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Knutson KR, Whiteman ST, Alcaino C, Mercado-Perez A, Finholm I, Serlin HK, Bellampalli SS, Linden DR, Farrugia G, Beyder A. Intestinal enteroendocrine cells rely on ryanodine and IP 3 calcium store receptors for mechanotransduction. J Physiol 2023; 601:287-305. [PMID: 36428286 PMCID: PMC9840706 DOI: 10.1113/jp283383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 11/24/2022] [Indexed: 11/27/2022] Open
Abstract
Enteroendocrine cells (EECs) are specialized sensors of luminal forces and chemicals in the gastrointestinal (GI) epithelium that respond to stimulation with a release of signalling molecules such as serotonin (5-HT). For mechanosensitive EECs, force activates Piezo2 channels, which generate a very rapidly activating and inactivating (∼10 ms) cationic (Na+ , K+ , Ca2+ ) receptor current. Piezo2 receptor currents lead to a large and persistent increase in intracellular calcium (Ca2+ ) that lasts many seconds to sometimes minutes, suggesting signal amplification. However, intracellular calcium dynamics in EEC mechanotransduction remain poorly understood. The aim of this study was to determine the role of Ca2+ stores in EEC mechanotransduction. Mechanical stimulation of a human EEC cell model (QGP-1) resulted in a rapid increase in cytoplasmic Ca2+ and a slower decrease in ER stores Ca2+ , suggesting the involvement of intracellular Ca2+ stores. Comparing murine primary colonic EECs with colonocytes showed expression of intercellular Ca2+ store receptors, a similar expression of IP3 receptors, but a >30-fold enriched expression of Ryr3 in EECs. In mechanically stimulated primary EECs, Ca2+ responses decreased dramatically by emptying stores and pharmacologically blocking IP3 and RyR1/3 receptors. RyR3 genetic knockdown by siRNA led to a significant decrease in mechanosensitive Ca2+ responses and 5-HT release. In tissue, pressure-induced increase in the Ussing short circuit current was significantly decreased by ryanodine receptor blockade. Our data show that mechanosensitive EECs use intracellular Ca2+ stores to amplify mechanically induced Ca2+ entry, with RyR3 receptors selectively expressed in EECs and involved in Ca2+ signalling, 5-HT release and epithelial secretion. KEY POINTS: A population of enteroendocrine cells (EECs) are specialized mechanosensors of the gastrointestinal (GI) epithelium that respond to mechanical stimulation with the release of important signalling molecules such as serotonin. Mechanical activation of these EECs leads to an increase in intracellular calcium (Ca2+ ) with a longer duration than the stimulus, suggesting intracellular Ca2+ signal amplification. In this study, we profiled the expression of intracellular Ca2+ store receptors and found an enriched expression of the intracellular Ca2+ receptor Ryr3, which contributed to the mechanically evoked increases in intracellular calcium, 5-HT release and epithelial secretion. Our data suggest that mechanosensitive EECs rely on intracellular Ca2+ stores and are selective in their use of Ryr3 for amplification of intracellular Ca2+ . This work advances our understanding of EEC mechanotransduction and may provide novel diagnostic and therapeutic targets for GI motility disorders.
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Affiliation(s)
- Kaitlyn R. Knutson
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Sara T. Whiteman
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Constanza Alcaino
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Arnaldo Mercado-Perez
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
- Medical Scientist Training Program (MSTP), Mayo Clinic, Rochester, Minnesota
| | - Isabelle Finholm
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Hannah K. Serlin
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Shreya S. Bellampalli
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
- Medical Scientist Training Program (MSTP), Mayo Clinic, Rochester, Minnesota
| | - David R. Linden
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Gianrico Farrugia
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Division of Gastroenterology &Hepatology, Department of Medicine, Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Arthur Beyder
- Enteric Neuroscience Program (ENSP), Mayo Clinic, Rochester, Minnesota
- Division of Gastroenterology &Hepatology, Department of Medicine, Mayo Clinic, Rochester, Minnesota
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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Abstract
Glucagon-like peptide-1 (GLP-1) is an enterohormone with a key role in several processes controlling body homeostasis, including glucose homeostasis and food intake regulation. It is secreted by the intestinal cells in response to nutrients, such as glucose, fat and amino acids. In the present review, we analyse the effect of protein on GLP-1 secretion and clearance. We review the literature on the GLP-1 secretory effects of protein and protein hydrolysates, and the mechanisms through which they exert these effects. We also review the studies on protein from different sources that has inhibitory effects on dipeptidyl peptidase-4 (DPP4), the enzyme responsible for GLP-1 inactivation, with particular emphasis on specific sources and treatments, and the gaps there still are in knowledge. There is evidence that the protein source and the hydrolytic processing applied to them can influence the effects on GLP-1 signalling. The gastrointestinal digestion of proteins, for example, significantly changes their effectiveness at modulating this enterohormone secretion in both in vivo and in vitro studies. Nevertheless, little information is available regarding human studies and more research is required to understand their potential as regulators of glucose homeostasis.
