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-The aim of this study was to compare the digestion of milk proteins from different species using an in vitro gastrointestinal model. Raw and heated milks from bovine, caprine, human and equine species were digested by human digestive enzymes. Digestion was performed in two 30-min sequential steps by digestive juices from the stomach (pH 2.5/37°C) and from the duodenum (pH 8.0/37°C). The degradation patterns of the milk proteins were visualized by SDS-PAGE and quantified using the ImageQuant program. Caseins in the equine milk were rapidly digested by the gastric juice in contrast to the caseins from the other species. During the subsequent digestion by the duodenal juice most of the caseins from all species were degraded within 5 min, and within 30 min only traces of caseins were detected. The mean casein micellar size varied between species in the range of 146.0-311.5 nm (equine > caprine > bovine > human). The α-lactalbumin from all species appeared to be very resistant to both gastric and duodenal digestions. A similar trend was shown for β-lactoglobulin from bovine and caprine milks, of which~60% intact protein remained, while only 25% remained intact in equine milk after total digestion. Equine milk contained a high amount of lysozyme, of which 60% remained intact in the present study. In heated milks from all species, only α-lactalbumin degradation increased approximately 12-20% in comparison to the raw milk. This study shows that equine milk with fast digestible proteins could be considered as a replacement for bovine milk in the diet of people with special needs, such as infants and the elderly. equine milk / bovine milk / caprine milk / human milk / digestion / whey protein / casein Résumé -Comparaison de la digestion des caséines et des protéines de lactosérum du lait équin, bovin, caprin et humain par les enzymes gastro-intestinales humaines. Le but de cette étude était de comparer la digestion des protéines laitières provenant de différentes espèces en utilisant un modèle gastro-intestinal in vitro. Des laits crus et traités thermiquement des espèces bovines, caprines, équines et humaines ont été digérés par des enzymes digestives humaines. La digestion a été réalisée au cours de deux étapes séquentielles de 30 min par des sucs digestifs gastriques (pH 2,5/37°C) et duodénaux (pH 8,0/37°C). Les profils de dégradation des protéines laitières ont été visualisés par SDS-PAGE et quantifiés à l'aide du programme ImageQuant. Les caséines du lait équin étaient rapidement digérées par le suc gastrique contrairement aux caséines des autres espèces. Au cours de la digestion suivante par le suc duodénal, la plupart des caséines de toutes les espèces étaient dégradées en 5 min, et après 30 min seules des traces des caséines étaient détectées. La taille moyenne des micelles de caséines variait de 146,0 à 311,5 nm selon les espèces (équin > caprin > bovin > humain). L'α-lactalbumine de toutes les espèces apparaissait être très résistante à la fois à la digestion gastrique et duodénale. Une tendance simila...

The objective of this study was to investigate the effects of high and low inhibitor soybean meals on the duodenal enzyme activities and on the possible regulatory role of gastrointestinal hormones in the pancreatic response. After an overnight fast, 11 healthy volunteers received an intraduodenal infusion of saline for 60 min. This was followed by infusion of either of three test meals: extract of raw soybeans (RS), a low inhibitor soy protein isolate (SPI) or bovine serum albumin (BSA), 10 g/h for 60 min. Then saline was again given intraduodenally for 30 min. Gastric juice was collected continuously and duodenal juice and peripheral blood samples were collected every 10 min. Duodenal chymotryptic activity was severely inhibited by RS, whereas SPI and BSA increased the chymotryptic activity. Tryptic activity showed a transient reduction (55%) during RS infusion, whereas BSA and in particular SPI increased the tryptic activity. No change was seen in amylase activity. The lack of total inhibition of tryptic activity has been studied further and is the subject of the accompanying paper. The peripheral plasma levels of cholecystokinin (CCK) increased significantly during BSA but not during SPI or RS infusions. Thus, CCK levels were not increased by the inhibition of the proteolytic activity by RS in duodenal juice.

