背景：

肺炎支原体肺炎是儿童常见的社区性获得性肺炎，而且近年来重症肺炎支原体肺炎发病率有升高趋势。磷脂在肺表面活性物质脂质成分中占90%，是细胞膜的重要结构成分，是许多炎症物质的前体物质，也是支原体能量和碳源的主要来源。随着代谢组学的发展，国外已有学者发现肺炎的发生发展与磷脂有关，但国内对儿童肺炎支原体肺炎与磷脂的相关临床研究鲜有报道。

目的：

1.分析磷脂在MPP中的变化特征及其对SMPP的预测价值；

2.比较MPP与正常儿童间的代谢组学差异，分析代谢改变在MPP病理生理过程中的影响，筛选磷脂代谢谱中对SMPP有预测价值的成分。

方法：

1.回顾性研究319例MPP住院患儿临床资料，比较MPP与SMPP患儿的磷脂水平差异，分析其对SMPP及混合感染的预测价值；

2.另以50例单纯MPP住院患儿为病例组，50名健康体检儿童作为对照组，分别采集其临床信息，并留取入院后24小时内血清，采用超高效液相色谱质谱法测定代谢产物，无监督的主成分分析及有监督的正交偏最小二乘法相结合找到组间的差异代谢物，并通过MBRole进行通路富集分析。将有显著性差异的磷脂类物质进行预测SMPP的受试者工作曲线分析；

结果：

1.319例MPP患儿中重症组91例，男45例，女46例，平均年龄3.71±3.73岁；普通组228例，男131例，女97例，平均年龄3.98±3.87岁，两组间患儿性别年龄无显著性差异。SMPP组磷脂显著降低（P<0.05）。磷脂降低是SMPP的危险因素（OR=0.359，P<0.05），在预测SMPP中的曲线下面积（AUC）为0.673，敏感性为0.747，特异性为0.491，临界值为1.79mmol/L（P<0.05）。在SMPP中磷脂降低组心脏损害发生率及发热时间为分别为34.9%，5.28±2.35天，显著大于磷脂正常组（P<0.05）。磷脂与MPP发生混合病毒感染的OR值为0.34（P<0.05），预测MPP发生混合病毒感染的AUC为0.604，敏感性0.904，特异性为0.36，临界值为1.685mmol/L，P<0.05）;

2.MPP组患儿共50例，其中男27名、女23名，年龄6±3.65岁，健康对照组儿童50例，男28名、女22名，年龄为6.62±2.64岁，两组间的年龄性别无显著性差异；共检测出392种差异代谢物，与对照组相比，在MPP中降低的有306种，升高的有86种。其中变量权重值（variable important in projection, VIP）>5且P<0.05的差异代谢物有41种，在MPP中降低的有38种，主要为磷脂酰胆碱、磷脂酰丝氨酸、磷脂酰乙醇胺、溶血磷脂、鞘磷脂等磷脂类物质。升高的有3种，分别为牛磺熊去氧胆酸、二十五碳五烯酸、5,6-环氧基-8,11,14顺-二十碳三烯酸；

3.通路富集分析结果显示，MPP涉及的代谢通路包括苯丙氨酸、酪氨酸、色氨酸、不饱和脂肪酸、氨酰tRNA的生物合成,胰岛素信号途径及ABC转运蛋白的代谢;

4．将代谢组学检测中50例MPP分为重症组和普通组，SMPP患儿25例，平均年龄6.35±3.8岁，其中男15人，女10人；普通MPP患儿25例，平均年龄5.66±3.54岁，男12人，女13人。两组患儿在性别年龄方面无显著性差异（P>0.05）。选择VIP>1,P<0.05且差异倍数FC>2或FC<0.5的磷脂类物质有14种， 其中磷脂酰胆碱PC(18:4(6Z,9Z,12Z,15Z)/20:5(5Z,8Z,11Z,14Z,17Z))的曲线下面积为0.6864，敏感性为0.96, 特异性为0.44，磷脂酰胆碱PC(16:1(9Z)/16:1(9Z))的曲线下面积为0.664,敏感性为0.64，特异性为0.72。

结论:

1.与普通MPP相比，SMPP患儿血清磷脂水平显著降低。当磷脂低于1.79mmol/L时需警惕SMPP的发生，在磷脂降低时SMPP患儿心脏损害发生率更高，发热时间更长；当血清磷脂低于1.685mmol/L时需警惕MPP混合病毒感染的可能；

2.MPP患儿与正常儿童的代谢轮廓存在显著差异，不饱和脂肪酸、氨酰tRNA、苯丙氨酸、酪氨酸、色氨酸的生物合成,胰岛素信号途径及ABC转运蛋白的代谢参与了肺炎支原体肺炎的发生发展；

3.磷脂酰胆碱、磷脂酰乙醇胺、磷脂酰丝氨酸、磷脂酸等磷脂类物质在肺炎支原体感染后显著降低，其中磷脂酰胆碱PC(18:4(6Z,9Z,12Z,15Z)/20:5(5Z,8Z,11Z,14Z,17Z)和 PC(16:1(9Z)/16:1(9Z))对于SMPP具有一定预测价值；

Background：

Mycoplasma pneumoniae pneumonia (MPP) is a common community-acquired pneumonia in children. The incidence of Severe mycoplasma pneumoniae pneumonia (SMPP) has been increasing in recent years. Phospholipids account for 90% of the lipid components of lung surfactants, which are important structural components of cell membranes , precursors of many inflammatory substances, and the main nutrients required for the survival of mycoplasma. With the development of metabonomics, foreign scholars have found that the occurrence and development of pneumonia is related to phospholipids. In China, there are few clinical studies on relationship of mycoplasma pneumoniae pneumonia and phospholipids in children.

