Figure 4.

Activities of plasma phospholipids and cholesteryl-esters transfer enzymes according to season. Enzymatic activities of (A) cholesteryl ester transfer protein (‘CETP’), (B) lecithin-cholesterol acyltransferase (‘LCAT’), and (C) phospholipid transfer protein (‘PLTP’) were measured in blood plasma from summer active (‘summer’) and winter hibernating (‘winter’) brown bears. The specific reaction catalyzed by each of the enzymes is depicted of the right side inside from each graph. (D) CETP transfers cholesteryl-esters (‘CE’) from high-density lipoprotein (‘HDL’) to low-density lipoprotein (‘LDL’) in exchange to triacylglycerols (‘TAG’). (E) LCAT converts free cholesterol (‘CHF’) into CE, which is then sequestered in HDL. (F) PLTP mediates the transfer of CHF and phospholipids (‘PL’) from very low-density lipoprotein (‘VLDL’) and LDL into HDL. In contrast to summer active individuals, winter hibernating bears were all torpid as indicated by their body temperature during hibernation (see Table 1). Error bars represent standard errors. Winter levels differing significantly from their respective summer level are denoted by subscripts (**p < 0.01, ***p < 0.001).