Insulin Inhibits Hepatocellular Glucose Production by Utilizing Liver-enriched Transcriptional Inhibitory Protein to Disrupt the Association of CREB-binding Protein and RNA Polymerase II with the Phosphoenolpyruvate Carboxykinase Gene Promoter

Abstract

Hormones regulate glucose homeostasis, in part, by controlling the expression of gluconeogenic enzymes, such as phosphoenolpyruvate carboxykinase (PEPCK). Insulin and glucocorticoids reciprocally regulate PEPCK expression primarily at the level of gene transcription. We demonstrate here that glucocorticoids promote, whereas insulin disrupts, the association of CREB-binding protein (CBP) and RNA polymerase II with the hepatic PEPCK gene promoter in vivo. We also show that accessory factors, such as CCAAT/enhancerbinding protein ␤ (C/EBP␤), can recruit CBP to drive transcription. Insulin increases protein levels of liverenriched transcriptional inhibitory protein (LIP), an inhibitory form of C/EBP␤, in a phosphatidylinositol 3-kinase-dependent manner. LIP concomitantly replaces liver-enriched transcriptional activator protein on the PEPCK gene promoter, which can abrogate the recruitment of CBP and polymerase II, culminating in the repression of PEPCK expression and the attenuation of hepatocellular glucose production.

The Synergistic Effect of Dexamethasone and All-trans-retinoic Acid on Hepatic Phosphoenolpyruvate Carboxykinase Gene Expression Involves the Coactivator p300

“…GR is only recruited to the PEPCK gene promoter when Dex is present (1-versus 13.0-fold), as shown previously (Fig. 7 and Table I) (18). This association is increased by the combined Dex/RA treatment (13.0 versus 21.2; Fig.…”

“…The forward primer used for the PEPCK gene promoter was 5Ј-GTTTCACGTCTCA-GAGCTGA-3Ј; the reverse primer was 5Ј-ACCGTGACTGTTGCT-GATGC-3Ј. The forward and reverse primers used for the ␤-actin gene promoter were described previously (18). PCR products were run on a 2% agarose gel and visualized by ethidium bromide staining.…”

Increased expression of CCAAT/enhancer binding protein-β and -δ and monocyte chemoattractant protein-1 genes in aortas from hyperinsulinaemic rats

“…The chromatin immunoprecipitation (ChIP) assay protocol was adapted from methods described elsewhere [17,18]. In brief, rat VSMCs (1×10 8 cells/condition) were cross-linked with 1% formaldehyde in PBS at 37°C for 15 min.…”

Identification and characterization of peroxisome proliferator response element in the mouse GLUT2 promoter

“…The ChIP assay protocol was adapted from methods as described by Duong et al (Duong et al, 2002). Adult male lean (+/+) and diabetic (ob/ob) mice (blood glucose level; 240 mg/dl) had free access to Purina chow.…”