Brown bears build up large fat reserves as a source of energy to fuel their hibernation. Despite the total physical inactivity, however, hibernating bears do not develop any cardiovascular disease during several months in winter. An international study led by Vetmeduni that was recently published in Scientific Reports shows that brown bears have effective protective mechanisms during hibernation to prevent damage to their blood plasma and muscles despite profound changes in their lipid metabolism and elevated lipid levels.
To investigate the mechanisms by which hibernators avoid the metabolic disorder known as atherogenic dyslipidemia during hibernation, the researchers assessed lipoprotein and cholesterol metabolisms of free‑ranging Scandinavian brown bears (Ursus arctos) by measuring lipoprotein sizes, subclasses and composition, triglyceride‑related plasma‑enzyme activities, and muscle lipid composition along with plasma‑levels of antioxidant capacities and inflammatory markers in bears during winter and summer. Their findings: “Although nearly all lipid levels were higher in the winter, a nearly one-third increase in activity of cholesteryl ester transfer protein, a key enzyme involved in cholesterol recycling based on futile cycles of re-esterification via lipoprotein metabolism, helped to stabilize the lipid composition of high‑density lipoproteins (HDL). The concentration of inflammatory metabolites declined in winter and correlated inversely with cardioprotective HDL2b‑proportions and HDL sizes that increased during hibernation,” says first author Sylvain Giroud, a wildlife and physiological ecologist at the Research Institute of Wildlife Ecology at Vetmeduni.
The article „Hibernating brown bears are protected against atherogenic dyslipidemia“ by Sylvain Giroud, Isabelle Chery, Mathilde Arrivé, Michel Prost, Julie Zumsteg, Dimitri Heintz, Alina L. Evans, Guillemette Gauquelin‑Koch, Jon M. Arnemo, Jon E. Swenson, Etienne Lefai, Fabrice Bertile, Chantal Simon, and Stéphane Blanc was published in Scientific Reports veröffentlicht.
Vetmeduni press release