Short chain fatty acids and bile acids in human faeces are associated with the intestinal cholesterol conversion status.

BACKGROUND AND PURPOSE: The analysis of human faecal metabolites can provide an insight into metabolic interactions between gut microbiota and host organism. The creation of metabolic profiles in faeces has received little attention until now and reference values, especially in the context of dietary and therapeutic interventions, are missing. Exposure to xenobiotics significantly affects the physiology of the microbiome and microbiota manipulation as well as short chain fatty acids administration have been proposed as treatment targets for several diseases. The aim of the present study is to give concomitant concentration ranges of faecal sterol species, bile acids and short chain fatty acids based on a large cohort.

EXPERIMENTAL APPROACH: Sterol species, bile acids and short chain fatty acids in human faeces from 165 study participants were quantified by LC-MS/MS. For standardization, we refer all values to dry weight of faeces. Based on the individual intestinal sterol conversion we classified participants into low and high converters according to their coprostanol/cholesterol ratio.

KEY RESULTS: Low converters excrete more straight chain fatty acids and bile acids than high converters. 5 , 95 percentile and median of bile acids and short chain fatty acids were calculated for both groups.

CONCLUSION AND IMPLICATIONS: We give concentration ranges for 16 faecal metabolites that can serve as reference values. Patient stratification into high or low sterol converter groups is associated with significant differences in faecal metabolites with biological activities. Such stratification should then allow assessing faecal metabolites better before therapeutic interventions.