Endothelial lipase provides an alternative pathway for FFA uptake in lipoprotein lipase-deficient mouse adipose tissue.
Lipoprotein lipase (LPL) is thought to be the only enzyme responsible for the catabolism of triglycerides (TGs) associated with TG-rich lipoproteins in adipose tissue (AT). However, LPL deficiency in humans and induced mutant mice is not associated with decreased fat mass. We investigated whether endothelial lipase (EL), a recently discovered phospholipase, might represent an alternative mechanism for the uptake of phospholipid-derived fatty acids in murine lipoprotein-deficient AT. When LPL was expressed in AT and isolated murine adipocytes, EL mRNA was not detectable. In contrast, mouse AT and isolated adipocytes that lacked LPL expressed large amounts of EL mRNA. The cellular phospholipase activity in LPL-deficient fat pads was increased 4-fold compared with control fat pads and could be inhibited to control levels by a specific EL antibody. Fatty acids produced by EL activity were absorbed by adipocytes and incorporated into the TG moiety of AT. Our results suggest that EL activity in AT and other peripheral tissues might contribute to the tissue uptake of free fatty acids, which could have important implications for the metabolism of plasma lipoproteins.
Kratky
Dagmar
D
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Zimmermann
Robert
R
Wagner
Elke M
EM
Strauss
Juliane G
JG
Jin
Weijun
W
Kostner
Gerhard M
GM
Haemmerle
Guenter
G
Rader
Daniel J
DJ
Zechner
Rudolf
R
D041721:3T3-L1 Cells; D000273:Adipose Tissue / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation; D005230:Fatty Acids, Nonesterified / Q000737:chemistry / Q000378:metabolism*; D008049:Lipase / Q000235:genetics / Q000378:metabolism*; D008071:Lipoprotein Lipase / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000097:blood; D008099:Liver / Q000201:enzymology; D051379:Mice; D010740:Phospholipases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014280:Triglycerides / Q000097:blood
D005230:Fatty Acids, Nonesterified; C034396:HDL-triglyceride; D008075:Lipoproteins, HDL; D012333:RNA, Messenger; D014280:Triglycerides; D010740:Phospholipases; D008049:Lipase; C498741:Lipg protein, mouse; D008071:Lipoprotein Lipase