Systems biology approach to defining impact of a genetic variant of GPx4 and selenium intake

The micronutrient selenium (Se) is critically important for optimal health. The Se status of the UK population is only marginal and may increase risk not only of viral infections but also of a number of major diseases including prostate and colon cancer. However, the mechanisms by which Se intake affects gut health are poorly understood and the impact of interactions between Se intake and genetic factors not defined. In this project we will adopt a systems approach to describe the effects of Se on the intestinal epithelium and the impact of a specific genetic variant. The project will also provide a proof of principle of for such analysis of nutrient-gene interactions. The programme of work will combine mathematical modelling with in vitro molecular techniques, experiments in cell lines and work with transgenic mice to assess the functional effects of a key variant in the gene that codes for the selenoprotein glutathione peroxidase in response to Se intake. Measurements will be made of selenoproteins and related biochemical pathways and the experimental data will be used to refine a mathematical model of selenoprotein metabolism and its downstream effects. The systems model generated in this programme will allow prediction of the how Se supply modulates biochemical pathways and cell function. Validation of the model in a physiological context will lay the basis for future testing of the model in human studies. The major outcomes from this programme will identification of novel functional biomarkers of Se status for use in later human studies and an increased ability to model nutrient metabolism at different physiological levels in relation to genetic factors.

The aim of this project is to develop a systems approach that can yield robust understanding of the complex interactions between intake of the micronutrient selenium (Se) and genotype which influence health. This will be achieved by building a predictive model of the selenoprotein hierarchy and network of downstream pathways affected by Se intake and selenoprotein expression using data from in vitro RNA-protein binding, cell culture and animal experiments. A cell-specific mathematical model will be built to predict how, at the intracellular level in intestinal epithelial cells, genetic variants interact with altered dietary Se intake to influence biomarkers of selenoprotein function. To achieve this we will carry out a series of iterations in which mathematical models are refined by inclusion of experimental data from RNA-protein binding, cell culture and animal experiments. RNA-protein binding experiments will be carried out to describe quantitatively how the interactions between protein factors of the protein synthetic machinery and selenoprotein mRNAs determine the hierarchy of selenoprotein synthesis, and how these interactions are altered by genetic variants in 3'untranslated sequences with a particular focus a specific genetic variant in the glutathione peroxidise 4 (GPx4)gene. The selenoprotein hierarchy and downstream target pathways will be investigated in cell culture by modulating expression of a series of single selenoproteins (using knock-down technologies). Knock-in mice will be made by homologous recombination so that for GPx4 the homologous mouse gene is knocked out and replaced by either variant of the human gene corresponding to the SNPs of interest. Feeding experiments with these mice will investigate the impact of the SNPs, in conjunction with Se supply, on selenoprotein expression and downstream targets such as inflammatory and stress response pathways.

This research will impact on BBSRC strategy - both 'Fundamental (mechanistic) research on the biology of ageing and its modulation by diet, physical activity and developmental factors' and 'Systems approaches to biological research'. Major, immediate beneficiaries will be researchers either investigating health-related outcomes of selenium intake or designing studies of how inter-individual genetic variability influences outcomes of micronutrient intake. The research will help define nutrient requirements for optimal health in relation to genetic individuality. The project will develop new systems biology approaches for modelling the interaction of nutrient and genetic factors in affecting metabolic pathways and will provide proof-of-principle that a systems approach can yield robust understanding of the complex interactions between diet and genotype which influence health. The predictive model should identify potential systems biomarkers of Se status that can be tested in future human studies; since Se intake is sub-optimal in UK and other parts of Europe such biomarkers will be of considerable use in studies of Se intake in relation to health outcome. In a broader context the work will provide a prototype for modelling how a limiting resource or nutrient is allocated to various biological functions. The resources generated (including gene constructs, cell lines, mouse models and mathematical models) will be available beyond the life of this project for further studies that will feed into a research environment specialised in studies of nutrition, systems biology and ageing. The RCUK Brain Ageing and Vitality Centre, combined with specialist facilities for long-term mouse studies in ageing, will provide a focus for translating the findings from the programme into the design of future human studies and identification of outcome measures of nutrition/ageing. The resources will also be available for further studies through collaboration, with researchers elsewhere, with interests in nutrition, genotype and health including. In particular, this programme is expected to inform the identification of outcome measures which are likely to be modifiable by nutrition and which may influence the ageing trajectory. Other potential beneficiaries are bodies responsible for issuing guidelines to the public about optimum nutrition, such as the Food Standards Agency and the British Nutrition Foundation, and manufacturers of micronutrient-enriched foods. JCM and JEH have good engagement with Food Standards agency through workshops (JEH) and advisory committees (JCM). This will allow a base for further engagment in relation to data that emerge from this project. Our communication strategy will be to present the work at appropriate scientific conferences (Nutrition Society, Systems workshops) and to publish results in high-impact journals. Applicants will work closely with CISBAN (the BBSRC/EPSRC Centre for Integrated Systems Biology of Ageing and Nutrition) and this will facilitate communication of the project to the systems biology community . The research team is built on two successful collaborations: between John Hesketh (JEH) and John Mathers (JCM) in the area of nutrient-gene interactions, and between Tom Kirkwood (TBLK), Daryl Shanley (DPS) and JCM within CISBAN. JEH and DPS co-supervise a PhD student working with both laboratory and mathematical approaches. CISBAN provides a focus where mathematical biology can be developed within a nutritional context. DPS will provide the critical link with CISBAN, JEH will take responsibility for publication strategy JCM for engagement with government food and nutrition bodies and TBLK will take the lead in identifying activities relevant to public engagement of science. The outputs of the project will be discussed at the monthly meetings of all applicants and post-docs. At these meetings we will identify outputs with potential scientific impact and decide on communication and publishing strategy.