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Zietek T, Giesbertz P, Ewers M, Reichart F, Weinmüller M, Urbauer E, Haller D, Demir IE, Ceyhan GO, Kessler H, Rath E. Organoids to Study Intestinal Nutrient Transport, Drug Uptake and Metabolism - Update to the Human Model and Expansion of Applications. Front Bioeng Biotechnol 2020; 8:577656. [PMID: 33015026 PMCID: PMC7516017 DOI: 10.3389/fbioe.2020.577656] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 08/19/2020] [Indexed: 12/22/2022] Open
Abstract
Intestinal transport and sensing processes and their interconnection to metabolism are relevant to pathologies such as malabsorption syndromes, inflammatory diseases, obesity and type 2 diabetes. Constituting a highly selective barrier, intestinal epithelial cells absorb, metabolize, and release nutrients into the circulation, hence serving as gatekeeper of nutrient availability and metabolic health for the whole organism. Next to nutrient transport and sensing functions, intestinal transporters including peptide transporter 1 (PEPT1) are involved in the absorption of drugs and prodrugs, including certain inhibitors of angiotensin-converting enzyme, protease inhibitors, antivirals, and peptidomimetics like β-lactam antibiotics. Here, we verify the applicability of 3D organoids for in vitro investigation of intestinal biochemical processes related to transport and metabolism of nutrients and drugs. Establishing a variety of methodologies including illustration of transporter-mediated nutrient and drug uptake and metabolomics approaches, we highlight intestinal organoids as robust and reliable tool in this field of research. Currently used in vitro models to study intestinal nutrient absorption, drug transport and enterocyte metabolism, such as Caco-2 cells or rodent explant models are of limited value due to their cancer and non-human origin, respectively. Particularly species differences result in poorly correlative data and findings obtained in these models cannot be extrapolated reliably to humans, as indicated by high failure rates in drug development pipelines. In contrast, human intestinal organoids represent a superior model of the intestinal epithelium and might help to implement the 3Rs (Reduction, Refinement and Replacement) principle in basic science as well as the preclinical and regulatory setup.
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Affiliation(s)
- Tamara Zietek
- Chair of Nutritional Physiology, Technische Universität München, Munich, Germany
| | - Pieter Giesbertz
- Chair of Nutritional Physiology, Technische Universität München, Munich, Germany
| | - Maren Ewers
- Pediatric Nutritional Medicine, Klinikum Rechts der Isar, Else Kröner-Fresenius-Zentrum für Ernährungsmedizin, Technische Universität München, Munich, Germany
| | - Florian Reichart
- Institute for Advanced Study, Department of Chemistry and Center for Integrated Protein Science (CIPSM), Technische Universität München, Garching, Germany
| | - Michael Weinmüller
- Institute for Advanced Study, Department of Chemistry and Center for Integrated Protein Science (CIPSM), Technische Universität München, Garching, Germany
| | - Elisabeth Urbauer
- Chair of Nutrition and Immunology, Technische Universität München, Munich, Germany
| | - Dirk Haller
- Chair of Nutrition and Immunology, Technische Universität München, Munich, Germany.,ZIEL Institute for Food and Health, Technische Universität München, Munich, Germany
| | - Ihsan Ekin Demir
- Department of Surgery, Klinikum Rechts der Isar, Technische Universität München, Munich, Germany.,Department of General Surgery, HPB-Unit, School of Medicine, Acibadem Mehmet Ali Aydinlar University, Istanbul, Turkey.,German Cancer Consortium (DKTK), Munich, Germany.,CRC 1321 Modeling and Targeting Pancreatic Cancer, Klinikum rechts der Isar, School of Medicine, Technische Universität München, Munich, Germany
| | - Güralp O Ceyhan
- Department of Surgery, Klinikum Rechts der Isar, Technische Universität München, Munich, Germany.,Department of General Surgery, HPB-Unit, School of Medicine, Acibadem Mehmet Ali Aydinlar University, Istanbul, Turkey
| | - Horst Kessler
- Institute for Advanced Study, Department of Chemistry and Center for Integrated Protein Science (CIPSM), Technische Universität München, Garching, Germany
| | - Eva Rath
- Chair of Nutrition and Immunology, Technische Universität München, Munich, Germany
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Rubio C, Puerto M, García-Rodríquez JJ, Lu VB, García-Martínez I, Alén R, Sanmartín-Salinas P, Toledo-Lobo MV, Saiz J, Ruperez J, Barbas C, Menchén L, Gribble FM, Reimann F, Guijarro LG, Carrascosa JM, Valverde ÁM. Impact of global PTP1B deficiency on the gut barrier permeability during NASH in mice. Mol Metab 2020; 35:100954. [PMID: 32244182 PMCID: PMC7082558 DOI: 10.1016/j.molmet.2020.01.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 01/23/2020] [Accepted: 01/28/2020] [Indexed: 12/11/2022] Open
Abstract
OBJECTIVE Non-alcoholic steatohepatitis (NASH) is characterized by a robust pro-inflammatory component at both hepatic and systemic levels together with a disease-specific gut microbiome signature. Protein tyrosine phosphatase 1 B (PTP1B) plays distinct roles in non-immune and immune cells, in the latter inhibiting pro-inflammatory signaling cascades. In this study, we have explored the role of PTP1B in the composition of gut microbiota and gut barrier dynamics in methionine and choline-deficient (MCD) diet-induced NASH in mice. METHODS Gut features and barrier permeability were characterized in wild-type (PTP1B WT) and PTP1B-deficient knockout (PTP1B KO) mice fed a chow or methionine/choline-deficient (MCD) diet for 4 weeks. The impact of inflammation was studied in intestinal epithelial and enteroendocrine cells. The secretion of GLP-1 was evaluated in primary colonic cultures and plasma of mice. RESULTS We found that a shift in the gut microbiota shape, disruption of gut barrier function, higher levels of serum bile acids, and decreased circulating glucagon-like peptide (GLP)-1 are features during NASH. Surprisingly, despite the pro-inflammatory phenotype of global PTP1B-deficient mice, they were partly protected against the alterations in gut microbiota composition during NASH and presented better gut barrier integrity and less permeability under this pathological condition. These effects concurred with higher colonic mucosal inflammation, decreased serum bile acids, and protection against the decrease in circulating GLP-1 levels during NASH compared with their WT counterparts together with increased expression of GLP-2-sensitive genes in the gut. At the molecular level, stimulation of enteroendocrine STC-1 cells with a pro-inflammatory conditioned medium (CM) from lipopolysaccharide (LPS)-stimulated macrophages triggered pro-inflammatory signaling cascades that were further exacerbated by a PTP1B inhibitor. Likewise, the pro-inflammatory CM induced GLP-1 secretion in primary colonic cultures, an effect augmented by PTP1B inhibition. CONCLUSION Altogether our results have unraveled a potential role of PTP1B in the gut-liver axis during NASH, likely mediated by increased sensitivity to GLPs, with potential therapeutic value.
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Affiliation(s)
- Carmen Rubio
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM), Madrid, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), ISCIII, Madrid, Spain; Centro de Biología Molecular Severo Ochoa (CBMSO, CSIC-UAM), Madrid, Spain
| | - Marta Puerto
- Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; CIBER de Enfermedades Hepáticas y Digestivas (CIBERHED), ISCIII, Madrid, Spain
| | - Juan J García-Rodríquez
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Van B Lu
- Wellcome Trust MRC Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
| | - Irma García-Martínez
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM), Madrid, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), ISCIII, Madrid, Spain
| | - Rosa Alén
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM), Madrid, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), ISCIII, Madrid, Spain
| | | | - M Val Toledo-Lobo
- Departamento de Biología de Sistemas, Universidad de Alcalá de Henares, Madrid, Spain
| | - Jorge Saiz
- CEMBIO, Universidad San Pablo-CEU, Madrid, Spain
| | | | - Coral Barbas
- CEMBIO, Universidad San Pablo-CEU, Madrid, Spain
| | - Luis Menchén
- Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; CIBER de Enfermedades Hepáticas y Digestivas (CIBERHED), ISCIII, Madrid, Spain; Departamento de Medicina, Facultad de Medicina, Universidad Complutense de Madrid, Spain
| | - Fiona M Gribble
- Wellcome Trust MRC Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
| | - Frank Reimann
- Wellcome Trust MRC Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
| | - Luis G Guijarro
- Departamento de Biología de Sistemas, Universidad de Alcalá de Henares, Madrid, Spain
| | - Jose M Carrascosa
- Centro de Biología Molecular Severo Ochoa (CBMSO, CSIC-UAM), Madrid, Spain.
| | - Ángela M Valverde
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM), Madrid, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), ISCIII, Madrid, Spain.
