Liver-Specific PPAR-γ Knockout Mice

Liver-specific PPARγ knockout (KO) mice were generated by breeding PPARγ-loxP mice (The Jackson Laboratory, Bar Harbor, ME) to transgenic Alb-Cre (B6.Cg-Tg (Alb-Cre) 21Mgn/J, The Jackson Laboratory) mice as previously described [25 (link)]. Two-month-old male KO or control (i.e., wildtype (WT) C57BL6/J; The Jackson Laboratory) mice were given ad lib access to sterile, irradiated low-fat (S4031, BioServ, Flemington, NJ) or high-fat (S3282, BioServ; 60% kcal from fat) diets, with or without 0.01% (w/w) pioglitazone hydrochloride (Pio, Sigma-Aldrich, St. Louis, MO) for 3 months (n = 4 − 5 mice/experimental group). Body weight was measured weekly and body composition analyzed at the experimental endpoint by ECHO MRI spectroscopy [26 (link)]; after which, mice were euthanized for tissue harvest and analysis. Blood glucose, serum insulin and free fatty acid levels, and liver histology and triglyceride content were determined as previously described [25 (link)–27 (link)]. All experiments were approved by the Washington University Institutional Animal Care and Use Committee (IACUC), and all animals received humane care in accordance with institutional guidelines and criteria in the “Guide for the Care and Use of Laboratory Animals” (8^th edition, 2011, https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf).