of toxic metabolic by-products and promoting the oxidation of long-chain fatty acids. The increase in autophagic flux mediated by SGLT2 inhibitors also promotes the clearance of harmful glucose and lipid by-products and the disposal of dysfunctional mitochondria, allowing for mitochondrial renewal through mitochondrial biogenesis. This Review describes the orchestrated interplay between nutrient transport and metabolism and nutrient-deprivation and nutrient-surplus signalling, to explain how SGLT2 inhibitors reverse the profound nutrient, metabolic and cellular abnormalities observed in heart failure, thereby restoring the myocardium to a healthy molecular and cellular phenotype.

Clinical efficacy of SGLT2 inhibitors with different SGLT1/SGLT2 selectivity in cardiovascular outcomes among patients with and without heart failure: A systematic review and meta-analysis of randomized trials

BACKGROUND

Some sodium-glucose co-transporter-2 (SGLT2) inhibitors showed benefits on heart failure (HF), but different SGLT2/SGLT1 selectivity might influence the treatment effect. This study aimed to meta-analyze the treatment effects of SGLT2 inhibitors and the diversity of receptor selectivity for patients with and without HF.

METHODS

Randomized controlled trials were searched in PubMed, Embase, Cochrane databases and ClinicalTrials.gov registry from inception to October 2020. The interest outcomes were analyzed with random-effects models and presented with a risk ratio (RR) and 95% confidence interval (CI). Subgroup analyses examined the treatment effects among SGLT2 inhibitors with different SGLT2/SGLT1 selectivity.

RESULTS

The final analyses included 10 trials and 52,607 patients. The RR of total cardiovascular (CV) death or hospitalization for HF (HHF) between SGLT2 inhibitors and placebo was 0.79 (95% CI 0.74-0.84, I2 = 31%). With SGLT2 inhibitors, HF patients had reduced mortality risks (RR 0.89, 95% CI 0.80-0.99, I2 = 0), and non-HF patients had lower risks of major adverse CV events (RR 0.92, 95% CI 0.85-0.99, I2 = 0). The risk reduction of HHF was consistent in groups of HF (RR 0.72, 95% CI 0.64-0.80, I2 = 8%) and non-HF (RR 0.74, 95% CI 0.61-0.89, I2 = 0), but the effect of the low SGLT2/SGLT1 selectivity inhibitor was insignificant in non-HF patients.

CONCLUSION

The efficacy of SGLT2 inhibitors on risk reduction of total CV death or HHF is consistent with the previous studies. The regimen is beneficial for reducing mortality in patients with HF and major adverse CV events in those without HF. Different SGLT2/SGLT1 selectivity may differ in the treatment effects in patients with and without HF.

Cardiac Sodium/Hydrogen Exchanger (NHE11) as a Novel Potential Target for SGLT2i in Heart Failure: A Preliminary Study

Despite the reduction of cardiovascular events, including the risk of death, associated with sodium/glucose cotransporter 2 inhibitors (SGLT2i), their basic action remains unclear. Sodium/hydrogen exchanger (NHE) has been proposed as the mechanism of action, but there are controversies related to its function and expression in heart failure (HF). We hypothesized that sodium transported-related molecules could be altered in HF and modulated through SGLT2i. Transcriptome alterations in genes involved in sodium transport in HF were investigated in human heart samples by RNA-sequencing. NHE11 and NHE1 protein levels were determined by ELISA; the effect of empagliflozin on NHE11 and NHE1 mRNA levels in rats’ left ventricular tissues was studied through RT-qPCR. We highlighted the overexpression of SLC9C2 and SCL9A1 sodium transport genes and the increase of the proteins that encode them (NHE11 and NHE1). NHE11 levels were correlated with left ventricular diameters, so we studied the effect of SGLT2i on its expression, observing that NHE11 mRNA levels were reduced in treated rats. We showed alterations in several sodium transports and reinforced the importance of these channels in HF progression. We described upregulation in NHE11 and NHE1, but only NHE11 correlated with human cardiac dysfunction, and its levels were reduced after treatment with empagliflozin. These results propose NHE11 as a potential target of SGLT2i in cardiac tissue.

