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[Nutrition of premature infants below 1,500 g: enteral prerequisites]
Insights
The human fetal gastrointestinal tract develops early, with key digestive enzymes like lipase and proteases becoming active around the 24th week of gestation. Premature infants under 1500g possess a functional system for digesting lipids, proteins, and carbohydrates.
Area of Science:
- Fetal development
- Gastrointestinal physiology
- Digestive enzyme activity
Context:
- Human fetal gastrointestinal tract development occurs early in gestation.
- Pancreatic exocrine enzyme secretion begins around the 24th week, with exceptions like amylase.
- Small intestine development includes morphological and functional maturation by the 10th week.
Purpose:
- To detail the developmental timeline of the human fetal gastrointestinal tract.
- To identify the onset of specific digestive enzyme activities during gestation.
- To assess the digestive and absorptive capabilities of premature infants.
Summary:
- Pancreatic enzymes (trypsinogen, lipase, colipase) are secreted starting at 24 weeks gestation.
- Intestinal enzyme activities (sucrase-isomaltase, maltase-glucoamylase, lactase, peptidases) are detected from 11-12 weeks, reaching sufficient levels by 25 weeks, except for lactase.
- Premature infants (<1500g) have a well-equipped GI tract for digesting lipids, carbohydrates, and proteins via multiple lipase, carbohydrase, and peptidase activities.
Impact:
- Provides a timeline for fetal digestive system maturation.
- Highlights the functional capacity of premature infants' gastrointestinal tracts.
- Informs clinical nutrition strategies for preterm neonates.
Abstract:
The development of the human fetal gastrointestinal tract takes place early during gestation. The pancreas although developed by morphological means at the 16th week of gestation excretes its exocrine enzymes later at the 24th week of gestation except for amylase which reaches its full activity 6 months after birth. Trypsinogen secreted at the 24th week is activated into trypsin by enterokinase at the 26th week of gestation whereas lipase and colipase are secreted from the 24th week. The small intestine starts developing at the 10th week morphologically and functionally. At the same time when villi and crypts start to develop at the 11th to 12th week the first enzyme activities can be detected, i.e. sucrase-isomaltase, maltase-glucoamylase and lactase. Also peptidases and lysosomal hydrolases are measured at this age. With the exception of lactase, intestinal enzymes reach sufficient activities at the 25th week of gestation. Lactase activity remains low until the 32nd-34th week. For the digestion and absorption of lipids, protein and carbohydrates the gastrointestinal tract of premature infants under 1500 g in rather well equipped. Lipids are hydrolysed by the mutual action of breast milk lipase, lingual lipase, gastric lipase and pancreatic lipase. The carbohydrates lactose and oligosaccharides as supplements to breast milk are hydrolysed by lactase, sucrase-isomaltase and maltase-glucoamylase. Breast milk proteins and cows milk hydrolysates are digested by pancreatic proteases into oligopeptides which can be hydrolysed within the lumen by brush border peptidases and be absorbed. Peptides also can actively be transported through the microvillus membrane and be hydrolyzed by intracellular peptidases.(ABSTRACT TRUNCATED AT 250 WORDS)