title: Stimulation of lipolysis enhances the rate of cholesterol efflux to HDL in adipocytes.
abstract: Adipose tissue constitutes a major location for cholesterol storage and, as such, it may play a role in the regulation of circulating cholesterol levels. A possible metabolic link between the lipolytic activity of adipocytes and their ability to release cholesterol to reconstituted human high density lipoprotein, HDL, was investigated in 3T3-L1 adipocytes. In the presence of HDL, composed of human apoA-I and phosphatidylcholine, adipocytes release cholesterol in a lipoprotein-dose and time dependent fashion. beta-adrenergic activation of the lipolysis promotes a 22% increase in the extent of cholesterol efflux to reconstituted discoidal HDL particles. Activation of lipolysis promotes a rapid decrease in the cholesterol content of the plasma membrane and a concomitant increase in lipid droplet cholesterol. This change is independent of the presence of HDL. Activation of the lipolysis does not affect the levels of ABCA1 and SR-BI. Therefore, the enhancement of cholesterol efflux is not due to the level of plasma membrane cholesterol, or to the levels of the cholesterol transporters ABCA1 and scavenger receptor SR-BI. Brefeldin A did not affect the rate of cholesterol efflux under basal lipolytic conditions, but it abolished the lipolysis-dependent enhancement of cholesterol efflux to HDL. This study suggests that activation of lipolysis is accompanied by an increase in BFA-sensitive vesicular transport that in turn enhances cholesterol efflux to HDL. The study supports a metabolic link between the lipolytic activity of adipocytes and the rate of cellular cholesterol efflux to HDL.
authors: Department of Biochemistry and Molecular Biology, Oklahoma State University, 147 Noble Research Center, Stillwater, OK 74078, USA.
authors: Philip B
authors: PB
authors: Verghese
authors: Estela L
authors: EL
authors: Arrese
authors: Jose L
authors: JL
authors: Soulages
mesh_terms: D041721:3T3-L1 Cells; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D006801:Humans; D008066:Lipolysis / Q000187:drug effects; D008075:Lipoproteins, HDL / Q000378:metabolism*; D051379:Mice; D051122:Scavenger Receptors, Class B / Q000378:metabolism
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D008075:Lipoproteins, HDL; D051122:Scavenger Receptors, Class B; D020126:Brefeldin A; D002784:Cholesterol