Browsing by Author "McNabb WC"

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    A Mathematical Model for the Hydrogenotrophic Metabolism of Sulphate-Reducing Bacteria.
    (Frontiers Media S.A., 2019-07-17) Smith NW; Shorten PR; Altermann E; Roy NC; McNabb WC; Greening C
    Sulphate-reducing bacteria (SRB) are studied across a range of scientific fields due to their characteristic ability to metabolise sulphate and produce hydrogen sulphide, which can lead to significant consequences for human activities. Importantly, they are members of the human gastrointestinal microbial population, contributing to the metabolism of dietary and host secreted molecules found in this environment. The role of the microbiota in host digestion is well studied, but the full role of SRB in this process has not been established. Moreover, from a human health perspective, SRB have been implicated in a number of functional gastrointestinal disorders such as Irritable Bowel Syndrome and the development of colorectal cancer. To assist with the study of SRB, we present a mathematical model for the growth and metabolism of the well-studied SRB, Desulfovibrio vulgaris in a closed system. Previous attempts to model SRB have resulted in complex or highly specific models that are not easily adapted to the study of SRB in different environments, such as the gastrointestinal tract. We propose a simpler, Monod-based model that allows for easy alteration of both key parameter values and the governing equations to enable model adaptation. To prevent any incorrect assumptions about the nature of SRB metabolic pathways, we structure the model to consider only the concentrations of initial and final metabolites in a pathway, which circumvents the current uncertainty around hydrogen cycling by SRB. We parameterise our model using experiments with varied initial substrate conditions, obtaining parameter values that compare well with experimental estimates in the literature. We then validate our model against four independent experiments involving D. vulgaris with further variations to substrate availability. Further use of the model will be possible in a number of settings, notably as part of larger models studying the metabolic interactions between SRB and other hydrogenotrophic microbes in the human gastrointestinal tract and how this relates to functional disorders.
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    A protocol combining breath testing and ex vivo fermentations to study the human gut microbiome
    (Elsevier Inc, 2021-03-19) Payling L; Roy NC; Fraser K; Loveday SM; Sims IM; Janssen PH; Hill SJ; Raymond LG; McNabb WC
    This protocol describes the application of breath testing and ex vivo fermentations to study the association between breath methane and the composition and functionality of the gut microbiome. The protocol provides a useful systems biology approach for studying the gut microbiome in humans, which combines standardized methods in human breath testing and fecal sampling. The model described is accessible and easy to repeat, but its relative simplicity means that it can deviate from human physiological conditions.
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    Actinidin in Green and SunGold Kiwifruit Improves Digestion of Alternative Proteins-An In Vitro Investigation
    (MDPI (Basel, Switzerland), 2022-09-06) Kaur L; Mao B; Bailly J; Oladeji O; Blatchford P; McNabb WC; Recio I
    Both Hayward (green) and SunGold (gold) kiwifruit varieties contain a proteolytic enzyme, actinidin, that has been reported to enhance the upper tract digestion of animal proteins. Unlike the other gold varieties, which do not contain any actinidin, the SunGold variety contains significantly higher actinidin activity, but its activity is still much lower than that present in the green (Hayward) fruit. The objective of this study was to determine the effectiveness of actinidin in Hayward and SunGold kiwifruit in digesting alternative proteins, including pea protein, almonds, tofu, and quinoa. The protein sources were digested using a three-stage in vitro oral-gastro-small intestinal digestion model. The findings showed that both kiwifruit extracts enhanced the breakdown (observed through SDS-PAGE) for all the studied protein sources, particularly during gastric digestion, possibly due to higher actinidin activity at gastric pH. The increase in the rate of protein breakdown was probably due to the broader specificity of actinidin compared to pepsin. For many protein sources, most of the intact proteins disappeared within the first few minutes of gastric digestion with added kiwifruit extract. Green kiwifruit extract, due to its higher actinidin activity, had a higher effect on protein breakdown than the SunGold extract. However, for some proteins and under certain digestion conditions, SunGold extract resulted in higher protein breakdown. The latter, in the absence of any digestive enzymes, also led to some protein breakdown during the small intestinal digestion phase, which was not the case for the green kiwifruit extract. The green kiwifruit extract led to the greater breakdown of polypeptide chains of Pru-du 6, a major allergen in almonds. The results, for the first time, suggest that both Hayward and SunGold kiwifruit can lead to improved breakdown and digestion of alternative proteins when consumed as part of a meal; and therefore, have the potential to be used as a digestive aid in population groups looking to achieve faster and greater protein digestion such as athletes, elderly and people with the impaired digestive system.
