Review
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 21, 2016; 22(39): 8698-8719
Published online Oct 21, 2016. doi: 10.3748/wjg.v22.i39.8698
Improved glucose metabolism following bariatric surgery is associated with increased circulating bile acid concentrations and remodeling of the gut microbiome
Lukasz Kaska, Tomasz Sledzinski, Agnieszka Chomiczewska, Agnieszka Dettlaff-Pokora, Julian Swierczynski
Lukasz Kaska, General, Endocrine and Transplant Surgery, Medical University of Gdańsk, 80-214 Gdańsk, Poland
Tomasz Sledzinski, Agnieszka Chomiczewska, Department of Pharmaceutical Biochemistry, Medical University of Gdańsk, 80-211 Gdańsk, Poland
Agnieszka Dettlaff-Pokora, Julian Swierczynski, Department of Biochemistry, Medical University of Gdańsk, 80-211 Gdańsk, Poland
Julian Swierczynski, State School of Higher Vocational Education in Koszalin, 75-582 Koszalin, Poland
Author contributions: Kaska L, Sledzinski T and Chomiczewska A contributed to the background research, the formulation of the manuscript, and the revision of the manuscript; Dettlaff-Pokora A contributed to background research, formulation of the manuscript, and management of the images; Swierczynski J contributed to background research, formulation of the manuscript, revision of the manuscript, and final approval of the manuscript.
Supported by the Medical University of Gdańsk, No. ST-41 and No. ST-40; the Ministry of Science and Higher Education of the Republic of Poland under the Leading National Research Centre (KNOW) program, No. 2012-2017.
Conflict-of-interest statement: The authors declare no conflict of interest.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Julian Swierczynski, Professor, Department of Biochemistry, Medical University of Gdańsk, ul. Dębinki 1, 80-211 Gdańsk, Poland. juls@gumed.edu.pl
Telephone: +48-58-34914 62 Fax: +48-58-34914 65
Received: July 12, 2016
Peer-review started: July 14, 2016
First decision: August 8, 2016
Revised: August 23, 2016
Accepted: September 14, 2016
Article in press: September 14, 2016
Published online: October 21, 2016
Abstract

Clinical studies have indicated that circulating bile acid (BA) concentrations increase following bariatric surgery, especially following malabsorptive procedures such as Roux-en-Y gastric bypasses (RYGB). Moreover, total circulating BA concentrations in patients following RYGB are positively correlated with serum glucagon-like peptide-1 concentrations and inversely correlated with postprandial glucose concentrations. Overall, these data suggest that the increased circulating BA concentrations following bariatric surgery - independently of calorie restriction and body-weight loss - could contribute, at least in part, to improvements in insulin sensitivity, incretin hormone secretion, and postprandial glycemia, leading to the remission of type-2 diabetes (T2DM). In humans, the primary and secondary BA pool size is dependent on the rate of biosynthesis and the enterohepatic circulation of BAs, as well as on the gut microbiota, which play a crucial role in BA biotransformation. Moreover, BAs and gut microbiota are closely integrated and affect each other. Thus, the alterations in bile flow that result from anatomical changes caused by bariatric surgery and changes in gut microbiome may influence circulating BA concentrations and could subsequently contribute to T2DM remission following RYGB. Research data coming largely from animal and cell culture models suggest that BAs can contribute, via nuclear farnezoid X receptor (FXR) and membrane G-protein-receptor (TGR-5), to beneficial effects on glucose metabolism. It is therefore likely that FXR, TGR-5, and BAs play a similar role in glucose metabolism following bariatric surgery in humans. The objective of this review is to discuss in detail the results of published studies that show how bariatric surgery affects glucose metabolism and subsequently T2DM remission.

Keywords: Bariatric surgery, Type-2 diabetes, Bile acids, RXR, TGR-5, Gut microbiota, Roux-en-Y gastric bypasses

Core tip: Emerging evidence suggests that increased concentrations of circulating bile acids could, through their interaction with membrane (TGR-5) and nuclear (FXR) receptors, significantly contribute to improved glucose metabolism following bariatric surgery. This review presents information on the potential mechanism of bile acids on the remission of type-2 diabetes following bariatric surgery.