The human intestinal mucosa covers an area of 200–300 square meters (equivalent to 3 football fields) and harbors 10 trillion different symbiotic microorganisms, collectively called the "gut microbiota."
Gut microbiota plays a crucial role in digestive function and influences the operation of other bodily systems and tissues. Its key functions include:
- Promoting food breakdown
- Synthesizing essential vitamins
- Removing toxic compounds
- Resisting pathogens
- Maintaining the integrity of the intestinal epithelial cell layer
- Regulating immune function
Impairment of the intestinal lining and imbalance of gut microbiota can lead to a range of metabolic diseases, such as obesity, type 2 diabetes, and non-alcoholic fatty liver disease.
Key Study Findings
Jiangsu University researchers divided mice into groups and supplemented them with different concentrations of NMN in drinking water for 15 consecutive weeks. The results confirmed NMN’s effects on gut health:
1. NMN Increases Gut Microbiota Species Richness
- NMN supplementation significantly raised NAD+ levels in mice in a concentration-dependent manner.
- It altered the composition of specific bacterial populations in the gut microbiota:
- Beneficial bacteria enrichment: Abundance of butyrate-producing bacteria (e.g., Ruminococcaceae, Akkermansia) increased—these bacteria are critical for intestinal health and significantly boost energy production in intestinal cells.
- Harmful bacteria reduction: Levels of harmful bacteria (e.g., Bilophila, Oscillibacter, Desulfovibrionaceae) decreased. Bilophila is associated with the development of infectious diseases such as sepsis and cholecystitis.
2. NMN Improves Intestinal Barrier Function
- Enhanced mucus barrier: NMN increased the mucus thickness of intestinal goblet cells. Mucins secreted by goblet cells form a barrier that prevents direct contact between external bacteria and the epithelial layer, while also serving as a nutrient source for gut bacteria.
- Reduced intestinal leakage: Mice treated with NMN showed much less compound leakage from the intestines, indicating NMN lowers intestinal mucosal permeability and maintains the integrity of the mucosal barrier.
- Boosted autophagy for barrier tightness: Intestinal barrier integrity is regulated by autophagy (which enhances the tightness of intercellular barriers to prevent nutrient loss). NMN strengthens autophagy, making intercellular barriers tighter and maintaining intestinal epithelial integrity.
Figure Note: NMN increases protein levels in intestinal wall cells (left) and improves the integrity of the intestinal mucosal lining (right, detected via FITC-Dextran/FD4/DAPI staining).
Research Significance & Outlook
The study confirms NMN enhances gut microbiota composition and improves intestinal lining integrity, laying a foundation for exploring intestinal health.
As gut microbiota research advances, NMN is expected to play a significant role in improving digestive function and combating intestinal diseases.
References
Huang, P., Jiang, A., Wang, X., Zhou, Y., Tang, W., Ren, C., Qian, X., Zhou, Z., Gong, A. (2021). NMN Maintains Intestinal Homeostasis by Regulating the Gut Microbiota. Frontiers in Nutrition, 8:714604. https://doi.org/10.3389/fnut.2021.714604