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Stringer DM, Zahradka P, Taylor CG. Glucose transporters: cellular links to hyperglycemia in insulin resistance and diabetes. Nutr Rev 2016; 73:140-54. [PMID: 26024537 DOI: 10.1093/nutrit/nuu012] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Abnormal expression and/or function of mammalian hexose transporters contribute to the hallmark hyperglycemia of diabetes. Due to different roles in glucose handling, various organ systems possess specific transporters that may be affected during the diabetic state. Diabetes has been associated with higher rates of intestinal glucose transport, paralleled by increased expression of both active and facilitative transporters and a shift in the location of transporters within the enterocyte, events that occur independent of intestinal hyperplasia and hyperglycemia. Peripheral tissues also exhibit deregulated glucose transport in the diabetic state, most notably defective translocation of transporters to the plasma membrane and reduced capacity to clear glucose from the bloodstream. Expression of renal active and facilitative glucose transporters increases as a result of diabetes, leading to elevated rates of glucose reabsorption. However, this may be a natural response designed to combat elevated blood glucose concentrations and not necessarily a direct effect of insulin deficiency. Functional foods and nutraceuticals, by modulation of glucose transporter activity, represent a potential dietary tool to aid in the management of hyperglycemia and diabetes.
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Affiliation(s)
- Danielle M Stringer
- D.M. Stringer was with the Department of Human Nutritional Sciences, University of Manitoba, and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, MB, Canada at the time of manuscript preparation. C.G. Taylor is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada. P. Zahradka is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada.
| | - Peter Zahradka
- D.M. Stringer was with the Department of Human Nutritional Sciences, University of Manitoba, and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, MB, Canada at the time of manuscript preparation. C.G. Taylor is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada. P. Zahradka is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada
| | - Carla G Taylor
- D.M. Stringer was with the Department of Human Nutritional Sciences, University of Manitoba, and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, MB, Canada at the time of manuscript preparation. C.G. Taylor is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada. P. Zahradka is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada
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New water-soluble carbamate ester derivatives of resveratrol. Molecules 2014; 19:15900-17. [PMID: 25275336 PMCID: PMC6271179 DOI: 10.3390/molecules191015900] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 09/22/2014] [Accepted: 09/24/2014] [Indexed: 12/16/2022] Open
Abstract
Low bioavailability severely hinders exploitation of the biomedical potential of resveratrol. Extensive phase-II metabolism and poor water solubility contribute to lowering the concentrations of resveratrol in the bloodstream after oral administration. Prodrugs may provide a solution—protection of the phenolic functions hinders conjugative metabolism and can be exploited to modulate the physicochemical properties of the compound. We report here the synthesis and characterization of carbamate ester derivatives of resveratrol bearing on each nitrogen atom a methyl group and either a methoxy-poly(ethylene glycol)-350 (mPEG-350) or a butyl-glucosyl promoiety conferring high water solubility. Ex vivo absorption studies revealed that the butyl-glucosyl conjugate, unlike the mPEG-350 one, is able to permeate the intestinal wall. In vivo pharmacokinetics confirmed absorption after oral administration and showed that no hydrolysis of the carbamate groups takes place. Thus, sugar groups can be attached to resveratrol to obtain soluble derivatives maintaining to some degree the ability to permeate biomembranes, perhaps by facilitated or active transport.
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Cheng MW, Chegeni M, Kim KH, Zhang G, Benmoussa M, Quezada-Calvillo R, Nichols BL, Hamaker BR. Different sucrose-isomaltase response of Caco-2 cells to glucose and maltose suggests dietary maltose sensing. J Clin Biochem Nutr 2013; 54:55-60. [PMID: 24426192 PMCID: PMC3882486 DOI: 10.3164/jcbn.13-59] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 10/22/2013] [Indexed: 01/07/2023] Open
Abstract
Using the small intestine enterocyte Caco-2 cell model, sucrase-isomaltase (SI, the mucosal α-glucosidase complex) expression and modification were examined relative to exposure to different mono- and disaccharide glycemic carbohydrates. Caco-2/TC7 cells were grown on porous supports to post-confluence for complete differentiation, and dietary carbohydrate molecules of glucose, sucrose (disaccharide of glucose and fructose), maltose (disaccharide of two glucoses α-1,4 linked), and isomaltose (disaccharide of two glucoses α-1,6 linked) were used to treat the cells. qRT-PCR results showed that all the carbohydrate molecules induced the expression of the SI gene, though maltose (and isomaltose) showed an incremental increase in mRNA levels over time that glucose did not. Western blot analysis of the SI protein revealed that only maltose treatment induced a higher molecular weight band (Mw ~245 kDa), also at higher expression level, suggesting post-translational processing of SI, and more importantly a sensing of maltose. Further work is warranted regarding this putative sensing response as a potential control point for starch digestion and glucose generation in the small intestine.
