¿Por qué los osos pardos están protegidos contra la aterosclerosis a pesar de que sus niveles de colesterol plasmático doblan al de los humanos?

Plasma cholesterol and triglyceride levels are twice as high in hibernating brown bears (Ursus arctos) than in healthy humans. Yet, bears display no sign of atherosclerosis development. To explore this apparent paradox, we analyzed lipoproteins from same ten individual bears plasma collected during winter (hibernation; February) and summer (active; June) in the same year. Plasma from fourteen healthy humans were analyzed as comparator. We used standard methods for lipoprotein isolation, composition and functional investigation. The results shows that in brown bears the absence of atherosclerosis despite elevated cholesterol is likely associated with two main athero-protective properties of circulating lipoproteins. First, a significant ten times lower affinity of low-density-lipoprotein (LDL) particles for arterial proteoglycans and secondly, an elevated plasma cholesterol efflux capacity. What does the brown bear data tell us? That elevated total cholesterol and ApoB-containing lipoproteins not always associates with atherosclerosis disease. We need to look also at the lipoprotein biochemical features and functionality as they are relevant for arterial pathophysiology. What is the translatability into human of these results? We humans need to control our total and LDL-cholesterol levels. We are not brown bears!