Overexpression of membrane-associated fatty acid binding protein (FABPpm) in vivo increases fatty acid sarcolemmal transport and metabolism.
Fatty acid translocase (FAT/CD36) is a key fatty acid transporter in skeletal muscle. However, the effects on fatty acid transport by another putative fatty acid transporter, plasma membrane-associated fatty acid binding protein (FABPpm), have not been determined in mammalian tissue. We examined the functional effects of overexpressing FABPpm on the rates of 1) palmitate transport across the sarcolemma and 2) palmitate metabolism in skeletal muscle. One muscle (soleus) was transfected with pTracer containing FABPpm cDNA. The contralateral muscle served as control. After injecting the FABPpm cDNA, muscles were electroporated. FABPpm overexpression was directly related to the quantity of DNA administered. Electrotransfection (200 microg/muscle) rapidly induced FABPpm protein overexpression (day 1, +92%, P < 0.05), which was further increased during the next few days (days 3-7; range +142% to +160%, P < 0.05). Sarcolemmal FABPpm was comparably increased (day 7, +173%, P < 0.05). Neither FAT/CD36 expression nor sarcolemmal FAT/CD36 content was altered. FABPpm overexpression increased the rates of palmitate transport (+79%, P < 0.05). Rates of palmitate incorporation into phospholipids were also increased +36%, as were the rates of palmitate oxidation (+20%). Rates of palmitate incorporation into triacylglycerol depots were not altered. These studies demonstrate that in mammalian tissue FABPpm overexpression increased the rates of palmitate transport across the sarcolemma, an effect that is independent of any changes in FAT/CD36. However, since the overexpression of plasmalemmal FABPpm (+173%) exceeded the effects on the rates of palmitate transport and metabolism, it appears that the overexpression of FABPpm alone is not sufficient to induce completely parallel increments in palmitate transport and metabolism. This suggests that other mechanisms are required to realize the full potential offered by FABPpm overexpression.
Clarke
David C
DC
Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Miskovic
Dragana
D
Han
Xiao-Xia
XX
Calles-Escandon
Jorge
J
Glatz
Jan F C
JF
Luiken
Joost J F P
JJ
Heikkila
John J
JJ
Bonen
Arend
A
D000818:Animals; D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D018274:Electroporation / Q000379:methods; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019308:Palmitic Acid / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D012508:Sarcolemma / Q000737:chemistry / Q000378:metabolism
D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D019308:Palmitic Acid