Possible molecular mechanisms and role of NAD⁺ precursors in restoring hematopoietic stem cell (HSC) function. Aged HSC function might be recovered through increasing mitochondrial function using NAD⁺ precursors.

Abbreviations: AMPK, 5′ adenosine monophosphate-activated protein kinase; NAMPT, nicotinamide phosphoribosyltransferase; FOXO, forkhead box protein; SIRT1, sirtuin 1; Sir2, silent information regulator 2; NR, nicotinamide riboside; cADP, cyclic ADP; Nam, nicotinamide; Trp, tryptophan; Na, nicotinic acid; Na ADP, nicotinic ADP.