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    Acute effects of fresh versus dried Hayward green kiwifruit on sleep quality, mood, and sleep-related urinary metabolites in healthy young men with good and poor sleep quality
    (Frontiers Media S.A., 2023-03-14) Kanon AP; Giezenaar C; Roy NC; McNabb WC; Henare SJ; Scholey A
    Background and aims: Daily kiwifruit (KF) consumption has been associated with improved sleep quality, but underlying physiological mechanisms are unknown. This study examined acute effects of fresh and dried green KF, compared with a water control, on sleep quality, mood, and urinary serotonin and melatonin metabolite concentrations. Methods: 24 men (age: 29 ± 1 years, body mass index: 24 ± 1 kg/m2) with poor (n = 12) or good (n = 12) sleep quality participated in a randomized, single-blind crossover study. One of three treatments was consumed with a standardized evening meal; (1) the flesh of two fresh green KF, (2) dried green KF powder (including skin; equivalent to dry matter of two fresh KF) mixed with water, or (3) a water control, in their own home. Subjective and objective sleep quality, mood, waking urinary 5-hydroxyindoleacetic acid (5-HIAA), 6-sulfatoxymelatonin (aMT6s), vitamin C and B-vitamin concentrations were determined. Results: Regardless of sleep quality group, compared to control, morning sleepiness, alertness upon awakening, and vigor were improved (p < 0.05) after dried KF consumption. Compared to control, both fresh and dried KF treatments tended (p < 0.1) toward improved esteem and total mood disturbance. Both KF treatments increased (fresh +1.56 ± 0.4 ng/g, p = 0.001; dried: +1.30 ± 0.4 ng/g, p = 0.004) urinary concentration of the serotonin metabolite 5-HIAA compared to the control (4.32 ± 0.4 ng/g). In poor sleepers, ease of awakening improved by 24% after dried KF consumption (p = 0.005) and tended to improve by 13% after fresh KF intake (p = 0.052) compared to the control. Good sleepers tended toward 9% improved ratings of getting to sleep with fresh KF (p = 0.053) compared to the control. Poor sleepers had lower amounts of some B-vitamins compared to good sleepers (p < 0.05). Conclusion: Consumption of dried or fresh KF with a standard evening meal, was associated with improved aspects of sleep quality and mood, possibly mediated through changes in serotonin metabolism. Clinical trial registration: [www.anzctr.org.au], identifier [ACTRN12621000046808].
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    Adaptation of the infant gut microbiome during the complementary feeding transition
    (PLOS, 2022-07-14) McKeen S; Roy NC; Mullaney JA; Eriksen H; Lovell A; Kussman M; Young W; Fraser K; Wall CR; McNabb WC; xia Y
    The infant gut microbiome progresses in composition and function during the introduction of solid foods throughout the first year of life. The purpose of this study was to characterize changes in healthy infant gut microbiome composition, metagenomic functional capacity, and associated metabolites over the course of the complementary feeding period. Fecal samples were obtained at three 'snapshot' timepoints from infants participating in the 'Nourish to Flourish' pilot study: before the introduction of solid foods at approximately 4 months of age, after introducing solid foods at 9 months of age, and after continued diet diversification at 12 months of age. KEGG and taxonomy assignments were correlated with LC-MS metabolomic profiles to identify patterns of co-abundance. The composition of the microbiome diversified during the first year of life, while the functional capacity present in the gut microbiome remained stable. The introduction of solid foods between 4 and 9 months of age corresponded to a larger magnitude of change in relative abundance of sequences assigned to KEGG pathways and taxonomic assignments, as well as to stronger correlations with metabolites, compared to the magnitude of changes and number of correlations seen during continued diet diversification between 9 and 12 months of age. Changes in aqueous fecal metabolites were more strongly correlated with KEGG pathway assignments, while changes in lipid metabolites associated with taxonomic assignments, particularly between 9 and 12 months of age. This study establishes trends in microbiome composition and functional capacity occurring during the complementary feeding period and identifies potential metabolite targets for future investigations.
