Insulin resistance and heart failure during treatment with sodium glucose cotransporter 2 inhibitors: proposed role of ketone utilization

Protein succinylation: regulating metabolism and beyond

Modifications of protein post-translation are critical modulatory processes, which alters target protein biological activity，function and/or location, even involved in pathogenesis of some diseases. So far, there are at least 16 types of post-translation modifications identified, particularly through recent mass spectrometry analysis. Among them, succinylation (Ksuc) on protein lysine residues causes a variety of biological changes. Succinylation of proteins contributes to many cellular processes such as proliferation, growth, differentiation, metabolism and even tumorigenesis. Mechanically, Succinylation leads to conformation alteration of chromatin or remodeling. As a result, transcription/expression of target genes is changed accordingly. Recent research indicated that succinylation mainly contributes to metabolism modulations, from gene expression of metabolic enzymes to their activity modulation. In this review, we will conclude roles of succinylation in metabolic regulation of glucose, fat, amino acids and related metabolic disease launched by aberrant succinylation. Our goal is to stimulate extra attention to these still not well researched perhaps important succinylation modification on proteins and cell processes.

Immunomodulation and immunopharmacology in heart failure

The immune system is intimately involved in the pathophysiology of heart failure. However, it is currently underused as a therapeutic target in the clinical setting. Moreover, the development of novel immunomodulatory therapies and their investigation for the treatment of patients with heart failure are hampered by the fact that currently used, evidence-based treatments for heart failure exert multiple immunomodulatory effects. In this Review, we discuss current knowledge on how evidence-based treatments for heart failure affect the immune system in addition to their primary mechanism of action, both to inform practising physicians about these pleiotropic actions and to create a framework for the development and application of future immunomodulatory therapies. We also delineate which subpopulations of patients with heart failure might benefit from immunomodulatory treatments. Furthermore, we summarize completed and ongoing clinical trials that assess immunomodulatory treatments in heart failure and present several therapeutic targets that could be investigated in the future. Lastly, we provide future directions to leverage the immunomodulatory potential of existing treatments and to foster the investigation of novel immunomodulatory therapeutics.

Effects of dapagliflozin monotherapy and combined aerobic exercise on skeletal muscle mitochondrial quality control and insulin resistance in type 2 diabetes mellitus rats

Type 2 diabetes mellitus (T2DM) is a prevalent, chronic metabolic disease. Sodium-glucose cotransporter-2 (SGLT2) inhibitors and aerobic exercise (AE) have shown promise in mitigating insulin resistance (IR) and T2DM. This study investigated the effects of dapagliflozin (Dapa) monotherapy and combined AE on mitochondrial quality control (MQC) in skeletal muscle and IR in T2DM rats. T2DM rats, induced by a high-fat diet/streptozotocin model, were randomly assigned to the following groups: T2DM+vehicle group (DMV), T2DM rats treated with Dapa (DMDa, 10 mg/kg/d), T2DM rats subjected to combined Dapa treatment and AE (DMDa+AE), and the standard control group (CON). Blood and skeletal muscle samples were collected after 6 weeks of intragastric administration and treadmill exercise. The results showed that DMDa monotherapy could reduce the accumulation of white adipose tissue and skeletal muscle lipid droplets and improve HOMA-IR. While the combined AE led to further reductions in subcutaneous white adipose tissue and fasting glucose levels, it did not confer additional benefits in terms of HOMA-IR. Furthermore, Dapa monotherapy enhanced skeletal muscle mitochondrial biogenesis (PGC-1α, NRF1, TFAM, and COX IV), mitochondrial dynamics (OPA1, DRP1, and MFN2), and mitophagy (PGAM5 and PINK1) related protein levels. Nevertheless, the combination of Dapa with AE treatment did not yield an additive effect. In conclusion, this study highlights the potential of SGLT2 inhibitors, specifically Dapa, in ameliorating IR and maintaining MQC in skeletal muscle in rats with T2DM. However, combined AE did not produce an additive effect, indicating the need for further research.

Triglyceride glucose index and its combination with the Get with the Guidelines-Heart Failure score in predicting the prognosis in patients with heart failure

Background

Heart failure (HF) is associated with generalized insulin resistance (IR). Recent studies demonstrated that triglyceride glucose (TyG) is an effective alternative index of IR. However, the relationship between the TyG index and in-hospital mortality in patients with HF is unclear. In the present study, we aimed to clarify the association between the TyG index and in-hospital mortality in patients with HF.

Methods

A retrospective study consisting of 4,411 patients diagnosed with HF from 2015 to 2018 was conducted. All-cause mortality during hospitalization was the primary endpoint. The association between the TyG index and in-hospital mortality was assessed using the logistic regression analysis.

