Liver fatty acid binding protein expression enhances branched-chain fatty acid metabolism.
Although liver fatty acid binding protein (L-FABP) is known to enhance uptake and esterification of straight-chain fatty acids such as palmitic acid and oleic acid, its effects on oxidation and further metabolism of branched-chain fatty acids such as phytanic acid are not completely understood. The present data demonstrate for the first time that expression of L-FABP enhanced initial rate and average maximal oxidation of [2,3-3H] phytanic acid 3.5- and 1.5-fold, respectively. This enhancement was not due to increased [2,3-3H] phytanic acid uptake, which was only slightly stimulated (20%) in L-FABP expressing cells after 30 min. Similarly, L-FABP also enhanced the average maximal oxidation of [9,10-3H] palmitic acid 2.2-fold after incubation for 30 min. However, the stimulation of L-FABP on palmitic acid oxidation nearly paralleled its 3.3-fold enhancement of uptake. To determine effects of metabolism on fatty acid uptake, a non-metabolizable fluorescent saturated fatty acid, BODIPY-C16, was examined by laser scanning confocal microscopy (LSCM). L-FABP expression enhanced uptake of BODIPY-C16 1.7-fold demonstrating that L-FABP enhanced saturated fatty acid uptake independent of metabolism. Finally, L-FABP expression did not significantly alter [2,3-3H] phytanic acid esterification, but increased [9,10-3H] palmitic acid esterification 4.5-fold, primarily into phospholipids (3.7-fold) and neutral lipids (9-fold). In summary, L-FABP expression enhanced branched-chain phytanic acid oxidation much more than either its uptake or esterification. These data demonstrate a potential role for L-FABP in the peroxisomal oxidation of branched-chain fatty acids in intact cells.
Atshaves
Barbara P
BP
Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466, USA.
Storey
Stephen M
SM
Huang
Huan
H
Schroeder
Friedhelm
F
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D050556:Fatty Acid-Binding Proteins; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D007739:L Cells; D008055:Lipids / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism*; D051379:Mice; D019308:Palmitic Acid / Q000378:metabolism*; D010831:Phytanic Acid / Q000378:metabolism*
D002352:Carrier Proteins; C493320:Fabp1 protein, mouse; D050556:Fatty Acid-Binding Proteins; D008055:Lipids; D010831:Phytanic Acid; D019308:Palmitic Acid