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Browsing by Subject "nutrition"

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  • Lalli, Marianne (2024)
    Background: The infant gut microbiome undergoes major temporal changes in the first year of life, crucial for supporting normal development and long-term health. The immense diversity of fiber structures in breast milk and later in solid foods pose unique selection pressures on the gut microbiome maturation by providing novel substrates for the microbiota. However, the longitudinal impact of complementary food-derived fibers on the taxonomic and functional maturation of the gut microbiome during the gradual transition from breast milk to solid foods is not well understood. Objectives: My objective was to examine how breast milk, its fiber and complementary food fibers in the broader context of overall infant diet may affect the gut microbiome bacterial species composition and support age-appropriate gut bacterial maturation trajectories during first year of life. Methods: Longitudinal and cross-sectional development of 68 infant gut microbiomes and 33 metabolomes were examined with linear mixed models to determine the impact of infant nutrition on gut microbiome taxa and functional development. Nutrition assessments were based on detailed quantitative weighted 3-day food records (months 3,6,9,12) and the intakes of total dietary fiber with its food sources and fiber fractions relied on current internationally approved CODEX-compliant values. Questionnaires were utilized to monitor when various complementary foods were introduced, enabling more comprehensive nutritional analyses. Bacterial species identification was based on MetaPhlAn2 quantification of bacterial species from metagenomic data and metabolomic profiles were generated using four liquid chromatography-mass spectrometry (LC-MS) methods. Results: My examinations place the previously described sequential trajectories in infant gut microbiome maturation into detailed fiber-dependent nutritional context relying on metagenomic species identification. I discovered 176 complementary food derived fiber-bacterial species associations. The majority of the associations (147, 84%) were positive whereas breastfeeding and related variables tended to be inversely associated with the same species, showing strongest inverse correlations to later trajectory species indicative of slower maturation. Both bacterial species and metabolomic profiles displayed pronounced longitudinal shifts in response to solid food fibers. Each introduction of novel dietary source of fiber associated to diversification of the microbiome revealing fiber-species specific temporal patterns. Conclusions: The longitudinal analyses highlight that sufficient fiber intake from appropriate sources during the weaning period likely function to build capacity for the species permanence in the more diverse and stable mature gut microbiome composition and function reached in later childhood.
  • Viitanen, Arto I. (2019)
    The intestinal stem cells (ISC) are responsible for the regeneration of the intestine epithelial barrier after acute injury and for the replenishment of its cells overall. How the ISC activation and resulting proliferation is controlled is complex and still under study. The ISCs of the midgut, which is the functional analogue to mammalian small intestine, are also highly responsive to changes in nutrition, and with proper methodologies it is possible to study the effects of diet on stem cell activation. The metabolic flux of the nutritional components of the diet can then shed light on which metabolic pathways are necessary for nutrient-dependent proliferation. One nutrient that has garnered interest is glutamine (Gln). It is well established that glutamine supplementation can in parenterally fed patients diminish intestinal barrier atrophy, extend the time the patient can be kept under the regime, and increase survivability of critically ill patients. Consequently, glutamine or its downstream metabolites may have stem cell activating characteristics. However, the exact regulatory mechanisms and specific effects of Gln are not well known, and studies have found contradictory results on the beneficial effects of Gln supplementation. Glutamine itself is a conditionally essential amino acid that has a variety of functions: it is an important source of nitrogen and cellular energy and contributes carbon into the tricarboxylic acid cycle (TCA) and is involved in protein and nucleotide synthesis. In this thesis, the effects of Gln supplementation on the cell populations of D. melanogaster were studied via microscopy and computational analysis. Cross-breeds of fruit fly were established to lineage label the ISC with a GAL4/UAS driver system. Confocal microscope was used to image the midguts which were then analysed with Imaris software. A novel analysis method was developed to study population changes and varying features of the cells in the midgut in an unprecedented region-by-region bulk analysis. Earlier studies into nutrient control of ISC have had limited focus within the midgut and might have consequently given a restricted view of ISC activation. This new Longitudinal Analysis of Midgut (LAM) can be utilized in a diverse set of further studies to describe conditional variation within midgut, and possibly other tissues. Gln was found to increase total cell numbers to comparable levels with well-fed midguts, and to drive limited endoreplication in enterocytes. Lineage labelled cell population grew primarily in the R3 and R4 regions of the midgut. Additionally, enteroendocrine cells (EE) were greatly increased in the posterior part of R3 but had conceivable minor increases along the whole length of the midgut. Improved nutrition was also found to affect the proportions of the midgut, presenting itself as elongated posterior and stunted anterior. Overall, the pipeline and analysis method established during this study enable more expeditious research of effects of other nutritional components and allows for study of effects of other mechanisms, for example how gene knock-downs or altered gene activities affect cell populations of the midgut.