Short term changes in the expression of lipogenic genes in broilers (Gallus gallus).

The purpose of these experiments were to determine possible relationships between certain indices of lipid metabolism and specific gene expression in chickens fed graded levels of dietary crude protein. Male, broiler chickens growing from 7 to 28 days of age were fed diets containing 12 or 30% protein ad libitum. Both groups were then switched on day 28 to the diets containing the opposite level of protein. Birds were killed on day 28 (basal values prior to the switch) and at 12, 18 and 24 h post switch. Measurements taken included in vitro lipogenesis, malic enzyme activity the expression of the genes for malic enzyme, fatty acid synthase and acetyl coenzyme carboxylase. In vitro lipogenesis and malic enzyme activity were inversely related to dietary protein levels (12 to 30%) and to acute changes from 12 to 30%. Malic enzyme, fatty acid synthase and acetyl coenzyme A carboxylase genes were constant over a dietary protein range of 12 to 21% as in previous experiments, but decreased by feeding a 30% protein diet in the present experiments (acute or chronic feeding). Results of the present study demonstrate a continued role for protein in the regulation of broiler metabolism. Metabolic regulation at the gene level only occurs when feeding very high levels of dietary protein.