When presented with a nutrient rich environment, an organism utilizes those energy stores for growth as well as long-term storage. However, when nutrients are no longer available or the animal encounters a stressful situation such as an infection, an organism must be able to sense a change in its environment and redirect its energy utilization to accommodate the stressful conditions. My thesis research uses the genetically tractable organism, Drosophila melanogaster, to understand the genes and pathways responsible for growth and triglyceride storage in response to nutrient abundance as well as those directing the shift in ATP utilization away from energy-consuming processes in response to various stresses such as starvation and infection. I have focused on the evolutionarily conserved insulin signaling pathway due to its known role of regulating cell and organ growth as well as glucose and lipid metabolism in a number of organisms. I have found that activating insulin signaling in the fly\u27s main triglyceride storage organ, the fat body, promotes the energy-consuming process of storing nutrients by increasing both fat cell number and cellular fat content. Conversely, when activating inflammatory signaling in the fly genetically or by infection, I have found that insulin signaling activity is decreased resulting in blunted triglyceride storage and small flies. These data suggest that the insulin signaling pathway is a central regulator of growth and metabolism and altering the activity of this pathway can shift energy utilization away from energy-consuming processes during times of stress