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Affiliation(s)
- Min-Wen Cheng
- Whistler Center for Carbohydrate Research, 745 Agriculture Mall Drive, Purdue University, West Lafayette, IN 47907-2009, USA ; Department of Food Science, Purdue University, West Lafayette, IN 47907-2009, USA
| | - Mohammad Chegeni
- Whistler Center for Carbohydrate Research, 745 Agriculture Mall Drive, Purdue University, West Lafayette, IN 47907-2009, USA ; Department of Food Science, Purdue University, West Lafayette, IN 47907-2009, USA
| | - Kee-Hong Kim
- Department of Food Science, Purdue University, West Lafayette, IN 47907-2009, USA
| | - Genyi Zhang
- School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China
| | - Mustapha Benmoussa
- School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China
| | - Roberto Quezada-Calvillo
- USDA/ARS Children's Nutrition Research Center and the Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA ; Department of Chemistry, Universidad Autonoma de San Luis Potosi, San Luis Potosi 78210, Mexico
| | - Buford L Nichols
- USDA/ARS Children's Nutrition Research Center and the Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Bruce R Hamaker
- Whistler Center for Carbohydrate Research, 745 Agriculture Mall Drive, Purdue University, West Lafayette, IN 47907-2009, USA ; Department of Food Science, Purdue University, West Lafayette, IN 47907-2009, USA
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Lindblad M, Tveden-Nyborg P, Lykkesfeldt J. Regulation of vitamin C homeostasis during deficiency. Nutrients 2013; 5:2860-79. [PMID: 23892714 PMCID: PMC3775232 DOI: 10.3390/nu5082860] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 07/15/2013] [Accepted: 07/18/2013] [Indexed: 12/31/2022] Open
Abstract
Large cross-sectional population studies confirm that vitamin C deficiency is common in humans, affecting 5%–10% of adults in the industrialized world. Moreover, significant associations between poor vitamin C status and increased morbidity and mortality have consistently been observed. However, the absorption, distribution and elimination kinetics of vitamin C in vivo are highly complex, due to dose-dependent non-linearity, and the specific regulatory mechanisms are not fully understood. Particularly, little is known about how adaptive mechanisms during states of deficiency affect the overall regulation of vitamin C transport in the body. This review discusses mechanisms of vitamin C transport and potential means of regulation with special emphasis on capacity and functional properties, such as differences in the Km of vitamin C transporters in different target tissues, in some instances demonstrating a tissue-specific distribution.
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Affiliation(s)
- Maiken Lindblad
- Section of Experimental Animal Models, Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Ridebanevej 9, Frederiksberg C 1870, Denmark.
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Zheng Y, Sarr MG. Effect of the artificial sweetener, acesulfame potassium, a sweet taste receptor agonist, on glucose uptake in small intestinal cell lines. J Gastrointest Surg 2013; 17:153-8; discussion p. 158. [PMID: 22948835 PMCID: PMC3516624 DOI: 10.1007/s11605-012-1998-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 08/06/2012] [Indexed: 01/31/2023]
Abstract
INTRODUCTION Sweet taste receptors may enhance glucose absorption. AIM This study aimed to explore the cell biology of sweet taste receptors on glucose uptake. HYPOTHESIS Artificial sweeteners increase glucose uptake via activating sweet taste receptors in the enterocyte to translocate GLUT2 to the apical membrane through the PLC βII pathway. METHODS Caco-2, RIE-1, and IEC-6 cells, starved from glucose for 1 h were pre-incubated with 10 mM acesulfame potassium (AceK). Glucose uptake was measured by incubating cells for 1 to 10 min with 0.5-50 mM glucose with or without U-73122, chelerythrine, and cytochalasin B. RESULTS In Caco-2 and RIE-1 cells, 10 mM AceK increased glucose uptake by 20-30 % at glucose >25 mM, but not in lesser glucose concentrations (<10 mM), nor at 1 min or 10 min incubations. U-73122 (PLC βII inhibitor) inhibited uptake at glucose >25 mM and for 5 min incubation; chelerythrine and cytochalasin B had similar effects. No effect occurred in IEC-6 cells. Activation of sweet taste receptors had no effect on glucose uptake in low (<25 mM) glucose concentrations but increased uptake at greater concentrations (>25 mM). CONCLUSIONS Role of artificial sweeteners on glucose uptake appears to act in part by effects on the enterocyte itself.
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Grefner NM, Gromova LV, Gruzdkov AA, Komissarchik YY. Caco2 cell culture as an intestinal epithelium model to study hexose transport. ACTA ACUST UNITED AC 2012. [DOI: 10.1134/s1990519x12040062] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Zheng Y, Sarr MG. Translocation of transfected GLUT2 to the apical membrane in rat intestinal IEC-6 cells. Dig Dis Sci 2012; 57:1203-12. [PMID: 22116644 PMCID: PMC3331913 DOI: 10.1007/s10620-011-1984-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 11/10/2011] [Indexed: 02/01/2023]
Abstract
AIM In this study, we transfected the full length cDNA of glucose transporter 2 (GLUT2) into IEC-6 cells (which lack GLUT2 expression) to investigate GLUT2 translocation in enterocytes. The purpose of this study was to investigate cellular mechanisms of GLUT2 translocation and its signaling pathway. METHODS Rat GLUT2 cDNA was transfected into IEC-6 cells. Glucose uptake was measured by incubating cell monolayers with glucose (0.5-50 mM), containing (14)C-D-glucose and (3)H-L-glucose, to measure stereospecific, carrier-mediated and passive uptake. We imaged GLUT2 immunoreactivity by confocal fluorescence microscopy. We evaluated the GLUT2 inhibitor (1 mM phloretin), SGLT1 inhibitor (0.5 mM phlorizin), disrupting microtubular integrity (2 μM nocodazole and 0.5 μM cytochalasin B), protein kinase C (PKC) inhibitors (50 nM calphostin C and 10 μM chelerythrine), and PKC activator (50 nM phorbol 12-myristate 13-acetate: PMA). RESULTS In GLUT2-IEC cells, the K(m) (54.5 mM) increased compared with non-transfected IEC-6 cells (7.8 mM); phloretin (GLUT2 inhibitor) inhibited glucose uptake to that of non-transfected IEC-6 cells (P < 0.05). Nocodazole and cytochalasin B (microtubule disrupters) inhibited uptake by 43-58% only at glucose concentrations ≥25 and 50 mM and the 10-min incubations. Calphostin C (PKC inhibitor) reproduced the inhibition of nocodazole; PMA (a PKC activator) enhanced glucose uptake by 69%. Exposure to glucose increased the GFP signal at the apical membrane of GLUT-1EC cells. CONCLUSION IEC-6 cells lacking GLUT2 translocate GLUT2 apically when transfected to express GLUT2. Translocation of GLUT2 occurs through glucose stimulation via a PKC-dependent signaling pathway and requires integrity of the microtubular skeletal structure.
