Limits...
Regulation of IGFBP-2 expression during fasting.

Kang HS, Kim MY, Kim SJ, Lee JH, Kim YD, Seo YK, Bae JH, Oh GT, Song DK, Ahn YH, Im SS - Biochem. J. (2015)

Bottom Line: Wy14643, a selective PPARα agonist, significantly induced Igfbp-2 gene expression in primary cultured hepatocytes.To explore the role of PPARα in IGF-1 signalling, we treated primary cultured hepatocytes with Wy14643 and observed a decrease in the number of IGF-1 receptors (IGF-1Rs) and in Akt phosphorylation.These results suggest that PPARα controls IGF-1 signalling through the up-regulation of hepatic Igfbp-2 transcription during fasting and Wy14643 treatment.

View Article: PubMed Central - PubMed

Affiliation: *Department of Physiology, Keimyung University School of Medicine, Daegu 704-701, Republic of Korea.

ABSTRACT
Insulin-like growth factor (IGF)-binding protein-2 (IGFBP-2), one of the most abundant circulating IGFBPs, is known to attenuate the biological action of IGF-1. Although the effect of IGFBP-2 in preventing metabolic disorders is well known, its regulatory mechanism remains unclear. In the present study, we demonstrated the transcriptional regulation of the Igfbp-2 gene by peroxisome-proliferator-activated receptor (PPAR) α in the liver. During fasting, both Igfbp-2 and PPARα expression levels were increased. Wy14643, a selective PPARα agonist, significantly induced Igfbp-2 gene expression in primary cultured hepatocytes. However, Igfbp-2 gene expression in Pparα mice was not affected by fasting or Wy14643. In addition, through transient transfection and chromatin immunoprecipitation assay in fasted livers, we determined that PPARα bound to the putative PPAR-responsive element between -511 bp and -499 bp on the Igfbp-2 gene promoter, indicating that the Igfbp-2 gene transcription is activated directly by PPARα. To explore the role of PPARα in IGF-1 signalling, we treated primary cultured hepatocytes with Wy14643 and observed a decrease in the number of IGF-1 receptors (IGF-1Rs) and in Akt phosphorylation. No inhibition was observed in the hepatocytes isolated from Pparα mice. These results suggest that PPARα controls IGF-1 signalling through the up-regulation of hepatic Igfbp-2 transcription during fasting and Wy14643 treatment.

Show MeSH

Related in: MedlinePlus

The IGF-1 signalling system is mediated by PPARα in primary hepatocytesWT and Pparα  mice were pretreated with Wy14643 for 6 h and then exposed to IGF-1 for 15 min under the indicated conditions. Whole cell extracts were isolated from primary hepatocytes of the indicated groups and assessed by Western blot analysis with various antibodies. Right panel indicate the density of Western blot bands measured with ImageJ software. *P<0.05 compared with untreated control or IGF-1-treated cells and #P<0.05 compared with IGF-1- and Wy14643-treated cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4403943&req=5

Figure 4: The IGF-1 signalling system is mediated by PPARα in primary hepatocytesWT and Pparα mice were pretreated with Wy14643 for 6 h and then exposed to IGF-1 for 15 min under the indicated conditions. Whole cell extracts were isolated from primary hepatocytes of the indicated groups and assessed by Western blot analysis with various antibodies. Right panel indicate the density of Western blot bands measured with ImageJ software. *P<0.05 compared with untreated control or IGF-1-treated cells and #P<0.05 compared with IGF-1- and Wy14643-treated cells.

Mentions: To determine the role of PPARα on hepatic IGF-1 signalling, we treated hepatocytes of WT and Pparα mice with IGF-1 and/or Wy14643. IGF-1-induced phosphorylation of IGF-1R and Akt were decreased significantly by Wy14643 in WT mice and the inhibitory effect of Wy14643 was abolished in Pparα mice (Figure 4). These findings suggest that PPARα may play a negative role in IGF-1 signal transduction in primary hepatocytes.


