title: Free fatty acids modulate intermembrane trafficking of cholesterol by increasing lipid mobilities: novel 13C NMR analyses of free cholesterol partitioning.
abstract: Cholesterol and free fatty acids in membranes modulate major biological processes, and their cellular metabolism and actions are often coordinately regulated. However, effects of free fatty acid on cholesterol-membrane interactions have proven difficult to monitor in real time in intact systems. We developed a novel (13)C NMR method to assess effects of free fatty acids on molecular interactions of cholesterol within--and transfer between--model membranes. An important advantage of this method is the ability to acquire kinetic data without separation of donor and acceptor membranes. Large unilamellar phospholipid vesicles (LUV) with phosphatidylcholine/cholesterol ratios of 4:1 served as cholesterol donors. Small unilamellar vesicles (SUV) made with phosphatidylcholine were acceptors. The (13)C(4)-cholesterol peak is narrow in SUV, but very broad in LUV, spectra; the increase in intensity of this peak over time monitored transfer. Oleic acid and other long chain free fatty acids [saturated (C12-18) and unsaturated (C18)] dose-dependently increased mobilities of lipids in LUV (phospholipid and cholesterol) and cholesterol transfer rates, whereas short (C8-10) and very long (C24) chain free fatty acids did not. Decreasing pH from 7.4 to 6.5 (+/-oleic acid) had no effect on cholesterol transfer, and 5 mol % fatty acyl-CoAs increased transfer rates, demonstrating greater importance of the fatty-acyl tail over the headgroup. In LUV containing sphingomyelin, transfer rates decreased, but the presence of oleic acid increased transfer 1.3-fold. These results demonstrate free fatty acid-facilitated cholesterol movement within and between membranes, which may contribute to their multiple biological effects.
authors.affiliation: Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, 630 West 168th Street PH 1512, New York, New York 10032, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Johnson
authors.forename: James A
authors.initials: JA
authors.lastname: Hamilton
authors.forename: Tilla S
authors.initials: TS
authors.lastname: Worgall
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Deckelbaum
mesh_terms: D001692:Biological Transport; D002247:Carbon Isotopes; D002784:Cholesterol / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000737:chemistry*; D007700:Kinetics; D008027:Light; D008051:Lipid Bilayers / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D019301:Oleic Acid / Q000737:chemistry; D010713:Phosphatidylcholines / Q000032:analysis / Q000737:chemistry; D012542:Scattering, Radiation; D013109:Sphingomyelins / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D005230:Fatty Acids, Nonesterified; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D019301:Oleic Acid; D002784:Cholesterol