Evaluating the Impact of Four Major Nutrients on Gut Microbial Metabolism by a Targeted Metabolomics Approach

Gut
microbiome plays fundamental roles in host physiology, and
gut microbial metabolism is important to the host–microbiome
homeostasis. As major contributors to gut microbial metabolism, the
medium nutritional components are essential to in vitro gut microbiome
growths, and four nutrients, namely, inorganic salts, bile salts,
short-chain fatty acids (SCFAs), and mucin, have gained particular
attention because of their significant variation found in different
growth environments and their ability to modulate the gut microbial
population and functions. However, a systematic study is lacking to
evaluate the effects of these four nutrients on the gut microbiome
in terms of their impact on the microbial metabolic profiles. To fill
the gap of the knowledge, we applied mass-spectrometry-based targeted
metabolomics approach to study the regulation effects of these four
medium components on in vitro-cultured gut microbiota. Our results
show that inorganic salts and mucin had the greatest impacts on the
gut microbiome metabolic profile compared to the other components
studied, with gut microbial cultures grown with low-concentration
inorganic salts and mucin-supplemented medium demonstrating greater
numbers of metabolites detected. We also applied metabolic pathway
impact analysis, which revealed several significantly impacted metabolic
pathways during the comparison of different medium supplements, which
could further assist our understanding of the overall impacts of certain
critical nutrients on gut microbial metabolism. In summary, this pilot
study can serve as a first attempt to evaluate the individual nutritional
component in their contribution to gut microbial metabolic functions.