Infant blood samples were collected at postnatal days (PND) 1, 7, 14, and 28, and at postmenstrual age (PMA) 32, 36, and 40 weeks. The blood was allowed to clot at 4°C for a minimum of 45 min and a maximum of 2 h before centrifugation at room temperature at 1500 g for 10 min. The serum was then transferred into cryovials and stored at −20°C for up to 1 week before long-term storage at −80°C until analysis. All samples had been subjected to at least one, but less than five, freeze-thaw cycle before NMR analysis.
Serum samples (50 μl) were prepared and then analyzed on an Oxford 800 MHz magnet equipped with an Avance III HD console and 3 mm TCI cryoprobe (Bruker BioSpin). Details of sample processing and the 1H NMR analysis have been published (Nilsson et al., 2020 (link)). Tentative annotations of peaks were made using ChenomX 8.3 (ChenomX Inc.) and the spectral data in the Human Metabolome Data Bank (Wishart et al., 2018 (link)). In total, 260 NMR features were detected in the serum samples. From these, 31 metabolites could be chemically and structurally annotated. In instances where multiple features represented a single metabolite, a strong well-separated peak was selected, or two or more peaks were summarized. All metabolite levels are reported as normalized NMR signals or as standardized values.
Serum samples (50 μl) were prepared and then analyzed on an Oxford 800 MHz magnet equipped with an Avance III HD console and 3 mm TCI cryoprobe (Bruker BioSpin). Details of sample processing and the 1H NMR analysis have been published (Nilsson et al., 2020 (link)). Tentative annotations of peaks were made using ChenomX 8.3 (ChenomX Inc.) and the spectral data in the Human Metabolome Data Bank (Wishart et al., 2018 (link)). In total, 260 NMR features were detected in the serum samples. From these, 31 metabolites could be chemically and structurally annotated. In instances where multiple features represented a single metabolite, a strong well-separated peak was selected, or two or more peaks were summarized. All metabolite levels are reported as normalized NMR signals or as standardized values.
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