Elevated hepatic DPP4 activity promotes insulin resistance and non-alcoholic fatty liver disease

Baumeier, Christian; Schlüter, Luisa; Saussenthaler, Sophie; Laeger, Thomas; Rödiger, Maria; Alaze, Stella Amelie; Fritsche, Louise; Häring, Hans-Ulrich; Stefan, Norbert; Fritsche, Andreas; Schwenk, Robert Wolfgang; Schürmann, Annette

2.10. Cell culture Human hepatoma cells (HepG2) were cultured at 37 C and 5% CO 2 in Dulbecco's Modified Eagle Medium (DMEM) containing 5.5 mmol/l glucose, 10% fetal calf serum (FCS) and 1% non-essential amino acids (NEAA). Cells were treated with various concentrations of recombinant human DPP4 (1180-SE-010, R&D Systems) for 48 h before being serum-starved (3 h) and insulin-stimulated (10 min, 100 nmol/l). Primary hepatocytes were isolated from 12-week-old standard diet fed male C57BL/6J WT or Dpp4-Liv-Tg mice by a collagenase perfusion method [30] . Isolated hepatocytes were cultured in 12 well plates in DMEM with 5.5 mmol/l glucose, 10% FCS, 1% NEAA and 1% penicillin/streptomycin at 37 C and 5% CO 2 . After 4 h, cells were either infected with 3.5 Â 10 6 PFU/well adenovirus coding for full-length murine Dpp4 (Ad-Dpp4, ADV-257420) or green fluorescent protein (Gfp, Ad-Gfp, 1060) (Vector BioLabs), or treated with 500 ng/ml recombinant mouse DPP4 (954-SE-010, R&D Systems). Cells were cultured for 48 h, serum-starved (3 h) and subsequently stimulated with insulin (10 min, 100 nmol/l).