Background:
Sodium-glucose co-transporter 2 (SGLT2) inhibitors are antidiabetic drugs of great interest in cardiology due to their improvement of heart failure outcomes independent of diabetes. As SGLT2 is not expressed in cardiomyocytes, the mechanism of such benefit remains unclear. Elevated myocardial intracellular sodium [Na
+
]
i
has been found in heart failure and SGLT2 inhibition lowers [Na
+
]
i
in isolated cardiomyocytes. Elevated [Na
+
]
i
was shown to decrease mitochondrial calcium via mitochondrial Na/Ca exchanger (NCx
MITO
), resulting in decreased mitochondrial ATP synthesis. We have previously shown that mice fed a diet high in fat and sugar (HFHS) develop metabolic heart disease (MHD) characterized by decreased mitochondrial ATP synthesis with decreased phosphocreatine (PCr), worsened diastolic function and contractile reserve. We hypothesize that the SGLT2 inhibitor ertugliflozin (ERTU) decreases the elevated [Na
+
]
i
to improve energetics and contractile function in MHD.
Methods and Results:
Isolated hearts from mice after 6 months of HFHS vs. control diet (CD), +/- ERTU in the last month, were studied using
31
P and
23
Na NMR spectroscopy to measure PCr/ATP ratio and [Na
+
]
i
, respectively. As expected, HFHS hearts showed lower PCr/ATP, diastolic dysfunction (↑LVEDP) and lack of contractile reserve (↓RPP) during high work protocol compared to CD hearts. Myocardial [Na
+
]
i
was elevated more than 2-fold in HFHS compared to CD. One month of ERTU treatment decreased [Na
+
]
i
and improved energetics and contractile function in HFHS to levels similar to or better than CD. Perfusion with CGP 37157, which inhibits NCx
MITO
, improved PCr/ATP in HFHS hearts.
Conclusion:
Lowering of myocardial [Na
+
]
i
by ertugliflozin contributes to improved energetics and function in MHD. These results suggest targeting [Na
+
]
i
as an effective strategy to improve cardiac dysfunction in MHD and other forms of heart disease associated with elevated myocardial [Na
+
]
i.
Differential Effects of Sacubitril/Valsartan on Diastolic Function in Mice With Obesity-Related Metabolic Heart Disease
