title: Stearoyl-CoA Desaturase 1 Is a Key Determinant of Membrane Lipid Composition in 3T3-L1 Adipocytes.
abstract: Stearoyl-CoA desaturase 1 (SCD1) is a lipogenic enzyme important for the regulation of membrane lipid homeostasis; dysregulation likely contributes to obesity associated metabolic disturbances. SCD1 catalyses the Δ9 desaturation of 12-19 carbon saturated fatty acids to monounsaturated fatty acids. To understand its influence in cellular lipid composition we investigated the effect of genetic ablation of SCD1 in 3T3-L1 adipocytes on membrane microdomain lipid composition at the species-specific level. Using liquid chromatography/electrospray ionisation-tandem mass spectrometry, we quantified 70 species of ceramide, mono-, di- and trihexosylceramide, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, bis(monoacylglycero)phosphate, phosphatidylinositol and cholesterol in 3T3-L1 adipocytes in which a 90% reduction in scd1 mRNA expression was achieved with siRNA. Cholesterol content was unchanged although decreases in other lipids resulted in cholesterol accounting for a higher proportion of lipid in the membranes. This was associated with decreased membrane lateral diffusion. An increased ratio of 24:0 to 24:1 in ceramide, mono- and dihexosylceramide, and sphingomyelin likely also contributed to this decrease in lateral diffusion. Of particular interest, we observed a decrease in phospholipids containing arachidonic acid. Given the high degree of structural flexibility of this acyl chain this will influence membrane lateral diffusion, and is likely responsible for the transcriptional activation of Lands' cycle enzymes lpcat3 and mboat7. Of relevance these profound changes in the lipidome were not accompanied by dramatic changes in gene expression in mature differentiated adipocytes, suggesting that adaptive homeostatic mechanisms to ensure partial maintenance of the biophysical properties of membranes likely occur at a post-transcriptional level.
authors.affiliation: Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Sergio
authors.initials: S
authors.lastname: Rodriguez-Cuenca
authors.affiliation: Genetics and Molecular Pathology, SA Pathology, Adelaide, Australia.
authors.forename: Lauren
authors.initials: L
authors.lastname: Whyte
authors.affiliation: Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Rachel
authors.initials: R
authors.lastname: Hagen
authors.affiliation: Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.|Wellcome Trust Sanger Institute, Hinxton, United Kingdom.
authors.forename: Antonio
authors.initials: A
authors.lastname: Vidal-Puig
authors.affiliation: Genetics and Molecular Pathology, SA Pathology, Adelaide, Australia.|University of Adelaide, North Terrace, Adelaide, SA 5000, Australia.
authors.forename: Maria
authors.identifier: http://orcid.org/0000-0001-9092-8942
authors.initials: M
authors.lastname: Fuller
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D002853:Chromatography, Liquid; D005227:Fatty Acids / Q000096:biosynthesis; D015870:Gene Expression; D008563:Membrane Lipids / Q000378:metabolism*; D051379:Mice; D021241:Spectrometry, Mass, Electrospray Ionization; D013230:Stearoyl-CoA Desaturase / Q000235:genetics / Q000378:metabolism*; D053719:Tandem Mass Spectrometry
chemical_list: D005227:Fatty Acids; D008563:Membrane Lipids; D013230:Stearoyl-CoA Desaturase