Previously, fragments from Sirtuin 1 (SIRT1) were identified in preclinical and clinical samples to display an increase in serum levels for N-terminal (NT) SIRT1 vs. C-terminal (CT) SIRT1, indicative of early signs of OA. Here we tested NT/CT SIRT1 levels as well as a novel formulated sandwich assay to simultaneously detect both domains of SIRT1 in a manner that may inform us about the levels of full-length SIRT1 in the circulation (flSIRT1) of clinical cohorts undergoing knee joint distraction (KJD). We employed an indirect ELISA assay to test NT- and CT-SIRT1 levels and calculated their ratio. Further, to test flSIRT1 we utilized novel antibodies (Ab), which were validated for site specificity and used in a sandwich ELISA method, wherein the CT-reactive served as capture Ab, and its NT-reactive served as primary detection Ab. This method was employed in human serum samples derived from a two-year longitudinal study of KJD patients. Two-year clinical and structural outcomes were correlated with serum levels of flSIRT1 compared to baseline. Assessing the cohort, exhibited a significant increase of NT/CT SIRT1 serum levels with increased osteophytes and PIIANP/CTX-II at baseline, while a contradictory increase in NT/CT SIRT1 was associated with less denuded bone, post-KJD. On the other hand, flSIRT1 exhibited an upward trend in serum level, accompanied by reduced denuded bone for 2-year adjusted values. Moreover, 2 year-adjusted flSIRT1 levels displayed a steeper linear regression for cartilage and bone-related structural improvement than those observed for NT/CT SIRT1. Our data support that increased flSIRT1 serum levels are a potential molecular endotype for cartilage-related structural improvement post-KJD, while NT/CT SIRT1 appears to correlate with osteophyte and PIIANP/CTX-II reduction at baseline, to potentially indicate baseline OA severity.

中文翻译：

---

两年后牵引软骨相关结构改善伴随着血清全长 SIRT1 的增加


此前，在临床前和临床样本中鉴定了 Sirtuin 1 (SIRT1) 的片段，显示 N 端 (NT) SIRT1 与 C 端 (CT) SIRT1 的血清水平增加，表明 OA 的早期迹象。在这里，我们测试了 NT/CT SIRT1 水平以及一种新颖的夹心测定法，以同时检测 SIRT1 的两个域，这种方式可以让我们了解接受膝关节治疗的临床队列循环中全长 SIRT1 的水平 (flSIRT1)分心（KJD）。我们采用间接 ELISA 测定来测试 NT-和 CT-SIRT1 水平并计算它们的比率。此外，为了测试 flSIRT1，我们使用了新型抗体 (Ab)，该抗体经过位点特异性验证并用于夹心 ELISA 方法，其中 CT 反应性用作捕获 Ab，其 NT 反应性用作主要检测 Ab。该方法用于对 KJD 患者进行的为期两年的纵向研究中获得的人血清样本。与基线相比，两年的临床和结构结果与 flSIRT1 的血清水平相关。评估队列时，基线时 NT/CT SIRT1 血清水平随着骨赘和 PIIANP/CTX-II 的增加而显着增加，而 KJD 后 NT/CT SIRT1 的矛盾增加与骨质剥脱较少相关。另一方面，flSIRT1 的血清水平呈上升趋势，伴随着 2 年调整值的裸露骨减少。此外，2 年调整后的 flSIRT1 水平显示出比 NT/CT SIRT1 观察到的软骨和骨相关结构改善更陡峭的线性回归。 我们的数据支持 flSIRT1 血清水平升高是 KJD 后软骨相关结构改善的潜在分子内型，而 NT/CT SIRT1 似乎与基线时骨赘和 PIIANP/CTX-II 减少相关，可能表明基线 OA 严重程度。