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3
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Hajishafiee M, Elovaris RA, Jones KL, Heilbronn LK, Horowitz M, Poppitt SD, Feinle-Bisset C. Effects of intragastric administration of L-tryptophan on the glycaemic response to a nutrient drink in men with type 2 diabetes - impacts on gastric emptying, glucoregulatory hormones and glucose absorption. Nutr Diabetes 2021; 11:3. [PMID: 33414406 PMCID: PMC7791097 DOI: 10.1038/s41387-020-00146-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 12/01/2020] [Accepted: 12/07/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The rate of gastric emptying and glucoregulatory hormones are key determinants of postprandial glycaemia. Intragastric administration of L-tryptophan slows gastric emptying and reduces the glycaemic response to a nutrient drink in lean individuals and those with obesity. We investigated whether tryptophan decreases postprandial glycaemia and slows gastric emptying in type 2 diabetes (T2D). METHODS Twelve men with T2D (age: 63 ± 2 years, HbA1c: 49.7 ± 2.5 mmol/mol, BMI: 30 ± 1 kg/m2) received, on three separate occasions, 3 g ('Trp-3') or 1.5 g ('Trp-1.5') tryptophan, or control (0.9% saline), intragastrically, in randomised, double-blind fashion, 30 min before a mixed-nutrient drink (500 kcal, 74 g carbohydrates), containing 3 g 3-O-methyl-D-glucose (3-OMG) to assess glucose absorption. Venous blood samples were obtained at baseline, after tryptophan, and for 2 h post-drink for measurements of plasma glucose, C-peptide, glucagon and 3-OMG. Gastric emptying of the drink was quantified using two-dimensional ultrasound. RESULTS Tryptophan alone stimulated C-peptide (P = 0.002) and glucagon (P = 0.04), but did not affect fasting glucose. In response to the drink, Trp-3 lowered plasma glucose from t = 15-30 min and from t = 30-45 min compared with control and Trp-1.5, respectively (both P < 0.05), with no differences in peak glucose between treatments. Gastric emptying tended to be slower after Trp-3, but not Trp-1.5, than control (P = 0.06). Plasma C-peptide, glucagon and 3-OMG increased on all days, with no major differences between treatments. CONCLUSIONS In people with T2D, intragastric administration of 3 g tryptophan modestly slows gastric emptying, associated with a delayed rise, but not an overall lowering of, postprandial glucose.
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Affiliation(s)
- Maryam Hajishafiee
- Adelaide Medical School and Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia
| | - Rachel A Elovaris
- Adelaide Medical School and Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia
| | - Karen L Jones
- Adelaide Medical School and Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia
| | - Leonie K Heilbronn
- Adelaide Medical School and Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia
- Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Michael Horowitz
- Adelaide Medical School and Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia
- Endocrine and Metabolic Unit, Royal Adelaide Hospital, Adelaide, Australia
| | - Sally D Poppitt
- Human Nutrition Unit, School of Biological Sciences, Department of Medicine, University of Auckland, Auckland, New Zealand
| | - Christine Feinle-Bisset
- Adelaide Medical School and Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia.
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4
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Kaelberer MM, Rupprecht LE, Liu WW, Weng P, Bohórquez DV. Neuropod Cells: The Emerging Biology of Gut-Brain Sensory Transduction. Annu Rev Neurosci 2020; 43:337-353. [PMID: 32101483 PMCID: PMC7573801 DOI: 10.1146/annurev-neuro-091619-022657] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Guided by sight, scent, texture, and taste, animals ingest food. Once ingested, it is up to the gut to make sense of the food's nutritional value. Classic sensory systems rely on neuroepithelial circuits to convert stimuli into signals that guide behavior. However, sensation of the gut milieu was thought to be mediated only by the passive release of hormones until the discovery of synapses in enteroendocrine cells. These are gut sensory epithelial cells, and those that form synapses are referred to as neuropod cells. Neuropod cells provide the foundation for the gut to transduce sensory signals from the intestinal milieu to the brain through fast neurotransmission onto neurons, including those of the vagus nerve. These findings have sparked a new field of exploration in sensory neurobiology-that of gut-brain sensory transduction.
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Affiliation(s)
- Melanie Maya Kaelberer
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA;
| | - Laura E Rupprecht
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA;
| | - Winston W Liu
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA;
- School of Medicine, Duke University, Durham, North Carolina 27710, USA
| | - Peter Weng
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA;
- School of Medicine, Duke University, Durham, North Carolina 27710, USA
| | - Diego V Bohórquez
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA;
- Department of Neurobiology, Duke University, Durham, North Carolina 27710, USA
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5
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Kaelberer MM, Rupprecht LE, Liu WW, Weng P, Bohórquez DV. Neuropod Cells: The Emerging Biology of Gut-Brain Sensory Transduction. Annu Rev Neurosci 2020. [PMID: 32101483 DOI: 10.1146/annurev‐neuro‐091619‐022657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Guided by sight, scent, texture, and taste, animals ingest food. Once ingested, it is up to the gut to make sense of the food's nutritional value. Classic sensory systems rely on neuroepithelial circuits to convert stimuli into signals that guide behavior. However, sensation of the gut milieu was thought to be mediated only by the passive release of hormones until the discovery of synapses in enteroendocrine cells. These are gut sensory epithelial cells, and those that form synapses are referred to as neuropod cells. Neuropod cells provide the foundation for the gut to transduce sensory signals from the intestinal milieu to the brain through fast neurotransmission onto neurons, including those of the vagus nerve. These findings have sparked a new field of exploration in sensory neurobiology-that of gut-brain sensory transduction.
