Change in Ucp1 mRNA Expression Following Long-Term Cold Exposure under Normal or High-Fat Diet Regimes in the Cold-Intolerant Mammal, Suncus murinus

Abstract

The house musk shrew (Suncus murinus), or suncus, is a unique experimental mammal that is cold intolerant. However, even basic knowledge of brown adipose tissue (BAT), which is important for non-shivering thermogenesis (NST), is minimal. Therefore, we exposed suncus for 18 days to mild cold temperatures (8-14°C) and/or a high-fat diet, which are factors that increase NST, and measured two mRNAs that are critical for NST in BAT, uncoupling protein 1 (Ucp1) and type II 5 ' -deiodinase (D2

Changes in Ucp1, D2 (Dio2) and Glut4 (Slc2a4) mRNA Expression in Response to Short-Term Cold Exposure in the House Musk Shrew (Suncus murinus)

“…In general, Ucp1 expression is strongly regulated by the sympathetic nervous system. The weak increase of Ucp1 was likely caused by suppression of the sympathetic nervous activity in BAT by a high-protein and low-fat diet, as in our previous study [36].…”

“…6a, b). Because longterm exposure (18 d) to mild cold (8.5-14.6°C) with standard trout pellets did not lead to augmented Ucp1 expression levels [36], we conclude that Ucp1 up-regulation in suncus eating standard trout pellets only occurs immediately after cold exposure. Ucp1 expression in suncus may decline to normal levels after the initial increase, as it does in hamsters [45].…”

“…To elucidate the mechanisms underlying cold-intolerance in suncus, we examined Ucp1 mRNA changes in interscapular brown adipose tissue (IBAT) during long-term (18 d) cold exposure [36]. In our pilot study, most immobile or dead suncus were observed within 1 week after exposure to severe cold (6-8°C), suggesting that the adaptive response in the early phase of cold exposure is critical for suncus survival in a cold environment.…”

Uncoupling protein 1 expression and high-fat diets

“…Comparable data are reported for the house shrew (69). Notably, different mouse strains were employed in the two contradicting mouse studies above, and others have already demonstrated a diverging response of different strains to HFD at 5°C (12).…”

“…Twenty-three employed the mouse as an animal model (1, 3-5, 11, 15-17, 25, 32, 33, 40, 44, 49, 52, 53, 57, 63, 67, 74, 75, 78, 79), 16 employed the rat (6,23,35,38,42,43,48,58,70,71,73,77,80,82,84,85) and one used the Brandt's vole (86) and the house shrew (69), respectively. Whenever possible, we compared both the regulatory effect of a given parameter across different studies and within the same study.…”