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The aim of this study was to characterise the individual human gastric and duodenal juices to be used in in vitro model digestion and to examine the storage stability of the enzymes. Gastroduodenal juices were aspirated, and individual variations in enzymatic activities as well as total volumes, pH, bile acids, protein and bilirubin concentrations were recorded. Individual pepsin activity in the gastric juice varied by a factor of 10, while individual total proteolytic activity in the duodenal juice varied by a factor of 5. The duodenal amylase activity varied from 0 to 52.6 U/ml, and the bile acid concentration varied from 0.9 to 4.5 mM. Pooled gastric and duodenal juices from 18 volunteers were characterised according to pepsin activity (26.7 U/ml), total proteolytic activity (14.8 U/ml), lipase activity (951.0 U/ml), amylase activity (26.8 U/ml) and bile acids (4.5 mM). Stability of the main enzymes in two frozen batches of either gastric or duodenal juice was studied for 6 months. Pepsin activity decreased rapidly and adjusting the pH of gastric juice to 4 did not protect the pepsin from degradation. Lipase activity remained stable for 4 months, however decreased rapidly thereafter even after the addition of protease inhibitors. Glycerol only marginally stabilised the survival of the enzymatic activities. These results of compositional variations in the individual gastrointestinal juices and the effect of storage conditions on enzyme activities are useful for the design of in vitro models enabling human digestive juices to simulate physiological digestion.

Sub-optimal breastfeeding practices still prevail in many countries, especially in traditional rural communities. Despite high breastfeeding initiation rates and long total duration of breastfeeding, exclusive breastfeeding is a rare practice. In the present study, quantitative methods were used to identify current infant feeding practices in 12 rural communities in The GAMBIA: Results indicated that delayed initiation of breastfeeding, prelacteal feeding and failure to practice exclusive breastfeeding were widespread. Qualitative data further indicated that current beliefs and practices were strongly influenced by traditional beliefs and practices. These were kept very much alive by elders, both women and men, including husbands. The results also showed an unexpected support for bottle-feeding from both male and female elders who considered it part of the modernization process. A strategy for promoting early initiation of breastfeeding, feeding of colostrum and exclusive breastfeeding for 6 months in rural communities should therefore incorporate traditional beliefs and practices into modern messages on optimal breastfeeding. Traditional beliefs and practices in the study setting that could be used in this way included knowledge from the population's acquaintance with the newborns of their livestock. It also included the traditional practice of mothers taking their very young children with them when going to work in the fields. The paper suggests such a strategy by developing a matrix to establish linkages between modern and traditional knowledge on a specific practice. Such linkages facilitate the acceptance of recommendations on infant feeding by mothers in these communities. The strategy recommends an expanded target group to include elders and husbands, as the data show that these groups are highly influential in matters regarding patterns of child feeding.

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Lactoferrin (LF) is a protein present in milk and other body fluids that plays important biological roles. As part of a diet, LF must survive gastrointestinal conditions or create bioactive fragments to exert its effects. The degradation of LF and formation of bioactive peptides is highly dependent on individual variation in intraluminal composition. The present study was designed to compare the degradation and peptide formation of bovine LF (bLF) following in vitro digestion under different simulated intraluminal conditions. Human gastrointestinal (GI) juices were used in a 2-step model digestion to mimic degradation in the stomach and duodenum. To account for variation in the buffering capacity of different lactoferrin-containing foods, gastric pH was adjusted either slowly or rapidly to 2.5 or 4.0. The results were compared with in vivo digestion of bLF performed in 2 volunteers. High concentration of GI juices and fast pH reduction to 2.5 resulted in complete degradation in the gastric step. More LF resisted gastric digestion when pH was slowly reduced to 2.5 or 4.0. Several peptides were identified; however, few matched with previously reported peptides from studies using nonhuman enzymes. Surprisingly, no bovine lactoferricin, f(17-41), was identified during in vitro or in vivo digestion under the intraluminal conditions used. The diversity of enzymes in human GI juices seems to affect the hydrolysis of bLF, generating different peptide fragments compared with those obtained when using only one or a few proteases of animal origin. Multiple sequence analysis of the identified peptides indicated a motif consisting of proline and neighboring hydrophobic residues that could restrict proteolytic processing. Further structure analysis showed that almost all proteolytic cutting sites were located on the surface and mainly on the nonglycosylated half of lactoferrin. Digestion of bLF by human enzymes may generate different peptides from those found when lactoferrin is digested by nonhuman enzymes. The degradation of LF in the GI tract should be taken into consideration when health effects are proposed, because LF has now been approved by the European Food Safety Authority as a dietary supplement in food products.