Background Serum C-peptide concentrations reflect insulin secretion and beta cell function and can be used to diagnose and distinguish type-1 and type-2 diabetes. C-peptide is a more accurate indicator of insulin status than direct insulin measurement for monitoring patients with diabetes. However, the current methods available for C-peptide quantification exhibit poor reproducibility, are costly, and require highly trained laboratory personnel. Here, we have developed and evaluated a matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based assay to standardize C-peptide measurements, providing highly accurate and comparable results across testing systems and laboratories. Methods C-peptide from human serum was enriched using antibody-conjugated magnetic beads. The eluted isolates were further modified with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) to enhance the ionization of naturally acidic C-peptide. After desalting with ZipTips, the samples were subjected to MALDI-TOF MS analysis. Recombinant human C-peptide was used to develop the assay, and a heavy isotope labeled human C-peptide was used as an internal standard for quantification. Results The MALDI-TOF MS method was validated in accordance with the restrictions of the device, with a limit of quantitation of 25 pmol/L. A correlation between the MAL-DI-TOF MS assay and a reference method was conducted using patient samples. The resulting regression revealed good agreement. Conclusions A simple, high-throughput, cost effective and quantitative MALDI-TOF MS C-peptide assay has been successfully developed and validated in clinical serum samples.

中文翻译：

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基于 MALDI-TOF 质谱的糖尿病患者 C 肽定量

背景 血清 C 肽浓度反映胰岛素分泌和 β 细胞功能，可用于诊断和区分 1 型和 2 型糖尿病。C肽是比直接测量胰岛素更准确的胰岛素状态指标，用于监测糖尿病患者。然而，目前可用于 C 肽定量的方法重现性差，成本高，并且需要训练有素的实验室人员。在这里，我们开发并评估了一种基于基质辅助激光解吸电离飞行时间质谱 (MALDI-TOF MS) 的测定，以标准化 C 肽测量，提供跨测试系统和实验室的高度准确和可比较的结果。方法利用抗体偶联磁珠富集人血清C肽。洗脱的分离物用 6-氨基喹啉基-N-羟基琥珀酰亚胺氨基甲酸酯 (AQC) 进一步修饰，以增强天然酸性 C 肽的电离。使用 ZipTips 脱盐后，对样品进行 MALDI-TOF MS 分析。重组人 C 肽用于开发该测定，并使用重同位素标记的人 C 肽作为定量的内标。结果 MALDI-TOF MS方法根据设备限制进行验证，定量限为25 pmol/L。使用患者样本进行 MAL-DI-TOF MS 测定与参考方法之间的相关性。由此产生的回归显示出良好的一致性。结论 一种简单、高通量、