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Starck CS, Wolfe RR, Moughan PJ. Endogenous Amino Acid Losses from the Gastrointestinal Tract of the Adult Human-A Quantitative Model. J Nutr 2018; 148:1871-1881. [PMID: 30247627 DOI: 10.1093/jn/nxy162] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 06/28/2018] [Indexed: 11/12/2022] Open
Abstract
Background The loss of endogenous (nondietary) amino acids (AAs) from the gastrointestinal tract (GIT) is an important component underlying the adult human dietary requirement for protein and essential AAs (EAAs). Although data with regard to endogenous AA losses to the end of the small intestine have been published, to our knowledge there are no direct measures of colonic endogenous AA losses. Objective The objective was to derive quantitative estimates for daily endogenous protein and EAAs lost from the colon of the adult human. Methods A factorial model was developed for the prediction of endogenous AA losses across the adult human GIT. Estimates of AAs entering the upper GIT lumen were combined with relative protein synthesis rates in the colon to predict colonic AA losses. The AA composition of human colonic endogenous protein was calculated by estimating the relative contributions of epithelial cell protein and mucin protein on the basis of published data for cell shedding in the pig small intestine, small intestinal protein synthesis rates in pigs and humans, and human upper and lower GIT surface areas. Colonic AA losses were summed with empirical estimates of ileal AA losses in humans to estimate total daily GIT endogenous AA losses. Results Colonic AA loss was estimated to total 3.5 g/d in the adult male human, comprising 33% of total GIT endogenous AA loss (10.2 g/d). GIT essential AA losses accounted for 25-97% of the current recommended daily AA requirement for adult humans. For threonine, colonic losses were 54% of total GIT threonine losses, which were 97% of the current recommended daily threonine requirement. Conclusions Colonic endogenous AA losses represent a significant fraction of total GIT endogenous AA losses. The requirement of the GIT for EAAs to replace AAs lost via the gut lumen comprises a substantial proportion of the Recommended Daily Intake of AAs.
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Affiliation(s)
- Carlene S Starck
- Riddet Institute, Massey University, Palmerston North, New Zealand
| | - Robert R Wolfe
- Reynolds Institute on Aging and Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR
| | - Paul J Moughan
- Riddet Institute, Massey University, Palmerston North, New Zealand
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James HA, O'Neill BT, Nair KS. Insulin Regulation of Proteostasis and Clinical Implications. Cell Metab 2017; 26:310-323. [PMID: 28712655 PMCID: PMC8020859 DOI: 10.1016/j.cmet.2017.06.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 05/02/2017] [Accepted: 06/14/2017] [Indexed: 02/01/2023]
Abstract
Maintenance and modification of the cellular proteome are at the core of normal cellular physiology. Although insulin is well known for its control of glucose homeostasis, its critical role in maintaining proteome homeostasis (proteostasis) is less appreciated. Insulin signaling regulates protein synthesis and degradation as well as posttranslational modifications at the tissue level and coordinates proteostasis at the organism level. Here, we review regulation of proteostasis by insulin in postabsorptive, postprandial, and diabetic states. We present the effects of insulin on amino acid flux in skeletal muscle and splanchnic tissues, the regulation of protein quality control, and turnover of mitochondrial protein pools in humans. We also review the current evidence for the mechanistic control of proteostasis by insulin and insulin-like growth factor 1 receptors based on preclinical studies. Finally, we discuss irreversible posttranslational modifications of the proteome in diabetes and how future investigations will provide new insights into mechanisms of diabetic complications.
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Affiliation(s)
- Haleigh A James
- Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
| | - Brian T O'Neill
- Division of Endocrinology and Metabolism, Fraternal Order of Eagles Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - K Sreekumaran Nair
- Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
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Zhao M, Liao D, Zhao J. Diabetes-induced mechanophysiological changes in the small intestine and colon. World J Diabetes 2017; 8:249-269. [PMID: 28694926 PMCID: PMC5483424 DOI: 10.4239/wjd.v8.i6.249] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 04/05/2017] [Accepted: 05/05/2017] [Indexed: 02/05/2023] Open
Abstract
The disorders of gastrointestinal (GI) tract including intestine and colon are common in the patients with diabetes mellitus (DM). DM induced intestinal and colonic structural and biomechanical remodeling in animals and humans. The remodeling is closely related to motor-sensory abnormalities of the intestine and colon which are associated with the symptoms frequently encountered in patients with DM such as diarrhea and constipation. In this review, firstly we review DM-induced histomorphological and biomechanical remodeling of intestine and colon. Secondly we review motor-sensory dysfunction and how they relate to intestinal and colonic abnormalities. Finally the clinical consequences of DM-induced changes in the intestine and colon including diarrhea, constipation, gut microbiota change and colon cancer are discussed. The final goal is to increase the understanding of DM-induced changes in the gut and the subsequent clinical consequences in order to provide the clinicians with a better understanding of the GI disorders in diabetic patients and facilitates treatments tailored to these patients.
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Rittler P, Schiefer B, Demmelmair H, Koletzko B, Vogeser M, Alpers DH, Jauch KW, Hartl WH. The Effect of Hyperglycemic Hyperinsulinemia on Small-Intestinal Mucosal Protein Synthesis in Patients After Surgical Stress. JPEN J Parenter Enteral Nutr 2017; 30:97-107. [PMID: 16517954 DOI: 10.1177/014860710603000297] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hyperglycemic hyperinsulinemia cannot stimulate intestinal protein synthesis in healthy individuals but does so in conditions characterized by an altered somatotropic axis such as diabetes. Only in a state of growth hormone resistance (high growth hormone but low insulin like growth factor [IGF-1] concentrations), extra insulin may acutely reverse the impaired, growth-hormone-induced IGF-1 release, thereby exerting anabolic actions at the intestinal tract. Growth hormone resistance can be also found in patients after surgical stress. Therefore, we wanted to test the hypothesis whether hyperglycemic hyperinsulinemia would stimulate ileal protein synthesis in the latter condition. Mass spectrometry techniques (capillary gas chromatography/combustion isotope ratio mass spectrometry) were used to directly determine the incorporation rate of 1-[(13)C]-leucine into ileal mucosal protein. All subjects had an ileostomy, which allowed easy access to the ileal mucosa, and consecutive sampling from the same tissue was performed during continuous isotope infusion (0.16 mumol/kg min). Isotopic enrichments and fractional protein synthesis were determined at baseline (period I) and after a 4-hour glucose infusion (170 mg/kg/h) or after infusion of saline (control group) (period II). In controls, ileal protein synthesis declined significantly during prolonged isotope infusion (period I: 1.11 +/- 0.14%/h, period II: 0.39 +/- 0.13%/h, p < .01). In contrast, ileal protein synthesis remained constant during glucose infusion (period I: 1.32 +/- 0.35%/h, period II: 1.33 +/- 0.21%/h, n.s. vs period I, but p < .005 vs the corresponding value at the end of period II in the control group). Using the continuous tracer infusion technique, ileal protein synthesis seemingly declines over a short time in control subjects. We found evidence that this artificial decline was due to mass effects of a rapidly turning over mucosa protein pool in which an isotopic plateau was reached during the experiment and of which the size amounted to approximately 4% of the total mixed protein pool. Maintenance of ileal protein synthesis during glucose infusion therefore indicates a rise of ileal protein synthesis in a slowly turning over protein pool. This effect in postsurgical patients would be compatible with the concept of intestinal insulin action to depend on the specific clinical state (eg, growth hormone resistance).
