INTRAGASTRIC TRYPTOPHAN REDUCES GLYCEMIA AFTER GLUCOSE, POSSIBLY VIA GLUCOSE-MEDIATED INSULINOTROPIC POLYPEPTIDE, IN EARLY-WEANED PIGLETS

The aim of this experiment was to investigate the influence of oral tr yptophan on insulin, glucose-mediated insulinotropic polypeptide and g lucose concentrations in early-weaned piglets. Piglets were given by i ntragastric infusion, at the same level of feeding, either a tryptopha n-deficient or tryptophan-adequate diet for 22 d. During the experimen t blood samples were taken after intragastric infusion of 1) the accus tomed meal, 2) a glucose plus tryptophan load and 3) a glucose load. P lasma samples were analyzed for insulin, glucose-mediated insulinotrop ic polypeptide, glucose and lactate. After the accustomed meal plasma insulin concentrations were augmented and liquid gastric emptying fast er in pigs fed tryptophan-adequate compared with tryptophan-deficient diets (P < 0.05) but glucose-mediated insulinotcopic polypeptide, gluc ose and lactate were unaffected. The addition of tryptophan to a gluco se load increased glucose-mediated insulinotropic polypeptide and redu ced glucose in both tryptophan-adequate and tryptophan-deficient diet fed pigs (P < 0.05). Piglets adapted to the tryptophan-adequate diet h ad a greater glucose-mediated insulinotropic polypeptide response to i ntragastric glucose plus tryptophan than piglets adapted to the trypto phan-deficient diet. Adaptation to a tryptophan-adequate diet seems to increase the release of glucose-mediated insulinotropic polypeptide d ue to infusion of a tryptophan-adequate compared with a tryptophan-def icient diet. The addition of tryptophan to a glucose load reduces the level of glycemia, possibly through glucose-mediated insulinotropic po lypeptide-mediated glucose disposal.