Obesity and gut microbiota
Obesity is a major concern in modern societies, especially in developed countries, since it’s prevalence has tripled worldwide since 1975 . The World Health Organization reports that 39% of adults aged 18 years and over were overweight in 2016, and 13% were obese .
Obesity is usually defined as excess of body weight compared to height. However, this simplistic definition hides an etiologically complex multifactorial disease that can be related to other disorders like type 2 diabetes , cardiovascular diseases  and some cancers . While several methods are used to treat excessive weight gain, obesity continues to be a major public health problem, demanding novel nutritional and/or medical solutions.
The intestinal microbiota has emerged over the last decade as a possible new factor to play a key role in the development of obesity. Many studies have identified significant changes in bacterial diversity loss in overweight or obese people . Diversity loss is also closely linked with tissue inflammation and insulin resistance . Another mechanism of action by which the microbiota may play a role in the development of obesity is by the energy harvesting increase from the diet  and fat storage . Therefore, the gut microbiome is being increasingly considered as a crucial target for new and more effective obesity therapies.
Many studies have identified bacterial diversity loss in overweight or obese people, which positions the gut microbiome as a crucial target for novel obesity therapies
When closely looking to the microbial members of the human gut, different bacterial families and genera have been reported to have a positive or negative correlation with obesity. Some of the bacterial families that were consistently enriched in obese people were Enterobacteriaceae  and Prevotellaceae . On the contrary, members of the bacterial family Christensenellaceae were consistently more abundant in low Body Mass Index (BMI) subjects . Specific bacterial genera associated with a negative correlation between BMI and relative abundance were Roseburia , Alistepes , Erwinia, and Oscilospira .
However, the microbiome is not a closed and unaltered ecosystem. Over time it can fluctuate induced by different factors. Accumulating evidence has suggested that long-term diet is the primary driver of gut microbiota composition. The Western diet high in sugar, protein and fat, but low in fruit, grains and vegetables and urban environmental factors lead to loss of bacterial diversity. This loss translates into a decrease of the microbiome functionality and in a lower production of Short chain fatty acids (SCFA) .
Based on all the available evidence, a personalized designed dietary intervention may induce changes in composition and function of the gut microbiota. Studying these changes will allow a better understanding of the associations between personalized diet-induced improvement of metabolic status and gut microbiota.
PREVENTOMICS and gut microbiota
The PREVENTOMICS project aims to bring new knowledge to the field of gut microbiota and personalised dietary interventions. In order to achieve the main aim, the microbiome of volunteers from interventional nutrition studies will be monitored through next-gen amplicon sequencing of 16S rRNA gene. The results of our research will allow to define which genera play the most important role in inducing greater weight loss and favouring a healthier metabolic state after a personalized diet intervention. This information will be used in a final animal model study with the objective to demonstrate the microbiome’s functionality in the prevention and improvement of pathologies associated with obesity. A subset of faecal samples from the volunteers will be selected and transplanted to a murine animal model with an overweighted induction through a previous consumption of a western diet.
About the author
Radu Ghemis Malcic
PhD student in Microbiome Research at LEITAT Technological Center. His research is focused around the analysis of human microbiota through bioinformatics systems aiming to understand the relationship between changes in the microbiota and the occurrence of pathologies.
Private non-profit RTO with large experience in industrial innovation, transforming technological solutions and scientific results into economic and competitive. With broad expertise in animal experimentation, applied microbiology and metabolomics, LEITAT will use humanized microbiome mouse models to correlate biomarkers and health status, to define the benefits of nutrition on diet-related diseases.
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