Studies on mechanism of heat production in the house musk shrew (Suncus murinus) with unstable body temperature.

家麝鼠是一种独特的实验动物，被认为是不耐寒的。当它被保存在低温室内时，它会变得低温，不能移动，最终死亡。1)我们发现Suncus比小鼠更容易受到寒冷的影响，他们耐寒的一个原因是棕色脂肪组织(IBAT)的产热故障和脂肪消耗(IBAT)。2)温和的冷暴露或高脂饮食本身都不会诱导蝙蝠解偶联蛋白1(Ucp1)和II型5‘-脱碘酶(D2)的mRNAs上调。然而，冷暴露和高脂饮食的组合显著增加了这两个mRNAs。因此，Suncus的耐寒性可能部分是由饲料成分引起的。3)我们克隆了Suncus Ucp1基因，并将其与其他物种进行了比较。推导的氨基酸序列与其他哺乳动物的UCP1高度同源。Northern印迹分析显示，蝙蝠和其他哺乳动物一样，都有mRNA。然而，在一个重要的生热残基中观察到了氨基酸残基的不同。基因组序列分析表明，这种差异存在于我们两个遗传距离较远的实验室群体中。这些结果表明，Suncus的耐冷性可能源于UCP1的低生热活性。

The house musk shrew (Suncus murinus), or suncus, is a unique experimental animal that is thought to be cold intolerant. When it is maintained in low temperature room, it becomes hypothermic, immobile, and eventually dies.1) We found that the suncus are more susceptible to cold than mice, and that one reason for their cold intolerance is a malfunction of heat production and lipid depletion in brown adipose tissue (IBAT).2) Neither mild cold exposure nor a high-fat diet alone induced up-regulation of the mRNAs for uncoupling protein 1 (Ucp1) and type II 5'-deiodinase (D2) in BAT. However, combinations of cold exposure and high-fat diet significantly increased both mRNAs. Therefore, cold intolerance in suncus may be partly caused by dietary components.3) We did cDNA cloning of suncus Ucp1 and compared it to other species. The deduced amino acid sequence showed high homology with other mammalian UCP1. Northern blot analysis revealed mRNA in BAT as in other mammals. However, a difference in an amino acid residue was observed in an important residue for thermogenesis. Genomic sequence analysis showed that this difference existed in our two genetically distant laboratory colonies. These results suggest that the cold intolerance in suncus may be derived from low thermogenic activity of UCP1.