Lipogenesis in response to an oral glucose load in fed and starved rats.

Lipogenesis in livers of fed but not of starved rats is increased after intragastric feeding with glucose. In contrast, lipogenesis in brown adipose tissue increases in both fed and starved animals. These observations suggest that lipogenesis in brown adipose tissue is regulated by mechanisms in addition to, or other than, those operating in liver. The fate of newly synthesized lipid in brown adipose tissue is not known. However, the formation of palmitoyl-carnitine from palmitoyl-CoA and carnitine by mitochondria from brown fat was inhibited by malonyl-CoA. Although inhibition was not 100%, it is implied that mitochondrial uptake of the newly synthesized fat by the carnitine acyltransferase system is restricted under conditions of increased lipogenesis.