Nicotinamide Mononucleotide Administration Amends Protein Acetylome of Aged Mouse Liver

It is known that the activities of nicotine adenine dinucleotide (NAD(+))-dependent deacetylase decline in the aging mouse liver, and nicotinamide mononucleotide (NMN)-mediated activation of deacetylase has been shown to increase healthspans. However, age-induced changes of the acetylomic landscape and effects of NMN treatment on protein acetylation have not been reported. Here, we performed immunoprecipitation coupled with label-free quantitative LC-MS/MS (IPMS) to identify the acetylome and investigate the effects of aging and NMN on liver protein acetylation. In total, 7773 acetylated peptides assigned to 1997 proteins were commonly identified from young and aged livers treated with vehicle or NMN. The major biological processes associated with proteins exhibiting increased acetylation from aged livers were oxidation-reduction and metabolic processes. Proteins with decreased acetylation from aged livers mostly participated in transport and translation processes. Furthermore, NMN treatment inhibited the aging-related increase of acetylation on proteins regulating fatty acid beta oxidation, the tricarboxylic acid (TCA) cycle and valine degradation. In particular, NAD (P) transhydrogenase (NNT) was markedly hyperacetylated at K70 in aged livers, and NMN treatment decreased acetylation intensity without altering protein levels. Acetylation at cytochrome 3a25 (Cyp3a25) at K141 was also greatly increased in aged livers, and NMN treatment totally arrested this increase. Our extensive identification and analysis provide novel insight and potential targets to combat aging and aging-related functional decline.

Automated summary

It has been reported that the activities of NAD(+)-dependent deacetylase decrease in the aging mouse liver, while NMN treatment can increase healthspans. However, the changes in the acetylomic landscape and the effects of NMN treatment on protein acetylation in the aging liver have not been studied. In this study, immunoprecipitation coupled with label-free quantitative LC-MS/MS was used to identify the acetylome and investigate the effects of aging and NMN on liver protein acetylation. The results showed that the acetylation levels of proteins involved in oxidation-reduction and metabolic processes increased in aged livers, while the acetylation levels of proteins involved in transport and translation processes decreased. NMN treatment inhibited the age-related increase in acetylation of proteins regulating fatty acid beta oxidation, the TCA cycle and valine degradation.