Analysis of Serotonin in Human Feces Using Solid Phase Extraction and Column-Switching LC-MS/MS

Abstract

Serotonin, an important neurotransmitter, is produced mainly in intestines, and serotonin levels in feces can be an indicator of the intestinal environment. Human feces, however, contain a large amount of contaminants, which vary widely owing to food contents and the intestinal environment, and these contaminants would be expected to interfere with the determination of serotonin levels in human feces. To remove these contaminants and determine serotonin levels, we developed a new method using solid phase extraction (SPE) and column-switching LC-MS/MS. Serotonin, labeled with a stable isotope, was added to human feces samples prior to SPE as an internal standard to correct for individual di erences in matrix e ects. e recovery rate for SPE was 55.9-81.0% (intraday) and 56.5-78.1% (interday) for feces from two subjects. We analyzed 220 fecal samples from 96 subjects including 76 pregnant and post-delivery women. e endogenous serotonin content per unit weight of dried feces was 0.09-14.13 ng/mg for pregnant and post-delivery women and 0.30-9.93 ng/mg for the remaining subjects.

An evaluation of the rat intestinal monoamine biogeography days following exposure to acute stress

“…Fecal biomarkers are commonly used as gross measures of GI mucosal physiology ( Burri and Beglinger, 2014 ; Chong et al, 2019 ). For instance, fecal neurochemical concentrations commonly serve as a correlate of neurochemical patterns in intestinal mucosa environment ( Assche, 2011 ; Hirabayashi et al, 2020a ). Therefore, it is of interest to note the discrepancies between the patterns of 5-HT and DA levels observed in fecal content compared to the intestinal tissue, suggesting fecal neurochemical changes may not always reflect those across the entire intestinal tract.…”

“…Indeed, some evidence exists suggesting pharmacological or probiotic approaches that can reduce the activity of intestinal 5-HT following stress exposure may be effective at attenuating rodent GI distress ( Hirata et al, 2008 ; Li et al, 2019b ). However, it is still unclear how stress influences the entire intestinal monoaminergic biogeography, as research has been typically limited to the examination of a single monoamine that is characterized within one or two gut regions, or just in fecal matter ( Mönnikes et al, 2001 ; Dong et al, 2016 , 2017 ; Li et al, 2019b ; Hirabayashi et al, 2020 ; Li et al, 2022 ). This is an important consideration, as monoamine neurotransmitters interact in complex and coordinated manners to influence biological processes and sub-regions of the gut are not autonomous in function ( Bowcutt et al, 2014 ; Donaldson et al, 2015 ; Kennedy and Chang, 2020 ; Bauer et al, 2021 ).…”