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Affiliation(s)
- Peter Rittler
- Department of Surgery, Department of Clinical Chemistry, Klinikum Grosshadern, Marchioninistrasse 15, D-81377 Munich, Germany
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Ravages of Diabetes on Gastrointestinal Sensory-Motor Function: Implications for Pathophysiology and Treatment. Curr Gastroenterol Rep 2016; 18:6. [PMID: 26768896 DOI: 10.1007/s11894-015-0481-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Symptoms related to functional and sensory abnormalities are frequently encountered in patients with diabetes mellitus. Most symptoms are associated with impaired gastric and intestinal function. In this review, we discuss basic concepts of sensory-motor dysfunction and how they relate to clinical findings and gastrointestinal abnormalities that are commonly seen in diabetes. In addition, we review techniques that are available for investigating the autonomic nervous system, neuroimaging and neurophysiology of sensory-motor function. Such technological advances, while not readily available in the clinical setting, may facilitate stratification and individualization of therapy in diabetic patients in the future. Unraveling the structural, mechanical, and sensory remodeling in diabetes disease is based on a multidisciplinary approach that can bridge the knowledge from a variety of scientific disciplines. The final goal is to increase the understanding of the damage to GI structures and to sensory processing of symptoms, in order to assist clinicians with developing an optimal mechanics based treatment.
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Altered CD161 bright CD8+ mucosal associated invariant T (MAIT)-like cell dynamics and increased differentiation states among juvenile type 1 diabetics. PLoS One 2015; 10:e0117335. [PMID: 25625430 PMCID: PMC4307988 DOI: 10.1371/journal.pone.0117335] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 12/22/2014] [Indexed: 12/16/2022] Open
Abstract
Type 1A diabetes (T1D) is believed to be caused by immune-mediated destruction of β-cells, but the immunological basis for T1D remains controversial. Microbial diversity promotes the maturation and activation of certain immune subsets, including CD161bright CD8+ mucosal associated invariant T (MAIT) cells, and alterations in gut mucosal responses have been reported in type 1 diabetics (T1Ds). We analyzed T cell populations in peripheral blood leukocytes from juvenile T1Ds and healthy controls. We found that proportion and absolute number of MAIT cells were similar between T1Ds and controls. Furthermore, while MAIT cell proportions increased with age among healthy controls, this trend was not observed among long-standing T1Ds. Additionally, the CD27- MAIT cell subset is significantly increased in T1Ds and positively correlated with HbA1c levels. However, after T1Ds are stratified by age, the younger group has significantly increased proportions of CD27- MAIT cells compared to age-matched controls, and this proportional increase appears to be independent of HbA1c levels. Finally, we analyzed function of the CD27- MAIT cells and observed that IL-17A production is increased in CD27- compared to CD27+ MAIT cells. Overall, our data reveal disparate MAIT cell dynamics between T1Ds and controls, as well as signs of increased MAIT cell activation in T1Ds. These changes may be linked to hyperglycemia and increased mucosal challenge among T1Ds.
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Chinese herbal medicine banxiaxiexin decoction treating diabetic gastroparesis: a systematic review of randomized controlled trials. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:749495. [PMID: 23935681 PMCID: PMC3725710 DOI: 10.1155/2013/749495] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 05/19/2013] [Accepted: 05/20/2013] [Indexed: 12/27/2022]
Abstract
Objective. To assess the current clinical evidence of Banxiaxiexin decoction for diabetic gastroparesis (DGP). Methods. Electronic databases were searched until December 2012. No language limitations were applied. We included RCTs using Banxiaxiexin decoction/modified Banxiaxiexin decoction for DGP. No restriction for the control group except acupuncture. Applying clinical effective rate as the main outcome index. Data extraction, analyses and quality assessment were conducted according to the Cochrane review standards. Results. 16 RCTs involving 1302 patients were finally identified, and the methodological quality was evaluated as generally low. The data showed that the effect of Banxiaxiexin decoction (BXXD) for DGP was superior to the control group (n = 1302, RR 1.23, 95% CI 1.17 to 1.29, Z = 8.04, P < 0.00001). Only one trial recorded adverse events, no obvious adverse event occurred. Conclusions. Banxiaxiexin decoction could regain the gastric emptying rate and improve diabetic gastrointestinal symptoms. However, the methodological quality of included studies is low, and long term efficacy and safety are still uncertain, which indicates that the findings above should be read with caution. Thereby, well-designed, large-scale, and high-quality randomized controlled clinical trials with scientific rigor are warranted for stronger evidence in future research.
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Coëffier M, Claeyssens S, Bôle-Feysot C, Guérin C, Maurer B, Lecleire S, Lavoinne A, Donnadieu N, Cailleux AF, Déchelotte P. Enteral delivery of proteins stimulates protein synthesis in human duodenal mucosa in the fed state through a mammalian target of rapamycin-independent pathway. Am J Clin Nutr 2013; 97:286-94. [PMID: 23283505 DOI: 10.3945/ajcn.112.046946] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Glutamine modulates duodenal protein metabolism in fasted healthy humans, but its effects in a fed state remain unknown. OBJECTIVE We aimed to assess the effects of either glutamine or an isonitrogenous protein mixture on duodenal protein metabolism in humans in the fed state. DESIGN Twenty-four healthy volunteers were randomly included in 2 groups. Each volunteer was studied on 2 occasions in a random order and received, during 5 h, either an enteral infusion of maltodextrins alone (0.25 g · kg⁻¹ · h⁻¹; both groups) that mimicked a carbohydrate fed state or maltodextrins with glutamine (group 1) or an isonitrogenous (22.4 mg N · kg⁻¹ · h⁻¹) protein powder (group 2). Simultaneously, a continuous intravenous infusion of ¹³C-leucine and ²H₅-phenylalanine (both 9 μmol · kg⁻¹ · h⁻¹) was performed. Endoscopic duodenal biopsies were taken. Leucine and phenylalanine enrichments were assessed by using gas chromatography-mass spectrometry in duodenal proteins and the intracellular free amino acids pool to calculate the mucosal fractional synthesis rate (FSR). Proteasome proteolytic activities and phosphokinase expression were assessed by using specific fluorogenic substrates and macroarrays, respectively. RESULTS The FSR and proteasome activity were not different after the glutamine supply compared with after maltodextrins alone. In contrast, the FSR increased (1.7-fold increase; P < 0.05) after protein-powder delivery without modification of total proteasome activity. The protein powder increased insulinemia, PI3 kinase, and erk phosphorylation but did not affect the mammalian target of rapamycin (mTOR) pathway and mitogen-activated protein kinase signal-integrating kinase 1 phosphorylation. A trend for an increase of eukaryotic translation initiation factor 4E phosphorylation was observed (P = 0.07). CONCLUSION In the carbohydrate fed state, enteral proteins but not glutamine increased duodenal protein synthesis through an mTOR independent pathway in humans.
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Affiliation(s)
- Moïse Coëffier
- Institut National de la Santé et de la Recherche Médicale (INSERM) Unit 1073, Rouen University Hospital, Rouen, France
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Tennoune N, Bertrand J, Goichon A, Déchelotte P, Coëffier M. Régulation du métabolisme protéique intestinal par les nutriments. NUTR CLIN METAB 2011. [DOI: 10.1016/j.nupar.2011.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Goichon A, Coëffier M, Claeyssens S, Lecleire S, Cailleux AF, Bôle-Feysot C, Chan P, Donnadieu N, Lerebours E, Lavoinne A, Boyer O, Vaudry D, Déchelotte P. Effects of an enteral glucose supply on protein synthesis, proteolytic pathways, and proteome in human duodenal mucosa. Am J Clin Nutr 2011; 94:784-94. [PMID: 21795435 DOI: 10.3945/ajcn.110.009738] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Previous studies have shown that the glucose supply reduces postoperative insulin resistance and improves patient outcomes. However, the effects of luminal glucose on intestinal mucosal proteins remain unknown. OBJECTIVE We aimed to assess the effects of an enteral glucose supply on protein synthesis, proteolytic pathways, and proteome in human duodenal mucosa. DESIGN Twenty healthy volunteers received a 5-h enteral infusion of either saline or glucose (0.12 g · kg(-1) · h(-1)). Simultaneously, a continuous intravenous infusion of l-[1-(13)C]leucine (12 μmol · kg(-1) · h(-1)) was maintained until endoscopy. The duodenal mucosal protein fractional synthesis rate (FSR) was calculated from leucine enrichments assessed in protein and free amino acid pools by gas chromatography-mass spectrometry. Cathepsin D, calpains, and chymotrypsin-like proteasome mucosal activities were evaluated by using specific fluorogenic substrates. A 2-dimensional PAGE-based comparative proteomics analysis was also performed on additional duodenal mucosal biopsy samples to identify differentially expressed proteins. RESULTS Duodenal mucosal protein FSR and protease activities were not affected by glucose infusion relative to saline. Nevertheless, the comparative proteomics analysis indicated that 10 protein spots were significantly differentially expressed (ie, at least ±1.5-fold modulated; Student's t test, P < 0.05) in response to the glucose infusion relative to saline. Of the 8 proteins identified by mass spectrometry, α-enolase, cytoplasmic aconitate hydratase, and glutathione S-transferase ω-1 were upregulated, whereas epoxide hydrolase 2 was downregulated. CONCLUSION Enteral glucose supply affected neither duodenal mucosal protein FSR nor activities of mucosal proteases but altered the duodenal mucosal proteome by modulating the expression of several enzymes involved mainly in carbohydrate and xenobiotic metabolism. This trial is registered at clinicaltrials.gov as NCT00213551.
