Empagliflozin Disrupts a Tnfrsf12a-Mediated Feed Forward Loop That Promotes Left Ventricular Hypertrophy

Empagliflozin mitigates cardiac hypertrophy through cardiac RSK/NHE-1 inhibition

BACKGROUND

SGLT2i reduce cardiac hypertrophy, but underlying mechanisms remain unknown. Here we explore a role for serine/threonine kinases (STK) and sodium hydrogen exchanger 1(NHE1) activities in SGLT2i effects on cardiac hypertrophy.

METHODS

Isolated hearts from db/db mice were perfused with 1 µM EMPA, and STK phosphorylation sites were examined using unbiased multiplex analysis to detect the most affected STKs by EMPA. Subsequently, hypertrophy was induced in H9c2 cells with 50 µM phenylephrine (PE), and the role of the most affected STK (p90 ribosomal S6 kinase (RSK)) and NHE1 activity in hypertrophy and the protection by EMPA was evaluated.

RESULTS

In db/db mice hearts, EMPA most markedly reduced STK phosphorylation sites regulated by RSKL1, a member of the RSK family, and by Aurora A and B kinases. GO and KEGG analysis suggested that EMPA inhibits hypertrophy, cell cycle, cell senescence and FOXO pathways, illustrating inhibition of growth pathways. EMPA prevented PE-induced hypertrophy as evaluated by BNP and cell surface area in H9c2 cells. EMPA blocked PE-induced activation of NHE1. The specific NHE1 inhibitor Cariporide also prevented PE-induced hypertrophy without added effect of EMPA. EMPA blocked PE-induced RSK phosphorylation. The RSK inhibitor BIX02565 also suppressed PE-induced hypertrophy without added effect of EMPA. Cariporide mimicked EMPA's effects on PE-treated RSK phosphorylation. BIX02565 decreased PE-induced NHE1 activity, with no further decrease by EMPA.

CONCLUSIONS

RSK inhibition by EMPA appears as a novel direct cardiac target of SGLT2i. Direct cardiac effects of EMPA exert their anti-hypertrophic effect through NHE-inhibition and subsequent RSK pathway inhibition.

Pathophysiological basis of the cardiological benefits of SGLT-2 inhibitors: a narrative review

In recent years, GLP-1 receptor agonists (GLP-1RA), and SGLT-2 inhibitors (SGLT-2i) have become available, which have become valuable additions to therapy for type 2 diabetes as they are associated with low risk for hypoglycemia and cardiovascular benefits. Indeed, SGLT-2i have emerged as a promising class of agents to treat heart failure (HF). By inhibiting SGLT-2, these agents lead to excretion of glucose in urine with subsequent lowering of plasma glucose, although it is becoming clear that the observed benefits in HF cannot be explained by glucose-lowering alone. In fact, multiple mechanisms have been proposed to explain the cardiovascular and renal benefits of SGLT-2i, including hemodynamic, anti-inflammatory, anti-fibrotic, antioxidant, and metabolic effects. Herein, we review the available evidence on the pathophysiology of the cardiological benefits of SGLT-2i. In diabetic heart disease, in both clinical and animal models, the effect of SGLT-2i have been shown to improve diastolic function, which is even more evident in HF with preserved ejection fraction. The probable pathogenic mechanisms likely involve damage from free radicals, apoptosis, and inflammation, and therefore fibrosis, many of which have been shown to be improved by SGLT-2i. While the effects on systolic function in models of diabetic heart disease and HF with preserved ejection fraction is limited and contrasting, it is a key element in patients with HF and reduced ejection fraction both with and without diabetes. The significant improvement in systolic function appears to lead to subsequent structural remodeling of the heart with a reduction in left ventricle volume and a consequent reduction in pulmonary pressure. While the effects on cardiac metabolism and inflammation appear to be consolidated, greater efforts are still warranted to further define the entity to which these mechanisms contribute to the cardiovascular benefits of SGLT-2i.