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    Alternative protein-based foods must contribute to micronutrient adequacy
    (Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2024-01-29) Smith NW; Fletcher AJ; McNabb WC
    Sustainable diets must consider health, economic, environmental, and social outcomes. The development and production of alternative protein foods should also make these considerations. We examined the nutritional role of these foods, with New Zealand (NZ) as a case study. We used the DELTA Model® to assess 2020 NZ nutrient supply. We then simulated the substitution of 50% of meat supply (by mass) with various plant protein sources (soy, peas, beans, and mushroom), and observed the impact on nutrient supply. NZ had an undersupply of calcium (38%), vitamin E (34% deficit), dietary fibre (20%), potassium (13%), and vitamin C (10%) compared to population requirements. Contrastingly, there was sufficient protein and amino acid supply for an additional 2.4 million people. Halving of meat supply resulted in decreased availability for potassium (21% deficit), zinc (17%), folate (10%), and iron (9%). Soy proved the best nutritional replacement for meat, with reduced deficits for all undersupplied nutrients compared to 2020. Replacement with other modelled protein sources resulted in greater nutrient deficits. The nutritional implications beyond protein must be considered when making dietary substitutions. There are clear public health reasons to fortify alternative proteins with both the nutrients lost in substitution and those already in deficit.
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    Analysis of global nutrient gaps and their potential to be closed through redistribution and increased supply
    (Frontiers Media S.A., 2024-08-09) Fletcher AJ; Lozano R; McNabb WC; Van Der Wielen N
    Global food systems are crucial for sustaining life on Earth. Although estimates suggest that the current production system can provide enough food and nutrients for everyone, equitable distribution remains challenging. Understanding global nutrient distribution is vital for addressing disparities and creating effective solutions for the present and future. This study analyzes global nutrient supply changes to address inadequacies in certain populations using the existing DELTA Model®, which uses aggregates of global food production to estimate nutrient adequacy. By examining the 2020 global food commodity and nutrient distribution, we project future food production in 2050 needs to ensure global adequate nutrition. Our findings reveal that while some nutrients appear to be adequately supplied on a global scale, many countries face national insufficiencies (% supply below the population reference intake) in essential vitamins and minerals, such as vitamins A, B12, B2, potassium, and iron. Closing these gaps will require significant increases in nutrient supply. For example, despite global protein supply surpassing basic needs for the 2050 population, significant shortages persist in many countries due to distribution variations. A 1% increase in global protein supply, specifically targeting countries with insufficiencies, could address the observed 2020 gaps. However, without consumption pattern changes, a 26% increase in global protein production is required by 2050 due to population growth. In this study, a methodology was developed, applying multi-decade linear convergence to sufficiency values at the country level. This approach facilitates a more realistic assessment of future needs within global food system models, such as the DELTA Model®, transitioning from idealized production scenarios to realistic projections. In summary, our study emphasizes understanding global nutrient distribution and adjusting minimum global nutrient supply targets to tackle country-level inequality. Incorporating these insights into global food balance models can improve projections and guide policy decisions for sustainable, healthy diets worldwide.
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    Animal and plant-sourced nutrition: Complementary not competitive
    (CSIRO Publishing, 2022-05) Smith NW; Fletcher AJ; Hill JP; McNabb WC; Pembleton K
    Debate on the sustainability of the global food system often compares the environmental, economic and health impacts of plant- and animal-sourced foods. This distinction can mask the considerable variation in impacts across and within these food groups. Moreover, the nutritional benefits of these food groups are insufficiently discussed. In this review, we highlight the nutritional contribution to the current global food system of both plant- and animal-sourced foods and place their impacts on human health in the global context. We highlight how the comparison of the environmental impacts of foods via life cycle analyses can change on the basis of the functional unit used, particularly the use of mass as opposed to nutrient content or nutrient richness. We review the literature on the affordability of nutrient-adequate diets, demonstrating the presence of both plant- and animal-sourced foods in affordable nutritious diets. Finally, we address the potential of alternative food sources that are gaining momentum, to ask where they may fit in a sustainable food system. We conclude that there is a clear place for both plant- and animal-sourced foods in future sustainable food systems, and a requirement for both for sustainable global nutrition; as such, the two groups are complementary and not competitive.
