ALTERATIONS IN NUTRITIONAL-STATUS REGULATE ACETYL-COA CARBOXYLASE EXPRESSION IN AVIAN LIVER BY A TRANSCRIPTIONAL MECHANISM

Feeding previously starved chicks with a high-carbohydrate, low-fat di et stimulates a 9-fold increase in both the rate of synthesis of acety l-CoA carboxylase (ACC) and the abundance of its mRNA in liver. To def ine the steps involved in mediating diet-induced changes in the abunda nce of ACC mRNA, transcriptional activity was measured with the nuclea r run-on assay and multiple DNA probes specific to the ACC gene. ACC t ranscription was low in livers of starved chicks; feeding them with a high-carbohydrate, low-fat diet induced ACC transcription, increasing it 11-fold. An increase in transcription was detectable at 1 h, was ma ximal at 5 h and remained high for 26 h. Feeding previously starved ch icks with a low-carbohydrate, high-fat diet stimulated a smaller incre ase (4-fold) in the abundance of ACC mRNA and the transcription of ACC than feeding with a high-carbohydrate, low-fat diet. The half-life of ACC mRNA in liver, as estimated from the kinetics of accumulation and decay of ACC mRNA during high-carbohydrate feeding and starvation, wa s not changed significantly by dietary manipulation. ACC mRNA was expr essed at low levels in heart, pectoral muscle, kidney and brain. The a bundance of ACC mRNA in these tissues was not affected by nutritional manipulation. These results demonstrate that nutritional control of th e abundance of ACC mRNA in the chicken is liver-specific and is mediat ed primarily by changes in the rate of transcription of the ACC gene.