The zebrafish is a useful vertebrate model to study lipid metabolism. Oil Red-O (ORO) staining of zebrafish embryos, though sufficient for visualizing the localization of triglycerides, was previously inadequate to quantify neutral lipid abundance. For metabolic studies, it is crucial to be able to quantify lipids during embryogenesis. Currently no cost effective, rapid and reliable method exists to quantify the deposition of neutral lipids and triglycerides. Thin layer chromatography (TLC), gas chromatography and mass spectrometry can be used to accurately measure lipid levels, but are time consuming and costly in their use. Hence, we developed a rapid and reliable method to quantify neutral lipids and triglycerides. Zebrafish embryos were exposed to Rimonabant (Rimo) or WIN 55,212-2 mesylate (WIN), compounds previously shown to modify lipid content during zebrafish embryogenesis. Following this, ORO stain was extracted out of both the zebrafish body and yolk sac and optical density was measured to give an indication of neutral lipid and triglyceride accumulation. Embryos treated with 0.3 microM WIN resulted in increased lipid accumulation, whereas 3 microM Rimo caused a decrease in lipid accumulation during embryogenesis. TLC was performed on zebrafish bodies to validate the developed method. In addition, BODIPY free fatty acids were injected into zebrafish embryos to confirm quantification of changes in lipid content in the embryo. Previously, ORO was limited to qualitative assessment; now ORO can be used as a quantitative tool to directly determine changes in the levels of neutral lipids and triglycerides.

The zebrafish is fast becoming a leading and prominent model organism used by researchers for developmental biology, and research in modeling human diseases in zebrafish is being undertaken at a fast pace. Many therapeutic areas, including oncology and cardiovascular diseases to name a few all have zebrafish models based on known disease mechanisms that are translatable to modes of action in humans. Many novel assays have been and are continuing to be developed to study human disease in zebrafish. Prominent methods to identify novel drug targets within the organism include, chemical mutagenesis, insertional mutagenesis and high throughput small molecule screens. Methods to validate potential drug targets include reverse and forward genetics, transgenesis and gene knockout. This review summarizes the important contributions made using the zebrafish model in recent years to aid in drug discovery and target validations in the highly important medical field of cancer medicine, cardiovascular disease and the emerging role of the zebrafish model as a platform for toxicity screening.

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