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    Biotransformation of Rutin in In Vitro Porcine Ileal and Colonic Fermentation Models
    (American Chemical Society, 2023-08-23) Ulluwishewa D; Montoya CA; Mace L; Rettedal EA; Fraser K; McNabb WC; Moughan PJ; Roy NC
    Quercetin, a polyphenol antioxidant, is widely distributed in food in the form of glycoside rutin, which is not readily absorbed in the gastrointestinal tract. The microbiota of the colon is known to biotransform rutin, generating quercetin aglycones that can be absorbed. We investigated the role of the ileal and colonic microbiota in rutin biotransformation using established in vitro fermentation models. Overall, a higher rate of rutin biotransformation was observed during colonic fermentation compared with ileal fermentation. The colonic microbiome showed higher potential for rutin conversion to quercetin through an increased abundance of α-rhamnosidase- and β-glucosidase-encoding genes compared to the ileal microbiome. Nonetheless, rutin metabolism occurred rapidly during ileal fermentation (∼20% rutin disappearance after 1 h). The appearance of quercetin varied depending on the ileal inoculum and correlated with an increased abundance of Firmicutes, suggesting that quercetin absorption could be improved via modulation of the ileal microbiota.
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    Competition for Hydrogen Prevents Coexistence of Human Gastrointestinal Hydrogenotrophs in Continuous Culture.
    (Frontiers Media S.A., 2020-05-29) Smith NW; Shorten PR; Altermann E; Roy NC; McNabb WC; Kappler U
    Understanding the metabolic dynamics of the human gastrointestinal tract (GIT) microbiota is of growing importance as research continues to link the microbiome to host health status. Microbial strains that metabolize hydrogen have been associated with a variety of both positive and negative host nutritional and health outcomes, but limited data exists for their competition in the GIT. To enable greater insight into the behaviour of these microbes, a mathematical model was developed for the metabolism and growth of the three major hydrogenotrophic groups: sulphate-reducing bacteria (SRB), methanogens and reductive acetogens. In batch culture simulations with abundant sulphate and hydrogen, the SRB outcompeted the methanogen for hydrogen due to having a half-saturation constant 106 times lower than that of the methanogen. The acetogen, with a high model threshold for hydrogen uptake of around 70 mM, was the least competitive. Under high lactate and zero sulphate conditions, hydrogen exchange between the SRB and the methanogen was the dominant interaction. The methanogen grew at 70% the rate of the SRB, with negligible acetogen growth. In continuous culture simulations, both the SRB and the methanogen were washed out at dilution rates above 0.15 h-1 regardless of substrate availability, whereas the acetogen could survive under abundant hydrogen conditions. Specific combinations of conditions were required for survival of more than one hydrogenotroph in continuous culture, and survival of all three was not possible. The stringency of these requirements and the inability of the model to simulate survival of all three hydrogenotrophs in continuous culture demonstrates that factors outside of those modelled are vital to allow hydrogenotroph coexistence in the GIT.
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    Complete Annotated Genome Sequence of Limosilactobacillus fermentum AGR1487.
    (American Society for Microbiology, 2021-01-07) Bailie MA; Altermann E; Young W; Roy NC; McNabb WC; Putonti C
    Limosilactobacillus fermentum is a probiotic species; however, L. fermentum AGR1487 increases colon inflammation in germfree mice and decreases barrier integrity in Caco-2 cells. The AGR1487 genome was sequenced to explore these phenotypes. The genome is a single, circular, 1,939,032-bp chromosome with a G+C content of 52.17% and no plasmids.
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    Complete Genome Sequence of Lactobacillus fermentum Strain AGR1485, a Human Oral Isolate.
