Animals

PGRN heterozygous KO mice, developed by Kayasuga et al.²⁴, were purchased from RIKEN BioResource Center (Ibaraki, Japan). Genotyping of PGRN homozygous KO mice was performed as described previously²⁴. WT C57BL/6J mice were used as controls. Mice were individually housed in plastic cages with free access to food and water throughout the experiment. Specifically, 8-week-old mice were randomly divided into four groups to be fed the HFD (WT-HFD and KO-HFD groups; 5.2 kcal/g, 60% of calories from fat [35%/g]; D12492; Research Diets, New Brunswick, NJ, USA) or the standard diet (SD) (WT-SD and KO-SD groups; 3.39 kcal/g, 4.6/g; CE-2; CLEA Japan, Tokyo, Japan) for 12 weeks. All mice were maintained in the same room under specific pathogen-free conditions with a regular 12-h light/dark cycle and a temperature controlled at 24 ± 1 °C. At 20 weeks of age, all mice were sacrificed under intraperitoneally anesthesia with 50 mg/kg sodium pentobarbital to obtain kidney, epididymal white adipose tissue, and blood samples. Blood samples were collected from the left ventricle. All animal experiments were approved by the Ethics Review Committee for Animal Experimentation of Juntendo University Faculty of Medicine (document no. 1312), and all animals were treated according to the guidelines for animal experimentation of Juntendo University in Tokyo, Japan.