Abstract
Elevated triglycerides are associated with an increased risk of cardiovascular disease (CVD). Therefore, it is very important to understand the metabolism of triglyceride-rich lipoproteins (TRLs) and their atherogenic role in animal models. Using low-density lipoprotein receptor knockout (LDLR−/−) Syrian golden hamsters, this study showed that unlike LDLR−/− mice, when LDLR−/− hamsters were fed a high cholesterol high-fat diet (HFD), they had very high plasma levels of triglycerides and cholesterol. We found that LDLR−/− hamsters exhibited increased serum TRLs and the ApoB100 and 48 in these particles after being fed with HFD. Treatment with ezetimibe for 2 weeks decreased these large particles but not the LDL. In addition, ezetimibe simultaneously reduced ApoB48 and ApoE in plasma and TRLs. The expression of LRP1 did not change in the liver. These findings suggested that the significantly reduced large particles were mainly chylomicron remnants, and further, the remnants were mainly cleared by the LDL receptor in hamsters. After 40 days on an HFD, LDLR−/− hamsters had accelerated aortic atherosclerosis, accompanied by severe fatty liver, and ezetimibe treatment reduced the consequences of hyperlipidemia. Compared with the serum from LDLR−/− hamsters, that from ezetimibe-treated LDLR−/− hamsters decreased the expression of vascular adhesion factors in vascular endothelial cells and lipid uptake by macrophages. Our results suggested that in the LDLR−/− hamster model, intestinally-derived lipoprotein remnants are highly atherogenic and the inflammatory response of the endothelium and foam cells from macrophages triggered atherosclerosis. The LDL receptor might be very important for chylomicrons remnant clearance in the Syrian golden hamster, and this may not be compensated by another pathway. We suggest that the LDLR−/− hamster is a good model for the study of TRLs-related diseases as it mimics more complex hyperlipidemia.
Highlights
Cardiovascular diseases are a leading cause of death and are associated with metabolic syndromes including hyperlipidemia, non-alcohol fatty liver, diabetes, hypertension, and obesity [1, 2]
We found that low-density lipoprotein receptor (LDLR)−/− hamsters had significantly higher total cholesterol and triglyceride levels in the plasma when fed with chow diet (CD), compared with LDLR−/− mice (Figures 1A,B)
Our results showed that dietary lipids predominantly increased large particles of plasma lipoproteins in the Syrian golden hamster, especially in the LDLR−/− hamster model
Summary
Cardiovascular diseases are a leading cause of death and are associated with metabolic syndromes including hyperlipidemia, non-alcohol fatty liver, diabetes, hypertension, and obesity [1, 2]. Atherosclerosis is the underlying pathology of many cardiovascular diseases (CVD), while hyperlipidemia is the most common contributing factor. Animal models of atherosclerosis have demonstrated that plaque formation begins with the infiltration and oxidation of low-density lipoproteins (LDL) in the arterial wall [3]. While it has previously been demonstrated that severe hypertriglyceridemia promoted atherosclerosis in lipoprotein lipase knockout (LPL−/−) mice, disease progression was very slow, taking more than 1 year to detect atherosclerosis [5]. It is possible that very large lipoprotein particles in LPLdeficient animal models have difficulty entering the arterial wall. A more appropriate animal model is required to investigate the role of TRLs in atherosclerosis
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