In these same mice, Hong and colleagues injected 500 mg/kg of NMN or saline three times per week. NMN treatment alleviated bodyweight reduction and colitis severity, resulting in a better survival rate. In detail, saline injection resulted in 33% survival (4/12 mice), whereas NMN administration resulted in 67% survival (8/12 mice). Consistently, NMN treatment increased the number of cells in a replicative state while decreasing cell death markers and reducing macrophage infiltration. These results show that NMN administration protects mice from colitis by enhancing the resolution of inflammation.
Next, Hong and colleagues examined whether any toxic side effects accompanied by NMN injection may present in mice. No gross and microscopic abnormalities were observed in the colon, liver, or spleen, and the serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were not increased upon NMN treatment, indicating that NMN injection could attenuate colitis without obvious liver toxicity.