Stiff substrates inhibit collagen accumulation via integrin α2β1, FAK and Src kinases in human atrial fibroblast and myofibroblast cultures derived from patients with aortal stenosis

The aim of the study was to confirm whether cell substrate stiffness may participate in the regulation of fibrosis. The involvement of integrin α2β1, focal adhesion kinase (FAK) and Src kinase in signal transmission was investigated. Human atrial fibroblasts and myofibroblasts were cultured in both soft (2.23 ± 0.8 kPa) and stiff (8.28 ± 1.06 kPa) polyacrylamide gels. The cells were derived from the right atrium of patients with aortal stenosis undergoing surgery. The isolated cells, identified as fibroblasts or myofibroblasts, were stained positively with α smooth muscle actin, vimentin and desmin. The cultures settled on stiff gel demonstrated lower intracellular collagen and collagen type I telopeptide (PICP) levels; however, no changes in α1 chain of procollagen type I and III expression were noted. Inhibition of α2β1 integrin by TC-I 15 (10^-7 and 10^-8 M) or α2 integrin subunit silencing augmented intracellular collagen level. Moreover, FAK or Src kinase inhibitors increased collagen content within the culture. Lower TIMP4 secretion was reported within the stiff gel cultures but neither MMP 2 nor TIMP-1, 2 or 3 release was altered. The stiff substrate cultures also demonstrated lower interleukin-6 release. Substrate stiffness modified collagen deposition within the atrial fibroblast and myofibroblast cultures. The elasticity of the cellular environment exerts a regulatory influence on both synthesis and breakdown of collagen. Integrin α2β1, FAK and Src kinase activity participates in signal transmission, which may influence fibrosis in the atria of the human heart.

Sodium-glucose Cotransporter 2 Inhibitors and Pathological Myocardial Hypertrophy

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a new type of oral hypoglycemic drugs that exert a hypoglycemic effect by blocking the reabsorption of glucose in the proximal renal tubules, thus promoting the excretion of glucose from urine. Their hypoglycemic effect is not dependent on insulin. Increasing data shows that SGLT2 inhibitors improve cardiovascular outcomes in patients with type 2 diabetes. Previous studies have demonstrated that SGLT2 inhibitors can reduce pathological myocardial hypertrophy with or without diabetes, but the exact mechanism remains to be elucidated. To clarify the relationship between SGLT2 inhibitors and pathological myocardial hypertrophy, with a view to providing a reference for the future treatment thereof, this study reviewed the possible mechanisms of SGLT2 inhibitors in attenuating pathological myocardial hypertrophy. We focused specifically on the mechanisms in terms of inflammation, oxidative stress, myocardial fibrosis, mitochondrial function, epicardial lipids, endothelial function, insulin resistance, cardiac hydrogen and sodium exchange, and autophagy.

Mechanisms of SGLT2 Inhibitors in Heart Failure and Their Clinical Value

ABSTRACT

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are widely used to treat diabetes mellitus. Abundant evidence has shown that SGLT2 inhibitors can reduce hospitalization for heart failure (HF) in patients with or without diabetes. An increasing number of studies are being conducted on the mechanisms of action of SGLT2 inhibitors in HF. Our review summarizes a series of clinical trials on the cardioprotective effects of SGLT2 inhibitors in the treatment of HF. We have summarized several classical SGLT2 inhibitors in cardioprotection research, including empagliflozin, dapagliflozin, canagliflozin, ertugliflozin, and sotagliflozin. In addition, we provided a brief overview of the safety and benefits of SGLT2 inhibitors. Finally, we focused on the mechanisms of SGLT2 inhibitors in the treatment of HF, including ion-exchange regulation, volume regulation, ventricular remodeling, and cardiac energy metabolism. Exploring the mechanisms of SGLT2 inhibitors has provided insight into repurposing these diabetic drugs for the treatment of HF.

Time-dependent Effects of Moderate- and High-intensity Exercises on Myocardial Transcriptomics

The heart is a highly adaptable organ that responds to changes in functional requirements due to exposure to internal and external stimuli. Physical exercise has unique stimulatory effects on the myocardium in both healthy individuals and those with health disorders, where the effects are primarily determined by the intensity and recovery time of exercise. We investigated the time-dependent effects of different exercise intensities on myocardial transcriptional expression in rats. Moderate intensity exercise induced more differentially expressed genes in the myocardium than high intensity exercise, while 16 differentially expressed genes were down-regulated by moderate intensity exercise but up-regulated by high intensity exercise at 12 h post- exercise. Both Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis indicated that moderate intensity exercise specifically regulated gene expression related to heart adaptation, energy metabolism, and oxidative stress, while high intensity exercise specifically regulated gene expression related to immunity, inflammation, and apoptosis. Moreover, there was increased expression of Tbx5, Casq1, Igsf1, and Ddah1 at all time points after moderate intensity exercise, while there was increased expression of Card9 at all time points after high intensity exercise. Our study provides a better understanding of the intensity dependent effects of physical exercise of the molecular mechanisms of cardiac adaptation to physical exercise.

