Running head: Basis of nonshivering thermogenesis in E. myurus

The molecular and biochemical basis of non-shivering thermogenesis in an African 1 endemic mammal, Elephantulus myurus 2 3 Nomakwezi Mzilikazi*, Martin Jastroch, Carola W Meyer and Martin Klingenspor 4 *To whom correspondence should be addressed 5 Department of Zoology, Nelson Mandela Metropolitan University, P.O. Box 77000, Port 6 Elizabeth, 6031, SOUTH AFRICA 7 Email: [email protected] 8 Tel: +27 41 504 2421 9 Fax: +27 41 504 2317 10 Department of Animal Physiology, Faculty of Biology, Philipps Universität Marburg, 11 Karl von Frisch Str.8, Marburg, 35043, GERMANY 12 [email protected] 13 14 15 Abstract 16 Uncoupling protein 1 (UCP1) mediated nonshivering thermogenesis (NST) in brown 17 adipose tissue (BAT) is an important avenue of thermoregulatory heat production in 18 many mammalian species. Until recently, UCP1 was thought to occur exclusively in 19 eutherians. In the light of the recent finding that UCP1 is already present in fish, it is of 20 interest to investigate when UCP1 gained a thermogenic function in the vertebrate 21 lineage. We elucidated the basis of NST in the rock elephant shrew, Elephantulus myurus 22 (Afrotheria: Macroscelidea). We sequenced Ucp1 and detected Ucp1 mRNA and protein 23 restricted to brown fat deposits. We found that cytochrome c oxidase activity was 24 highest in these deposits when compared with liver and skeletal muscle. Consistent with 25 a thermogenic function of UCP1 isolated BAT mitochondria showed increased state 4 26 respiration in the cold as well as palmitate induced, GDP sensitive proton conductance, 27 which was absent in liver mitochondria. On the whole animal level, evidence of 28 thermogenic function was further corroborated by an increased metabolic response to 29 noradrenaline (NA) injection. Cold acclimation (18°C) led to an increased basal 30 metabolic rate relative to warm acclimation (28°C) in E. myurus but there was no 31 evidence of additional recruitment of NA induced NST capacity in response to cold 32 acclimation. In summary, we showed that BAT and functional UCP1 are already present 33 in a member of the Afrotheria, but the seasonal regulation and adaptive value of NST in 34 Afrotherians remains to be elucidated. 35 36