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Cell and Tissue Research Sep 2019Living cells depend on a constant supply of energy-rich organic molecules from the environment. Small molecules pass into the interior of the cell via simple diffusion...
Living cells depend on a constant supply of energy-rich organic molecules from the environment. Small molecules pass into the interior of the cell via simple diffusion or active transport carried out by membrane bound transporters; macromolecules, or entire cells, are taken up by endocytosis/phagocytosis, and are degraded intracellularly in specialized membrane bound compartments (lysosomes). Whereas all cells are capable of transporting molecules through the membrane, the efficient procurement, digestion and uptake of nutrients have become the function of specialized cell types and organs, forming the digestive system in multicellular animals. In mammals, for example, the digestive system is comprised of glandular organs with classes of cells specialized in the secretion of enzymes for the extracellular digestion of food particles (e.g., exocrine cells of the salivary gland, pancreas), as well as other organs with absorptive function (e.g., small intestine). Numerous other cell types, such as smooth muscle cells, neurons and enteroendocrine cells, are associated with glandular cells and intestinal cells to promote the digestive process.
Topics: Animals; Biological Evolution; Digestion; Digestive System; Immune System; Phagocytosis
PubMed: 31478136
DOI: 10.1007/s00441-019-03102-x -
Nutrients Apr 2020Food ingestion induces a metered response of the digestive system. Initially, the upper digestive system reacts to process and extract meal substrates. Later, meal... (Review)
Review
Food ingestion induces a metered response of the digestive system. Initially, the upper digestive system reacts to process and extract meal substrates. Later, meal residues not absorbed in the small bowel, pass into the colon and activate the metabolism of resident microbiota. Food consumption also induces sensations that arise before ingestion (e.g., anticipatory reward), during ingestion (e.g., gustation), and most importantly, after the meal (i.e., the postprandial experience). The postprandial experience involves homeostatic sensations (satiety, fullness) with a hedonic dimension (digestive well-being, mood). The factors that determine the postprandial experience are poorly understood, despite their potential role in personalized diets and healthy eating habits. Current data suggest that the characteristics of the meal (amount, palatability, composition), the activity of the digestive system (suited processing), and the receptivity of the eater (influenced by multiple conditioning factors) may be important in this context.
Topics: Affect; Digestion; Eating; Feeding Behavior; Gastrointestinal Microbiome; Humans; Postprandial Period; Satiation; Satiety Response
PubMed: 32252402
DOI: 10.3390/nu12040986 -
Critical Reviews in Food Science and... Oct 2017Proteins are not equally digestible-their proteolytic susceptibility varies by their source and processing method. Incomplete digestion increases colonic microbial... (Review)
Review
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 in protein digestive capacity based on phenotypes, particularly disease states. To avoid putrefaction-induced intestinal inflammation, protein sources, and processing methods must be tailored to the consumer's digestive capacity. This review explores how food processing techniques alter protein digestibility and examines how physiological conditions alter digestive capacity. Possible solutions to improving digestive function or matching low digestive capacity with more digestible protein sources are explored. Beyond the ileal digestibility measurements of protein digestibility, less invasive, quicker and cheaper techniques for monitoring the extent of protein digestion and fermentation are needed to personalize protein nourishment. Biomarkers of protein digestive capacity and efficiency can be identified with the toolsets of peptidomics, metabolomics, microbial sequencing and multiplexed protein analysis of fecal and urine samples. By monitoring individual protein digestive function, the protein component of diets can be tailored via protein source and processing selection to match individual needs to minimize colonic putrefaction and, thus, optimize gut health.
Topics: Animal Feed; Diet; Digestion; Feces; Fermentation; Food Handling; Humans; Proteins
PubMed: 26713355
DOI: 10.1080/10408398.2015.1117412 -
Current Opinion in Endocrinology,... Feb 2017Provision of adequate nutrients by the gut is essential for survival and essential behaviors are linked to the proper ingestion and digestion of food. Recently, a new... (Review)
Review
PURPOSE OF REVIEW
Provision of adequate nutrients by the gut is essential for survival and essential behaviors are linked to the proper ingestion and digestion of food. Recently, a new neural connection has been reported between sensory cells of the gut epithelium and the nervous system that mediates signals from the gut to the brain.
RECENT FINDINGS
This review describes how the gut senses its environment, relays those signals to the brain, and how the brain influences the gut.
SUMMARY
This gut-brain connection provides a pathway for how the body handles food.
