Brown and white adipose tissue metabolism in cold-exposed rats

Abstract
Brown and white adipose tissue from rats exposed to 5 C for 9 days has been studied with reference to its composition and handling of glucose-U-C14 in vivo and in vitro. Brown adipose tissue from cold-exposed rats demonstrated a decreased lipid content per milligram nitrogen, due mainly to decreased amounts of neutral lipid with little change in phospholipid. The incorporation of glucose into neutral lipids, glyceride glycerol, and fatty acids was increased in vivo and in vitro. There was increased incorporation into CO2 in vitro and there was no change in glucose conversion to phospholipid in vivo. No changes in any of these were noted in epididymal fat pads. These findings suggest that cold exposure leads to alterations in carbohydrate metabolism and lipogenesis in brown adipose tissue but not in epididymal fat pads. The possible role in thermogenesis is discussed.