Associations of Early Gut Microbiome and Metabolome with Growth and Body Composition of Preterm Infants Within the First 6 Months

Objectives: This study aimed to explore the associations of growth and body composition with gut microbiome and metabolome in preterm infants. Materials and Methods: A prospective cohort study including 73 human milk-fed very preterm infants was conducted. During hospitalization, fecal samples were collected to detect microbes and metabolites using 16S rRNA gene sequencing and liquid chromatography-mass spectrometry. Growth and body composition indices were measured at term equivalent age (TEA) and 6 months of corrected age (CA). Associations of the fecal microbiome and metabolome profiles with growth and body composition indices, as well as their changes, were analyzed. Results: A higher abundance of Streptococcus was associated with a lower fat-free mass (FFM) z-score at 6 months of CA (p = 0.002) and a smaller increase in FFM z-score from TEA to 6 months of CA (p = 0.018). Higher levels of 3'-sialyllactose and 6'-sialyllactose (6'-SL) in feces were correlated with a lower z-score of percentage body fat (PBF) (p = 0.018 and 0.020, respectively) and a lower z-score of fat mass (p = 0.044 and 0.043, respectively) at 6 months of CA. A higher level of 6'-SL in feces was correlated with a greater increase in FFM z-score from TEA to 6 months of CA (p = 0.021). Conclusions: This study sheds light on the role of specific microbial-host interactions in metabolic changes in preterm infants, indicating the potential role of sialylated human milk oligosaccharides in optimizing body composition.