Effect of epinephrine deficiency on cold tolerance and on brown adipose tissue

Catecholamines are involved in thermogenesis. We investigated the specific role of epinephrine in regulation of temperature homeostasis in mice. We subjected adult wildtype (WT) and phenylethanolamine N-methyl transferase knock out mice (Pnmt^-/-) lacking epinephrine to cold for 24h. Body temperature and thyroid hormone levels were not different between WT and Pnmt^-/- mice. Although temperature was normal in Pnmt^-/- mice, the brown fat response to cold was abnormal with no increase in Ucp-1 or Pgc-1α mRNA levels (but with an exaggerated cold-induced lipid loss from the tissue). Our results show that epinephrine may have a role in brown fat mitochondrial uncoupling through regulation of Ucp-1 and Pgc-1α, although this is not required to maintain a normal temperature during acute cold exposure. We conclude that epinephrine may have an important role in induction of Ucp-1 and Pgc-1α gene expression during cold stress.