Determination of Short Chain Fatty Acids in Meconium from Healthy Term Infants

Abstract

Background: Short-chain fatty acids (SCFA) are metabolites produced by bacteria that can be found in the human gut. They have been shown to have several beneficial effects on the human health, one of them is to enhance the immune system by colonization resistance. The purpose of this study was to investigate the abundance of short chain fatty acids in meconium from healthy term born infants, as well as to develop sample preparation methods for metabolomics and DNA extraction from stool samples. The results will be used as a reference in a comparison with age-matched group of infants treated with antibiotics, to characterise how antibiotics use affects SCFA profile of the neonatal gut. Method: Stool samples were collected from 39 healthy infants born week 35-42, within 48 hours after birth. The samples were mixed with 95% ethanol, homogenised, aliquoted, and stored in a -80°C freezer until preparation. When preparing, the samples were divided in three parts: for metabolomics, dry weight measurement and DNA-extraction. We detected SCFA concentrations by targeted mass spectrometry-based technique and used the dry weight determination to normalise for different solvent content between stool samples. We also measured the DNA-concentration in 29 of the 39 samples. For statistical analysis available metadata to correlate with SCFA-profiles were: age at the time of sample collection (hours), birth weight (grams), time from sample collection to the sample was put in the freezer (hours), and DNA-concentration. Results: The most abundant SCFA detected were acetate, propionate and butyrate. Also the organic acids (OA) lactate and succinate were analysed and came out with relatively high values. The remaining 10 SCFA had very low concentrations. The 15 compounds showed slightly positive correlation with age the infants, and the number of hours passed from sample collection until it was put in the freezer. They also showed slightly negative correlation with birth weight of infants, and DNA concentration in the faecal samples. Conclusion: Main conclusion is that acetate, propionate and butyrate are the three most abundant SCFA of the infant gut metabolome. No conclusions are made based on correlation analyses, due to a small population and some inaccuracies in the method.