Digestion of Protein in Premature and Term Infants

Abstract

Premature birth rates and premature infant morbidity remain discouragingly high. Improving nourishment for these infants is the key for accelerating their development and decreasing disease risk. Dietary protein is essential for growth and development of infants. Studies on protein nourishment for premature infants have focused on protein requirements for catch-up growth, nitrogen balance, and digestive protease concentrations and activities. However, little is known about the processes and products of protein digestion in the premature infant. This review briefly summarizes the protein requirements of term and preterm infants, and the protein content of milk from women delivering preterm and at term. An in-depth review is presented of the current knowledge of term and preterm infant dietary protein digestion, including human milk protease and anti-protease concentrations; neonatal intestinal pH, and enzyme activities and concentrations; and protein fermentation by intestinal bacteria. The advantages and disadvantages of incomplete protein digestion as well as factors that increase resistance to proteolysis of particular proteins are discussed. In order to better understand protein digestion in preterm and term infants, future studies should examine protein and peptide fragment products of digestion in saliva, gastric, intestinal and fecal samples, as well as the effects of the gut micro biome on protein degradation. The confluence of new mass spectrometry technology and new bioinformatics programs will now allow thorough identification of the array of peptides produced in the infant as they are digested.

Endogenous Human Milk Peptide Release Is Greater after Preterm Birth than Term Birth

“…The preterm infant, compared with the term infant, is thought to be poorly equipped for the task of protein digestion (45,49). For example, a previous study showed that gastrointestinal trypsin activity is lower in preterm than term infants in early life (49).…”

“…Across lactation, a large number of functional peptides were present in both preterm and term milk with actions including antihypertensive, antimicrobial, and immunomodulatory. The release of these peptides is relevant because most milk peptides are inactive within the sequence of the intact parent protein, until they are released, and thus, activated by proteolytic enzymes (45). For example, during the digestion of highly phosphorylated b-caseins, phosphopeptides are formed.…”

Avances en el conocimiento de las proteínas de la leche materna

“…Por ejemplo, algunos de ellos participan en el organismo inmaduro en el desarrollo y la protección de su tubo digestivo, y en órganos extradigestivos de los recién nacidos 12,13 . La hidrólisis sucesiva de la β-caseína por la tripsina, la pepsina, la quimotripsina, la gama-glutamil endopeptidasa y probablemente otros enzimas, libera un péptido del que se origina una familia de cuatro componentes con fuerte actividad antimicrobiana; estos se caracterizan porque la cadena de aminoácidos de cada uno de ellos es, respectivamente, un aminoácido más corta que la del homólogo que la precede 12,14 . Es probable que las actividades antimicrobianas de algunos de los péptidos originados de la leche materna coincidan en sus actividades y se potencien entre si 15 .…”

Nutritional management of surgical newborns and infants in the acute phase and during follow up

“…Higher concentrations of hydrolysed proteins, mainly caseins, have been found in preterm milk relative to term milk. 25 Within this context, it must be considered that the industrial hydrolysis process may release peptides with unknown biological functions. 26 Some commercial formulas contain free amino acids rather than proteins or peptides; their use is generally well tolerated and has been associated with a shorter duration of parenteral nutrition and reduced risk of developing allergies.…”