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Affiliation(s)
- Alexis Goichon
- ADEN EA, Institute for Biomedical Research, Rouen University Hospital, France
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Oral insulin supplementation in paediatric short bowel disease: a pilot observational study. J Pediatr Gastroenterol Nutr 2009; 49:108-11. [PMID: 19503001 DOI: 10.1097/mpg.0b013e31819344db] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND AND AIM Insulin is present in human milk, and oral insulin supplementation causes a dramatic adaptive gut growth in a rat model of short bowel syndrome (SBS). We conducted an open-label pilot observational study to examine whether oral insulin supplementation to paediatric patients with SBS decreases the need for parenteral nutrition (PN). METHODS Between April 2004 and March 2006, 10 premature infants and children were recruited from 8 paediatric gastroenterology centres in Israel, Croatia, and Germany. Enrolled subjects received 1 unit of insulin (Actrapid, Novonordisk, Denmark)/kg body weight per dose x 4/day (every 6 hours) for 28 days. We monitored glucose blood levels, weight, enteral and parenteral intake of calories, carbohydrates, and lipids. In addition, blood levels of albumin, ALT, AST, GGT, ALP, total cholesterol, triglycerides, and anti-insulin antibodies were recorded. RESULTS On average, enteral intake increased from 45.6% +/- 30.6% to 58.9% +/- 28.2% (not statistically significant), and ALT blood levels decreased from 194 +/- 128 U to 136 +/- 79 U (not statistically significant). Two (2/10) infants were weaned off PN. None of the children developed insulin antibodies. CONCLUSIONS Oral insulin supplementation in paediatric SBS is not associated with short-term side effects. Although clinical improvement was observed in a subset of children, whether these effects are due to insulin administration is uncertain. The efficacy of oral insulin remains to be determined in a double-blind manner using a preparation that is resistant to degradation in the stomach.
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Suryawan A, O'Connor PMJ, Bush JA, Nguyen HV, Davis TA. Differential regulation of protein synthesis by amino acids and insulin in peripheral and visceral tissues of neonatal pigs. Amino Acids 2008; 37:97-104. [PMID: 18683020 DOI: 10.1007/s00726-008-0149-z] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2008] [Accepted: 07/10/2008] [Indexed: 11/27/2022]
Abstract
The high efficiency of protein deposition during the neonatal period is driven by high rates of protein synthesis, which are maximally stimulated after feeding. In the current study, we examined the individual roles of amino acids and insulin in the regulation of protein synthesis in peripheral and visceral tissues of the neonate by performing pancreatic glucose-amino acid clamps in overnight-fasted 7-day-old pigs. We infused pigs (n = 8-12/group) with insulin at 0, 10, 22, and 110 ng kg(-0.66) min(-1) to achieve approximately 0, 2, 6 and 30 muU ml(-1) insulin so as to simulate below fasting, fasting, intermediate, and fed insulin levels, respectively. At each insulin dose, amino acids were maintained at the fasting or fed level. In conjunction with the highest insulin dose, amino acids were also allowed to fall below the fasting level. Tissue protein synthesis was measured using a flooding dose of L: -[4-(3)H] phenylalanine. Both insulin and amino acids increased fractional rates of protein synthesis in longissimus dorsi, gastrocnemius, masseter, and diaphragm muscles. Insulin, but not amino acids, increased protein synthesis in the skin. Amino acids, but not insulin, increased protein synthesis in the liver, pancreas, spleen, and lung and tended to increase protein synthesis in the jejunum and kidney. Neither insulin nor amino acids altered protein synthesis in the stomach. The results suggest that the stimulation of protein synthesis by feeding in most tissues of the neonate is regulated by the post-prandial rise in amino acids. However, the feeding-induced stimulation of protein synthesis in skeletal muscles is independently mediated by insulin as well as amino acids.
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Affiliation(s)
- Agus Suryawan
- United States Department Agriculture/Agriculture Research Service, Department of Pediatrics, Children's Nutrition Research Center, Baylor College of Medicine, 1100 Bates St, Houston, TX 77030, USA
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Winter TA, O'Keefe SJ, Callanan M, Marks T. Effect of severe undernutrition and subsequent refeeding on gut mucosal protein fractional synthesis in human subjects. Nutrition 2007; 23:29-35. [PMID: 17189088 DOI: 10.1016/j.nut.2006.10.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Revised: 10/12/2006] [Accepted: 10/16/2006] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Undernutrition has been associated with gut mucosal atrophy, impaired absorption, and increased permeability. This study investigated the effect of severe undernutrition and subsequent refeeding on gastric and duodenal mucosal protein fractional syntheses (MPFS). METHODS MPFS was investigated in the gastric body, antrum, and duodenum of 23 severely undernourished patients by means of (14)C-leucine incorporation into tissue protein and repeated after a period of refeeding. Results were evaluated in comparison with a group of 22 healthy controls and presented as mean +/- standard error of the mean. RESULTS The mean body index of the undernourished patients was 13.29 +/- 0.33 kg/m(2) versus 22.67 +/- 0.63 kg/m(2) in the controls (P < 0.001). MPFS in the controls and undernourished patients were similar (gastric body, 36.49 +/- 2.88 versus 33.41 +/- 3.08%/d; gastric antrum, 25.51 +/- 2.20 versus 24.95 +/- 2.32%/d; duodenum, 25.90 +/- 2.58 versus 25.49 +/- 1.99%/d). After refeeding, the body mass index of the undernourished patients increased to 15.87 +/- 0.44 kg/m(2) (P < 0.001). The MPFS increased significantly (gastric body, 51.80 +/- 8.12%/d, P < 0.05; gastric antrum, 33.44 +/- 3.66%/d, P < 0.05; duodenum, 46.27 +/- 8.02%/d, P < 0.01), with the MPFS of the duodenum significantly greater than the control values (P = 0.01). CONCLUSION Despite severe undernutrition, MPFS of the gastric body, antrum, and duodenum remained similar to control values. Enteral feeding resulted in a significant increase in MPFS, indicating a trophic response.
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Affiliation(s)
- Trevor A Winter
- Division of Digestive Disease and Nutrition, University of Kentucky, Lexington, Kentucky, USA.
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Physiology, regulation and multifunctional activity of the gut wall: a rationale for multicompartmental modelling. Nutr Res Rev 2006; 19:227-53. [DOI: 10.1017/s0954422407334094] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A rationale is given for a modelling approach to identify the mechanisms involved in the functioning and metabolic activity of tissues in the wall of the gastrointestinal tract. Maintenance and productive functions are discussed and related to the distinct compartments of the gastrointestinal tract and the metabolic costs involved. Functions identified are: tissue turnover; tissue proliferation; ion transport; nutrient transport; secretions of digestive enzymes, mucus and immunoglobulins; production of immune cells. The major nutrients involved include glucose, amino acids and volatile fatty acids.In vivomeasurements of net portal fluxes of these nutrients in pigs and ruminants are evaluated to illustrate the complexity of physiology and metabolic activity of the gastrointestinal tract. Experimental evidence indicates that high, but variable and specific, nutrient costs are involved in the functioning of the gastrointestinal tract.
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Sha H, Zhao JB, Zhang ZY, Zhou SP, Tong XL, Zhuang FY, Gregersen H. Effect of Kaiyu Qingwei Jianji on the morphometry and residual strain distribution of small intestine in experimental diabetic rats. World J Gastroenterol 2006; 12:7149-54. [PMID: 17131477 PMCID: PMC4087776 DOI: 10.3748/wjg.v12.i44.7149] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effect of a Chinese medicine, Kaiyu Qingwei Jianji (KYQWJJ) used for diabetic treatment, on the morphometry and residual strain distribution of the small intestine in streptozotocin (STZ) -induced diabetic rats. Correlation analysis was also performed between the opening angle and residual strain with the blood glucose level.
