Empagliflozin Decreases Lactate Generation in an NHE-1 Dependent Fashion and Increases α-Ketoglutarate Synthesis From Palmitate in Type II Diabetic Mouse Hearts

Abstract

Aims/hypothesis: Changes in cardiac metabolism and ion homeostasis precede and drive cardiac remodeling and heart failure development. We previously demonstrated that sodium/glucose cotransporter 2 inhibitors (SGLT2i's) have direct cardiac effects on ion homeostasis, possibly through inhibition of the cardiac sodium/hydrogen exchanger (NHE-1). Here, we hypothesize that Empagliflozin (EMPA) also possesses direct and acute cardiac effects on glucose and fatty acid metabolism of isolated type II diabetes mellitus (db/db) mouse hearts. In addition, we explore whether direct effects on glucose metabolism are nullified in the presence of an NHE-1 inhibitor.Methods: Langendorff-perfused type II diabetic db/db mouse hearts were examined in three different series: 1: 13C glucose perfusions (n = 32); 2: 13C palmitate perfusions (n = 13); and 3: 13C glucose + 10 μM Cariporide (specific NHE-1 inhibitor) perfusions (n = 17). Within each series, EMPA treated hearts (1 μM EMPA) were compared with vehicle-perfused hearts (0.02% DMSO). Afterwards, hearts were snap frozen and lysed for stable isotope analysis and metabolomics using LC-MS techniques. Hearts from series 1 were also analyzed for phosphorylation status of AKT, STAT3, AMPK, ERK, and eNOS (n = 8 per group).Results: Cardiac mechanical performance, oxygen consumption and protein phosphorylation were not altered by 35 min EMPA treatment. EMPA was without an overall acute and direct effect on glucose or fatty acid metabolism. However, EMPA did specifically decrease cardiac lactate labeling in the 13C glucose perfusions (13C labeling of lactate: 58 ± 2% vs. 50 ± 3%, for vehicle and EMPA, respectively; P = 0.02), without changes in other glucose metabolic pathways. In contrast, EMPA increased cardiac labeling in α-ketoglutarate derived from 13C palmitate perfusions (13C labeling of α-KG: 79 ± 1% vs. 86 ± 1% for vehicle and EMPA, respectively; P = 0.01). Inhibition of the NHE by Cariporide abolished EMPA effects on lactate labeling from 13C glucose.Conclusions: The present study shows for the first time that the SGLT2 inhibitor Empagliflozin has acute specific metabolic effects in isolated diabetic hearts, i.e., decreased lactate generation from labeled glucose and increased α-ketoglutarate synthesis from labeled palmitate. The decreased lactate generation by EMPA seems to be mediated through NHE-1 inhibition.

Direct cardiac effects of SGLT2 inhibitors

“…Few studies have examined direct cardiac metabolic effects of SGLT2i. In isolated type 2 diabetic mice hearts, metabolic effects of 35 min EMPA (1 μM) perfusion in the presence of albumin on 13 C-glucose or 13 C-palmitate metabolism have been examined [ 49 ]. Although EMPA was without an overall effect on the major metabolic pathways of glucose or fatty acid metabolism, EMPA did reduce lactate labeling from 13 C glucose, and increased α-ketoglutarate labelling from 13 C palmitate.…”

“…This is not possible in the in vivo condition because of the strong effect SGLT2i has on the kidney resulting in acute diuresis, natriuresis and glycosuria. During normoxic perfusion with a balanced physiological mixture of the important substrates for the heart, 1–3 μM SGLT2i in the absence or presence of albumin was without effect on any of the cardiac performance parameters of the healthy or type II diabetic mouse hearts [ 11 , 22 , 49 ]. In line with the supposed action of SGLT2is on the NHE, the NHE-1 inhibitor Cariporide was also without any effect on cardiac performance [ 22 ].…”

Sodium-glucose co-transporter 2 inhibitor empagliflozin inhibits the cardiac Na+/H+ exchanger 1: persistent inhibition under various experimental conditions

“…also provided data (cardiac mechanical function and energetics) showing that they were unable to find evidence of NHE-1-inhibition by EMPA in Langendorff-perfused healthy rat hearts, thereby reproducing our results in healthy mouse hearts. 2 However, under pathological conditions, EMPA delayed contracture development during ischaemia in healthy mouse hearts 3 and reduced lactate generation in diabetic hearts, 7 both in an NHE-1 dependent fashion. Of note, EMPA, in contrast to Cariporide, was unable to reduce the development of infarct size during reperfusion.…”

Cardiac mechanisms of the beneficial effects of SGLT2 inhibitors in heart failure: Evidence for potential off-target effects

“…In non-diabetic post-MI pig hearts, 2 months of empagliflozin treatment increased myocardial fatty acid uptake, whereas glucose uptake was severely decreased [140]. Employing an isolated heart model, metabolic effects of 35 min empagliflozin (1 μM) perfusion on carbohydrate and fatty acid metabolism were examined in hearts from T2DM mice [162]. There was no overall effect by empagliflozin on the major metabolic pathways of glucose or fatty acid metabolism.…”