Human Forearm Muscle Metabolism during Exercise II Uptake, release and oxidation of individual FFA and glycerol

The uptake, release, and oxidation of individual free fatty acids (FFA) in the human forearm were studied during a 60-min exercise period. Muscular uptake of FFA rose with the arterial concentration. The muscle showed a slight preference for linoleic and oleic acid compared to palmitic acid. The forearm RQ indicated a constant fat oxidation during the period of exercise. The uptake of FFA covered about 50 per cent of the fat oxidation. On the average 60 per cent of the muscular FFA-14C uptake was oxidized to 14CO2. The remaining radioactivity left the muscle as water-soluble metabolite(s). β-Hydroxybutyrate leaving the muscle was shown to be labeled. No release of glycerol accompanied the release of FFA during exercise. Glycerol-1-14C was oxidized by the exercising muscle. Glycerol dehydrogenase activity was demonstrated in human skeletal muscle.