NNT and Impaired glucose tolerance: The C57BL/6JRccHsd mouse strain in our study contains a functional nicotinamide nucleotide transhydrogenase (Nnt) gene, whereas the C57BL/6J model that was used in the studies showing beneficial effects of high-dose NR supplementation harbors a spontaneous mutation in Nnt, which has been described to be responsible for an impaired glucose tolerance and decreased insulin secretion in this model [52,53].