Mitochondrial long chain fatty acid oxidation, fatty acid translocase/CD36 content and carnitine palmitoyltransferase I activity in human skeletal muscle during aerobic exercise

Abstract

Mitochondrial fatty acid transport is a rate-limiting step in long chain fatty acid (LCFA) oxidation. In rat skeletal muscle, the transport of LCFA at the level of mitochondria is regulated by carnitine palmitoyltransferase I (CPTI) activity and the content of malonyl-CoA (M-CoA); however, this relationship is not consistently observed in humans. Recently, fatty acid translocase (FAT)/CD36 was identified on mitochondria isolated from rat and human skeletal muscle and found to be involved in LCFA oxidation. The present study investigated the effects of exercise (120 min of cycling at ∼60%V O 2 peak ) on CPTI palmitoyl-CoA and M-CoA kinetics, and on the presence and functional significance of FAT/CD36 on skeletal muscle mitochondria. Whole body fat oxidation rates progressively increased during exercise (P < 0.05), and concomitantly M-CoA inhibition of CPTI was progressively attenuated. Compared to rest, 120 min of cycling reduced (P < 0.05) the inhibition of 0.7, 2, 5 and 10 μM M-CoA by 16%, 21%, 30% and 34%, respectively. Whole body fat oxidation and palmitate oxidation rates in isolated mitochondria progressively increased (P < 0.05) during exercise, and were positively correlated (r = 0.78). Mitochondrial FAT/CD36 protein increased by 63% (P < 0.05) during exercise and was significantly (P < 0.05) correlated with mitochondrial palmitate oxidation rates at all time points (r = 0.41). However, the strongest (P < 0.05) correlation was observed following 120 min of cycling (r = 0.63). Importantly, the addition of sulfo-N -succimidyloleate, a specific inhibitor of FAT/CD36, reduced mitochondrial palmitate oxidation to ∼20%, indicating FAT/CD36 is functionally significant with respect to LCFA oxidation. We hypothesize that exercise-induced increases in fatty acid oxidation occur as a result of an increased ability to transport LCFA into mitochondria. We further suggest that decreased CPTI M-CoA sensitivity and increased mitochondrial FAT/CD36 protein are both important for increasing whole body fatty acid oxidation during prolonged exercise.

Selective transport of long-chain fatty acids by FAT/CD36 in skeletal muscle of broilers

“…As we know, FAT/CD36 also plays an important role in mitochondrial oxidation, which involves CPT I as a key enzyme (Holloway et al, 2006;Holloway et al, 2008). When LA was added to the diet, the mRNA expression of CPT I increased significantly in red muscles, and its half-life was prolonged by 50% (Morash et al, 2009).…”

Fatty acid oxidation in cardiac and skeletal muscle mitochondria is unaffected by deletion of CD36

“…Recent reports noted that the plasma membrane fatty acid translocase CD36 is found in mitochondrial membranes, however the function of CD36 in mitochondria is unclear. Studies using a putative inhibitor of CD36, sulfo-N-succinimidyl oleate (SSO), observed decreased LCFA oxidation in skeletal muscle mitochondria, suggesting that CD36 is involved in LCFA transport into the mitochondrial matrix [4][5][6]. Although an attractive thesis, earlier studies showed SSO inhibits CPT-I activity [4], thus effects of SSO on fatty acid oxidation may not be specific for CD36.…”

Modest PGC-1α Overexpression in Muscle in Vivo Is Sufficient to Increase Insulin Sensitivity and Palmitate Oxidation in Subsarcolemmal, Not Intermyofibrillar, Mitochondria

“…CPTI activities were measured in isolated SS and IMF mitochondria with the method of McGarry et al (36), using 75 M of palmitoyl-CoA, which approximates the concentration at which the K m of CPTI activity is observed (37).…”

“…Palmitate Oxidation by Isolated Mitochondria-Oxidation of palmitate was measured in isolated mitochondria as we have described previously (24,37), using a modified Krebs-Ringer buffer (MKR: 115 mM NaCl, 2.6 mM KCl, 1.2 mM KH 2 PO 4 , 10 mM NaHCO 3 , 10 mM HEPES, pH 7.4) that was gassed for 15 min (with 5% CO 2 , 95% O 2 ) and then supplemented with 5.0 mM ATP, 1.0 mM NAD ϩ , 0.5 mM DL-carnitine, 0.1 mM coenzyme A, 25 M cytochrome c, and 0.5 mM malate. Palmitate (75 M, [1-14 C]palmitate (0.5 Ci)), complexed to BSA (6:1 (24, 40)) was used in all experiments.…”