Integrating 16S rDNA sequencing analysis and targeted tryptophan metabolomics to reveal potential mechanism of mulberry leaf extract in treating type 2 diabetes mellitus mice.

This study aims to explore the roles that the interplay between tryptophan (TRP) metabolism and gut microbiota plays in experimental type 2 diabetes mellitus (T2DM) mice treated with mulberry leaf extracts. Fecal and serum TRP metabolites were analyzed using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) based targeted metabolomics approaches. Concurrently, gut microbiota composition was characterized through high-throughput sequencing of bacterial 16S rDNA. Mulberry leaf extracts administration demonstrated significant improvement in normalizing TRP-related metabolite concentrations in serum from T2DM mice. Affected metabolites comprised 5-hydroxyindoleacetic acid, kynurenic acid, 3-hydroxyanthranilic acid, indole-3-acetic acid, nicotinic acid, indole-3-acetamide, N-acetyl-5-hydroxytryptamine (NAS), 3-indoleglyoxylic acid (IGA), and indole-lactic acid. Concurrently, fecal analysis revealed enhanced levels of indole-3-propionic acid, nicotinic acid, indole acrylic acid (IA), IGA, and indole. These modifications coincided with measurable alterations in gut microbial composition, particularly affecting bacterial genera such as Streptococcus, Acinetobacter, Weissella, Lachnoclostridium, Klebsiella, Dorea, Leuconostoc, Rhodococcus, Flavonifractor, Peptococcaceae_unclassified, Erysipelatoclostridiaceae_unclassified, Lachnospiraceae_NK4A136_group, and Christensenellaceae_R-7_group. Correlation analyses identified that Christensenellaceae_R-7_group exhibited significant positive association with serum concentrations of IGA and NAS alongside fecal IA levels. Conversely, Flavonifractor displayed strong positive correlation with both serum nicotinic acid and fecal indole content. The ameliorative impact of mulberry leaf extracts on T2DM may be attributed to its modulatory effects on both gut microbiota dysbiosis and TRP metabolic pathway disturbances. This therapeutic mechanism appears to contribute substantially to the observed mitigation of diabetic symptoms, particularly through the restoration of microbial homeostasis and optimization of TRP-related biochemical processes within the organism.