Seasonal changes in fatty acids and leptin contents in the plasma of the European brown bear (Ursus arctos arctos)

Abstract

The goal of this study was to examine whether or not the preparation of the bear to winter sleep requires changes in the composition of plasma fatty acids similar to those observed in deep hibernators. Seasonal changes in plasma fatty acids of six captive European brown bears (Ursus arctos arctos) were investigated between 1991 and 1996. Altogether fifty plasma samples were analysed chromatographically. The weight percentage of unsaturated to saturated fatty acids was 37.1% in winter but only 32.3% in summer. The proportions of palmitic (16:0), octadec-11-enoic (18:1n-7), arachidonic (20:4n-6), and docosahexaenoic (22:6n-3) acids increased significantly in the total fatty acid pool in winter. At the same time, a significant decrease in concentrations of heptadecanoic (17:0), stearic (18:0), oleic (18:1n-9), γ-linolenic (18:3n-6), α-linolenic (18:3n-3) and eicosapentaenoic (20:5n-3) acids was observed. Some fatty acids also act as precursors in the synthesis of specific tissue hormones. The leptin level reached its maximum just prior to winter sleep, i.e. when fat reserves were greatest.