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Affiliation(s)
- Melanie Maya Kaelberer
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA;
| | - Laura E Rupprecht
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA;
| | - Winston W Liu
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA; .,School of Medicine, Duke University, Durham, North Carolina 27710, USA
| | - Peter Weng
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA; .,School of Medicine, Duke University, Durham, North Carolina 27710, USA
| | - Diego V Bohórquez
- Gut-Brain Neurobiology Laboratory, Department of Medicine, School of Medicine, Duke University, Durham, North Carolina 27710, USA; .,Department of Neurobiology, Duke University, Durham, North Carolina 27710, USA
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6
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Roura E, Depoortere I, Navarro M. Review: Chemosensing of nutrients and non-nutrients in the human and porcine gastrointestinal tract. Animal 2019; 13:2714-2726. [PMID: 31387651 DOI: 10.1017/s1751731119001794] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The gastrointestinal tract (GIT) is an interface between the external and internal milieus that requires continuous monitoring for nutrients or pathogens and toxic chemicals. The study of the physiological/molecular mechanisms, mediating the responses to the monitoring of the GIT contents, has been referred to as chemosensory science. While most of the progress in this area of research has been obtained in laboratory rodents and humans, significant steps forward have also been reported in pigs. The objective of this review was to update the current knowledge on nutrient chemosensing in pigs in light of recent advances in humans and laboratory rodents. A second objective relates to informing the existence of nutrient sensors with their functionality, particularly linked to the gut peptides relevant to the onset/offset of appetite. Several cell types of the intestinal epithelium such as Paneth, goblet, tuft and enteroendocrine cells (EECs) contain subsets of chemosensory receptors also found on the tongue as part of the taste system. In particular, EECs show specific co-expression patterns between nutrient sensors and/or transceptors (transport proteins with sensing functions) and anorexigenic hormones such as cholecystokinin (CCK), peptide tyrosine tyrosine (PYY) or glucagon-like peptide-1 (GLP-1), amongst others. In addition, the administration of bitter compounds has an inhibitory effect on GIT motility and on appetite through GLP-1-, CCK-, ghrelin- and PYY-labelled EECs in the human small intestine and colon. Furthermore, the mammalian chemosensory system is the target of some bacterial metabolites. Recent studies on the human microbiome have discovered that commensal bacteria have developed strategies to stimulate chemosensory receptors and trigger host cellular functions. Finally, the study of gene polymorphisms related to nutrient sensors explains differences in food choices, food intake and appetite between individuals.
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Affiliation(s)
- E Roura
- Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, Queensland, Australia
| | - I Depoortere
- Translational Research Center for Gastrointestinal Disorders, Gut Peptide Research Lab, University of Leuven, Belgium
| | - M Navarro
- Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, Queensland, Australia
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7
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Menchini RJ, Chaudhry FA. Multifaceted regulation of the system A transporter Slc38a2 suggests nanoscale regulation of amino acid metabolism and cellular signaling. Neuropharmacology 2019; 161:107789. [PMID: 31574264 DOI: 10.1016/j.neuropharm.2019.107789] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 09/16/2019] [Accepted: 09/20/2019] [Indexed: 02/07/2023]
Abstract
Amino acids are essential for cellular protein synthesis, growth, metabolism, signaling and in stress responses. Cell plasma membranes harbor specialized transporters accumulating amino acids to support a variety of cellular biochemical pathways. Several transporters for neutral amino acids have been characterized. However, Slc38a2 (also known as SA1, SAT2, ATA2, SNAT2) representing the classical transport system A activity stands in a unique position: Being a secondarily active transporter energized by the electrochemical gradient of Na+, it creates steep concentration gradients for amino acids such as glutamine: this may subsequently drive the accumulation of additional neutral amino acids through exchange via transport systems ASC and L. Slc38a2 is ubiquitously expressed, yet in a cell-specific manner. In this review, we show that Slc38a2 is regulated at the transcriptional and translational levels as well as by ions and proteins through direct interactions. We describe how Slc38a2 senses amino acid availability and passes this onto intracellular signaling pathways and how it regulates protein synthesis, cellular proliferation and apoptosis through the mechanistic (mammalian) target of rapamycin (mTOR) and general control nonderepressible 2 (GCN2) pathways. Furthermore, we review how this extensively regulated transporter contributes to cellular osmoadaptation and how it is regulated by endoplasmic reticulum stress and various hormonal stimuli to promote cellular metabolism, cellular signaling and cell survival. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
| | - Farrukh Abbas Chaudhry
- Department of Molecular Medicine, University of Oslo, Oslo, Norway; Department of Plastic and Reconstructive Surgery, Oslo University Hospital, Oslo, Norway
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8
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Goldspink DA, Reimann F, Gribble FM. Models and Tools for Studying Enteroendocrine Cells. Endocrinology 2018; 159:3874-3884. [PMID: 30239642 PMCID: PMC6215081 DOI: 10.1210/en.2018-00672] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Accepted: 09/05/2018] [Indexed: 12/14/2022]
Abstract
Gut hormones produced by gastrointestinal enteroendocrine cells modulate key physiological processes including glucose homeostasis and food intake, making them potential therapeutic candidates to treat obesity and diabetes. Understanding the function of enteroendocrine cells and the molecular mechanisms driving hormone production is a key step toward mobilizing endogenous hormone reserves in the gut as a therapeutic strategy. In this review, we will discuss the variety of ex vivo and in vitro model systems driving this research and their contributions to our current understanding of nutrient-sensing mechanisms in enteroendocrine cells.
