Abstract
5-Aminoimidazole-4-carboxyamide-ribonucleoside (AICAR), a prodrug activator of AMP-activated protein kinase (AMPK), increased hepatic expression of cytochrome P450 4a10, 4a14, and 4a31 mRNAs 2-, 3-, and 4-fold, respectively, and liver microsomal lauric acid ω-hydroxylation increased 2.8-fold. Likewise, mRNA levels of the peroxisome proliferator-activated receptor α (PPARα)-responsive genes, Acox1, Acadm, Cpt1a, and Fabp1, were also increased by AICAR treatment. AICAR did not elicit these changes in PPARα null mice. In isolated murine hepatocytes, AICAR and adenosine produced similar effects, and these responses were blocked by the PPARα antagonist [(2S)-2-[[(1Z)-1-methyl-3-oxo-3-[4-(trifluoromethyl)phenyl]-1-propenyl]amino]-3-[4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]phenyl]propyl]-carbamic acid ethyl ester (GW6471). Inhibition of AMPK using compound C (dorsomorphin or 6-[4-(2-piperidin-1-ylethoxy)phenyl]-3-pyridin-4-ylpyrazolo[1,5-a]pyrimidine) did not block the induction of the PPARα-responsive genes by AICAR or adenosine, and 6,7-dihydro-4-hydroxy-3-(2′-hydroxy[1,1′-biphenyl]-4-yl)-6-oxo-thieno[2,3-b]pyridine-5-carbonitrile (A-769662), a non-nucleoside, direct activator of AMPK, did not increase expression of PPARα-responsive genes. An inhibitor of adenosine kinase, 5-iodotubercidin, blocked these responses, suggesting that the phosphorylation of AICAR and adenosine to AICAR 5′-monophosphate (ZMP) or AMP, respectively, was required. Concentrations of ZMP and AMP were elevated and ATP levels diminished at 24 h. The PPARα-dependent responses were associated with increased concentrations of oleic acid, a potent PPARα agonist, and diminished levels of oleoyl-CoA. Oleoyl-CoA synthase activity was inhibited by ZMP and AMP with IC50 values of 0.28 and 0.41 mM, respectively. These results suggest that PPARα is activated by increased concentrations of free fatty acids that may arise from impaired fatty acid metabolism caused by altered levels of ATP, AMP, and ZMP after AICAR or adenosine treatment.
Footnotes
This work was supported by the National Institutes of Health Eunice Kennedy Shriver National Institute of Child Health and Human Development [Grant R01-HD004445]. N.B. was the recipient of fellowships from the United Negro College Fund/Merck Science Initiative and the Joint University of San Diego/Scripps Research Institute Training for Future Faculty Program supported by the Fletcher Jones Foundation.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.111.184242.
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ABBREVIATIONS:
- Cyp4
- cytochrome P450 family 4
- AMPK
- AMP-activated protein kinase
- PPARα
- peroxisomal proliferator-activated receptor α
- Acox1
- acyl CoA oxidase 1
- Acadm
- acyl CoA dehydrogenase, medium chain
- Cpt1a
- carnitine palmitoyltransferase 1A
- Fabp1
- fatty acid binding protein
- AICAR
- 5-aminoimidazole-4-carboxyamide-ribonucleoside
- ZMP
- AICAR 5′-monophosphate
- Shp
- small heterodimer partner
- DMSO
- dimethyl sulfoxide
- qPCR
- quantitative real-time polymerase chain reaction
- ACSL
- ATP-dependent long-chain fatty acyl-CoA synthetase
- A-769662
- 6,7-dihydro-4-hydroxy-3-(2′-hydroxy[1,1′-biphenyl]-4-yl)-6-oxo-thieno[2,3-b]pyridine-5-carbonitrile
- compound C
- dorsomorphin or 6-[4-(2-piperidin-1-ylethoxy)phenyl]-3-pyridin-4-ylpyrazolo[1,5-a]pyrimidine
- WY14643
- [[4-chloro-6-[(2,3-dimethylphenyl)amino]-2-pyrimidinyl]thio]acetic acid
- GW6471
- [(2S)-2-[[(1Z)-1-methyl-3-oxo-3-[4-(trifluoromethyl)phenyl]-1-propenyl]amino]-3-[4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]phenyl]propyl]-carbamic acid ethyl ester.
- Received May 19, 2011.
- Accepted September 6, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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