METHODS: Forty-two male Wistar rats weighing 220-240 g were included in this study. Thirty-two STZ-induced diabetic rats were subdivided into four groups (n = 8 in each group), i.e. diabetic control group (DM); high dose of KYQWJJ (T1, 36g/kg per day); low dose of KYQWJJ (T2, 17 g/kg per day) and Gliclazide (T3, 50 mg/kg per day). Another ten rats were used as non-diabetic control (CON). The medicines were poured directly into stomach lumen by gastric lavage twice daily. The rats of CON and DM groups were only poured the physiological saline. Blood glucose and plasma insulin levels were measured. Experimental period was 35 d. At the end of experiment, three 5-cm long segments were harvested from the duodenum, jejunum and ileum. Three rings of 1-2 mm in length for no-load and zero-stress state tests were cut from the middle of different segments. The morphometric data, such as the circumferential length, the wall thickness and the opening angle were measured from the digitized images of intestinal segments in the no-load state and zero-stress state. The residual strain was computed from the morphometry data. Furthermore, the linear regression analysis was performed between blood glucose level with morphometric and biomechanical data in the different intestinal segments.
RESULTS: The blood glucose level of DM group was consistent 4-fold to 5-fold higher than those in CON group during the experiment (16.89 ± 1.11 vs 3.44 ± 0.15 mmol/L, P < 0.001). The blood glucose level in the T1 (16.89 ± 1.11 vs 11.08 ± 2.67 mmol/L, P < 0.01) and T3 groups (16.89 ± 1.11 vs 13.54 ± 1.73 mmol/L, P < 0.05), but not in T2 group (P > 0.05) was significantly lower than those in DM group. The plasma insulin levels of DM, T1, T2 and T3 groups were significantly lower than those in CON group (10.98 ± 1.02, 12.52 ± 1.42,13.54 ± 1.56,10.96 ± 0.96 vs 17.84 ± 2.34 pmol/L respectively, P < 0.05), but no significantly difference among the groups with exception of CON group. The wet weight/cm and total wall thickness of duodenum, jejunum and ileum in DM group were significantly higher than those in CON group (wet weight (g/cm): duodenum 0.209 ± 0.012 vs 0.166 ± 0.010, jejunum 0.149 ± 0.008 vs 0.121 ± 0.004, ileum 0.134 ± 0.013 vs 0.112 ± 0.007; Wall thickness (mm): duodenum 0.849 ± 0.027 vs 0.710 ± 0.026, jejunum 0.7259 ± 0.034 vs 0.627 ± 0.025, ileum 0.532 ± 0.023 vs 0.470 ± 0.010, all P < 0.05), T1 and T3 treatment could partly restore change of wall thickness, but T2 could not. The opening angle and absolute value of inner and outer residual stain were significantly smaller in duodenal segment (188 ± 11 degrees, -0.31 ± 0.02 and 0.35 ± 0.03 vs 259 ± 15 degrees, -0.40 ± 0.02 and 0.43 ± 0.05) and larger in jejunal (215 ± 20 degrees, -0.30 ± 0.03 and 0.36 ± 0.06 vs 172 ± 19 degrees, -0.25 ± 0.02 and 0.27 ± 0.02) and ileal segments (183 ± 20 degrees, -0.28 ± 0.01 and 0.34 ± 0.05 vs 153 ± 14 degrees, -0.23 ± 0.03 and 0.29 ± 0.04) in DM group than in CON group (P < 0.01). T1 and T3 treatment could partly restore this biomechanical alteration, but strong effect was found in T1 treatment (duodenum 243 ± 14 degrees, -0.36 ± 0.02 and 0.42 ± 0.06, jejunum 180 ± 15 degrees, -0.26 ± 0.03 and 0.30 ± 0.06 and ileum 163 ± 17 degrees, -0.23 ± 0.03 and 0.30 ± 0.05, compared with DM, P < 0.05). The linear association was found between the glucose level with most morphometric and biomechanical data.
CONCLUSION: KYQWJJ (high dose) treatment could partly restore the changes of blood glucose level and the remodeling of morphometry and residual strain of small intestine in diabetic rats. The linear regression analysis demonstrated that the effect of KYQWJJ on intestinal opening angle and residual strain is partially through its effect on the blood glucose level.
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Affiliation(s)
- Hong Sha
- China-Japan Friendship Hospital, Beijing, China
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Abstract
PURPOSE OF REVIEW An intimate interrelationship exists between nutritional status and gut function. This review focuses on the consequences of a poor nutritional state on metabolism and digestive function, and evaluates the effects of refeeding. RECENT FINDINGS Severe undernutrition has been associated with increased fat and protein catabolism, reflected by a decreased respiratory quotient. Resting energy expenditure assessed in relationship to body weight was increased, probably as a consequence of changes in body composition. Protein synthesis, expressed per kg body weight, was decreased in undernourished patients with coexistent disease, but not in anorexia nervosa patients, indicating the detrimental effects of disease states. Severe undernutrition is associated with malabsorption, which improves following refeeding. Despite a high prevalence of villous atrophy in the duodenal mucosa in undernourished patients, mucosal protein fractional synthesis rates appeared normal. Refeeding resulted in a potent trophic response, and normalization of the mucosal morphology. Gastric and pancreatic secretion was significantly impaired by the undernourished state, with significant improvement following refeeding. SUMMARY Undernutrition is associated with impairment of digestive function, which is likely to further aggravate the nutritional state. Refeeding corrects this dysfunction, and results in disruption of this vicious circle.
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Affiliation(s)
- Trevor A Winter
- Division of Digestive Diseases and Nutrition, University of Kentucky, Lexington, Kentucky 40536-0298, USA.
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Shehadeh N, Sukhotnik I, Shamir R. Gastrointestinal tract as a target organ for orally administered insulin. J Pediatr Gastroenterol Nutr 2006; 43:276-81. [PMID: 16954946 DOI: 10.1097/01.mpg.0000226377.03247.fb] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The intestine is not considered to be a classic target tissue for insulin. Recent in vitro and in vivo experiments suggest that intestinal as well as systemic effects are observed following oral administration of insulin. Local effects include enhancement of intestinal growth, cell maturation, enzyme expression, gut adaptation after intestinal resection and reduction of intestinal permeability. Systemic effects, at least in animal models, include favorable effects on blood glucose and lipid profile and on the prevention of autoimmunity and attenuating the atherosclerotic process.
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Affiliation(s)
- Naim Shehadeh
- Department of Pediatrics A, Meyer Children's Hospital of Haifa, Haifa, Israel.
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Abstract
Gastrointestinal (GI) sensory-motor abnormalities are common in patients with diabetes mellitus and may involve any part of the GI tract. Abnormalities are frequently sub-clinical, and fortunately only rarely do severe and life-threatening problems occur. The pathogenesis of abnormal upper GI sensory-motor function in diabetes is incompletely understood and is most likely multi-factorial of origin. Diabetic autonomic neuropathy as well as acute suboptimal control of diabetes has been shown to impair GI motor and sensory function. Morphological and biomechanical remodeling of the GI wall develops during the duration of diabetes, and may contribute to motor and sensory dysfunction. In this review sensory and motility disorders of the upper GI tract in diabetes is discussed; and the morphological changes and biomechanical remodeling related to the sensory-motor dysfunction is also addressed.
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Affiliation(s)
- Jingbo Zhao
- Center of Excellence in Visceral Biomechanics and Pain, the Research Building room 404, Aalborg Hospital, Sdr. Skovvej 15, DK-9000 Aalborg, Denmark.
