Modulation of gastrointestinal digestion of ß-lactoglobulin and micellar casein following binding by (-)-epigallocatechin-3-gallate (EGCG) and green tea flavanols.

The effect of binding of flavonoids, (-)-epigallocatechin-3-gallate (EGCG) and green tea extract (GTE), to beta-lactoglobulin (ß-Lg) and micellar casein (micellar casein isolate, MCI) on protein digestibility was investigated. ß-Lg resisted digestion by pepsin, but in the presence of EGCG the digestion of ß-Lg was enhanced. Binding of EGCG to ß-Lg was identified by nitro blue tetrazolium (NBT) staining and found, by isothermal titration calorimetry, to be an enthalpy-driven exothermic process, with a binding constant of 19 950 L mol-1. Binding promoted a more rapid digestion of ß-Lg during simulated upper duodenal digestion. NBT staining indicated a loss of binding of EGCG to ß-Lg during combined gastric and distal small intestinal digestion and correlated with the cleavage of ß-Lg. However, increased ß-Lg heteromer formation and reduced ß-Lg monomer digestibility were observed for the ß-Lg-GTE complex. MCI was more digestible than ß-Lg during pepsin digestion, but reduced digestibility was observed for both MCI-EGCG and MCI-GTE complexes, with loss of binding during intestinal digestion. The free radical scavenging capacity (FRSC) of EGCG remained stable for the ß-Lg-EGCG complex throughout the gastric and intestinal phases of digestion, but this was significantly lowered for the MCI-EGCG complex. These results indicated that polyphenols bind to milk proteins modulating the in vitro digestibility and FRSC of ß-Lg and MCI as a result of the formation of complexes.

Bioactive proteins in bovine colostrum and effects of heating, drying and irradiation.

Bovine colostrum (BC) contains bioactive proteins, such as immunoglobulin G (IgG), lactoferrin (LF) and lactoperoxidase (LP). BC was subjected to low-temperature, long-time pasteurization (LTLT, 63 °C, 30 min) or high-temperature, short-time pasteurization (HTST, 72 °C, 15 s) and spray-drying (SD), with or without γ-irradiation (GI, ∼14 kGy) to remove microbial contamination. Relative to unpasteurized liquid BC, SD plus GI increased protein denaturation by 6 and 11%, respectively, increasing to 19 and 27% after LTLT and to 48% after HTST, with no further effects after GI (all P < 0.05). LTLT, without or with GI, resulted in 15 or 29% denaturation of IgG, compared with non-pasteurized BC, and 34 or 58% for HTST treatment (all P < 0.05, except LTLT without GI). For IgG, only GI, not SD or LTLT, increased denaturation (30-38%, P < 0.05) but HTST increased denaturation to 40%, with further increases after GI (60%, P < 0.05). LTLT and HTST reduced LP levels (56 and 81% respectively) and LTLT reduced LF levels (21%), especially together with GI (47%, P < 0.05). Denaturation of BSA, ß-LgA, ß-LgB and α-La were similar to IgG. Methionine, a protective amino acid against free oxygen radicals, was oxidised by LTLT + GI (P < 0.05) while LTLT and HTST had no effect. Many anti-inflammatory proteins, including serpin anti-proteinases were highly sensitive to HTST and GI but preserved after LTLT pasteurization. LTLT, followed by SD is an optimal processing technique preserving bioactive proteins when powdered BC is used as a diet supplement for sensitive patients.

Spray Dried, Pasteurised Bovine Colostrum Protects Against Gut Dysfunction and Inflammation in Preterm Pigs.

