Presented at the Neonatal Society 2010 Summer Meeting.
Hyde MJ1, Beckonert OP2, Yap IKS2, Booms C1, Gale CRK1, Logan K1, Karataza A1, Murgasova D1, Holmes E2, Modi N1
1 Neonatal Medicine, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London, SW10 9NH, UK
2 Biomolecular Medicine, Sir Alexander Fleming Building, Imperial College London, South Kensington, SW7 2AZ, UK
Background: The composition of biofluids is sensitive to changes in health and physiology. Consequently, screening biofluids using metabolomic technologies has the potential to identify altered physiology and to identify biomarkers of later disease risk. We have previously reported that young adults who were born preterm have an altered urinary metabolome compared to young adults born at term (1). Here we report the use of metabolomics to study the change in the urinary metabolome with post-natal age in preterm neonates and differences from full term infants.
Methods: The study was conducted with Research Ethics Committee approval. Infants were recruited from the post-natal wards or neonatal unit at Chelsea and Westminster Hospital between September 2009 and April 2010. Urine samples were collected using urine bags or cotton wool placed in the infant’s nappy and stored at -20°C until analysis. A single urine sample was collected from term infants; preterm infants were sampled weekly until discharge. Samples were analysed using one-dimensional 1H NMR spectroscopy at 300K on a Bruker LC-NMR 600 MHz spectrometer, using standard parameters and pre-processing algorithms, as previously described (2). The spectra were automatically phased; baseline corrected, referenced using an in-house routine written in MATLAB, normalised to the area under the spectra and bucketed (0.04 ppm width). Spectra were analysed on the basis of experimental group using principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA).
Results: To date we have recruited 32 preterm (24-30 weeks GA) and 16 term (38-42 weeks GA) infants. Preterm infants were studied for between 1-17 weeks (mean 6). The urinary metabolome of preterm infants altered over time, although the pattern of change requires further elucidation. A significant difference in the urinary metabolome of preterm and term neonates was apparent in the first urine samples collected after birth (Fig 1A), and remained evident at term-equivalent age (Fig 1B). Significant differences were identified in the urinary metabolites alanine, formate and citrate (higher in preterm infants) and creatinine, creatine and dimethylglycine (lower in preterm infants).
Figure 1: PLS-DA scores plot of Pareto scaled, 0.04ppm bucketed data from 1H NMR spectra of urine collected within a week of birth from term infants (∆; born 38-42 weeks GA; n = 16) compared to A) urine samples collected within a week of admittance to the neonatal unit from preterm infants (■; born 24-30 weeks GA; n = 32; Q2 = 0.71) and B) urine samples collected from the same preterm infants but at term corrected age (■; 38-42 weeks GA; n = 22; Q2 = 0.81)
Conclusion: The differences in urinary metabolome between term and preterm infants, persisting to term-equivalent age, are indicative of differences in physiology. These data, taken with our observation of an altered urinary metabolome in adults born preterm compared to term, indicate that preterm birth and/or preterm therapies initiate life-long trajectories of altered development. Metabolomic technologies offer a sensitive means to identify the specific biological pathways affected, and may lead to the identification of biomarkers for interventional studies to ameliorate the consequences of preterm birth.
1. Parkinson JR et al (2010) Altered urinary metabolome in young adults born below 33 weeks gestation. Neonatal Society Spring Meeting
2. Beckonert O et al (2007) Nature Protocols 2, 2692-703