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Gastroesophageal Reflux Induces Protein Adducts in the Esophagus.
Caspa Gokulan R, Adcock JM, Zagol-Ikapitte I, Mernaugh R, Williams P, Washington KM, Boutaud O, Oates JA, Dikalov SI, Zaika AI
(2019) Cell Mol Gastroenterol Hepatol 7: 480-482.e7
MeSH Terms: Acetylcysteine, Animals, Benzylamines, Bile Acids and Salts, Cell Line, Cyclic N-Oxides, Esophagus, Gastroesophageal Reflux, Humans, Lipids, Mice, Spin Labels, Tumor Suppressor Protein p53
Added March 26, 2019
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1 Members
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13 MeSH Terms
Role of Bile Acids and GLP-1 in Mediating the Metabolic Improvements of Bariatric Surgery.
Albaugh VL, Banan B, Antoun J, Xiong Y, Guo Y, Ping J, Alikhan M, Clements BA, Abumrad NN, Flynn CR
(2019) Gastroenterology 156: 1041-1051.e4
MeSH Terms: Anastomosis, Surgical, Animals, Anticholesteremic Agents, Bariatric Surgery, Bile Acids and Salts, Blood Glucose, Cholestyramine Resin, Diet, High-Fat, Gallbladder, Glucagon-Like Peptide 1, Glucagon-Like Peptide-1 Receptor, Glucose Tolerance Test, Ileum, Insulin Resistance, Intestines, Lymph, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Receptors, Cytoplasmic and Nuclear, Receptors, G-Protein-Coupled, Signal Transduction, Verrucomicrobia, Weight Loss
Show Abstract · Added January 4, 2019
BACKGROUND & AIMS - Bile diversion to the ileum (GB-IL) has strikingly similar metabolic and satiating effects to Roux-en-Y gastric bypass (RYGB) in rodent obesity models. The metabolic benefits of these procedures are thought to be mediated by increased bile acids, although parallel changes in body weight and other confounding variables limit this interpretation.
METHODS - Global G protein-coupled bile acid receptor-1 null (Tgr5) and intestinal-specific farnesoid X receptor null (Fxr) mice on high-fat diet as well as wild-type C57BL/6 and glucagon-like polypeptide 1 receptor deficient (Glp-1r) mice on chow diet were characterized following GB-IL.
RESULTS - GB-IL induced weight loss and improved oral glucose tolerance in Tgr5, but not Fxr mice fed a high-fat diet, suggesting a role for intestinal Fxr. GB-IL in wild-type, chow-fed mice prompted weight-independent improvements in glycemia and glucose tolerance secondary to augmented insulin responsiveness. Improvements were concomitant with increased levels of lymphatic GLP-1 in the fasted state and increased levels of intestinal Akkermansia muciniphila. Improvements in fasting glycemia after GB-IL were mitigated with exendin-9, a GLP-1 receptor antagonist, or cholestyramine, a bile acid sequestrant. The glucoregulatory effects of GB-IL were lost in whole-body Glp-1r mice.
CONCLUSIONS - Bile diversion to the ileum improves glucose homeostasis via an intestinal Fxr-Glp-1 axis. Altered intestinal bile acid availability, independent of weight loss, and intestinal Akkermansia muciniphila appear to mediate the metabolic changes observed after bariatric surgery and might be manipulated for treatment of obesity and diabetes.
Copyright © 2019 AGA Institute. Published by Elsevier Inc. All rights reserved.
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2 Members
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25 MeSH Terms
CD36 Modulates Fasting and Preabsorptive Hormone and Bile Acid Levels.
Shibao CA, Celedonio JE, Tamboli R, Sidani R, Love-Gregory L, Pietka T, Xiong Y, Wei Y, Abumrad NN, Abumrad NA, Flynn CR
(2018) J Clin Endocrinol Metab 103: 1856-1866
MeSH Terms: Adult, African Americans, Bile Acids and Salts, CD36 Antigens, Case-Control Studies, Energy Metabolism, Fasting, Female, Genotype, Hormones, Humans, Intestinal Absorption, Middle Aged, Polymorphism, Single Nucleotide
Show Abstract · Added May 14, 2018
Context - Abnormal fatty acid (FA) metabolism contributes to diabetes and cardiovascular disease. The FA receptor CD36 has been linked to risk of metabolic syndrome. In rodents CD36 regulates various aspects of fat metabolism, but whether it has similar actions in humans is unknown. We examined the impact of a coding single-nucleotide polymorphism in CD36 on postprandial hormone and bile acid (BA) responses.
