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Am J Physiol Regul Integr Comp Physiol (August 8, 2007). doi:10.1152/ajpregu.00427.2007
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Submitted on June 18, 2007
Accepted on August 7, 2007

The molecular and biochemical basis of non-shivering thermogenesis in an African endemic mammal, Elephantulus myurus

Nomakwezi Mzilikazi1*, Martin Jastroch2, Carola W. Meyer3, and Martin Klingenspor4

1 Zoology, Nelson Mandela Metropolitan University, Port Elizabeth, Eastern Cape, South Africa
2 Department of Biology, Animal Physiology, Philipps-University of Marburg, Marburg, Germany
3 Department of Animal Physiology, Philipps-University of Marburg, Marburg, Hessen, Germany
4 Faculty of Biology, Department of Animal Physiology, Philipps-Universitat Marburg, Marburg, Hessen, Germany

* To whom correspondence should be addressed. E-mail: nomakwezi.mzilikazi{at}nmmu.ac.za.

Uncoupling protein 1 (UCP1) mediated nonshivering thermogenesis (NST) in brown adipose tissue (BAT) is an important avenue of thermoregulatory heat production in many mammalian species. Until recently, UCP1 was thought to occur exclusively in eutherians. In the light of the recent finding that UCP1 is already present in fish, it is of interest to investigate when UCP1 gained a thermogenic function in the vertebrate lineage. We elucidated the basis of NST in the rock elephant shrew, Elephantulus myurus (Afrotheria: Macroscelidea). We sequenced Ucp1 and detected Ucp1 mRNA and protein restricted to brown fat deposits. We found that cytochrome c oxidase activity was highest in these deposits when compared with liver and skeletal muscle. Consistent with a thermogenic function of UCP1 isolated BAT mitochondria showed increased state 4 respiration in the cold as well as palmitate induced, GDP sensitive proton conductance, which was absent in liver mitochondria. On the whole animal level, evidence of thermogenic function was further corroborated by an increased metabolic response to noradrenaline (NA) injection. Cold acclimation (18°C) led to an increased basal metabolic rate relative to warm acclimation (28°C) in E. myurus but there was no evidence of additional recruitment of NA induced NST capacity in response to cold acclimation. In summary, we showed that BAT and functional UCP1 are already present in a member of the Afrotheria, but the seasonal regulation and adaptive value of NST in Afrotherians remains to be elucidated.




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Plasticity of muscle function in a thermoregulating ectotherm (Crocodylus porosus): biomechanics and metabolism
Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2008; 294(3): R1024 - R1032.
[Abstract] [Full Text] [PDF]




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