DNA mutations in metabolic syndrom and epigenetic regulation of repair enzymes

Metabolic syndrome and diabetes mellitus type 2 are associated with a systemic low-grade inflammation and enhanced oxidative stress which is caused by endogen produced reactive oxygen species (ROS). Both conditions fortify each other and are responsible for diverse symptoms of the metabolic syndrome such as insulin resistance. Oxidative stress is especially elevated in extended adipose tissue and under chronic exposure to free saturated fatty acids. Saturated fatty acids activate the nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) which leads to a higher ROS burden. Long chain poly-unsaturated fatty acids have the opposite effect. ROS causes DNA damages which are recovered by DNA repair mechanisms or prevented by endogen and exogen antioxidants. Epigenetic mechanisms regulate mRNA expression of a variety of genes including the ones involved in inflammatory processes, ROS production and quenching and DNA repair mechanisms. DNA methylation of several genes was found to be altered under oxidative stress or inflammatory conditions. The aim of the present project is to analyse alterations of epigenetic DNA methylation and mRNA expression of genes involved in DNA damage repair, oxidative stress and inflammatory processes caused by a high fat diet, which is typical for western countries, enriched with polyunsaturated fatty acids and with or without antioxidants. Furthermore, the influence of this diet on inflammatory pathways and on ROS formation will be investigated. An animal and a cell culture model were chosen for these investigations. Two groups of C57BL/6J mice are fed a high-fat and a normal diet with or without addition of vitamin E and C for up to three months. After the intervention, adipose and colon tissue will be stored for analyses. In a study on Caco-2 cell, they will be treated with palmitate, docosahexaenoic acid, hydrogen peroxide, folate, vitamin E and C and combinations of these reagents. Further, two NADPH family members will be knocked down. DNA methylation of distinct genes will be analysed in all collected samples by pyrosequencing and DNA methylation array. mRNA expression will be assessed using a microarray and quantitative PCR. Microsatellite instability, DNA strand breaks and the total antioxidative capacity will also be investigated. Findings of this study will help to understand patho-epigenetic processes in obesity associated oxidative stress and inflammation. This knowledge may improve the therapy of metabolic syndrome and diabestes mellitus type 2 (DMT2) by influencing epigenetic, oxidative and inflammatory pathways by nutritional interventions.

The correlation between obesity and metabolic syndrome with significant increases of certain cancer rates is of public concern. The main objective of this project was therefore to assess the influence of diet on DNA methylation and expression of genes involved in DNA damage, repair and inflammation pathways.In a first step, a comprehensive literature research was performed. Results of this evaluation indicate altered glucose and fatty acid metabolism as a reason for DNA damage. Literature also showed that genomic damage can be reversed by dietary measures leading to reduction of body weight.Our in vitro experiments showed a dose dependent reduction of oxidative stress and an enhanced expression of DNMT1 and DNA repair gene MLH1. Vitamin E and EGCG, extracted from green tea, counteracted oxidative stress induced by H2O2. In vivo we detected a significant increase of DNA damage in liver and colon of mice fed with a high fat diet. Vitamin E, Gallic acid (GA), EGCG and soy-based equol reduced DNA damage, derived from obesity, modulated the expression of MLH1 and DNMT1 and improved obesity induced dysbalances of GI microbiota. Furthermore, obesity related parameters, which are associated with adverse health effects (tumor necrosis factor-?, haemoxygenase-1, monocyte chemoattractant protein-1 and Nf-? B) were reduced after GA feeding as well. In some cases the changes of gene expression could be linked to the methylation of CpGs in the promotor region of DNMT1 and MLH1. In conclusion, the evaluation of currently available literature showed that only a small number of studies have been published with concern excess body weight and genome stability. Our experiences indicate a significant impact of excessive overweight on DNA stability and DNA methylation. Supplementation with plant ingredients were found to reduce obesity linked inflammatory status, reduce DNA breaks and modulated the epigenetic control of crucial genes, presumably by individual characteristics of the compounds. These activities should be a science based starting point for concepts of an individual preventive health care.