The relative atherogenicity of VLDL and LDL is dependent on the topographic site.
ABSTRACT: To evaluate whether the relative atherogenicity of VLDL and LDL is dependent on the topographic site, atherosclerosis was compared at four topographic sites in homozygous LDL receptor (LDLr)-deficient rabbits fed normal chow and in heterozygous LDLr-deficient rabbits with the same genetic background fed a 0.15% cholesterol diet to match cholesterol levels. VLDL cholesterol was significantly higher and LDL cholesterol significantly lower in LDLr(+/-) diet rabbits compared with LDLr(-/-) rabbits. Intimal area in the ascending thoracic aorta and in the abdominal aorta at the level of the renal arteries was 1.4-fold (P < 0.05) and 1.5-fold (P < 0.05) higher, respectively, in LDLr(-/-) rabbits than in LDLr(+/-) diet rabbits, whereas no significant difference occurred in the descending thoracic aorta and in the abdominal aorta just above the bifurcation. Differences remained statistically significant after adjustment for plasma cholesterol, triglycerides, and sex. Compared with LDLr(+/-) diet rabbits, higher intimal lipoprotein lipase (LPL) and apolipoprotein (apo) B levels were observed in LDLr(-/-) rabbits only at the level of the descending thoracic aorta. Intimal apo E levels in LDLr(-/-) rabbits were significantly lower in sites with a larger intima than in LDLr(+/-) diet rabbits. In conclusion, the relative atherogenicity of VLDL and LDL is dependent on the topographic site.
Project description:Mechanisms of atherogenesis have been studied extensively in genetically engineered mice with disturbed cholesterol metabolism such as those lacking either the LDL receptor (Ldlr) or apolipoprotein E (apoe). Few other animal models of atherosclerosis are available. WT rabbits or rats, even on high-fat or high-cholesterol diets, develop sparse atherosclerotic lesions. We examined the effects of Ldlr deletion on lipoprotein metabolism and atherosclerotic lesion formation in Sprague-Dawley rats. Deletion of Ldlr resulted in the loss of the LDLR protein and caused a significant increase in plasma total cholesterol and triglycerides. On normal chow, Ldlr-KO rats gained more weight and were more glucose intolerant than WT rats. Plasma proprotein convertase subtilisin kexin 9 (PCSK9) and leptin levels were higher and adiponectin levels were lower in KO than WT rats. On the Western diet, the KO rats displayed exaggerated obesity and age-dependent increases in glucose intolerance. No appreciable aortic lesions were observed in KO rats fed normal chow for 64 weeks or Western diet for 16 weeks; however, after 34-52 weeks of Western diet, the KO rats developed exuberant atherosclerotic lesions in the aortic arch and throughout the abdominal aorta. The Ldlr-KO rat may be a useful model for studying obesity, insulin resistance, and early-stage atherosclerosis.
Project description:Plasma very low-density lipoprotein and low-density lipoprotein (VLDL+LDL) cholesterol levels of 2 partially inbred strains of opossums (Monodelphis domestica) differ markedly when they are fed a high-cholesterol and low-fat (HCLF) diet. High-responding opossums exhibit a dramatic increase (>10-fold) in VLDL+LDL cholesterol, whereas low-responding opossums exhibit a minimal increase (<2-fold) in VLDL+LDL cholesterol. The genes responsible for the accumulation of high levels of plasma VLDL+LDL cholesterol in high-responding opossums have not yet been identified. In this study, we analyzed the expression of genes encoding for (1) 4 bile acid synthesis enzymes (CYP7A1, CYP27A1, CYP8B1, and CYP7B1); (2) 3 cholesterol synthesis enzymes (HMGCR, HMGCS1, and SQLE); (3) the LDL receptor (LDLR); (4) 2 sterol transporters (ABCG5 and ABCG8); and (5) 2 bile acid transporters (ABCB11 and SLC10A1) to determine how the expression of these genes was affected by dietary cholesterol in the 2 strains of opossums. We found differences between high and low responders in the expression of cholesterol synthesis genes on the basal diet, as well as differences in the expression of the CYP27A1, ABCG5, ABCG8, and SLC10A1 genes on the HCLF diet. CYP27A1 messenger RNA levels were lower in the livers of high responders compared with low responders, whereas CYP27A1 messenger RNA levels in extrahepatic tissues were similar in high and low responders on the HCLF diet. Low levels of CYP27A1, ABCG5, and ABCG8 expression in the liver may contribute to hypercholesterolemia in high-responding opossums.
