The Gut Microbiome Profile in Obesity: A Systematic Review

Hindawi International Journal of Endocrinology Volume 2018, Article ID 4095789, 9 pages https://doi.org/10.1155/2018/4095789 Review Article The Gut Microbiome Profile in Obesity: A Systematic Review Olga Castaner ,1,2 Albert Goday,2,3,4 Yong-Moon Park,5 Seung-Hwan Lee ,6 Faidon Magkos,7 Sue-Anne Toh Ee Shiow,8,9,10 and Helmut Schröder 1,11 1 Cardiovascular Risk and Nutrition Research Group, Hospital del Mar Research Institute (IMIM), Barcelona, Spain CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Santiago de Compostela, Spain 3 Department of Endocrinology and Nutrition, Hospital del Mar Research Institute, Barcelona, Spain 4 Department of Medicine, University Autònoma de Barcelona and Universitat Pompeu Fabra, Barcelona, Spain 5 Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA 6 Division of Endocrinology & Metabolism, Department of Internal Medicine, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea 7 Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore (NUS) and Clinical Nutrition Research Centre (CNRC), Singapore Institute for Clinical Sciences (SICS), Agency for Science, Technology and Research (A∗STAR), Singapore 8 Yong Loo Lin School of Medicine, National University of Singapore, Singapore 9 Division of Endocrinology, Department of Medicine, National University Health System, Singapore 10 Regional Health System Planning and Development, Singapore 11 CIBER de Epidemiologia y Salud Pública (CIBERESP), Madrid, Spain 2 Correspondence should be addressed to Olga Castaner; and Helmut Schröder; Received 27 October 2017; Accepted 3 January 2018; Published 22 March 2018 Academic Editor: Małgorzata Kotula-Balak Copyright © 2018 Olga Castaner et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Gut microbiome has been identified in the past decade as an important factor involved in obesity, but the magnitude of its contribution to obesity and its related comorbidities is still uncertain. Among the vast quantity of factors attributed to obesity, environmental, dietary, lifestyle, genetic, and others, the microbiome has aroused curiosity, and the scientific community has published many original articles. Most of the studies related to microbiome and obesity have been reported based on the associations between microbiota and obesity, and the in-depth study of the mechanisms related has been studied mainly in rodents and exceptionally in humans. Due to the quantity and diverse information published, the need of reviews is mandatory to recapitulate the relevant achievements. In this systematic review, we provide an overview of the current evidence on the association between intestinal microbiota and obesity. Additionally, we analyze the effects of an extreme weight loss intervention such as bariatric surgery on gut microbiota. The review is divided into 2 sections: first, the association of obesity and related metabolic disorders with different gut microbiome profiles, including metagenomics studies, and second, changes on gut microbiome after an extreme weight loss intervention such as bariatric surgery. 1. Introduction Obesity is known to be a major public health problem that affects more than 1.9 billion adults, which means 39% of adults are considered obesity and overweight [1]. Estimations from the noncommunicable diseases (NCD) collaboration reported that if these trends continue, by 2025, global obesity prevalence will reach 18% in men and surpass 21% in women; severe obesity will surpass 6% in men and 9% in women [2]. Obesity is associated with multiple pathologies, among them cardiovascular diseases, metabolic syndrome, and cancer [3]. The latest public statements report the attributable deaths to obesity. The Global BMI Mortality Collaboration reported 2 that mortality increased with body mass index (BMI) approximately in a log-linear manner and that the associations of both overweight and obesity with higher all-cause mortality were broadly consistent in four continents [4]. Another troubling factor is the increase of childhood obesity, which is known to be a risk factor for obesity in adults [5]. Gut microbiota has captured our attention in the last decade as an element that directly affects our health or disease status. In particular, it has been implicated in the aetiology of obesity [6]. In fact, the composition of gut microbiota seems to play a role concerning obesity. Gut microbiota is considered as an assortment of microorganisms that inhabit the gastrointestinal tract. The composition of this microbial community depends on the host, but it can also be modified by exogenous and endogenous events [7]. With regard to the host, these bacteria are symbiotic, and play an important role in physiological processes, for example, in digestion, or they can intervene in the metabolism, as they can increase energy production from the diet and take part in the regulation of the fatty acid tissue composition [8]. The different bacteria can also induce low-grade inflammation. All these processes are involved in obesity and metabolic disorders. With the introduction of human whole metagenome studies, the associations of microbiota and disease were plausible and many have been encountered. It is known that most of the human’s populations microbiota is composed by 5 phyla Bacteroidetes, Firmicutes, Actinobacteria, Proteobacteria, and Verrucomicrobia [9] being Bacteroidetes and Firmicutes around 90% of the total bacterial species [9, 10]. The composition of the bacterial diversity seems to change between lean and obese, increasing the number of Firmicutes to the detriment of Bacteroidetes [9, 11–13] in obese patients and also in type 2 diabetes, which is pathology in close relationship to obesity. But some recent studies have found controversial results [9, 11–15]: studies of association between microbiota profiles and different phenotypes or body mass index have adventured the positive and negative associations among the different phyla that populate the intestines. The searches of mechanistic pathways involved in the contribution of microbiota to obesity or vice versa have been subject for many animal studies [10]. An interesting finding was that obesity-resistant germ-free mice become obese and increase their energy harvest and caloric uptake after receiving a microbiota transplant [16]. The new era of sequencers has widely unlocked the acquirement of information. Sequencing of specific regions of 16S or 18S ribosomal genes allows the identification of organisms and their relative abundance in purified DNA [17]. Thus, the sequencing of gut microbiota with 16S rRNA made an inflexion point in the knowledge and relationship of (...truncated)