Metabolism of individual fatty acids during infusion of a triacylglycerol emulsion

The triacylglycerol emulsion Intralipid was infused into six normal subject s to investigate the metabolism of individual fatty acids in subcutaneous a dipose tissue and forearm muscle, by measurement of arteriovenous differenc es. The composition of plasma nonesterified fatty acids changed steadily af ter passage through adipose tissue and became similar to that of the emulsi on, reflecting hydrolysis of the Intralipid-triacylglycerol by lipoprotein lipase, since endogenous lipolysis (hormone-sensitive lipase activity plus lipoprotein lipase hydrolysis of very low density lipoprotein triacylglycer ol) was decreased. There was no significant net release of total or individ ual fatty acids from forearm muscle although there was a tendency for the c omposition of the fatty acids in forearm venous plasma to change during pas sage through the tissue to reflect the composition of the emulsion. This ma y reflect hydrolysis of emulsion particles by lipoprotein lipase situated i n capillaries which drain into the forearm vein. The behavior of stearic ac id in the plasma nonesterified fatty acid pool was consistently aberrant, w ith arterialized concentrations considerably higher than predicted from adi pose tissue release, both before and during Intralipid infusion. We conclud e that there are no significant differences in the metabolism of specific f atty acids, with the exception of stearic acid.