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Affiliation(s)
- Ye Zheng
- Department of Surgery and The Gastroenterology Research Unit, Mayo Clinic (GU 10-01), 200 1st Street SW, Rochester, MN 55905, USA.
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Chaudhry RM, Scow JS, Madhavan S, Duenes JA, Sarr MG. Acute enterocyte adaptation to luminal glucose: a posttranslational mechanism for rapid apical recruitment of the transporter GLUT2. J Gastrointest Surg 2012; 16:312-9; discussion 319. [PMID: 22068967 PMCID: PMC3265642 DOI: 10.1007/s11605-011-1752-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Accepted: 10/13/2011] [Indexed: 01/31/2023]
Abstract
BACKGROUND Glucose absorption postprandially increases markedly to levels far greater than possible by the classic glucose transporter sodium-glucose cotransporter 1 (SGLT1). HYPOTHESIS Luminal concentrations of glucose >50 mM lead to rapid, phenotypic, non-genomic adaptations by the enterocyte to recruit another transporter, glucose transporter 2 (GLUT2), to the apical membrane to increase glucose absorption. METHODS Isolated segments of jejunum were perfused in vivo with glucose-containing solutions in anesthetized rats. Carrier-mediated glucose uptake was measured in 10 and 100 mM glucose solutions (n = 6 rats each) with and without selective inhibitors of SGLT1 and GLUT2. RESULTS The mean rate of carrier-mediated glucose uptake increased in rats perfused with 100 mM versus 10 mM glucose to 13.9 ± 2.9 μmol from 2.1 ± 0.1 μmol, respectively (p < 0.0001). Using selective inhibitors, the relative contribution of GLUT2 to glucose absorption was 56% in the 100 mM concentration of glucose compared to the 10 mM concentration (27%; p < 0.01). Passive absorption accounted for 6% of total glucose absorption at 100 mM glucose. CONCLUSION A small amount of GLUT2 is active at the lesser luminal concentrations of glucose, but when exposed to concentrations of 100 mM, the enterocyte presumably changes its phenotype by recruiting GLUT2 apically to markedly augment glucose absorption.
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Affiliation(s)
- Rizwan M Chaudhry
- Department of Surgery and Gastroenterology Research Unit, Mayo Clinic (GU 10-01), 200 1st Street SW, Rochester, MN 55905, USA
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Kim Y, Park SC, Wolf BW, Hertzler SR. Combination of erythritol and fructose increases gastrointestinal symptoms in healthy adults. Nutr Res 2011; 31:836-41. [DOI: 10.1016/j.nutres.2011.09.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 09/25/2011] [Accepted: 09/29/2011] [Indexed: 12/27/2022]
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Qandeel HG, Alonso F, Hernandez DJ, Madhavan S, Duenes JA, Zheng Y, Sarr MG. Peptide absorption after massive proximal small bowel resection: mechanisms of ileal adaptation. J Gastrointest Surg 2011; 15:1537-47. [PMID: 21647767 PMCID: PMC3160514 DOI: 10.1007/s11605-011-1581-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Accepted: 05/25/2011] [Indexed: 02/07/2023]
Abstract
BACKGROUND Protein absorption occurs as di- and tri-peptides via H(+)/peptide co-transporter-1 (PepT1). AIM The aim of this study is to identify mechanisms of ileal adaptation after massive proximal enterectomy. HYPOTHESIS Ileal adaptation in uptake of peptides is mediated through upregulation of PepT1 gene expression. STUDY DESIGN Rats underwent 70% jejunoileal resection. Total mucosal cellular levels of messenger RNA (mRNA) and protein and transporter-mediated uptake per centimeter of the di-peptide glycyl-sarcosine (Gly-Sar) were compared in remnant ileum 1 and 4 weeks postoperatively to control and to 1-week sham laparotomy rats. Histomorphology, food consumption, and weights of rats were monitored. RESULTS After 70% resection, although mRNA per cell for PepT1 decreased at 1 week (p = 0.002), expression of mRNA at 4 weeks and protein at 1 and 4 weeks in remnant ileum were unchanged (p > 0.1). Ileal Gly-Sar uptake (V (max)-nanomoles per centimeter per minute, i.e., number of transporters per centimeter) increased at 1 and 4 weeks compared to control and 1-week sham (p < 0.05 each); K (m) (i.e., transporter function) was unchanged. Villous heights (millimeters) in remnant ileum increased at 1- and 4-week time points over controls (0.45 and 0.57 vs 0.21, resp; p < 0.001). CONCLUSIONS Ileal adaptation to proximal resection for peptide absorption occurs through cellular proliferation (hyperplasia) and not through cellular upregulation of PepT1 mRNA or protein per enterocyte.