Sodium-glucose cotransporter-2 (SGLT2) expression in diabetic and non-diabetic failing human cardiomyocytes

This study aimed at investigating the SGLT2 expression in human cardiomyocytes. Human studies evaluating cardiomyocyte SGLT2s expression are limited. To better clarify this issue, SGLT2 protein expression was assessed in human hearts of diabetic and non-diabetic patients, and in AC16 human cardiomyocyte cell line. A prospective study with a follow-up of patients who underwent their first heart transplant (HTX) was performed. Explanted heart, basal (1 week after HTX), and final (48 weeks after HTX) endomyocardial biopsies (EMBs) from patients were evaluated for SGLT2 occurrence in cardiomyocyte with immunohistochemistry, immunofluorescence and SGLT2 quantization with both real-time reverse transcription-polymerase chain reaction and Western blot analysis. The immunofluorescence co-localization of SGLT2 in cardiomyocyte evidenced that an increased expression in the explanted heart from diabetic patients compared to non-diabetic (p < 0.001). In all final EMBs from diabetic patients, the expression of SGLT2 in cardiomyocyte was increased compared to non-diabetic (p < 0.01). This evidence was confirmed by Western blot analysis of SGLT2 protein. In addition, PCR analysis revealed very low mRNA levels in basal EMBs from diabetic and non-diabetic patients (p = NS), whereas final EMBs from diabetic patients showed higher SGLT2 mRNA levels in diabetic compared to non-diabetic patients (p < 0.05). Cultured human cardiomyocytes exposed to high-glucose showed increased expression of SGLT2 protein compared to cells exposed to normal glucose (p < 0.05). The presence of SGLT2 in cardiomyocytes supports the hypothesis of SGLT2i-mediated impact on metabolic pathways within cardiomyocytes. Moreover, metabolic disorders linked to diabetes may lead promptly to upregulation of SGLT2 levels in human cardiomyocytes.

Characterization of the SGLT2 Interaction Network and Its Regulation by SGLT2 Inhibitors: A Bioinformatic Analysis

Background: Sodium–glucose cotransporter 2 (SGLT2), also known as solute carrier family 5 member 2 (SLC5A2), is a promising target for a new class of drugs primarily established as kidney-targeting, effective glucose-lowering agents used in diabetes mellitus (DM) patients. Increasing evidence indicates that besides renal effects, SGLT2 inhibitors (SGLT2i) have also a systemic impact via indirectly targeting the heart and other tissues. Our hypothesis states that the pleiotropic effects of SGLT2i are associated with their binding force, location of targets in the SGLT2 networks, targets involvement in signaling pathways, and their tissue-specific expression.

Methods: Thus, to investigate differences in SGLT2i impact on human organisms, we re-created the SGLT2 interaction network incorporating its inhibitors and metformin and analyzed its tissue-specific expression using publicly available datasets. We analyzed it in the context of the so-called key terms ( autophagy, oxidative stress, aging, senescence, inflammation, AMPK pathways, and mTOR pathways) which seem to be crucial to elucidating the SGLT2 role in a variety of clinical manifestations.

Results: Analysis of SGLT2 and its network components’ expression confidence identified selected organs in the following order: kidney, liver, adipose tissue, blood, heart, muscle, intestine, brain, and artery according to the TISSUES database. Drug repurposing analysis of known SGLT2i pointed out the influence of SGLT1 regulators on the heart and intestine tissue. Additionally, dapagliflozin seems to also have a stronger impact on brain tissue through the regulation of SGLT3 and SLC5A11. The shortest path analysis identified interaction SIRT1-SGLT2 among the top five interactions across six from seven analyzed networks associated with the key terms. Other top first-level SGLT2 interactors associated with key terms were not only ADIPOQ, INS, GLUT4, ACE, and GLUT1 but also less recognized ILK and ADCY7. Among other interactors which appeared in multiple shortest-path analyses were GPT, COG2, and MGAM. Enrichment analysis of SGLT2 network components showed the highest overrepresentation of hypertensive disease, DM-related diseases for both levels of SGLT2 interactors. Additionally, for the extended SGLT2 network, we observed enrichment in obesity (including SGLT1), cancer-related terms, neuroactive ligand–receptor interaction, and neutrophil-mediated immunity.

