Parenteral lipid emulsion-induced atherosclerosis in the obese Zucker rat and its lean littermate.

We have shown previously that parenterally-administered lipid emulsions can be utilized to induce early atherosclerosis in the aortas of Sprague-Dawley rats. In order to evaluate the effect of obesity on lipid-induced atherogenesis, we have utilized this same approach in the present study to demonstrate that i.v. infusions of the parenteral lipid emulsion, Lipofundin-S, will induce in the genetically obese Zucker rat and its lean littermate aortic endothelial and myofibroelastic changes indicative of early atherogenesis. Four groups of rats were used: 1) obese controls, 2) obese lipid-infused, 3) lean littermate controls, and 4) lean littermate lipid-infused. Observations were made with light and transmission electron microscopy (TEM), using qualitative morphological criteria to evaluate the results. Based on the fact that both untreated control and Lipofundin-S-induced atherosclerosis was more frequent and generally more advanced in the obese animals than in their respective lean counterparts, it appears that the obese Zucker rat is more susceptible to both spontaneous and hyperlipidemia-induced atherosclerosis than its respective lean littermate. Thus, obesity in these animals, as might be the case in humans, could potentiate an atherogenic process already enhanced by hyperlipidemia.