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Affiliation(s)
- Deborah A Goldspink
- Metabolic Research Laboratories, University of Cambridge, Cambridge, United Kingdom
| | - Frank Reimann
- Metabolic Research Laboratories, University of Cambridge, Cambridge, United Kingdom
| | - Fiona M Gribble
- Metabolic Research Laboratories, University of Cambridge, Cambridge, United Kingdom
- Correspondence: Fiona M. Gribble, DPhil, BM, BCh, Institute of Metabolic Science, University of Cambridge, Addenbrooke’s Hospital, Cambridge CB2 0QQ, United Kingdom. E-mail:
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9
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Abstract
Obesity is a major global health issue. High-protein diets have been shown to be associated with weight loss and satiety. The precise mechanism by which protein-rich diets promote weight loss remains unclear. Evidence suggests amino acids, formed as a consequence of protein digestion, are sensed by specific receptors on L-cells in the gastrointestinal (GI) tract. These L-cells respond by secreting gut hormones that subsequently induce satiety. In recent years, the calcium-sensing receptor has been identified in several cells of the GI tract, including L-cells, and suggested to sense specific amino acids. This review evaluates the evidence for protein-rich diets in inducing weight loss and how the calcium-sensing receptor may be implicated in this phenomenon. Commandeering the mechanisms by which elements of a protein-rich diet suppress appetite may provide another successful avenue for developing anti-obesity drugs.
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Affiliation(s)
- Utkarsh Ojha
- Faculty of Medicine, Imperial College School of Medicine, Imperial College London, London, UK
- Correspondence: Utkarsh Ojha, Faculty of Medicine, Imperial College School of Medicine, Sir Alexander Fleming Building, Imperial College London, Exhibition Road, London SW7 2AZ, UK, Tel +44 775 966 7685, Email
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10
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Baghcheghi Y, Salmani H, Beheshti F, Hosseini M. Contribution of Brain Tissue Oxidative Damage in Hypothyroidism-associated Learning and Memory Impairments. Adv Biomed Res 2017; 6:59. [PMID: 28584813 PMCID: PMC5450450 DOI: 10.4103/2277-9175.206699] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The brain is a critical target organ for thyroid hormones, and modifications in memory and cognition happen with thyroid dysfunction. The exact mechanisms underlying learning and memory impairments due to hypothyroidism have not been understood yet. Therefore, this review was aimed to compress the results of previous studies which have examined the contribution of brain tissues oxidative damage in hypothyroidism-associated learning and memory impairments.
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Affiliation(s)
- Yousef Baghcheghi
- Student Research Committee, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hossein Salmani
- Department of Physiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Farimah Beheshti
- Neurogenic Inflammation Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mahmoud Hosseini
- Neurocognitive Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
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11
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Jyotaki M, Sanematsu K, Shigemura N, Yoshida R, Ninomiya Y. Leptin suppresses sweet taste responses of enteroendocrine STC-1 cells. Neuroscience 2016; 332:76-87. [PMID: 27353597 DOI: 10.1016/j.neuroscience.2016.06.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 06/17/2016] [Accepted: 06/22/2016] [Indexed: 12/26/2022]
Abstract
Leptin is an important hormone that regulates food intake and energy homeostasis by acting on central and peripheral targets. In the gustatory system, leptin is known to selectively suppress sweet responses by inhibiting the activation of sweet sensitive taste cells. Sweet taste receptor (T1R2+T1R3) is also expressed in gut enteroendocrine cells and contributes to nutrient sensing, hormone release and glucose absorption. Because of the similarities in expression patterns between enteroendocrine and taste receptor cells, we hypothesized that they may also share similar mechanisms used to modify/regulate the sweet responsiveness of these cells by leptin. Here, we used mouse enteroendocrine cell line STC-1 and examined potential effect of leptin on Ca(2+) responses of STC-1 cells to various taste compounds. Ca(2+) responses to sweet compounds in STC-1 cells were suppressed by a rodent T1R3 inhibitor gurmarin, suggesting the involvement of T1R3-dependent receptors in detection of sweet compounds. Responses to sweet substances were suppressed by ⩾1ng/ml leptin without affecting responses to bitter, umami and salty compounds. This effect was inhibited by a leptin antagonist (mutant L39A/D40A/F41A) and by ATP gated K(+) (KATP) channel closer glibenclamide, suggesting that leptin affects sweet taste responses of enteroendocrine cells via activation of leptin receptor and KATP channel expressed in these cells. Moreover, leptin selectively inhibited sweet-induced but not bitter-induced glucagon-like peptide-1 (GLP-1) secretion from STC-1 cells. These results suggest that leptin modulates sweet taste responses of enteroendocrine cells to regulate nutrient sensing, hormone release and glucose absorption in the gut.
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Affiliation(s)
- Masafumi Jyotaki
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan; Monell Chemical Senses Center, Philadelphia, PA, United States
| | - Keisuke Sanematsu
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan; OBT Research Center, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Yuzo Ninomiya
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Monell Chemical Senses Center, Philadelphia, PA, United States.
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12
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Alamshah A, McGavigan AK, Spreckley E, Kinsey-Jones JS, Amin A, Tough IR, O'Hara HC, Moolla A, Banks K, France R, Hyberg G, Norton M, Cheong W, Lehmann A, Bloom SR, Cox HM, Murphy KG. L-arginine promotes gut hormone release and reduces food intake in rodents. Diabetes Obes Metab 2016; 18:508-18. [PMID: 26863991 PMCID: PMC4982043 DOI: 10.1111/dom.12644] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 01/31/2016] [Accepted: 02/07/2016] [Indexed: 12/14/2022]
Abstract
AIMS To investigate the anorectic effect of L-arginine (L-Arg) in rodents. METHODS We investigated the effects of L-Arg on food intake, and the role of the anorectic gut hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), the G-protein-coupled receptor family C group 6 member A (GPRC6A) and the vagus nerve in mediating these effects in rodents. RESULTS Oral gavage of L-Arg reduced food intake in rodents, and chronically reduced cumulative food intake in diet-induced obese mice. Lack of the GPRC6A in mice and subdiaphragmatic vagal deafferentation in rats did not influence these anorectic effects. L-Arg stimulated GLP-1 and PYY release in vitro and in vivo. Pharmacological blockade of GLP-1 and PYY receptors did not influence the anorectic effect of L-Arg. L-Arg-mediated PYY release modulated net ion transport across the gut mucosa. Intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) administration of L-Arg suppressed food intake in rats. CONCLUSIONS L-Arg reduced food intake and stimulated gut hormone release in rodents. The anorectic effect of L-Arg is unlikely to be mediated by GLP-1 and PYY, does not require GPRC6A signalling and is not mediated via the vagus. I.c.v. and i.p. administration of L-Arg suppressed food intake in rats, suggesting that L-Arg may act on the brain to influence food intake. Further work is required to determine the mechanisms by which L-Arg suppresses food intake and its utility in the treatment of obesity.
