Use of batch culture and a two-stage continuous culture system to study the effect of supplemental alpha-lactalbumin and glycomacropeptide on mixed populations of human gut bacteria

Bioactive Compounds in Infant Formula and Their Effects on Infant Nutrition and Health: A Systematic Literature Review

Infant formulas are an alternative to replace or supplement human milk when breastfeeding is not possible. The knowledge of human milk's bioactive compounds and their beneficial effects has attracted the interest of researchers in the field of infant nutrition, as well as researchers of technology and food sciences that seek to improve the nutritional characteristics of infant formulas. Several scientific studies evaluate the optimization of infant formula composition. The bioactive compound inclusion has been used to upgrade the quality and nutrition of infant formulas. In this context, the purpose of this systematic literature review is to assess the scientific evidence of bioactive compounds present in infant formulas (α-lactalbumin, lactoferrin, taurine, milk fat globule membrane, folates, polyamines, long-chain polyunsaturated fatty acids, prebiotics, and probiotics) and their effects on infant nutrition and health. Through previously determined criteria, studies published in the last fifteen years from five different databases were included to identify the advances in the optimization of infant formula composition. Over the last few years, there has been optimization of the infant formula composition, not only to increase the similarities in their content of macro and micronutrients but also to include novel bioactive ingredients with potential health benefits for infants. Although the infant food industry has advanced in the last years, there is no consensus on whether novel bioactive ingredients added to infant formulas have the same functional effects as the compounds found in human milk. Thus, further studies about the impact of bioactive compounds in infant nutrition are fundamental to infant health.

Host Factors of Favorable Intestinal Microbial Colonization

Gut microbial colonization starts with birth and initiates a complex process between the host and the microbiota. Successful co-development of both establishes a symbiotic mutual relationship and functional homeostasis, while alterations thereof predispose the individual life-long to inflammatory and metabolic diseases. Multiple data have been provided how colonizing microbes induce a reprogramming and maturation of immunity by providing crucial instructing information to the newborn immune system. Less is known about what host factors have influence on the interplay between intestinal immunity and the composition of the gut microbial ecology. Here we review existing evidence regarding host factors that contribute to a favorable development of the gut microbiome and thereby successful maturation of gut mucosal immunity.

Alpha-Lactalbumin Enriched Whey Protein Concentrate to Improve Gut, Immunity and Brain Development in Preterm Pigs

Human milk is rich in nutritional factors, such as alpha-lactalbumin (α-Lac), and important for neonatal development, but nutrient supplementation may be required for optimal growth. Using a pig model, we hypothesized that α-Lac-enriched whey protein concentrate (WPC) supplementation improves neonatal development. Cesarean-delivered preterm pigs were fed either dilute bovine milk (REF) or REF milk supplemented with WPC with normal (STANDARD-ALPHA) or high (HIGH-ALPHA) α-Lac. Clinical, gut, immune and cognitive endpoints (open field, T-maze) were assessed and tissues collected at Day 19. The growth of STANDARD-ALPHA and HIGH-ALPHA were higher than REF (31 vs. 19 g/kg/d). Most organ weights, gut, immunity and brain variables were similar between WPC groups. HIGH-ALPHA had a higher bone mineral content, colon microbial diversity and an abundance of specific bacteria and microbial metabolites, and tended to show a faster food transit time (p = 0.07). Relative to REF, WPC pigs showed higher relative organ weights, blood amino acids, blood neutrophil function, and microbial metabolites, but lower brush-border enzyme activities and plasma cortisol. Cognition outcomes did not differ among the groups. In conclusion, WPC supplementation of milk improved some growth, gut and immunity parameters in preterm pigs. However, increasing the α-Lac content beyond human milk levels had limited effects on the immature gut and developing brain.

Dose-Dependent Alterations to In Vitro Human Microbiota Composition and Butyrate Inhibition by a Supercritical Carbon Dioxide Hops Extract

Hop cones (Humulus lupulus L.) have been used throughout history as an additive in beer brewing and as herbal supplements with medicinal and culinary properties. The objective of this study was to ascertain the effect of a range of concentrations of a supercritical CO2 extract of hops on the composition and metabolism of human gut bacterial communities using in vitro batch culture systems. Fermentations were conducted over 24 h using a mixed human fecal inoculum. Microbial metabolism was assessed by measuring organic acid production and microbial community alterations were determined by 16S rRNA gene sequencing. Butyrate, an important short chain fatty acid in maintaining colonic well-being, decreased at elevated concentrations of hops, which may partly be accounted for by the concomitant reduction of Eubacterium and Coprococcus, known butyrate-producing genera, and also the inhibition of Bifidobacterium, a beneficial organism that has a butyrogenic effect through metabolic cross-feeding with intestinal commensals. The hops compounds also caused dose-dependent increases in the potentially pathogenic Enterobacteriaceae and potentially beneficial Akkermansia. Thus, hops compounds had a significant impact on the structure of the bacterial consortium, which warrants further study including human clinical trials.

