GC-MS analysis of short chain fatty acids and branched chain amino acids in urine and faeces samples from newborns and lactating mothers

Background: Short chain fatty acids (SCFAs) and branched chain amino acids (BCAAs) are frequently determined in faeces, and widely used as biomarkers of gut-microbiota activity. However, collection of faeces samples from neonates is not straightforward, and to date levels of these metabolites in newborn's faeces and urine samples have not been described. Methods: A targeted gas chromatography - mass spectrometry (GC-MS) method for the determination of SCFAs and BCAAs in both faeces and urine samples has been validated. The analysis of 210 urine and 137 faeces samples collected from preterm (PI), term infants (TI) and their mothers was used to report faecal and urinary SCFA and BCAA levels in adult and neonatal populations. Results: A significant correlation among five SCFAs and BCAAs in faeces and urine samples was observed. Reference ranges of SCFAs and BCAAs in mothers, PI and TI were reported showing infant's lower concentrations in faeces and higher concentrations in urine. Conclusion: This method presents a non-invasive approach for the simultaneous assessment of SCFAs and BCAAs in faecal and urine samples and the results will serve as a knowledge base for future experiments that will focus on the study of the impact of nutrition on the microbiome of lactating mothers and their infants.