In vivo effects of glucagon on fatty acid synthesis in fasted and refed rats.

Since altered nutritional states evoke compensatory changes in systemic levels of several hormones, the present study was conducted to determine in vivo effects of glucagon and insulin on hepatic and adipose tissue lipogenesis in fed, fasted (3-days) and refed (3-days) rats. Compared to the fed controls, glucagon reduced hepatic fatty acid synthesis and acetyl CoA carboxylase activity by 62% and 65% in fed rats, and by 51% and 48%, respectively, in refed rats. In contrast, glucagon had no effect on fatty acid synthesis or acetyl CoA carboxylase activity in adipose tissue of any of the three experimental groups. Exogenous insulin antagonized the glucagon effects and restored hepatic fatty acid synthesis and enzyme activity in fed or refed rats. No glucagon or insulin effects were observed in fasting rats. In addition, glucagon reduced in vivo incorporation of acetate into hepatic cholesterol by about 33% and into fatty acids of the liver, and heart and the kidney by 33%, 77% and 30%, respectively. The hormone had no effect on fatty acid synthesis in the muscle.