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Gastrointestinal conditions in which the transit of contents is altered may benefit from nutritional approaches to influencing health outcomes. Milk proteins modulate the transit of contents along different regions, suggesting that they have varying effects on neuromuscular function to alter gastrointestinal motility. We tested the hypothesis that bovine whey and casein milk protein hydrolysates could have direct modulatory effects on colonic motility patterns in isolated rat large intestine. Casein protein hydrolysate (CPH), whey protein concentrate (WPC), whey protein hydrolysate (WPH), and a milk protein hydrolysate (MPH; a hydrolyzed blend of 60% whey to 40% casein) were compared for their effects on spontaneous contractile waves. These contractions propagate along the length of the isolated intact large intestine (22 cm) between the proximal colon and rectum and were detected by measuring activity at 4 locations. Milk proteins were perfused through the tissue bath, and differences in contraction amplitude and frequency were quantified relative to pretreatment controls. Propagation frequency was decreased by CPH, increased by MPH, and unaffected by intact whey proteins. The reduced motility with CPH and increased motility with MPH indicate a direct action of these milk proteins on colon tissue and provide evidence for differential modulation by hydrolysate type. These findings mirror actions on lower gastrointestinal transit reported in vivo, with the exception of WPH, suggesting that other factors are required.

Colostrum plays an important role in initiating the development of the intestinal barrier in newborn mammals. Given its bioactivity, there is much interest in the potential use of bovine colostrum to improve human gastrointestinal health throughout the life span. There is evidence that bovine colostrum is effective at improving small intestinal barrier integrity and some indication that it may alter colonic motility. However, for colostrum to be used as a product to improve intestinal health, it needs to be bioactive after processing. The aim of this study was to determine whether industrial processing of bovine colostrum affects its ability to improve small intestinal barrier integrity or alter distal colon motility. Three colostrum sample types were compared; raw whole colostrum powder (WCP), raw skim colostrum powder (SCP), and industrially produced colostrum milk protein concentrate (CMPC). To determine whether these colostrum powders had different effects on small intestinal barrier integrity, their effects on the transepithelial electrical resistance across an in vitro intestinal epithelial layer (Caco-2 cells) were measured, both with and without a challenge from the proinflammatory cytokine tumor necrosis factor-α. These results showed that CMPC enhanced transepithelial electrical resistance across unchallenged epithelial cell layers, whereas the raw colostrum samples, WCP and SCP, did not have an effect. The colostrum samples were also compared to determine how they affect contractility in the distal colon isolated from the rat. Skim colostrum powder was the only sample to act directly on colonic tissue to modulate motility, increasing the amplitude of contractions. The results show that bovine colostrum is able to improve small intestinal barrier integrity and alter colon motility, and they implicate different components. The barrier integrity enhancement was apparent only in the industrial CMPC, which may have been due to the increase in protein concentration or the release of small peptides as a result of processing. The ability to alter colon motility was present in SCP but absent in WCP, again implying that an increase in protein concentration is responsible for the effect. However, this effect was not apparent for the industrially processed CMPC, suggesting denaturation or degradation of the active component. The beneficial effect of colostrum on small intestinal barrier integrity was present after processing, confirming that it is feasible to industrially produce an active product for gut health.

Bovine lactoferrin is an important milk protein with many health-promoting properties, including improving intestinal barrier integrity. Dysfunction of this barrier, commonly referred to as "leaky gut," has been linked to inflammatory and autoimmune diseases. With some processing techniques, lactoferrin isolated from milk collected at the start of the milking season (early lactation) may have lower purity than that isolated from milk collected during the rest of the milking season (mid-lactation) and could result in differences in bioactivity based on the stage of lactation. We compared reversed-phase HPLC chromatographs of early-lactation and mid-lactation preparations and found that both had large chromatograph peaks at the time predicted for lactoferrin. The notable difference between the 2 chromatographs was a much larger peak in the early-lactation lactoferrin sample that was determined to be angiogenin. Angiogenin was first identified due to its ability to induce new blood vessel formation, but is now known to be involved in numerous physiological processes. Then, we compared the effects of early-lactation and mid-lactation lactoferrin preparations in 2 bioassays: trans-epithelial electrical resistance (TEER), a measure of intestinal barrier integrity, and peripheral blood mononuclear cell cytokine secretion, a measure of immune-stimulatory properties. We found that early-lactation lactoferrin increased TEER across Caco-2 cell layers compared with control from 10 to 48 h, mid-lactation lactoferrin did not alter TEER. We also found that early-lactation lactoferrin reduced the amount of IL-8 produced by peripheral blood mononuclear cells (compared with those treated with control medium) to a greater extent than mid-lactation lactoferrin. A pro-inflammatory chemokine, IL-8 is also known to decrease barrier function. These results suggest that the decrease in IL-8 production in the presence of early-lactation lactoferrin may be the mechanism by which it increases TEER. The anti-inflammatory effect of early-lactation lactoferrin may be related to the presence of angiogenin, which is known to suppress inflammatory responses. This work indicates that products rich in angiogenin may have intestinal health benefits, and further work to investigate this is warranted.