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Januszkiewicz A, Klaude M, Loré K, Andersson J, Ringdén O, Rooyackers O, Wernerman J. Determination of in vivo protein synthesis in human palatine tonsil. Clin Sci (Lond) 2005; 108:179-84. [PMID: 15535800 DOI: 10.1042/cs20040271] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The palatine tonsils are constantly exposed to ingested or inhaled antigens which, in turn, lead to a permanent activation of tonsillar immune cells, even in a basic physiological state. The aim of the present study was to investigate if the immunological activation of the human palatine tonsil is reflected by a high metabolic activity, as determined by in vivo measurement of protein synthesis. The protein synthesis rate of the tonsil was also compared with that of the circulating T-lymphocytes, the total blood mononuclear cells and the whole population of blood leucocytes. Phenotypic characterization of immune-competent cells in tonsil tissue and blood was performed by flow cytometry. Pinch tonsil biopsies were taken after induction of anaesthesia in healthy adult patients (n=12) scheduled for ear surgery, uvulopalatopharyngoplasty or nose surgery. Protein synthesis was quantitatively determined during a 90-min period by a flooding-dose technique. The in vivo protein synthesis rate in the palatine tonsils was 22.8+/-5.7%/24 h (mean+/-S.D.), whereas protein synthesis in the circulating T-lymphocytes was 10.7+/-3.4%/24 h, in mononuclear cells was 10.8+/-2.8%/24 h and in leucocytes was 3.2+/-1.2%/24 h. CD3+ lymphocytes were the most abundant cell population in the tonsil. The in vivo protein synthesis rate in human tonsils was higher compared with the circulating immune cells. This high metabolic rate may reflect the permanent immunological activity present in human tonsils, although cell phenotypes and activity markers do not explain the differences.
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Affiliation(s)
- Anna Januszkiewicz
- Department of Anaesthesiology and Intensive Care, Karolinska University Hospital at Huddinge, Karolinska Institutet, Stockholm 141 86, Sweden.
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Adiv OE, Mandel H, Shehadeh N, Knopf C, Shen-Or Z, Shamir R. Influence of co-administration of oral insulin and docosahexaenoic acid in mice. J Nutr Biochem 2004; 15:638-43. [PMID: 15542356 DOI: 10.1016/j.jnutbio.2004.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2003] [Revised: 04/20/2004] [Accepted: 05/10/2004] [Indexed: 11/23/2022]
Abstract
Insulin and docosahexaenoic acid are both present in human milk. The aim of this study was to examine the effect of co-administration of oral insulin and DHA in mice. Immediately after weaning, Balb C mice were divided into four groups of seven mice each for a period of 4 weeks. Group 1 received a chow diet only. Group 2 received a chow diet and also was given human insulin (1 unit/mL of drinking water) without docosahexaenoic acid. Group 3 received a chow diet supplemented with docosahexaenoic acid (500 mg/kg/day in the chow) and no insulin. Group 4 received a chow diet and supplementation with both human insulin and docosahexaenoic acid. At 28 days, fasting blood levels of glucose, insulin, lipids, lipid peroxidation analysis, docosahexaenoic acid plasma levels, and docosahexaenoic acid content in red blood cells were determined. We found that glucose levels were lower in the group that was supplemented with insulin only (group 2, 61.4 mg/dL +/- 2.8,mean +/- SD) and in the group that was supplemented with DHA only (group 3, 61.1 mg/dL +/- 2.0) compared to controls (group 1, 71 mg/dL +/- 6.9, P < 0.0001). Supplementation of both insulin and docosahexaenoic acid (group 4) resulted in significantly lower glucose levels (56.4 mg/dL +/- 2.6) compared to those in groups 2 and 3 (P < 0.01). No significant differences were found in lipid profile or lipid peroxidation between the groups. We conclude that adding insulin or docosahexaenoic acid to the diet of weaned Balb C mice reduces glucose blood levels. Supplementation with both substances has a synergistic effect. The presence of insulin and docosahexaenoic acid in human milk may be the cause for reduced glucose levels in breast-fed infants, in addition to the known effects of DHA on insulin sensitivity.
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Affiliation(s)
- Orly Eshach Adiv
- Meyer Children's Hospital of Haifa, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel
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Guillet C, Boirie Y, Walrand S. An integrative approach to in-vivo protein synthesis measurement: from whole tissue to specific proteins. Curr Opin Clin Nutr Metab Care 2004; 7:531-8. [PMID: 15295273 DOI: 10.1097/00075197-200409000-00005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW In-vivo estimation of protein turnover by stable isotopes in animals and humans has provided much relevant information on metabolic regulation and alterations for decades. While it was first appreciated at the whole body level in the 1970s and 1980s, new approaches have allowed inter-organ or tissue protein turnover rates to be measured, notably the incorporation rate of a labelled amino acid in muscle. These technical improvements have recently been completed by new isolation methods for the study of protein synthesis rates in various muscle and hepatic protein fractions in different blood cells or tissues such as bone and skin. RECENT FINDINGS This new insight into tissue protein synthesis opens the door for exploration of single proteins, which may be fully achievable in the near future through the combination of proteomics analysis and technical progress in mass spectrometry. This is, therefore, a new area in which not only quantitative but also qualitative changes in specific proteins will be considered for a fully integrative approach to assessing protein metabolism in physiology and disease. SUMMARY To understand the mechanisms by which protein metabolism is altered during physiopathological situations, it is of importance to measure the effect on specific proteins rather than on the body as a whole. Procedures are currently under development with the aim of isolating individuals proteins and to measure their synthesis rates by isotopic methods. Such technical progress is needed to gain a better understanding of the regulation of protein metabolism in situations in which loss of body protein mass occurs.
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Affiliation(s)
- Christelle Guillet
- Protein Energy Metabolism Unit, Auvergne University, Human Nutrition Research Centre, 58 rue Montalembert, Clermont-Ferrand cedex 1, France
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Bhor VM, Raghuram N, Sivakami S. Oxidative damage and altered antioxidant enzyme activities in the small intestine of streptozotocin-induced diabetic rats. Int J Biochem Cell Biol 2004; 36:89-97. [PMID: 14592535 DOI: 10.1016/s1357-2725(03)00142-0] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The small intestine exhibits numerous morphological and functional alterations during diabetes. Oxidative stress, a factor implicated in the pathogenesis of diabetic complications may contribute towards some of these alterations. We therefore investigated the occurrence of oxidative stress in the small intestine during diabetes by measuring the extent of oxidative damage as well as the status of the antioxidant defense system. Significant increases in lipid peroxidation (four-fold) as measured by TBARS and protein oxidation (38%) as measured by protein carbonyl content were observed after 6 weeks of diabetes. A distinct elevation in the activities of catalase (123.9%) and superoxide dismutase (71.9%) and a decline in the activity of glutathione peroxidase (67.7%) were also observed. The steady state mRNA levels of these enzymes measured by RT-PCR were, however, unchanged suggesting the absence of transcriptional control. In contrast, no changes in the levels of protein and non-protein thiols as well as the activities of glutathione reductase and glutathione-S-transferase were detected. Interestingly, decreases in the activities of xanthine oxidase (XO; 25.7%) and xanthine dehydrogenase (XDH; 42.6%) indicate that they do not contribute significantly to oxidative damage. The results thus reveal the occurrence of oxidative stress in the small intestine during diabetes and suggest its possible involvement in some of the accompanying functional alterations.
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Affiliation(s)
- V M Bhor
- Department of Life Sciences, University of Mumbai, Santacruz (East), Mumbai 400098, India
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Jaleel A, Nair KS. Identification of multiple proteins whose synthetic rates are enhanced by high amino acid levels in rat hepatocytes. Am J Physiol Endocrinol Metab 2004; 286:E950-7. [PMID: 14871883 DOI: 10.1152/ajpendo.00403.2003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Amino acids are key regulators of protein synthesis in liver. However, it remains to be determined whether amino acids stimulate synthesis of all or certain specific liver proteins. No techniques are currently available to simultaneously measure synthetic rates of several individual proteins. Here we report studies performed on rat hepatocyte primary cultures in which we used metabolic labeling with [(14)C]leucine, two-dimensional gel electrophoresis (2DGE), and tandem mass spectrometry to identify proteins that showed increased leucine incorporation when high amino acid levels were present in the media. Rat hepatocytes were isolated by in situ collagenase perfusion, cultured in serum-free medium containing insulin, and incubated for 2, 4, and 8 h in media of standard and high amino acid concentrations. SDS-PAGE and 2DGE were performed to separate proteins from cell lysates. Proteins that consistently showed increased synthesis on triplicate cultures, as detected by phosphorimaging of gels, were identified by tandem mass spectrometry. The combination of these approaches enabled the detection of 16 specific liver proteins whose synthetic rates were enhanced by increased amino acid concentration. These proteins are involved in specific functions such as translation initiation, protein folding and modification, oxidative phosphorylation, antioxidant defense, signal transduction, and transport, as well as cell motility and tissue integrity. No quantitative changes for any of these proteins were detected by gel staining, indicating that no detectable changes in protein concentration occurred. In contrast, measurable changes in synthetic rates occurred in 16 proteins. In conclusion, amino acids stimulate the synthesis of several liver proteins with important cellular functions.
