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.

昼夜节律（circadian rhythms）调控诸多生理功能，涵盖代谢与蛋白质表达。尽管目前学界对昼夜节律时机对血浆糖基化的影响仍知之甚少，但异常N-糖基化（N-glycosylation）已被证实与代谢疾病密切相关。本研究针对高脂饮食（high-fat diet, HFD）喂养的小鼠，探究其血浆N-糖组（N-glycome）的昼夜变化；实验设置对照组与给药组，给药组分别于清晨或夜间给予钠-葡萄糖协同转运蛋白2（sodium-glucose cotransporter 2, SGLT2）抑制剂达格列净（dapagliflozin, Dap）。本研究采用基于糖印迹（glycoblotting）与基质辅助激光解吸电离飞行时间质谱（matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, MALDI-TOF MS）的定量糖组学平台，发现在高脂饮食喂养后，小鼠血浆特定N-聚糖（N-glycan）呈现出随昼夜时段变化的特征，且此类变化在夜间采集的血浆样本中更为显著。此外，反复给予达格列净所引发的聚糖谱变化，会因给药时段的不同而存在差异。值得注意的是，尽管达格列净对血糖与体重的影响有限，但夜间给药可使高脂饮食诱导的多种聚糖异常恢复至接近对照组小鼠的水平。本研究结果表明，在该实验模型中，N-聚糖谱可作为药效检测的敏感且潜在的早期生物标志物；同时也证实，在评估靶向糖基化的干预手段时，依据昼夜时段进行样本采集具有重要意义。