Veterinary Basic Sciences, Royal Veterinary College, Hawkshead lane, North Mymms, Hertfordshire, AL9 7TA, United KingdomInstitute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, HA7 4LP, United Kingdom.
Comp Biochem Physiol A Mol Integr Physiol. 2008 Feb;149(2):203-8. doi: 10.1016/j.cbpa.2007.11.012.
Some hibernating animals are known to reduce muscle and bone loss associated with mechanical unloading during prolonged immobilisation,compared to humans. However, here we show that wild pregnant polar bears (Ursus maritimus) are the first known animals to avoid significant bone loss altogether, despite six months of continuous hibernation. Using serum biochemical markers of bone turnover, we showed that concentrations for bone resorption are not significantly increased as a consequence of hibernation in wild polar bears. This is in sharp contrast to previous studies on other hibernating species, where for example, black bears (Ursus americanus), show a 3-4 fold increase in serum bone resorption concentrations posthibernation,and must compensate for this loss through rapid bone recovery on remobilisation, to avoid the risk of fracture. In further contrast to black bears, serum concentrations of bone formation markers were highly significantly increased in pregnant female polar bears compared to non-pregnant,thus non-hibernating females both prior to and after hibernation. However, bone formation concentrations in new mothers were significantly reduced compared to pre-hibernation concentrations. The de-coupling of bone turnover in favour of bone formation prior to hibernation, suggests that wild polar bears may posses a unique physiological mechanism for building bone in protective preparation against expected osteopenia associated with disuse,starvation, and hormonal drives to mobilise calcium for reproduction, during hibernation. Understanding this physiological mechanism could have profound implications for a natural solution for the prevention of osteoporosis in animals subjected to captivity with inadequate space for exercise,humans subjected to prolonged bed rest while recovering from illness, or astronauts exposed to antigravity during spaceflight.© 2008 Elsevier Inc. All rights reserved.
一些冬眠动物在长时间的固定不动中，肌肉和骨骼的损失明显低于人类。然而，我们在这里表明，野生怀孕北极熊（Ursus maritimus）是第一个完全避免显著骨丢失的动物，尽管它们经历了六个月的连续冬眠。我们利用骨转换的血清生化标志物表明，骨吸收的浓度并没有因冬眠而显著增加。这与之前对其他冬眠物种的研究形成了鲜明的对比，例如，黑熊（Ursus americanus）在冬眠后，血清骨吸收浓度增加了 3-4 倍，必须通过快速的骨骼恢复来弥补这种损失，以避免骨折的风险。与黑熊进一步形成对比的是，与非怀孕、非冬眠的雌性相比，怀孕雌性北极熊的血清骨形成标志物浓度显著增加，无论是在冬眠前还是冬眠后。然而，新母亲的骨形成浓度与冬眠前相比显著降低。在冬眠前，骨转换的解偶联有利于骨形成，这表明野生北极熊可能拥有一种独特的生理机制，用于在与不活动、饥饿以及为了繁殖而动员钙相关的预期骨质疏松症作斗争时，构建保护性的骨骼。了解这种生理机制可能对解决因运动空间不足而被囚禁的动物、因疾病而长期卧床休息的人类或在太空飞行中受到抗重力影响的宇航员的骨质疏松症问题具有深远的意义。© 2008 Elsevier Inc. 保留所有权利。
