Involvement of transcription factor C/EBP-beta in stimulation of PEPCK gene expression during exercise

Abstract

Prolonged exercise increases gluconeogenesis and activates transcription of the hepatic phosphoenol pyruvate carboxykinase (PEPCK) gene. The mechanisms that regulate the transcriptional control of gene expression depend on the interaction of nuclear proteins with distinct DNA sequences. To determine the involvement with the liver-enriched transcription factor CCAAT/enhancer binding protein beta (C/EMP-beta) in the induction of PEPCK gene transcription during prolonged exercise or adenosine 3',5'-cyclic monophosphate (cAMP) treatment, we examined C/EBP-beta mRNA and nuclear protein concentrations, as well as C/EBP-beta binding to the PEPCK promoter at the cAMP response element (CRE)(-87/-74) and P3I (-248/-230) binding sites. The requirement of these DNA elements for exercise-induced stimulation of PEPCK gene expression was established in transgenic mice carrying -460 +/- 73 of the PEPCK promoter with a mutation in either the CRE or P3I binding domain linked to a bovine growth hormone (bGH) reporter gene. In mice carrying the intact promoter, prolonged exercise increased the concentration of liver bGH mRNA by 510% compared with an increase of only 270% in mice with a mutation in either the CRE or P3I site. Exercise or cAMP injection induced a 7.5- and 13-fold increase in nuclear C/EBP-beta protein, respectively. In electrophoretic mobility shift assays (EMSA), the total quantity of nuclear proteins bound to either oligomer was not altered by treatment. However, addition of C/EBP-beta antisera in the EMSA in a supershift assay indicated that liver nuclear extracts from exercised or cAMP-treated mice demonstrated significantly greater DNA binding due to C/EBP-beta (CRE: control 44.4 +/- 2.3%, exercise 56.7% +/- 2.2%, cAMP 54.5 +/- 3.6% of total binding, P < 0.001; P3I: control 35.8 +/- 2.5%, exercise 64.9 +/- 1.9%, cAMP 57.3 +/- 2.5% of total binding, P < 0.001). Taken together, these results suggest that exercise and cAMP treatment induce a transient increase in C/EBP-beta that may contribute to the molecular mechanism for signaling PEPCK gene transcription and increasing gluconeogenesis during exercise.

CCAAT/Enhancer-binding Protein β Is an Accessory Factor for the Glucocorticoid Response from the cAMP Response Element in the Rat Phosphoenolpyruvate Carboxykinase Gene Promoter

“…The following year, in accordance with previous work published by this lab, Angrand et al (49) found that a full glucocorticoid response for PEPCK requires the CRE. Soon afterward, in a set of in vivo studies using transgenic mice, Friedman and colleagues (50,51) correlated the dramatic increase in C/EBP␤ levels with the CRE-dependent glucocorticoid induction of PEPCK gene transcription during exercise.…”

Role of CCAAT Enhancer-binding Protein β in the Thyroid Hormone and cAMP Induction of Phosphoenolpyruvate Carboxykinase Gene Transcription

“…Other data indicate that the binding of C/EBP␤ to the PEPCK promoter may be increased by cAMP. When animals are injected with cAMP, the abundance of C/EBP␤ rises rapidly in the liver and the binding of C/EBP␤ to the P3(I) site increases (37). In physiologic situations such as with increased exercise, the abundance of C/EBP␤ increases in the liver (37).…”

“…When animals are injected with cAMP, the abundance of C/EBP␤ rises rapidly in the liver and the binding of C/EBP␤ to the P3(I) site increases (37). In physiologic situations such as with increased exercise, the abundance of C/EBP␤ increases in the liver (37). Our data 3 responsiveness to a PEPCK promoter HepG2 cells were transfected with 5 g of Ϫ490-PCAT, 5 g of RSV-TR␤, 5 g of Gal4-C/EBP␣ fusion plasmid, and 5 g of SV40-␤-gal as described in Table I demonstrate that, when C/EBP␤ is bound to the P3(I) site, it can stimulate basal expression and contribute to cAMP responsiveness.…”

Activation of the mitogen-activated protein kinase (MAPK) signalling pathway in the liver of mice is related to plasma glucose levels after acute exercise

“…The metabolic adaptation to exercise is not restricted to the working muscle. It has been recognised for decades that the liver, as a major regulator of glucose and lipid homoeostasis, also responds to acute exercise, and increased activities of the gluconeogenic enzymes as well as decreased lipogenic enzyme activities have been found [18][19][20]. Compared with the numerous reports on the transcriptional regulation of genes in the working muscle, remarkably little data on exercise-induced gene expression in the liver are available.…”