Time-restricted feeding provides limited microglial immunometabolic improvements in diet-induced obese rats

Time-restricted eating has shown great promise for improving metabolic health in humans with obesity, but its mechanism is still not completely resolved. In this study, we investigated how time-restricted feeding (TRF) affects microglial immunometabolism using Wistar rats. High-fat diet (HFD)-fed animals became obese, but restricting food intake to the active phase reduced fat mass, reinforced the rhythmicity of the microglial transcriptome, and prevented an increase of hypothalamic microglial cell numbers. However, TRF failed to reverse HFD-induced microglial immune dysfunction and metabolic disturbances, including suppressed electron transport chain activity, increased lipid metabolism gene expression, and impaired metabolic flexibility. These findings suggest that obesity-driven microglial immunometabolic reprogramming persists despite TRF-induced weight loss and may contribute to obesogenic memory and weight regain after weight loss induced by dietary interventions. RNA-seq profiling was performed on isolated microglia from adult male Wistar rats to investigate the impact of diet and feeding schedule on circadian transcriptional dynamics. Animals were maintained on either standard chow or a high-fat diet (HFD) and were subjected to one of three feeding regimens: ad libitum, dark-phase feeding, or light-phase feeding. Microglia were collected at six Zeitgeber times (ZT02, ZT06, ZT10, ZT14, ZT18, and ZT22), resulting in 6 experimental groups × 6 circadian time points. This design enables the comparison of microglial transcriptional responses to diet, feeding schedule, and circadian phase.