Conclusion: This study provides comprehensive and ranked information about the SGLT2 interaction network in the context of tissue expression and can help to predict the clinical effects of the SGLT2i.

Dual sodium-glucose cotransporter (SGLT) 1/2 versus pure SGLT2 inhibitors: two distinct drug categories or one class with multiple faces?

INTRODUCTION

According to their selectivity for sodium-glucose cotransporters (SGLT) 1 and 2, gliflozins could be subdivided into two additional categories: pure SGLT2 inhibitors, which are highly selective for SGLT2, and dual SGLT1/2 inhibitors which, in addition to SGLT2, exhibit strong inhibitory activity for SGLT1.

AREAS COVERED

This article aims to discuss whether the pharmacological differences between the two subtypes of gliflozins could be translated into different efficacy and safety characteristics that might be important for clinical practice.

EXPERT OPINION

In large cardiovascular outcome trials, dual inhibitors have shown a unique efficacy profile in terms of reducing glycemia in patients with severe renal impairment and decreasing the risk of atherosclerotic outcomes. These features do not characterize selective SGLT2 inhibitors and could be attributed to the parallel inhibition of SGLT1. The increased risk of diarrhea and severe hypoglycemia observed only with dual inhibitors is probably related to their action in the gut and brain, respectively. However, differences in populations included in various studies should be considered when attempting to translate their findings into clinical practice; therefore, head-to-head trials are needed to shed more light on this issue and provide clear guidance to clinicians.

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.

Genetic variation in sodium glucose co-transporter 1 and cardiac structure and function at middle age

Aims

The effects of inhibition of sodium glucose cotransporter (SGLT)‐1, as opposed to SGLT2, on cardiovascular structure and function are not well known. We assessed the associations of a missense genetic variant of SGLT1 with cardiac structure and function.

Methods and results

We evaluated associations of a functionally modifying variant of SLC5A1 (rs17683011 [p.Asn51Ser]), the gene that encodes SGLT1, with cardiac structure and function on echocardiography among middle‐aged adults in the Coronary Artery Risk Development in Young Adults Study. Of 1904 participants (55.3 ± 3.5 years, 57% female, 34% Black), 166 (13%) White participants and 18 (3%) Black participants had at least one copy of rs17683011. There were no significant differences in age, sex, body mass index, glucose, or diabetes status by the presence of the rs17683011 variant. In Black participants, the presence of at least one copy of the rs17683011 variant was significantly associated with better GLS compared with those without a copy of the variant after covariate adjustment (−15.8 ± 0.7% vs. −14.0 ± 0.1%, P = 0.02). Although the direction of effect was consistent, the association between the presence of at least one copy of rs17683011 and GLS was not statistically significant in White participants (−15.1 ± 0.2% vs. −14.8 ± 0.1%, P = 0.16). There were no significant associations between rs17683011 and other measures of LV structure, systolic function, or diastolic function.

Conclusions

The rs17683011 variant, a functionally modifying variant of the SGLT1 gene, was associated with higher GLS among middle‐age adults. These exploratory findings require further validation and suggest that SGLT1 inhibition may have beneficial effects upon LV systolic function.

