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Background: Metabolic syndrome (MetS) is a cluster of risk factors that predisposes individuals to develop atherosclerotic cardiovascular disease, type 2 diabetes mellitus, and nonalcoholic fatty liver disease. Dyslipidemia is an essential element of MetS. Mice lack cholesterol ester transfer protein (CETP) and rapidly clear ApoB-containing lipoprotein and are resistant to the development of dyslipidemia and clinically relevant metabolic phenotypes when challenged with high fat, high cholesterol Western-type diet (WTD). We hypothesized that the presence of CETP and ApoB-containing lipoproteins would sensitize mice to the development of dyslipidemia and exacerbate metabolic phenotypes. Approach and Results: Male and female (n=7-11) C57Bl6/J mice harboring a human CETP transgene, a human ApoB100 transgene, or both transgenes were placed on a WTD (42% kCal fat, 0.2% cholesterol). Adiposity, insulin sensitivity, glucose tolerance and plasma cholesterol were assessed at the midpoint and termination of the study. Mice were anesthetized, basal bile was collected (30 min), euthanized via cardiac puncture, and tissues dissected and snap frozen. One lobe of the liver was additionally fixed for histological analysis. In both females and males, CETP/ApoB100 and ApoB100 transgenic mice showed a robust increase in total plasma cholesterol and LDL-C. The presence of CETP further increased LDL-C in ApoB100 expressing mice and modestly reduced HDL-C. Differences in body weight were not observed across genotypes. However, ApoB100 expression reduced adiposity in females, but not males. Conversely, the presence of either ApoB100 or CETP impaired insulin sensitivity in male, but not female mice. Liver histology showed increased hepatocyte ballooning in ApoB100 and CETP/ApoB100 transgenic mice, but other measures of NAFLD were unaffected. Conclusions: Mice expressing CETP/ApoB100 transgenes develop dyslipidemia more consistent with human lipoprotein profiles. The humanized lipoprotein profile reveals sexually dimorphic responses to WTD.

Background: Insulin signaling regulates a variety of features of hepatic lipid and lipoprotein metabolism. Liver-specific deletion of insulin receptor (LIRKO) reduces plasma HDL, an effect attributed to a reduction in deiodinase 2 expression and apolipoprotein (Apo) AI mRNA expression. We report a concomitant accumulation of ApoAI protein in the liver of LIRKO mice in a yet to be fully characterized compartment within hepatocytes. Methods: Mice harboring loxP sites within the insulin receptor gene (IR fl/fl ) were administered a control adenoassociated viral vector (AAV-Empty) or an AAV encoding Cre recombinase under the control of a liver-specific promoter (AAV_TBG-Cre) at 8 weeks of age to generate Control and LIRKO mice. Male and female mice were evaluated for the abundance of ApoAI in liver and total and FPLC-fractionated plasma. ApoAI secretion rates were evaluated in primary hepatocytes from both genotypes. Subcellular localization of ApoAI in liver of Control and LIRKO mice was evaluated by immunofluorescence microscopy and biochemical fractionation. Results: The loss of hepatic insulin receptor and signaling was confirmed by rtPCR, immunoblot analysis and glucose tolerance test. Whereas ApoAI was unaffected in LIRKO mice compared to controls, protein levels were reduced in plasma and elevated in liver. In contrast, no changes were observed for ApoB or ApoE in either liver or plasma. FPLC fractionation of plasma indicates a shift in HDL size and an accumulation of ApoM in the HDL fractions. Secretion rates of newly synthesized ApoAI were modestly reduced in primary hepatocytes isolated from LIRKO mice. Immunolocalization of ApoAI demonstrated accumulation in large, membrane-bound organelles located peripherally in cells. These organelles stained positively for LampI and other markers of the endosomal-lysosomal system. However, markers of the endosomal-lysosomal compartment in perinuclear regions of the cells were negative for ApoAI. Conclusions: Insulin signaling is a regulator of ApoAI secretion that alters the intracellular itinerary of ApoAI in the secretory and endocytic pathways and alters the plasma HDL proteome in mice.