title: FAT/CD36-null mice reveal that mitochondrial FAT/CD36 is required to upregulate mitochondrial fatty acid oxidation in contracting muscle.
abstract: The plasma membrane fatty acid transport protein FAT/CD36 is also present at the mitochondria, where it may contribute to the regulation of fatty acid oxidation, although this has been challenged. Therefore, we have compared enzyme activities and rates of mitochondrial palmitate oxidation in muscles of wild-type (WT) and FAT/CD36 knockout (KO) mice, at rest and after muscle contraction. In WT and KO mice, carnitine palmitoyltransferase-I, citrate synthase, and beta-hydroxyacyl-CoA dehydrogenase activities did not differ in subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria of WT and FAT/CD36 KO mice. Basal palmitate oxidation rates were lower (P < 0.05) in KO mice (SS -18%; IMF -13%). Muscle contraction increased fatty acid oxidation (+18%) and mitochondrial FAT/CD36 protein (+16%) in WT IMF but not in WT SS, or in either mitochondrial subpopulation in KO mice. This revealed that the difference in IMF mitochondrial fatty acid oxidation between WT and KO mice can be increased approximately 2.5-fold from 13% under basal conditions to 35% during muscle contraction. The FAT/CD36 inhibitor sulfo-N-succinimidyl oleate (SSO), inhibited palmitate transport across the plasma membrane in WT, but not in KO mice. In contrast, SSO bound to mitochondrial membranes and reduced palmitate oxidation rates to a similar extent in both WT and KO mitochondria ( approximately 80%; P < 0.05). In addition, SSO reduced state III respiration with succinate as a substrate, without altering mitochondrial coupling (P/O ratios). Thus, while SSO inhibits FAT/CD36-mediated palmitate transport at the plasma membrane, SSO has undefined effects on mitochondria. Nevertheless, the KO animals reveal that FAT/CD36 contributes to the regulation of mitochondrial fatty acid oxidation, which is especially important for meeting the increased metabolic demands during muscle contraction.
authors.affiliation: 1Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada. ghollowa@uoguelph.ca
authors.forename: Graham P
authors.initials: GP
authors.lastname: Holloway
authors.forename: Swati S
authors.initials: SS
authors.lastname: Jain
authors.forename: Veronic
authors.initials: V
authors.lastname: Bezaire
authors.forename: Xiao Xia
authors.initials: XX
authors.lastname: Han
authors.forename: Jan F C
authors.initials: JF
authors.lastname: Glatz
authors.forename: Joost J F P
authors.initials: JJ
authors.lastname: Luiken
authors.forename: Mary-Ellen
authors.initials: ME
authors.lastname: Harper
authors.forename: Arend
authors.initials: A
authors.lastname: Bonen
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D018955:CD36 Antigens / Q000172:deficiency* / Q000235:genetics; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005260:Female; D051379:Mice; D018345:Mice, Knockout; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009829:Oleic Acids / Q000494:pharmacology; D010084:Oxidation-Reduction; D019308:Palmitic Acid / Q000378:metabolism*; D019802:Succinic Acid / Q000378:metabolism; D013388:Succinimides / Q000494:pharmacology
chemical_list: D018955:CD36 Antigens; D009829:Oleic Acids; D013388:Succinimides; C120556:sulfo-N-succinimidyl oleate; D019308:Palmitic Acid; D019802:Succinic Acid; D015094:3-Hydroxyacyl CoA Dehydrogenases; D002334:Carnitine O-Palmitoyltransferase; D002950:Citrate (si)-Synthase