Objective - To examine whether the minor allele (G) of coding CD36 variant rs3211938 (G/T), which reduces CD36 level by ∼50%, influences hormonal responses to a high-fat meal (HFM).
Design - Obese African American (AA) women carriers of the G allele of rs3211938 (G/T) and weight-matched noncarriers (T/T) were studied before and after a HFM.
Setting - Two-center study.
Participants - Obese AA women.
Intervention - HFM.
Main Outcome Measures - Early preabsorptive responses (10 minutes) and extended excursions in plasma hormones [C-peptide, insulin, incretins, ghrelin fibroblast growth factor (FGF)19, FGF21], BAs, and serum lipoproteins (chylomicrons, very-low-density lipoprotein) were determined.
Results - At fasting, G-allele carriers had significantly reduced cholesterol and glycodeoxycholic acid and consistent but nonsignificant reductions of serum lipoproteins. Levels of GLP-1 and pancreatic polypeptide (PP) were reduced 60% to 70% and those of total BAs were 1.8-fold higher. After the meal, G-allele carriers displayed attenuated early (-10 to 10 minute) responses in insulin, C-peptide, GLP-1, gastric inhibitory peptide, and PP. BAs exhibited divergent trends in G allele carriers vs noncarriers concomitant with differential FGF19 responses.
Conclusions - CD36 plays an important role in the preabsorptive hormone and BA responses that coordinate brain and gut regulation of energy metabolism.
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14 MeSH Terms
Activation of NADPH oxidases leads to DNA damage in esophageal cells.
Bhardwaj V, Gokulan RC, Horvat A, Yermalitskaya L, Korolkova O, Washington KM, El-Rifai W, Dikalov SI, Zaika AI
(2017) Sci Rep 7: 9956
MeSH Terms: Barrett Esophagus, Bile Acids and Salts, Cells, Cultured, DNA Damage, Epithelial Cells, Humans, NADPH Oxidase 1, NADPH Oxidase 2, Reactive Oxygen Species
Show Abstract · Added March 26, 2019
Gastroesophageal reflux disease (GERD) is the strongest known risk factor for esophageal adenocarcinoma. In the center of tumorigenic events caused by GERD is repeated damage of esophageal tissues by the refluxate. In this study, we focused on a genotoxic aspect of exposure of esophageal cells to acidic bile reflux (BA/A). Analyzing cells generated from patients with Barrett's esophagus and human esophageal specimens, we found that BA/A cause significant DNA damage that is mediated by reactive-oxygen species. ROS originate from mitochondria and NADPH oxidases. We specifically identified NOX1 and NOX2 enzymes to be responsible for ROS generation. Inhibition of NOX2 and NOX1 with siRNA or chemical inhibitors significantly suppresses ROS production and DNA damage induced by BA/A. Mechanistically, our data showed that exposure of esophageal cells to acidic bile salts induces phosphorylation of the p47 subunit of NOX2 and its translocation to the cellular membrane. This process is mediated by protein kinase C, which is activated by BA/A. Taken together, our studies suggest that inhibition of ROS induced by reflux can be a useful strategy for preventing DNA damage and decreasing the risk of tumorigenic transformation caused by GERD.
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1 Members
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9 MeSH Terms
Bile acids and bariatric surgery.
