Latitudinal Differences in the Hibernation Characteristics of Woodchucks (Marmota monax)

There is little information on the phenotypic flexibility of hibernation characteristics within species. To address this issue, we observed differences in hibernation characteristics of three free-ranging populations of woodchucks (Marmota monax) distributed along a latitudinal gradient from Maine to South Carolina. Data from free-ranging animals exhibited a direct relationship between latitude and length of the hibernation season. As expected, woodchucks in the northern latitudes hibernated longer than those in the southern latitudes. Also, the length of interbout arousals decreased with increase in latitude, whereas the length of torpor bouts and the number of arousals increased. Thus, we observed phenotypic plasticity in hibernation characteristics based primarily on latitudinal temperature differences in each population. Further analysis revealed a direct relationship between latitude and total time spent in torpor. Maine animals spent 68% more time in torpor than South Carolina animals. However, total time spent euthermic did not differ among the three populations. The cost-benefit hypothesis of hibernation may help to explain these results. It assumes that hibernators avoid the physiological stress of torpor by staying euthermic as much as possible. Woodchucks in each population maximized time spent euthermic, utilizing torpor only at the level needed to survive winter hibernation and to commence reproduction in the spring

Exploring the Bone Proteome to Help Explain Altered Bone Remodeling and Preservation of Bone Architecture and Strength in Hibernating Marmots

Periods of physical inactivity increase bone resorption and cause bone loss and increased fracture risk. However, hibernating bears, marmots, and woodchucks maintain bone structure and strength, despite being physically inactive for prolonged periods annually. We tested the hypothesis that bone turnover rates would decrease and bone structural and mechanical properties would be preserved in hibernating marmots (Marmota flaviventris). Femurs and tibias were collected from marmots during hibernation and in the summer following hibernation. Bone remodeling was significantly altered in cortical and trabecular bone during hibernation with suppressed formation and no change in resorption, unlike the increased bone resorption that occurs during disuse in humans and other animals. Trabecular bone architecture and cortical bone geometrical and mechanical properties were not different between hibernating and active marmots, but bone marrow adiposity was significantly greater in hibernators. Of the 506 proteins identified in marmot bone, 40 were significantly different in abundance between active and hibernating marmots. Monoaglycerol lipase, which plays an important role in fatty acid metabolism and the endocannabinoid system, was 98-fold higher in hibernating marmots compared with summer marmots and may play a role in regulating the changes in bone and fat metabolism that occur during hibernation

2023_12_08_BDNFPaperinGMGS_SuppFig5.pdfSupplementaryFigs-SquirrelPaperSupplementaryFigures_SquirrelPaper

Golden-Mantled Ground Squirrels exhibit dramatic seasonal fluctuations in metabolism and can fast for months while hibernating. Brain-derived neurotrophic factor is essential determinant of cellular and systemic metabolism, and in this study, we characterized seasonal fluctuations in BDNF expression, then administered the small molecule BDNF mimetic 7,8-dihydroxyflavone (DHF) in hibernating squirrels. The results indicate that activating BDNF/TrkB signaling disrupts hibernation, with implications for synaptic homeostasis in prolonged hypometabolic states.</p

2023_12_08_BDNFPaperinGMGS_SuppFig2.pdfSupplementaryFigs-SquirrelPaperSupplementaryFigures_SquirrelPaper

Golden-Mantled Ground Squirrels exhibit dramatic seasonal fluctuations in metabolism and can fast for months while hibernating. Brain-derived neurotrophic factor is essential determinant of cellular and systemic metabolism, and in this study, we characterized seasonal fluctuations in BDNF expression, then administered the small molecule BDNF mimetic 7,8-dihydroxyflavone (DHF) in hibernating squirrels. The results indicate that activating BDNF/TrkB signaling disrupts hibernation, with implications for synaptic homeostasis in prolonged hypometabolic states.</p

2023_12_08_BDNFPaperinGMGS_SuppFig1.pdfSupplementaryFigs-SquirrelPaperSupplementaryFigures_SquirrelPaper

Golden-Mantled Ground Squirrels exhibit dramatic seasonal fluctuations in metabolism and can fast for months while hibernating. Brain-derived neurotrophic factor is essential determinant of cellular and systemic metabolism, and in this study, we characterized seasonal fluctuations in BDNF expression, then administered the small molecule BDNF mimetic 7,8-dihydroxyflavone (DHF) in hibernating squirrels. The results indicate that activating BDNF/TrkB signaling disrupts hibernation, with implications for synaptic homeostasis in prolonged hypometabolic states.</p

2023_12_08_BDNFPaperinGMGS_SuppFig4.pdfSupplementaryFigs-SquirrelPaperSupplementaryFigures_SquirrelPaper

Golden-Mantled Ground Squirrels exhibit dramatic seasonal fluctuations in metabolism and can fast for months while hibernating. Brain-derived neurotrophic factor is essential determinant of cellular and systemic metabolism, and in this study, we characterized seasonal fluctuations in BDNF expression, then administered the small molecule BDNF mimetic 7,8-dihydroxyflavone (DHF) in hibernating squirrels. The results indicate that activating BDNF/TrkB signaling disrupts hibernation, with implications for synaptic homeostasis in prolonged hypometabolic states.</p

2023_12_08_BDNFPaperinGMGS_SuppFig3.pdfSupplementaryFigs-SquirrelPaperSupplementaryFigures_SquirrelPaper

Golden-Mantled Ground Squirrels exhibit dramatic seasonal fluctuations in metabolism and can fast for months while hibernating. Brain-derived neurotrophic factor is essential determinant of cellular and systemic metabolism, and in this study, we characterized seasonal fluctuations in BDNF expression, then administered the small molecule BDNF mimetic 7,8-dihydroxyflavone (DHF) in hibernating squirrels. The results indicate that activating BDNF/TrkB signaling disrupts hibernation, with implications for synaptic homeostasis in prolonged hypometabolic states.</p