Summary14); however, its relationship to diet has been explored only to a Small intestinal development was followed in rats from 17 to 28 days of age in order to evaluate the interactions of diets, genetic preprogramming, and hormones in influencing developmental changes. Control pups, weaned naturally at 21-24 days, showed a gradual increase in body weight, intestinal length, and segmental mucosal weight, total DNA, and protein content. In contrast, pups weaned at 17 days showed an immediate increase in intestinal length, decrease in lactase, and precocious increase in sucrase and maltase. The changes in segmental mucosal weight, DNA and protein contents, however, paralleled that of controls. Pups nursed "p to 25 days had a smalle; body weight, shorter intestine, lighter mucosa, and lesser mucosal protein content. They showed no significant delay in the increase in sucrase and maltase together with a persistent higher level of lactase. Enterokinase and leucine aminopeptidase showed little change irrespective of the dietary modifications. Significant increases in segmental mucosal mass, DNA, and protein contents during the studied period were seen in all animals. At 19 days, early weaned pups had serum levels of corticosteroids about 3 times that of control or prolonged nursed pups. The results support the concept of an inherent biologic program as a basic control of intestinal ontogeny whereas dietary changes seem to have a modifying role and act directly, or in concert with, hormonal changes.Neonatal rats have no detectable sucrase, low maltase, and high levels of lactase activities in their small intestines. The activities of sucrase and maltase increase abruptly about the 15th day of age. These two enzymes continue to rise during the third and fourth week with a concomitant decrease in lactase. The third week of life in rats corresponds to the weaning time that is marked by a shift from a fat-rich diet supplied by the mother (4) to a carbohydrate-rich lab-chow diet. The carbohydrate is also changed from an almost exclusive lactose-containing milk to a predominant glucose-polymer-and sucrose-containing chow. A casual relationship exists therefore between dietary changes and the increase in sucrase and maltase with a corresponding decrease in lactase. The possibility of a "dietary influence" of enzymes is further strengthened by the observations that sucrase rises precociously by early feeding of sucrose (15,21). In addition, we have shown (16) that prolonged nursing leads to a slower decline in lactase activity. At 25 days of age, prolonged nursed rats show similar maltase and sucrase activities as control weaned rats. Similar studies by Henning and Guerin (20) also showed no depression in sucrase activities when pups were weaned onto a special diet with lactose as the sole source of carbohydrate. These results are in agreement with those studies using intestinal explants (8,11) or in vitro cultures ( 6 ) and together suggest that the postnatal increase in sucrase and maltase in the rat is preprogrammed. Othe...
SummaryThirty-one premature infants who required nasojejunal feeding were evaluated for pancreatic exocrine function before and after feeding of milk-based or soy-based formulas for 30 days. The two groups were well matched for age and birth weight (about 1.5 kg). At birth, all infants had high basal secretion of trypsin and chymotrypsin, but low lipase and no amylase activity. Additionally, there was no response to pancreozymin (CCK). After 30 days of feeding with either soy or milk-based formulas, both groups showed a similar increase in body weight (to 1.8 kg) and basal secretion of trypsin, chymotrypsin, and lipase and failure to secrete amylase. The group that was fed milk-based formula failed to respond to CCK and secretin administration. Thus, soy-and milk-based formulas result in similar weight gain and similar basal pancreatic enzyme secretion while feeding with soy-based formula selectively increases the trypsin and lipase response to CCK. SpeculationAdaptation of pancreatic exocrine function to dietary modifications has been shown in adults. Such adaptation may also exist in neonates. Feeding of two contrasting formulas, soy and milk based, may affect the development and maturation of the exocrine pancreatic function differently.In comparison to adults, newborn term and preterm infants suffer a state of digestive insufficiency. Newborns have a less developed pattern of exocrine pancreatic function which is characterized by very low lipase and absence of amylase activities in the duodenal contents (2,4,8,13,26).Premature infants (32 to 34 wk of gestation) absorb only 65 to 75% of the lipid intake. Full-term newborns absorb 85 to 90% of the lipid intake, and adult levels of lipid absorption are not attained until 4 to 6 months of age (12,20). Thus, varying degrees of "steatorrhea" can be found in young infants. Starch digestion has not been studied in prematures; however, as measured by the carbohydrate content and composition in the intestinal juice after feeding of a test meal containing amylopectin, infants 3 to 6 months of age suffer diminished starch digestion when compared to children older than 1 year (1). In contrast, both premature and full-term neonates have been found to effectively absorb proteins (2).Knowledge of the level of pancreatic enzymes in premature infants is scanty (10). In the study by Borgstrom et a1 (2), premature infants around 1 wk of age were found to have a decreased concentration of trypsin in basal duodenal fluid and a failure of pancreatic response to feeding when compared with infants 14 to 30 days of age. Zoppi et al. (26) found no difference in trypsin activity between premature neonates and full-term neonates. However, very low activities of lipase and alpha-amylase were noted in premature neonates.In animals, pancreatic enzymes have been shown to be influenced by diet. Diets high in carbohydrate content were found to selectively increase the pancreatic content of amylase in rats (5, 23), whereas diets high in protein were shown to result in high trypsin and chymotry...
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