Journal Articles

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    Characterisation of the Plasma and Faecal Metabolomes in Participants with Functional Gastrointestinal Disorders.
    (MDPI (Basel, Switzerland), 2024-12-16) Fraser K; James SC; Young W; Gearry RB; Heenan PE; Keenan JI; Talley NJ; McNabb WC; Roy NC; Fukui H
    There is evidence of perturbed microbial and host processes in the gastrointestinal tract of individuals with functional gastrointestinal disorders (FGID) compared to healthy controls. The faecal metabolome provides insight into the metabolic processes localised to the intestinal tract, while the plasma metabolome highlights the overall perturbances of host and/or microbial responses. This study profiled the faecal (n = 221) and plasma (n = 206) metabolomes of individuals with functional constipation (FC), constipation-predominant irritable bowel syndrome (IBS-C), functional diarrhoea (FD), diarrhoea-predominant IBS (IBS-D) and healthy controls (identified using the Rome Criteria IV) using multimodal LC-MS technologies. Discriminant analysis separated patients with the 'all constipation' group (FC and IBS-C) from the healthy control group and 'all diarrhoea' group (FD and IBS-D) from the healthy control group in both sample types. In plasma, almost all multimodal metabolite analyses separated the 'all constipation' or 'all diarrhoea' group from the healthy controls, and the IBS-C or IBS-D group from the healthy control group. Plasma phospholipids and metabolites linked to several amino acid and nucleoside pathways differed (p < 0.05) between healthy controls and IBS-C. In contrast, metabolites involved in bile acid and amino acid metabolism were the key differentiating classes in the plasma of subjects with IBS-D from healthy controls. Faecal lipids, particularly ceramides, diglycerides, and triglycerides, varied (p < 0.05) between healthy controls and the 'all constipation' group and between healthy controls and 'all diarrhoea' group. The faecal and plasma metabolomes showed perturbations between constipation, diarrhoea and healthy control groups that may reflect processes and mechanisms linked to FGIDs.
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    Metabolome and microbiome profiling of a stress-sensitive rat model of gut-brain axis dysfunction
    (Springer Nature Limited, 2019-10-01) Bassett SA; Young W; Fraser K; Dalziel JE; Webster J; Ryan L; Fitzgerald P; Stanton C; Dinan TG; Cryan JF; Clarke G; Hyland N; Roy NC
    Stress negatively impacts gut and brain health. Individual differences in response to stress have been linked to genetic and environmental factors and more recently, a role for the gut microbiota in the regulation of stress-related changes has been demonstrated. However, the mechanisms by which these factors influence each other are poorly understood, and there are currently no established robust biomarkers of stress susceptibility. To determine the metabolic and microbial signatures underpinning physiological stress responses, we compared stress-sensitive Wistar Kyoto (WKY) rats to the normo-anxious Sprague Dawley (SD) strain. Here we report that acute stress-induced strain-specific changes in brain lipid metabolites were a prominent feature in WKY rats. The relative abundance of Lactococcus correlated with the relative proportions of many brain lipids. In contrast, plasma lipids were significantly elevated in response to stress in SD rats, but not in WKY rats. Supporting these findings, we found that the greatest difference between the SD and WKY microbiomes were the predicted relative abundance of microbial genes involved in lipid and energy metabolism. Our results provide potential insights for developing novel biomarkers of stress vulnerability, some of which appear genotype specific.
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    Effects of Defatted Rice Bran-Fortified Bread on the Gut Microbiota Composition of Healthy Adults With Low Dietary Fiber Intake: Protocol for a Crossover Randomized Controlled Trial
    (JMIR Publications, 2024-08-29) Ng HM; Maggo J; Wall CL; Bayer SB; McNabb WC; Mullaney JA; Foster M; Cabrera DL; Fraser K; Cooney J; Trower T; Günther CS; Frampton C; Gearry RB; Roy NC
    BACKGROUND: Inadequate dietary fiber (DF) intake is associated with several human diseases. Bread is commonly consumed, and its DF content can be increased by incorporating defatted rice bran (DRB). OBJECTIVE: This first human study on DRB-fortified bread primarily aims to assess the effect of DRB-fortified bread on the relative abundance of a composite of key microbial genera and species in fecal samples. Secondary outcomes include clinical (cardiovascular risk profile), patient-reported (daily bread consumption and bowel movement, gut comfort, general well-being, and total DF intake), biological (fecal microbiota gene abundances, and fecal and plasma metabolites), and physiome (whole-gut and regional transit time and gas fermentation profiles) outcomes in healthy adults with low DF intake. METHODS: This is a 2-armed, placebo-controlled, double-blinded, crossover randomized controlled trial. The study duration is 14 weeks: 2 weeks of lead-in, 4 weeks of intervention per phase, 2 weeks of washout, and 2 weeks of follow-up. Overall, 60 healthy adults with low DF intake (<18 g [female individuals] or <22 g [male individuals] per day) were recruited in Christchurch, New Zealand, between June and December 2022. Randomly assigned participants consumed 3 (female individuals) or 4 (male individuals) slices of DRB-fortified bread per day and then placebo bread, and vice versa. The DRB-fortified bread provided 8 g (female individuals) or 10.6 g (male individuals) of total DF, whereas the placebo (a matched commercial white toast bread) provided 2.7 g (female individuals) or 3.6 g (male individuals) of total DF. Before and after each intervention phase, participants provided fecal and blood samples to assess biological responses; completed a 3-day food diary to assess usual intakes and web-based questionnaires to assess gut comfort, general and mental well-being, daily bread intake, and bowel movement via an app; underwent anthropometry and blood pressure measurements; and drank blue food dye to assess whole-gut transit time. Additionally, 25% (15/60) of the participants ingested Atmo gas-sensing capsules to assess colonic gas fermentation profile and whole-gut and regional transit time. Mean differences from baseline will be compared between the DRB and placebo groups, as well as within groups (after the intervention vs baseline). For metabolome analyses, comparisons will be made within and between groups using postintervention values. RESULTS: Preliminary analysis included 56 participants (n=33, 59% female; n=23, 41% male). Due to the large dataset, data analysis was planned to be fully completed by the last quarter of 2024, with full results expected to be published in peer-reviewed journals by the end of 2024. CONCLUSIONS: This first human study offers insights into the prospect of consuming DRB-fortified bread to effectively modulate health-promoting gut microbes, their metabolism, and DF intake in healthy adults with low DF intake. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12622000884707; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=383814. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/59227.
