NR1H4 and familial hypercholesterolemia: FXR-null mice are featured with hypertriglyceridemia, hypercholesterolemia, and growing intestinal cholesterol absorption, in close association with increase in HDL cholesterol and lipoprotein lipase activity, the generation and characterization of which are a breakthrough for uncovering and verifying the importance of FXR action for lipid metabolism (Sinal et al., 2000; Lambert et al., 2003).