A rare gain of function variant of hepatic lipase attenuates hypercholesterolemia and atherosclerosis in mice via an LDL receptor-independent mechanism

Abstract

Aims LIPC encodes hepatic lipase (HL), a liver-bound protein with both phospholipase and triglyceride lipase activity, and involved in the catabolism of circulating lipoproteins. We recently identified the gain-of-function variant HL-E97G, with selectively increased phospholipase activity, as a new genetic cause of familial combined hypocholesterolemia in humans. The role of HL in the development of atherosclerosis remains controversial. In this context, the action of HL-E97G on the development of atherosclerosis remains unknown. Methods and Results To evaluate the lipid-lowering and anti-atherogenic properties of HL-E97G versus wild-type HL (HL-WT) in hypercholesterolemic APOE*3-Leiden.CETP mice, a well-established model for human-like lipoprotein metabolism, and to assess dependence of these effects on the LDL receptor (LDLR) pathway in LDLR-deficient (Ldlr-/-) mice. APOE*3.Leiden.CETP mice or Ldlr-/- mice received an intravenous injection of AAV8 expressing either eGFP (control), HL-WT or HL-E97G (3×1011 GC/mouse) while being fed pro-atherogenic diets. Plasma cholesterol levels were measured monthly, and aortic atherosclerotic lesion sizes were assessed at termination. HL-E97G largely decreased plasma total cholesterol exposure in APOE*3-Leiden.CETP mice (-63% vs control; -58% vs HL-WT), resulting at least in part from increased uptake of (V)LDL by the liver, accompanied by a marked decrease in atherosclerotic lesion size (-98% vs control; -97% vs HL-WT) in the aortic root. Importantly, HL-E97G also strongly reduced plasma cholesterol exposure in Ldlr-/- mice (-80% vs control; -77% vs HL-WT), and decreased atherosclerotic lesion size in the aortic root (-54% vs control; -41% vs HL-WT) and the aortic arch (-73% vs control; -70% vs HL-WT). Conclusions HL-E97G strongly reduces plasma cholesterol levels, by increasing the uptake of (V)LDL, to decrease atherosclerosis development in mice independently of the LDLR pathway. These data suggest that modulating HL function is a promising tool in patients with familial hypercholesterolemia.