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Cell Metabolism Apr 2017In addition to their bioenergetic intracellular function, several classical metabolites act as extracellular signaling molecules activating cell-surface... (Review)
Review
In addition to their bioenergetic intracellular function, several classical metabolites act as extracellular signaling molecules activating cell-surface G-protein-coupled receptors (GPCRs), similar to hormones and neurotransmitters. "Signaling metabolites" generated from nutrients or by gut microbiota target primarily enteroendocrine, neuronal, and immune cells in the lamina propria of the gut mucosa and the liver and, through these tissues, the rest of the body. In contrast, metabolites from the intermediary metabolism act mainly as metabolic stress-induced autocrine and paracrine signals in adipose tissue, the liver, and the endocrine pancreas. Importantly, distinct metabolite GPCRs act as efficient pro- and anti-inflammatory regulators of key immune cells, and signaling metabolites may thus function as important drivers of the low-grade inflammation associated with insulin resistance and obesity. The concept of key metabolites as ligands for specific GPCRs has broadened our understanding of metabolic signaling significantly and provides a number of novel potential drug targets.
Topics: Animals; Enteroendocrine Cells; Gastrointestinal Microbiome; Humans; Ligands; Metabolome; Receptors, G-Protein-Coupled; Signal Transduction
PubMed: 28380372
DOI: 10.1016/j.cmet.2017.03.008 -
Cell Reports May 2019Intestinal-type gastric cancer is preceded by premalignant lesions, including chronic atrophic gastritis and intestinal metaplasia. In this study, we constructed a...
Intestinal-type gastric cancer is preceded by premalignant lesions, including chronic atrophic gastritis and intestinal metaplasia. In this study, we constructed a single-cell atlas for 32,332 high-quality cells from gastric antral mucosa biopsies of patients spanning a cascade of gastric premalignant lesions and early gastric cancer (EGC) using single-cell RNA sequencing. We then constructed a single-cell network underlying cellular and molecular characteristics of gastric epithelial cells across different lesions. We found that gland mucous cells tended to acquire an intestinal-like stem cell phenotype during metaplasia, and we identified OR51E1 as a marker for unique endocrine cells in the early-malignant lesion. We also found that HES6 might mark the pre-goblet cell cluster, potentially aiding identification of metaplasia at the early stage. Finally, we identified a panel of EGC-specific signatures, with clinical implications for the precise diagnosis of EGC. Our study offers unparalleled insights into the human gastric cellulome in premalignant and early-malignant lesions.
Topics: Basic Helix-Loop-Helix Transcription Factors; Cell Lineage; Enteroendocrine Cells; Epithelial Cells; Gastric Mucosa; Gene Expression Regulation, Neoplastic; Gene Regulatory Networks; Goblet Cells; Humans; Precancerous Conditions; RNA, Neoplasm; Repressor Proteins; Single-Cell Analysis; Stomach Neoplasms; Transcription, Genetic; Transcriptome
PubMed: 31067475
DOI: 10.1016/j.celrep.2019.04.052 -
Brain Research Aug 2018Parkinson's disease (PD) is a debilitating neurodegenerative condition associated with tremor, rigidity, dementia, and gastrointestinal symptoms such as constipation,... (Review)
Review
Parkinson's disease (PD) is a debilitating neurodegenerative condition associated with tremor, rigidity, dementia, and gastrointestinal symptoms such as constipation, nausea and vomiting. The pathological hallmarks of PD are Lewy bodies and neurites in the brain and peripheral nerves. The major constituent of Lewy bodies is the neuronal protein α-synuclein. Misfolding of α-synuclein confers prion-like properties enabling its spread from cell to cell. Misfolded α-synuclein also serves as a template and induces misfolding of endogenous α-synuclein in recipient cells leading to the formation of oligomers that progress to fibrils and eventually Lewy bodies. Accumulating evidence suggests that PD may arise in the gut. Clinically, gastrointestinal symptoms often appear in patients before other neurological signs and aggregates of α-synuclein have been found in enteric nerves of PD patients. Importantly, patients undergoing vagotomy have a reduced risk of developing PD. Experimentally, abnormal forms of α-synuclein appear in enteric nerves before they appear in the brain and injection of abnormal α-synuclein into the wall of the intestine spreads to the vagus nerve. Ingested toxins and alterations in gut microbiota can induce α-synuclein aggregation and PD, however, it is not known how PD starts. Recently, it has been shown that sensory cells of the gut known as enteroendocrine cells (EECs) contain α-synuclein and synapse with enteric nerves, thus providing a connection from the gut to the brain. It is possible that abnormal α-synuclein first develops in EECs and spreads to the nervous system.
