Insights From Liver-Humanized Mice on Cholesterol Lipoprotein Metabolism and LXR-Agonist Pharmacodynamics in Humans

Genetically modified mice have been extensively used to study human disease. However, the data gained are not always translatable to humans because of major species differences. Liver‐humanized mice (LHM) are considered a promising model to study human hepatic and systemic metabolism. Therefore, we aimed to further explore their lipoprotein metabolism and to characterize key hepatic species‐related, physiological differences. Fah‐/‐, Rag2‐/‐, Il2rg‐/‐ (FRG®‐KO) mice on the non‐obese diabetic (NOD) background (FRGN) were repopulated with primary human hepatocytes from different donors. Cholesterol lipoprotein profiles of LHM showed a human‐like pattern, characterized by high ratio of low‐density lipoprotein (LDL) to high‐density lipoprotein (HDL), and dependency on the human donor. This pattern was determined by a higher level of apolipoprotein (APO) B100 in circulation, as a result of lower hepatic APOB mRNA editing and LDL receptor (LDLR) expression, and higher levels of circulating proprotein convertase subtilisin/kexin type 9 (PCSK9). As a consequence, LHM lipoproteins bound to human aortic proteoglycans in a pattern similar to human lipoproteins. Unexpectedly, cholesteryl ester transfer protein (CETP) was not required to determine the human‐like cholesterol lipoprotein profile. Moreover, LHM treated with GW3965 mimicked the negative lipid outcomes of the first human trial of liver X receptor (LXR) stimulation, i.e. a dramatic increase of cholesterol and triglycerides in circulation. Innovatively, LHM allowed the characterization of these effects at molecular level. Conclusions LHM represent an interesting translatable model of human hepatic and lipoprotein metabolism. Since several metabolic parameters displayed donor‐dependency, LHM may also be employed in studies for personalized medicine.