Inter-organ communication in Drosophila: Lipoproteins, adipokines, and immune-metabolic coordination.

Inter-organ communication networks are essential for maintaining systemic homeostasis in multicellular organisms. In Drosophila melanogaster, studies of adipokines and lipoproteins reveal evolutionarily conserved mechanisms coordinating metabolism, immunity, and behavior. This mini-review focuses on two key pathways: the adipokine Unpaired 2 (Upd2) and lipoprotein-mediated signaling. Upd2, a leptin analog, mediates fat-brain communication to regulate insulin secretion, sleep, and feeding behavior. Recent work has uncovered an LC3/Atg8-dependent secretion mechanism for Upd2, linking nutrient sensing to systemic adaptation. Lipoproteins, particularly ApoLpp and LTP, function beyond lipid transport, orchestrating neural maintenance and immune responses. During infection, macrophage-derived signals trigger lipoprotein-mediated lipid redistribution to support host defense. Additionally, muscle tissue emerges as an unexpected mediator of immune-metabolic coordination through inter-organ signaling. These findings highlight the intricate cross-talk between organs required for organismal survival and suggest therapeutic strategies for metabolic disorders.