In vivo digestion of infant formula in piglets: protein digestion kinetics and release of bioactive peptides

Abstract

The first months of life correspond to a key period in human life where dramatic physiological changes (establishment of microbiota, development of the immune system, etc.) occur. In order to better control these changes it is necessary to understand the behaviour of food in the gastrointestinal tract of the newborn. Infant formula is the only food for the newborn when breast-feeding is impossible. The kinetics of digestion of milk proteins and the nature of the peptides liberated in the small intestine throughout infant formula digestion have never been extensively investigated so far and were therefore studied using the piglet as a model of the newborn child. Piglets were fed infant formula by an automatic delivery system during 28 d, and slaughtered 30, 90 and 210 min after the last meal. Contents of stomach, proximal and median jejunum and ileum were collected and characterised. The extent of b-lactoglobulin (b-lg), a-lactalbumin (a-la) and casein proteolysis was monitored by inhibition ELISA, SDS-PAGE, immunoblotting and MS. At 30 min after the last meal, caseins were shown to be extensively hydrolysed in the stomach. Nevertheless, peptides originating mainly from b-caseins (from 509 to 2510 Da) were identified in the jejunum and ileum of the piglets. b-Lg partially resisted gastric digestion but completely disappeared in the stomach after 210 min. a-La had a similar behaviour to that of b-lg. Two large peptides (4276 and 2674 Da) generated from b-lg were present in the ileum after 30 and 210 min and only one (2674 Da) after 90 min.Key words: Digestion: Milk proteins: Piglets: Infant formula Protein digestion is a complex process resulting in the concerted action of digestive enzymes on dietary proteins and depending on many factors such as the type of dietary proteins, gastric and intestinal pH, peptic activity, endogenous secretions, and motility.Major differences in the composition of breast milk and infant formula (protein content, lipids, lactose, growth factors, immunoglobulins, enzymes, etc.) can make the way proteins are digested by the newborn different and can therefore modulate the physiology of the gut (1) . Although studies have been performed on different aspects of digestion (metabolism, gastric emptying, protein flow, etc.), there is very limited information in the literature on protein digestion in the infant. During the neonatal period, the gastric hydrolysis of milk proteins by pepsin is limited due to the buffering capacity of milk that increases the pH, thus limiting the activity of this acid protease (2) . Gastric emptying was shown to be faster with human milk than with casein-based formula-and cows' milk-fed children (3,4) . However, identical gastric emptying was found in preterm infants fed either a soluble milk protein (SMP)-predominant (caseins:SMP ratio 40:60) or a casein-predominant (caseins:SMP ratio 82:18) formula, the amount of all other nutrients and osmolality being similar (5) . Several studies have been conducted in vitro on the digestion of milk proteins using v...

Towards infant formula biomimetic of human milk structure and digestive behaviour

“…Though several pertinent static in vitro digestion models mimicking the infant digestive conditions have been proposed (Dupont et al, 2010;Bouzerzour et al, 2012;Bourlieu et al, 2014;Levi et al, in press), very few studies have investigated the behaviour of HM during static in vitro digestion. Most digestion models were employed to evaluate IF digestion (Lueamsaisuk et al, 2014).…”

The DIDGI® System

“…The dynamic digestive system was set up using parameters taken from the literature that are listed in Table 8.1. The pH curve in the stomach was obtained by combining data from different in vivo experiments on piglets (Moughan et al 1991;Chiang et al 2008;Bouzerzour et al 2012) whereas intestinal pH was kept constant at 6.5. Other parameters like the transit time of the formula in the stomach (determination of t 1/2 and β) was obtained from an exhaustive review on human infant gastrointestinal physiological conditions (Bourlieu et al 2014) and fixed at t 1/2 = 70 min or 200 min and β = 1.23 or 2.2 for gastric or intestinal transit time, respectively.…”

“…Other parameters like the transit time of the formula in the stomach (determination of t 1/2 and β) was obtained from an exhaustive review on human infant gastrointestinal physiological conditions (Bourlieu et al 2014) and fixed at t 1/2 = 70 min or 200 min and β = 1.23 or 2.2 for gastric or intestinal transit time, respectively. Volumes, flow rates of secretions, nature and quantity of enzymes in the different stages of the gastro-intestinal model have been described previously (Minekus et al 1995;Blanquet et al 2004;Bouzerzour et al 2012) based on results of in vivo experiments. Digestive enzymes and bile were diluted in 150 mM NaCl, pH 6.5.…”

“…Eighteen piglets [Pietrain × (Large White × Landrace)] were separated from their mothers after 2 days and fed for 26 days with the formula using an automatic milk feeder, as described previously (Bouzerzour et al 2012). The experimental design was a complete block design with 1 × 3 factorial arrangement of 1 diet and 3 slaughter times after the last meal (30 min, 90 min and 210 min).…”

Biodisponibilidade de peptídeos do feijão caupi (Vigna unguiculata L.Walp) e o metabolismo do colesterol

“…Já a absorção dos di e tripeptídeos ocorre pelo PEPT1 (Proton-dependent peptide transporter 1) (DEAN e MA, 2007;GILBERT et al, 2008;SEGURA-CAMPOS et al, 2011;BOUZERZOUR et al, 2012;FURUTANI et al, 2013;SPANIER, 2014).…”