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    Development and validation of an LC-MS/MS method for the quantification of oral-sugar probes in plasma to test small intestinal permeability and absorptive capacity in the domestic cat (Felis catus)
    (Elsevier BV, 2024-07-15) Patterson K; Fraser K; Bernstein D; Bermingham EN; Weidgraaf K; Kate Shoveller A; Thomas D
    A novel method for quantifying the concentration of lactulose, rhamnose, xylose, and 3-O-methylglucose (3-OMG) in cat plasma using liquid chromatography-mass spectrometry (LC-MS) was developed. Domestic male cats (n = 13) were orally dosed with a solution containing the four sugars to test the permeability and absorptive capacity of their intestinal barrier. Plasma samples were taken 3 h later and were prepared with acetonitrile (ACN), dried under N2, and reconstituted in 90 % ACN with 1 mM ammonium formate. Stable isotope labelled 13C standards for each analyte were used as internal standards. Chromatographic separation was conducted using a Phenomenex Luna NH2 column with a gradient elution system of deionized water and 90 % ACN with 1 mM ammonium formate at 300 µL/min for 13 min total analysis time. Recovery trials were conducted in triplicate over three days with RSD values (%) for each day ranging from 1.2 to 1.4 for lactulose, 5.4 - 6.0 for rhamnose, 3.3 - 5.5 for xylose, and 2.6 - 5.6 for 3-OMG. Inter-day variations for each analyte were not different (p > 0.05). Limit of detection and quantification were 0.2 and 0.7 µg/mL for lactulose, 0.8 and 2.4 µg/mL for rhamnose, 0.6 and 1.8 µg/mL for xylose, and 0.3 and 1.1 µg/mL for 3-OMG, respectively. Plasma sugar concentrations recovered from cats were above the limit of quantification and below the highest calibration standard, validating the use of this method to test intestinal permeability and absorptive capacity in cats.
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    Nourishing the Infant Gut Microbiome to Support Immune Health: Protocol of SUN (Seeding Through Feeding) Randomized Controlled Trial.
    (JMIR Publications, 2024-09-02) Wall CR; Roy NC; Mullaney JA; McNabb WC; Gasser O; Fraser K; Altermann E; Young W; Cooney J; Lawrence R; Jiang Y; Galland BC; Fu X; Tonkie JN; Mahawar N; Lovell AL; Ma S
    Background: The introduction of complementary foods during the first year of life influences the diversity of the gut microbiome. How this diversity affects immune development and health is unclear. Objective: This study evaluates the effect of consuming kūmara or kūmara with added banana powder (resistant starch) compared to a reference control at 4 months post randomization on the prevalence of respiratory tract infections and the development of the gut microbiome. Methods: This study is a double-blind, randomized controlled trial of mothers and their 6-month-old infants (up to n=300) who have not yet started solids. Infants are randomized into one of 3 groups: control arm (C), standard kūmara intervention (K), and a kūmara intervention with added banana powder product (K+) to be consumed daily for 4 months until the infant is approximately 10 months old. Infants are matched for sex using stratified randomization. Data are collected at baseline (prior to commencing solid food) and at 2 and 4 months after commencing solid food (at around 8 and 10 months of age). Data and samples collected at each timepoint include weight and length, intervention adherence (months 2 and 4), illness and medication history, dietary intake (months 2 and 4), sleep (diary and actigraphy), maternal dietary intake, breast milk, feces (baseline and 4 months), and blood samples (baseline and 4 months). Results: The trial was approved by the Health and Disability Ethics Committee of the Ministry of Health, New Zealand (reference 20/NTA/9). Recruitment and data collection did not commence until January 2022 due to the COVID-19 pandemic. Data collection and analyses are expected to conclude in January 2024 and early 2025, respectively. Results are to be published in 2024 and 2025. Conclusions: The results of this study will help us understand how the introduction of a specific prebiotic complementary food affects the microbiota and relative abundances of the microbial species, the modulation of immune development, and infant health. It will contribute to the expanding body of research that aims to deepen our understanding of the connections between nutrition, gut microbiota, and early-life postnatal health. Trial Registration: Australian New Zealand Clinical Trials Registry ACTRN12620000026921; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=378654 International Registered Report Identifier (IRRID): DERR1-10.2196/56772 JMIR Res Protoc 2024;13:e56772