Metabolic command centers in Drosophila: how the fat body and oenocytes orchestrate immunity, reproduction, and aging.

Energy storage and mobilization are fundamental to physiology and survival, yet their dysregulation drives obesity, diabetes, cancer, and age-related diseases. Drosophila melanogaster offers a tractable model for dissecting these pathways because its metabolic and endocrine circuits mirror those of vertebrates. In flies, the fat body functions like mammalian adipose and liver tissues, as it stores triacylglycerol and glycogen, produces lipoproteins, and serves as a major immune site. In addition, hepatocyte-like oenocytes direct lipid mobilization and trafficking during nutrient stress, synthesize cuticular hydrocarbons, and help regulate fertility and behavior. This review surveys discoveries enabled by single-cell genomics, metabolomics, and advanced genetics, with a focus on how the fat body and oenocytes integrate metabolism with reproduction, immunity, and aging.