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Soleimani M, Alborzi P. The role of salt in the pathogenesis of fructose-induced hypertension. Int J Nephrol 2011; 2011:392708. [PMID: 21789281 PMCID: PMC3140039 DOI: 10.4061/2011/392708] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 04/14/2011] [Accepted: 04/30/2011] [Indexed: 12/12/2022] Open
Abstract
Metabolic syndrome, as manifested by visceral obesity, hypertension, insulin resistance, and dyslipidemia, is reaching epidemic proportions in the Western World, specifically the United States. Epidemiologic studies suggest that the increased prevalence of metabolic syndrome directly correlates with an increase in the consumption of fructose, mainly in the form of high-fructose corn syrup. This inexpensive alternative to traditional sugar has been increasingly utilized by the food industry as a sweetener since the 1960s. While augmented caloric intake and sedentary lifestyles play important roles in the increasing prevalence of obesity, the pathogenesis of hypertension in metabolic syndrome remains controversial. One intriguing observation points to the role of salt in fructose-induced hypertension. Recent studies in rodents demonstrate that increased dietary fructose intake stimulates salt absorption in the small intestine and kidney tubules, resulting in a state of salt overload, thus setting in motion a cascade of events that will lead to hypertension. These studies point to a novel interaction between the fructose-absorbing transporter, Glut5, and the salt transporters, NHE3 and PAT1, in the intestine and kidney proximal tubule. This paper will focus on synergistic roles of fructose and salt in the pathogenesis of hypertension resulting from salt overload.
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Affiliation(s)
- Manoocher Soleimani
- The Center on Genetics of Transport and Epithelial Biology, University of Cincinnati, 231 Albert Sabin Way, MSB 6312, Cincinnati, OH 45267-0585, USA
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Scow JS, Tavakkolizadeh A, Zheng Y, Sarr MG. Acute "adaptation" by the small intestinal enterocyte: a posttranscriptional mechanism involving apical translocation of nutrient transporters. Surgery 2011; 149:601-5. [PMID: 21496564 DOI: 10.1016/j.surg.2011.02.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Accepted: 02/10/2011] [Indexed: 11/25/2022]
Affiliation(s)
- Jeffrey S Scow
- Department of Surgery and the Gastroenterology Research Unit, The Mayo Clinic, Rochester, MN 55905, USA
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Kellett GL. Alternative perspective on intestinal calcium absorption: proposed complementary actions of Ca(v)1.3 and TRPV6. Nutr Rev 2011; 69:347-70. [PMID: 21729089 DOI: 10.1111/j.1753-4887.2011.00395.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Transcellular models of dietary Ca(2+) absorption by the intestine assign essential roles to TRPV6 and calbindin-D(9K) . However, studies with gene-knockout mice challenge this view. Something fundamental is missing. The L-type channel Ca(v) 1.3 is located in the apical membrane from the duodenum to the ileum. In perfused rat jejunum in vivo and in Caco-2 cells, Ca(v) 1.3 mediates sodium glucose transporter 1 (SGLT1)-dependent and prolactin-induced active, transcellular Ca(2+) absorption, respectively. TRPV6 is activated by hyperpolarization and is vitamin D dependent; in contrast, Ca(v) 1.3 is activated by depolarization and is independent of calbindin-D(9K) and vitamin D. This review considers evidence supporting the idea that Ca(v) 1.3 and TRPV6 have complementary roles in the regulation of intestinal Ca(2+) absorption as depolarization and repolarization of the apical membrane occur during and between digestive periods, respectively, and as chyme moves from one intestinal segment to another and food transit times increase. Reassessment of current arguments for paracellular flow reveals that key phenomena have alternative explanations within the integrated Ca(v) 1.3/TRPV6 view of transcellular Ca(2+) absorption.
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Affiliation(s)
- George L Kellett
- Department of Biology, University of York, Heslington, United Kingdom.
