Insulin resistance in mammalian hibernators

Mammals that undergo winter hibernation prepare by dramatically increasing food intake and consequently, body fat stores during the summer and early autumn. Several species (e.g. genus: Marmota, Spermophilus, Glis, and Cricetus) nearly double their body mass in the form of fat. The consequence of this significant increase in fat mass has been shown to be hyperinsulinemia, peripheral insulin resistance, and elevated serum glucose levels in all species investigated thus far. In reviewing the data reported for these mammals that undergo torpor bouts during winter hibernation, the impact of the marked increase in fat mass on the regulation of glucose and fatty acids by insulin will be discussed. Furthermore, our recent data on the role of leptin and adiponectin in the yellow‐bellied marmot (M. flaviventris) will be included since there is evidence that these adipokines may be involved in regulating glucose and fatty acid metabolism to improve insulin resistance.