Sodium-glucose co-transporter-2 inhibitors increase Klotho in patients with diabetic kidney disease: A clinical and experimental study

Sodium-glucose co-transporter-2 inhibitors (SGLT2i) provide cardiorenal protection. However, the molecular mechanisms remain poorly understood. We explored the impact of SGLT2i on Klotho, a kidney-derived protein with antiaging, renal-protective and heart-protective properties. A real world prospective observational study addressed the impact of initiating SGLT2i (canagliflozin, dapagliflozin, empagliflozin) or dipeptidyl peptidase-4 inhibitors (DPP4i) in patients with early diabetic kidney disease (DKD). Serum and urinary soluble Klotho, albuminuria and serum and urinary tumor necrosis factor-alpha (TNFa) were measured. The effect of SGLT2i on Klotho mRNA and protein was explored in vitro in kidney proximal tubular cells stressed with high glucose concentrations to simulate the diabetic milieu, albumin to simulate albuminuria, and the inflammatory cytokine TWEAK to simulate the inflammatory environment in DKD. Baseline urinary Klotho was negatively associated with albuminuria (r - 0.45, P < 0.001) and urinary TNFa (r - 0.40, P < 0.01). Both DPP4i and SGLT2i reduced HbA1c similarly, but only SGLT2i decreased eGFR, albuminuria and urinary TNFa and increased (P < 0.001) serum (5.2 %) and urinary Klotho (38.9 %). Changes in urinary TNFa (β - 0.53, P = 0.001) and albuminuria (β - 0.31, P < 0.05) were independently associated with changes in urinary Klotho (adjusted R² = 0.54, P < 0.001). Studies in renal tubular cells demonstrated that high glucose, albumin and TWEAK decreased Klotho mRNA expression and protein levels, an effect similarly prevented by SGLT2i. SGLT2i increase Klotho availability in type 2 diabetic patients with poorly controlled diabetes and early DKD, as well as in stressed tubular cells. This effect on Klotho may contribute to the kidney and heart protection afforded by SGLT2i.

Inhibition of activin A receptor signalling attenuates age-related pathological cardiac remodelling

In the heart, ageing is associated with DNA damage, oxidative stress, fibrosis and activation of the activin signalling pathway, leading to cardiac dysfunction. The cardiac effects of activin signalling blockade in progeria are unknown. This study investigated the cardiac effects of progeria induced by attenuated levels of Ercc1, which is required for DNA excision and repair, and the impact of activin signalling blockade using a soluble activin receptor type IIB (sActRIIB). DNA damage and oxidative stress were significantly increased in Ercc1^Δ/− hearts, but were reduced by sActRIIB treatment. sActRIIB treatment improved cardiac systolic function and induced cardiomyocyte hypertrophy in Ercc1^Δ/− hearts. RNA-sequencing analysis showed that in Ercc1^Δ/− hearts, there was an increase in pro-oxidant and a decrease in antioxidant gene expression, whereas sActRIIB treatment reversed this effect. Ercc1^Δ/− hearts also expressed higher levels of anti-hypertrophic genes and decreased levels of pro-hypertrophic ones, which were also reversed by sActRIIB treatment. These results show for the first time that inhibition of activin A receptor signalling attenuates cardiac dysfunction, pathological tissue remodelling and gene expression in Ercc1-deficient mice and presents a potentially novel therapeutic target for heart diseases.

Summary: Attenuated DNA repair is associated with pathological cardiac remodelling and gene expression. Much of this phenotype is attenuated by inhibition of the activin signalling pathway using soluble activin receptor treatment.

Sodium-Glucose Cotransporter 2 Inhibitors and Cardiac Remodeling

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have evident cardiovascular benefits in patients with type 2 diabetes with or at high risk for atherosclerotic cardiovascular disease, heart failure with reduced ejection fraction, heart failure with preserved ejection fraction (only empagliflozin and dapagliflozin have been investigated in this group so far), and chronic kidney disease. Prevention and reversal of adverse cardiac remodeling is one of the mechanisms by which SGLT2 inhibitors may exert cardiovascular benefits, especially heart failure-related outcomes. Cardiac remodeling encompasses molecular, cellular, and interstitial changes that result in favorable changes in the mass, geometry, size, and function of the heart. The pathophysiological mechanisms of adverse cardiac remodeling are related to increased apoptosis and necrosis, decreased autophagy, impairments of myocardial oxygen supply and demand, and altered energy metabolism. Herein, the accumulating evidence from animal and human studies is reviewed investigating the effects of SGLT2 inhibitors on these mechanisms of cardiac remodeling.