RESPONSES OF GASTROINTESTINAL PEPTIDES AND MOTOR-ACTIVITY TO MILK AND WATER FEEDINGS IN PRETERM AND TERM INFANTS

Because duodenal motor activity differs between preterm and term infants during fasting, this study evaluated the responses of motor activity and peptide release in response to feeding. In the first study, fasting concentrations of gastrin, gastric inhibitory peptide, neurotensin, and peptide YY (PYY) were determined in 53 preterm and 20 term infants. Plasma concentrations of gastrin and neurotensin were significantly lower in preterm infants than in healthy adults reported previously by our lab (p < 0.01). Plasma concentration of gastric inhibitory peptide and PYY were higher than in healthy adults (p < 0.01). Gastrin concentrations in preterm and term infants varied directly with gestational age (p < 0.005); PYY varied inversely with gestational age (p < 0.005). In a secondary study, intestinal manometry was recorded and serial peptide concentrations were determined in 43 preterm babies who were given their first enteral feeding intraduodenally with formula or sterile water. Although none of the four peptide plasma concentrations changed in response to feeding with water, plasma concentrations of gastric inhibitory peptide, neurotensin, and PYY significantly increased with formula feedings (p < 0.05 or less). In addition, plasma gastrin increased significantly in seven infants fed milk compared with eight fed water by orogastric tube (p < 0.01). In contrast to the peptide response to feeding, motor activity changed in response to feeding with either water or milk; motility indices increased and periods of motor quiescence decreased significantly during feeding as compared with fasting (p < 0.02). Responses of both motor activity and peptides to feeding were time related. Although fasting concentrations of four regulatory peptides were immature in preterm infants compared with adults, postprandial responses to nutrient feedings were present in the first days of life. This discrepancy in functional maturation of the preterm intestine during fasting and feeding is present for both motor activity and peptide response, and we speculate that the controlling mechanisms of these two phases of digestion may mature independently at different postconceptual ages.