Animals and experimental procedure

All the animal procedures were approved by the ethics committee of Aix-Marseille University and complied with the European Convention for the protection of animals used for experimental purposes. Animal MRI experiments were carried out on a 4.7T Bruker Biospec Avance system (Bruker, Ettlingen, Germany) dedicated to rodent exploration and equipped with a 70 mm birdcage TX resonator and a decoupled surface receive coil.

Thirty-four C57BL/6 8-week-old male mice (Janvier, France) were housed in a controlled environment under standard laboratory conditions (12–12 h light–dark cycle, 22 °C). The mice were randomly divided into: Control (n = 10) with standard diet (#U8224G10R, Safe Diets, France) and HFHS (n = 24) diet (#U8978P Version 0019, Safe Diets, France) as previously described [20] (Fig. 1). At 4 weeks, metabolic status (intraperitoneal glucose tolerance test (IPGTT), glucagon, insulin and blood ketones) and MRI evaluation of ectopic fat stores (liver and myocardial, as rodents have no epicardial fat) were performed. The HFHS group was then randomly divided into two subgroups, EMPA (n = 12), with empagliflozin in water (30 mg/kg bodyweight + 0.1% DMSO (Sigma, USA)), and a placebo group HFHS (n = 12) with 0.1% DMSO in water. Metabolic status and MRI evaluation were performed after 4 and 12 weeks of treatment. At 24 weeks, mice were sacrificed, and tissues (heart, liver) collected (Additional file 1: Appendix S1).

Study design and flow chart. a Mice design. b Human design. IPGTT, intraperitoneal glucose tolerance test; MRI, magnetic resonance imaging; MRS, magnetic resonance spectroscopy