title: Saturated fatty acid in the phospholipid monolayer contributes to the formation of large lipid droplets.
abstract: The degree of saturation of fatty acid chains in the bilayer membrane structure is known to control membrane fluidity and packing density. However, the significance of fatty acid composition in the monolayers of lipid droplets (LDs) has not been elucidated. In this study, we noted a relationship between the size of LDs and the fatty acid composition of the monolayer. To obtain large LDs, we generated NIH3T3 cells overexpressing fat-specific protein 27 (FSP27). This induced the fusion of LDs, resulting in larger LDs in FSP27-overexpressing cells compared with LDs in control cells. Moreover, the lipid extracts of LDs from FSP27-overexpressing cells reconstituted large-droplet emulsions in vitro, implying that the lipid properties of LDs might affect the size of LDs. FSP27-overexpressing cells had more saturated fatty acids in the phospholipid monolayer of the LDs compared with control cells. To further investigate the effects of the degree of phospholipid unsaturation on the size of LDs, we synthesized artificial emulsions of a lipid mixed with distearoylphosphatidylcholine (DSPC, diC18:0-PC) and with dioleoylphosphatidylcholine (DOPC, diC18:1n-9-PC) and compared the sizes of the resulting LDs. The emulsions prepared from saturated PC had larger droplets than those prepared from unsaturated PC. Our results suggest that saturated fatty acid chains in phospholipid monolayers might establish the form and/or stability of large LDs.
authors.affiliation: Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan.
authors.forename: Kotoko
authors.initials: K
authors.lastname: Arisawa
authors.affiliation: Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan.
authors.forename: Haruka
authors.initials: H
authors.lastname: Mitsudome
authors.affiliation: Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan.
authors.forename: Konomi
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan.
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sugimoto
authors.affiliation: Institute for Human Life Innovation, Ochanomizu University, Tokyo 112-8610, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Institute for Human Life Innovation, Ochanomizu University, Tokyo 112-8610, Japan; Natural Science Division, Faculty of Core Research, Ochanomizu University, Tokyo 112-8610, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Fujiwara
authors.affiliation: Institute for Human Life Innovation, Ochanomizu University, Tokyo 112-8610, Japan; Natural Science Division, Faculty of Core Research, Ochanomizu University, Tokyo 112-8610, Japan. Electronic address: ichi.ikuyo@ocha.ac.jp.
authors.forename: Ikuyo
authors.initials: I
authors.lastname: Ichi
mesh_terms: D000818:Animals; D004655:Emulsions / Q000737:chemistry / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry* / Q000378:metabolism; D066292:Lipid Droplets / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism; D053835:Unilamellar Liposomes / Q000737:chemistry* / Q000378:metabolism
chemical_list: D004655:Emulsions; D005227:Fatty Acids; D008563:Membrane Lipids; D010743:Phospholipids; D053835:Unilamellar Liposomes
keywords: Fatty acid; Lipid droplet; Phospholipid monolayer