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MESH Headings
- Animals
- Appetite Depressants/administration & dosage
- Appetite Depressants/adverse effects
- Appetite Depressants/pharmacology
- Appetite Depressants/therapeutic use
- Arginine/administration & dosage
- Arginine/adverse effects
- Arginine/therapeutic use
- Cells, Cultured
- Dietary Supplements/adverse effects
- Energy Intake/drug effects
- Energy Metabolism/drug effects
- Gastrointestinal Agents/administration & dosage
- Gastrointestinal Agents/adverse effects
- Gastrointestinal Agents/pharmacology
- Gastrointestinal Agents/therapeutic use
- Glucagon-Like Peptide 1/agonists
- Glucagon-Like Peptide 1/blood
- Glucagon-Like Peptide 1/metabolism
- In Vitro Techniques
- Injections, Intraperitoneal
- Injections, Intraventricular
- Intestinal Mucosa/cytology
- Intestinal Mucosa/drug effects
- Intestinal Mucosa/metabolism
- Intestinal Mucosa/pathology
- Male
- Mice, Inbred C57BL
- Mice, Knockout
- Obesity/diet therapy
- Obesity/drug therapy
- Obesity/metabolism
- Obesity/pathology
- Peptide YY/agonists
- Peptide YY/blood
- Peptide YY/metabolism
- Random Allocation
- Rats, Wistar
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/antagonists & inhibitors
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Weight Loss/drug effects
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Affiliation(s)
- A Alamshah
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - A K McGavigan
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - E Spreckley
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - J S Kinsey-Jones
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - A Amin
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - I R Tough
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - H C O'Hara
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - A Moolla
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - K Banks
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - R France
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - G Hyberg
- AstraZeneca R&D, Mölndal, Sweden
| | - M Norton
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - W Cheong
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - A Lehmann
- AstraZeneca R&D, Mölndal, Sweden
- Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - S R Bloom
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - H M Cox
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - K G Murphy
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
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13
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Liu J, Yu K, Zhu W. Amino acid sensing in the gut and its mediation in gut-brain signal transduction. ACTA ACUST UNITED AC 2016; 2:69-73. [PMID: 29767064 PMCID: PMC5940996 DOI: 10.1016/j.aninu.2016.03.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 03/24/2016] [Accepted: 03/25/2016] [Indexed: 11/28/2022]
Abstract
Animal gastrointestinal tract is not only a digestive organ, but also a nutrient sensing organ which detects luminal nutrient and thus can regulate food intake. There are many amino acid sensing receptors and transporters in the gut. Amino acids sensing by these receptors and transporters can stimulate the intestinal endocrine cells to release a variety of gut hormones. These hormones trigger a series of physiological effects via the nerve system. This review summarized the recent advance on the amino acid sensing receptors and transporters in the gastrointestinal tract, the gut hormones released from the intestinal endocrine cells and the hormones-induced signal transduction between the gut and brain. A better understanding of these processes may help to gain further insight into the specific role of amino acids in digestion and provide guidelines in developing strategy for the better use of amino acids in the diet.
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Affiliation(s)
- Jing Liu
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Kaifan Yu
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Weiyun Zhu
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
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14
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Li AJ, Wang Q, Dinh TT, Simasko SM, Ritter S. Mercaptoacetate blocks fatty acid-induced GLP-1 secretion in male rats by directly antagonizing GPR40 fatty acid receptors. Am J Physiol Regul Integr Comp Physiol 2016; 310:R724-32. [PMID: 26791830 DOI: 10.1152/ajpregu.00387.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 01/19/2016] [Indexed: 12/13/2022]
Abstract
Mercaptoacetate (MA) is an orexigenic agent reported to block fatty acid (FA) oxidation. Recently, however, we reported evidence from isolated nodose ganglion neurons that MA antagonizes the G protein-coupled long- and medium-chain FA receptor GPR40. GPR40 mediates FA-induced secretion of the satietogenic incretin peptide glucagon-like peptide 1 (GLP-1), by enteroendocrine L cells, as well as FA-induced enhancement of glucose-stimulated insulin secretion. Our results in cultured nodose neurons suggest that MA would also block GPR40 in enteroendocrine cells controlling GLP-1 secretion. If so, this would suggest an alternative mechanism by which MA increases food intake. We tested the hypothesis that MA blocks FA-induced GLP-1 secretion in vitro using cultured STC-1 cells (a murine enteroendocrine cell line) and in vivo in adult male rats. In vitro, MA blocked the increase in both cytosolic Ca(2+)and GLP-1 release stimulated by FAs and also reduced (but less effectively) the response of STC-1 cells to grifolic acid, a partial agonist of the GPR120 FA receptor. In vivo, MA reduced GLP-1 secretion following olive oil gavage while also increasing glucose and decreasing insulin levels. The carnitine palmatoyltransferase 1 antagonist etomoxir did not alter these responses. Results indicate that MA's actions, including its orexigenic effect, are mediated by GPR40 (and possibly GPR120) receptor antagonism and not by blockade of fat oxidation, as previously believed. Analysis of MA's interaction with GPR40 may facilitate understanding of the multiple functions of this receptor and the manner in which FAs participate in the control of hunger and satiety.
