New mechanisms that regulate the expression of genes implicated in the process of ketogenesis

Dissertação para obtenção do Grau de Mestre em Biotecnologia

Fatty acid oxidation and ketogenesis play an important role in metabolic adaptation of the liver. Ketogenesis is a crucial process, especially in fasting. It is the last step of lipid metabolism and provides energy in the form of ketone bodies for the extra hepatic tissues, saving glucose for vital tissues, as the brain. In this project there were studied mechanisms by which genes involved in ketogenesis are regulated. In the first part, the hypothesis was to test whether the FoxO family members, FoxO3a and FoxO1, were responsible for HMGCS2 induction by p53 activation. HMGCS2 is a key regulator of the ketone body production, and it was published by the laboratory where this project was developed that it is a FoxO3a/FoxO1 target. P53 was described to stimulate FAO in conditions of food restriction, and that this could be a part of its effect as a suppressor gene, related to the Warburg effect. During the development of this project, it was seen that FoxO3a and FoxO1 were not related to HMGCS2 induction, when there is p53 activation, induced by DNA damage with doxorubicin treatment. In the second part, Fsp27, from the CIDE family, was studied. Fsp27 is a lipid droplet associated protein. Its expression is regulated by HMGCS2 activity and this gene is expressed during early fasting. Fsp27 is able to down-regulate FAO when it’s overexpressed. The objective was to seek a regulatory role of Fsp27 in mouse liver. During the development of this project, it was confirmed that this protein had a nuclear localization and that its expression would affect PPAR signaling pathway. In AML12 cells, Fsp27 inhibited the activation of the HMGCS2 promoter by PPARα. The hypothesis was that Fsp27 would be sequestering PPARα’s endogenous ligands, since this inhibition would disappear when the cells were treated with the pharmacological agonist WY14643.