    (American Society for Microbiology, 2020-09-03) Bailie MA; Altermann E; Young W; Roy NC; McNabb WC; Gill SR
    Lactobacillus fermentum is found in food products and is generally considered safe. L. fermentum AGR1485 promotes barrier integrity in Caco-2 cells and has genetic similarities to other known probiotic L. fermentum strains. L. fermentum AGR1485 has potential as a probiotic and was sequenced to explore these probiotic properties. The genome is a 2.2-Mbp circular chromosome with no plasmids and a GC content of 51.15%.
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    Complete Genome Sequences of Eight Faecalibacterium sp. Strains Isolated from Healthy Human Stool
    (American Society for Microbiology, 2023-01-24) Fraccascia D; Chanyi RM; Altermann E; Roy NC; Flint SH; McNabb WC; Dunning Hotopp JC
    Eight Faecalibacterium sp. strains were isolated from feces of healthy human volunteers. Here, we describe their genome sequences. The genome sizes ranged from 2.78 Mbp to 3.23 Mbp, with an average GC content of 56.6% and encoding 2,795 protein-coding genes on average.
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    Complex network analysis and health implications of nutrient trade
    (Elsevier BV, 2024-03) Silvestrini MM; Smith NW; Fletcher AJ; McNabb WC; Sarti FM
    Food trade plays a key role in global nutrition, but the essential nutrients within this trade are understudied. We investigated the global nutrient trade network from 1986 to 2020, examining the relationship with income level and health outcomes. Bilateral nutrient trade data for 48 nutrients and 254 countries/economies was produced, made accessible through an interactive online application. Nutrients of interest in the context of food security and health (protein, calcium, iron, and vitamins A and B12) were examined using network analysis, animated graphs, and logistic regression to demonstrate the inequitable nature of nutrient trade, but its positive role in current nutrition-related disease. Food trade policy should be set with micronutrient content and deficiency in mind to address food security, nutrition, and health.
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    Concentrations of Fecal Bile Acids in Participants with Functional Gut Disorders and Healthy Controls
    (MDPI (Basel, Switzerland), 2021-09-09) James SC; Fraser K; Young W; Heenan PE; Gearry RB; Keenan JI; Talley NJ; Joyce SA; McNabb WC; Roy NC; Apidianakis Y; Agapiou A
    Bile acids are metabolites involved in nutrient absorption and signaling with levels influenced by dietary intake, metabolic processes, and the gut microbiome. We aimed to quantify 23 bile acids in fecal samples to ascertain if concentrations differed between healthy participants and those with functional gut disorders. Fecal bile acids were measured using liquid chromatography-mass spectrometry (LC-MS) in the COMFORT (The Christchurch IBS cohort to investigate mechanisms for gut relief and improved transit) cohort of 250 participants with Rome IV IBS (IBS-constipation (C), IBS-diarrhea (D), IBS-mixed (M)), functional gut disorders (functional constipation (FC), functional diarrhea (FD)) and healthy controls (FC n = 35, FD n = 13, IBS-C n = 24, IBS-D n = 52, IBS-M n = 29, and control n = 97). Dietary information was recorded to ascertain three-day dietary intake before fecal samples were collected. Fecal bile acid concentrations, predominantly primary bile acids, were significantly different between all functional gut disorder participants and healthy controls (CDCA p = 0.011, CA p = 0.003) and between constipation (FC + IBS-C) and diarrhea (FD + IBS-D) groups (CDCA p = 0.001, CA p = 0.0002). Comparison of bile acids between all functional groups showed four metabolites were significantly different, although analysis of combined groups (FC + IBS-C vs. FD + IBS-D) showed that 10 metabolites were significantly different. The bile acid profiles of FD individuals were similar to those with IBS-D, and likewise, those with FC were similar to IBS-C. Individuals with a diarrhea phenotype (FD + IBS-D) had higher concentrations of bile acids compared to those with constipation (FC + IBS-C). Bile acid metabolites distinguish between individuals with functional gut disorders and healthy controls but are similar in constipation (or diarrhea) whether classified as IBS or not.
