Analysis of blood metabolites in preterm infants with bronchopulmonary dysplasia using liquid chromatography-tandem mass spectrometry

Objective To analyze the changes in blood metabolites in premature infants with bronchopulmonary dysplasia (BPD) within 36 h and in the 3rd week after birth in order to find new biomarkers for diagnosis of BPD. Methods The BPD group included 20 premature infants (<32 gestational weeks) hospitalized in the Neonatal Intensive Care Unit (NICU) of the Sixth Affiliated Hospital of Sun Yat-sen University and diagnosed with BPD from January 2014 to October 2016. Another 20 non-BPD premature infants with similar gestational age (within one week) who were admitted during the same period were enrolled in the control group. Blood samples of both groups were collected within 36 h and in the 3rd week after birth. Liquid chromatography-tandem mass spectrometry was used to detect blood metabolites and the obtained data were subjected to metabolomics analysis using orthogonal partial least squares discriminant analysis. Chi-square test (or Fisher's exact test), Mann-Whitney U test or t test was used for statistical analysis. Results (1) Twenty and 11 blood samples were collected within 36 h and in the 3rd week after birth from the BPD and the control group, respectively. Compared with the control group, the interval between premature rupture of membranes and delivery, the average length of hospital stay, non-invasive and invasive mechanical ventilation duration and the total duration of supplemental oxygen during hospitalization in the BPD group were longer [M (P25-P75) or (±s): 13.5 (0.0-98.3) vs 0.0 (0.0-0.0) h, Z=3.049; (66.6±20.5) vs (43.9±9.3) d, t=4.574; 267.0 (199.5-516.1) vs 110.5 (0.0-238.5) h, Z=-3.428; 117.5 (0.0-269.3) vs 0.0 (0.0-72.0) h, Z=-2.785; (1 184.0±386.6) vs (595.9±270.3) h, t=5.576; all P<0.05]. (2) Within 36 h after birth, the levels of glycine, proline, tryptophan and piperamide-C5:1 in the BPD group were decreased obviously compared with those in the control group [(201.59±65.01) vs (290.90±137.56) μmol/L, t=-2.625; 103.55 (72.43-434.57) vs 439.48 (103.80-608.98) μmol/L, Z=-2.245; 29.54 (20.30-41.04) vs 47.42 (29.46-73.57) μmol/L, Z=-2.326; 50.04 (35.29-104.78) vs 95.79 (76.21-129.97) μmol/L, Z=-2.029; all P<0.05]. However, the glutamate level was increased [(224.30±67.40) vs (182.67±40.87) μmol/L, t=2.362, P<0.05]. (3) In the 3rd week after birth, the levels of glycine, proline and tryptophan in the BPD group were lower compared to those in the control group [(185.92±61.51) vs (271.85±115.85) μmol/L, t=-2.177; (39.41±18.22) vs (63.92±17.50) μmol/L, t=-3.217; 90.23 (37.93-146.37) vs 330.15 (47.79-622.90) μmol/L, Z=-2.134; all P<0.05]. However, the ornithine level was higher [(75.09±43.21) vs (39.25±16.53) μmol/L, t=2.569, P<0.05]. Conclusions Glycine, proline and tryptophan in blood are potential biomarkers for early diagnosis of BPD. Key words: Bronchopulmonary dysplasia; Amino acids; Metabolomics; Chromatography, liquid; Tandem mass spectrometry