Human Milk Proteins and Their Glycosylation Exhibit Quantitative Dynamic Variations during Lactation

BACKGROUND

Proteins in human milk are essential and known to support the growth, development, protection, and health of the newborn. These proteins are highly modified by glycans that are currently being recognized as vital to protein structure, stability, function, and health of the intestinal mucosa. Although milk proteins have been studied, the quantitative changes in milk proteins and their respective site-specific glycosylation are unknown.

OBJECTIVE

This study expanded the analytical tools for milk proteins and their site-specific glycosylation and applied these tools to a large cohort to determine changes in individual protein concentrations and their site-specific N-glycosylation across lactation.

DESIGN

A tandem mass spectrometry method was applied to 231 breast-milk samples from 33 mothers in Davis, California, obtained during 7 different periods of lactation. Dynamic changes in the absolute abundances of milk proteins, as well as variation in site-specific N-glycosylation of individual proteins, were quantified.

RESULTS

α-Lactalbumin, β-casein, k-casein, and α-antitrypsin were significantly increased from colostrum to transitional milk (4.37 ± 1.33 g/L to 6.41 ± 0.72 g/L, 2.25 ± 0.86 g/L to 2.59 ± 0.78 g/L, 1.33 ± 0.44 g/L to 1.60 ± 0.39 g/L, and 0.09 ± 0.10 g/L to 0.11 ± 0.04 g/L, respectively; P < 0.002). α-Lactalbumin (37%), β-casein (9%), and lysozyme (159%) were higher in mature milk than in colostrum. Glycans exhibited different behavior. Fucosylated glycans of lactoferrin and high-mannose, undecorated, fucosylated, sialylated, and combined fucosylated + sialylated glycans of secretory immunoglobulin A increased during lactation even when the concentrations of the parent proteins decreased.

CONCLUSIONS

Proteins in healthy mothers vary dynamically through lactation to support the development of infants. Individual milk proteins carried unique glycan modifications that varied systematically in structure even with site specificity. The role of glycosylation in human milk proteins will be important in understanding the functional components of human milk. This trial was registered at clinicaltrials.gov as NCT01817127.

On Lactococcus lactis UL719 competitivity and nisin (Nisaplin(®)) capacity to inhibit Clostridium difficile in a model of human colon

Clostridium difficile is the most frequently identified enteric pathogen in patients with nosocomially acquired, antibiotic-associated diarrhea and pseudomembranous colitis. Although metronidazole and vancomycin were effective, an increasing number of treatment failures and recurrence of C. difficile infection are being reported. Use of probiotics, particularly metabolically active lactic acid bacteria, was recently proposed as an alternative for the medical community. The aim of this study was to assess a probiotic candidate, nisin Z-producer Lactococcus lactis UL719, competitivity and nisin (Nisaplin^®) capacity to inhibit C. difficile in a model of human colon. Bacterial populations was enumerated by qPCR coupled to PMA treatment. L. lactis UL719 was able to survive and proliferate under simulated human colon, did not alter microbiota composition, but failed to inhibit C. difficile. While a single dose of 19 μmol/L (5× the MIC) was not sufficient to inhibit C. difficile, nisin at 76 μmol/L (20×the MIC) was effective at killing the pathogen. Nisin (at 76 μmol/L) caused some temporary changes in the microbiota with Gram-positive bacteria being the mostly affected. These results highlight the capacity of L. lactis UL719 to survive under simulated human colon and the efficacy of nisin as an alternative in the treatment of C. difficile infections.

Effect of an α-lactalbumin-enriched infant formula supplemented with oligofructose on fecal microbiota, stool characteristics, and hydration status: a randomized, double-blind, controlled trial

AIMS

To evaluate the impact of oligofructose (OF)-supplemented infant formula on fecal microbiota, stool characteristics, and hydration.

METHODS

Ninety-five formula-fed infants were randomized to α-lactalbumin-enriched control formula (CF) or identical formula with 3.0 g/L OF (EF) for 8 weeks; 50 infants fed human milk (HM) were included.

