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

点击翻译按钮获取中文摘要

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.