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      SGLT2 Inhibitors Play a Salutary Role in Heart Failure via Modulation of the Mitochondrial Function

      review-article
      *
      Frontiers in Cardiovascular Medicine
      Frontiers Media S.A.
      SGLT2, mitochondria, ketone body, NHE, fusion, fission

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          Abstract

          Three cardiovascular outcome trials of sodium glucose cotransporter 2 (SGLT2) inhibitors, including the EMPA-REG OUTCOME trial, CANVAS Program, and DECLARE TIMI 58 trial, revealed that SGLT2 inhibitors were superior to a matching placebo in reducing cardiovascular events, including mortality and hospitalization for heart failure, in patients with type 2 diabetes. However, the detailed mechanism underlying the beneficial effects that SGLT2 inhibitors exert on cardiovascular diseases remains to be elucidated. We herein review the latest findings of the salutary mechanisms of SGLT2 inhibitors in cardiomyocytes, especially focusing on their mitochondrial function-mediated beneficial effects. The administration of SGLT2 inhibitors leads to the elevation of plasma levels of ketone bodies, which are an efficient energy source in the failing heart, by promoting oxidation of the mitochondrial coenzyme Q couple and enhancing the free energy of cytosolic ATP hydrolysis. SGLT2 inhibitors also promote sodium metabolism-mediated cardioprotective effects. These compounds could reduce the intracellular sodium overload to improve mitochondrial energetics and oxidative defense in the heart through binding with NHE and/or SMIT1. Furthermore, SGLT2 inhibitors could modulate mitochondrial dynamics by regulating the fusion and fission of mitochondria. Together with ongoing large-scale clinical trials to evaluate the efficacy of SGLT2 inhibitors in patients with heart failure, intensive investigations regarding the mechanism through which SGLT2 inhibitors promote the restoration in cases of heart failure would lead to the establishment of these drugs as potent anti-heart failure drugs.

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          Most cited references54

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          Myocardial fatty acid metabolism in health and disease.

          There is a constant high demand for energy to sustain the continuous contractile activity of the heart, which is met primarily by the beta-oxidation of long-chain fatty acids. The control of fatty acid beta-oxidation is complex and is aimed at ensuring that the supply and oxidation of the fatty acids is sufficient to meet the energy demands of the heart. The metabolism of fatty acids via beta-oxidation is not regulated in isolation; rather, it occurs in response to alterations in contractile work, the presence of competing substrates (i.e., glucose, lactate, ketones, amino acids), changes in hormonal milieu, and limitations in oxygen supply. Alterations in fatty acid metabolism can contribute to cardiac pathology. For instance, the excessive uptake and beta-oxidation of fatty acids in obesity and diabetes can compromise cardiac function. Furthermore, alterations in fatty acid beta-oxidation both during and after ischemia and in the failing heart can also contribute to cardiac pathology. This paper reviews the regulation of myocardial fatty acid beta-oxidation and how alterations in fatty acid beta-oxidation can contribute to heart disease. The implications of inhibiting fatty acid beta-oxidation as a potential novel therapeutic approach for the treatment of various forms of heart disease are also discussed.
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            Empagliflozin decreases myocardial cytoplasmic Na + through inhibition of the cardiac Na + /H + exchanger in rats and rabbits

