David Charles Dallas

David Charles Dallas
Oregon State University | OSU · College of Public Health and Human Sciences, School of Biological and Population Health, Nutrition Program

Ph.D.

About

83
Publications
25,263
Reads
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2,205
Citations
Additional affiliations
January 2016 - present
Oregon State University
Position
  • Professor (Assistant)
July 2012 - present
University of California, Davis
Position
  • PostDoc Position
Description
  • Post-doctoral research on naturally occurring milk peptides and infant digestion
September 2008 - June 2012
University of California, Davis
Description
  • Research on digestion of human milk and identification of milk protein-linked glycans
Education
September 2008 - June 2012
University of California, Davis
Field of study
  • Nutritional Biology
August 2004 - June 2008
Rice University
Field of study
  • Health Sciences

Publications

Publications (83)
Article
Human milk-protein-derived peptides exhibit an array of bioactivities. Certain bioactivities cannot be exerted unless the peptides are absorbed across the gastrointestinal lumen into the bloodstream. The purpose of study was to determine which peptides derived from in vitro digestion of human milk could cross human intestinal Caco-2 cell monolayers...
Article
Full-text available
Background Bovine milk κ-casein-derived caseinomacropeptide (CMP) is produced in large quantities during cheesemaking and has various biological activities demonstrated via in vitro and in vivo experiments. Previous studies examined protein degradation and peptide release after casein or whey protein consumption. However, whether purified intact CM...
Article
Full-text available
Background Milk proteins contain many encrypted bioactive peptides. Whether these bioactive peptides are released in the infant intestine and exert immunomodulatory activity remains unknown. Objective This study examined in vitro immunomodulatory activities of peptides from in vitro- and in vivo-digested human milk. Methods Peptides were extracte...
Article
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Background: Though human milk feeding reduces the risk of necrotizing enterocolitis (NEC) in preterm infants compared with formula feeding, the exact risk reduction mechanism remains unknown. As NEC occurs at the distal small intestines where digestion has occurred, we applied proteomics to examine the extent to which colostrum proteins survive si...
Article
Full-text available
Caseinomacropeptide (CMP) is released from bovine kappa-casein after rennet treatment and is one of the major peptides in whey protein isolate. CMP has in vitro anti-inflammatory and antibacterial activities. CMP has two major amino acid sequences with different modifications, including glycosylation, phosphorylation and oxidation. However, no prev...
Article
Full-text available
Human milk contains numerous N-glycoproteins with functions that provide protection to the infant. Increasing understanding of the functional role of human milk glycoproteins within the infant requires toolsets to comprehensively profile their site-specific glycosylation patterns. However, optimized methods for site-specific glycosylation analysis...
Article
Full-text available
For bioactive milk peptides to be relevant to infant health, they must be released by gastrointestinal proteolysis and resist further proteolysis until they reach their site of activity. The intestinal tract is the likeliest site for most bioactivities, but it is currently unknown whether bioactive milk peptides are present therein. The purpose of...
Article
Aside from their amino acid content, dairy proteins are valuable for their ability to carry encrypted bioactive peptides whose activities are latent until released by digestive enzymes or endogenous enzymes within the food. Peptides can possess a wide variety of functionalities, such as antibacterial, antihypertensive, and antioxidative properties,...
Chapter
Full-text available
Modern mammalian milk has evolved over more than 200 million years to optimally nourish the infant (Oftedal, J Mammary Gland Biol Neoplasia 7(3):225–252, 2002; Lefèvre et al., Annu Rev Genomics Hum Genet 11(1):219–238, 2010Q2). Milk provides the infant with essential nutrients, including high quality proteins, lipids and carbohydrates, as well as m...
Chapter
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Beyond proteins, milk contains an array of smaller nitrogen (N)-containing components generally referred to as nonprotein nitrogen (NPN). These include milk protein–derived peptides, peptide hormones, amino acids (AAs), N-containing oligosaccharides, N-containing monosaccharides, nucleic acids (DNA and RNA), free nucleotides, and small molecules, i...
Article
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The article “Understanding the effects of dietary components on the gut microbiome and human health”, written by Bryna Rackerby, Hyun Jung Kim, David C. Dallas, Si Hong Park, was originally published Online First without Open Access.
Article
Full-text available
Background Potentially, orally administered antibodies specific to enteric pathogens could be administered to infants to prevent diarrheal infections, particularly in developing countries where diarrhea is a major problem. However, to prevent infection, such antibodies would need to resist degradation within the gastrointestinal tract. Methods Pal...