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Pine bark extract inhibits glucose transport in enterocytes via mitogen-activated kinase and phosphoinositol 3-kinase. Nutrition 2011; 27:707-12. [DOI: 10.1016/j.nut.2010.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2010] [Revised: 06/10/2010] [Accepted: 07/01/2010] [Indexed: 11/18/2022]
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Azevedo MF, Lima CF, Fernandes-Ferreira M, Almeida MJ, Wilson JM, Pereira-Wilson C. Rosmarinic acid, major phenolic constituent of Greek sage herbal tea, modulates rat intestinal SGLT1 levels with effects on blood glucose. Mol Nutr Food Res 2011; 55 Suppl 1:S15-25. [PMID: 21433280 DOI: 10.1002/mnfr.201000472] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 12/08/2010] [Accepted: 01/24/2011] [Indexed: 11/08/2022]
Abstract
SCOPE Previous results suggested that the effects of Salvia fruticosa tea (SFT) drinking on glucose regulation might be at the intestinal level. Here we aim to characterize the effects of SFT treatment and of its main phenolic constituent--rosmarinic acid (RA)--on the levels and localization of the intestinal Na+/glucose cotransporter-1 (SGLT1), the facilitative glucose transporter 2 and glucagon-like peptide-1 (GLP-1). METHODS AND RESULTS Two models of SGLT1 induction in rats were used: through diabetes induction with streptozotocin (STZ) and through dietary carbohydrate manipulation. Drinking water was replaced with SFT or RA and blood parameters, liver glycogen and the levels of different proteins in enterocytes quantified. Two weeks of SFT treatment stabilized fasting blood glucose levels in STZ-diabetic animals. The increase in SGLT1 localized to the enterocyte brush-border membrane (BBM) induced by STZ treatment was significantly abrogated by treatment with SFT, without significant changes in total cellular transporter protein levels. No effects were observed on glucose transporter 2, Na(+) /K(+) -ATPase or glucagon-like peptide-1 levels by SFT. Additionally, SFT and RA for 4 days significantly inhibited the carbohydrate-induced adaptive increase of SGLT1 in BBM. CONCLUSION SFT and RA modulate the trafficking of SGLT1 to the BBM and may contribute to the control of plasma glucose.
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Affiliation(s)
- Marisa F Azevedo
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Braga, Portugal
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Nistor Baldea LA, Martineau LC, Benhaddou-Andaloussi A, Arnason JT, Lévy É, Haddad PS. Inhibition of intestinal glucose absorption by anti-diabetic medicinal plants derived from the James Bay Cree traditional pharmacopeia. JOURNAL OF ETHNOPHARMACOLOGY 2010; 132:473-482. [PMID: 20804840 DOI: 10.1016/j.jep.2010.07.055] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 06/23/2010] [Accepted: 07/06/2010] [Indexed: 05/29/2023]
Abstract
BACKGROUND Type II diabetes and obesity are major health problems worldwide and aboriginal peoples are particularly at risk. To address this problem in Canadian native populations who find modern pharmaceuticals culturally inappropriate, our team is testing the traditional pharmacopeia of the James Bay Cree for anti-diabetic and anti-obesity activities. More specifically, the aim of the present study was to define the effects of traditional plants on intestinal glucose absorption, an under-appreciated anti-hyperglycaemic and anti-obesity activity. METHODS Crude ethanol extracts of 17 Boreal forest medicinal plants were tested in vitro using the Caco-2 human enterocytic cell line and in vivo using an oral glucose tolerance test. RESULTS Thirteen of seventeen extracts were observed to significantly inhibit uptake when administered simultaneously with (3)H-deoxyglucose. Inhibition was dose-dependent and, in a few cases, even surpassed that induced by a combination of the positive controls. To validate these effects in vivo, four plant extracts were administered by intragastric gavage at 250 mg/kg to normal rats simultaneously with a 3g/kg bolus of glucose. This resulted in a decrease in peak glycaemia by approximately 40% for two of them. Similarly, only 2 extracts reduced glucose transport after long term incubation and this could be related to reductions in the expression of SGLT-1 or GLUT-2 proteins. CONCLUSIONS These findings indicate that competitive inhibition of intestinal glucose uptake can be achieved by crude extracts of medicinal plants. Such extracts could be taken with meals to control postprandial glycaemia and reduce caloric intake in high risk populations that are positively inclined towards traditional medicine.
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Affiliation(s)
- Lidia A Nistor Baldea
- Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, Quebec, Canada
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Scow JS, Iqbal CW, Jones TW, Qandeel HG, Zheng Y, Duenes JA, Nagao M, Madhavan S, Sarr MG. Absence of evidence of translocation of GLUT2 to the apical membrane of enterocytes in everted intestinal sleeves. J Surg Res 2010; 167:56-61. [PMID: 20739033 DOI: 10.1016/j.jss.2010.04.026] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 03/05/2010] [Accepted: 04/15/2010] [Indexed: 02/01/2023]
Abstract
INTRODUCTION Traditional models of intestinal glucose absorption confine GLUT2 to the basolateral membrane. Evidence suggests that GLUT2 is translocated to the apical membrane when the enterocyte is exposed to high luminal glucose concentrations. HYPOTHESIS GLUT2 translocates to the apical membrane by a PKC signaling mechanism dependent on activity of SGLT1 and the cellular cytostructure. METHODS Transporter-mediated glucose uptake was studied in rat jejunum using everted sleeves under seven conditions: Control, SGLT1 inhibition (phlorizin), GLUT2 inhibition (phloretin), both SGLT1 and GLUT2 inhibition, PKC inhibition (calphostin C or chelerythrine), and disruption of cellular cytostructure (nocodazole). Each condition was tested in iso-osmotic solutions of 1, 20, or 50 mM glucose for 1 or 5 min incubations (n = 6 rats each). RESULTS Control rats exhibited a saturable pattern of uptake at both durations of incubation. Phlorizin (P ≤ 0.006 each) inhibited markedly and phloretin (P ≤ 0.01 each) inhibited partially glucose uptake in all concentrations and time. Phloretin and phlorizin together completely inhibited uptake (P = 0.004 each). Calphostin C, chelerythrine, and nocodazole had little effect on glucose uptake at either 1 or 5 min. Inhibition of SGLT1 led to near complete cessation of transporter-mediated glucose uptake, while GLUT2 inhibition led to partial inhibition, suggesting some constitutive expression of GLUT2 in the apical membrane. Disruption of PKC signaling or cytoskeletal integrity partially inhibited transporter-mediated glucose uptake only in 1 mM glucose, suggesting a non-specific effect. CONCLUSIONS Under these conditions, it does not appear that GLUT2 is translocated to the apical membrane on the cellular cytostructure in response to PKC signaling.
