Hibernation and disuse osteoporosis

Zimmerman, Gail D.; McKean, Thomas; Hardt, Alfred B.

doi:10.1016/0011-2240(76)90163-2

Cited by 13 publications

(10 citation statements)

References 13 publications

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“…This differs from previous studies of sciatic neurectomy during hibernation in thirteen‐lined ground squirrels where Zimmerman et al. () found that during the summer months, but not during hibernation, neurectomy led to a loss of bone and muscle mass. Why Zimmerman et al.…”

Section: Discussionmentioning

confidence: 51%

The effects of hibernation and forced disuse (neurectomy) on bone properties in arctic ground squirrels

Bogren

Johnston

Barati

et al. 2016

Physiological Reports

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Bone loss is a well‐known medical consequence of disuse such as in long‐term space flight. Immobilization in many animals mimics the effects of space flight on bone mineral density. Decreases in metabolism are also thought to contribute to a loss of skeletal mass. Hibernating mammals provide a natural model of disuse and metabolic suppression. Hibernating ground squirrels have been shown to maintain bone strength despite long periods of disuse and decreased metabolism during torpor. This study examined if the lack of bone loss during torpor was a result of the decrease in metabolic rate during torpor or an evolutionary change in these animals affording protection against disuse. We delineated changes in bone density during natural disuse (torpor) and forced disuse (sciatic neurectomy) in the hind limbs of the arctic ground squirrel (AGS) over an entire year. We hypothesized that the animals would be resistant to bone loss due to immobilization and disuse during the winter hibernation season when metabolism is depressed but not the summer active season. This hypothesis was not supported. The animals maintained bone density (dual‐energy X‐ray absorptiometry) and most bone structural and mechanical properties in both seasons. This was observed in both natural and forced disuse, regardless of the known metabolic rate increase during the summer. However, trabecular bone volume fraction (microcomputed tomography) in the distal femur was lower in neurectomized AGS at the study endpoint. These results demonstrate a need to better understand the relationship between skeletal load (use) and bone density that may lead to therapeutics or strategies to maintain bone density in disuse conditions.

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Section: Discussionmentioning

confidence: 51%

The effects of hibernation and forced disuse (neurectomy) on bone properties in arctic ground squirrels

Bogren

Johnston

Barati

et al. 2016

Physiological Reports

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“…Zimmerman et al investigated the effects of disuse on bone composition in both active and hibernating thirteen-lined ground squirrels. Active animals were immobilized by subjecting one hindlimb to sciatic nerve section; the immobilized limbs had significantly lower muscle mass, bone mass, total bone calcium, percentage calcium and percentage phosphorus than those of active control animals (Zimmerman et al, 1976). After 30 days of hibernation, bone calcium and phosphorus content were comparable with values from the active control group; histological analysis of bone from the hibernation group also supported the maintenance of bone tissue.…”

Section: Discussionmentioning

confidence: 87%

“…Zimmerman et al also investigated long-term effects. Following 150days of hibernation, a few enlarged lacunae were observed and there were still no changes in phosphorus or calcium content (Zimmerman et al, 1976). Conversely, when comparing interradicular alveolar bone between nonhibernating and hibernating ground squirrels, hibernating animals had an increased number of lacunae and an overall 'foamy' appearance, consistent with osteocytic osteolysis (Haller and Zimny, 1977).…”

Section: Discussionmentioning

confidence: 97%

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Bone strength is maintained after 8 months of inactivity in hibernating golden-mantled ground squirrels, Spermophilus lateralis

Utz

Nelson

O’Toole

et al. 2009

Journal of Experimental Biology

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SUMMARYProlonged inactivity leads to disuse atrophy, a loss of muscle and bone mass. Hibernating mammals are inactive for 6-9 months per year but must return to full activity immediately after completing hibernation. This necessity for immediate recovery presents an intriguing conundrum, as many mammals require two to three times the period of inactivity to recover full bone strength. Therefore, if hibernators experience typical levels of bone disuse atrophy during hibernation, there would be inadequate time available to recover during the summer active season. We examined whether there were mechanical consequences as a result of the extended inactivity of hibernation. We dissected femur and tibia bones from squirrels in various stages of the annual hibernation cycle and measured the amount of force required to fracture these bones. Three groups were investigated; summer active animals were captured during the summer and immediately killed, animals in the 1 month detraining group were captured in the summer and killed following a 1-month period of restricted mobility, hibernating animals were killed after 8 months of inactivity. A three-point bend test was employed to measure the force required to break the bones. Apparent flexural strength and apparent flexural modulus (material stiffness) were calculated for femurs. There were no differences between groups for femur fracture force, tibia fracture force, or femur flexural strength. Femur flexural modulus was significantly less for the 1 month detraining group than for the hibernation and summer active groups. Thus, hibernators seem resistant to the deleterious effects of prolonged inactivity during the winter. However, they may be susceptible to immobilization-induced bone loss during the summer.

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“…Most previous studies of hibernation-induced bone loss in small hibernating mammals, however, were largely or solely observational rather than quantitative (42,69,97,99,138,210), and thus, the conclusions that can be drawn from them are limited. For example, although osteocyte lacunar size has been reported to increase in bats, hamsters, and ground squirrels, only one study on hamsters has quantified lacunar area (172), whereas other studies reported histological images without quantitative measurements (42,69,97,99,197,210). Comparisons of hibernating to active counterparts are difficult to interpret as well.…”

Section: Effects Of Hibernation On Bones In Small Mammalsmentioning

confidence: 93%

Mammalian hibernation as a model of disuse osteoporosis: the effects of physical inactivity on bone metabolism, structure, and strength

McGee‐Lawrence¹,

Carey²,

Donahue³

2008

American Journal of Physiology-Regulatory, Integrative and Comp

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Reduced skeletal loading typically leads to bone loss because bone formation and bone resorption become unbalanced. Hibernation is a natural model of musculoskeletal disuse because hibernating animals greatly reduce weight-bearing activity, and therefore, they would be expected to lose bone. Some evidence suggests that small mammals like ground squirrels, bats, and hamsters do lose bone during hibernation, but the mechanism of bone loss is unclear. In contrast, hibernating bears maintain balanced bone remodeling and preserve bone structure and strength. Differences in the skeletal responses of bears and smaller mammals to hibernation may be due to differences in their hibernation patterns; smaller mammals may excrete calcium liberated from bone during periodic arousals throughout hibernation, leading to progressive bone loss over time, whereas bears may have evolved more sophisticated physiological processes to recycle calcium, prevent hypercalcemia, and maintain bone integrity. Investigating the roles of neural and hormonal control of bear bone metabolism could give valuable insight into translating the mechanisms that prevent disuse-induced bone loss in bears into novel therapies for treating osteoporosis.

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Hibernation and disuse osteoporosis

Cited by 13 publications

References 13 publications

The effects of hibernation and forced disuse (neurectomy) on bone properties in arctic ground squirrels

The effects of hibernation and forced disuse (neurectomy) on bone properties in arctic ground squirrels

Bone strength is maintained after 8 months of inactivity in hibernating golden-mantled ground squirrels, Spermophilus lateralis

Mammalian hibernation as a model of disuse osteoporosis: the effects of physical inactivity on bone metabolism, structure, and strength

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