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Affiliation(s)
- Ai-Jun Li
- Programs in Neuroscience, Washington State University, Pullman, Washington
| | - Qing Wang
- Programs in Neuroscience, Washington State University, Pullman, Washington
| | - Thu T Dinh
- Programs in Neuroscience, Washington State University, Pullman, Washington
| | - Steve M Simasko
- Programs in Neuroscience, Washington State University, Pullman, Washington
| | - Sue Ritter
- Programs in Neuroscience, Washington State University, Pullman, Washington
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15
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Chemosensory signalling pathways involved in sensing of amino acids by the ghrelin cell. Sci Rep 2015; 5:15725. [PMID: 26510380 PMCID: PMC4625164 DOI: 10.1038/srep15725] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 10/01/2015] [Indexed: 01/06/2023] Open
Abstract
Taste receptors on enteroendocrine cells sense nutrients and transmit signals that control gut hormone release. This study aimed to investigate the amino acid (AA) sensing mechanisms of the ghrelin cell in a gastric ghrelinoma cell line, tissue segments and mice. Peptone and specific classes of amino acids stimulate ghrelin secretion in the ghrelinoma cell line. Sensing of L-Phe occurs via the CaSR, monosodium glutamate via the TAS1R1-TAS1R3 while L-Ala and peptone act via 2 different amino acid taste receptors: CaSR &TAS1R1-TAS1R3 and CaSR &GPRC6A, respectively. The stimulatory effect of peptone on ghrelin release was mimicked ex vivo in gastric but not in jejunal tissue segments, where peptone inhibited ghrelin release. The latter effect could not be blocked by receptor antagonists for CCK, GLP-1 or somatostatin. In vivo, plasma ghrelin levels were reduced both upon intragastric (peptone or L-Phe) or intravenous (L-Phe) administration, indicating that AA- sensing is not polarized and is due to inhibition of ghrelin release from the stomach or duodenum respectively. In conclusion, functional AA taste receptors regulate AA-induced ghrelin release in vitro. The effects differ between stomach and jejunum but these local nutrient sensing mechanisms are overruled in vivo by indirect mechanisms inhibiting ghrelin release.
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16
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Jiang Y, Rose AJ, Sijmonsma TP, Bröer A, Pfenninger A, Herzig S, Schmoll D, Bröer S. Mice lacking neutral amino acid transporter B(0)AT1 (Slc6a19) have elevated levels of FGF21 and GLP-1 and improved glycaemic control. Mol Metab 2015; 4:406-17. [PMID: 25973388 PMCID: PMC4421019 DOI: 10.1016/j.molmet.2015.02.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 02/05/2015] [Accepted: 02/09/2015] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVE Type 2 diabetes arises from insulin resistance of peripheral tissues followed by dysfunction of β-cells in the pancreas due to metabolic stress. Both depletion and supplementation of neutral amino acids have been discussed as strategies to improve insulin sensitivity. Here we characterise mice lacking the intestinal and renal neutral amino acid transporter B(0)AT1 (Slc6a19) as a model to study the consequences of selective depletion of neutral amino acids. METHODS Metabolic tests, analysis of metabolite levels and signalling pathways were used to characterise mice lacking the intestinal and renal neutral amino acid transporter B(0)AT1 (Slc6a19). RESULTS Reduced uptake of neutral amino acids in the intestine and loss of neutral amino acids in the urine causes an overload of amino acids in the lumen of the intestine and reduced systemic amino acid availability. As a result, higher levels of glucagon-like peptide 1 (GLP-1) are produced by the intestine after a meal, while the liver releases the starvation hormone fibroblast growth factor 21 (FGF21). The combination of these hormones generates a metabolic phenotype that is characterised by efficient removal of glucose, particularly by the heart, reduced adipose tissue mass, browning of subcutaneous white adipose tissue, enhanced production of ketone bodies and reduced hepatic glucose output. CONCLUSIONS Reduced neutral amino acid availability improves glycaemic control. The epithelial neutral amino acid transporter B(0)AT1 could be a suitable target to treat type 2 diabetes.
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Affiliation(s)
- Yang Jiang
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Adam J. Rose
- Joint Research Division Molecular Metabolic Control, German Cancer Research Center, Center for Molecular Biology, Heidelberg University and Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Tjeerd P. Sijmonsma
- Joint Research Division Molecular Metabolic Control, German Cancer Research Center, Center for Molecular Biology, Heidelberg University and Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Angelika Bröer
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Anja Pfenninger
- Sanofi-Aventis Deutschland GmbH, Industriepark Hoechst, Frankfurt am Main 65926, Germany
| | - Stephan Herzig
- Joint Research Division Molecular Metabolic Control, German Cancer Research Center, Center for Molecular Biology, Heidelberg University and Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Dieter Schmoll
- Sanofi-Aventis Deutschland GmbH, Industriepark Hoechst, Frankfurt am Main 65926, Germany
| | - Stefan Bröer
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
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17
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González-Abuín N, Martínez-Micaelo N, Blay M, Green BD, Pinent M, Ardévol A. Grape-seed procyanidins modulate cellular membrane potential and nutrient-induced GLP-1 secretion in STC-1 cells. Am J Physiol Cell Physiol 2013; 306:C485-92. [PMID: 24371039 DOI: 10.1152/ajpcell.00355.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Grape-seed procyanidin extracts (GSPE) modulate glucose homeostasis, and it was suggested that GSPE may achieve this by enhancing the secretion of incretin hormones such as glucagon-like peptide-1 (GLP-1). Therefore, the aim of the present study is to examine in detail the effects of GSPE on intestinal endocrine cells (STC-1). GSPE was found to modulate plasma membrane potential in enteroendocrine cells, inducing depolarization at low concentrations (0.05 mg/l) and hyperpolarization at high concentrations (50 mg/l), and surprisingly this was also accompanied by suppressed GLP-1 secretion. Furthermore, how GSPE affects STC-1 cells under nutrient-stimulated conditions (i.e., glucose, linoleic acid, and l-proline) was also explored, and we found that the higher GSPE concentration was effective in limiting membrane depolarization and reducing GLP-1 secretion. Next, it was also examined whether GSPE affected mitochondrial membrane potential, and it was found that this too is altered by GSPE; however, this does not appear to explain the observed effects on plasma membrane potential and GLP-1 secretion. In conclusion, our results show that grape-seed procyanidins modulate cellular membrane potential and nutrient-induced enteroendocrine hormone secretion in STC-1 cells.
