Effects of chronic parenteral pyridoxine and acute enteric tryptophan on pyridoxine status, glycemia and insulinemia stimulated by enteric glucose in weanling piglets
In order to investigate the importance of the relation between pyridoxine and tryptophan on glucose tolerance and insulin response to glucose, 12 Large White × Pietrain piglets (males and females), weaned at 3 wk of age, were allocated to two treatment groups. Within each of the six pairs (four females and two males), one piglet received daily 3 mL i.m. of pyridoxine.HCl (5 g L−1) and the other received a control injection of saline. The animals were fed a liquid feed through a gastric tube surgically inserted on the day of weaning. Seven days later, one catheter was placed in the duodenum and another in the jugular vein. One week after recovery, the piglets received an intraduodenal infusion of glucose or glucose + tryptophan; 2 d later, each piglet received the opposite treatment. There was no effect (P > 0.18) of the administration of pyridoxine.HCl on plasma pyridoxal and pyridoxal-5-phosphate. Whatever the pyridoxine treatment, the plasma glucose response was lower (P ≤ 0.05) after the glucose + tryptophan infusion than after the glucose infusion. There was, also, an interaction between parenteral pyridoxine and duodenal infusion on changes in plasma insulin concentrations following the duodenal infusion (P ≤ 0.02). The greatest response, observed in piglets supplemented with pyridoxine.HCl and infused with glucose, was 55% higher than for the three other treatments. Further work is needed for an eventual reliable estimate of the pyridoxine status and requirements of weanling piglets. The tryptophan and pyridoxine effects on insulin metabolism suggest a different action of these nutrients on sensitivity and release of insulin. Key words: Pyridoxine, tryptophan, glucose, insulin, weanling piglets