Topics: Animals; Brain; Connectome; Digestion; Eating; Enteroendocrine Cells; Gastrointestinal Hormones; Gastrointestinal Microbiome; Gastrointestinal Tract; Humans
PubMed: 27820704
DOI: 10.1097/MED.0000000000000299 -
Nutrients Mar 2021Food ingestion induces homeostatic sensations (satiety, fullness) with a hedonic dimension (satisfaction, changes in mood) that characterize the postprandial experience.... (Review)
Review
Food ingestion induces homeostatic sensations (satiety, fullness) with a hedonic dimension (satisfaction, changes in mood) that characterize the postprandial experience. Both types of sensation are secondary to intraluminal stimuli produced by the food itself, as well as to the activity of the digestive tract. Postprandial sensations also depend on the nutrient composition of the meal and on colonic fermentation of non-absorbed residues. Gastrointestinal function and the sensitivity of the digestive tract, i.e., perception of gut stimuli, are determined by inherent individual factors, e.g., sex, and can be modulated by different conditioning mechanisms. This narrative review examines the factors that determine perception of digestive stimuli and the postprandial experience.
Topics: Brain; Conditioning, Psychological; Digestion; Eating; Female; Gastrointestinal Microbiome; Gastrointestinal Tract; Homeostasis; Humans; Intestinal Absorption; Intestinal Diseases; Male; Meals; Postprandial Period; Satiation; Sensation; Sex Characteristics
PubMed: 33801924
DOI: 10.3390/nu13030893 -
Nestle Nutrition Institute Workshop... 2017Milk proteins are a complex and diverse source of biological activities. Beyond their function, intact milk proteins also act as carriers of encrypted functional... (Review)
Review
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. Research has now revealed that the release of these functional peptides begins within the mammary gland itself. A complex array of proteases produced in mother's milk has been shown to be active in the milk, releasing these peptides. Moreover, our recent research demonstrates that these milk proteases continue to digest milk proteins within the infant's stomach, possibly even to a larger extent than the infant's own proteases. As the neonate has relatively low digestive capacity, the activity of milk proteases in the infant may provide important assistance to digesting milk proteins. The coordinated release of these encrypted sequences is accomplished by selective proteolytic action provided by an array of native milk proteases and infant-produced enzymes. The task for scientists is now to discover the selective advantages of this protein-protease-based peptide release system.
Topics: Digestion; Female; Humans; Infant; Infant Nutritional Physiological Phenomena; Infant, Newborn; Milk Proteins; Milk, Human; Peptide Hydrolases; Proteolysis
PubMed: 28346930
DOI: 10.1159/000455250 -
Annual Review of Food Science and... Mar 2023The in vitro digestion model developed by the INFOGEST international consortium is widely used to simulate the physicochemical processes occurring inside the human... (Review)
Review
The in vitro digestion model developed by the INFOGEST international consortium is widely used to simulate the physicochemical processes occurring inside the human gastrointestinal tract (mouth, stomach, and small intestine) during the digestion of foods. In this review, we provide a brief overview of the INFOGEST method and the procedures used to measure the digestion of macronutrients (lipids, proteins, and starch), the bioaccessibility of bioactive agents (vitamins, minerals, and nutraceuticals), and the changes in the structure and physical properties of foods under gastrointestinal conditions (particle size, charge, and location). We then review the application of the INFOGEST method for monitoring the gastrointestinal fate of different kinds of foods and beverages, including dairy, egg, meat, seafood, fruit, vegetable, cereal, and emulsified products. We also discuss the application of this method for studying the digestibility of next-generation plant-based foods, such as meat, seafood, dairy, and egg analogs. Finally, the benefits and limitations of this standardized in vitro digestion model are assessed.
Topics: Humans; Digestion; Gastrointestinal Tract; Fruit; Vegetables; Dietary Supplements
PubMed: 36446138
DOI: 10.1146/annurev-food-060721-012235 -
Gastroenterology May 2019G-protein-coupled receptors (GPCRs) are the largest family of transmembrane signaling proteins. In the gastrointestinal tract, GPCRs expressed by epithelial cells sense... (Review)
Review
G-protein-coupled receptors (GPCRs) are the largest family of transmembrane signaling proteins. In the gastrointestinal tract, GPCRs expressed by epithelial cells sense contents of the lumen, and GPCRs expressed by epithelial cells, myocytes, neurons, and immune cells participate in communication among cells. GPCRs control digestion, mediate digestive diseases, and coordinate repair and growth. GPCRs are the target of more than one third of therapeutic drugs, including many drugs used to treat digestive diseases. Recent advances in structural, chemical, and cell biology research have shown that GPCRs are not static binary switches that operate from the plasma membrane to control a defined set of intracellular signals. Rather, GPCRs are dynamic signaling proteins that adopt distinct conformations and subcellular distributions when associated with different ligands and intracellular effectors. An understanding of the dynamic nature of GPCRs has provided insights into the mechanism of activation and signaling of GPCRs and has shown opportunities for drug discovery. We review the allosteric modulation, biased agonism, oligomerization, and compartmentalized signaling of GPCRs that control digestion and digestive diseases. We highlight the implications of these concepts for the development of selective and effective drugs to treat diseases of the gastrointestinal tract.
