bims-hafaim 2023-10-15 papers

Issue of 2023–10–15
four papers selected by
Kyle McCommis, Saint Louis University

Cardiovasc Res. 2023 Oct 11. pii: cvad157. [Epub ahead of print]

Empagliflozin improves cardiac energetics during ischaemia/reperfusion by directly increasing cardiac ketone utilisation.

Dylan Chase, Thomas R Eykyn, Michael J Shattock, Yu Jin Chung.

AIM: Empagliflozin (EMPA), a potent inhibitor of the renal sodium-glucose cotransporter 2 (SGLT2) and an effective treatment for type-2 diabetes, has been shown to have cardioprotective effects, independent of improved glycaemic control. Several non-canonical mechanisms have been proposed to explain these cardiac effects, including increasing circulating ketone supply to the heart. This study aims to test whether EMPA directly alters cardiac ketone metabolism independent of supply.
METHODS AND RESULTS: The direct effects of EMPA on cardiac function and metabolomics were investigated in Langendorff rat heart perfused in buffer containing 5 mM glucose, 4 mM β-hydroxybutyrate (βHb) and 0.4 mM intralipid, subject to low flow ischaemia/reperfusion. Cardiac energetics were monitored in situ using 31P NMR spectroscopy. Steady-state 13C-labelling was performed by switching 12C substrates for 13C1 glucose or 13C4 βHb, and 13C incorporation into metabolites determined using 2D 1H-13C HSQC NMR spectroscopy. EMPA treatment improved left ventricular developed pressure during ischaemia and reperfusion compared to vehicle-treated hearts. In EMPA-treated hearts, total ATP and PCr levels, and Gibbs free energy for ATP hydrolysis were significantly higher during ischaemia and reperfusion. EMPA treatment did not alter the incorporation of 13C from glucose into glycolytic products lactate or alanine neither during ischaemia nor reperfusion. In ischaemia, EMPA led to a decrease in 13C1 glucose incorporation and a concurrent increase in 13C4 βHb incorporation into TCA intermediates succinate, citrate, and glutamate. During reperfusion, the concentration of metabolites originating from 13C1 glucose was similar to vehicle but those originating from 13C4 βHb remained elevated in EMPA treated hearts.
CONCLUSIONS: Our findings indicate that EMPA causes a switch in metabolism away from glucose oxidation towards increased ketone utilisation in the rat heart, thereby improving function and energetics both during ischaemia and recovery during reperfusion. This preference of ketone utilisation over glucose was observed under conditions of constant supply of substrate, suggesting that EMPA acts directly by modulating cardiac substrate preference, independent of substrate availability. The mechanisms underlying our findings are currently unknown, warranting further study.
TRANSLATIONAL PERSPECTIVE: Heart failure remains a huge clinical burden. Clinical trials of SGLT2 inhibitors in patients with diabetes and heart failure have reported significant cardio-protection from EMPA treatment that appears independent of improved glycaemic control. The direct cardiac effect of EMPA in modulating ketone metabolism observed in this study raises the potential for EMPA to be used as a therapy for heart failure in both diabetic and non-diabetic patients alike.

DOI: https://doi.org/10.1093/cvr/cvad157

Basic Res Cardiol. 2023 Oct 11. 118(1): 45

Succinate dehydrogenase is essential for epigenetic and metabolic homeostasis in hearts.

Wenwen Li, Li Quan, Kun Peng, Yanru Wang, Xianhua Wang, Quan Chen, Heping Cheng, Qi Ma.

A hallmark of heart failure is a metabolic switch away from fatty acids β-oxidation (FAO) to glycolysis. Here, we show that succinate dehydrogenase (SDH) is required for maintenance of myocardial homeostasis of FAO/glycolysis. Mice with cardiomyocyte-restricted deletion of subunit b or c of SDH developed a dilated cardiomyopathy and heart failure. Hypertrophied hearts displayed a decrease in FAO, while glucose uptake and glycolysis were augmented, which was reversed by enforcing FAO fuels via a high-fat diet, which also improved heart failure of mutant mice. SDH-deficient hearts exhibited an increase in genome-wide DNA methylation associated with accumulation of succinate, a metabolite known to inhibit DNA demethylases, resulting in changes of myocardial transcriptomic landscape. Succinate induced DNA hypermethylation and depressed the expression of FAO genes in myocardium, leading to imbalanced FAO/glycolysis. Inhibition of succinate by α-ketoglutarate restored transcriptional profiles and metabolic disorders in SDH-deficient cardiomyocytes. Thus, our findings reveal the essential role for SDH in metabolic remodeling of failing hearts, and highlight the potential of therapeutic strategies to prevent cardiac dysfunction in the setting of SDH deficiency.

