title: Phytoceramide and sphingoid bases derived from brewer's yeast Saccharomyces pastorianus activate peroxisome proliferator-activated receptors.
abstract: BACKGROUND
  Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that regulate lipid and glucose metabolism. PPARα is highly expressed in the liver and controls genes involved in lipid catabolism. We previously reported that synthetic sphingolipid analogs, part of which contains shorter-length fatty acid chains than natural sphingolipids, stimulated the transcriptional activities of PPARs. Sphingosine and dihydrosphingosine (DHS) are abundant sphingoid bases, and ceramide and dihydroceramide are major ceramide species in mammals. In contrast, phytosphingosine (PHS) and DHS are the main sphingoid bases in fungi. PHS and phytoceramide exist in particular tissues such as the epidermis in mammals, and involvement of ceramide species in PPARβ activation in cultured keratinocytes has been reported. The purpose of the present study is to investigate whether natural sphingolipids with C18 fatty acid and yeast-derived sphingoid bases activate PPARs as PPAR agonists.
  
  
  METHODS
  Lipids of brewer's yeast contain PHS- and DHS-based sphingolipids. To obtain the sphingoid bases, lipids were extracted from brewer's yeast and acid-hydrolyzed. The sphingoid base fraction was purified and quantified. To assess the effects of sphingolipids on PPAR activation, luciferase reporter assay was carried out. NIH/3T3 and human hepatoma (HepG2) cells were transfected with expression vectors for PPARs and retinoid × receptors, and PPAR responsive element reporter vector. When indicated, the PPAR/Gal4 chimera system was performed to enhance the credibility of experiments. Sphingolipids were added to the cells and the dual luciferase reporter assay was performed to determine the transcriptional activity of PPARs.
  
  
  RESULTS
  We observed that phytoceramide increased the transcriptional activities of PPARs significantly, whereas ceramide and dihydroceramide did not change PPAR activities. Phytoceramide also increased transactivation of PPAR/Gal4 chimera receptors. Yeast-derived sphingoid base fraction, which contained PHS and DHS, or authentic PHS or DHS increased PPAR-dependent transcription. Additionally, phytoceramide stimulated PPARα activity in HepG2 hepatocytes, suggesting that phytoceramide activates genes regulated by PPARα.
  
  
  CONCLUSIONS
  Phytoceramide and yeast-derived sphingoid bases activate PPARs, whereas ceramide and dihydroceramide do not change the PPAR activity. The present findings suggest that phytoceramide acts as a PPAR ligand that would regulate PPAR-targeted genes.
authors.affiliation: Department of Biomembrane and Biofunctional Chemistry, Faculty of Advanced Life Sciences, Hokkaido University, Nishi 11, Kita 21, Kita-ku, Sapporo 001-0021, Japan.
authors.forename: Itsuo
authors.initials: I
authors.lastname: Murakami
authors.forename: Yukari
authors.initials: Y
authors.lastname: Wakasa
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamashita
authors.forename: Toshio
authors.initials: T
authors.lastname: Kurihara
authors.forename: Kota
authors.initials: K
authors.lastname: Zama
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Mizutani
authors.forename: Susumu
authors.initials: S
authors.lastname: Mitsutake
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Shigyo
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Igarashi
mesh_terms: D000818:Animals; D002518:Ceramides / Q000737:chemistry / Q000378:metabolism*; D017930:Genes, Reporter; D056945:Hep G2 Cells; D006801:Humans; D006900:Hydroxylation; D008024:Ligands; D051379:Mice; D041681:NIH 3T3 Cells; D010084:Oxidation-Reduction; D047492:Peroxisome Proliferator-Activated Receptors / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020218:Response Elements; D012440:Saccharomyces / Q000378:metabolism*; D013107:Sphingolipids / Q000737:chemistry / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D002518:Ceramides; D008024:Ligands; D047492:Peroxisome Proliferator-Activated Receptors; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D013107:Sphingolipids; C012491:phytosphingosine; D013110:Sphingosine; C005682:safingol