The liver samples were collected from ad libitum feeding 10-week-old wild-type and ob/ob mice. Tissues were lysed with 0.5 mL of a solution containing 50 mM Tris-HCl pH8.8, 2% sodium dodecyl sulfate (SDS), and 7 M urea, and then homogenized by ultrasonication using a Bioruptor (Digaenode, Denville, NJ, USA). After dilution with equal amount of water, the samples were centrifuged at 15,000 g for 15 min at 4°C to exclude the insoluble fractions. Bicinchoninic acid (BCA) assay (Thermo Fisher Scientific) was used to quantify the protein concentration of the lysates, and lysate concentration was adjusted to 1 mg/mL. Cysteine residues were blocked using 2 mM Tris (2-carboxyethyl) phosphine hydrochloride (TCEP) (Thermo Fisher Scientific) at 37 °C for 30 min followed by alkylation with 10 mM 2-iodoacetamide (IAA) at room temperature for 30 min. Proteins were precipitated by addition of acetone. The resulting protein pellet was digested with trypsin in 100 mM ammonium bicarobonate. To enrich the phosphopeptides, the resulting peptides (1 mg) were subjected to Fe3+-IMAC. All samples were analyzed with Orbitrap Exploris 480 mass spectrometer (Thermo Fisher Scientific) equipped with the UltiMate 3000 RSLCnano LC system (Thermo Fisher Scientific) via a nano-electrospray source with a column oven set at 60°C (AMR Inc.). Peptides were directly injected onto a 75 μm × 120 mm column (Nikkyo Technos Co.,Ltd., Tokyo, Japan) with a linear gradient of 5–32% B for 70 min and 32–65% B for 10 min at a flow rate of 200 nL/min, where A is 0.1% formic acid and B is 0.1% formic acid and 80% acetonitrile.