Obesity and the metabolic complications associated with it are increasing globally. Sedentary lifestyles, poor diet and genetic predisposition contribute to obesity. In addition, environmental chemicals such as Bisphenol A (BPA) may play a significant role. Exposure to BPA has been correlated with an array of adverse health effects on the endocrine system and whole-body homeostasis. This has resulted in manufacturers replacing it with structural analogues such as Tetra Methyl Bisphenol F (TMBPF), Bisphenol F (BPF), Bisphenol AP (BPAP), and fluorine-9-bisphenol (BHPF). BPA is a suspected obesogen as it can induce adipogenesis in human and murine preadipocytes. The effects of the BPA analogues listed above on adipogenesis have yet to be evaluated. The aim of this project is to investigate their adipogenic effects. For this purpose, we used 3T3-L1 mouse embryonic fibroblasts. This cell model can be differentiated into mature adipocytes with appropriate inducers including 3-isobutyl-1-methylxanthine (IBMX), insulin and dexamethasone, a synthetic steroid. To assess the effects of BPA analogues, the cells were treated with varying concentrations of TMBPF, BPF, BHPF, BPA, or BPAP in place of dexamethasone. The expression levels of mature adipocyte markers were assessed at mRNA and protein levels to determine the adipogenic potential of the analogues. Lipid accumulation was evaluated by Nile Red staining. A time course was performed to assess the expression levels of known transcriptional regulators of adipogenesis. The results indicate that TMBPF, BPF and BPA increase 3T3-L1 adipogenesis. BHPF and BPAP did not affect adipogenesis in this model. BPF appears to be at least as good as BPA at inducing adipogenesis. TMBPF, on the other hand, can induce adipogenesis to a greater extent than the other chemicals, including BPA, as evidenced by increased expression of adipogenic markers and lipid accumulation. Finally, key transcription factors C/ebpδ and C/ebpα, part of the adipogenic transcriptional cascade, were up-regulated at III two and six hours post-treatment by TMBPF. BPA also up-regulated C/ebpδ at two hours post-treatment. Though the adipogenic effects have become apparent for some of these analogues, the mechanism by which they elicit their effects remains to be discovered. More research is required to deduce the mechanism of action and to provide consensus on what the effects of these replacement bisphenols actually are.

Impaired function of the human intestinal epithelial barrier (IEB) might allow for permeability of harmful substances, such as obesogens, which induce obesity and further implications. Tight junction (TJ) proteins are the key component for normal functions of the barrier. In this master thesis, the correlation between increased TJ permeability of the IEB and absorption of obesogens was studied. The effect of obesogens on TJ expression was also investigated. Permeability tests performed on Caco-2 cell monolayers exposed to obesogens showed altered permeability, indicating that obesogens might have an effect on TJ protein expression. Furthermore, impaired monolayers showed increased permeability, which implies that impaired functions of IEB lead to increased absorption of obesogens.

The prevalence of obesity has already epidemic dimensions. Recently, the obesogens have been identified as the main cause in addition to excessive food intake, the lack of physical activity and the genetic background. These substances damage the metabolic processes, interfere with the hormonal functions and impair the energy balance in behalf of gaining weight and obesity. The theoretical part of this work deals with obesity, adipose tissue, lipid droplet and obesogens. From the obesogens there is closely specified a group of persistent organic pollutants (POP) from which one representative was used in the practical part of this work. The aim of the practical part was to describe the cellular model of differentiation the mesenchymal stem cell into adipocytes and to investigate the effect of one of the most frequently occurring obesogen on the expression genes of lipid metabolism and insulin signalling pathway. The morphological changes were observed in cells during differentiation (at days 0, 4, 10 and 21). The mesenchymal cells of the elongated spindle shape changed into adipocytes filled with lipid droplets. Oil Red O staining was used for quantification of accumulated lipids. The differentiation to adipocytes was confirmed by fluorescence immunocytochemistry using a specific protein FABP4. The...