Models of cardiovascular surgery biobanking to facilitate translational research and precision medicine

Biobanking in health care has evolved over the last few decades from simple biological sample repositories to complex and dynamic units with multi‐organizational infrastructure networks and has become an essential tool for modern medical research. Cardiovascular tissue biobanking provides a unique opportunity to utilize cardiac and vascular samples for translational research into heart failure and other related pathologies. Current techniques for diagnosis, classification, and treatment monitoring of cardiac disease relies primarily on interpretation of clinical signs, imaging, and blood biomarkers. Further research at the disease source (i.e. myocardium and blood vessels) has been limited by a relative lack of access to quality human cardiac tissue and the inherent shortcomings of most animal models of heart disease. In this review, we describe a model for cardiovascular tissue biobanking and databasing, and its potential to facilitate basic and translational research. We share techniques to procure endocardial samples from patients with hypertrophic cardiomyopathy, heart failure with reduced ejection fraction, and heart failure with preserved ejection fraction, in addition to aortic disease samples. We discuss some of the issues with respect to data collection, privacy, biobank consent, and the governance of tissue biobanking. The development of tissue biobanks as described here has significant scope to improve and facilitate translational research in multi‐omic fields such as genomics, transcriptomics, proteomics, and metabolomics. This research heralds an era of precision medicine, in which patients with cardiovascular pathology can be provided with optimized and personalized medical care for the treatment of their individual phenotype.

Differences in outcomes of hospitalizations for heart failure after SGLT2 inhibitor treatment: effect modification by atherosclerotic cardiovascular disease

Background

The treatment effects on hospitalization for heart failure (hHF) from sodium-glucose cotransporter 2 (SGLT2) inhibitors may vary among type 2 diabetes (T2D) patients depending on whether or not they have established atherosclerotic cardiovascular diseases (ASCVD). We aimed to examine differences in hHF outcomes after dapagliflozin or empagliflozin use between T2D patients with and without a history of established ASCVD.

Methods

We conducted a retrospective multi-institutional cohort study in Taiwan. We included T2D patients newly receiving dapagliflozin or empagliflozin during 2016–2019, and followed them up until December 31, 2020. We implemented 1:1 propensity score matching to create homogenous groups for comparisons. We generated Cox proportional hazard models to compare the risk of hHF between dapagliflozin and empagliflozin (reference group). We included interaction terms of SGLT2 inhibitor and ASCVD history in the regression models to examine effect modification by ASCVD.

Results

We included a total cohort of 9,586 dapagliflozin new users and 9,586 matched empagliflozin new users. The overall hHF risks were similar for dapagliflozin and empagliflozin (HR: 0.90, 95% CI 0.74–1.09). However, differential hHF risks between dapagliflozin and empagliflozin were observed only in the subgroup without ASCVD (HR: 0.67, 95% CI 0.49–0.90), while not in the subgroup with ASCVD (HR: 1.12, 95% 0.87–1.45), and the p-value for examining interaction was 0.0097.

Conclusion

In this study, history of established ASCVD was associated with different hHF risks among SGLT2 inhibitors. For T2D patients without ASCVD, dapagliflozin may offer a more favorable hHF reduction effect, compared to empagliflozin, in clinical practice. Future prospective studies should be conducted to validate our findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01406-3.

Changes in the SARS-CoV-2 cellular receptor ACE2 levels in cardiovascular patients: a potential biomarker for the stratification of COVID-19 patients

Angiotensin-converting enzyme 2 (ACE2) is essential for SARS-CoV-2 cellular entry. Here we studied the effects of common comorbidities in severe COVID-19 on ACE2 expression. ACE2 levels (by enzyme activity and ELISA measurements) were determined in human serum, heart and lung samples from patients with hypertension (n = 540), heart transplantation (289) and thoracic surgery (n = 49). Healthy individuals (n = 46) represented the controls. Serum ACE2 activity was increased in hypertensive subjects (132%) and substantially elevated in end-stage heart failure patients (689%) and showed a strong negative correlation with the left ventricular ejection fraction. Serum ACE2 activity was higher in male (147%), overweight (122%), obese (126%) and elderly (115%) hypertensive patients. Primary lung cancer resulted in higher circulating ACE2 activity, without affecting ACE2 levels in the surrounding lung tissue. Male sex resulted in elevated serum ACE2 activities in patients with heart transplantation or thoracic surgery (146% and 150%, respectively). Left ventricular (tissular) ACE2 activity was unaffected by sex and was lower in overweight (67%), obese (62%) and older (73%) patients with end-stage heart failure. There was no correlation between serum and tissular (left ventricular or lung) ACE2 activities. Neither serum nor tissue (left ventricle or lung) ACE2 levels were affected by RAS inhibitory medications. Abandoning of ACEi treatment (non-compliance) resulted in elevated blood pressure without effects on circulating ACE2 activities. ACE2 levels associate with the severity of cardiovascular diseases, suggestive for a role of ACE2 in the pathomechanisms of cardiovascular diseases and providing a potential explanation for the higher mortality of COVID-19 among cardiovascular patients. Abandoning RAS inhibitory medication worsens the cardiovascular status without affecting circulating or tissue ACE2 levels.