Regulation of IGFBP-2 expression during fasting.

Kang HS, Kim MY, Kim SJ, Lee JH, Kim YD, Seo YK, Bae JH, Oh GT, Song DK, Ahn YH, Im SS - Biochem. J. (2015)

The IGF-1 signalling system is mediated by PPARα in primary hepatocytesWT and Pparα  mice were pretreated with Wy14643 for 6 h and then exposed to IGF-1 for 15 min under the indicated conditions. Whole cell extracts were isolated from primary hepatocytes of the indicated groups and assessed by Western blot analysis with various antibodies. Right panel indicate the density of Western blot bands measured with ImageJ software. *P<0.05 compared with untreated control or IGF-1-treated cells and #P<0.05 compared with IGF-1- and Wy14643-treated cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403943&req=5

Figure 4: The IGF-1 signalling system is mediated by PPARα in primary hepatocytesWT and Pparα mice were pretreated with Wy14643 for 6 h and then exposed to IGF-1 for 15 min under the indicated conditions. Whole cell extracts were isolated from primary hepatocytes of the indicated groups and assessed by Western blot analysis with various antibodies. Right panel indicate the density of Western blot bands measured with ImageJ software. *P<0.05 compared with untreated control or IGF-1-treated cells and #P<0.05 compared with IGF-1- and Wy14643-treated cells.
Mentions: To determine the role of PPARα on hepatic IGF-1 signalling, we treated hepatocytes of WT and Pparα mice with IGF-1 and/or Wy14643. IGF-1-induced phosphorylation of IGF-1R and Akt were decreased significantly by Wy14643 in WT mice and the inhibitory effect of Wy14643 was abolished in Pparα mice (Figure 4). These findings suggest that PPARα may play a negative role in IGF-1 signal transduction in primary hepatocytes.

Bottom Line: Wy14643, a selective PPARα agonist, significantly induced Igfbp-2 gene expression in primary cultured hepatocytes.To explore the role of PPARα in IGF-1 signalling, we treated primary cultured hepatocytes with Wy14643 and observed a decrease in the number of IGF-1 receptors (IGF-1Rs) and in Akt phosphorylation.These results suggest that PPARα controls IGF-1 signalling through the up-regulation of hepatic Igfbp-2 transcription during fasting and Wy14643 treatment.

View Article: PubMed Central - PubMed

Affiliation: *Department of Physiology, Keimyung University School of Medicine, Daegu 704-701, Republic of Korea.

ABSTRACT
Insulin-like growth factor (IGF)-binding protein-2 (IGFBP-2), one of the most abundant circulating IGFBPs, is known to attenuate the biological action of IGF-1. Although the effect of IGFBP-2 in preventing metabolic disorders is well known, its regulatory mechanism remains unclear. In the present study, we demonstrated the transcriptional regulation of the Igfbp-2 gene by peroxisome-proliferator-activated receptor (PPAR) α in the liver. During fasting, both Igfbp-2 and PPARα expression levels were increased. Wy14643, a selective PPARα agonist, significantly induced Igfbp-2 gene expression in primary cultured hepatocytes. However, Igfbp-2 gene expression in Pparα mice was not affected by fasting or Wy14643. In addition, through transient transfection and chromatin immunoprecipitation assay in fasted livers, we determined that PPARα bound to the putative PPAR-responsive element between -511 bp and -499 bp on the Igfbp-2 gene promoter, indicating that the Igfbp-2 gene transcription is activated directly by PPARα. To explore the role of PPARα in IGF-1 signalling, we treated primary cultured hepatocytes with Wy14643 and observed a decrease in the number of IGF-1 receptors (IGF-1Rs) and in Akt phosphorylation. No inhibition was observed in the hepatocytes isolated from Pparα mice. These results suggest that PPARα controls IGF-1 signalling through the up-regulation of hepatic Igfbp-2 transcription during fasting and Wy14643 treatment.

Show MeSH
Related in: MedlinePlus