Activation of Peroxisome Proliferator-activated Receptor α Increases the Expression and Activity of Microsomal Triglyceride Transfer Protein in the Liver

• Published in: The Journal of biological chemistry 2005-01, Vol.280 (2), p.1224-1229
• Main Authors: Améen, Caroline, Edvardsson, Ulrika, Ljungberg, Anna, Asp, Lennart, Åkerblad, Peter, Tuneld, Anna, Olofsson, Sven-Olof, Lindén, Daniel, Oscarsson, Jan
• Format: Article
• Language: English
• Subjects: Alitretinoin; Animals; Apolipoproteins B - metabolism; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Line; Cells, Cultured; Dactinomycin - pharmacology; Gene Expression Regulation - drug effects; Hepatocytes - drug effects; Hepatocytes - metabolism; Liver - cytology; Liver - drug effects; Liver - metabolism; Male; Mice; Mice, Inbred C57BL; PPAR alpha - metabolism; Promoter Regions, Genetic - genetics; Pyrimidines - pharmacology; Rats; Rats, Sprague-Dawley; RNA, Messenger - genetics; RNA, Messenger - metabolism; Rosiglitazone; Thiazolidinediones - pharmacology; Transcription, Genetic - drug effects; Tretinoin - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M412107200

Microsomal triglyceride transfer protein (MTP) is rate-limiting in the assembly and secretion of lipoproteins containing apolipoprotein (apo) B. Previously we demonstrated that Wy 14,643 (Wy), a peroxisome proliferator-activated receptor (PPAR) α agonist, increases apoB-100 secretion despite decreased triglyceride synthesis. In this study, we sought to determine whether PPARα activation increases MTP expression and activity. Treatment with Wy increased hepatic MTP expression and activity in rats and mice and increased MTP expression in primary cultures of rat and mouse hepatocytes. Addition of actinomycin D blocked this increase and the MTP promoter (–136 to +67) containing a conserved DR1 element was activated by Wy, showing that PPARα activates transcription of the gene. Wy did not affect MTP expression in the intestine or in cultured hepatocytes from PPARα-null mice. A retinoid X receptor agonist (9-cis-retinoic acid), but not a PPARγ agonist (rosiglitazone), increased MTP mRNA expression in cultured hepatocytes from both wild type and PPARα-null mice. In rat hepatocytes incubated with Wy, MTP mRNA levels increased between 6 and 24 h, and MTP protein expression and apoB-100 secretion increased between 24 and 72 h. In conclusion, PPARα activation stimulates hepatic MTP expression via increased transcription of the Mtp gene. This effect is paralleled by a change in apoB-100 secretion, indicating that the effect of Wy on apoB-100 secretion is mediated by increased expression of MTP.