title: Lipid Abundance in Zebrafish Embryos Is Regulated by Complementary Actions of the Endocannabinoid System and Retinoic Acid Pathway.
abstract: The endocannabinoid system (ECS) and retinoic acid (RA) signaling have been associated with influencing lipid metabolism. We hypothesized that modulation of these pathways could modify lipid abundance in developing vertebrates and that these pathways could have a combinatorial effect on lipid levels. Zebrafish embryos were exposed to chemical treatments altering the activity of the ECS and RA pathway. Embryos were stained with the neutral lipid dye Oil-Red-O (ORO) and underwent whole-mount in situ hybridization (WISH). Mouse 3T3-L1 fibroblasts were differentiated under exposure to RA-modulating chemicals and subsequently stained with ORO and analyzed for gene expression by qRT-PCR. ECS activation and RA exposure increased lipid abundance and the expression of lipoprotein lipase. In addition, RA treatment increased expression of CCAAT/enhancer-binding protein alpha. Both ECS receptors and RA receptor subtypes were separately involved in modulating lipid abundance. Finally, increased ECS or RA activity ameliorated the reduced lipid abundance caused by peroxisome proliferator-activated receptor gamma (PPARγ) inhibition. Therefore, the ECS and RA pathway influence lipid abundance in zebrafish embryos and have an additive effect when treated simultaneously. Furthermore, we demonstrated that these pathways act downstream or independently of PPARγ to influence lipid levels. Our study shows for the first time that the RA and ECS pathways have additive function in lipid abundance during vertebrate development.
authors.affiliation: Metabolic Research Unit, Deakin University School of Medicine, Geelong 3217, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Fraher
authors.affiliation: Metabolic Research Unit, Deakin University School of Medicine, Geelong 3217, Australia.
authors.forename: Megan K
authors.initials: MK
authors.lastname: Ellis
authors.affiliation: Metabolic Research Unit, Deakin University School of Medicine, Geelong 3217, Australia.
authors.forename: Shona
authors.initials: S
authors.lastname: Morrison
authors.affiliation: Metabolic Research Unit, Deakin University School of Medicine, Geelong 3217, Australia.
authors.forename: Sean L
authors.initials: SL
authors.lastname: McGee
authors.affiliation: Metabolic Research Unit, Deakin University School of Medicine, Geelong 3217, Australia.
authors.forename: Alister C
authors.initials: AC
authors.lastname: Ward
authors.affiliation: Metabolic Research Unit, Deakin University School of Medicine, Geelong 3217, Australia.
authors.forename: Ken
authors.initials: K
authors.lastname: Walder
authors.affiliation: Metabolic Research Unit, Deakin University School of Medicine, Geelong 3217, Australia.
authors.forename: Yann
authors.initials: Y
authors.lastname: Gibert
mesh_terms: D041721:3T3-L1 Cells; D050156:Adipogenesis / Q000187:drug effects; D000818:Animals; D001391:Azo Compounds / Q000737:chemistry; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D063388:Endocannabinoids / Q000378:metabolism* / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D050356:Lipid Metabolism / Q000235:genetics; D008055:Lipids / Q000032:analysis*; D051379:Mice; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D043884:Receptor, Cannabinoid, CB1 / Q000235:genetics / Q000378:metabolism; D043885:Receptor, Cannabinoid, CB2 / Q000235:genetics / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013194:Staining and Labeling / Q000379:methods; D014212:Tretinoin / Q000378:metabolism* / Q000494:pharmacology; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D001391:Azo Compounds; D063388:Endocannabinoids; D008055:Lipids; D047495:PPAR gamma; C000607072:Rara protein, mouse; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D029961:Zebrafish Proteins; D014212:Tretinoin; C011049:oil red O