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Affiliation(s)
- Noemi González-Abuín
- Departament de Bioquímica i Biotecnologia, Universitat Rovira i Virgili, Tarragona, Spain; and
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18
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The SLC38 family of sodium-amino acid co-transporters. Pflugers Arch 2013; 466:155-72. [PMID: 24193407 DOI: 10.1007/s00424-013-1393-y] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/16/2013] [Accepted: 10/20/2013] [Indexed: 12/13/2022]
Abstract
Transporters of the SLC38 family are found in all cell types of the body. They mediate Na(+)-dependent net uptake and efflux of small neutral amino acids. As a result they are particularly expressed in cells that grow actively, or in cells that carry out significant amino acid metabolism, such as liver, kidney and brain. SLC38 transporters occur in membranes that face intercellular space or blood vessels, but do not occur in the apical membrane of absorptive epithelia. In the placenta, they play a significant role in the transfer of amino acids to the foetus. Members of the SLC38 family are highly regulated in response to amino acid depletion, hypertonicity and hormonal stimuli. SLC38 transporters play an important role in amino acid signalling and have been proposed to act as transceptors independent of their transport function. The structure of SLC38 transporters is characterised by the 5 + 5 inverted repeat fold, which is observed in a wide variety of transport proteins.
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19
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Cattani D, Goulart PB, Cavalli VLDLO, Winkelmann-Duarte E, Dos Santos AQ, Pierozan P, de Souza DF, Woehl VM, Fernandes MC, Silva FRMB, Gonçalves CA, Pessoa-Pureur R, Zamoner A. Congenital hypothyroidism alters the oxidative status, enzyme activities and morphological parameters in the hippocampus of developing rats. Mol Cell Endocrinol 2013; 375:14-26. [PMID: 23693027 DOI: 10.1016/j.mce.2013.05.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 04/17/2013] [Accepted: 05/01/2013] [Indexed: 11/23/2022]
Abstract
Congenital hypothyroidism is associated with delay in cell migration and proliferation in brain tissue, impairment of synapse formation, misregulation of neurotransmitters, hypomyelination and mental retardation. However, the mechanisms underlying the neuropsychological deficits observed in congenital hypothyroidism are not completely understood. In the present study we proposed a mechanism by which hypothyroidism leads to hippocampal neurotoxicity. Congenital hypothyroidism induces c-Jun-N-terminal kinase (JNK) pathway activation leading to hyperphosphorylation of the glial fibrillary acidic protein (GFAP), vimentin and neurofilament subunits from hippocampal astrocytes and neurons, respectively. Moreover, hyperphosphorylation of the cytoskeletal proteins was not reversed by T3 and poorly reversed by T4. In addition, congenital hypothyroidism is associated with downregulation of astrocyte glutamate transporters (GLAST and GLT-1) leading to decreased glutamate uptake and subsequent influx of Ca(2+) through N-methyl-D-aspartate (NMDA) receptors. The Na(+)-coupled (14)C-α-methyl-amino-isobutyric acid ((14)C-MeAIB) accumulation into hippocampal cells also might cause an increase in the intracellular Ca(2+) concentration by opening voltage-dependent calcium channels (VDCC). The excessive influx of Ca(2+) through NMDA receptors and VDCCs might lead to an overload of Ca(2+) within the cells, which set off glutamate excitotoxicity and oxidative stress. The inhibited acetylcholinesterase (AChE) activity might also induce Ca(2+) influx. The inhibited glucose-6-phosphate dehydrogenase (G6PD) and gamma-glutamyl transferase (GGT) activities, associated with altered glutamate and neutral amino acids uptake could somehow affect the GSH turnover, the antioxidant defense system, as well as the glutamate-glutamine cycle. Reduced levels of S100B and glial fibrillary acidic protein (GFAP) take part of the hypothyroid condition, suggesting a compromised astroglial/neuronal neurometabolic coupling which is probably related to the neurotoxic damage in hypothyroid brain.