Topics: Animals; Enteroendocrine Cells; Gastrointestinal Tract; Humans; Lewy Bodies; Neurons; Parkinson Disease; Prions; Proteostasis Deficiencies; alpha-Synuclein
PubMed: 29360467
DOI: 10.1016/j.brainres.2018.01.010 -
Science (New York, N.Y.) Sep 2018The brain is thought to sense gut stimuli only via the passive release of hormones. This is because no connection has been described between the vagus and the putative...
The brain is thought to sense gut stimuli only via the passive release of hormones. This is because no connection has been described between the vagus and the putative gut epithelial sensor cell-the enteroendocrine cell. However, these electrically excitable cells contain several features of epithelial transducers. Using a mouse model, we found that enteroendocrine cells synapse with vagal neurons to transduce gut luminal signals in milliseconds by using glutamate as a neurotransmitter. These synaptically connected enteroendocrine cells are referred to henceforth as neuropod cells. The neuroepithelial circuit they form connects the intestinal lumen to the brainstem in one synapse, opening a physical conduit for the brain to sense gut stimuli with the temporal precision and topographical resolution of a synapse.
Topics: Animals; Brain Stem; Electrophysiological Phenomena; Enteroendocrine Cells; Green Fluorescent Proteins; Intestine, Small; Mice; Neurons; Signal Transduction; Synapses; Vagus Nerve; Vesicular Glutamate Transport Protein 1
PubMed: 30237325
DOI: 10.1126/science.aat5236 -
Gastroenterology Jun 2018Diarrhea is common in infants (children less than 2 years of age), usually acute, and, if chronic, commonly caused by allergies and occasionally by infectious agents.... (Review)
Review
Diarrhea is common in infants (children less than 2 years of age), usually acute, and, if chronic, commonly caused by allergies and occasionally by infectious agents. Congenital diarrheas and enteropathies (CODEs) are rare causes of devastating chronic diarrhea in infants. Evaluation of CODEs is a lengthy process and infrequently leads to a clear diagnosis. However, genomic analyses and the development of model systems have increased our understanding of CODE pathogenesis. With these advances, a new diagnostic approach is needed. We propose a revised approach to determine causes of diarrhea in infants, including CODEs, based on stool analysis, histologic features, responses to dietary modifications, and genetic tests. After exclusion of common causes of diarrhea in infants, the evaluation proceeds through analyses of stool characteristics (watery, fatty, or bloody) and histologic features, such as the villus to crypt ratio in intestinal biopsies. Infants with CODEs resulting from defects in digestion, absorption, transport of nutrients and electrolytes, or enteroendocrine cell development or function have normal villi to crypt ratios; defects in enterocyte structure or immune-mediated conditions result in an abnormal villus to crypt ratios and morphology. Whole-exome and genome sequencing in the early stages of evaluation can reduce the time required for a definitive diagnosis of CODEs, or lead to identification of new variants associated with these enteropathies. The functional effects of gene mutations can be analyzed in model systems such as enteroids or induced pluripotent stem cells and are facilitated by recent advances in gene editing procedures. Characterization and investigation of new CODE disorders will improve management of patients and advance our understanding of epithelial cells and other cells in the intestinal mucosa.
Topics: Biopsy; Chronic Disease; Critical Pathways; Diarrhea, Infantile; Endoscopy, Digestive System; Enterocytes; Enteroendocrine Cells; Genetic Testing; Humans; Infant; Infant, Newborn; Intestinal Diseases; Mutation; Whole Genome Sequencing
PubMed: 29654747
DOI: 10.1053/j.gastro.2018.03.067 -
Cell Feb 2019Homeostatic regulation of the intestinal enteroendocrine lineage hierarchy is a poorly understood process. We resolved transcriptional changes during enteroendocrine...
