The effects of niacin status on NAD levels in relation to memory and learning in guinea pigs and rats
Niacin deficiency in humans causes the disease pellagra, characterized, in part, by dementia. We hypothesized that niacin deficiency will affect learning through depletion of substrate (NAD+) required for synthesis of cADPr and NAADP. To explore this we (1) determined the effect of niacin deficiency and supplementation on NAD+ levels; (2) studied the effects of niacin deficiency and supplementation on Morris water maze (MWM) performance. Guinea pigs were fed 25%, 20%, 15%, 10% casein niacin deficient (ND) or pair fed (PF) (50 mg/kg) diets. Guinea pigs were resistant to ND with no differences in MWM. Rats were fed a 5% casein/8% gelatin or 6% casein/7% gelatin ND or PF diets (30mg/kg). The 5% casein/8% gelatin produced the best ND model with no differences in MWM. Niacin supplementation caused significantly higher NAD+ levels and differences in MWM. Supplementation of niacin in disease treatment supports further research on NAD+ status in learning.