Project description:Solid-organ transplant recipients are prone to develop atherosclerosis. The objectives of this study were to investigate the effects of Rapamune (Wyeth Canada, Saint-Larent, QC, Canada) on the rabbit model of atherosclerosis. The rabbits were assigned to four groups: group I, regular diet (control); group II, 1% cholesterol diet; group III, control with Rapamune (1 mg/kg/d orally); and group IV, high cholesterol diet with Rapamune. Blood samples for serum lipids (triglycerides [TG], total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C]), as well as malondialdehyde, and protein carbonyls, the indices of oxidative stress were collected at the end of 2 months on the respective diet regimen. Aortic tissue for atherosclerotic changes were also collected for oxidative stress indices were also collected. Rapamune reduced serum levels of TG, TC, LDL-C, and HDL-C. Rapamune elevated the oxidative stress in rabbits on high cholesterol diet. Rapamune did not attenuate extent of atherosclerosis (group II vs. group IV, 45.00 ± 12.00 vs. 57.28 ± 2.99%); intimal thickness (group II vs. group IV, 32.38 ± 7.14 × 10(3) vs. 21.90 ± 11.98 × 10(3) μm(2)); intimal/medial ratio (group II vs. group IV, 0.50 ± 0.06 vs. 0.35 ± 0.06); and macrophage accumulation (group II vs. group IV, 69.72 ± 5.02 vs. 61.52 ± 8.94%) in the intima of rabbits on high cholesterol diet. The data suggest that (1) Rapamune increased the oxidative stress in rabbits on high cholesterol diet and (2) Rapamune did not attenuate the hypercholesterolemic atherosclerosis in the rabbit model.
Project description:Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a key role in cholesterol homeostasis and atherogenesis. However, there are only limited rodent models, with a functional low-density lipoprotein receptor (LDLR) pathway and cholesteryl ester transfer protein (CETP) to evaluate the drug candidates targeting the PCSK9/LDLR pathway, that are translatable to humans. Here, by using our recently generated LDLR heterozygote (Ldlr+/-) hamster model with functional LDLR pathway and CETP function, we seek to evaluate the effect of a PCSK9 antibody, evolocumab, on dyslipidemia and atherosclerosis compared with ezetimibe, an effective inhibitor of cholesterol absorption, as a positive therapeutic control. We show that the plasma levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) were significantly increased in Ldlr+/- hamsters fed a high-fat high-cholesterol (HFHC) diet; therefore, areas of atherosclerotic lesion in the aorta were obviously increased and positively correlated with plasma LDL-C and TC. Circulating free PCSK9 was downregulated by the HFHC diet and was undetectable in the evolocumab treated group, as expected. Most importantly, either evolocumab or ezetimibe treatment prevented HFHC diet-induced hyperlipidemia and subsequent atherosclerotic plaque formation. The results indicate that Ldlr+/- hamsters fed an HFHC diet represent an ideal rodent model to evaluate drug candidates that affect LDLR pathways.
