Weanling male Long-Evans rats were fed niacin deficient (ND) or niacin replete (pair-fed control, PF) (30 mg nicotinic acid/kg) diet for 3 weeks. After 2 weeks of feeding, pairs of ND and PF rats were randomly assigned to receive oral etoposide (40mg/kg body weight) (ETO) or soy oil vehicle (V) for 7 consecutive days while remaining on their ND or PF diet. Three hours following the last dose of etoposide or vehicle, rats were euthanised and bone marrow and blood collected. Niacin deficiency alone caused an 80% decrease in bone marrow NAD+ relative to PF rats: surprisingly, ETO treatment of ND rats caused a 3.0 fold increase in the NAD+ status of the bone marrow. In PF-ETO rats there was also an NAD+ response, with a 1.25 fold increase over PF-V rats. Blood NAD+ did not differ between PF-V and PF-ETO rats, but was increased 1.5 fold in ND-ETO vs. ND-V. Telomere length in ND-V rats was found to be decreased by 10% relative to PF-V rats (p

Keywords: niacin, Telomere, Etoposide, NAD+