Description:Diurnal oscillation in glucose metabolism is strictly regulated by various factors, including activity, sleep and diet. We used a isotopologue tracing method to characterize the diurnal oscillation in glucose metabolite isotopes in Drosophila sp. Specifically, the interaction of food intake and sleep/activity was investigated. Wild type flies were injected with uniformly labeled 13C glucose after 4h fasting or ad lib condition. Different isotopologues of glucose metabolites were measured using UPLC-MS/MS to assess their temporal pattern.