Mass spectrometry-based analysis of gut microbial metabolites of aromatic amino acids

Abstract

Small molecules derived from gut microbiota have been increasingly investigated to better understand the functional roles of the human gut microbiome. Microbial metabolites of aromatic amino acids (AAA) have been linked to many diseases, such as metabolic disorders, chronic kidney diseases, inflammatory bowel disease, diabetes, and cancer. Important microbial AAA metabolites are often discovered via global metabolite profiling of biological specimens collected from humans or animal models. Subsequent metabolite identity confirmation and absolute quantification using targeted analysis enable comparisons across different studies, which can lead to the establishment of threshold concentrations of potential metabolite biomarkers. Owing to their excellent selectivity and sensitivity, hyphenated mass spectrometry (MS) techniques are often employed to identify and quantify AAA metabolites in various biological matrices. Here, we summarize the developments over the past five years in MS-based methodology for analyzing gut microbiota-derived AAA. Sample preparation, method validation, analytical performance, and statistical methods for correlation analysis are discussed, along with future perspectives.

Keywords: Aromatic amino acid; Gut microbial metabolite; Mass spectrometry; Metabolomics; Quantitative analysis.

Graphical abstract

Fig. 1

Overview of workflow for discovery and validation of gut microbial metabolites in clinical research. A: study design and sample collection, B: sample preparation and metabolite profiling via untargeted or semi-targeted analysis using MS-based methods followed by substantial statistical analysis, C: proposed candidate metabolites, D: Targeted analysis to confirm metabolite identity and determine their absolute concentrations.

Fig. 2

Summary workflow of data input and data handling of metabolome and microbiome before correlation analysis.