Suppression of lipid transfer inhibitor protein activity by oleate. A novel mechanism of cholesteryl ester transfer protein regulation by plasma free fatty acids.
Arterioscler Thromb Vasc Biol
; 17(11): 3041-8, 1997 Nov.
Article
en En
| MEDLINE
| ID: mdl-9409291
ABSTRACT
Cholesteryl ester transfer protein (CETP) mediates the interlipoprotein exchange of cholesteryl ester (CE) and triglyceride. A second plasma protein, lipid transfer inhibitor protein (LTIP), binds to lipoproteins and inhibits CETP activity by displacing CETP from the lipoprotein surface. Since free fatty acids (FFAs) enhance the binding of CETP to lipoproteins, we have examined the possible role of FFAs in modulating LTIP activity. Partially purified CETP, LTIP, and lipoproteins were incubated with 0 to 30 mumol/L sodium oleate, and the transfer of CE between a labeled donor lipoprotein and a given acceptor lipoprotein was measured. Without LTIP, oleate stimulated CETP-mediated CE transfer between VLDL, LDL, and HDL up to threefold. This stimulation was unique in both magnitude and oleate concentration dependence for each donor-acceptor lipoprotein pair. In contrast to CETP activity, in transfer reactions involving LDL or VLDL as donor, LTIP activity was suppressed (> 80%) by 10 to 15 mumol/L oleate. LTIP activity in transfer reactions with HDL as donor was less sensitive. Similar results to these were observed when lipid transfer reactions were measured in the total lipoprotein fraction isolated from FFA-enriched plasma. The FFA content of lipoproteins was strongly influenced by the concentration of FFA in plasma; lipoprotein FFA levels sufficient to suppress LTIP activity by 50% to 100% were achieved in plasma containing 0.8 to 1.0 mmol/L FFA. We conclude that LTIP may be functionally inactive during periods of transient elevations of plasma FFA levels, such as during postprandial lipemia or overnight fasting, or chronically suppressed in disease states in which plasma FFA levels are increased. The suppression of LTIP activity by FFA allows for maximum CETP-mediated lipid transfer between all lipoproteins, including lipid transfer reactions involving LDL that are normally preferentially suppressed by LTIP.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas Sanguíneas
/
Glicoproteínas
/
Proteínas Portadoras
/
Ácido Oléico
/
Ácidos Grasos no Esterificados
/
Lipoproteínas
Límite:
Humans
Idioma:
En
Revista:
Arterioscler Thromb Vasc Biol
Asunto de la revista:
ANGIOLOGIA
Año:
1997
Tipo del documento:
Article
País de afiliación:
Estados Unidos