Review Bariatric surgery and the gut-brain communicationdThe state of the art three years later Maria de Fa ´ tima Haueisen S. Diniz M.D., Ph.D. * , Vale ´ ria M. Azeredo Passos M.D., Ph.D., Marco Tu ´ lio C. Diniz M.D., Ph.D. Federal University of Minas Gerais, Department of Internal Medicine, Rua Ceara ´, Belo Horizonte, Minas Gerais, Brazil article info Article history: Received 30 September 2009 Accepted 23 November 2009 Keywords: Gut peptides Gut-brain axis Bariatric surgery obesity abstract Objective: This review analyzes the literature concerning gut peptides and bariatric surgery, from 2005 to July 2009. In particular, we are interested in whether, and how, gastrointestinal peptide alterations following surgery interfere with appetite/satiety, and what role they might play in the resolution of comorbidities. Research methods and procedure: PubMed/MEDLINE and ISI Web of Knowledge were used to search for human studies concerning gut peptides profiles after any bariatric operation technique. Results: Most of the studies reviewed had longitudinal design, short follow-up, and low statistical power. The diversity of study results may be partially explained by methodological aspects. Glucagon-like peptide-1, gastric inhibitory peptide, and peptide YY alterations may contribute to the excellent results in glycemic control of diabetics. Results do vary depending on bariatric operation technique; this is particularly evident in the case of ghrelin, which has been much studied in recent years. Ghrelin suppression has been linked to increased satiety, alterations in energy homeostasis, and better glucose metabolism. Conclusions: There is a lack of long-term data on gastrointestinal hormone profiles after bariatric surgery and the studies have many methodological pitfalls. We still need prospective, long-term, good methodological studies in this area. Ó 2010 Elsevier Inc. All rights reserved. Bariatric surgery has been considered the choice treatment for morbid obesity, and its long-term results, which were supe- rior to clinical treatment, had generated research interest in the mechanisms of such efficiency [1]. Three years ago, we reviewed the literature to look for possible implications of different bariatric operations on gastrointestinal peptides and their relationships with the neural paths involved in the central regulation of appetite and satiety. At that time, one could say that there was a lack of comparability between studies. The samples were too small, and statistical power was poor. The design approaches and study protocols were very different. Furthermore, laboratorial techniques could not be compared. As in all new research areas, human studies involving gastrointestinal peptides are limited by the number of participants and short follow-up in longitudinal studies. At the conclusion to that review, it was still not clear how gastrointes- tinal peptides changed after different bariatric techniques or whether abnormalities in the gut brain communication contributed to the bariatric surgery outcomes [2]. Currently, the main questions are still the following: what are the alterations of gastrointestinal peptides after bariatric surgeries? Could these alterations be related to weight loss and the resolution of comorbidities after the operations? Is appetite related to gastrointestinal peptide changes after surgery? Can we predict the long-term results of surgery by measuring changes in these peptides? Understanding the role of gastrointestinal peptide alterations after bariatric surgery may allow for a more comprehensive approach to obesity and its comorbidities. Therefore, this article aims to critically review the recent literature and search for human studies that examine the profile of gut peptides after any bariatric surgery technique. Methods PubMed/MEDLINE and ISI Web of Knowledge were used to search the English- and French-language literature from March 2005 to July 2009. Search terms included ‘‘gut peptides’’, ‘‘gastrointestinal peptides’’, ‘‘gut hormones’’, ‘‘bariatric surgery’’, ‘‘morbid obesity’’, and each peptide individually: ‘‘cholecys- tokinin’’, ‘‘glucagon-like peptide-1’’ (GLP-1), ‘‘gastric inhibitory polypeptide’’ * Corresponding author. Tel.: þ55 3132872250; fax: þ55 31 32412280. E-mail address: mfhsdiniz@yahoo.com.br (M. F. H. S. Diniz). 0899-9007/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.nut.2009.11.018 Contents lists available at ScienceDirect Nutrition journal homepage: www.nutritionjrnl.com Nutrition 26 (2010) 925–931