Die Zebrafische als transgenes Tiermodell für die Visualisierung und Untersuchung des Blutzuckermetabolismus in-vivo
Final Report Abstract
Obesity and the closely associated Type 2 Diabetes Mellitus (T2DM) have reached epidemic proportions, and better drugs to treat these metabolic diseases are urgently needed. During my time as a DFG postdoctoral fellow, I (co-)pioneered the use of the zebrafish model to study glucose metabolism. The focus of this effort is the regulation of gluconeogenesis, a central biosynthetic pathway in the liver that provides glucose to peripheral organs during times of low energy supply. Elevated hepatic gluconeogenesis has a well-documented and major contribution to chronic hyperglycemia in diabetic patients. I set out to systemically identify novel modulators of glucose metabolism through highthroughput screening for small molecules that regulate gluconeogenesis. Specifically, I generated and applied transgenic pck1 reporter zebrafish, that monitor activity of this gluconeogenic key enzyme, to perform a high-throughput, whole organism screen for drugs that modulate gluconeogenesis. I tested 1280 compounds and identified 159 drugs that either up- or down-regulate the pck1 promoter by more than 1-fold log2 difference. This unbiased screen revealed a high level of functional conservation of drugs that modulate glucose homeostasis in zebrafish and humans, as it identified beta-adrenergic agonists, glucocorticoids, and various antipsychotic drugs amongst others. In addition, I identified many novel compounds for which the mechanisms of action on gluconeogenesis are completely unknown or poorly defined. In secondary assays, I linked the effect of these ”hit compounds” on pck1 promoter activity to levels of free glucose. I identified two compounds, PK11195 and GW405833 that strongly increase pck1 promoter activity, but surprisingly lower glucose levels. This phenotype is in contrast to most identified ”hit compounds” that activate the pck1 promoter and also induce higher levels of free glucose consistent with enhanced gluconeogenesis. One possible explanation for this ”high pck1, low glucose” trait is that gluconeogenesis is activated in response to a systemic fasting condition induced by these compounds. Drugs that increase energy expenditure are thought to be a promising avenue for the treatment of diabetes and obesity, but are difficult to discover in traditional in vitro drug screening approaches due to the complex regulation of energy metabolism. I continue my postdoctoral training in Dr. Stainier’s lab to analyze the mechanisms of action of these two compounds, PK11195 and GW405833, with the goal of developing new therapeutic strategies for diabetes. To this end, I will perform molecular and physiological analyses of energy metabolism using wildtype as well as zebrafish models of diabetes developed in our laboratory. I will also analyze the effect of these compounds in mammalian cells in culture, as well as in established mouse models of diabetes. In summary, this study will identify new regulators of gluconeogenesis, deepen our understanding of this central biosynthetic pathway, establish the zebrafish as a new tool for pharmacological and genetic research of energy metabolism, and potentially lead to the development of new drugs to treat obesity and type 2 diabetes. This approach is innovative and shows strong potential to complement traditional large-scale in vitro screens in the search for new treatments for metabolic diseases.
Publications
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(2011). ”Dynamic glucoregulation and mammalian-like responses to metabolic and developmental disruption in zebrafish.” General and Comparative Endocrinology 170: 334-45
Jurczyk, A., Roy, N., Bajwa, R., Gut, P., Lipson, K., Yang, C., Covassin, L, Racki, W.J., Rossini, A.A., Phillips, N., Stainier, D.Y.R., Greiner, D.L., Brehn, M.A., Bortell, R and DiIorio, P.
