Hepatic Wnt/LRP6 Regulation of Plasma Lipids

Yale University, New Haven CT

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Abstract

DESCRIPTION (provided by applicant): The genetic etiology and the molecular mechanisms of combined hyperlipidemia (CHL), the most common lipid disorder of the general population is not understood. Accordingly, no single therapeutic agent is available that completely normalizes both plasma LDL and TG, and or prevent cardiovascular disease. We have identified rare loss of function mutations in Wnt coreceptor LRP6 that underlie early atherosclerosis, and metabolic phenotypes including CHL. Since our initial discovery altered plasma levels and or functions of Wnt proteins and LRP6 antagonists have been associated with risk of hyperlipidemia and early onset CAD in the general population. In addition, common variants in Wnt transcription factor TCF7L2 have been associated with familial CHL. These findings have implicated Wnt signaling in hyperlipidemia and early onset atherosclerosis. To investigate disease mechanisms, mice with the human LRP6R611C (LRP6mut/mut) point mutation were generated. LRP6mut/mut mice exhibit significantly elevated plasma triglycerides (TG) and LDL cholesterols on high cholesterol diet, which dramatically increases after they are crossbred onto LDLR/ mice. Further studies in these mice revealed enhanced expression of liver IGF1/IGF1R associated with augmented activities of AKT/mTOR pathways, leading to increased SREBP1 and 2 activation, lipid synthesis and ApoB secretion. Strikingly, these changes normalized and hyperlipidemia was rescued by systemic Wn3a administration. We have devised several mouse models and propose to study the role of canonical Wnt/ß-catenin/ TCF7L2, and their potential downstream pathways IGF1 and mTORC2 in regulation of lipid synthesis and ApoB secretion. These studies hold great promise for identifying novel pathways and potential targets for development of therapeutics against combined hyperlipidemia.