Homeostatic regulation of the intestinal enteroendocrine lineage hierarchy is a poorly understood process. We resolved transcriptional changes during enteroendocrine differentiation in real time at single-cell level using a novel knockin allele of Neurog3, the master regulator gene briefly expressed at the onset of enteroendocrine specification. A bi-fluorescent reporter, Neurog3Chrono, measures time from the onset of enteroendocrine differentiation and enables precise positioning of single-cell transcriptomes along an absolute time axis. This approach yielded a definitive description of the enteroendocrine hierarchy and its sub-lineages, uncovered differential kinetics between sub-lineages, and revealed time-dependent hormonal plasticity in enterochromaffin and L cells. The time-resolved map of transcriptional changes predicted multiple novel molecular regulators. Nine of these were validated by conditional knockout in mice or CRISPR modification in intestinal organoids. Six novel candidate regulators (Sox4, Rfx6, Tox3, Myt1, Runx1t1, and Zcchc12) yielded specific enteroendocrine phenotypes. Our time-resolved single-cell transcriptional map presents a rich resource to unravel enteroendocrine differentiation.
Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Differentiation; Cell Lineage; Enteroendocrine Cells; Fluorescent Dyes; Gene Expression Profiling; Homeodomain Proteins; Intestinal Mucosa; Mice; Mice, Knockout; Nerve Tissue Proteins; Optical Imaging; Organoids; Phenotype; Single-Cell Analysis; Stem Cells; Transcription Factors; Transcriptome
PubMed: 30712869
DOI: 10.1016/j.cell.2018.12.029 -
Proceedings of the National Academy of... Jan 2020Studies of the adult midgut have led to many insights in our understanding of cell-type diversity, stem cell regeneration, tissue homeostasis, and cell fate decision....
Studies of the adult midgut have led to many insights in our understanding of cell-type diversity, stem cell regeneration, tissue homeostasis, and cell fate decision. Advances in single-cell RNA sequencing provide opportunities to identify new cell types and molecular features. We used single-cell RNA sequencing to characterize the transcriptome of midgut epithelial cells and identified 22 distinct clusters representing intestinal stem cells, enteroblasts, enteroendocrine cells (EEs), and enterocytes. This unbiased approach recovered most of the known intestinal stem cells/enteroblast and EE markers, highlighting the high quality of the dataset, and led to insights on intestinal stem cell biology, cell type-specific organelle features, the roles of new transcription factors in progenitors and regional variation along the gut, 5 additional EE gut hormones, EE hormonal expression diversity, and paracrine function of EEs. To facilitate mining of this rich dataset, we provide a web-based resource for visualization of gene expression in single cells. Altogether, our study provides a comprehensive resource for addressing functions of genes in the midgut epithelium.
Topics: Animals; Digestive System; Drosophila; Drosophila Proteins; Enterocytes; Enteroendocrine Cells; Epithelial Cells; Epithelium; Gene Expression Regulation; Hormones; Intestines; Stem Cells; Transcription Factors; Transcriptome
PubMed: 31915294
DOI: 10.1073/pnas.1916820117 -
Cell Jun 2020Enteroendocrine cells (EECs) sense intestinal content and release hormones to regulate gastrointestinal activity, systemic metabolism, and food intake. Little is known...
Enteroendocrine cells (EECs) sense intestinal content and release hormones to regulate gastrointestinal activity, systemic metabolism, and food intake. Little is known about the molecular make-up of human EEC subtypes and the regulated secretion of individual hormones. Here, we describe an organoid-based platform for functional studies of human EECs. EEC formation is induced in vitro by transient expression of NEUROG3. A set of gut organoids was engineered in which the major hormones are fluorescently tagged. A single-cell mRNA atlas was generated for the different EEC subtypes, and their secreted products were recorded by mass-spectrometry. We note key differences to murine EECs, including hormones, sensory receptors, and transcription factors. Notably, several hormone-like molecules were identified. Inter-EEC communication is exemplified by secretin-induced GLP-1 secretion. Indeed, individual EEC subtypes carry receptors for various EEC hormones. This study provides a rich resource to study human EEC development and function.
