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Environmental chemicals as obesogens

Periodic Reporting for period 2 - OBESOGENS (Environmental chemicals as obesogens)

Période du rapport: 2018-07-01 au 2019-06-30

Obesity is a multifactorial disorder that has reached epidemic proportions. The recent dramatic rise in obesity rates is an alarming global health trend that consumes an increasing portion of health care budgets in the EU. The recent research implicates our environment as a major contributing factor. In this project, we focused on di-2-(ethylhexyl) phthalate (DEHP) that is a ubiquitous chemical used as plasticizer e.g. in polyvinyl chloride (PVC) products. Phthalates can disrupt endocrine systems and more recently, epidemiological and experimental studies associate phthalates with the high body weight in humans. To fully understand the mechanisms and to address the multifaceted nature of chemical induced metabolic disruption, the study focused on several key regulators involved in metabolism: the host gut and associated gut microbiome. To study these complex mechanisms, we used a zebrafish (ZF) as a model organism which is a novel powerful tool in translational biomedical research.
We successfully investigated the effect of DEHP on wide array of physiological functions including metabolism, gut integrity and homeostasis and immune function. Using the latest bioinformatics approaches, such as sub-network enrichment analysis, we were able to identify the adverse effects on cell processes and identify the expression targets responsible for the observed effects in detail. Among the genes, the signaling cascade dealing with the PPAR genes were altered, which is a very specific group of genes that may play an important role in lipid processes that lead to alterations in gut energy homeostasis, a possible link to DEHP-induced obesity. In addition, we identified novel molecular targets that show the link between dysregulated intestinal immune system and host microbiome in the adverse effects. More specifically, we bring the evidence, that metabolic disruptors can act via the effect on an adaptive part of the immune system, such as Th cells. Phthalates can thus contribute to diseases and dysfunctions that are based on dysregulated immune system such as Crohn's disease and ulcerative colitis.
To determine the alteration of microbiome with DEHP, we analyzed the composition and diversity of microbiome using NextGen sequencing. We also applied several novel bioinformatics approaches to predict metagenome functional content from marker gene (e.g. 16S rRNA) and thus predict the functional changes in the microbiome. In addition, we identified the microbial bioactive metabolites that are modulated by DEHP and have an adverse effect on host (e.g. dysregulation of adaptive part of the immune system). Further, the project helped the uncover the potency of ZF embryonic model to identify metabolic disruptors and suggested several sensitive endpoints dealing with metabolism and mitochondrial performance.
The project is actively discussing the results with scientific community via publications and with public via series of presentations and lectures. The project has both major scientific and public health significance. Scientifically, our knowledge of the molecular targets of phthalates is still limited, and this project was poised to uncover these mechanisms which could lead to the development of novel therapeutic interventions. Technologically, this research will establish zebrafish model as a tool to address mechanistic questions related to metabolic disruption and to study emerging chemicals of concern. From the public health perspective, diseases like obesity and metabolic disruption are a major cause of disability and a lesser quality of life.
Our research team had to optimize the exposure conditions such as the physico-chemical parameters of water and tested substance.
Initially, the fish (both sexes) were long term exposed to low dose of DEHP to mimic chronic exposure. To fully understand the mechanisms and to address the multifaceted nature of chemical induced metabolic disruption, we analyzed brain, the host gut and microbiome (fecal samples) in detail. Gut was analyzed using genome wide transcriptomic technique that helped us to determine the group of genes, cell processes or signaling pathways that were significantly modulated by model compound and thus to predict the mode of action and consequently the adverse health outcomes. The effect on the gut was evaluated together with the effect on the composition and diversity of the microbiome using latest bioinformatics approaches that helped us to understand the role on microbial bioactive metabolites in observed adverse effect. In addition, we investigated the suitability of zebrafish embryonic model to study metabolic disruptors. We applied several novel approaches that focus on metabolism and mitochondrial performance.
Taken together, we newly applied several advanced multi omics approaches that helped us to understand how these chemicals dysregulate the network of processes emphasizing the microbiome-gut axis as a main target. A detailed investigation found a zebrafish embryonic model as suitable model to study disruption of metabolism. The detailed view in phthalates’s mode of action represents a new piece of information for risk assessment and evaluation of potential health hazard.
Our results took considerable attention on conferences and discussions. We introduced our results and our topics to not only scientific community but also to a public audience, students and private sector.
Our experimental approach is a substantial departure from the status quo. Apart of other in vitro studies, more relevant in vivo multidisciplinary approach was considered allowing examination of multiple systems to better understand the interaction between brain, gut and microbiome in this complex disease. How the microbiome is altered by toxicants in the gut is not known for environmental contaminants. The results contribute not only to hazard assessment of phthalates but identify the mechanisms by which this occurs. Once identified, there is a high potential for these mechanistic studies to identify novel therapeutic targets for metabolic disruption and obesity.
From the public health perspective, diseases like obesity and metabolic disruption are a major cause of disability and a lesser quality of life. The expected outcome will bring what the researchers believe is a strong collaboration focused on a high priority topic (i.e. obesity/metabolic disruption) that is expected to gain public attention over the next decade. This research may generate biomarkers and methodology for earlier diagnostic tests of obesogens to prioritize chemicals for further investigation. We believe that this project will benefit the community of complex diseases by providing valuable insight into the underlying disease mechanisms, which can be directly translated into new therapies. Technologically, we established zebrafish model as a tool to address mechanistic questions related to obesity and to study emerging obesogens of concern. The fellow's new expertise (i.e. metagenomics, trancriptomics and bioinformatics), obtained during this project, will certainly benefit the European Research Area. New high throughput models for obesity research such as the zebrafish embryonic model have high potential to identify new obesogens (e.g. new generation of plastic additives), which is highly attractive to societies that facilitates contact with science-policy interface and can bring new information to policy makers.
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