Citrin缺陷导致婴儿肝内胆汁淤积症的血浆氨基酸谱特点

Characteristics of the plasma amino acid spectrum of neonatal intrahepatic cholestasis caused by citrin deficiency

目的研究Citrin缺陷导致的婴儿肝内胆汁淤积症（NICCD）血浆氨基酸谱改变特点，为NICCD的临床诊断提供线索。方法2003年6月至2009年9月就诊的婴儿胆汁淤积症患儿182例，分为三组：NICCD组24例、胆道闭锁（BA）组20例及不明原因肝内胆汁淤积症（INH）组138例。比较3组患儿间18种血浆氨基酸、各氨基酸所占总氨基酸比例、部分氨基酸之间的比值，并对上述数值进行受试者工作特征（ROC）曲线分析。用Kruskal—Wallis检验和Wilcoxon秩和检验进行统计学分析。结果NICCD组与BA组和INH组比较，血浆丙氨酸水平（136．3μmol／L对比175．7μμmol／L和205．7μmol／L，P=0．0001）、血浆天冬氨酸水平（31．55μmol／L对比47．5μmol／L和43．1μmol／L，P=0．0041）、血浆谷氨酸水平（175．71μmol／L对比276．16μmol／L和263．24μmol／L，P=0．0075）、血浆色氨酸水平（28．51μmol／L对比41．90和47．97μmol／L，P=0．0003）均明显下降，差异均有统计学意义；血浆蛋氨酸水平（71．40μmol／L对比28．24μmol／L和29．35μmol／L，P=0．0390）、血浆酪氨酸水平（116．81μmol／L对比55．8μmol／L和57．02μmol／L，P=0．0072）、血浆瓜氨酸水平（97．42μmol／L对比15．09μmol／L和15．65μmol／L，P=0．0001）水平显著升高，差异均有统计学意义。且NICCD组血浆各氨基酸与总氨基酸的比值显示出同样的趋势。瓜氨酸、酪氨酸、蛋氨酸与血浆总氨基酸的比值的ROC下面积分别为0．874[95％可信区间（甜）：0．752～0．996]、0．814（95％CI：0．706～0．923）、0．705（95％CI：0．535～0．875）。瓜氨酸与丙氨酸比值的ROC曲线下面积为0．893（95％CI：0．781～1．005）。取0．14为界值时，敏感度为75％，特异度为95％。结论血浆氨基酸谱变化可为NICCD提供诊断线索，瓜氨酸和丙氨酸比值具有诊断价值。

Objective To investigate the plasma amino acid spectrum in infants 〈 1-year-old with neonatal intrahepatic cholestasis caused by citrin deficiency （NICCD） in order to identify potential diagnostic markers of NICCD. Methods Infants 〈 1 year of age who had been referred to our hospital for investigation of suspected conjugated hyperbilirubinemia between June 2003 and June 2009 were eligible for enrollment. A total of 182 infants were enrolled and divided into three groups： infants diagnosed with NICCD （n = 24）, according to gene testing and/or western blotting results; infants diagnosed with biliary atresia （BA; n = 20）, according to intra-operative cholangiography findings; and infants diagnosed with idiopathic neonatal intrahepatic hepatitis （INH; n = 138）, according toexclusionary findings for diseases affecting the extrahepatic biliary system and no positive serology results to indicate infections with hepatitis B, C, A or E, toxoplasmosis, rubella, herpes simplex, human immunodeficiency virus-1, or syphilis. The plasma amino acid spectrum of each infant was analyzed by tandem mass spectrometry （MS/MS）. The concentrations of 18 amino acids, as well as the ratio of each amino acid to total amino acids, were compared among the three groups. Selected ratios of amino acids were analyzed by receiver operating characteristic （ROC） curve analysis. Results Compared with the BA and INH groups, the NICCD group had significantly lower levels of alanine （Ala; 175.7 and 205.7 vs. 136.3μmol/L, P = 0.0001）, aspartic acid （Asp; 47.5 and 43.1 vs. 31.55μmol/L, P = 0.0041）, glutamic acid （Glu; 276.16 and 263.24 vs. 175.71 μmol/L, P = 0.0075） and tryptophan （Trp; 41.90 and 47.97 vs. 28.51μmol/L, P = 0.0003）, but significantly higher levels of methionine （Met; 28.24 and 29.35 vs. 71.40μmol/L, P = 0.0390）, tyrosine （Tyr; 55.8 and 57.02 vs. 116.81 μmol/L, P = 0.0072） and citrulline （Cit; 15.09 and 15.65 vs. 97.42μmol/L, P = 0.0001）. The ratio of each amino acid to total amino acids showed the same trends for the NICCD group. The calculated areas under the ROC curves of the ratios of Cit, Tyr, and Met to the total amino acids were 0.874 （95% CI：0.752 - 0.996）, 0.814 （95% CI： 0.706 - 0.923）, and 0.705 （95% CI： 0.535 - 0.875） respectively. The calculated area tmder the ROC curve of the ratio of Cit to Ala was 0.893 （95% CI： 0.781 - 1.005）, and when the cut-off value of the ratio of Cit to Ala was 0.14 for diagnosis of NICCD, the sensitivity and specificity were 75% and 95% respectively. Conclusion The plasma amino acid spectrum may represent a diagnostic indicator for NICCD, particularly the ratio of Cit to Ala.