Insulin regulates systemic lipid traffic in starving animals

In periods of malnutrition starving organisms initiate the reorganization and degradation of cellular lipids. Yet, the build-up of lipid stores is reported in animals entering early starvation stages. Anabolic lipid metabolism is regulated by many circuits including the insulin/insulin- like growth factor signaling (IIS) cascade. The regulative role of IIS ligands in food deprived animals is often neglected, since supporting evidence for this notion is largely missing. Here we show that in starving adult Drosophila melanogaster IIS is required to stabilize the transport of circulating lipids and sugars, and is essential for the initial increase of lipid stores in fat body cells. Further, we demonstrate that the Drosophila insulin-like peptides (dIlp) 2 and 5 regulate the cellular IIS cascade differentially. To its end we speculate that each hormone initiates complementary measures that increase the starvation resistance of adult flies.