# In vitro digestion and fermentation of ginseng pectic polysaccharide GPS-1 and attenuation of its product on oleic acid-induced oxidative stress in HepG2 cells

## TL;DR

This study shows that a ginseng polysaccharide, GPS-1, is fermented by gut bacteria into beneficial compounds that protect liver cells and reduce oxidative stress.

## Contribution

The study is the first to demonstrate that GPS-1's anti-diabetic effects are mediated through gut microbial fermentation into short-chain fatty acids.

## Key findings

- GPS-1 resists digestion but is effectively fermented by gut microbiota, leading to increased short-chain fatty acid production.
- The fermented product of GPS-1 enhances liver cell protection by boosting antioxidant activity and reducing lipid levels.
- Fermentation enriches Bacteroides and generates metabolites with improved hepatoprotective effects.

## Abstract

Based on prior evidence that red ginseng pectin GPS-1 ameliorates T2DM in rats and modulates gut microbiota, we report for the first time that GPS-1 interacts with the gut microbiota of T2DM rats, as demonstrated through an in vitro digestion-fermentation model. This study reports for the first time that GPS-1 is key to its anti-T2DM efficacy. Building on prior findings that GPS-1 modulates gut microbiota in diabetic rats, we employed an in vitro digestion-fermentation model to demonstrate how GPS-1 is metabolized by specific bacteria into beneficial metabolites (e.g., short-chain fatty acids), thereby clarifying the causal pathway through which GPS-1 improves host metabolic health.

GPS-1 was subjected to simulated salivary-gastrointestinal digestion in vitro, followed by fecal fermentation. Its physicochemical properties, including molecular weight (Mw), monosaccharide composition, uronic acid and reducing sugar content, were monitored. Short-chain fatty acids (SCFAs) production was quantified by GC-MS, and changes in gut microbiota composition were analyzed by 16S rRNA sequencing. The hepatoprotective effect of the fermented product (GPS-1-I48) was evaluated in oleic acid-treated HepG2 cells by measuring levels of triglyceride (TG), malondialdehyde (MDA), and the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px).

GPS-1 was highly resistant to in vitro digestion, with no significant changes in Mw or carbohydrate composition. However, it was effectively degraded during fermentation, showing marked decreases in Mw and uronic acid content, a shift in monosaccharide profile, and an increase in reducing sugars. Fermentation of GPS-1 significantly modulated the gut microbiota structure of T2DM rats. It also markedly promoted the production of SCFAs. Consequently, the fermented product GPS-1-I48 exhibited significantly enhanced hepatoprotective activity, increasing SOD, CAT, and GSH-Px activities while reducing MDA and TG levels in HepG2 cells.

This study demonstrates that the hepatoprotective effect of GPS-1 depends on gut microbial fermentation. GPS-1 resists digestion but is degraded by the microbiota, enriching Bacteroides, boosting propionate and acetate production, and generating fermented products with enhanced antioxidant and lipid-lowering activity. These findings suggest that GPS-1 has potential as a prebiotic functional ingredient for improving intestinal health and regulating lipid metabolism.