Topics: Allosteric Regulation; Digestion; Digestive System Diseases; Dimerization; Drug Discovery; Endosomes; Humans; Receptors, G-Protein-Coupled; Signal Transduction
PubMed: 30771352
DOI: 10.1053/j.gastro.2019.01.266 -
Animal : An International Journal of... Mar 2020Methane (CH4) production is a ubiquitous, apparently unavoidable side effect of fermentative fibre digestion by symbiotic microbiota in mammalian herbivores. Here, a... (Review)
Review
Methane (CH4) production is a ubiquitous, apparently unavoidable side effect of fermentative fibre digestion by symbiotic microbiota in mammalian herbivores. Here, a data compilation is presented of in vivo CH4 measurements in individuals of 37 mammalian herbivore species fed forage-only diets, from the literature and from hitherto unpublished measurements. In contrast to previous claims, absolute CH4 emissions scaled linearly to DM intake, and CH4 yields (per DM or gross energy intake) did not vary significantly with body mass. CH4 physiology hence cannot be construed to represent an intrinsic ruminant or herbivore body size limitation. The dataset does not support traditional dichotomies of CH4 emission intensity between ruminants and nonruminants, or between foregut and hindgut fermenters. Several rodent hindgut fermenters and nonruminant foregut fermenters emit CH4 of a magnitude as high as ruminants of similar size, intake level, digesta retention or gut capacity. By contrast, equids, macropods (kangaroos) and rabbits produce few CH4 and have low CH4 : CO2 ratios for their size, intake level, digesta retention or gut capacity, ruling out these factors as explanation for interspecific variation. These findings lead to the conclusion that still unidentified host-specific factors other than digesta retention characteristics, or the presence of rumination or a foregut, influence CH4 production. Measurements of CH4 yield per digested fibre indicate that the amount of CH4 produced during fibre digestion varies not only across but also within species, possibly pointing towards variation in microbiota functionality. Recent findings on the genetic control of microbiome composition, including methanogens, raise the question about the benefits methanogens provide for many (but apparently not to the same extent for all) species, which possibly prevented the evolution of the hosting of low-methanogenic microbiota across mammals.
Topics: Animals; Diet; Dietary Fiber; Digestion; Digestive System; Fermentation; Herbivory; Mammals; Methane; Rumen; Ruminants
PubMed: 32024568
DOI: 10.1017/S1751731119003161 -
Proceedings. Biological Sciences Jun 2018The digestive methods employed by amphioxus ()-both intracellular phagocytic digestion and extracellular digestion-have been discussed since 1937. Recent studies also...
The digestive methods employed by amphioxus ()-both intracellular phagocytic digestion and extracellular digestion-have been discussed since 1937. Recent studies also show that epithelial cells lining the digestive tract can express many immune genes. Here, in , using a special tissue fixation method, we show that some epithelial cells, especially those lining the large diverticulum protruding from the gut tube, phagocytize food particles directly, and can rely on this kind of phagocytic intracellular digestion to obtain energy throughout all stages of its life. Gene expression profiles suggest that diverticulum epithelial cells have functional features of both digestive cells and phagocytes. In starved , these cells accumulate endogenous digestive and hydrolytic enzymes, whereas, when sated, they express many kinds of immune genes in response to stimulation by phagocytized food particles. We also found that the distal hindgut epithelium can phagocytize food particles, but not as many. These results illustrate phagocytic intercellular digestion in , explain why digestive tract epithelial cells express typical immune genes and suggest that the main physiological function of the diverticulum is different from that of the vertebrate liver.
Topics: Animals; Digestion; Epithelial Cells; Gastrointestinal Tract; Lancelets; Phagocytes; Phagocytosis; Transcriptome
PubMed: 29875301
DOI: 10.1098/rspb.2018.0438