Treatment of inflammatory bowel disease: Potential effect of NMN on intestinal barrier and gut microbiota

Abstract

Nicotinamide mononucleotide (NMN) exerts physiological effects in mammals through its conversion to nicotinamide adenine dinucleotide (NAD⁺). In this study, we established experimental models of colitis by mixing drinking water of C57BL/6J mice with dextran sodium sulphate (DSS), and then fed them with the same concentration of NMN or at the same time. After NMN treatment, we observed improved morphology of inflamed intestines, slightly restored length of colon, improved barrier function and reduced proinflammatory factors expression in serum. Also, significant alterations in the composition and abundance of intestinal flora in IBD mice were found. The abundance of Firmicutes, Verrucomicrobia, Akkermansia and Lactobacillus, considered as beneficial bacteria, increased, while Bacteroidetes and Muribaculaceae unclassifiably decreased. Taken together, these results suggest that NMN may improve intestinal inflammation, reduce intestinal mucosal permeability and repair gut flora dysbiosis in IBD.

Keywords: DSS; DSS, Dextran sodium sulphate; Gut microbiota; IBD; IBD, Inflammatory bowel disease; NAD+; NAD+, Nicotinamide adenine dinucleotide; NMN; NMN, Nicotinamide mononucleotide.

Graphical abstract

Fig. 1

The NMN effect on the body weight of mice, colon length of mice, concentration of NAD⁺ and occult blood in the feces with colitis. A: Concentration of NAD⁺ in mice in all the groups. N+D vs. DSS (P = 0.0079); D + N vs. DSS (P = 0.0159). B: The body weight of mice in all the groups during NMN administration period. C: Rate of weight loss in mice in all the groups during the administration period. D–G: Serum concentrations of IL4, IL-6. IL-10 and TNF-α in colitis mice before and after NMN treatment, E: CON vs. DSS (P = 0.0286), F: CON vs. DSS (P = 0.00760), N + D vs. DSS (P = 0.0357), D + N vs. DSS (P = 0.0357), G: CON vs. DSS (P = 0.0043), N + D vs. DSS (P = 0.0079), D + N vs. DSS (P = 0.0159). H–I: The NMN effect on the colon length of mice with colitis. CON vs. DSS (P = 0.0061); D + N vs. DSS (P = 0.0095). J: Occult blood in the feces of the mice during modeling. P = 0.0047. *:0.01<P < 0.05, **:0.001<P < 0.01 and ***:P < 0.001.

Fig. 2

The effect of NMN on the intestinal mucosal barrier. A: HE staining of colon in mice of CON, DSS, N + D and D + N groups, bar = 200 μm. B: Alcian Blue staining of intestinal mucosal in mice of CON, DSS, N + D and D + N groups, bar = 200 μm. C: Tight-junction proteins' expression (claudin-1, E-Ca and Occluding) in colon with IHC. bar = 200 μm. D-F The quantitative of the proteins. D: CON vs. DSS (P = 0.0480). E: CON vs. DSS (P = 0.0118), DSS vs. N + D (P = 0.0170), DSS vs. D + N (P = 0.0135). F: CON vs. DSS (P = 0.0482). *:0.01<P < 0.05, **:0.001<P < 0.01 and ***:P < 0.001. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

A–B: The effect of NMN on intestinal mucosa permeability. A: The in vivo imaging in different mice groups; B: The concentration of serum FD4 in different mice groups. *:P < 0.05, **:P < 0.01 and ***:P < 0.001.

Fig. 4

A: Chao1 index, B: goods _coverage index, C: Observed_otus index, D: Shannon index, E: Principal component analysis (PCA) and F: Principal coordinates analysis (PCoA) *:P < 0.05.

Fig. 5

A: Cluster analysis-phylum, B: Cluster analysis-genus, C: Relative abundance at phylum level, D: Relative abundance at genus level, E: Distribution of intestinal dominant flora-phylum, F: The distribution of intestinal dominant flora-genus, G: Heatmap at phylum level and H: Heatmap at genus level.

Fig. 6

A–B: Differential analysis of intestinal microbiota of mice at phylum and genus levels, C: LDA of discriminative biomarkers and D: LEfSe cladogram of intestinal flora. *:P < 0.05, **:P < 0.01 and ***:P < 0.001.