Objective：

1. Analyze the difference of phospholipids levels in serum with MPP and evaluate its predictive efficiency for SMPP;

2. The metabolomic differences between MPP and normal children were compared to analyze the influence of metabolic changes on the pathophysiological process of MPP, and to evaluate the components of phospholipid on predictive efficiency for SMPP.

Methods：

1. Clinical data of 319 hospitalized children with MPP were retrospectively studied to compare the difference of phospholipid levels between MPP and SMPP, and to analyze the predictive efficiency of phospholipid in SMPP and co-infection;

2. A total of 50 children with mycoplasma pneumonia as the case group were recruited from and meanwhile 50 age- and gender-matched heathy children were selected and formed the control group. Clinical information and serum samples were collected within 24 hours after admission. Serum metabolites were quantified by using the untargeted ultra-high performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) technique. Unsupervised principle component analysis and (orthogonal) partial least-squares-discriminant analysis were employed to identify differential metabolites. MBRole software was used for pathway enrichment analysis. The predictive efficiency was evaluated by the receiver operating curve.

Results：

1. There were 45 boys and 46 girls in SMPP group with an average age of 3.71±3.73 years. There were 131 boys and 97 girls in mild MPP with an average age of 3.98±3.87 years old. There was no significant difference in gender and age between groups. Phospholipid in SMPP group was significantly decreased (P<0.05). Decrease of phospholipids was a risk factor for SMPP (OR=0.359, P<0.05). The area under the curve (AUC) was 0.673 (sensitivity 0.747, specificity 0.491), and the cut-off value was 1.79mmol/L(P<0.05). The incidence of heart damage was significantly increased and the days of fever was significantly prolonged in SMPP group (P<0.05).Phospholipid was a risk factor for mixed virus infection in MPP (OR=0.34, P<0.05). The AUC of phospholipid was 0.604(sensitivity 0.904, specificity 0.36), and the cut-off value was 1.685mmol/L, P<0.05.

2. There were 27 boys and 23 girls in the case group with an average age of 6.0±3.65 years, and the control group consisted of 28 boys and 22 girls with an average age of 6.62±2.64 years. A total of 392 different metabolites were detected. Compared with the control group, 306 metabolites were decreased and 86 increased in case group. Forty-one differential metabolites with variable important in projection (VIP) values >5 and P < 0.05 were demonstrated, mainly concentrated on phospholipid. 38 metabolites were significantly lower in the case group, 4 metabolites were significantly higher than that of the control group.

3. Metabolic enrichment analysis showed that different metabolites were related to the biosynthesis of phenylalanine, tyrosine, tryptophan, unsaturated fatty acid, ammonia acyl tRNA and insulin signaling pathway, as well as the metabolism of ABC transporters.

4. For further analysis of the result before, MPP group was divided. There were 15 boys and 10 girls in SMPP group with an average age of 6.35±3.8 years, and mild MPP group consisted of 12 boys and 13 girls with an average age of 5.66±3.54 years. There was no significant difference in gender and age (P<0.05).14 phospholipids were selected for VIP>1, P<0.05, and FC>2 or FC<0.5. AUC of PC (18:4(6Z,9Z,12Z,15Z)/20:5(5Z,8Z,11Z,14Z,17Z) was 0.6864(sensitivity 0.96, specificity 0.44, and the AUC of PC (16:1(9Z)/16:1(9Z)) was 0.664(sensitivity 0.64, specificity 0.72).

Conclusion：

1. Serum phospholipid level in children with SMPP was lower. We should paid attention to the tendency of SMPP when phospholipid was lower than 1.79mmol/L. SMPP children with lower phospholipid level had longer fever time and higher incidence of heart damage. When serum phospholipid was lower than 1.685mmol/L, we should be alert to the possibility of MPP mixed virus infection.

2. The metabolic profile of MPP children is significantly different from that of normal children. The biosynthesis of unsaturated fatty acids, aminoyl tRNA, phenylalanine, tyrosine, tryptophan, insulin signaling pathway and metabolism of ABC transporter are involved in the development of Mycoplasma pneumoniae pneumonia.

3. Phosphatidylcholine were significantly decreased after Mycoplasma pneumoniae infection. PC(18:4(6Z,9Z,12Z,15Z)/20:5(5Z,8Z,11Z,14Z,17Z) and PC (16:1(9Z)/16:1(9Z)) may help us to predict SMPP.