Seasonal Changes in Fatty Acid Content in Skeletal Muscle of the Long-Tailed Ground Squirrel Urocitellus undulatus

Seasonal changes in fatty acid composition in four skeletal muscles of the true hibernating Yakutian long-tailed ground squirrel Urocitellus undulatus were studied. Measurements were taken on animals of four experimental groups: summer active, autumn active, winter hibernating, and winter active. An increase in total fatty acids was found in winter in the quadriceps femoris muscle (m. vastus lateralis), triceps forearm muscle (m. triceps), and lumbar muscle (m. psoas). A decrease in the total content of saturated fatty acids in all muscles was observed during the winter period. The increase in the total content of monounsaturated fatty acids in winter hibernating animals occurred in the quadriceps femoris muscle, triceps forearm muscle, and lumbar muscle. In winter active animals, the total content of polyunsaturated fatty acids increased in quadriceps femoris muscle and lumbar muscle. A statistically significant decrease in the content of palmitic acid in hibernating and winter active animals compared to summer and autumn animals was found in all muscles studied. The content of palmitoleic acid increased in hibernating animals in the quadriceps femoris muscle and lumbar muscle. In the triceps forearm muscle, the content of palmitoleic acid was increased in autumn active and winter hibernating animals. The content of oleic acid was elevated in all muscles in winter hibernating animals relative to active autumn animals. Linoleic acid content was significantly increased in winter active animals in all muscles except the calf muscle. Dihomo-gamma-linolenic acid increased in all muscles during the autumn period with a decrease in content in winter hibernating and winter active animals to the level of summer (seasonal) controls. The results obtained indicate that most of the changes in fatty acid composition have the same direction in all four studied skeletal muscles of the long-tailed ground squirrel. The possible role of seasonal changes in fatty acid composition and fatty acid participation in biochemical processes in the muscle tissue of the long-tailed ground squirrel is discussed.