AMPK enhances the expression of pancreatic duodenal homeobox-1 via PPARα, but not PPARγ, in rat insulinoma cell line INS-1
Abstract
Aim: To investigate whether AMP-activated protein kinase (AMPK) regulates the expression of pancreatic duodenal homeobox-1 (PDX-1), a β-cell-specific transcription factor and whether PPARα/γ is involved in the regulation of pancreatic β-cell lines after acute stimulation.
Methods: Rat insulinoma cell line INS-1 was treated with an activator (AICAR) or inhibitor (Compound C) of AMPK as well as inhibitors of PPARs (MK886 to PPARα and BADGE to PPARγ). The mRNA levels of PDX-1, PPARα and PPARγ were measured using real-time RT-PCR, and Western blotting was used to detect the protein expression of these factors.
Results: Activation of AMPK by AICAR induced significantly increased the expression of PDX-1, and this increase was abrogated when AMPK was inactivated by Compound C. Similarly, the expression of PPARα and PPARγ was also increased by AICAR or decreased by Compound C. However AMPK activation did not increase nuclear PDX-1 protein levels when PPARα was inhibited. In contrast, AMPK activation still up-regulated PDX-1 protein levels during PPARγ inhibition. Additionally, PPARα activation induced by fenofibrate significantly enhanced nuclear PDX-1 protein expression.
Conclusion: AMPK regulates the expression of PDX-1 at both the transcriptional and protein levels, and PPARα may be acutely involved in the regulation of INS-1 cells.
Keywords:
Methods: Rat insulinoma cell line INS-1 was treated with an activator (AICAR) or inhibitor (Compound C) of AMPK as well as inhibitors of PPARs (MK886 to PPARα and BADGE to PPARγ). The mRNA levels of PDX-1, PPARα and PPARγ were measured using real-time RT-PCR, and Western blotting was used to detect the protein expression of these factors.
Results: Activation of AMPK by AICAR induced significantly increased the expression of PDX-1, and this increase was abrogated when AMPK was inactivated by Compound C. Similarly, the expression of PPARα and PPARγ was also increased by AICAR or decreased by Compound C. However AMPK activation did not increase nuclear PDX-1 protein levels when PPARα was inhibited. In contrast, AMPK activation still up-regulated PDX-1 protein levels during PPARγ inhibition. Additionally, PPARα activation induced by fenofibrate significantly enhanced nuclear PDX-1 protein expression.
Conclusion: AMPK regulates the expression of PDX-1 at both the transcriptional and protein levels, and PPARα may be acutely involved in the regulation of INS-1 cells.