Recent work has discovered that some primate species are capable of both daily torpor and seasonal multi-day hibernation and new research in the Storey lab is identifying the biochemistry involved in primate hypometabolism. These species, including our particular model, the gray mouse lemur (Microcebus murinus), are the closest species to man that use torpor/hibernation and are therefore the best models for identifying and applying the mechanism of torpor control to human biomedical concerns. The grey mouse lemur is a small nocturnal lemur from Madagascar that experiences seasonal limitations in food supply and cool temperatures, driving them to enhance their survival during the dry season with the use of torpor/hibernation. To facilitate this, lemurs go through an autumn fattening stage that builds up body lipid reserves that in turn fuels their winter resting period which is then followed by an active summer breeding season. Both hibernation and torpor are characterized by a regulated suppression of metabolic rate, a slowing of many physiological processes (e.g., heart and breathing rates, organ perfusion, kidney filtration, and neurological activity), and heterothermy that allows core body temperature to fall to near-ambient.
In the group of lemur papers that the Storey lab has published in 2015, we put our toolkit of metabolic markers and multiplex assay methods to use for a broad-based and comprehensive analysis of the biochemical responses to daily torpor in six organs of gray mouse lemurs. The studies included analysis of torpor-responsive changes in cell signaling pathways, mRNA expression changes for selected genes that are linked with hibernation in ground squirrels, controls on transcription and translation, carbohydrate fuel regulation, and cytoprotective and immune responses to torpor.