A common core microbiota between obese individuals and their lean relatives? Evaluation of the predisposition to obesity on the basis of the fecal microflora profile M. Elli a, * , O. Colombo b , A. Tagliabue b a AAT – Advanced Analytical Technologies Srl, Via Martiri della Resistenza-Galleria S. Giuseppe, 1, 29122 Piacenza, Italy b Centro Interdipartimentale di Studi e Ricerche sulla Nutrizione Umana e i Disturbi del Comportamento Alimentare, Università degli Studi di Pavia, Via A. Bassi 21, 27100 Pavia, Italy article info Article history: Received 12 March 2010 Accepted 18 March 2010 summary Obesity represents a crucial social problem in developed countries as a cause of multiple metabolic abnormalities. The exact etiology of this multifactorial disease is still unknown. The impact of dietary habits and lifestyle is currently under investigation but the role of other predisposing factors, such as genetic determinants and familial history, needs still to be elucidated. Significant alterations in the com- position of the intestinal microbiota have been recently identified in obese mice, suggesting an involve- ment of gut microbes in obesity. In humans, obese subjects are supposed to have a more efficient flora in energy extraction from food, due to the detection of quantitative differences in the major bacterial groups in obese subjects compared to lean ones. Despite these observations, the homologies in gut microbiota between obese adults and their lean relatives have never been investigated in details. Few reports about the detection of common microbial profiles between members of the same family have been published in the past but only one recent scientific article, investigating the presence of a common core microbiota between obese and lean twins, correlates genetic background and gut microflora as significant variables in obesity. The hypothesis suggested herein is that the identification of a familial-specific core microbiota could be precious in order to identify key-bacterial groups to be used as biomarkers for the evaluation of predis- position to obesity. Ó 2010 Elsevier Ltd. All rights reserved. Introduction The term ‘‘globesity” has recently been coined to describe the worldwide diffusion of obesity whose social impact on sanitary expenditure of Western countries is constantly increasing. The comprehension of the predisposing mechanisms has therefore ac- quired great relevance as source of opportunities for the early diag- nosis of obesity, especially for families with a history of obesity. The genetic determinants of human obesity are still currently un- der investigation, although several research groups identified 16 loci that reproducibly associate with common human overweight [1]. However, the impact of these discoveries in short term is not clear. A recent review [2] clearly defines the microbiota as an addi- tional ‘‘microbial” organ inside the human host whose manage- ment, via nutrition and use of food supplements, could lead to the reduction of the metabolic risk associated to dangerous life- styles. Obesity appears in fact as the result of a complicate mix of factors such as genetics, environment, diet and lifestyle, result- ing in an alteration of the equilibrium between energy expenditure and storage [3]. Gut microbiota, profoundly involved in the utilisation of in- gested nutrients, is thought to be more efficient in energy extrac- tion from nutrients in obese people than in lean ones [4] as indirectly demonstrated by the fact that the inoculation of germ- free mice with a conventional ‘‘obese” flora led to a significant weight gain [5,6] and that genetically obese ob/ob mice harboured a fecal microflora much more efficient in sugar fermentation and therefore promoting fat deposition [7]. The phylum of Firmicutes has been observed to be predominant in obese mice [7,8]. The composition of the microbial population of overweight peo- ple has been also investigated in recent years, by molecular meth- ods, retrieving contrasting results especially with reference to the Bacteroidetes that were found, by some authors, to increase in ob- ese people subjected to an hypocaloric diet [9] as well as, in other studies, to remain stable [10]. A decrease in Roseburia spp., Eubac- terium rectale and Bifidobacteria was also detected [10,11] follow- ing weight reduction. 0306-9877/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.mehy.2010.03.022 * Corresponding author. Tel.: +39 0523461483; fax: +39 0523451497. E-mail address: marina.elli@aat-taa.eu (M. Elli). Medical Hypotheses 75 (2010) 350–352 Contents lists available at ScienceDirect Medical Hypotheses journal homepage: www.elsevier.com/locate/mehy