Hormonal regulation of stearoyl coenzyme-A desaturase 1 activity and gene expression in primary cultures of chicken hepatocytes

Previous studies have provided evidence for the important role of liver ste aroyl-CoA desaturase (SCD) in excessive adiposity in the chicken and sugges t that the difference in SCD activity between fat and lean chickens could b e explained by a difference in SCD1 gene expression, In the present study, the regulation of SCD1 gene expression was analyzed as the result of insuli n and glucagon action, using primary cultures of 6-week-old chicken hepatoc ytes, Insulin increased SCD1 activity and mRNA levels, whereas glucagon dec reased dramatically both the enzyme activity and the mRNA levels. Nuclear r un-on transcription assays and mRNA stability investigations demonstrated t hat insulin and glucagon effects on SCD1 gene expression was primarily tran scriptional. Furthermore, the results indicated that the glucagon-mediated inhibition of SCD1 gene transcription was more potent than just counteracti ng the insulin-mediated effect. These data represent the first demonstratio n that the glucagon effect on the SCD1 gene expression is primarily transcr iptional. Moreover, among hepatic genes involved in lipid metabolism in chi cken, SCD1 is the first gene shown to be regulated at the transcriptional l evel by insulin, in the absence of triiodothyronine. These data point out t he potency of the growing chicken hepatocyte culture model in contrast with the embryonic cell culture model as regards the investigations of the insu lin effect on gene expression, (C) 1999 Academic Press.