Results

The risk of in-hospital mortality was significantly associated with increased TyG index (OR: 1.886, 95% CI: 1.421–2.501, p < 0.001) under logistic regression with multivariable adjustment. When divided into three groups based on the TyG index, Tertile 3 demonstrated significantly higher in-hospital mortality than the other two Tertiles (OR: 2.076, 95% CI: 1.284–3.354, p = 0.001). Moreover, the TyG index improved the prediction efficiency of the Get with the Guidelines-Heart Failure (GWTG-HF) score (absolute integrated discrimination improvement = 0.006, p < 0.001; category-free net reclassification improvement = 0.075, p = 0.005). In subgroup analysis, the TyG index exhibited similar predictive performance of in-hospital mortality when groups were stratified based on type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD).

Conclusion

TyG is a potential index for predicting in-hospital mortality in patients with HF, independent of T2DM or CAD status. The TyG index may be combined with the GWTG-HF score to further improve its predictive efficacy.

Association between serum insulin levels and heart failure-related parameters in patients with type 2 diabetes and heart failure treated with canagliflozin: a post-hoc analysis of the randomized CANDLE trial

Background

Insulin resistance and hyperinsulinemia in patients with type 2 diabetes (T2D) are adversely associated with the development and worsening of heart failure (HF). Herein, we sought to investigate the effect of canagliflozin on insulin concentrations and the associations of changes in insulin concentrations with HF-related clinical parameters in patients with T2D and HF.

Methods

This was a post-hoc analysis of the investigator-initiated, multicenter, open-label, randomized, controlled CANDLE trial for patients with T2D and chronic HF (UMIN000017669). The endpoints were the effects of 24 weeks of canagliflozin treatment, relative to glimepiride treatment, on insulin concentrations and the relationship between changes in insulin concentrations and clinical parameters of interest, including New York Heart Association (NYHA) classification. The effects of canagliflozin on those parameters were also analyzed by baseline insulin level.

Results

Among the participants in the CANDLE trial, a total of 129 patients (canagliflozin, n = 64; glimepiride, n = 65) who were non-insulin users with available serum insulin data both at baseline and week 24 were included in this analysis. Overall, the mean age was 69.0 ± 9.4 years; 75% were male; the mean HbA1c was 6.8 ± 0.7%; and the mean left ventricular ejection fraction was 59.0 ± 14.1%, with parameters roughly balanced between treatment groups. Canagliflozin treatment significantly reduced insulin concentrations at week 24 (p < 0.001), and the between-group difference (canagliflozin minus glimepiride) in those changes was − 3.52 mU/L (95% confidence interval, − 4.85 to − 2.19; p < 0.001). Decreases in insulin concentrations, irrespective of baseline insulin level, were significantly associated with improvement in NYHA class in patients treated with canagliflozin.

Conclusion

Our findings suggest that canagliflozin treatment in patients with T2D and HF ameliorated excess insulin overload, contributing to the improvement of clinical HF status.

Trial registration: University Medical Information Network Clinical Trial Registry, number 000017669, Registered on May 25, 2015.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01589-3.

Could SGLT2 Inhibitors Improve Exercise Intolerance in Chronic Heart Failure?

Despite the constant improvement of therapeutical options, heart failure (HF) remains associated with high mortality and morbidity. While new developments in guideline-recommended therapies can prolong survival and postpone HF hospitalizations, impaired exercise capacity remains one of the most debilitating symptoms of HF. Exercise intolerance in HF is multifactorial in origin, as the underlying cardiovascular pathology and reactive changes in skeletal muscle composition and metabolism both contribute. Recently, sodium-related glucose transporter 2 (SGLT2) inhibitors were found to improve cardiovascular outcomes significantly. Whilst much effort has been devoted to untangling the mechanisms responsible for these cardiovascular benefits of SGLT2 inhibitors, little is known about the effect of SGLT2 inhibitors on exercise performance in HF. This review provides an overview of the pathophysiological mechanisms that are responsible for exercise intolerance in HF, elaborates on the potential SGLT2-inhibitor-mediated effects on these phenomena, and provides an up-to-date overview of existing studies on the effect of SGLT2 inhibitors on clinical outcome parameters that are relevant to the assessment of exercise capacity. Finally, current gaps in the evidence and potential future perspectives on the effects of SGLT2 inhibitors on exercise intolerance in chronic HF are discussed.

