Doctor of Philosophy

dissertationThe incidence of complex metabolic disease has risen to an alarming level in the last several decades. This elevated frequency has been accompanied by increased social and financial costs, with nearly $250 billion spent each year on diabetes alone. Despite this growing health crisis, only a small percentage of the heritable risk for these disorders has been identified. Possible sources of this missing heritability include geneenvironment interactions and gene-gene interactions, as well as the influence of parental or grandparental metabolism. In this work, I have focused on characterizing potential sources of these effects and the impacts they may have on physiology. The deacetylase Sir2 is a conserved metabolic regulator whose influence in normal and pathological physiology has been well documented but little understood. In characterizing Drosophila sir2 mutants, I discovered that loss of sir2 leads to progressive defects in carbohydrate and lipid homeostasis as well as the development of insulin resistance and glucose intolerance. I found that these functions of Sir2 are localized to the fat body and partially restore metabolic function by overexpressing the nuclear receptor dHNF4. Finally, I found that dHNF4 acetylation and stability is altered in sir2 mutants, suggesting that this factor is a key and direct target for Sir2 in the maintenance of metabolic flexibility. In the second part of this work, I focus on the development of both dietary and genetic paradigms to induce metabolic dysfunction in the parental generation that can iv lead to heritable physiological defects in their progeny. I found that either method of altering parental metabolic state can induce heritable changes in offspring metabolism under both basal and challenge conditions for at least two generations. I also identified key sources of genetic and environmental variation that influence the degree of parental dysfunction as well as the degree of physiological responses in the progeny. These studies lay the groundwork for more careful characterization of progeny responses, the molecular pathways affected in these progeny, as well as the mechanisms by which these changes are inherited

Charakterisierung der molekularen Wirkmechanismen der Langlebigkeitsgene Sir2 und foxo und der epigenetischen Anpassungen an eine Nahrungsrestriktion in Drosophila melanogaster

Ziel dieser Arbeit war es, den Einfluss der Überexpression von Sir2 und foxo im adulten Fettkörper auf Lebensspanne, Hungerresistenz, Fettspeicherung und Genexpressionsmuster von Drosophila zu untersuchen. Außerdem wurde das genomweite Bindungsmuster der Histonmodifikation H3K9ac nach einer Nahrungsrestriktion untersucht. Die Sir2-Überexpression verlängerte die Lebensspanne von Weibchen und Männchen und erhöhte außerdem die Hungerresistenz von Männchen. Außerdem induzierten Sir2 und foxo sehr ähnliche Genexpressionsmuster im adulten Fettkörper, weshalb postuliert wird, dass beide Gene über ähnliche Signalwege zur Lebensverlängerung führen. Die Nahrungsrestriktion führte zur genomweiten Hyperacetylierung an Histon H3K9 und schaffte weiterhin die epigenetische Grundlage für verstärkten Proteinabbau. Beides sind mögliche Mechanismen über die die Nahrungsrestriktion lebensverlängernd wirkt, da bekannt ist, dass die Histonacetylierung und auch die Proteasomaktivität mit dem Alter abnimmt