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Affiliation(s)
- Jeffrey S Scow
- Mayo Clinic Department of Surgery, Rochester, Minnesota 55905, USA
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Iqbal CW, Fatima J, Duenes J, Houghton SG, Kasparek MS, Sarr MG. Expression and function of intestinal hexose transporters after small intestinal denervation. Surgery 2009; 146:100-12. [PMID: 19541015 PMCID: PMC2743990 DOI: 10.1016/j.surg.2009.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 02/23/2009] [Indexed: 12/12/2022]
Abstract
BACKGROUND The role of neural regulation in expression and function of intestinal hexose transporters is unknown. The aim of this study is to determine the role of intestinal innervation in gene expression and function of the membrane hexose transporters, SGLT1, GLUT2, and GLUT5 in the enterocyte. We hypothesize that denervation of the small intestine decreases expression of hexose transporters, which leads to decreased glucose absorption. METHODS Six groups of Lewis rats were studied (n = 6 each) as follows: control, 1 week after sham laparotomy, 1 and 8 weeks after syngeneic (no immune rejection) orthotopic small-bowel transplantation (SBT) (SBT1 and SBT8) to induce complete extrinsic denervation, and 1 and 8 weeks after selective disruption of intrinsic neural continuity to jejunoileum by gut transection and reanastomosis (T/A1 and T/A8). All tissue was harvested between 8 AM and 10 AM. In duodenum, jejunum, and ileum, mucosal messenger RNA (mRNA) levels were quantitated by real-time polymerase chain reaction (PCR), protein by Western blotting, and transporter-mediated glucose absorption using the everted sleeve technique. RESULTS Across the 6 groups, the relative gene expression of hexose transporter mRNA and protein levels were unchanged, and no difference in transporter-mediated glucose uptake was evident in any region. The glucose transporter affinity (K(m)) and functional transporter levels (V(max)) calculated for duodenum and jejunum showed no difference among the 6 groups. CONCLUSION Baseline regulation of hexose transporter function is not mediated tonically by intrinsic or extrinsic neural continuity to the jejunoileum.
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Affiliation(s)
- Corey W Iqbal
- Department of Surgery, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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Rivas CI, Zúñiga FA, Salas-Burgos A, Mardones L, Ormazabal V, Vera JC. Vitamin C transporters. J Physiol Biochem 2008; 64:357-75. [DOI: 10.1007/bf03174092] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Kellett GL, Brot-Laroche E, Mace OJ, Leturque A. Sugar absorption in the intestine: the role of GLUT2. Annu Rev Nutr 2008; 28:35-54. [PMID: 18393659 DOI: 10.1146/annurev.nutr.28.061807.155518] [Citation(s) in RCA: 325] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Intestinal glucose absorption comprises two components. One is classical active absorption mediated by the Na+/glucose cotransporter. The other is a diffusive component, formerly attributed to paracellular flow. Recent evidence, however, indicates that the diffusive component is mediated by the transient insertion of glucose transporter type 2 (GLUT2) into the apical membrane. This apical GLUT2 pathway of intestinal sugar absorption is present in species from insect to human, providing a major route at high sugar concentrations. The pathway is regulated by rapid trafficking of GLUT2 to the apical membrane induced by glucose during assimilation of a meal. Apical GLUT2 is therefore a target for multiple short-term and long-term nutrient-sensing mechanisms. These include regulation by a newly recognized pathway of calcium absorption through the nonclassical neuroendocrine l-type channel Cav1.3 operating during digestion, activation of intestinal sweet taste receptors by natural sugars and artificial sweeteners, paracrine and endocrine hormones, especially insulin and GLP-2, and stress. Permanent apical GLUT2, resulting in increased sugar absorption, is a characteristic of experimental diabetes and of insulin-resistant states induced by fructose and fat. The nutritional consequences of apical and basolateral GLUT2 regulation are discussed in the context of Western diet, processed foods containing artificial sweeteners, obesity, and diabetes.
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Affiliation(s)
- George L Kellett
- Department of Biology (Area 3), The University of York, York YO10 5YW, United Kingdom.