The promise and problems of metabolic-based therapies for heart failure

Despite standard therapies, heart failure patients have high rates of morbidity highlighting the need to develop alternative therapeutic approaches. Heart failure has been described as an energy-starved condition that is hypothesized to drive the pathological remodeling of the heart. Numerous studies have described the metabolic defects that occur when the heart fails and adaptive changes that take place to maintain the energy needed for the heart to function properly. In this review we will summarize the metabolic requirements of a normal heart and what happens during failure. We will also summarize the various metabolic therapeutic strategies that have been developed over the years to treat heart failure and their results from clinical trials.

Cardiac PANK1 deletion exacerbates ventricular dysfunction during pressure overload

Coenzyme A (CoA) is an essential cofactor required for intermediary metabolism. Perturbations in homeostasis of CoA have been implicated in various pathologies; however, whether CoA homeostasis is changed and the extent to which CoA levels contribute to ventricular function and remodeling during pressure overload has not been explored. In this study, we sought to assess changes in CoA biosynthetic pathway during pressure overload and determine the impact of limiting CoA on cardiac function. We limited cardiac CoA levels by deleting the rate-limiting enzyme in CoA biosynthesis, pantothenate kinase 1 (Pank1). We found that constitutive, cardiomyocyte-specific Pank1 deletion (cmPank1-/-) significantly reduced PANK1 mRNA, PANK1 protein, and CoA levels compared with Pank1-sufficient littermates (cmPank1+/+) but exerted no obvious deleterious impact on the mice at baseline. We then subjected both groups of mice to pressure overload-induced heart failure. Interestingly, there was more ventricular dilation in cmPank1-/- during the pressure overload. To explore potential mechanisms contributing to this phenotype, we performed transcriptomic profiling, which suggested a role for Pank1 in regulating fibrotic and metabolic processes during the pressure overload. Indeed, Pank1 deletion exacerbated cardiac fibrosis following pressure overload. Because we were interested in the possibility of early metabolic impacts in response to pressure overload, we performed untargeted metabolomics, which indicated significant changes to metabolites involved in fatty acid and ketone metabolism, among other pathways. Collectively, our study underscores the role of elevated CoA levels in supporting fatty acid and ketone body oxidation, which may be more important than CoA-driven, enzyme-independent acetylation in the failing heart.NEW & NOTEWORTHY Changes in CoA homeostasis have been implicated in a variety of metabolic diseases; however, the extent to which changes in CoA homeostasis impacts remodeling has not been explored. We show that limiting cardiac CoA levels via PANK deletion exacerbated ventricular remodeling during pressure overload. Our results suggest that metabolic alterations, rather than structural alterations, associated with Pank1 deletion may underlie the exacerbated cardiac phenotype during pressure overload.

Effects of SGLT2 Inhibitors beyond Glycemic Control-Focus on Myocardial SGLT1

Selective sodium–glucose cotransporter 2 (SGLT2) inhibitors reduced the risk of hospitalization for heart failure in patients with or without type 2 diabetes (T2DM) in large-scale clinical trials. The exact mechanism of action is currently unclear. The dual SGLT1/2 inhibitor sotagliflozin not only reduced hospitalization for HF in patients with T2DM, but also lowered the risk of myocardial infarction and stroke, suggesting a possible additional benefit related to SGLT1 inhibition. In fact, several preclinical studies suggest that SGLT1 plays an important role in cardiac pathophysiological processes. In this review, our aim is to establish the clinical significance of myocardial SGLT1 inhibition through reviewing basic research studies in the context of SGLT2 inhibitor trials.