Keywords: DNA methylation; Heart failure; Myocardial metabolism; SDH; Succinate

DOI: https://doi.org/10.1007/s00395-023-01015-z

Biomed Pharmacother. 2023 Oct 09. pii: S0753-3322(23)01467-1. [Epub ahead of print]168 115669

Targeting mitochondrial quality control for diabetic cardiomyopathy: Therapeutic potential of hypoglycemic drugs.

Yutong Zhou, Wendong Suo, Xinai Zhang, Jiaojiao Liang, Weizhe Zhao, Yue Wang, Hong Li, Qing Ni.

Diabetic cardiomyopathy is a chronic cardiovascular complication caused by diabetes that is characterized by changes in myocardial structure and function, ultimately leading to heart failure and even death. Mitochondria serve as the provider of energy to cardiomyocytes, and mitochondrial dysfunction plays a central role in the development of diabetic cardiomyopathy. In response to a series of pathological changes caused by mitochondrial dysfunction, the mitochondrial quality control system is activated. The mitochondrial quality control system (including mitochondrial biogenesis, fusion and fission, and mitophagy) is core to maintaining the normal structure of mitochondria and performing their normal physiological functions. However, mitochondrial quality control is abnormal in diabetic cardiomyopathy, resulting in insufficient mitochondrial fusion and excessive fission within the cardiomyocyte, and fragmented mitochondria are not phagocytosed in a timely manner, accumulating within the cardiomyocyte resulting in cardiomyocyte injury. Currently, there is no specific therapy or prevention for diabetic cardiomyopathy, and glycemic control remains the mainstay. In this review, we first elucidate the pathogenesis of diabetic cardiomyopathy and explore the link between pathological mitochondrial quality control and the development of diabetic cardiomyopathy. Then, we summarize how clinically used hypoglycemic agents (including sodium-glucose cotransport protein 2 inhibitions, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, thiazolidinediones, metformin, and α-glucosidase inhibitors) exert cardioprotective effects to treat and prevent diabetic cardiomyopathy by targeting the mitochondrial quality control system. In addition, the mechanisms of complementary alternative therapies, such as active ingredients of traditional Chinese medicine, exercise, and lifestyle, targeting mitochondrial quality control for the treatment of diabetic cardiomyopathy are also added, which lays the foundation for the excavation of new diabetic cardioprotective drugs.

Keywords: DPP4i; Diabetic cardiomyopathy; GLP1-RA; Mitochondrial quality control; SGLT2i

DOI: https://doi.org/10.1016/j.biopha.2023.115669

Heart Fail Rev. 2023 Oct 12.

Autophagy protects mitochondrial health in heart failure.

Yating Tang, Wenlong Xu, Yu Liu, Jiajun Zhou, Kai Cui, Yanmei Chen.

The progression of heart failure is reported to be strongly associated with homeostatic imbalance, such as mitochondrial dysfunction and abnormal autophagy, in the cardiomyocytes. Mitochondrial dysfunction triggers autophagic and cardiac dysfunction. In turn, abnormal autophagy impairs mitochondrial function and leads to apoptosis or autophagic cell death under certain circumstances. These events often occur concomitantly, forming a vicious cycle that exacerbates heart failure. However, the role of the crosstalk between mitochondrial dysfunction and abnormal autophagy in the development of heart failure remains obscure and the underlying mechanisms are mainly elusive. The potential role of the link between mitochondrial dysfunction and abnormal autophagy in heart failure progression has recently garnered attention. This review summarized recent advances of the interactions between mitochondria and autophagy during the development of heart failure.

Keywords: Autophagy; Heart failure; Mitochondria health; Mitochondria-targeted therapeutics; Mitochondrial quality control

DOI: https://doi.org/10.1007/s10741-023-10354-x