Hepatocyte-specific fibroblast growth factor 21 overexpression ameliorates high-fat diet-induced obesity and liver steatosis in mice

Fibroblast growth factor (FGF) 21 is an endocrine growth factor mainly secreted by the liver in response to a ketogenic diet and alcohol consumption. FGF21 signaling requires co-receptor β-klotho (KLB) co-acting with FGF receptors, which has pleiotropic metabolic effects, including induced hepatic fatty acid oxidation and ketogenesis, in human and animal models of obesity. We examined the hepatocyte-specific enhancer/promoter of FGF21 expression plasmids in high-fat diet-fed mice for 12 weeks. Hydrodynamic injection for FGF21 delivery every 6 weeks sustained high circulating levels of FGF21, resulting in marked reductions in body weight, epididymal fat mass, insulin resistance, and liver steatosis. FGF21-induced lipolysis in the adipose tissue enabled the liver to be flooded with fat-derived FFAs. The hepatic expression of Glut2 and Bdh1 was upregulated, whereas that of gluconeogenesis-related genes, G6p and Pepck, and lipogenesis-related genes, Srebp-1 and Srebp-2, was significantly suppressed. FGF21 induced the phosphorylation of AMPK at Thr172 and Raptor at ser792 and suppressed that of mTOR at ser2448, which downregulated mTORC1 signaling and reduced IRS-1 phosphorylation at ser1101. Finally, in the skeletal muscle, FGF21 increased Glut4 and Mct2, a membrane protein that acts as a carrier for ketone bodies. Enzymes for ketone body catabolism (Scot) and citrate cycle (Cs, Idh3a), and a marker of regenerating muscle (myogenin) were also upregulated via increased KLB expression. Thus, FGF21-induced lipolysis was continuously induced by a high-fat diet and fat-derived FFAs might cause liver damage. Hepatic fatty acid oxidation and ketone body synthesis may act as hepatic FFAs' disposal mechanisms and contribute to improved liver steatosis. Liver-derived ketone bodies might be used for energy in the skeletal muscle. The potential FGF21-related crosstalk between the liver and extraliver organs is a promising strategy to prevent and treat metabolic syndrome-related nonalcoholic steatohepatitis.

Towards precision medicine in heart failure

The number of therapies for heart failure (HF) with reduced ejection fraction has nearly doubled in the past decade. In addition, new therapies for HF caused by hypertrophic and infiltrative disease are emerging rapidly. Indeed, we are on the verge of a new era in HF in which insights into the biology of myocardial disease can be matched to an understanding of the genetic predisposition in an individual patient to inform precision approaches to therapy. In this Review, we summarize the biology of HF, emphasizing the causal relationships between genetic contributors and traditional structure-based remodelling outcomes, and highlight the mechanisms of action of traditional and novel therapeutics. We discuss the latest advances in our understanding of both the Mendelian genetics of cardiomyopathy and the complex genetics of the clinical syndrome presenting as HF. In the phenotypic domain, we discuss applications of machine learning for the subcategorization of HF in ways that might inform rational prescribing of medications. We aim to bridge the gap between the biology of the failing heart, its diverse clinical presentations and the range of medications that we can now use to treat it. We present a roadmap for the future of precision medicine in HF.

β-Hydroxybutyrate inhibits cardiac microvascular collagen 4 accumulation by attenuating oxidative stress in streptozotocin-induced diabetic rats and high glucose treated cells

Accumulation of collagen 4 (COL4) and thickened basement membrane are features of diabetic cardiac microvascular fibrosis that may be induced by oxidative stress. The ketone body β-hydroxybutyrate exhibits various cardiovascular protective effects, however its mechanism remains to be clarified. In the current study, the effects of β-hydroxybutyrate on cardiac microvascular fibrosis and COL4 accumulation were evaluated in streptozotocin-induced diabetic rats and in high glucose (HG) treated human cardiac microvascular endothelial cells (HCMECs). Generations of inducible nitric oxide synthase (iNOS) and copper-zinc superoxide dismutase (Cu/Zn-SOD), and the amount of nitrotyrosine (NT) were measured in vivo and in vitro. Ten weeks of β-hydroxybutyrate treatment (160, 200 and 240 mg/kg/d) attenuated cardiac microvascular fibrosis and inhibited cardiac COL4 generation and microvascular distribution in diabetic rats. Furthermore, β-hydroxybutyrate promoted cardiac Cu/Zn-SOD generation and reduced NT content, without reducing iNOS generation in diabetic rats. In HCMECs, stimulation with HG induced excess generation of COL4 via peroxynitrite. β-Hydroxybutyrate treatment (2, 4, 6 mM) attenuated HG-stimulated COL4 accumulation in a concentration-dependent manner. Similarly, 4 mM β-hydroxybutyrate promoted Cu/Zn-SOD generation and reduced NT content, without affecting excess iNOS generation in HG-stimulated HCMECs. In conclusion, this study showed that β-hydroxybutyrate promoted Cu/Zn-SOD generation, reduced peroxynitrite and inhibited cardiac microvascular COL4 accumulation in diabetes.