Influence of receptor selectivity on benefits from SGLT2 inhibitors in patients with heart failure: a systematic review and head-to-head comparative efficacy network meta-analysis

Background

Receptor selectivity of sodium-glucose cotransporter-2 inhibitors (SGLT2i) varies greatly between agents. The overall improvement of cardiovascular (CV) outcomes in heart failure (HF) patients varies between trials. We, therefore, evaluated the comparative efficacy of individual SGLT2i and the influence of their respective receptor selectivity thereon.

Methods

We identified randomized controlled trials investigating the use of SGLT2i in patients with HF—either as the target cohort or as a subgroup of it. Comparators included placebo or any other active treatment. The primary endpoint was the composite of hospitalization for HF or CV death. Secondary outcomes included all-cause mortality, CV mortality, hospitalization for HF, worsening renal function (RF), and the composite of worsening RF or CV death. Evidence was synthesized using network meta-analysis. In addition, the impact of receptor selectivity on outcomes was analysed using meta-regression.

Results

We identified 18,265 patients included in 22 trials. Compared to placebo, selective and non-selective SGLT2i improved fatal and non-fatal HF events. Head-to-head comparisons suggest superior efficacy with sotagliflozin as compared to dapagliflozin, empagliflozin or ertugliflozin. No significant difference was found between canagliflozin and sotagliflozin. Meta-regression analyses show a decreasing benefit on HF events with increasing receptor selectivity of SGLT2i. In contrast, receptor selectivity did not affect mortality and renal endpoints and no significant difference between individual SGLT2i was noted.

Conclusion

Our data point towards a class-effect of SGLT2i on mortality and renal outcomes. However, non-selective SGLT2i such as sotagliflozin may be superior to highly selective SGLT2i in terms of HF outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01913-z.

Left Ventricular SGLT1 Protein Expression Correlates with the Extent of Myocardial Nitro-Oxidative Stress in Rats with Pressure and Volume Overload-Induced Heart Failure

Myocardial sodium-glucose cotransporter 1 (SGLT1) has been shown to be upregulated in humans with heart failure (HF) with or without diabetes. In vitro studies have linked SGLT1 to increased nitro-oxidative stress in cardiomyocytes. We aimed to assess the relation between left ventricular (LV) SGLT1 expression and the extent of nitro-oxidative stress in two non-diabetic rat models of chronic heart failure (HF) evoked by either pressure (TAC, n = 12) or volume overload (ACF, n = 12). Sham-operated animals (Sham-T and Sham-A, both n = 12) served as controls. Both TAC and ACF induced characteristic LV structural and functional remodeling. Western blotting revealed that LV SGLT1 protein expression was significantly upregulated in both HF models (both p < 0.01), whereas the phosphorylation of ERK1/2 was decreased only in ACF; AMPKα activity was significantly reduced in both models. The protein expression of the Nox4 NADPH oxidase isoform was increased in both TAC and ACF compared with respective controls (both p < 0.01), showing a strong positive correlation with SGLT1 expression (r = 0.855, p < 0.001; and r = 0.798, p = 0.001, respectively). Furthermore, SGLT1 protein expression positively correlated with the extent of myocardial nitro-oxidative stress in failing hearts assessed by 3-nitrotyrosin (r = 0.818, p = 0.006) and 4-hydroxy-2-nonenal (r = 0.733, p = 0.020) immunostaining. Therefore, LV SGLT1 protein expression was upregulated irrespective of the nature of chronic hemodynamic overload, and correlated significantly with the expression of Nox4 and with the level of myocardial nitro-oxidative stress, suggesting a pathophysiological role of SGLT1 in HF.

