(A) RNA expression in the heart of WT and p32cKO mice subjected to NMN treatment from 2 to 9 mo of age (WT, p32cKO, and p32cKO + NMN: n = 5, WT + NMN: n = 6). Data are presented as the mean ± SD. (B) Amino acid metabolism analysis of NMN-treated mice. LC-MS/MS metabolomic analysis of amino acids was performed in 9-mo-old WT and p32cKO mice and mice supplemented with NMN from 2 to 9 mo of age (WT, p32cKO, and p32cKO + NMN: n = 5, WT + NMN: n = 6). Amino acids are significantly different between p32cKO and p32cKO + NMN. Data are presented as the mean ± SEM. (C) Autofluorescence showing lipofuscin localization around the nucleus as dots per cell in the heart of WT and p32cKO mice, and in p32cKO mice treated with NMN from 2 to 10 mo of age. Tissues were excited at a wavelength of 540 nm (upper panel) or 470 nm (lower panel), and emission spectra were collected with a confocal microscope at wavelengths (band path) of 580–630 nm (right panel) or 510–560 nm (left panel). Scale bars, 20 μm. Quantification of the ratio of autofluorescent blots per DAPI-staining area is shown in the lower panel as the mean ± SD (n = 4). Arrows indicate intracellular aggregation of lipofuscin.