# Gentiopicroside alleviates type 2 diabetes mellitus by attenuating oxidative stress and reshaping gut microbiota in high-fat diet and streptozotocin-induced mice

## TL;DR

Gentiopicroside helps treat type 2 diabetes in mice by reducing oxidative stress and improving gut microbiota diversity.

## Contribution

This study reveals that gentiopicroside's therapeutic effects on T2DM are linked to gut microbiota modulation and activation of the Nrf2/Keap1 pathway.

## Key findings

- GPS reduced blood glucose and insulin levels and improved glucose tolerance in T2DM mice.
- GPS increased gut microbiota diversity and altered the abundance of specific bacterial genera.
- GPS activated the Nrf2/Keap1 pathway in the liver, enhancing antioxidant defenses.

## Abstract

The rising incidence of T2DM, along with the limited efficacy and side effects of current drugs, demands new therapies. Gentiopicroside (GPS) has been shown to improve T2DM and its chronic complications; however, whether these effects are related to modulation of the gut microbiota (GM) remains unclear. Herein, the relationship between the therapeutic effects of GPS on T2DM and GM alterations was investigated using a C57BL/6J mouse model of T2DM induced by a high-fat diet combined with streptozotocin (STZ).

A T2DM model was induced in C57BL/6J mice by high-fat diet combined with STZ. Biochemical methods were used to determine glucose metabolism and oxidative stress-related indices in serum and liver; Western blot was employed to detect the expression of proteins related to the Nrf2/Keap1 signaling pathway in the liver; 16S rRNA high-throughput sequencing was used to detect and analyze gut microbiota in mouse feces.

The results demonstrated that 8 weeks of GPS supplementation significantly reduced blood glucose and insulin levels, improved glucose tolerance and insulin resistance, alleviated liver pathology, enhanced the activity of antioxidant enzymes in serum and liver, increased antioxidant substance levels, and decreased MDA content. Moreover, GPS markedly upregulated the expression protein of Nrf2, HO-1, and NQO1, while downregulating the Keap1 expression in the liver. High-throughput 16S rRNA sequencing further revealed that GPS significantly increased the Chao1 index and Observed_otus index, showed a trend of improving indices such as Shannon, Simpson, Pielou-e, Goods-coverage, and improved β-diversity in fecal samples from T2DM mice. GPS increased the Firmicutes-to-Bacteroidetes (F/B) ratio and reduced the relative abundance of Verrucomicrobiota, Cyanobacteria and Unclassified at the phylum level. At the genus level, GPS increased the relative abundance of Lactobacillus, HT002, Dubosiella, and reduced that of Muribaculaceae_unclassified, Akkermansia, Desulfovibrio, Muribaculum Alloprevotella. Correlation analysis further indicated that the anti-T2DM effects of GPS were closely related to improvements in GM diversity and composition.

In conclusion, these results indicated that GPS can reshape the structural composition and diversity of GM, activate the hepatic Nrf2/Keap1 pathway, and maintain glucose homeostasis.