Albaugh VL, Banan B, Ajouz H, Abumrad NN, Flynn CR
(2017) Mol Aspects Med 56: 75-89
MeSH Terms: Animals, Bile Acids and Salts, Diabetes Mellitus, Type 2, Enterohepatic Circulation, Gastrectomy, Gastric Bypass, Gastrointestinal Microbiome, Gene Expression Regulation, Glucose, Homeostasis, Humans, Insulin Resistance, Obesity, Morbid, Receptors, Cytoplasmic and Nuclear, Receptors, G-Protein-Coupled, Rodentia, Signal Transduction
Show Abstract · Added June 6, 2017
Bariatric surgery, specifically Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), are the most effective and durable treatments for morbid obesity and potentially a viable treatment for type 2 diabetes (T2D). The resolution rate of T2D following these procedures is between 40 and 80% and far surpasses that achieved by medical management alone. The molecular basis for this improvement is not entirely understood, but has been attributed in part to the altered enterohepatic circulation of bile acids. In this review we highlight how bile acids potentially contribute to improved lipid and glucose homeostasis, insulin sensitivity and energy expenditure after these procedures. The impact of altered bile acid levels in enterohepatic circulation is also associated with changes in gut microflora, which may further contribute to some of these beneficial effects. We highlight the beneficial effects of experimental surgical procedures in rodents that alter bile secretory flow without gastric restriction or altering nutrient flow. This information suggests a role for bile acids beyond dietary fat emulsification in altering whole body glucose and lipid metabolism strongly, and also suggests emerging roles for the activation of the bile acid receptors farnesoid x receptor (FXR) and G-protein coupled bile acid receptor (TGR5) in these improvements. The limitations of rodent studies and the current state of our understanding is reviewed and the potential effects of bile acids mediating the short- and long-term metabolic improvements after bariatric surgery is critically examined.
Copyright © 2017 Elsevier Ltd. All rights reserved.
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3 Members
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17 MeSH Terms
Prevention of DNA damage in Barrett's esophageal cells exposed to acidic bile salts.
Bhardwaj V, Horvat A, Korolkova O, Washington MK, El-Rifai W, Dikalov SI, Zaika AI
(2016) Carcinogenesis 37: 1161-1169
MeSH Terms: Acetophenones, Acids, Adenocarcinoma, Antioxidants, BRCA1 Protein, Barrett Esophagus, Bile Acids and Salts, Cell Line, Tumor, DNA Damage, DNA Repair, Esophageal Neoplasms, Gastric Acid, Gastroesophageal Reflux, Humans, Reactive Oxygen Species
Show Abstract · Added March 26, 2019
Esophageal adenocarcinoma (EA) is one of the fastest rising tumors in the USA. The major risk factor for EA is gastroesophageal reflux disease (GERD). During GERD, esophageal cells are exposed to refluxate which contains gastric acid frequently mixed with duodenal bile. This may lead to mucosal injury and Barrett's metaplasia (BE) that are important factors contributing to development of EA. In this study, we investigated DNA damage in BE cells exposed to acidic bile salts and explored for potential protective strategies. Exposure of BE cells to acidic bile salts led to significant DNA damage, which in turn, was due to generation of reactive oxygen species (ROS). We found that acidic bile salts induce a rapid increase in superoxide radicals and hydrogen peroxide, which were determined using electron paramagnetic resonance spectroscopy and Amplex Red assay. Analyzing a panel of natural antioxidants, we identified apocynin to be the most effective in protecting esophageal cells from DNA damage induced by acidic bile salts. Mechanistic analyses showed that apocynin inhibited ROS generation and increases the DNA repair capacity of BE cells. We identified BRCA1 and p73 proteins as apocynin targets. Downregulation of p73 inhibited the protective effect of apocynin. Taken together, our results suggest potential application of natural compounds such as apocynin for prevention of reflux-induced DNA damage and GERD-associated tumorigenesis.
© The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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MeSH Terms
APE1-mediated DNA damage repair provides survival advantage for esophageal adenocarcinoma cells in response to acidic bile salts.