RESULTS

Eighty-four infants completed the study, 70 met per-protocol criteria. Over 8 weeks, bifidobacteria increased more in EF than CF group (0.70 vs. 0.16 log10 bacterial counts/g dry feces, P = .008); EF was not significantly different from HM group (P = .32). EF group stool consistency was intermediate between CF and HM groups; at week 8, EF group had softer stools than CF (5-point scale: 1 = hard, 5 = watery; consistency score 3.46 vs. 2.82, P = .015) without significant differences in stool frequency. Physician-assessed hydration status was normal for all infants.

CONCLUSIONS

Infant formula with 3.0 g/L OF promoted bifidobacteria growth and softer stools without adversely affecting stool frequency or hydration.

Approaches that ascertain the role of dietary compounds in colonic cancer cells

Preventive approaches against cancer have not been fully developed and applied. For example, the incidence of some types of cancer, including colon cancer, is highly dependent upon lifestyle, and therefore, amenable to prevention. Among the lifestyle factors, diet strongly affects the incidence of colon cancer; however, there are no definitive dietary recommendations that protect against this malignancy. The association between diet-derived bioactives and development of colonic neoplasms will remain ill defined if we do not take into account: (1) the identity of the metabolites present in the colonic lumen; (2) their concentrations in the colon; and (3) the effect of the colonic contents on the function of individual bioactives. We review two approaches that address these questions: the use of fecal water and in vitro models of the human colon. Compared to treatment with individual diet-derived compounds, the exposure of colon cancer cells to samples from fecal water or human colon simulators mimics closer the in vitro conditions and allows for more reliable studies on the effects of diet on colon cancer development. The rationale and the advantages of these strategies are discussed from the perspective of a specific question on how to analyze the combined effect of two types of bioactives, butyrate and polyphenol metabolites, on colon cancer cells.

Xylo-oligosaccharides and inulin affect genotoxicity and bacterial populations differently in a human colonic simulator challenged with soy protein

High dietary intakes of some protein sources, including soy protein, can increase colonic DNA damage in animals, whereas some carbohydrates attenuate this. We investigated whether inulin and xylo-oligosaccharides (XOS) could be protective against DNA strand breaks by adding them to a human colonic simulator consisting of a proximal vessel (PV) (pH 5.5) and a distal vessel (DV) (pH 6.8) inoculated with human faeces and media containing soy protein. Genotoxicity of the liquid phase and microbial population changes in the vessels were measured. Soy protein (3%) was fermented with 1% low amylose cornstarch for 10 day followed by soy protein with 1% XOS or 1% inulin for 10 day. Inulin did not alter genotoxicity but XOS significantly reduced PV genotoxicity and increased DV genotoxicity. Inulin and XOS significantly increased butyrate concentration in the DV but not PV. Numbers of the key butyrate-producing bacterium Faecalibacterium prausnitzii were significantly increased in the PV and DV by inulin but significantly decreased by XOS in both vessels. Other bacteria examined were also significantly impacted by the carbohydrate treatments or by the vessel (i.e., pH). There was a significant overall inverse correlation between levels of damage induced by the ferments and levels of sulphate-reducing bacteria, Bacteroides fragilis, and acetate. In conclusion, dietary XOS can potentially modulate the genotoxicity of the colonic environment and specific bacterial groups and short chain fatty acids may mediate this.

Glycerol induces reuterin production and decreases Escherichia coli population in an in vitro model of colonic fermentation with immobilized human feces

Lactobacillus reuteri ATCC 55730 is a probiotic strain that produces, in the presence of glycerol, reuterin, a broad-spectrum antimicrobial substance. This strain has been shown to prevent intestinal infections in vivo; however, its mechanisms of action, and more specifically whether reuterin production occurs within the intestinal tract, are not known. In this study, the effects of L. reuteri ATCC 55730 on intestinal microbiota and its capacity to secrete reuterin from glycerol in a novel in vitro colonic fermentation model were tested. Two reactors were inoculated with adult immobilized fecal microbiota and the effects of daily addition of L. reuteri into one of the reactors (c.10(8) CFU mL(-1)) without or with glycerol were tested on major bacterial populations and compared with addition of glycerol or reuterin alone. The addition of glycerol alone or with L. reuteri increased numbers of the Lactobacillus-Enterococcus group and decreased Escherichia coli. The addition of reuterin significantly and selectively decreased E. coli without affecting other bacterial populations. The observed decrease in E. coli concentration during the addition of glycerol (in presence or absence of L. reuteri) could be due to in situ reuterin production because 1,3-propanediol, a typical product of glycerol fermentation, was detected during the addition of glycerol.