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    Concentrations of Plasma Amino Acids and Neurotransmitters in Participants with Functional Gut Disorders and Healthy Controls
    (MDPI (Basel, Switzerland), 2023-02-20) James SC; Fraser K; Cooney J; Günther CS; Young W; Gearry RB; Heenan PE; Trower T; Keenan JI; Talley NJ; McNabb WC; Roy NC; Jang C
    Amino acids are important in several biochemical pathways as precursors to neurotransmitters which impact biological processes previously linked to functional gastrointestinal disorders (FGIDs). Dietary protein consumption, metabolic host processes, and the gut microbiome can influence the plasma concentration of amino acids and neurotransmitters, and their uptake by tissues. The aim of this analysis was to quantify 19 proteogenic and 4 non-proteogenic amino acids and 19 neurotransmitters (including precursors and catabolites, herein referred to as neurotransmitters) to ascertain if their circulating concentrations differed between healthy participants and those with FGIDs. Plasma proteogenic and non-proteogenic amino acids and neurotransmitters were measured using ultra-performance liquid chromatography and liquid chromatography-mass spectrometry, respectively, from 165 participants (Rome IV: irritable bowel syndrome (IBS-constipation, IBS-diarrhea), functional constipation, functional diarrhea, and healthy controls). There were significant differences (p < 0.05) in pairwise comparisons between healthy controls and specific FGID groups for branched-chain amino acids (BCAAs), ornithine, and alpha-aminobutyric acid. No other significant differences were observed for the neurotransmitters or any other amino acids analyzed. Multivariate and bivariate correlation analyses between proteogenic and non-proteogenic amino acids and neurotransmitters for constipation (constipation (IBS-C and functional constipation) and phenotypes diarrhea (IBS-D and functional diarrhea)) and healthy controls suggested that associations between BCAAs, 5-hydroxytryptophan, and kynurenine in combination with tyrosine, 3,4-dihydroxyphenylalanine, and 3,4-dihydroxyphenylacetic acid and associations with gamma-aminobutyric acid, glutamate, asparagine, and serine are likely disrupted in FGID phenotypes. In conclusion, although correlations were evident between some proteogenic and non-proteogenic amino acids and neurotransmitters, the results showed minor concentration differences in plasma proteogenic and non-proteogenic amino acids, amino acid-derived metabolites, and neurotransmitters between FGID phenotypes and healthy controls.
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    Correction: Barnsley et al. Lifetime Climate Impacts of Diet Transitions: A Novel Climate Change Accounting Perspective. Sustainability 2021, 13, 5568
    (MDPI (Basel, Switzerland), 2022-07) Barnsley JE; Chandrakumar C; Gonzalez-Fischer C; Eme PE; Bourke BEP; Smith NW; Dave LA; McNabb WC; Clark H; Frame DJ; Lynch J; Roche JR
    The authors would like to make the following corrections about the published paper The changes are as follows: (1) Replacing the Conflicts of Interest: Conflicts of Interest: The authors declare no conflict of interest. with Conflict of Interest: The Ministry for Primary Industries (MPI) is the regulator for New Zealand’s entire primary sector. As regulator, we are responsive to the needs of all food-producing industries and have a wide range of other responsibilities. In a practical sense, our role includes protecting New Zealand from biological risk, increasing food production, minimising environmental impacts, and ensuring the food we produce in New Zealand is safe for consumers. The primary sector is wide-ranging and includes our arable and horticulture industries, as well as our red meat, dairy, fisheries and aquaculture industries. The authors apologize for any inconvenience caused and state that the scientific conclusions are unaffected. The original publication has also been updated.
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    Culture media and format alter cellular composition and barrier integrity of porcine colonoid-derived monolayers
    (Taylor and Francis Group, 2024-04-02) Barnett AM; Mullaney JA; McNabb WC; Roy NC
    Intestinal organoid technology has revolutionized our approach to in vitro cell culture due in part to their three-dimensional structures being more like the native tissue from which they were derived with respect to cellular composition and architecture. For this reason, organoids are becoming the new gold standard for undertaking intestinal epithelial cell research. Unfortunately, their otherwise advantageous three-dimensional geometry prevents easy access to the apical epithelium, which is a major limitation when studying interactions between dietary or microbial components and host tissues. To overcome this problem, we developed porcine colonoid-derived monolayers cultured on both permeable Transwell inserts and tissue culture treated polystyrene plates. We found that seeding density and culture format altered the expression of genes encoding markers of specific cell types (stem cells, colonocytes, goblets, and enteroendocrine cells), and barrier maturation (tight junctions). Additionally, we found that changes to the formulation of the culture medium altered the cellular composition of colonoids and of monolayers derived from them, resulting in cultures with an increasingly differentiated phenotype that was similar to that of their tissue of origin.