Hong J, Chen Z, Peng D, Zaika A, Revetta F, Washington MK, Belkhiri A, El-Rifai W
(2016) Oncotarget 7: 16688-702
MeSH Terms: Adenocarcinoma, Barrett Esophagus, Bile Acids and Salts, Cell Line, Tumor, Cell Survival, DNA Damage, DNA Repair, DNA-(Apurinic or Apyrimidinic Site) Lyase, Esophageal Neoplasms, Gastroesophageal Reflux, Humans
Show Abstract · Added April 8, 2016
Chronic Gastroesophageal Reflux Disease (GERD) is the main risk factor for the development of Barrett's esophagus (BE) and its progression to esophageal adenocarcinoma (EAC). Accordingly, EAC cells are subjected to high levels of oxidative stress and subsequent DNA damage. In this study, we investigated the expression and role of Apurinic/apyrimidinic endonuclease 1 (APE1) protein in promoting cancer cell survival by counteracting the lethal effects of acidic bile salts (ABS)-induced DNA damage. Immunohistochemistry analysis of human tissue samples demonstrated overexpression of APE1 in more than half of EACs (70 of 130), as compared to normal esophagus and non-dysplastic BE samples (P < 0.01). To mimic in vivo conditions, we treated in vitro cell models with a cocktail of ABS. The knockdown of endogenous APE1 in EAC FLO-1 cells significantly increased oxidative DNA damage (P < 0.01) and DNA single- and double-strand breaks (P < 0.01), whereas overexpression of APE1 in EAC OE33 cells reversed these effects. Annexin V/PI staining indicated that the APE1 expression in OE33 cells protects against ABS-induced apoptosis. In contrast, knockdown of endogenous APE1 in FLO-1 cells increased apoptosis under the same conditions. Mechanistic investigations indicated that the pro-survival function of APE1 was associated with the regulation of stress response c-Jun N-terminal protein kinase (JNK) and p38 kinases. Pharmacological inhibition of APE1 base excision repair (BER) function decreased cell survival and enhanced activation of JNK and p38 kinases by ABS. Our findings suggest that constitutive overexpression of APE1 in EAC may be an adaptive pro-survival mechanism that protects against the genotoxic lethal effects of bile reflux episodes.
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3 Members
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11 MeSH Terms
Bile diversion to the distal small intestine has comparable metabolic benefits to bariatric surgery.
Flynn CR, Albaugh VL, Cai S, Cheung-Flynn J, Williams PE, Brucker RM, Bordenstein SR, Guo Y, Wasserman DH, Abumrad NN
(2015) Nat Commun 6: 7715
MeSH Terms: Adaptation, Biological, Anastomosis, Surgical, Animals, Bariatric Surgery, Bile Acids and Salts, Carrier Proteins, Disease Models, Animal, Energy Metabolism, Fibroblast Growth Factors, Gallbladder, Gastrointestinal Microbiome, Intestine, Small, Liver, Male, Membrane Glycoproteins, Mice, Inbred C57BL, Obesity, Random Allocation
Show Abstract · Added August 26, 2015
Roux-en-Y gastric bypass (RYGB) is highly effective in reversing obesity and associated diabetes. Recent observations in humans suggest a contributing role of increased circulating bile acids in mediating such effects. Here we use a diet-induced obesity (DIO) mouse model and compare metabolic remission when bile flow is diverted through a gallbladder anastomosis to jejunum, ileum or duodenum (sham control). We find that only bile diversion to the ileum results in physiologic changes similar to RYGB, including sustained improvements in weight, glucose tolerance and hepatic steatosis despite differential effects on hepatic gene expression. Circulating free fatty acids and triglycerides decrease while bile acids increase, particularly conjugated tauro-β-muricholic acid, an FXR antagonist. Activity of the hepatic FXR/FGF15 signalling axis is reduced and associated with altered gut microbiota. Thus bile diversion, independent of surgical rearrangement of the gastrointestinal tract, imparts significant weight loss accompanied by improved glucose and lipid homeostasis that are hallmarks of RYGB.
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5 Members
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18 MeSH Terms
Early Increases in Bile Acids Post Roux-en-Y Gastric Bypass Are Driven by Insulin-Sensitizing, Secondary Bile Acids.
Albaugh VL, Flynn CR, Cai S, Xiao Y, Tamboli RA, Abumrad NN
(2015) J Clin Endocrinol Metab 100: E1225-33
MeSH Terms: Adolescent, Adult, Bile Acids and Salts, Blood Glucose, Body Mass Index, Fasting, Female, Follow-Up Studies, Gastric Bypass, Humans, Insulin, Insulin Resistance, Male, Middle Aged, Obesity, Morbid, Treatment Outcome, Weight Loss, Young Adult
Show Abstract · Added August 26, 2015
CONTEXT - Roux-en-Y gastric bypass (RYGB) is the most effective treatment for morbid obesity and resolution of diabetes. Over the last decade, it has become well accepted that this resolution of diabetes occurs before significant weight loss; however, the mechanisms behind this effect remain unknown and could represent novel therapeutic targets for obesity and diabetes. Bile acids have been identified as putative mediators of these weight loss-independent effects.
