Development of Functional Response in Human Exocrine Pancreas

Abstract

The ability of newborns to digest proteins, fats, and carbohydrates depends, to a large extent, on their level of exocrine pancreatic function. Building on the limited published data, we studied pancreatic enzyme activities in the duodenal fluid and the response of the exocrine pancreas to secretogogues in 15 premature and full-term infants at birth and at 30 days of age. We compared these findings to those obtained from identical studies of 17 children age 2 years and above. In addition, we measured the pancreatic exopeptidase, carboxypeptidase B, in relation to other pancreatic enzymes. The duodenal fluid of newborns and infants contained no amylase and negligible lipase. Carboxypeptidase B levels were also low compared to those in the older children. In contrast, chymotrypsin activity in infants was about 50% to 60% of level found in the older children. Trypsin activity, the highest of all enzymes measured, was about the same in both newborns and older children, with a transient increase at 30 days. Administration of pancreozymin had no effect on pancreatic enzymes in the duodenal fluid of newborns and a slight effect on 1-month-old infants. But by age 2 years, a full response of the pancreas to pancreozymin was evident. In infants and newborns, responses to secretin were poor. Thus, the secretory response of the human pancreas to secretogogues, absent or minimal at birth, is acquired during the postnatal period.

Alpha‐Amylase Inhibits Cell Proliferation and Glucose Uptake in Human Neuroblastoma Cell Lines

“…The levels of α -amylase activity observed in breast milk (about 9-10 kU/l) and in the postprandial duodenal aspirates of infants (about 5 kU/l) are high considering the absence of starch in the infants' diet [ 33 – 37 ], but they are significantly lower when compared to those found in the duodenal lumen of healthy adults [ 38 ]. One should remember that preprandial duodenal fluid samples in healthy term newborns do not contain any amylase at least during the first month of life [ 39 ], and in fact, all healthy term newborns which are not breastfed are exocrine pancreatic insufficient [ 40 ]. Thus, the mothers' milk seems to be an important source of α -amylase, which can enter the circulation and may affect NB development or have some other yet unknown functions unrelated to carbohydrate digestion.…”

Development of the human pancreas and its exocrine function

“…Neonates from 32 weeks gestation to term appear to have 90% to 100% of trypsin levels of children 2 years of age. On the other hand, levels of chymotrypsin is 50-60% and while carboxypeptidase B is 10-25% the level of 2-year-old children, thus showing the development of protease levels over time ( Table 1 ) ( 29 ).…”

“…The mRNA encoding PLRP1 and PLRP2 was present by the 16th week in the human fetal pancreas. In contrast, the mRNA encoding PTL is limited in the fetal pancreas ( 29 ), and likely does not start increasing until 41 weeks gestation ( 24 ).…”

“…However, a high protein and low-fat diet stimulates both trypsin and PTL activity ( 36 ). After 12 months of age, PTL does appear to be stimulated over baseline activity by meals ( 29 ). It may therefore be possible that CCK and secretin more effectively stimulate exocrine function closer to 12 months of age.…”

Necrotizing enterocolitis, pathogenesis and the protector effect of prenatal corticosteroids

“…The immaturity of the gastrointestinal mucosal barrier can be demonstrated by: 1) Increased permeability of intestinal mucosal to intact proteins [57][58][59][60][61] ; 2) Reduced gastric acid secretion during the first week of life 62 ; 3) Reduced concentration of proteolytic pancreatic enzymes 63,64 , enterokinase 6 , and disaccharidase and lactase 66 ; 4) Immaturity of gastrointestinal motor activity 66,67 ; 5) A molar ratio of carbohydrate-toprotein that is less in the newborn mucus (The total protein content in intestinal mucus from newborn rat is greater than in adult mucus. 68 ); 6) Structural modifications of intestinal microvilli; and 69 7) Cellular and humoral gastrointestinal immaturity 70,71 .…”