Background. Sodium/glucose co-transporter 2 (SGLT-2) inhibitors, e.g. empagliflozin (empa), and glucagon like peptide 1 receptor (GLP-1R) agonists, such as semaglutide (sema), improve the outcome of patients with heart failure. The underlying mechanisms are, however, unresolved. Since obesity is an important risk factor for the development of heart failure with preserved ejection fraction (HFpEF), we evaluated the impact of a combinatory treatment with empa and sema on excitation-contraction coupling and mitochondrial energetics in a rat model with diet-induced obesity.

Methods and results. Male Wistar rats were fed a high fat, high fructose diet (HFD) for 8 weeks to induce obesity. Afterwards, rats received empagliflozin (Empa; 10mg/kg/day via drinking water) and sema (120μg/kg/day s.c.) or regular tap water and saline s.c. (CO) for 8-weeks, and could choose between HFD and low fat diet. Treatment with empa+sema led to a maximum body weight loss of 11.2%, whereas animals of the CO group gained weight continuously (up to +8%). Cardiac ventricular myocytes and mitochondria were isolated from n=3 or 6 rats per group, respectively. Sarcomere length, cytosolic Ca²⁺ (Indo1, AM), mitochondrial redox state (autofluorescence of NAD(P)H and FAD), membrane potential (TMRM) and ROS (DCF) were determined in myocytes using an automatic Ionoptix fluorescence setup. Pacing at 0.3 Hz, followed by β-adrenergic stimulation and increasing stimulation rate to 3 Hz for 3 minutes was employed to subject cardiac myocytes to simulate a physiological increase in workload. Empa+sema treatment lowered [Ca²⁺]_i and also the magnitude of cytosolic Ca²⁺-transients (n=70/58 CO/empa). Diastolic sarcomere length (n=100/60 CO/empa) was slightly extended, although fractional sarcomere shortening was unchanged. ROS generation was significantly increased (n=56/49 CO/empa), but mitochondrial redox state (n=46/52 CO/empa) and membrane potential (n=69/60 CO/empa) were unaffected. In isolated mitochondria, complex I (pyruvate/malate) or complex II respiration (with succinate), Ca²⁺-retention capacity detected by Calcium-Green, mitochondrial membrane potential using TMRM as well as NAD(P)H levels were unaltered after empa and sema compared to CO treatment.

Conclusion. In a rat model of diet-induced obesity, in vivo treatment with empagliflozin+semaglutide  lowers cytosolic Ca²⁺ concentrations, but leads to a slight diastolic dysfunction on sarcomere function, while fractional sarcomere shortening is unchanged without adverse effects on mitochondrial redox state, membrane potential, but increased  ROS generation. These data warrant further studies into the impact of empa and sema on mechano-energetic coupling also in rats in which obesity is combined with hypertension to induce HFpEF.