Metabolic Flux Analysis Uncovers Substrate-Specific Reprogramming and ATP Deficit in CORT-Induced Depressive-like Astrocytes

Depression is closely associated with brain energy metabolism; however, its metabolic characteristics and the mechanisms underlying energy dysregulation remain poorly understood. In this study, we employed an in vitro depression model using corticosterone (CORT)-induced astrocytes and applied stable isotope-resolved metabolomics (SIRM) to trace the metabolic fate of [U-¹³C₆]-glucose, [U-¹³C₃]-lactate, and [U-¹³C₅]-glutamine. Metabolic flux analysis (MFA) was subsequently used to quantify intracellular fluxes. CORT exposure triggered substrate-specific metabolic reprogramming: glucose and lactate catabolism were impaired, whereas glutamine utilization was upregulated. Despite increased glucose uptake and glycolytic flux, most glucose-derived carbon was shunted toward excessive lactate production rather than entering the tricarboxylic acid (TCA) cycle, resulting in a net lactate efflux. Concurrently, glutaminolysis was enhanced to partially compensate for reduced oxidative metabolism. These findings indicate that while glucose remains the dominant energy substrate, its preferential diversion to aerobic glycolysis markedly diminishes ATP production. Collectively, this work provides novel insights into astrocytic energy dysfunction in depression and highlights potential metabolic targets for therapeutic strategies aimed at restoring cerebral energy homeostasis.