L-carnitine and PPAR[alpha]-agonist fenofibrate are involved in the regulation of Carnitine Acetyltransferase mRNA levels in murine liver cells

• Published in: BMC genomics 2014-06, Vol.15 (1), p.514-514
• Main Authors: Kienesberger, Klemens, Pordes, Aniko Ginta, Völk, Thomas Georg, Hofbauer, Reinhold
• Format: Article
• Language: English
• Subjects: Analysis; Biotechnology; Cell culture; Colleges & universities; Experiments; Genetic aspects; Genomics; Glucose; Health aspects; Levocarnitine; Messenger RNA; Molecular biology; Perutz, Max; Physiological aspects; Protein binding; Proteins; Statistical analysis
• ISSN: 1471-2164; 1471-2164
• DOI: 10.1186/1471-2164-15-514

The carnitine acetyltransferase (CrAT) is a mitochondrial matrix protein that directly influences intramitochondrial acetyl-CoA pools. Murine CrAT is encoded by a single gene located in the opposite orientation head to head to the PPP2R4 gene, sharing a very condensed bi-directional promoter. Since decreased CrAT expression is correlated with metabolic inflexibility and subsequent pathological consequences, our aim was to reveal and define possible activators of CrAT transcription in the normal embryonic murine liver cell line BNL CL. 2 and via which nuclear factors based on key metabolites mainly regulate hepatic expression of CrAT. Here we describe a functional characterization of the CrAT promoter region under conditions of L-carnitine deficiency and supplementation as well as fenofibrate induction in cell culture cells. The murine CrAT promoter displays some characteristics of a housekeeping gene: it lacks a TATA-box, is very GC-rich and harbors two Sp1 binding sites. Analysis of the promoter activity of CrAT by luciferase assays uncovered a L-carnitine sensitive region within -342 bp of the transcription start. Electrophoretic mobility shift and supershift assays proved the sequence element (-228/-222) to be an L-carnitine sensitive RXR[alpha] binding site, which also showed sensitivity to application of anti-PPAR[alpha] and anti-PPARbp antibodies. In addition we analysed this specific RXR[alpha]/PPAR[alpha] site by Southwestern Blotting technique and could pin down three protein factors binding to this promoter element. By qPCR we could quantify the nutrigenomic effect of L-carnitine itself and fenofibrate. Our results indicate a cooperative interplay of L-carnitine and PPAR[alpha] in transcriptional regulation of murine CrAT, which is of nutrigenomical relevance. We created experimental proof that the muCrAT gene clearly is a PPAR[alpha] target. Both L-carnitine and fenofibrate are inducers of CrAT transcripts, but the important hyperlipidemic drug fenofibrate being a more potent one, as a consequence of its pharmacological interaction.