RESUMO
Tryptophan (Trp) is usually catabolized to CO2, H2O and urea in mammals. Quantitatively, minor branches from this pathway lead to the production of picolinate (PA) and NAD+. Although niacin is a required nutrient when NAD+ synthesis from Trp is insufficient, it is not known if dietary PA is beneficial in such conditions. Two kinds of experiment were used to investigate the effects of dietary PA. First, mice were fed on a diet deficient in Trp for six weeks to diminish endogenous PA synthesis and stores. After this time the body mass of the mice was reduced by approximately 30%. Tryptophan-deficient mice subsequently fed a nutritionally complete diet gained weight more rapidly during the first but not subsequent week(s) of recovery when PA was added to their food. Second, mice were fed on a diet deficient in Trp, niacin and vitamin B-6 during the preimplantation period of pregnancy in an attempt to acutely lower PA synthesis and perhaps alter the embryos thus produced. The rate at which preimplantation blastocysts formed trophoblastic outgrowths when cultured in vitro was stimulated by dietary PA only if these blastocysts came from mice fed on a nutritionally deficient diet. The results suggest that PA serves as a beneficial nutrient under some conditions where its endogenous synthesis may be diminished.