OBJECTIVE - To identify the longitudinal changes in bile acids after RYGB, which may provide mechanistic insight into the weight loss-independent effects of RYGB.
DESIGN - Observational study before/after intervention.
SETTING - Academic medical center.
PATIENTS/PARTICIPANTS - Samples were collected from morbidly obese patients (n = 21) before and after RYGB.
INTERVENTION - RYGB.
MAIN OUTCOME MEASURES - Seventeen individual bile acid species were measured preoperatively and at 1, 6, 12, and 24 months postoperatively. Anthropometric, hormonal, and hyperinsulinemic-euglycemic clamp data were also examined to identify physiological parameters associated with bile acid changes.
RESULTS - Fasting total plasma bile acids increased after RYGB; however, increases were bimodal and were observed only at 1 (P < .05) and 24 months (P < .01). One-month increases were secondary to surges in ursodeoxycholic acid and its glycine and taurine conjugates, bacterially derived bile acids with putative insulin-sensitizing effects. Increases at 24 months were due to gradual rises in primary unconjugated bile acids as well as deoxycholic acid and its glycine conjugate. Plasma bile acid changes were not significantly associated with any anthropometric or hormonal measures, although hepatic insulin sensitivity was significantly improved at 1 month.
CONCLUSIONS - Overall findings suggest that bacterially derived bile acids may mediate the early improvements at 1 month after RYGB. Future studies should examine the changes in specific bile acid chemical species after bariatric procedures and bile acid-specific signaling changes.
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4 Members
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18 MeSH Terms
Novel mechanistic insights into ectodomain shedding of EGFR Ligands Amphiregulin and TGF-α: impact on gastrointestinal cancers driven by secondary bile acids.
Nagathihalli NS, Beesetty Y, Lee W, Washington MK, Chen X, Lockhart AC, Merchant NB
(2014) Cancer Res 74: 2062-72
MeSH Terms: ADAM Proteins, ADAM17 Protein, Amphiregulin, Bile Acids and Salts, Cyclin D1, Deoxycholic Acid, EGF Family of Proteins, ErbB Receptors, Gastrointestinal Neoplasms, Glycoproteins, HCT116 Cells, Humans, Intercellular Signaling Peptides and Proteins, Pancreas, Phosphorylation, Receptors, G-Protein-Coupled, STAT3 Transcription Factor, Transforming Growth Factor alpha, src-Family Kinases
Show Abstract · Added February 14, 2014
Secondary bile acids (BA) such as deoxycholic acid (DCA) promote the development of several gastrointestinal malignancies, but how they mediate this effect is unclear. In this study, we offer evidence of a mechanism involving ectodomain shedding of the EGFR ligands amphiregulin (AREG) and TGF-α, which rely upon the cell surface protease TACE/ADAM-17. Specifically, we show that AREG participates in DCA-induced EGFR and STAT3 signaling, cell-cycle progression, and tumorigenicity in human colorectal cancer and pancreatic ductal adenocarcinoma (PDAC). TACE and AREG, but not TGF-α, were overexpressed in both colorectal cancer and PDAC tissues compared with normal tissues. Exposure of colorectal cancer and PDAC cells to DCA resulted in colocalization of Src and TACE to the cell membrane, resulting in AREG-dependent activation of EGFR, mitogen-activated protein kinase (MAPK), and STAT3 signaling. Src or TACE inhibition was sufficient to attenuate DCA-induced AREG, but not TGF-α shedding. We also examined a role for the BA transporter TGR5 in DCA-mediated EGFR and STAT3 signaling. RNA interference-mediated silencing of TGR5 or AREG inhibited DCA-induced EGFR, MAPK, and STAT3 signaling, blunted cyclin D1 expression and cell-cycle progression, and attenuated DCA-induced colorectal cancer or PDAC tumorigenicity. Together, our findings define an AREG-dependent signaling pathway that mediates the oncogenic effects of secondary BAs in gastrointestinal cancers, the targeting of which may enhance therapeutic responses in their treatment.
©2014 AACR.
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19 MeSH Terms