In Cardiac Myocytes the SGLT2 Inhibitor Ertugliflozin Attenuates Cytosolic Ca2+ Peaks After Adrenergic Stimulation

Abstract

A novel class of antidiabetic drugs, called gliflozins, inhibit sodium-glucose cotransporter 2 (SGLT2i) to lower blood glucose levels in patients with Type 2 diabetes (T2DM). Gliflozins reduce mortality and heart failure (HF) hospitalizations in HF patients with or without T2DM, but the molecular mechanisms are unclear. We hypothesize that modulating effects on cardiac calcium homeostasis are involved in SGLT2i-induced benefits during HF, and that the SGLT2i ertugliflozin (ERTU) will alter cytosolic calcium concentration ([Ca2+]cyt) in contracting cardiomyocytes after adrenergic stimulation. Cardiomyocytes were isolated from 0–2-day old C57BL/6J mice, treated for 72 hours with either ERTU (100 nM, and 1 μM), the NHE-1 inhibitor cariporide (CARI, 10 μM), ERTU and CARI, or vehicle (Ctrl). After 72 hours, cells were either A) loaded with Fura-2, baseline cytosolic calcium levels ([Ca2+]cyt) recorded, cells stimulated with phenylephrine (PE, 100 μM), and [Ca2+]cyt recorded for additional 30 minutes, B) lysed and protein isolated for analysis by immunoblotting, or C) fixed for immunohistochemical assessment. Results: 100 nM and 1 uM ERTU reduced [Ca2+]cyt peaks after PE, but 100 nM ERTU to a lesser degree. In contrast, 72-hour-long NHE1 inhibition with CARI increased [Ca2+]cyt at baseline when compared to vehicle and ERTU, and further enhanced [Ca2+]cyt peaks after PE. Immunoblotting revealed increased protein levels of S16 phosphorylated phospholamban, decreased total phospholamban, and upregulated sarcomeric α-actinin post-ERTU. Immunohistochemical assessment of sarcomeric α-actinin localization revealed improved sarcomeric Z-line organization after ERTU administration. Sustained exposure to the SGLT2i ERTU reduced, but the NHE-1 inhibitor CARI increased [Ca2+]cyt in contracting cardiac myocytes. These data indicate that ERTU’s beneficial effect on [Ca2+]cyt homeostasis is independent of NHE1 inhibition. Since disturbed calcium handling and calcium overload are hallmarks of HF, reduced [Ca2+]cyt levels after sympathetic stimulation may contribute to the cardioprotective effect of SGLT2i. Further studies are needed to unravel the molecular mechanisms behind ERTU’s influence on cardiac calcium homeostasis. This study was funded by Merck & Co., Inc. (Kenilworth, NJ). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.