Obesity and its comorbidities are currently considered an epidemic, and the involved pathophysiology is well studied. Hypercaloric diets are tightly related to the obesity etiology and also cause alterations in gut microbiota functionality. Diet and antibiotics are known to play crucial roles in changes in the microbiota ecosystem and the disruption of its balance; therefore, the manipulation of gut microbiota may represent an accurate strategy to understand its relationship with obesity caused by diet. Fecal microbiota transplantation, during which fecal microbiota from a healthy donor is transplanted to an obese subject, has aroused interest as an effective approach for the treatment of obesity. To determine its success, a multiomics approach was used that combined metagenomics and metaproteomics to study microbiota composition and function. To do this, a study was performed in rats that evaluated the effect of a hypercaloric diet on the gut microbiota, and this was combined with antibiotic treatment to deplete the microbiota before fecal microbiota transplantation to verify its effects on gut microbiota-host homeostasis. Our results showed that a high-fat diet induces changes in microbiota biodiversity and alters its function in the host. Moreover, we found that antibiotics depleted the microbiota enough to reduce its bacterial content. Finally, we assessed the use of fecal microbiota transplantation as a complementary obesity therapy, and we found that it reversed the effects of antibiotics and reestablished the microbiota balance, which restored normal functioning and alleviated microbiota disruption. This new approach could be implemented to support the dietary and healthy habits recommended as a first option to maintain the homeostasis of the microbiota.

Over the last few years, the application of high-throughput meta-omics methods has provided great progress in improving the knowledge of the gut ecosystem and linking its biodiversity to host health conditions, offering complementary support to classical microbiology. Gut microbiota plays a crucial role in relevant diseases such as obesity or cardiovascular disease (CVD), and its regulation is closely influenced by several factors, such as dietary composition. In fact, polyphenol-rich diets are the most palatable treatment to prevent hypertension associated with CVD, although the polyphenol-microbiota interactions have not been completely elucidated. For this reason, the aim of this study was to evaluate microbiota effect in obese rats supplemented by hesperidin, after being fed with cafeteria or standard diet, using a multi meta-omics approaches combining strategy of metagenomics and metaproteomics analysis. We reported that cafeteria diet induces obesity, resulting in changes in the microbiota composition, which are related to functional alterations at proteome level. In addition, hesperidin supplementation alters microbiota diversity and also proteins involved in important metabolic pathways. Overall, going deeper into strategies to integrate omics sciences is necessary to understand the complex relationships between the host, gut microbiota, and diet.

2 18 Abstract 19 Obesity and its comorbidities are currently considered an epidemic, and the involved 20 pathophysiology is well studied. Recently, the gut microbiota has emerged as a new potential 21 therapeutic target for the treatment of obesity. Diet and antibiotics are known to play crucial 22 roles in changes in the microbiota ecosystem and the disruption of its balance; therefore, the 23 manipulation of gut microbiota may represent a strategy for obesity treatment. Fecal microbiota 24 transplantation, during which fecal microbiota from a healthy donor is transplanted to an obese 25 subject, has aroused interest as an effective approach for the treatment of obesity. To determine 26 its success, a multiomics approach was used that combined metagenomics and metaproteomics 27 to study microbiota composition and function.28 To do this, a study was performed in rats that evaluated the effect of a hypercaloric diet on the 29 gut microbiota, and this was combined with antibiotic treatment to deplete the microbiota before 30 fecal microbiota transplantation to verify its effects on gut microbiota-host homeostasis. Our 31 results showed that a high-fat diet induces changes in microbiota biodiversity and alters its 32 function in the host. Moreover, we found that antibiotics depleted the microbiota enough to 33 reduce its bacterial content. Finally, we assessed the use of fecal microbiota transplantation as 34 an obesity therapy, and we found that it reversed the effects of antibiotics and reestablished the 35 microbiota balance, which restored normal functioning and alleviated microbiota disruption.38 Obesity is defined as a disequilibrium in energy balance and is currently a global health problem 39 in Western societies, where its prevalence has increased considerably in recent years. Obesity 40 triggers a vast number of comorbidities associated with hypertension, cardiovascular disease, 41 and diabetes, as well as other conditions [1]. It is widely known that obesity is affected by 42 numerous factors, such as diet, lifestyle and genetic background [2], and recently it has been 43 shown to be related to gut microbiota [3], which have been implicated in energy homeostasis 44 and metabolic functions [4]. Moreover, the same factors that affect obesity can modulate gut 45 microbiota composition, and the function of the gut microbiota will be affected by factors 46 involved in gut microbiota-host equilibrium [5].47 Several diet-induced animal models of obesity can be used to explore the mechanisms involved 48 in obesity. There are different obesogenic diets that can be employed. One example of these 49 diets is the semi-purified high-fat diet [6,7]. These types of diets are more commonly used in 50 these models due to their well-defined nutritional composition [8][9][10].51 Alterations in the gut microbiota composition have been shown to result in an imbalance that 52 leads to dysbiosis, which likely will have dramatic effects on the maintenance of health [11].53 Fecal microbiota transplantation (FMT) is a new and stra...