Impact of dietary methionine, tryptophan, and niacin deficiency on gut microbiota in mice.

Emerging evidence indicates that selective nutrient restriction can reproduce metabolic benefits. Although methionine and branched-chain amino acid limitation improve metabolism and reshape the gut microbiome, the effects of other nutrients are still unclear. In this study, we examine the consequences of restricting methionine, tryptophan, and niacin, and find that their transient deprivation induces significant changes in gut microbiota. BALB/c and C57BL/6J mice were fed either a control diet, a methionine-restricted (MR) diet, a diet lacking tryptophan and niacin (TNR), or a combined diet deficient in methionine, tryptophan, and niacin (MTNR) for 13 days. Following the dietary intervention, we performed16S rRNA sequencing to assess gene expression changes in the intestine. We also performed RNA-seq analysis of intestinal gene expression in mice that had been returned to a normal diet for two days following dietary restriction (rMR, rTNR, and rMTNR). Furthermore, fecal microbiota transplantation (FMT) was performed by transferring feces from rMR, rTNR, and rMTNR mice into MTNR mice that had been maintained on the MTNR diet for 15 days. FMT was conducted once daily for two consecutive days, and gut microbiota was analyzed one day after the second transplantation. We also performed gut microbiota analysis following changes in the duration of nutrient restriction.