Plasma cholesterol and triglyceride levels are twice as high in hibernating brown bears (Ursus arctos) than healthy humans. Yet, bears display no signs of early-stage atherosclerosis development when adult. To explore this apparent paradox, we analysed plasma lipoproteins from the same ten bears in winter (hibernation) and in summer using size exclusion chromatography, ultracentrifugation and electrophoresis. LDL cholesterol binding to arterial proteoglycans, and plasma cholesterol efflux capacity were also evaluated. The data collected and analysed from bears were also compared with those from healthy humans. In bears the cholesterol esters, unesterified cholesterol, triglyceride and phospholipid content of VLDL and LDL were higher in winter than in summer. The percentage lipid composition of LDL differed between bears and humans, but did not change seasonally in bears. Bear LDL was larger, richer in triglycerides, showed pre-beta electrophoretic mobility and had 5-10 times lower binding to arterial proteoglycans than human LDL. Finally, plasma cholesterol efflux capacity was higher in bears than in humans, especially the HDL fraction when mediated by ABCA1. These results suggest that in brown bears the absence of early atherogenesis is likely associated with a lower affinity of LDL cholesterol for arterial proteoglycans and an elevated cholesterol efflux capacity of bear plasma.

中文翻译：

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棕熊（Ursus arctos）血浆脂蛋白的血管保护特性。


冬眠棕熊（Ursus arctos）的血浆胆固醇和甘油三酯水平是健康人类的两倍。然而，熊成年后并没有表现出早期动脉粥样硬化的迹象。为了探索这一明显的悖论，我们使用尺寸排阻色谱、超速离心和电泳分析了同一十只熊在冬季（冬眠）和夏季的血浆脂蛋白。还评估了低密度脂蛋白胆固醇与动脉蛋白聚糖的结合以及血浆胆固醇流出能力。从熊身上收集和分析的数据也与健康人类的数据进行了比较。熊体内VLDL和LDL的胆固醇酯、非酯化胆固醇、甘油三酯和磷脂含量冬季高于夏季。熊和人类之间的低密度脂蛋白脂质组成百分比有所不同，但熊的脂质成分百分比没有季节性变化。与人类 LDL 相比，熊 LDL 更大，甘油三酯更丰富，显示出 pre-beta 电泳迁移率，并且与动脉蛋白聚糖的结合力低 5-10 倍。最后，熊的血浆胆固醇流出能力高于人类，尤其是由 ABCA1 介导的 HDL 部分。这些结果表明，棕熊早期动脉粥样硬化形成的缺失可能与低密度脂蛋白胆固醇对动脉蛋白聚糖的亲和力较低以及熊血浆中胆固醇流出能力的升高有关。