Objective To investigate the potential role of transthyretin (TTR) in the early diagnosis of rheumatoid arthritis (RA) by detecting the levels of TTR and types of its chemical modification in RA patients' sera with proteomics-based analysis. Methods Serum levels of TTR were measured by enzyme-linked immunosorbent assay (ELISA) from 39 RA patients [ 16 cases (course of disease ＜ 1 year) and 23 cases ( ＞2 years) ], 20 osteoarthritis (OA) patients and 20 age and sex matched healthy subjects. Western blot was used to determine the ratio of TTR polymers. The relative types and proportion of TTR modification in serum were identified by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). Results Serum levels of TTR were significantly higher in early stage RA patients [ (502.46 ± 109.25 ) mg/L] than those in healthy controls [ (424.98 ± 118.52)mg/L] (P＜0.05). TTR levels in middle and late stage patients [(440.67 ±94.15) mg/L] were shown to have increasing tendency, but there was no statistical difference with those in controls ( P = 0. 733 ). No significant differences were detected between OA patients [ (363.91 ± 106.41 ) mg/L] and healthy controls ( P = 0.072 ). 4 major peaks of TTR were 13 749.86 ± 1.48 mass-to-charge ratio ( m/z), 13 829.63 ± 2.76 m/z, 13 870.70 ± 2.70 m/z and 13 927 ±5.77 m/z, corresponding to native TTR, sul-TTR, cys-TTR and cysgly-TTR, respectively. Meanwhile, the proportion of.TTR modification changed with the course of disease. Conclusions 4 types of TTR peaks are found in serum, and the proportion of TTR modification in RA changes with the course of disease. Serum TTR levels are increased in early stage RA patients, and it may be a potential marker for the early diagnosis of RA.%目的 通过检测类风湿关节炎(RA)患者血清转甲状腺素蛋白(TTR)的化学修饰类型和含量,探讨其在RA早期诊断中的潜在作用.方法 采用酶联免疫吸附试验(ELISA)测定39名RA患者[早期(＜1年)16例,中晚期(＞2年)23例]、20名骨性关节炎(OA)患者及20名健康体检者血清TTR含量;采用Western blot测定血清TTR分子聚合体比例;采用基质辅助激光解吸离子化飞行时间质谱(MALDI-TOF-MS)技术鉴定血清中TTR蛋白的化学修饰类型和比例.结果 RA早期患者血清TTR含量为(502.46±109.25)mg/L,明显高于正常对照组[(424.98±118.52)mg/L](P<0.05);RA中晚期患者[(440.67±94.15) mg/L]也有增高趋势,但与正常对照组比较差异无统计学意义(P＝0.733);OA组TTR含量为(363.91±106.41)mg/L,与正常对照组比较差异无统计学意义(P＝0.072).血清TTR化学修饰有4种蛋白峰:质荷比(m/z) 13 749.86±1.48、m/z 13 829.63±2.76、m/z 13 870.70±2.70、m/z 13 927±5.77,分别对应野生型TTR(native TTR)、磺化TTR (sul-TTR)、半胱氨酰化TTR(cys-TTR)和半胱氨酰甘氨酰化TTR(cysgly- TTR),且TTR修饰比例随病程发生变化.结论 RA患者血清TTR质谱分析发现 4个TTR蛋白峰,且修饰比例随病程不同而发生改变;早期RA患者血清TTR含量增加,血清TTR水平有可能作为RA早期诊断的潜在指标.
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