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Callies C, Cooper TG, Yeung CH. Channels for water efflux and influx involved in volume regulation of murine spermatozoa. Reproduction 2008; 136:401-10. [PMID: 18614623 DOI: 10.1530/rep-08-0149] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The nature of the membrane channels mediating water transport in murine spermatozoa adjusting to anisotonic conditions was investigated. The volume of spermatozoa subjected to physiologically relevant hypotonic conditions either simultaneously, or after isotonic pre-incubation, with putative water transport inhibitors was monitored. Experiments in which quinine prevented osmolyte efflux, and thus regulatory volume decrease (RVD), revealed whether water influx or efflux was being inhibited. There was no evidence that sodium-dependent solute transporters or facilitative glucose transporters were involved in water transport during RVD of murine spermatozoa since phloretin, cytochalasin B and phloridzin had no effect on volume regulation. However, there was evidence that Hg(2+)- and Ag(+)-sensitive channels were involved in water transport and the possibility that they include aquaporin 8 is discussed. Toxic effects of these heavy metals were ruled out by evidence that mitochondrial poisons had no such effect on volume regulation.
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Affiliation(s)
- C Callies
- Centre of Reproductive Medicine and Andrology of the University, Domagkstrasse 11, D-48129 Münster, Germany
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Han HJ, Heo JS, Lee YJ, Min JJ, Park KS. High glucose-induced inhibition of 2-deoxyglucose uptake is mediated by cAMP, protein kinase C, oxidative stress and mitogen-activated protein kinases in mouse embryonic stem cells. Clin Exp Pharmacol Physiol 2006; 33:211-20. [PMID: 16487264 DOI: 10.1111/j.1440-1681.2006.04348.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Abnormally high glucose levels may play an important role in early embryo development and function. In the present study, we investigated the effect of high glucose on 2-deoxyglucose (2-DG) uptake and its related signalling pathway in mouse embryonic stem (ES) cells. 2. 2-Deoxyglucose uptake was maximally inhibited by 25 mmol/L glucose after 24 h treatment. However, 25 mmol/L mannitol and dextran did not affect 2-DG uptake. Indeed, 25 mmol/L glucose decreased GLUT-1 mRNA and protein levels. The glucose (25 mmol/L)-induced inhibition of 2-DG uptake was blocked by pertussis toxin (a G(i)-protein inhibitor; 2 ng/mL), SQ 22,536 (an adenylate cyclase inhibitor; 10(-6) mol/L) and the protein kinase (PK) A inhibitor myristoylated PKI amide-(14-22) (10(-6) mol/L). Indeed, 25 mmol/L glucose increased intracellular cAMP content. 3. Furthermore, 25 mmol/L glucose-induced inhibition of 2-DG uptake was prevented by 10(-4) mol/L neomycin or 10(-6) mol/L U 73,122 (phospholipase C (PLC) inhibitors) and staurosporine or bisindolylmaleimide I (protein kinase (PK) C inhibitors). At 25 mmol/L, glucose increased translocation of PKC from the cytoplasmic fraction to the membrane fraction. The 25 mmol/L glucose-induced inhibition of 2-DG uptake and GLUT-1 protein levels was blocked by SQ 22,536, bisindolylmaleimide I or combined treatment. In addition, 25 mmol/L glucose increased cellular reactive oxygen species and the glucose-induced inhibition of 2-DG uptake were blocked by the anti-oxidants N-acetylcysteine (NAC; 10(-5) mol/L) or taurine (2 yen 10(-3) mol/L). 4. Glucose (25 mmol/L) activated p38 mitogen-activated protein kinase (MAPK) and p44/42 MAPK. Staurosporine (10(-6) mol/L), NAC (10(-5) mol/L) and PD 98059 (10(-7) mol/L) attenuated the phosphorylation of p44/42 MAPK. Both SB 203580 (a p38 MAPK inhibitor; 10(-7) mol/L) and PD 98059 (a p44/42 MAPK inhibitor; 10(-7) mol/L) blocked 25 mmol/L glucose-induced inhibition of 2-DG uptake. 5. In conclusion, high glucose inhibits 2-DG uptake through cAMP, PLC/PKC, oxidative stress or MAPK in mouse ES cells.
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Affiliation(s)
- Ho Jae Han
- Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju, Korea.
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Abstract
Carbohydrates are an important component of the diet. The carbohydrates that we ingest range from simple monosaccharides (glucose, fructose and galactose) to disaccharides (lactose, sucrose) to complex polysaccharides. Most carbohydrates are digested by salivary and pancreatic amylases, and are further broken down into monosaccharides by enzymes in the brush border membrane (BBM) of enterocytes. For example, lactase-phloridzin hydrolase and sucrase-isomaltase are two disaccharidases involved in the hydrolysis of nutritionally important disaccharides. Once monosaccharides are presented to the BBM, mature enterocytes expressing nutrient transporters transport the sugars into the enterocytes. This paper reviews the early studies that contributed to the development of a working model of intestinal sugar transport, and details the recent advances made in understanding the process by which sugars are absorbed in the intestine.
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Affiliation(s)
- Laurie A Drozdowski
- Division of Gastroenterology, Department of Medicine, University of Alberta, 5150 Dentistry Pharmacy Building, Edmonton, Alberta T6G 2N8, Canada.