Article
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Breast milk contains bile salt-stimulated lipase (BSSL), which significantly increases the fat digestion capacity of newborns who have limited pancreatic lipase secretion in the first few months after birth. Problematically, Holder pasteurization used in non-profit milk banks to ensure the microbiological safety of donor milk for infants, particula...
Article
Full-text available
Our previous studies revealed that milk proteases begin to hydrolyze proteins in the mammary gland and that proteolytic digestion continues within the infant stomach. No research has measured how the release of milk peptides differs between the gastric aspirates of term and premature infants. This study examined the presence of milk peptides in mil...
Article
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The gut microbiome is the complex microbial ecosystem found in the gastrointestinal tract of humans and animals. It plays a vital role in host development, physiology and metabolism, and has been implicated as a factor in brain function, behavior, mental health, and many disease states. While many factors, including host genetics and environmental...
Article
Full-text available
Oral administration of engineered immunoglobulins has the potential to prevent enteric pathogen-induced diarrhea in infants. To prevent infection, these antibodies need to survive functionally intact in the proteolytic environment of the gastrointestinal tract. This research examined both ex vivo and in vivo the functional survival across infant di...
Article
Background and aims Preterm infants are born with a gastrointestinal tract insufficiently developed to digesting large quantities of human milk proteins. Peptides released from the digestion of human milk proteins have been identified with bioactivities that may be beneficial to the developing infant. However, it is unknown how prematurity affects...
Article
Full-text available
Oral administration of enteric pathogen-specific immunoglobulins may be an ideal approach for preventing infectious diarrhea in infants and children. For oral administration to be effective, antibodies must survive functionally intact within the highly proteolytic digestive tract. As an initial step toward assessing the viability of this approach,...
Article
Full-text available
To help rationally design an antibody for oral administration, we examined how different isotypes (IgG, IgA and sIgA) with the same variable sequence affect antibody stability across digestion. We compared the degradation of recombinant palivizumab (IgG1), and recombinant IgA and sIgA versions of palivizumab spiked in human milk to the degradation...
Article
Full-text available
Oral administration of pathogen-specific recombinant antibodies may help to prevent infant gastrointestinal (GI) pathogen infection; however, to neutralize an infectious agent, these antibodies must resist degradation in the GI tract. Palivizumab, a recombinant antibody specific for the respiratory syncytial virus (RSV), was used as a model for pat...
Article
Full-text available
Orally delivered antibodies may be useful for the prevention of enteric pathogen infection, but to be effective they need to survive intact across digestion through the gastrointestinal tract. As a test case, we fed a recombinant human antibody, palivizumab, spiked into human milk to four infants and collected gastric, intestinal and stool samples....
Article
The survival of antibody isotypes specific to pertussis toxin (PT) and filamentous hemagglutinin (FHA) from mother’s own milk (MBM) and donor breast milk (DBM) during preterm infant digestion was investigated. Feed, gastric, and stool samples were collected from 20 preterm mother–infant pairs at 8–9 days and 21–22 days postpartum. Samples were anal...
Article
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Immunomodulatory proteins from human milk may enhance the protection and development of the infant's gut. This study compared the immunomodulatory effects of treatment with milk from preterm-(PM) and term-delivering (TM) mothers and pasteurized donor milk (DM) on cytokine gene expression in human macrophage-like cells derived from the monocytic cel...
Article
Full-text available
To prevent infectious diarrhea in infants, orally-supplemented enteric pathogen-specific recombinant antibodies would need to resist degradation in the gastrointestinal tract. Palivizumab, a recombinant antibody specific to respiratory syncytial virus (RSV), was used as a model to assess the digestion of neutralizing antibodies in infant digestion....
Article
Background: Human milk peptides released by gastrointestinal proteases have been identified with bioactivities that can benefit the infant but must first reach their respective sites of activity. Peptides in the stool either survived to or were released inside the intestinal tract, and thus had the opportunity to exert bioactivity there. However,...
Presentation
During digestion, human lactoferrin peptides are released by the action of milk, gastric, and intestinal proteases. Some of these peptides are bioactive, but must be released and survive further digestion until they reach their site of activity in the stomach or intestine. In order to create a map of which lactoferrin peptides are present at which...