            Aims/hypothesis Empagliflozin (EMPA), an inhibitor of the renal sodium–glucose cotransporter (SGLT) 2, reduces the risk of cardiovascular death in patients with type 2 diabetes. The underlying mechanism of this effect is unknown. Elevated cardiac cytoplasmic Na+ ([Na+]c) and Ca2+ ([Ca2+]c) concentrations and decreased mitochondrial Ca2+ concentration ([Ca2+]m) are drivers of heart failure and cardiac death. We therefore hypothesised that EMPA would directly modify [Na+]c, [Ca2+]c and [Ca2+]m in cardiomyocytes. Methods [Na+]c, [Ca2+]c, [Ca 2+]m and Na+/H+ exchanger (NHE) activity were measured fluorometrically in isolated ventricular myocytes from rabbits and rats. Results An increase in extracellular glucose, from 5.5 mmol/l to 11 mmol/l, resulted in increased [Na+]c and [Ca2+]c levels. EMPA treatment directly inhibited NHE flux, caused a reduction in [Na+]c and [Ca2+]c and increased [Ca2+]m. After pretreatment with the NHE inhibitor, Cariporide, these effects of EMPA were strongly reduced. EMPA also affected [Na+]c and NHE flux in the absence of extracellular glucose. Conclusions/interpretation The glucose lowering kidney-targeted agent, EMPA, demonstrates direct cardiac effects by lowering myocardial [Na+]c and [Ca2+]c and enhancing [Ca2+]m, through impairment of myocardial NHE flux, independent of SGLT2 activity. Electronic supplementary material The online version of this article (doi:10.1007/s00125-016-4134-x) contains peer-reviewed but unedited supplementary material, which is available to authorised users.
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              Can a Shift in Fuel Energetics Explain the Beneficial Cardiorenal Outcomes in the EMPA-REG OUTCOME Study? A Unifying Hypothesis.

              Type 2 diabetes mellitus causes excessive morbidity and premature cardiovascular (CV) mortality. Although tight glycemic control improves microvascular complications, its effects on macrovascular complications are unclear. The recent publication of the EMPA-REG OUTCOME study documenting impressive benefits with empagliflozin (a sodium-glucose cotransporter 2 [SGLT2] inhibitor) on CV and all-cause mortality and hospitalization for heart failure without any effects on classic atherothrombotic events is puzzling. More puzzling is that the curves for heart failure hospitalization, renal outcomes, and CV mortality begin to separate widely within 3 months and are maintained for >3 years. Modest improvements in glycemic, lipid, or blood pressure control unlikely contributed significantly to the beneficial cardiorenal outcomes within 3 months. Other known effects of SGLT2 inhibitors on visceral adiposity, vascular endothelium, natriuresis, and neurohormonal mechanisms are also unlikely major contributors to the CV/renal benefits. We postulate that the cardiorenal benefits of empagliflozin are due to a shift in myocardial and renal fuel metabolism away from fat and glucose oxidation, which are energy inefficient in the setting of the type 2 diabetic heart and kidney, toward an energy-efficient super fuel like ketone bodies, which improve myocardial/renal work efficiency and function. Even small beneficial changes in energetics minute to minute translate into large differences in efficiency, and improved cardiorenal outcomes over weeks to months continue to be sustained. Well-planned physiologic and imaging studies need to be done to characterize fuel energetics-based mechanisms for the CV/renal benefits.
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                Author and article information

                Contributors
                Journal
                Front Cardiovasc Med
                Front Cardiovasc Med
                Front. Cardiovasc. Med.
                Frontiers in Cardiovascular Medicine
                Frontiers Media S.A.
                2297-055X
                08 January 2020
                2019
                : 6
                : 186
                Affiliations
                Department of Cardiovascular Medicine, Tokyo Medical and Dental University , Tokyo, Japan
                Author notes

                Edited by: Junichi Sadoshima, University of Medicine and Dentistry of New Jersey, United States

                Reviewed by: Junco Shibayama Warren, The University of Utah, United States; Yoshiyuki Ikeda, Kagoshima University, Japan

                *Correspondence: Yasuhiro Maejima ymaeji.cvm@ 123456tmd.ac.jp

                This article was submitted to Cardiovascular Metabolism, a section of the journal Frontiers in Cardiovascular Medicine

                Article
                10.3389/fcvm.2019.00186
                6960132
                31970162
                80a4ae17-abff-4ebe-944f-0437c0aed8b6
                Copyright © 2020 Maejima.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 03 November 2019
                : 10 December 2019
                Page count
                Figures: 4, Tables: 1, Equations: 0, References: 82, Pages: 13, Words: 8530
                Categories
                Cardiovascular Medicine
                Review

                sglt2,mitochondria,ketone body,nhe,fusion,fission
                sglt2, mitochondria, ketone body, nhe, fusion, fission

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