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Thiesen AL, Tappenden KA, McBurney MI, Clandinin MT, Keelan M, Thomson BK, Wild GE, Thomson AB. Dietary lipids alter the effect of steroids on the transport of glucose after intestinal resection: Part I. Phenotypic changes and expression of transporters. J Pediatr Surg 2003; 38:150-60. [PMID: 12596094 DOI: 10.1053/jpsu.2003.50034] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND/PURPOSE Glucocorticosteroids alter the function of the intestine. This study was undertaken to assess the effect on D-glucose uptake of budesonide (Bud), prednisone (Pred), or dexamethasone (Dex) in animals with a 50% intestinal resection and fed chow or a diet enriched with saturated (SFA) or polyunsaturated fatty acids (PUFA). METHODS In vitro ring uptake technique, Western blots, and Northern blots were performed. RESULTS Bud increased the jejunal D-glucose uptake, and this effect was prevented by feeding PUFA. SGLT1 and Na+/K+ ATPase protein and mRNA abundance did not correlate with the change in the rate of uptake of glucose. CONCLUSIONS (1) Bud increased the jejunal glucose uptake, (2) the activity of the sugar transporter does not correlate with the abundance of protein or their respective mRNAs, (3) th Bud effect on glucose uptake is prevented by feeding PUFA. Thus, the desired intestinal adaptive response after intestinal resection may be enhanced further by the administration of the locally acting steroid budesonide and by feeding a saturated compared with a polyunsaturated fatty acid diet.
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Affiliation(s)
- Aducio L Thiesen
- Nutrition and Metabolism Research Group, Division of Gastroenterology, Department of Medicine, University of Alberta, Edmonton, Canada
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Debnam ES, Grimble GK. Methods for assessing intestinal absorptive function in relation to enteral nutrition. Curr Opin Clin Nutr Metab Care 2001; 4:355-67. [PMID: 11568496 DOI: 10.1097/00075197-200109000-00005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The success of nasoenteral nutrition support can be limited by intestinal impairment. In particular, reduced absorptive area, mucosal atrophy and abnormal motility may reduce absorption of macronutrients and micronutrients, and diarrhoea remains a commonly encountered complication. We review how basic physiological techniques can be used to investigate such pathophysiology. Lumenal nutrients control mucosal growth, expression of mucosal transporters and regional gut motility. Cell biology techniques now complement classical intestinal perfusion methods in determining the 'safety factor' of excess absorptive capacity. The controversial role of the sodium-glucose linked transporter in dietary glucose assimilation is described in terms of its control, its true function and its role in uptake of other solutes. Techniques that involve brush-border membrane vesicles, Caco-2 cells, mucosal immunohistochemistry and gene expression probes are described. Together, these techniques describe a picture of an organ with remarkable ability to maintain digestive and absorptive function in response to a wide variety of nutritional intakes, often in the face of inflammatory illness.
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Affiliation(s)
- E S Debnam
- Department of Physiology, University College, London, UK.
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Abstract
Malnutrition is a serious problem, and malabsorption of nutrients is believed to be partially responsible for its prevalence. A wide variety of innovative methods have been developed to study gastrointestinal transport function. Some of the first research into gastrointestinal function was conducted in the 1700's with animal and human models. Methodological advancements continue to allow scientists to innovatively assess gastrointestinal function in animal models, cellular preparations and clinical settings. For this update, the methods are divided into in vivo, ex vivo, isolated cells and membranes, and molecular biology approaches. The in vivo methods discussed include animal and human models to measure nutrient disappearance, catheterized animal models, models with isolated intestinal segments, and a new procedure for sampling luminal fluid from patients. The ex vivo approaches discussed obtain measurements with intact tissue, such as the everted sleeves method and Ussing chambers. The utility of novel cellular preparations, membrane fractionation procedures and various molecular biology techniques is included. Various aspects of these methods are evaluated to provide a detailed overview of recent methodological developments.
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Affiliation(s)
- D M Albin
- Division of Nutritional Sciences and Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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Kasahara M, Maeda M, Hayashi S, Mori Y, Abe T. A missense mutation in the Na(+)/glucose cotransporter gene SGLT1 in a patient with congenital glucose-galactose malabsorption: normal trafficking but inactivation of the mutant protein. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1536:141-7. [PMID: 11406349 DOI: 10.1016/s0925-4439(01)00043-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Na(+)/glucose cotransporter gene SGLT1 was analyzed in a Japanese patient with congenital glucose-galactose malabsorption. Genomic DNA was used as a template for amplification by the polymerase chain reaction of each of the 15 exons of SGLT1. The amplification products were cloned and sequenced. About half of the exon 5 clones of the patient contained a C-->T transition, resulting in an Arg(135)-->Trp mutation, whereas the remaining clones contained the normal exon 5 sequence. In addition, whereas some exon 12 clones exhibited the normal sequence, others showed a CAgtaggtatcatc-->CAgacc mutation at the splice donor site of intron 12 that may result either in the skipping of exon 12 or in read-through of intron 12. Neither the Arg(135)-->Trp mutant nor either of the possible intron 12 mutant proteins exhibited Na(+)-dependent glucose transport activity when expressed in Xenopus oocytes. Immunocytochemical analysis indicated, however, that the Arg(135)-->Trp mutant was localized to the oocyte plasma membrane. DNA sequence analysis revealed that the missense mutation in exon 5 and the splice site mutation in intron 12 were inherited from the proband's father and mother, respectively. These results indicate that the patient is a compound heterozygote for this disease, and that the Arg(135)-->Trp mutant of SGLT1 undergoes normal trafficking to the plasma membrane but is non-functional.
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Affiliation(s)
- M Kasahara
- Laboratory of Biophysics, School of Medicine, Teikyo University, hachioji, Tokyo, Japan.
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