Article
Consumption of mothers' milk is associated with reduced incidence and severity of enteric infections, leading to reduced morbidity in breastfed infants. Fucosylated and sialylated human milk oligosaccharides (HMO) are important for both direct antimicrobial action - likely via a decoy effect - and indirect antimicrobial action through commensal gro...
Article
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Antenatal milk anti-influenza antibodies may provide additional protection to newborns until they are able to produce their own antibodies. To evaluate the relative abundance of milk, we studied the antibodies specific to influenza A in feeds and gastric contents and stools from preterm infants fed mother’s own breast milk (MBM) and donor breast mi...
Article
Nationally representative data from mother-child dyads that capture human milk composition (HMC) and associated health outcomes are important for advancing the evidence to inform federal nutrition and related health programs, policies, and consumer information across the governments in the United States and Canada as well as in nongovernment sector...
Article
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Maternal antibody transfer to the newborn provides essential support for the infant’s naïve immune system. Preterm infants normally receive maternal antibodies through mother’s own breast milk (MBM) or, when mothers are unable to provide all the milk required, donor breast milk (DBM). DBM is pasteurized and exposed to several freeze–thaw cycles, wh...
Article
Full-text available
Digestion of milk proteins in the premature infant stomach releases functional peptides; however, which peptides are present has not been reported. Premature infants are often fed a combination of human milk and bovine milk fortifiers, but the variety of functional peptides released from both human and bovine milk proteins remains uncharacterized....
Data
The complete list of peptides identified in the HMF, milk, and gastric samples. Sequence lists the peptide sequence. Species lists the peptide's parent protein species. Protein Name lists the parent protein. Start and Stop list the amino acid position the peptide is derived from in the parent protein. HMF, Milk, and Gastric list the number of sampl...
Article
Background: Human milk immunoglobulins (Ig) are an important support for the naïve infant immune system; yet the extent to which these proteins survive within the infant digestive tract, particularly for preterm infants, is poorly studied. Objectives: Our objective was to evaluate the survival of human milk Igs in the preterm stomach across post...
Article
Full-text available
Human milk provides immunoglobulins (Igs) that supplement the passive immune system of neonates; however, the extent of survival of these Igs during gastric digestion and whether this differs between preterm and term infants remains unknown. Human milk, and infant gastric samples at 2 h post-ingestion were collected from 15 preterm (23–32 week ge...
Chapter
Full-text available
Human milk and dairy products are important parts of human nutrition. In addition to supplying nutrients, milk proteins contain fragments—peptides—with important biological functions that are released during processing or digestion. Besides their potential functional relevance, peptides released during processing can be used as markers of ripening...
Article
Sodium caseinate hydrolysates (NaCaH) contain biologically active peptides that can positively influence human health. However, their intense bitterness hinders their inclusion in food products. To our knowledge, no studies have investigated whether a correlation between bitterness and bioactivity exists in NaCaH, so it is not yet known what effect...
Article
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Aim: This study investigated the effect of time post-ingestion on gastric digestion and gastric hormones after feeding preterm infants unfortified and fortified human milk. Methods: Human milk and infant gastric samples were collected from 14 preterm (23-32 wk birth gestational age) mother-infant pairs within 7-98 days postnatal age. Gastric sam...
Article
Full-text available
Previous work demonstrates that proteases present in human milk release hundreds of peptides derived from milk proteins. However, the question of whether human milk protein digestion begins within the mammary gland remains incompletely answered. The primary objective of this study was to determine whether proteolytic degradation of human milk prote...
Article
Full-text available
Human milk contains active proteases that initiate hydrolysis of milk proteins within the mammary gland. Milk expressed at the beginning of feeding is known as foremilk and that at the end of feeding is known as hindmilk. As hindmilk contains higher fat, vitamins A and E, and higher calories than foremilk, feeding only hindmilk initially and reserv...
Article
Objectives: Whether premature infants have lower gastric protein digestive capacity than term infants and the extent to which human milk proteases contribute to overall gastric digestion are unknown and were investigated in this study. Methods: Human milk and infant gastric samples were collected from 16 preterm (24-32 wk gestational age (GA)) a...
Article
Objectives: Our previous studies suggested that human milk proteases begin to hydrolyze proteins in the mammary gland and continue within the term infant stomach. No research has measured milk protease and pepsin activity in the gastric aspirates of preterm infants after human milk feeding. This study investigated how the concentrations of human m...
