Gut microbiome and urinary metabolomic alterations in Chinese infants with functional constipation and yin-deficiency constitution.

Background: Functional constipation (FC) is common in early childhood and is closely associated with gut microbiota imbalance. According to Traditional Chinese Medicine (TCM) constitution theory, infants can be categorized into different constitution types, among which the yin-deficiency constitution is particularly linked to a higher risk of FC. However, data specifically addressing this association in infants remain limited. Methods: Infants under 2 years of age were assessed for yin-deficiency and balanced constitutions using a TCM Constitution Questionnaire, and FC was diagnosed according to the Rome IV criteria. The study enrolled 31 infants with yin-deficiency constitution and FC (YINDC) and 31 infants with balanced constitution and without FC (BC, controls). Evaluations included Bristol Stool Scale scores, constipation symptoms, fecal microbiota profiles, and urinary metabolite characteristics. Results: The YINDC group exhibited significantly lower Bristol Stool Scale scores and more severe FC symptoms than the BC group. Marked differences in gut microbial composition and metabolite profiles were observed between the two groups, with main alterations identified in the sphingolipid signaling and metabolism pathways. Conclusion: This study compares gut microbial and urinary metabolomic profiles between infants with the combined yin-deficiency constitution/FC phenotype and balanced non-constipated controls. We identified preliminary microbiota and metabolomic differences between the two groups, involving sphingolipid-related pathways. However, these differences cannot be specifically attributed to yin-deficiency constitution, FC, or their interaction. Our findings provide a preliminary basis for future investigation of the gut microbiome-metabolome axis in TCM-integrated FC management, but require validation in independent cohorts.