OBJECTIVE: Feeding bovine colostrum (BC) improves gut maturation and function and protects against necrotizing enterocolitis, relative to formula in newborn preterm pigs. Before BC can be used for preterm infants, it is important to test if the milk processing, required to reduce bacterial load and increase shelf life, may affect bioactivity and efficacy of a BC product. METHODS: We investigated if spray dried, pasteurised BC had protective effects on gut function in preterm pigs, relative to formula. After a 2-day total parenteral nutrition period, preterm pigs were fed formula for a few hours (to induce a proinflammatory state) followed by 2 days of formula (FORM, n = 14), BC (colostrum [COLOS], n = 14), spray-dried BC (POW, n = 8), or pasteurised, spray-dried BC (POWPAS, n = 9). RESULTS: Spray drying and pasteurisation of BC decreased the concentration of transforming growth factor-ß1, -ß2 and increased protein aggregation. All of the 3 BC groups had reduced necrotizing enterocolitis severity, small intestinal levels of IL-1ß, -8, and colonic lactic acid levels, and increased intestinal villus height, hexose absorption, and digestive enzyme activities, relative to the FORM group (all P < 0.05). All of the 3 BC diets stimulated epithelial cell migration in a wound-healing model with IEC-6 cells. CONCLUSIONS: Spray drying and pasteurisation affect BC proteins, but do not reduce the trophic and anti-inflammatory effects of BC on the immature intestine. It remains to be studied if BC products will benefit preterm infants just after birth when human milk is often not available.

Transforming growth factor-ß2 and endotoxin interact to regulate homeostasis via interleukin-8 levels in the immature intestine.

A balance between pro- and anti-inflammatory signals from milk and microbiota controls intestinal homeostasis just after birth, and an optimal balance is particularly important for preterm neonates that are sensitive to necrotizing enterocolitis (NEC). We suggest that the intestinal cytokine IL-8 plays an important role and hypothesize that transforming growth factor-ß2 (TGF-ß2) acts in synergy with bacterial lipopolysaccharide (LPS) to control IL-8 levels, thereby supporting intestinal homeostasis. Preterm pigs were fed colostrum (containing TGF-ß2) or infant formula (IF) with or without antibiotics (COLOS, n = 27; ANTI, n = 11; IF, n = 40). Intestinal IL-8 levels and NEC incidence were much higher in IF than in COLOS and ANTI pigs (P < 0.001), but IL-8 levels did not correlate with NEC severity. Intestinal TGF-ß2 levels were high in COLOS but low in IF and ANTI pigs. Based on these observations, the interplay among IL-8, TGF-ß2, and LPS was investigated in a porcine intestinal epithelial cell line. TGF-ß2 attenuated LPS-induced IL-6, IL-1ß, and TNF-α release by reducing early ERK activation, whereas IL-8 secretion was synergistically induced by LPS and TGF-ß2 via NF-κB. The TGF-ß2/LPS-induced IL-8 levels stimulated cell proliferation and migration following epithelial injury, without continuous NF-κB activation and cyclooxygenase-2 expression. We suggest that a combined TGF-ß2-LPS induction of IL-8 stimulates epithelial repair just after birth when the intestine is first exposed to colonizing bacteria and TGF-ß2-containing milk. Moderate IL-8 levels may act to control intestinal inflammation, whereas excessive IL-8 production may enhance the damaging proinflammatory cascade leading to NEC.

Raw bovine milk improves gut responses to feeding relative to infant formula in preterm piglets.

For preterm neonates, the quality of the first milk is crucial for intestinal maturation and resistance to necrotizing enterocolitis (NEC). Among other factors, milk quality is determined by the stage of lactation and processing. We hypothesized that unprocessed mature bovine milk (BM; raw bovine milk) would have less bioactivity than corresponding bovine colostrum (BC) in a preterm pig model, but have improved bioactivity relative to its homogenized, pasteurized, spray-dried equivalent, whole milk powder (WMP), or a bovine milk protein-based infant formula (IF). For 5 days, newborn preterm pigs received parenteral and enteral nutrition consisting of IF (n = 13), BM (n = 13), or BC (n = 14). In a second study, WMP (n = 15) was compared with IF (n = 10) and BM (n = 9). Compared with pigs fed IF, pigs that were fed BM had significantly improved intestinal structure (mucosal weight, villus height) and function (increased nutrient absorption and enzyme activities, decreased gut permeability, nutrient fermentation, and NEC severity). BC further improved these effects relative to BM (lactase activity, lactose absorption, plasma citrulline, and tissue interleukin-8). WMP induced similar effects as BM, except for lactase activity and lactose absorption. In conclusion, the maturational and protective effects on the immature intestine decreased in the order BC>BM>WMP, but all three intact bovine milk diets were markedly better than IF. The stage of lactation (colostrum vs. mature milk) and milk processing (e.g., homogenization, fractionation, pasteurization, spray-drying) are important factors in determining milk quality during the early postnatal period of preterm neonates.