SGLT2 inhibitors break the vicious circle between heart failure and insulin resistance: targeting energy metabolism

Heart failure (HF) often coexists with insulin resistance (IR), and the incidence of HF in type 2 diabetes mellitus (T2DM) patients is significantly higher. The reciprocal relationship between HF and IR has long been recognized, and the integration complicates the therapy of both. A number of mechanisms ascribe to the progression of cardiac IR, in which the main factors are the shift of myocardial substrate metabolism. Studies have found that SGLT2 inhibitors, an anti-diabetic drug, can improve the cardiac prognosis of patients with T2DM, which may be at least partially due to the relief of cardiac IR. Basic and clinical studies have revealed the important role of cardiac IR in the pathogenesis and progression of HF, and studies suggest that energy metabolism plays an important role in the pathogenesis of cardiac IR and HF. SGLT2 inhibitors mediated cardiovascular benefits through various mechanisms such as improving substrate utilization and improving myocardial energy. The regulation of SGLT2 inhibitors on cardiac energy status including carbohydrates, fatty acids (FA), amino acids and ketones, ATP transfer to the cytoplasm, and mitochondrial functional status have received extensive attention in HF, but its specific mechanism of action is still unclear. Therefore, this article reviews the relationship between IR and HF from the perspective of energy metabolism; subsequently, targeting energy metabolism discusses the pivotal role of SGLT2 inhibitors in improving cardiac IR and HF based on basic and clinical research evidences, and sought to clarify the molecular mechanism involved. (Fig. 1).

Beneficial effects on kidney during treatment with sodium-glucose cotransporter 2 inhibitors: proposed role of ketone utilization

Modestly elevated circulating levels of the ketone β-hydroxybutyrate (βOHB) during treatment with sodium-glucose cotransporter 2 (SGLT2) inhibitors cause different beneficial effects on organs and cells, depending on the succinyl-CoA:3-ketoacid CoA transferase (SCOT) level. In the failing heart, SCOT is highly expressed/up-regulated, and thus, βOHB may be an energy source, in addition to fat and glucose oxidation. However, SCOT is not highly expressed/down-regulated in the kidney, and thus, βOHB may cause different beneficial effects, rather than acting as an alternative energy source in patients with chronic kidney disease (CKD). βOHB is an endogenous and specific inhibitor of class I histone deacetylases (HDACs) and the NLRP3 inflammasome, accumulates in the kidney because of its decreased utilization as an energy source due to the down-regulation of SCOT, and may induce beneficial effects such as inhibiting inflammation, oxidative stress, and fibrosis. In addition to restoring tubulo-glomerular feedback and improving renal proximal tubule oxygenation, SGLT2 inhibitors may play a renoprotective role by way of βOHB in patients with CKD.

The dawn of the four-drug era? SGLT2 inhibition in heart failure with reduced ejection fraction

Sodium-glucose cotransporter type 2 (SGLT2) inhibitors are a relatively new class of antihyperglycemic drug with salutary effects on glucose control, body weight, and blood pressure. Emerging evidence now indicates that these drugs may have a beneficial effect on outcomes in heart failure with reduced ejection fraction (HFrEF). Post-approval cardiovascular outcomes data for three of these agents (canagliflozin, empagliflozin, and dapagliflozin) showed an unexpected improvement in cardiovascular endpoints, including heart failure hospitalization and mortality, among patients with type 2 diabetes mellitus (T2DM) and established cardiovascular disease or risk factors. These studies were followed by a placebo controlled trial of dapagliflozin in patients with HFrEF both with and without T2DM, showing a reduction in all-cause mortality comparable to current guideline-directed HFrEF medical therapies such as angiotensin-converting enzyme inhibitors and beta-blockers. In this review, we discuss the current landscape of evidence, safety and adverse effects, and proposed mechanisms of action for use of these agents for patients with HFrEF. The United States (US) and European guidelines are reviewed, as are the current US federally approved indications for each SGLT2 inhibitor. Use of these agents in clinical practice may be limited by an uncertain insurance environment, especially in patients without T2DM. Finally, we discuss practical considerations for the cardiovascular clinician, including within-class differences of the SGLT2 inhibitors currently available on the US market (217/300).