Project description:Genetic defects in LDL clearance result in severe hypercholesterolemia and premature atherosclerosis. Mutations in the LDL receptor (LDLR) cause familial hypercholesterolemia (FH), the most severe form of genetic hypercholesterolemia. A phenocopy of FH, autosomal recessive hypercholesterolemia (ARH), is due to mutations in an adaptor protein involved in LDLR internalization. Despite comparable reductions in LDL clearance rates, plasma LDL levels are substantially lower in ARH than in FH. To determine the metabolic basis for this difference, we examined the synthesis and catabolism of VLDL in murine models of FH (Ldlr(-/-)) and ARH (Arh(-/-)). The hyperlipidemic response to a high-sucrose diet was greatly attenuated in Arh(-/-) mice compared with Ldlr(-/-) mice despite similar rates of VLDL secretion. The rate of VLDL clearance was significantly higher in Arh(-/-) mice than in Ldlr(-/-) mice, suggesting that LDLR-dependent uptake of VLDL is maintained in the absence of ARH. Consistent with these findings, hepatocytes from Arh(-/-) mice (but not Ldlr(-/-) mice) internalized beta-migrating VLDL (beta-VLDL). These results demonstrate that ARH is not required for LDLR-dependent uptake of VLDL by the liver. The preservation of VLDL remnant clearance attenuates the phenotype of ARH and likely contributes to greater responsiveness to statins in ARH compared with FH.
Project description:Here we undertook a proteomic investigation of ascending aorta from New Zealand White rabbits after 10 weeks on a high (2% w/w) cholesterol diet (HCD, n=5) or control diet (n=5) in order to profile the proteomic changes in response to the HCD. Histology confirmed intimal thickening in the HCD group and LC-MS/MS analysis of individually obtained ascending aorta extracts labelled with isobaric (iTRAQ) tags led to identification and quantitation of 453 unique proteins above the 1% false discovery rate threshold. Of 67 proteins showing significant differences in relative abundance (p<0.05), 62 were elevated and five decreased in ascending aorta from HCD-fed rabbits compared to controls. Six proteins were selected for validation using Multiple Reaction Monitoring which confirmed the iTRAQ results.
Project description:Hyperlipidemia is a major risk factor for developing atherosclerosis in humans, and epidemiological studies have correlated specific lipoprotein levels with cardiovascular disease risk. Murine models of atherosclerosis rely on the induction of hyperlipidemia for vascular lesions to form, but the pathogenic contributions attributed to different lipoprotein populations are not well defined. To address this issue, we analyzed over 300 LDL receptor (LDLR) deficient mice that have been fed a high-fat diet and for which a full lipoprotein profile and aortic root atherosclerosis values were assessed. Overall, aortic root atherosclerosis is best predicted by plasma VLDL cholesterol levels with less predictive value derived from either LDL or HDL cholesterol. Triglyceride levels are more atherogenic in female mice, especially immune competent females, and depletion of the adaptive immune system leads to a global reduction in plasma lipid levels and aortic root lesion size yet does not appear to alter the atherogenic potential of individual lipoprotein subspecies. In contrast, HDL-cholesterol is a better predictor of aortic root atherosclerosis in apoE-deficient mice. In summary, this large scale analysis of high-fat diet fed LDLR deficient mice highlight the relationship between different plasma lipid components, especially VLDL-cholesterol, and aortic root atherosclerosis.
Project description:Familial hypercholesterolemia (FH) is an autosomal dominant genetic disease caused mainly by LDL receptor (Ldlr) gene mutations. Unlike FH patients, heterozygous Ldlr knockout (KO) mice do not show a dominant FH trait. Hamsters, like humans, have the cholesteryl ester transfer protein, intestine-only ApoB editing and low hepatic cholesterol synthesis. Here, we generated Ldlr-ablated hamsters using CRISPR/Cas9 technology. Homozygous Ldlr KO hamsters on a chow diet developed hypercholesterolemia with LDL as the dominant lipoprotein and spontaneous atherosclerosis. On a high-cholesterol/high-fat (HCHF) diet, these animals exhibited severe hyperlipidemia and atherosclerotic lesions in the aorta and coronary arteries. Moreover, the heterozygous Ldlr KO hamsters on a short-term HCHF diet also had overt hypercholesterolemia, which could be effectively ameliorated with several lipid-lowering drugs. Importantly, heterozygotes on 3-month HCHF diets developed accelerated lesions in the aortas and coronary arteries. Our findings demonstrate that the Ldlr KO hamster is an animal model of choice for human FH and has great potential in translational research of hyperlipidemia and coronary heart disease.