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Affiliation(s)
- Abdul Jaleel
- Endocrinology Research Unit, Mayo Clinic, Rochester, Minnesota 55905, USA
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Zhao J, Yang J, Gregersen H. Biomechanical and morphometric intestinal remodelling during experimental diabetes in rats. Diabetologia 2003; 46:1688-97. [PMID: 14593459 DOI: 10.1007/s00125-003-1233-2] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2003] [Revised: 07/28/2003] [Indexed: 12/19/2022]
Abstract
AIMS/HYPOTHESIS Morphometric and passive biomechanical properties were studied in the duodenum, jejunum and ileum in 10 non-diabetic and 40 streptozotocin-induced diabetic rats. METHODS The diabetic rats were divided into groups living 4 days, 1, 2, and 4 weeks after diabetes was induced ( n=10 for each groups). The mechanical test was done as a ramp distension experiment. The intestinal diameter and length were obtained from digitised images of the intestinal segments at pre-selected pressures and at no-load and zero-stress states. Circumferential and longitudinal stresses (force per area) and strains (deformation) were computed from the length, diameter and pressure data and from the zero-stress state geometry. RESULTS The blood glucose concentration increased four- to fivefold in the diabetic rats. Streptozotocin-induced diabetes generated pronounced increase in the weight per centimetre length, wall thickness and wall cross-sectional area in all intestinal segments during diabetes ( p<0.05). Histological analysis showed that the thickness of the intestinal layers was increased in all segments during diabetes ( p<0.05). In the duodenum the opening angle did not change in the first 2 weeks and decreased after 4 weeks ( p<0.05). In the jejunum and ileum the opening angle increased after 1 week in the diabetic group. The residual strain showed the same pattern as the opening angle. Furthermore, it was found that the circumferential and longitudinal stiffness of the intestinal wall increased with the duration of diabetes ( p<0.05 and p<0.01). CONCLUSION/INTERPRETATION Morphological and biomechanical remodelling of the small intestine occurred during the development of diabetes.
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Affiliation(s)
- J Zhao
- Centre of Sensory-Motor Interaction, Aalborg University, Denmark
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Coëffier M, Claeyssens S, Hecketsweiler B, Lavoinne A, Ducrotté P, Déchelotte P. Enteral glutamine stimulates protein synthesis and decreases ubiquitin mRNA level in human gut mucosa. Am J Physiol Gastrointest Liver Physiol 2003; 285:G266-73. [PMID: 12702496 DOI: 10.1152/ajpgi.00385.2002] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Effects of glutamine on whole body and intestinal protein synthesis and on intestinal proteolysis were assessed in humans. Two groups of healthy volunteers received in a random order enteral glutamine (0.8 mmol.kg body wt(-1)x h(-1)) compared either to saline or isonitrogenous amino acids. Intravenous [2H5]phenylalanine and [13C]leucine were simultaneously infused. After gas chromatography-mass spectrometry analysis, whole body protein turnover was estimated from traced plasma amino acid fluxes and the fractional synthesis rate (FSR) of gut mucosal protein was calculated from protein and intracellular phenylalanine and leucine enrichments in duodenal biopsies. mRNA levels for ubiquitin, cathepsin D, and m-calpain were analyzed in biopsies by RT-PCR. Glutamine significantly increased mucosal protein FSR compared with saline. Glutamine and amino acids had similar effects on FSR. The mRNA level for ubiquitin was significantly decreased after glutamine infusion compared with saline and amino acids, whereas cathepsin D and m-calpain mRNA levels were not affected. Enteral glutamine stimulates mucosal protein synthesis and may attenuate ubiquitin-dependent proteolysis and thus improve protein balance in human gut.
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Affiliation(s)
- Moïse Coëffier
- Appareil Digestif, Environnement et Nutrition, Institut Fédératif de Recherche Multidisciplinaire sur les Peptides, Centre d' Investigation Clinique, Rouen, France
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Nygren J, Nair KS. Differential regulation of protein dynamics in splanchnic and skeletal muscle beds by insulin and amino acids in healthy human subjects. Diabetes 2003; 52:1377-85. [PMID: 12765947 DOI: 10.2337/diabetes.52.6.1377] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
To determine the in vivo effect of amino acids (AAs) alone or in combination with insulin on splanchnic and muscle protein dynamics, we infused stable isotope tracers of AAs in 36 healthy subjects and sampled from femoral artery and vein and hepatic vein. The subjects were randomized into six groups and were studied at baseline and during infusions of saline (group 1), insulin (0.5 mU. kg(-1). min(-1)) (group 2), insulin plus replacement of AAs (group 3) insulin plus high-dose AAs (group 4), or somatostatin and baseline replacement doses of insulin, glucagon and GH plus high dose of AAs (group 5) or saline (group 6). Insulin reduced muscle release of AAs mainly by inhibition of protein breakdown. Insulin also enhanced AA-induced muscle protein synthesis (PS) and reduced leucine transamination. The main effect of AAs on muscle was the enhancement of PS. Insulin had no effect on protein dynamics or leucine transamination in splanchnic bed. However, AAs reduced protein breakdown and increased synthesis in splanchnic bed in a dose-dependent manner. AAs also enhanced leucine transamination in both splanchnic and muscle beds. Thus insulin's anabolic effect was mostly on muscle, whereas AAs acted on muscle as well as on splanchnic bed. Insulin achieved anabolic effect in muscle by inhibition of protein breakdown, enhancing AA-induced PS, and reducing leucine transamination. AAs largely determined protein anabolism in splanchnic bed by stimulating PS and decreasing protein breakdown.
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Affiliation(s)
- Jonas Nygren
- Division of Endocrinology, Mayo Clinic and Foundation, Joseph 5-194, 200 First Street SW, Rochester, MN 55905, USA
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Zhao J, Sha H, Zhou S, Tong X, Zhuang FY, Gregersen H. Remodelling of zero-stress state of small intestine in streptozotocin-induced diabetic rats. Effect of gliclazide. Dig Liver Dis 2002; 34:707-16. [PMID: 12469798 DOI: 10.1016/s1590-8658(02)80022-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Biomechanical properties in terms of residual strains in diabetic small intestine have not been studied. Furthermore, no data have been reported on affect of gliclazide on gastrointestinal complications of diabetes. AIMS To determine remodelling of zero-stress state of small intestine in streptozotocin-induced diabetic rats and effect of gliclazide treatment. MATERIALS Morphological properties and residual strains were studied in duodenum, jejunum and ileum obtained from diabetic rats, gliclazide-treated diabetic rats and normal rats (n = 8 each group). METHODS Diabetes was induced by single intraperitoneal injection of 65 mg/kg streptozotocin. Gliclazide (10 mg kg(-1) day(-1) was injected directly into stomach lumen by intragastric gavage twice daily. Experimental period was 35 days. To approach no-load state; intestinal segments were surgically excised and cut transversely into short ring-shaped segments. Each ring was cut radially to obtain geometry of zero-stress state. Circumferential length, the wall thickness and opening angle were measured from digital images of each specimen and residual strains were computed. RESULTS Blood glucose level of diabetic group (approximately 20 mmol/l) was consistently higher than that in normal group (approximately 4 mmol/l) after induction of diabetes (p < 0.001). Gliclazide lowered average blood glucose level to between 10 and 15 mmol/l (p < 0.001). Plasma insulin levels of both diabetic groups (average between 10 and 15 pmol/l) were significantly lower than those in normal group (average approximately 18 pmol/l, p < 0.05). Wet weight per unit length and wall thickness of duodenum, jejunum and ileum were significantly higher in Diabetes group than those in Normal group (p < 0.05). Opening angle and absolute value of residual strain were significantly smaller in duodenum and larger in jejunum and ileum in Diabetes group than in Normal group (p < 0.001). Gliclazide treatment partly restored these changes (p < 0.05). CONCLUSIONS Diabetes induced morphometric and biomechanical remodelling in intestine. Gliclazide partly restored these changes.
