The biological variation of serum ACE and CPN/CPB2 activity in healthy individuals as measured by the degradation of the neuro-peptide bradykinin – A reference dataset

Bradykinin (BK) is an inflammatory mediator. Its degradation in biofluids reports on the activity of enzymes like angioten-sin-converting enzyme (ACE) and basic carboxypeptidases N and CBP2 for which the neuropeptide is a substrate. Clinical studies have shown significant changes in the serum activity of these enzymes in patients with inflammatory diseases. Here, we investigated the natural variation of the cleavage of dabsylated BK in serum and the formation of two of its major fragments in a large cohort of 340 healthy volunteers from the international human Personal Omics Profiling (hPOP) consor-tium based at Stanford University. A batch effect was noted among sampling sites. In individual sample sets, it could be shown that the serum measured protease activity was statistically significantly higher in males than in females. Moreover, outliers were detected, which indicated a correlation of the experimental values and untreated diabetes and extensive exer-cising. There was no significant correlation with age, ethnicity, body mass index or overnight fasting. The investigation pro-vides reference values from the healthy population for the neuropeptide reporter assay. Importantly, the experiments were sensitive to sample quality and collection procedures – the results reiterate the importance of a high level of standardisation in preanalytical sample collection and processing.

缓激肽(BK)是一种炎症介质。其在生物流体中的降解水平，可反映血管紧张素转换酶(ACE)、碱性羧肽酶N及CBP2等酶的活性——该神经肽为上述酶的天然底物。临床研究已证实，炎症疾病患者体内此类酶的血清活性会发生显著改变。本研究针对由斯坦福大学牵头的国际人类个人组学图谱(hPOP)联盟招募的340名健康志愿者组成的大型队列，分析了血清中丹酰化缓激肽(dabsylated BK)的切割自然变异情况，以及其两种主要降解片段的生成量。研究观测到不同采样点间存在批次效应。在各独立样本子集内，可检测到男性血清中的蛋白酶活性在统计学上显著高于女性。此外还检出异常值，提示实验检测结果与未治糖尿病状态及大量运动存在相关性；而检测结果与年龄、种族、体重指数或隔夜空腹状态无显著相关性。本研究为该神经肽报告检测法提供了健康人群参考值区间。值得注意的是，本实验对样本质量及采集流程极为敏感，研究结果再次强调了在分析前样本采集与处理环节实施高标准标准化的重要性。