Project description:BACKGROUND AND AIMS:Heparin-binding EGF-like growth factor (HB-EGF) is a representative EGF family member that interacts with EGFR under diverse stress environment. Previously, we reported that the HB-EGF-targeting using antisense oligonucleotide (ASO) effectively suppressed an aortic aneurysm in the vessel wall and circulatory lipid levels. In this study, we further examined the effects of the HB-EGF ASO administration on the development of hyperlipidemia-associated atherosclerosis using an atherogenic mouse model. METHODS AND RESULTS:The male and female LDLR deficient mice under Western diet containing 21% fat and 0.2% cholesterol content were cotreated with control and HB-EGF ASOs for 12 weeks. We observed that the HB-EGF ASO administration effectively downregulated circulatory VLDL- and LDL-associated lipid levels in circulation; concordantly, the HB-EGF targeting effectively suppressed the development of atherosclerosis in the aorta. An EGFR blocker BIBX1382 administration suppressed the hepatic TG secretion rate, suggesting a positive role of the HB-EGF signaling for the hepatic VLDL production. We newly observed that there was a significant improvement of the insulin sensitivity by the HB-EGF ASO administration in a mouse model under the Western diet as demonstrated by the improvement of the glucose and insulin tolerances. CONCLUSION:The HB-EGF ASO administration effectively downregulated circulatory lipid levels by suppressing hepatic VLDL production rate, which leads to effective protection against atherosclerosis in the vascular wall.
Project description:Rabbits (Oryctolagus cuniculus) have been the very frequently used as animal models in the study of human lipid metabolism and atherosclerosis, because they have similar lipoprotein metabolism to humans. Most of hyperlipidemia and atherosclerosis rabbit models are produced by feeding rabbits a high-cholesterol diet. Gene editing or knockout (KO) offered another means of producing rabbit models for study of the metabolism of lipids and lipoproteins. Even so, apolipoprotein (Apo)E KO rabbits must be fed a high-cholesterol diet to induce hyperlipidemia. In this study, we used the CRISPR/Cas9 system anchored exon 7 of low-density lipoprotein receptor (LDLR) in an attempt to generate KO rabbits. We designed two sgRNA sequences located in E7:g.7055-7074 and E7:g.7102-7124 of rabbit LDLR gene, respectively. Seven LDLR-KO founder rabbits were generated, and all of them contained biallelic modifications. Various mutational LDLR amino acid sequences of the 7 founder rabbits were subjected to tertiary structure modeling with SWISS-MODEL, and results showed that the structure of EGF-A domain of each protein differs from the wild-type. All the founder rabbits spontaneously developed hypercholesterolemia and atherosclerosis on a normal chow (NC) diet. Analysis of their plasma lipids and lipoproteins at the age of 12 weeks revealed that all these KO rabbits exhibited markedly increased levels of plasma TC (the highest of which was 1013.15 mg/dl, 20-fold higher than wild-type rabbits), LDL-C (the highest of which was 730.00 mg/dl, 35-fold higher than wild-type rabbits) and TG accompanied by reduced HDL-C levels. Pathological examinations of a founder rabbit showed prominent aortic atherosclerosis lesions and coronary artery atherosclerosis.In conclusion, we have reported the generation LDLR-KO rabbit model for the study of spontaneous hypercholesterolemia and atherosclerosis on a NC diet. The LDLR-KO rabbits should be a useful rabbit model of human familial hypercholesterolemia (FH) for the simulations of human primary hypercholesterolemia and such models would allow more exact research into cardio-cerebrovascular disease.