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.

Implications of SGLT Inhibition on Redox Signalling in Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained (atrial) arrhythmia, a considerable global health burden and often associated with heart failure. Perturbations of redox signalling in cardiomyocytes provide a cellular substrate for the manifestation and maintenance of atrial arrhythmias. Several clinical trials have shown that treatment with sodium-glucose linked transporter inhibitors (SGLTi) improves mortality and hospitalisation in heart failure patients independent of the presence of diabetes. Post hoc analysis of the DECLARE-TIMI 58 trial showed a 19% reduction in AF in patients with diabetes mellitus (hazard ratio, 0.81 (95% confidence interval: 0.68-0.95), n = 17.160) upon treatment with SGLTi, regardless of pre-existing AF or heart failure and independent from blood pressure or renal function. Accordingly, ongoing experimental work suggests that SGLTi not only positively impact heart failure but also counteract cellular ROS production in cardiomyocytes, thereby potentially altering atrial remodelling and reducing AF burden. In this article, we review recent studies investigating the effect of SGLTi on cellular processes closely interlinked with redox balance and their potential effects on the onset and progression of AF. Despite promising insight into SGLTi effect on Ca²⁺ cycling, Na⁺ balance, inflammatory and fibrotic signalling, mitochondrial function and energy balance and their potential effect on AF, the data are not yet conclusive and the importance of individual pathways for human AF remains to be established. Lastly, an overview of clinical studies investigating SGLTi in the context of AF is provided.

Sodium-glucose cotransporter 2 inhibitors reduce myocardial infarct size in preclinical animal models of myocardial ischaemia-reperfusion injury: a meta-analysis

AIMS/HYPOTHESIS

Large cardiovascular outcome trials demonstrated that the cardioprotective effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors might reach beyond glucose-lowering action. In this meta-analysis, we sought to evaluate the potential infarct size-modulating effect of SGLT2 inhibitors in preclinical studies.

METHODS

In this preregistered meta-analysis (PROSPERO: CRD42020189124), we included placebo-controlled, interventional studies of small and large animal models of myocardial ischaemia-reperfusion injury, testing the effect of SGLT2 inhibitor treatment on myocardial infarct size (percentage of area at risk or total area). Standardised mean differences (SMDs) were calculated and pooled using random-effects method. We evaluated heterogeneity by computing Τ² and I² values. Meta-regression was performed to explore prespecified subgroup differences according to experimental protocols and their contribution to heterogeneity was assessed (pseudo-R² values).

RESULTS

We identified ten eligible publications, reporting 16 independent controlled comparisons on a total of 224 animals. Treatment with SGLT2 inhibitor significantly reduced myocardial infarct size compared with placebo (SMD = -1.30 [95% CI -1.79, -0.81], p < 0.00001), referring to a 33% [95% CI 20%, 47%] difference. Heterogeneity was moderate (Τ² = 0.58, I² = 60%). SGLT2 inhibitors were only effective when administered to the intact organ system, but not to isolated hearts (p interaction <0.001, adjusted pseudo-R² = 47%). While acute administration significantly reduced infarct size, chronic treatment was superior (p interaction <0.001, adjusted pseudo-R² = 85%). The medications significantly reduced infarct size in both diabetic and non-diabetic animals, favouring the former (p interaction = 0.030, adjusted pseudo-R² = 12%). Treatment was equally effective in rats and mice, as well as in a porcine model. Individual study quality scores were not related to effect estimates (p = 0.33). The overall effect estimate remained large even after adjusting for severe forms of publication bias.

CONCLUSIONS/INTERPRETATION

The glucose-lowering SGLT2 inhibitors reduce myocardial infarct size in animal models independent of diabetes. Future in vivo studies should focus on clinical translation by exploring whether SGLT2 inhibitors limit infarct size in animals with relevant comorbidities, on top of loading doses of antiplatelet agents. Mechanistic studies should elucidate the potential relationship between the infarct size-lowering effect of SGLT2 inhibitors and the intact organ system.