Aufklärung des Mechanismus des transendothelialen Fettsäuretransportes
Biochemie
Zusammenfassung der Projektergebnisse
A unique feature of microvascular endothelial cells is the efficient uptake and transport of fatty acids across the endothelium, with only scarce amounts used for their own metabolism. Transendothelial fatty acid transport is especially relevant for the energy metabolism of muscle cells, and for the storage of neutral lipids in adipose tissue. Fundamental questions regarding this process have remained unresolved, despite their enormous pathophysiological relevance for widespread metabolic diseases. Here, extracellular concentration of fatty acids, endothelial fatty acid metabolism and basolateral fatty acid trapping were analysed in a time resolved manner for their effect on the efficiency of transendothelial fatty acid transport. The model system were human umbilical vein endothelial cells (HUVECs) grown on Transwell filters incubated with radiolabeled oleic acid, followed by scintillation counting and quantitative thin layer chromatography. Extracellular availability of fatty acids correlated with the extent and speed of endothelial fatty acid uptake and transport. An initial burst of fatty acid incorporation within the first minute was followed by a steady phase where levels of intracellular non-esterified fatty acid remained high even as newly synthesized membrane and neutral lipids increased over time. The velocity of transendothelial fatty acid transport was high, as demonstrated by the efflux of the majority of radiolabeled non-esterified fatty acids within 30s in a pulse-chase approach. Calculations suggest that the rate of transport was more than twentyfold higher than the rate of endothelial metabolism. Accordingly, manipulation of endothelial fatty acid metabolism by either overexpression or depletion of CoA ligases elicited significant but modest changes of fatty acid uptake and transport. Efflux of fatty acids correlated with different concentrations of fatty acid free albumin in the basolateral chamber, mimicking variable parenchymal fatty acid consumption. Surprisingly, lipolysis of triacylglycerol contributed to the efflux of fatty acids. Inhibition of lipolysis by Atglistatin supported this novel and unexpected mechanism. Consistent with this, the basolateral medium contained only non-esterified fatty acids. In conclusion, the current data support a model where extracellular serum fatty acids are the main driver of transendothelial transport. Fatty acids derived by the lipolysis of transiently synthesized triglycerides contribute to endothelial fatty acid efflux.
Projektbezogene Publikationen (Auswahl)
-
Molecular mechanism of trans-endothelial fatty acid transport. Retreat of the Heidelberg Thematic Research Network Molecular Mechanisms in Health and Disease (MINDS), Niedernhausen, Germany (poster presentation)
Bergler F.
-
Endothelial fatty acid transport and metabolism. ASBMB Deuel Conference on Lipids, Dana Point, CA, USA (reviewed abstract, poster presentation)
Bergler, F. & J. Füllekrug
-
Impact of FATP4 upregulation and related parameters on trans-endothelial fatty acid transport. Dissertation
Bergler, F.
-
Lipolysis of triglycerides contributes to endothelial fatty acid efflux. 1st EMBO Workshop on Lipid Droplets, San Feliu de Guixols, Spain (reviewed abstract, poster presentation)
Bergler, F. & J. Füllekrug