Topics: Cells, Cultured; Enteroendocrine Cells; Gastrointestinal Hormones; Gastrointestinal Tract; Glucagon-Like Peptide 1; Humans; Organoids; RNA, Messenger; Transcription Factors; Transcriptome
PubMed: 32407674
DOI: 10.1016/j.cell.2020.04.036 -
Nature Reviews. Gastroenterology &... Jun 2020The gastrointestinal tract is the only internal organ to have evolved with its own independent nervous system, known as the enteric nervous system (ENS). This Review... (Review)
Review
The gastrointestinal tract is the only internal organ to have evolved with its own independent nervous system, known as the enteric nervous system (ENS). This Review provides an update on advances that have been made in our understanding of how neurons within the ENS coordinate sensory and motor functions. Understanding this function is critical for determining how deficits in neurogenic motor patterns arise. Knowledge of how distension or chemical stimulation of the bowel evokes sensory responses in the ENS and central nervous system have progressed, including critical elements that underlie the mechanotransduction of distension-evoked colonic peristalsis. Contrary to original thought, evidence suggests that mucosal serotonin is not required for peristalsis or colonic migrating motor complexes, although it can modulate their characteristics. Chemosensory stimuli applied to the lumen can release substances from enteroendocrine cells, which could subsequently modulate ENS activity. Advances have been made in optogenetic technologies, such that specific neurochemical classes of enteric neurons can be stimulated. A major focus of this Review will be the latest advances in our understanding of how intrinsic sensory neurons in the ENS detect and respond to sensory stimuli and how these mechanisms differ from extrinsic sensory nerve endings in the gut that underlie the gut-brain axis.
Topics: Afferent Pathways; Autonomic Fibers, Preganglionic; Efferent Pathways; Enteric Nervous System; Enteroendocrine Cells; Gastrointestinal Motility; Humans; Mechanotransduction, Cellular; Myoelectric Complex, Migrating; Neural Pathways; Neurons; Neurotransmitter Agents; Sensation; Sensory Receptor Cells; Serotonin
PubMed: 32152479
DOI: 10.1038/s41575-020-0271-2 -
Gastroenterology Feb 2022Acinar to ductal metaplasia (ADM) occurs in the pancreas in response to tissue injury and is a potential precursor for adenocarcinoma. The goal of these studies was to...
BACKGROUND & AIMS
Acinar to ductal metaplasia (ADM) occurs in the pancreas in response to tissue injury and is a potential precursor for adenocarcinoma. The goal of these studies was to define the populations arising from ADM, the associated transcriptional changes, and markers of disease progression.
METHODS
Acinar cells were lineage-traced with enhanced yellow fluorescent protein (EYFP) to follow their fate post-injury. Transcripts of more than 13,000 EYFP+ cells were determined using single-cell RNA sequencing (scRNA-seq). Developmental trajectories were generated. Data were compared with gastric metaplasia, Kras-induced neoplasia, and human pancreatitis. Results were confirmed by immunostaining and electron microscopy. Kras was expressed in injury-induced ADM using several inducible Cre drivers. Surgical specimens of chronic pancreatitis from 15 patients were evaluated by immunostaining.
RESULTS
scRNA-seq of ADM revealed emergence of a mucin/ductal population resembling gastric pyloric metaplasia. Lineage trajectories suggest that some pyloric metaplasia cells can generate tuft and enteroendocrine cells (EECs). Comparison with Kras-induced ADM identifies populations associated with disease progression. Activation of Kras expression in HNF1B+ or POU2F3+ ADM populations leads to neoplastic transformation and formation of MUC5AC+ gastric-pit-like cells. Human pancreatitis samples also harbor pyloric metaplasia with a similar transcriptional phenotype.
CONCLUSIONS
Under conditions of chronic injury, acinar cells undergo a pyloric-type metaplasia to mucinous progenitor-like populations, which seed disparate tuft cell and EEC lineages. ADM-derived EEC subtypes are diverse. Kras expression is sufficient to drive neoplasia when targeted to injury-induced ADM populations and offers an alternative origin for tumorigenesis. This program is conserved in human pancreatitis, providing insight into early events in pancreas diseases.
Topics: Acinar Cells; Carcinoma, Pancreatic Ductal; Cell Plasticity; Enteroendocrine Cells; Gene Expression Profiling; Humans; Metaplasia; Mucin 5AC; Pancreas; Pancreatic Ducts; Pancreatic Neoplasms; Pancreatitis; Proto-Oncogene Proteins p21(ras); Single-Cell Analysis
PubMed: 34695382
DOI: 10.1053/j.gastro.2021.10.027