Time-of-Day Differences in the Plasma N -Glycome of Normal and Obese Mice and the Effects of Dapagliflozin Administered in the Morning or at Night

Circadian rhythms regulate a wide range of physiological functions, including metabolism and protein expression. While the influence of circadian timing on plasma glycosylation remains poorly understood, aberrant N-glycosylation is implicated in metabolic diseases. Here, we investigated diurnal variations in the plasma N-glycome of mice fed a high-fat diet (HFD), with or without treatment using the sodium-glucose cotransporter 2 (SGLT2) inhibitor dapagliflozin (Dap), administered either in the morning or at night. Using a quantitative glycomic platform based on glycoblotting and MALDI-TOF MS, we identified time-of-day-dependent changes in specific plasma N-glycans following HFD feeding. These alterations were more pronounced in plasma collected at night. Moreover, repeated administration of Dap induced glycan profile changes that differed depending on the dosing time. Interestingly, nighttime administration of Dap normalized several HFD-induced glycan alterations to levels closer to those of control mice, despite limited effects on blood glucose or body weight. These results suggest that N-glycan profiles may serve as sensitive and potentially early biomarkers of pharmacological effects in this experimental model and support the importance of time-of-day-dependent sampling when evaluating glycosylation-targeted interventions.