Article
Full-text available
Practical applications: The developed food-grade fractionation system, allowed for a simple and reasonably scaled approach to separating a NaCaH, into physicochemically different fractions that could be evaluated by a sensory panel. The method of sensory evaluation used in this study, in which NaCaH samples are impregnated into paper-disks, provid...
Article
During processing and digestion, milk proteins are disassembled into peptides with an array of biological functions, including antimicrobial, angiotensin-converting enzyme inhibition, antioxidant, opioid, and immunomodulation. These functions are summarized in numerous reviews, yet information on which peptides have which functions remains scattere...
Article
Background: Peptidomics research has demonstrated that protease activity is higher in breast milk from preterm- delivering mothers than from term-delivering mothers. However, to our knowledge, the effect of the degree of prematurity and postnatal age on proteases and protease inhibitors in human milk remains unknown. Objective: We aimed to determi...
Chapter
Full-text available
Milk proteins are a complex and diverse source of biological activities. Beyond their function, intact milk proteins also act as carriers of encrypted functional sequences that, when released as peptides, exert biological functions, including antimicrobial and immunomodulatory activity, which could contribute to the infant's competitive success. Re...
Article
Exclusively breast-fed infants can exhibit clear signs of IgE or non IgE-mediated cow's milk allergy. However, the definite characterization of dietary cow's milk proteins (CMP) that survive the maternal digestive tract to be absorbed into the bloodstream and secreted into breast milk remains missing. Herein, we aimed at assessing possible CMP-deri...
Article
Full-text available
Proteins are not equally digestible—their proteolytic susceptibility varies by their source and processing method. Incomplete digestion increases colonic microbial protein fermentation (putrefaction), which produces toxic metabolites that can induce inflammation in vitro and have been associated with inflammation in vivo. Individual humans differ i...
Article
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Scope: The microorganisms that make up kefir grains are well known for lactose fermentation, but the extent to which they hydrolyze and consume milk proteins remains poorly understood. Peptidomics technologies were used to examine the proteolytic activity of kefir grains on bovine milk proteins. Methods and results: Gel electrophoresis revealed...
Article
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Milk contains elements of numerous proteolytic systems (zymogens, active proteases, protease inhibitors and protease activators) produced in part from blood, in part by mammary epithelial cells and in part by immune cell secretion. Researchers have examined milk proteases for decades, as they can cause major defects in milk quality and cheese produ...
Article
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Peptidomics is an emerging field branching from proteomics that targets endogenously produced protein fragments. Endogenous peptides are often functional within the body-and can be both beneficial and detrimental. This review covers the use of peptidomics in understanding digestion, and identifying functional peptides and biomarkers. Various techni...
Article
Hundreds of naturally occurring milk peptides are present in term human milk. Preterm milk is produced before complete maturation of the mammary gland, which could change milk synthesis and secretion processes within the mammary gland, leading to differences in protein expression and enzymatic activity, thereby resulting in an altered peptide profi...
Article
Full-text available
Little is known about the digestive process in infants. In particular, the chronological activity of enzymes across the course of digestion in the infant remains largely unknown. To create a temporal picture of how milk proteins are digested, enzyme activity was compared between intact human milk samples from three mothers and the gastric samples f...
Article
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An extensive mass spectrometry analysis of the human milk peptidome has revealed almost 700 endogenous peptides from 30 different proteins. Two in-house computational tools were created and used to visualize and interpret the data by both alignment of the peptide quasi-molecular ion intensities and estimation of the differential enzyme participatio...
Article
Numerous milk components, such as lactoferrin, are recognized as health-promoting compounds. A growing body of evidence suggests that glycans could mediate lactoferrin's bioactivity. Goat milk lactoferrin is a candidate for infant formula supplementation because of its high homology with its human counterpart. The aim of this study was to character...
Chapter
Full-text available
Milk has evolved to provide only components that will give selective advantage to the growing neonate. Oligosaccharides—short polymers made of several monosaccharides—are carbohydrates present in all mammalian milks studied so far and cannot be degraded by the infant’s digestive enzymes. However, oligosaccharides selectively feed beneficial commens...
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An analysis of dairy peptides that lower blood pressure or prevent cancer cell proliferation. Future research should focus on determining the functions of peptides that occur naturally in dairy products or that are released during digestion in the consumer.
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In vitro digestion of isolated milk proteins results in milk peptides with a variety of actions. However, it remains unclear to what degree protein degradation occurs in vivo in the infant stomach and whether peptides previously annotated for bioactivity are released. This study combined nanospray liquid chromatography separation with time-of-fligh...