The role of free fatty acids in the regulation of lipolysis by human adipose tissue cells

The effect of added fatty acid on lipolysis and cyclic AMP concentration of human adipose tissue cells was studied. The addition of sodium oleate decreased the lipolytic response of adipocytes to 10−7 M isoproterenol. Inhibition was detectable with the lowest quantity of oleate added, 0.2 mM, and was progressively greater with increasing quantities of added fatty acid. Palmitic and linoleic acids were as effective as oleic acid in suppressing isoproterenol-stimulated lipolysis. Suppression of cyclic AMP formation was detectable within one minute after the addition of oleate. Cyclic AMP formation, suppressed by accumulated fatty acids, could not be stimulated by the addition of fresh isoproterenol. However, after the accumulated fatty acids were removed by buffer change, cyclic AMP formation was stimulated by fresh isoproterenol. These findings are consistent with the view that fatty acids are physiologically significant regulators of lipolysis.