title: Dynamic regulation of hepatic lipid droplet properties by diet.
abstract: Cytoplasmic lipid droplets (CLD) are organelle-like structures that function in neutral lipid storage, transport and metabolism through the actions of specific surface-associated proteins. Although diet and metabolism influence hepatic CLD levels, how they affect CLD protein composition is largely unknown. We used non-biased, shotgun, proteomics in combination with metabolic analysis, quantitative immunoblotting, electron microscopy and confocal imaging to define the effects of low- and high-fat diets on CLD properties in fasted-refed mice. We found that the hepatic CLD proteome is distinct from that of CLD from other mammalian tissues, containing enzymes from multiple metabolic pathways. The hepatic CLD proteome is also differentially affected by dietary fat content and hepatic metabolic status. High fat feeding markedly increased the CLD surface density of perilipin-2, a critical regulator of hepatic neutral lipid storage, whereas it reduced CLD levels of betaine-homocysteine S-methyltransferase, an enzyme regulator of homocysteine levels linked to fatty liver disease and hepatocellular carcinoma. Collectively our data demonstrate that the hepatic CLD proteome is enriched in metabolic enzymes, and that it is qualitatively and quantitatively regulated by diet and metabolism. These findings implicate CLD in the regulation of hepatic metabolic processes, and suggest that their properties undergo reorganization in response to hepatic metabolic demands.
authors.affiliation: Graduate Program of Molecular Biology, University of Colorado School of Medicine, Aurora, Colorado, United States of America.
authors.forename: Amanda E
authors.initials: AE
authors.lastname: Crunk
authors.forename: Jenifer
authors.initials: J
authors.lastname: Monks
authors.forename: Aya
authors.initials: A
authors.lastname: Murakami
authors.forename: Matthew
authors.initials: M
authors.lastname: Jackman
authors.forename: Paul S
authors.initials: PS
authors.lastname: Maclean
authors.forename: Mark
authors.initials: M
authors.lastname: Ladinsky
authors.forename: Elise S
authors.initials: ES
authors.lastname: Bales
authors.forename: Shannon
authors.initials: S
authors.lastname: Cain
authors.forename: David J
authors.initials: DJ
authors.lastname: Orlicky
authors.forename: James L
authors.initials: JL
authors.lastname: McManaman
mesh_terms: D000818:Animals; D001622:Betaine / Q000378:metabolism; D018752:Diet, Fat-Restricted / Q000379:methods; D059305:Diet, High-Fat; D004041:Dietary Fats / Q000008:administration & dosage; D004721:Endoplasmic Reticulum / Q000378:metabolism; D050904:Homocysteine S-Methyltransferase / Q000378:metabolism; D050356:Lipid Metabolism / Q000502:physiology*; D008099:Liver / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D051379:Mice; D008810:Mice, Inbred C57BL; D000070780:Perilipin-2; D011506:Proteins / Q000378:metabolism; D020543:Proteome / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D008565:Membrane Proteins; D000070780:Perilipin-2; D011506:Proteins; D020543:Proteome; D001622:Betaine; D050904:Homocysteine S-Methyltransferase