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Affiliation(s)
- Daiane Cattani
- Departamento de Bioquímica, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
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20
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Hamdani EH, Gudbrandsen M, Bjørkmo M, Chaudhry FA. The system N transporter SN2 doubles as a transmitter precursor furnisher and a potential regulator of NMDA receptors. Glia 2012; 60:1671-83. [PMID: 22821889 DOI: 10.1002/glia.22386] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 06/14/2012] [Accepted: 06/15/2012] [Indexed: 12/28/2022]
Abstract
Activation of NMDA receptor requires two co-agonists, glutamate and glycine. Despite its intrinsic role in brain functions molecular mechanisms involved in glutamate replenishment and identification of the origin of glycine have eluded characterization. We have performed direct measurements of glycine flux by SN2 (Slc38a5; also known as SNAT5), executed extensive electrophysiological characterization as well as implemented ratiometric analyses to show that SN2 transport resembles SN1 in mechanism but differ in functional implications. We report that rat SN2 mediates electroneutral and bidirectional transport of glutamine and glycine at perisynaptic astroglial membranes. Sophisticated coupled and uncoupled movements of H(+) differentially associate with glutamine and glycine transport by SN2 and regulate pH(i) and the release mode of the transporter. Consequently, SN2 doubles as a transmitter precursor furnisher and a potential regulator of NMDA receptors.
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Affiliation(s)
- El Hassan Hamdani
- The Biotechnology Center and Center for Molecular Biology and Neuroscience, University of Oslo, Blindern, Oslo, Norway
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21
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Korotaeva KN, Tsirkin VI, Vyaznikov VA. Positive Inotropic Effect of Tyrosine, Histidine, and Tryptophan in Experiments on Isolated Human Myocardium. Bull Exp Biol Med 2012; 153:51-3. [DOI: 10.1007/s10517-012-1640-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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22
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Moran-Ramos S, Tovar AR, Torres N. Diet: friend or foe of enteroendocrine cells--how it interacts with enteroendocrine cells. Adv Nutr 2012; 3:8-20. [PMID: 22332097 PMCID: PMC3262619 DOI: 10.3945/an.111.000976] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Gut hormones play a key role in the regulation of food intake, energy expenditure, glucose homeostasis, lipid metabolism, and a wide range of metabolic functions in response to food ingestion. These hormones are altered in metabolic diseases, such as obesity and type 2 diabetes, and are thus proposed to be possible targets for the prevention or treatment of these diseases. It is clear that food composition, macronutrients, and other non-nutrient components as well as the physical properties of food not only modulate the secretion of gut peptides but also modulate transcription and enteroendocrine cell differentiation, which ultimately modifies gut hormone response. The specific mechanisms or sensing machinery that respond to the different components of the diet have been studied for many years; however, over the last few years, new molecular genetic techniques have led to important advances, thereby allowing a deeper understanding of these mechanisms. This review addresses the current knowledge regarding enteroendocrine cells and how diet interacts with this machinery to stimulate and regulate the secretion of gut peptides. The potential for diet interventions as a promising strategy for modulating gut hormone responses to food ingestion and, ultimately, preventing or treating metabolic diseases is being emphasized considering that these diseases are currently a public health burden.
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Affiliation(s)
- Sofia Moran-Ramos
- Departamento de Fisiología de la Nutrición Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán,” México, México City, México; and,Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México
| | - Armando R. Tovar
- Departamento de Fisiología de la Nutrición Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán,” México, México City, México; and
| | - Nimbe Torres
- Departamento de Fisiología de la Nutrición Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán,” México, México City, México; and,To whom correspondence should be addressed. E-mail:
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23
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Gustatory and extragustatory functions of mammalian taste receptors. Physiol Behav 2011; 105:4-13. [DOI: 10.1016/j.physbeh.2011.02.010] [Citation(s) in RCA: 172] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 02/01/2011] [Accepted: 02/07/2011] [Indexed: 01/05/2023]
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24
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Gerspach AC, Steinert RE, Schönenberger L, Graber-Maier A, Beglinger C. The role of the gut sweet taste receptor in regulating GLP-1, PYY, and CCK release in humans. Am J Physiol Endocrinol Metab 2011; 301:E317-25. [PMID: 21540445 DOI: 10.1152/ajpendo.00077.2011] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The recent identification of sweet taste receptors in the gastrointestinal tract has important implications in the control of food intake and glucose homeostasis. Lactisole can inhibit the sweet taste receptor T1R2/T1R3. The objective was to use lactisole as a probe to investigate the physiological role of T1R2/T1R3 by assessing the effect of T1R2/T1R3 blockade on GLP-1, PYY, and CCK release in response to 1) intragastric administration of nutrients or 2) intraduodenal perfusion of nutrients. The study was performed as a randomized, double-blind, placebo-controlled crossover study that included 35 healthy subjects. In part I, subjects received intragastrically 75 g of glucose in 300 ml of water or 500 ml of a mixed liquid meal with or without lactisole. In part II, subjects received an intraduodenal perfusion of glucose (29.3 g glucose/100 ml; rate: 2.5 ml/min for 180 min) or a mixed liquid meal (same rate) with or without lactisole. The results were that 1) lactisole induced a significant reduction in GLP-1 and PYY but not CCK secretion in both the intragastric and the intraduodenal glucose-stimulated parts (P ≤ 0.05), 2) comparison of the inhibitory effect of lactisole showed a significantly greater suppression of the hormone response in the intragastric part (P = 0.023), and 3) lactisole had no effect on liquid meal-stimulated parameters. We conclude that T1R2/T1R3 is involved in glucose-dependent secretion of satiation peptides. However, the results of the liquid meal-stimulated parts show that the receptor alone is not responsible for peptide secretion.
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Affiliation(s)
- A C Gerspach
- Phase 1 Research Unit, Department of Biomedicine, University Hospital Basel, Basel, Switzerland
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25
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Current world literature. Curr Opin Endocrinol Diabetes Obes 2011; 18:83-98. [PMID: 21178692 DOI: 10.1097/med.0b013e3283432fa7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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