Phytoceramide and sphingoid bases derived from brewer's yeast Saccharomyces pastorianus activate peroxisome proliferator-activated receptors

Abstract

BackgroundPeroxisome 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.MethodLipids 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.ResultsWe 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.ConclusionsPhytoceramide 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.

Improved High-Fat Diet-Induced Glucose Intolerance by an Oral Administration of Phytosphingosine

“…Our results therefore indicate that PHS and phCer in traditional Japanese fermented food might help to prevent the development of type 2 diabetes. 4) We have recently reported that 4,8-sphingadienine enhanced ceramide production in the skin by activating PPARs. 16) Since many other subclasses of sphingolipid are present in food, we should determine in a future study which type of sphingolipid is important in daily food.…”

“…4) PHS and phCer are the major sphingolipids in yeast and fungi, and are thus present in the fermented food consumed almost exclusively by the Japanese. Our results therefore indicate that PHS and phCer in traditional Japanese fermented food might help to prevent the development of type 2 diabetes.…”

“…We have already described synthetic ligands of PPAR being used to treat type 2 diabetes and we have previously reported that phCer and PHS activated PPAR. 4) We therefore next examined the effect of PHS on glucose intolerance, a major characteristic of type 2 diabetes. The intraperioneal glucose tolerance test (GTT) was performed as DES2 knockout (KO) mice were fed with a high-fat diet (HFD; D123492, Research Diet, New Brunswick, NJ, USA) supplemented or not with 0.2% PHS (Tokyo Chemical Industry, Tokyo, Japan) or a normal diet (ND; AIN76A, Nihon Nohsan Kogyo Co., Yokohama, Japan) from 4 to 22 weeks of age.…”

“…We have previously reported that phCer and PHS stimulated the transcriptional activities of peroxisome proliferator-activated receptor (PPAR), using a dual-luciferase reporter system. 3,4) PPAR is a ligand-activated transcriptional factor belonging to the nuclear receptor superfamily that has important roles in glucose and lipid homeostasis. 5) Such synthetic ligands of PPAR, as rosiglitazone and pioglitazone are widely used to treat type 2 diabetes.…”

Effects of <i>Asterias amurensis</i>-derived Sphingoid Bases on the <i>de novo</i> Ceramide Synthesis in Cultured Normal Human Epidermal Keratinocytes

“…Previous reports have shown that peroxisome proliferator-activated receptor PPAR agonists promote keratinocyte differentiation 32 . These PPARs can be activated by sphingoid bases 9,37,38 . According to Shirakura et al 9 , the activation of PPARγ requires a double bond at the C8 position of sphingoid bases.…”