THE DEGREE OF DIETARY FATTY-ACID UNSATURATION AFFECTS TORPOR PATTERNSAND LIPID-COMPOSITION OF A HIBERNATOR

Diets rich in unsaturated and polyunsaturated fatty acids have a posit ive effect on mammalian torpor, whereas diets rich in saturated fatty acids have a negative effect. To determine whether the number of doubl e bonds in dietary fatty acids are responsible for these alterations i n torpor patterns, we investigated the effect of adding to the normal diet 5% pure fatty acids of identical chain length (C18) but a differe nt number of double bonds (0, 1, or 2) on the pattern of hibernation o f the yellow-pine chipmunk, Eutamias amoenus. The response of torpor b outs to a lowering of air temperature and the mean duration of torpor bouts at an air temperature of 0.5 degrees C (stearic acid C18:0, 4.5 +/- 0.8 days, oleic acid C18:1, 8.6 +/- 0.5 days; linoleic acid C18:2, 8.5 +/- 0.7 days) differed among animals that were maintained on the three experimental diets. The mean minimum body temperatures (C18:0, 2.3 +/- 0.3 degrees C; C18:1, +0.3 +/- 0.2 degrees C; C18:2, -0.2 +/- 0.2 degrees C), which torpid Individuals defended by an increase in me tabolic rate, and the metabolic rate of torpid animals also differed a mong diet groups. Moreover, diet-induced differences were observed in the composition of total lipid fatty acids from depot fat and the phos pholipid fatty acids of cardiac mitochondria. For depot fat 7 of 13 an d for heart mitochondria 7 of 14 of the identified fatty acids differe d significantly among the three diet groups. Significant differences a mong diet groups were also observed for the sum of saturated, unsatura ted and polyunsaturated fatty acids. These diet-induced alterations of body fatty acids were correlated with some of the diet-induced differ ences in variables of torpor. The results suggest that the degree of u nsaturation of dietary fatty acids influences the composition of tissu es and membranes which in turn may influence torpor patterns and thus survival of hibernation.