Free fatty acids as a source of energy for trehalose synthesis in the fat body of the American cockroach ( Periplaneta americana)

Abstract

Both trehalose synthesis and O 2 consumption by the fat body of Periplaneta americana were increased 120 and 70% respectively by corpus cardiacum (CC) extract. Stimulation of these processes by CC extract was accompanied by a decrease in the oxidation of [6- 14C]glucose (22%) and an increase in that of [1- 14C]oleic acid (106%). No measurable effect of CC extract on endogenous levels of free fatty acids or tri-, di-, or monoaclyglyercols in the fat body was found. The oxidation inhibitor pent-4-enoic acid (PEA) inhibited trehalose production by the fat body in vitro by 32%. Trehalose synthesis was stimulated 113% by CC extract but only by 58% in the presence of 1 mM PEA. Oxidation of [1- 14C]oleic acid, both in unstimulated and CC-stimulated fat body was also inhibited by PEA. Furthermore, PEA caused the rate of glycolytic flux, as measured by the oxidation of [6- 14C]glucose, to decrease concomitantly with the decrease in trehalose synthesis. The calculated yield of ATP from the estimated value for fatty acid oxidation equalled that available from the O 2 consumed. ATP production (derived from O 2 consumption) however, was 3-fold greater than that required to account for the synthesis of trehalose. The data suggest that CC extract stimulates energy dependent reactions additional to that of trehalose synthesis. These studies support the proposal that fatty acids are an important source of energy for CC-stimulated trehalose synthesis.