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Affiliation(s)
- J Zhao
- China-Japan Friendship Hospital, Beijing, PR China
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30
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Davis TA, Fiorotto ML, Burrin DG, Reeds PJ, Nguyen HV, Beckett PR, Vann RC, O'Connor PMJ. Stimulation of protein synthesis by both insulin and amino acids is unique to skeletal muscle in neonatal pigs. Am J Physiol Endocrinol Metab 2002; 282:E880-90. [PMID: 11882508 DOI: 10.1152/ajpendo.00517.2001] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In neonatal pigs, the feeding-induced stimulation of protein synthesis in skeletal muscle, but not liver, can be reproduced by insulin infusion when essential amino acids and glucose are maintained at fasting levels. In the present study, 7- and 26-day-old pigs were studied during 1) fasting, 2) hyperinsulinemic-euglycemic-euaminoacidemic clamps, 3) euinsulinemic-euglycemic-hyperaminoacidemic clamps, and 4) hyperinsulinemic-euglycemic-hyperaminoacidemic clamps. Amino acids were clamped using a new amino acid mixture enriched in nonessential amino acids. Tissue protein synthesis was measured using a flooding dose of L-[4-(3)H]phenylalanine. In 7-day-old pigs, insulin infusion alone increased protein synthesis in various skeletal muscles (from +35 to +64%), with equivalent contribution of myofibrillar and sarcoplasmic proteins, as well as cardiac muscle (+50%), skin (+34%), and spleen (+26%). Amino acid infusion alone increased protein synthesis in skeletal muscles (from +28 to +50%), also with equivalent contribution of myofibrillar and sarcoplasmic proteins, as well as liver (+27%), pancreas (+28%), and kidney (+10%). An elevation of both insulin and amino acids did not have an additive effect. Similar qualitative results were obtained in 26-day-old pigs, but the magnitude of the stimulation of protein synthesis by insulin and/or amino acids was lower. The results suggest that, in the neonate, the stimulation of protein synthesis by feeding is mediated by either amino acids or insulin in most tissues; however, the feeding-induced stimulation of protein synthesis in skeletal muscle is uniquely regulated by both insulin and amino acids.
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Affiliation(s)
- Teresa A Davis
- United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, and Endocrinology and Metabolism Section, Baylor College of Medicine, Houston, Texas 77030, USA.
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Boirie Y, Short KR, Ahlman B, Charlton M, Nair KS. Tissue-specific regulation of mitochondrial and cytoplasmic protein synthesis rates by insulin. Diabetes 2001; 50:2652-8. [PMID: 11723046 DOI: 10.2337/diabetes.50.12.2652] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In vivo studies have reported conflicting effects of insulin on mixed tissue protein synthesis rates. To test the hypothesis that insulin has differential effects on synthesis rates of various protein fractions in different organs, we infused miniature swine (n = 8 per group) with saline, insulin alone (at 0.7 mU/kg(-1). min(-1)), or insulin plus an amino acid mixture for 8 h. Fractional synthesis rate (FSR) of mitochondrial and cytoplasmic proteins in liver, heart, and skeletal muscle, as well as myosin heavy chain (MHC) in muscle, were measured using L-[1-(13)C]leucine as a tracer. The FSR of mitochondrial and cytoplasmic proteins were highest in liver, followed by heart and then muscle. Mitochondrial FSR in muscle was higher during insulin and insulin plus amino acid infusions than during saline. Insulin had no significant effect on FSR of MHC in muscle. In contrast, FSR of both mitochondrial and cytoplasmic proteins were not stimulated by insulin in liver. Insulin also did not increase FSR of mitochondrial in heart, whereas insulin and amino acid stimulated FSR of cytoplasmic protein. In conclusion, insulin stimulates the synthesis of muscle mitochondrial proteins, with no significant stimulatory effect on synthesis of sarcoplasmic and MHC. These results demonstrate that insulin has different effects on synthesis rates of specific protein fractions in the liver, heart, and skeletal muscle.
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Affiliation(s)
- Y Boirie
- Division of Endocrinology and Metabolism, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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32
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Rizza RA, Jensen MD, Nair KS. Type I Diabetes Mellitus (Insulin‐Dependent Diabetes Mellitus). Compr Physiol 2001. [DOI: 10.1002/cphy.cp070236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ahlman B, Charlton M, Fu A, Berg C, O'Brien P, Nair KS. Insulin's effect on synthesis rates of liver proteins. A swine model comparing various precursors of protein synthesis. Diabetes 2001; 50:947-54. [PMID: 11334437 DOI: 10.2337/diabetes.50.5.947] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin's effect on the synthesis of liver proteins remains to be fully defined. Previous studies using various surrogate measures of amino acyl-tRNA have reported variable results of insulin's effect on liver protein synthesis. We determined the effect of insulin with or without amino acid supplementation on the synthesis rates of liver proteins (tissue, albumin, and fibrinogen) using L-[1-13C]Leu as a tracer in 24 male miniature swine. In addition, we compared the isotopic enrichment of different precursors of liver proteins with that of amino acyl-tRNA using L-[1-13C]Leu and L-[15N]Phe as tracers. Although liver tissue fluid enrichment of [13C]Leu and [15N]Phe and that of plasma [13C]ketoisocaproatic acid (KIC) were very similar to that of tRNA, plasma isotopic enrichment of both Leu and Phe were substantially higher (P < 0.01) and VLDL apolipoprotein-B100 enrichment was lower (P < 0.01) than the respective amino acyl-tRNA enrichment. Plasma KIC enrichment most accurately predicted leucyl-tRNA enrichment, whereas plasma Leu enrichment was best correlated with that of tRNA. Neither insulin alone nor insulin plus amino acid infusion had an effect on liver tissue protein synthesis. In contrast, insulin alone decreased the albumin synthesis rate, and insulin with amino acids maintained the albumin synthesis rate. Insulin with or without amino acids inhibited the fibrinogen synthesis rate. These results, based on synthetic rates using amino acyl-tRNA, were consistent with those obtained using KIC or tissue fluid Leu or Phe as precursor pools. These studies demonstrated that plasma KIC enrichment is a convenient and reliable surrogate measure of leucyl-tRNA in liver. We also concluded that insulin has differential effects on the synthesis rates of liver proteins. Whereas insulin with or without amino acid supplement has no acute effect on the synthesis of liver tissue protein, insulin has a substantial inhibitory effect on fibrinogen synthesis. In contrast, insulin administration along with amino supplement is necessary to maintain albumin synthesis rate.
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Affiliation(s)
- B Ahlman
- Endocrine Research Unit, Division of Endocrinology and Metabolism, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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Davis TA, Fiorotto ML, Beckett PR, Burrin DG, Reeds PJ, Wray-Cahen D, Nguyen HV. Differential effects of insulin on peripheral and visceral tissue protein synthesis in neonatal pigs. Am J Physiol Endocrinol Metab 2001; 280:E770-9. [PMID: 11287360 DOI: 10.1152/ajpendo.2001.280.5.e770] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We recently demonstrated in neonatal pigs that, with amino acids and glucose maintained at fasting levels, the stimulation of protein synthesis in longissimus dorsi muscle with feeding can be reproduced by a physiological rise in insulin alone. In the current report, we determine whether the response of protein synthesis to insulin in the neonatal pig is 1) present in muscles of different fiber types, 2) proportional in myofibrillar and sarcoplasmic proteins, 3) associated with increased translational efficiency and ribosome number, and 4) present in other peripheral tissues and in viscera. Hyperinsulinemic-euglycemic-amino acid clamps were performed in 7- and 26-day-old pigs infused with 0, 30, 100, or 1,000 ng. kg(-0.66). min(-1) of insulin to reproduce insulin levels present in fasted, fed, refed, and supraphysiological conditions, respectively. Tissue protein synthesis was measured using a flooding dose of L-[4-(3)H]phenylalanine. Insulin increased protein synthesis in gastrocnemius muscle and, to a lesser degree, masseter muscle. The degree of stimulation of protein synthesis by insulin was similar in myofibrillar and sarcoplasmic proteins. Insulin increased translational efficiency but had no effect on ribosome number in muscle. All of these insulin-induced changes in muscle protein synthesis decreased with age. Insulin also stimulated protein synthesis in cardiac muscle and skin but not in liver, intestine, spleen, pancreas, or kidney. The results support the hypothesis that insulin mediates the feeding-induced stimulation of myofibrillar and sarcoplasmic protein synthesis in muscles of different fiber types in the neonate by increasing the efficiency of translation. However, insulin does not appear to be involved in the feeding-induced stimulation of protein synthesis in visceral tissues. Thus different mechanisms regulate the growth of peripheral and visceral tissues in the neonate.
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Affiliation(s)
- T A Davis
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA.
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