4 We hypothesize that these differences may be due in part to a dysregulation of
the UPR in db/db mice that discourages cellular recovery and promotes further injury. The present results suggest that activation of the UPR and initiation of downstream inflammatory pathways may play a significant role in MCD induced steatohepatitis in db/db mice. ALT, alanine aminotransferase; ATF-4, activating transcription factor 4; ATF-6, activating transcription factor 6; CHOP, C/EBP homologous transcription factor; EDEM, enhancing α-mannosidase-like protein; ER, endoplasmic reticulum; ERO-1, oxireductase endoplasmic reticulum oxidoreductin-1; GADD34, growth arrest and DNA damage 34; IRE1α, inositol requiring 1α; JNK, c-Jun N-terminal CP868596 kinase; NF-κB, nuclear factor kappaB; MCD, methionine choline-deficient; Myd 116, myleloid differentiation response gene 116; NAFLD, nonalcoholic fatty liver disease; NASH, nonalcoholic steatohepatitis; PERK, PKR-like eukaryotic initiation factor 2 kinase; RT-PCR, real time quantitative polymerase chain reaction; TG, triglyceride; TNF-α, tumor necrosis
factor alpha; UPR, unfolded protein response. For all experiments, 8 to 10-week-old female db/db, db/m, and corresponding wildtype strain control C57BLKS/J selleck or C57BL/6 (only for experiments done for Supporting Fig. S1), (Jackson Laboratory, Bar Harbor, ME) were used. All mice were maintained under 12-hour light/dark cycles with unlimited access to regular chow and water until Molecular motor the first day
of the study. Mice then received the MCD diet or a nutritionally identical diet supplemented with methionine and choline to serve as the control. At the conclusion of each experiment mice were fasted for 4 hours and euthanized using CO2 narcosis. Whole blood was obtained from the right atrium by cardiac puncture and the livers were excised and weighed. Livers were flash-frozen in liquid nitrogen and stored at −70°C, with the exception of NF-κB experiments, in which nuclear extract was collected from fresh liver tissue. All animal experiments were approved by the Animal Care and Use Committee of Northwestern University Feinberg School of Medicine. Fasting blood glucose was measured by the glucose oxidase method using a reflectance glucometer (One Touch Ultra; LifeScan, Milpitas, CA). The determination of serum ALT was performed using a spectrophotometric assay kit on fresh plasma (Biotron, Hemet, CA). Triglyceride (TG) and cholesterol were measured enzymatically (Thermo Electron, Louisville, KY) on hepatic homogenate. Total RNA was extracted from liver by homogenizing snap-frozen liver tissue samples in TRIzol reagent (Invitrogen). Complementary DNA (cDNA) was synthesized from 2 μg of total RNA using the SuperScript First Strand System for real-time reverse-transcription PCR (RT-PCR) (Invitrogen), henceforth abbreviated RT-PCR, and random hexamer primers. The resulting cDNA was subsequently used as a template for quantitative RT-PCR.