Inflammatory bowel disease (IBD) is a poorly understood chronic immune disorder for which there is no medical cure. Milk and colostrum are rich sources of bioactives with immunomodulatory properties. Here we compared the therapeutic effects of oral delivery of bovine milk-derived iron-saturated lactoferrin (Fe-bLF), angiogenin, osteopontin (OPN), colostrum whey protein, Modulen IBD (Nestle Healthsciences, Rhodes, Australia), and cis-9,trans-11 conjugated linoleic acid (CLA)-enriched milk fat in a mouse model of dextran sulfate-induced colitis. The CLA-enriched milk fat significantly increased mouse body weights after 24d of treatment, reduced epithelium damage, and downregulated the expression of proinflammatory cytokines and nitrous oxide. Modulen IBD most effectively decreased the clinical score at d 12, and Modulen IBD and OPN most effectively lowered the inflammatory score. Myeloperoxidase activity that denotes neutrophil infiltration was significantly lower in mice fed Modulen IBD, OPN, angiogenin, and Fe-bLF. A significant decrease in the numbers of T cells, natural killer cells, dendritic cells, and a significant decrease in cytokine expression were observed in mice fed the treatment diets compared with dextran sulfate administered mice. The Fe-bLF, CLA-enriched milk fat, and Modulen IBD inhibited intestinal angiogenesis. In summary, each of the milk components attenuated IBD in mice, but with differing effectiveness against specific disease parameters.

To investigate the impact of probiotic supplementation of infant formula on immune parameters, intestinal microbiota, and metabolism, five individually housed infant rhesus monkeys exclusively fed standard infant formula supplemented with probiotics (Bifidobacterium animalis subsp. lactis HN019) from birth until 3months of age were compared with five standard formula-fed and five breast-fed monkeys. Anthropometric measurements, serum insulin, immune parameters, fecal microbiota, and metabolic profiles of serum, urine, and feces were evaluated. Consumption of B.lactis-supplemented formula reduced microbial diversity, restructured the fecal microbial community, and altered the fecal metabolome at the last two time points, in addition to increasing short-chain fatty acids in serum and urine. Circulating CCL22 was lower and threonine, branched-chain amino acids, urea, and allantoin, as well as dimethylglycine in serum and urine, were increased in the group supplemented with B.lactis compared with the standard formula-fed group. These results support a role of probiotics as effectors of gut microbial activity regulating amino acid utilization and nitrogen cycling. Future risk-benefit analyses are still needed to consolidate the existing knowledge on the long-term consequences of probiotic administration during infancy. IMPORTANCE Probiotics are becoming increasingly popular due to their perceived effects on health, despite a lack of mechanistic information on how they impart these benefits. Infant formula and complementary foods are common targets for supplementation with probiotics. However, different probiotic strains have different properties, and there is a lack of data on long-term health effects on the consumer. Given the increasing interest in supplementation with probiotics and the fact that the gastrointestinal tracts of infants are still immature, we sought to determine whether consumption of infant formula containing the probiotic Bifidobacterium animalis subsp. lactis HN019 for 3months starting at birth would impact gut microbial colonization, as well as infant immunity and metabolism, when compared with consumption of formula alone.

Monophosphogiyc~rate mutase (MPGM) catalyses the interconversion of 3-phosphoglycerate and 2-phosphoglycerate, in a reaction mechanism involving a pl~osphohistidine illter~nediate [ 1 ,I?]. A correlation of the 2.8 _& resolution electron-density map ffom X-ray crystallographic studies ofyeast MPGM with its amino acid sequence shows 2 histidines at the active site [3]. Structural studies of muscle MGP~I are much less complete, although the enzyme has been used extensively in kinetic work, e.g. [4,5]. The muscle and yeast enzymes have been shown to differ in several respects. The muscle enzyme is a dimer with identical subunits of mol. wt 28 000 [6], whereas the yeast enzyme is isolated as a tetramer composed of 4 identical subunits of mol. wt 27 000 [7]. The activity of the muscle enzyme is sensitive to modification of cysteinyl and arginyl residues [8,9], in contrast to the yeast enzyme that has no thiol [lo], and is only moderately sensitive to butanedione [l l]. In addition, a phosphohistidine peptide isolated from chicken breast muscle MGPM has been sequenced [ 121, and shows no homology with any of the 4 histidine sequences of the yeast enzyme (see table 2). We report here the purification and determination of the amino acid sequences of histidine-containing peptides from rabbit muscle MPGM to obtain an estimate of the extent of structural similarity at the active sites of the muscle and yeast enzymes.