Short chain fatty acids (SCFAs) are produced in the colonic lumen by bacterial fermentation of dietary fiber. SCFAs serve a key role as the metabolic fuel for the colonocytes and are important for the integrity of colonic epithelium. A major consequence of reduction in intracellular SCFA oxidation results in metabolic starvation and mucosal atrophy. In fact, local starving of the colon plays a critical role in the etiology of inflammatory bowel diseases. This warrants the need for a better understanding of the regulation of their absorption. Over the last 15 years our group has been involved in understanding the membrane and molecular basis of SCFA absorption in the human intestine. Studies during the previous funding cycles have demonstrated critical role of the monocarboxylate transporter 1 (MCT1) in SCFA absorption and has defined the mechanisms of its regulation. Our extensive preliminary studies, in the current application, showed a role of a novel nutrient- sensing mechanism involving GPR109a (a G-protein coupled SCFA receptor in human colonocyte apical membranes) and leading to translocation of MCT1 to the apical membrane domains in response to high levels of luminal SCFAs. Our preliminary data utilizing polarized C2BBE cells showed that acute treatment with butyrate (10 mM, 60-120 min) increased MCT1 function and association with CD147 (the ancillary chaperon protein), enhanced apical surface MCT1 level, and decreased intracellular cAMP levels. Further, MCT1 function was reduced by cAMP agonists forskolin and dibutyryl cAMP and enhanced by nicotinic acid (a GPR109A agonist). Ex vivo studies in normal and soluble fiber pectin fed rats also showed evidence for nutrient sensing. In fiber fed rats, the MCT1 expression was increased along with a marked increase in its translocation to the apical membranes. Therefore, we propose a novel hypothesis that the activation of GPR109A by high levels of luminal SCFAs represents a nutrient-sensing mechanism that increases the level of MCT1 on the apical membranes and involves distinct signaling and trafficking pathways. We will test this hypothesis by systematic set of approaches utilizing both in vitro and in vivo models and state-of- the-art imaging and advanced molecular biology techniques. Studies proposed in Specific Aim 1 will investigate the mechanisms of acute regulation of MCT1 by SCFAs in model human intestinal C2BBE and rat intestinal IEC-6 cell monolayers;
Specific Aim 2 will focus on elucidating mechanisms of substrate-induced trafficking of MCT1 in polarized C2BBE/ IEC-6 cells;and studies in Specific Aim 3 will examine the effects of short-term as well as long-term SCFAs on MCT1 function and membrane targeting mechanisms in in vivo rat models. These studies should enhance our understanding of cellular pathways upregulating MCT1 function in response to substrates and provide the basis for its variable membrane localization. In addition, given that MCT1 is down-regulated in inflammation, defining the molecular mechanisms involved in the up-regulation of MCT1 as proposed here could identify novel targets for the treatment of intestinal inflammatory disorders.

Public Health Relevance

Fiber in our diet is broken down into short chain fatty acids (SCFAs) by normal bacteria in the large intestine (colon). These short chain fatty acids serve as important nutrients for maintaining the health of the colonic wall. Deficiency of these nutrients has been shown to result in local starvation of the colonic wall and contributes to the development of inflammatory bowel diseases. The studies proposed in this application will test a novel hypothesis that SCFAs can regulate the targeting of the SCFA transporter Mono Carboxylate Transporter-1 via distinct trafficking mechanisms. These studies may identify novel targets for the treatment of inflammatory bowel diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK054016-16
Application #
8715769
Study Section
Clinical, Integrative and Molecular Gastroenterology Study Section (CIMG)
Program Officer
Grey, Michael J
Project Start
1998-06-01
Project End
2017-08-31
Budget Start
2014-09-01
Budget End
2015-08-31
Support Year
16
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of Illinois at Chicago
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
City
Chicago
State
IL
Country
United States
Zip Code
60612
Priyamvada, Shubha; Anbazhagan, Arivarasu N; Kumar, Anoop et al. (2016) Lactobacillus acidophilus stimulates intestinal P-glycoprotein expression via a c-Fos/c-Jun-dependent mechanism in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 310:G599-608
Asghar, M Nadeem; Priyamvada, Shubha; Nyström, Joel H et al. (2016) Keratin 8 knockdown leads to loss of the chloride transporter DRA in the colon. Am J Physiol Gastrointest Liver Physiol 310:G1147-54
Anbazhagan, Arivarasu N; Priyamvada, Shubha; Gujral, Tarunmeet et al. (2016) A novel anti-inflammatory role of GPR120 in intestinal epithelial cells. Am J Physiol Cell Physiol 310:C612-21
Anbazhagan, Arivarasu N; Priyamvada, Shubha; Alakkam, Anas et al. (2016) Transcriptional modulation of SLC26A3 (DRA) by sphingosine-1-phosphate. Am J Physiol Gastrointest Liver Physiol 310:G1028-35
Gujral, Tarunmeet; Kumar, Anoop; Priyamvada, Shubha et al. (2015) Mechanisms of DRA recycling in intestinal epithelial cells: effect of enteropathogenic E. coli. Am J Physiol Cell Physiol 309:C835-46
Priyamvada, Shubha; Anbazhagan, Arivarasu N; Gujral, Tarunmeet et al. (2015) All-trans-retinoic Acid Increases SLC26A3 DRA (Down-regulated in Adenoma) Expression in Intestinal Epithelial Cells via HNF-1β. J Biol Chem 290:15066-77
Kumar, Anoop; Alrefai, Waddah A; Borthakur, Alip et al. (2015) Lactobacillus acidophilus counteracts enteropathogenic E. coli-induced inhibition of butyrate uptake in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 309:G602-7
Nazir, Saad; Kumar, Anoop; Chatterjee, Ishita et al. (2015) Mechanisms of Intestinal Serotonin Transporter (SERT) Upregulation by TGF-β1 Induced Non-Smad Pathways. PLoS One 10:e0120447
Muthusamy, Saminathan; Malhotra, Pooja; Hosameddin, Mobashir et al. (2015) N-glycosylation is essential for ileal ASBT function and protection against proteases. Am J Physiol Cell Physiol 308:C964-71
Priyamvada, Shubha; Gomes, Rochelle; Gill, Ravinder K et al. (2015) Mechanisms Underlying Dysregulation of Electrolyte Absorption in Inflammatory Bowel Disease-Associated Diarrhea. Inflamm Bowel Dis 21:2926-35

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