Abstract 1313: A Novel Pathway for the Regulation of Hepatic Cholesterol Synthesis by microRNA’s
Dietary fat has been shown to cause substantial changes in hepatic lipid and lipoprotein metabolism. The objective of this study was to observe through systems biology the hepatic response to a typical Western diet rich in saturated fats. C57BL6 mice were fed a high fat diet (42% cal. from fat) or normal chow for 3 weeks. The complete microRNA (miRNA) and mRNA gene expression profiles were determined by LC Sciences microfluidics and Affymetrix microarrays, respectively; and were validated by real-time PCR. We observed significant differential expression of 12 miRNAs and 89 mRNAs. 2D-DIGE electrophoresis and Tandem Mass Tag Spectrometry were used to profile differential protein expression, and 84 (2D)/131 (TMT) unique and differentially abundant proteins were identified by these techniques. Furthermore, we observed numerous metabolic changes as determined by GC-MS. Pathway level analysis of gene expression (PLAGE) indentified the sterol biosynthetic pathway as being one of the most active pathways in response to dietary fat. A majority of the top most down-regulated mRNAs were found to be essential components (enzymes) within the cholesterol biosynthesis pathway (14/16). Six of these 14 altered mRNAs are the direct targets of our top most up-regulated miRNAs. We experimentally validated the targeting of these predictions biochemically, using synthetic miRNAs. Mmu-mir-690,699,710 and 329 were all confirmed to significantly knockdown multiple enzymes (mRNA) in the cholesterol biosynthesis pathway with resulting precursor metabolite accumulation. In addition to identifying a novel mechanism for cholesterol regulation through miRNAs, we have used these organized data sets to develop and test novel hypotheses related to a potential new treatment for Smith-Lemli Opitz Syndrome, a disorder of cholesterol metabolism. In summary, we have used a systems biology approach to explore previously unknown relationships involved in the intricate hepatic response to dietary fat with a focus on cholesterol regulation. The integration and organization of multiple datasets, utilizing software for data conceptualization, proved invaluable in observing novel mechanisms of fat-sensing and gene regulatory responses with metabolic outcomes.