Metabolic syndrome, encompassing type 2 diabetes, non-alcoholic fatty-liver disease, and cardiovascular disease, affects more than one billion people worldwide. While its etiology is complex, the best biological marker of metabolic syndrome is increased levels of apolipoprotein B (ApoB)-containing lipoproteins (B-lps). B-lps transport triglycerides and cholesterol through the plasma to peripheral tissues, and excess plasma B-lps are causative to metabolic syndrome. A single ApoB molecule decorates each B-lp and is essential for its function. However, the cellular mechanisms that ultimately regulate ApoB and B-lp production, secretion, transport, and degradation remains to be fully defined. The proposed studies aim to identify new molecules that alter B-lp physiology with the hope of not only generating new therapeutics but to elucidate new cell biological mechanisms of ApoB regulation. Human B-lp biology is remarkably conserved in the zebrafish. Further, zebrafish produce large numbers of progeny, larvae are optically transparent, and larvae do not require an exogenous food source. Thus, the zebrafish is the ideal model to identify novel mechanisms of ApoB modulation. Therefore, the Farber lab generated an in vivo chemiluminescent reporter of ApoB that does not disrupt ApoB function. Thus, I hypothesize that I can identify novel drugs that modulate ApoB regulation, turnover, and function to rectify metabolic dysfunction using this whole-animal reporter of ApoB. I have developed a high-throughput assay to screen chemiluminescence from whole zebrafish. Each compound that reduces ApoB from a drug repurposing library will be further validated by several assays measuring ApoB and B-lps production, size, and turnover. I will also evaluate the effects of each compound on whole-animal physiology. My screening efforts have identified 25 ApoB-lowering compounds. One compound, pimethixene maleate, specifically reduces ApoB levels in a dose- dependent manner. Prior research suggests pimethixene is a serotonin receptor antagonist. Studies suggest that serotonin influence B-lps levels through regulation of the mammalian Target of Rapamycin (mTOR). Thus, I hypothesize that pimethixene-dependent ApoB reduction is mediated by 5-HT2 receptor antagonism. I will determine whether pimethixene directly alters this pathway. Further, I will examine whether this compound improves several risk factors associated with metabolic disease using a series of established transgenic reporter lines and bioinformatic approaches. Ultimately, this research aims not only to identify novel ApoB-modulating therapeutics that would improve outcomes of metabolic disease but would also provide fundamental insights into the regulation and function of ApoB. Together, the research environment of the Farber lab and the Carnegie Institute are ideal for the success of this project and my success in the future as I grow towards an independent career in metabolism research.
High plasma triglycerides and cholesterol levels, transported via lipoproteins, causes metabolic dysfunction, affecting more than one billion people globally; thus, there is a need to identify new mechanisms to modulate plasma lipid levels. Human lipid metabolism is remarkably conserved in the larval zebrafish, and this model represents the ideal system to identify new means of lipoprotein regulation. The proposed studies utilize a whole- animal model to expand our understanding of the regulation of lipoproteins and to improve the pharmaceutical options for the treatment of metabolic diseases.
