PPARalpha regulates the hepatotoxic biomarker alanine aminotransferase (ALT1) gene expression in human hepatocytes.
In this work, we investigated a potential mechanism behind the observation of increased aminotransferase levels in a phase I clinical trial using a lipid-lowering drug, the peroxisome proliferator-activated receptor (PPAR) alpha agonist, AZD4619. In healthy volunteers treated with AZD4619, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were elevated without an increase in other markers for liver injury. These increases in serum aminotransferases have previously been reported in some patients receiving another PPARalpha agonist, fenofibrate. In subsequent in vitro studies, we observed increased expression of ALT1 protein and mRNA in human hepatocytes after treatment with fenofibric acid. The PPAR effect on ALT1 expression was shown to act through a direct transcriptional mechanism involving at least one PPAR response element (PPRE) in the proximal ALT1 promoter, while no effect of fenofibrate and AZD4619 was observed on the ALT2 promoter. Binding of PPARs to the PPRE located at -574 bp from the transcriptional start site was confirmed on both synthetic oligonucleotides and DNA in hepatocytes. These data show that intracellular ALT expression is regulated by PPAR agonists and that this mechanism might contribute to increased ALT activity in serum.
Thulin
Petra
P
Atherosclerosis Research Unit, Department of Medicine, Center for Molecular Medicine, Karolinska Institutet, S-171 76 Stockholm, Sweden.
Rafter
Ingalill
I
Stockling
Kenneth
K
Tomkiewicz
Celine
C
Norjavaara
Ensio
E
Aggerbeck
Martine
M
Hellmold
Heike
H
Ehrenborg
Ewa
E
Andersson
Ulf
U
Cotgreave
Ian
I
Glinghammar
Björn
B
D000328:Adult; D000410:Alanine Transaminase / Q000096:biosynthesis* / Q000235:genetics; D015415:Biomarkers; D056486:Chemical and Drug Induced Liver Injury / Q000201:enzymology*; D002843:Chromatin / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D011345:Fenofibrate / Q000031:analogs & derivatives / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics / Q000502:physiology*; D022781:Hepatocytes / Q000201:enzymology*; D006801:Humans; D000960:Hypolipidemic Agents / Q000009:adverse effects / Q000494:pharmacology; D047468:Immunoprecipitation; D008156:Luciferases / Q000235:genetics; D008297:Male; D016296:Mutagenesis / Q000187:drug effects; D047493:PPAR alpha / Q000819:agonists* / Q000502:physiology*; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D020218:Response Elements / Q000235:genetics / Q000502:physiology; D014162:Transfection
D015415:Biomarkers; D002843:Chromatin; D000960:Hypolipidemic Agents; D047493:PPAR alpha; D012313:RNA; C006012:fenofibric acid; D008156:Luciferases; D000410:Alanine Transaminase; D011345:Fenofibrate