However, in the absence of a “liver,” that function may be subserved by cell systems. For example, cytochrome p450 expression is detected in several larval tissues. These include the fat body, but also critically, the malpighian tubules and mid gut.6, 7 The roles of these topographically distinct cytochromes have been the subject of significant research, because they are major determinants
of resistance to insecticides. Interestingly, when the relative roles of cytochromes within individual drosophila tissues have been analyzed, those in the Napabucasin order malpighian tubules (rather than in the gut and gut-related tissue) seem to be the most important to determining survival when the organism is challenged with DDT (dichlorodiphenyltrichloroethane).6 Selleckchem Forskolin With the identification of a further cell cluster, the oenocytes, which appear to be critical to fat metabolism and other metabolic pathways,
the picture of the Drosophila hepatocyte ortholog has become even more complex. Although the fat body acts as a major lipid store, the Gould group has recently demonstrated that the oenocyte accumulates lipids during starvation.8 Moreover, there appears to be bidirectional regulation of lipid metabolism in which the oenocytes are required for depleting stored lipid from the fat body during fasting. Additionally, the oenocytes express lipid-metabolizing proteins including Cyp4g1 and appear to share some of the lipid processing functions of the mammalian liver.8 As more is learned about the interplay between the broader functional repertoire of the oenocytes and the oenocyte–fat body interplay, the Drosophila system may well prove to be a model that can be deployed to study
aspects of fat metabolism and hepatic function that is orthologous to higher mammals. Indeed, the topographic separation of tissues delivering specific hepatic functions 上海皓元 within Drosophila means it may prove a valuable and unique model to study specific metabolic phenotypes. The evolution of the fruit fly provides a curious insight into the manner in which co-evolution of processes vital to life that have been grouped within a single, though multilineage, cellular system in the mammal, are topographically distributed across organ and tissue systems in the fly. So much for normal evolution and development, but what of the evolution of the response to disease? Here, intellectually simulating though the subject is, we can only conjecture. Unfortunately, we do not have the luxury of being able to conduct a controlled trial running for thousands, if not millions, of years.