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    Differences in small intestinal apparent amino acid digestibility of raw bovine, caprine, and ovine milk are explained by gastric amino acid retention in piglets as an infant model
    (Frontiers Media S.A., 2023-09-04) Ahlborn NG; Montoya CA; Roy D; Roy NC; Stroebinger N; Ye A; Samuelsson LM; Moughan PJ; McNabb WC; Gallier S
    BACKGROUND: The rate of stomach emptying of milk from different ruminant species differs, suggesting that the small intestinal digestibility of nutrients could also differ across these milk types. OBJECTIVE: To determine the small intestinal amino acid (AA) digestibility of raw bovine, caprine, and ovine milk in the piglet as an animal model for the infant. METHODS: Seven-day-old piglets (n = 12) consumed either bovine, caprine, or ovine milk diets for 15 days (n = 4 piglets/milk). On day 15, fasted piglets received a single meal of fresh raw milk normalized for protein content and containing the indigestible marker titanium dioxide. Entire gastrointestinal tract contents were collected at 210 min postprandially. Apparent AA digestibility (disappearance) in different regions of the small intestine was determined. RESULTS: On average, 35% of the dietary AAs were apparently taken up in the small intestine during the first 210 min post-feeding, with 67% of the AA digestibility occurring in the first quarter (p ≤ 0.05) and 33% in the subsequent two quarters. Overall, except for isoleucine, valine, phenylalanine, and tyrosine, the small intestinal apparent digestibility of all AAs at 210 min postprandially in piglets fed ovine milk was, on average, 29% higher (p ≤ 0.05) than for those fed bovine milk. Except for lysine, there was no difference in the apparent digestibility (p > 0.05) of any AAs between piglets fed caprine milk or ovine milk. The apparent digestibility of alanine was higher (p ≤ 0.05) in piglets fed caprine milk than those fed bovine milk. When apparent digestibility was corrected for gastric AA retention, only small differences in the small intestinal apparent digestibility of AAs were observed across milk types. CONCLUSION: Bovine, caprine and ovine milk had different apparent small intestinal AA digestibility at 210 min postprandially. When corrected for gastric AA retention, the differences in apparent digestibility across species largely disappeared. The apparent AA digestibility differed across small intestinal locations.
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    Effect of Heat Treatment on Protein Self-Digestion in Ruminants' Milk
    (MDPI (Basel, Switzerland), 2023-09-21) Leite JAS; Montoya CA; Maes E; Hefer C; Cruz RAPA; Roy NC; McNabb WC; Liu Q; Liu H; Zhang J
    This study investigated whether heat treatments (raw, 63 °C for 30 min, and 85 °C for 5 min) affect protein hydrolysis by endogenous enzymes in the milk of ruminants (bovine, ovine, and caprine) using a self-digestion model. Self-digestion consisted of the incubation for six hours at 37 °C of the ruminants' milk. Free amino group concentration was measured by the o-phthaldialdehyde method, and peptide sequences were identified by chromatography-mass spectrometry. Results showed that heat treatments prior to self-digestion decreased the free NH2 by 59% in bovine milk heated at 85 °C/5 min, and by 44 and 53% in caprine milk heated at 63 °C/30 min and 85 °C/5 min, respectively. However, after self-digestion, only new free amino groups were observed for the raw and heated at 63 °C/30 min milk. β-Casein was the most cleaved protein in the raw and heated at 63 °C/30 min bovine milk. A similar trend was observed in raw ovine and caprine milk. Self-digestion increased 6.8-fold the potential antithrombin peptides in the bovine milk heated at 63 °C/30 min. Enhancing bioactive peptide abundance through self-digestion has potential applications in the industry for functional products. Overall, heat treatments affected the free amino groups according to the species and heat treatment applied, which was reflected in the varying degrees of cleaved peptide bonds and peptides released during self-digestion.