Increase in membrane uptake of long-chain fatty acids early during preadipocyte differentiation.
An increase in early rates of oleate uptake, which reflected fatty acid (FA) entry into the cells, was apparent 2-3 days after confluence of differentiating BFC-1 preadipocytes. The increase was measured in cells kept without glucose and with arsenate, where greater than 95% of intracellular radioactivity was recovered as free unesterified oleate. Uptake of retinoic acid, a molecule structurally similar to long-chain FA, remained unaltered during cell differentiation. Increase in oleate transport was related to increase in transport Vmax (determined under arsenate treatment) from 0.2 to 2 nmol/min per 10(6) cells, whereas Km remained unchanged (2 x 10(-7) M). Oleate transport was maximal at about day 6 after cell confluence (day 0), as FA metabolism (incorporation into lipids) began to gradually increase. The increase in transport preceded induction of mRNAs for both cytosolic FA-binding protein, which appeared at day 6, and for the FA synthase, which appeared at day 10. Data indicated that increases in activities of FA transport and of lipoprotein lipase, early during cell differentiation, favored increased availability of exogenous FA at a stage when endogenous FA synthesis is limited. This result would promote FA esterification and lipid deposition by supplying a rate-limiting substrate. Furthermore, oleate addition to BFC-1 preadipocytes at confluence potentiated the effect of dexamethasone in inducing mRNA for cytosolic FA-binding protein. In adipocytes, FA from exogenous or endogenous sources was necessary to maintain levels of cytosolic FA-binding protein mRNA. Thus, the increase in FA availability might contribute to, or modulate, induction of proteins necessary for preadipocyte differentiation.
Abumrad
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NA
Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232.
Forest
C C
CC
Regen
D M
DM
Sanders
S
S
D002001:Adipose Tissue, Brown / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001149:Arsenates / Q000494:pharmacology; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D064429:Fatty Acid Synthases / Q000235:genetics; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005947:Glucose / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D001149:Arsenates; D002352:Carrier Proteins; C082667:Fabp5 protein, mouse; C086936:Fabp7 protein, mouse; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009829:Oleic Acids; D012333:RNA, Messenger; D019301:Oleic Acid; D064429:Fatty Acid Synthases; D005947:Glucose