Effects of polyunsaturated fatty acids and clofibrate on chicken stearoyl-CoA desaturase 1 gene expression

In chicken, adiposity is influenced by hepatic stearoyl-CoA desaturase (SCD ) 1. This gene is upregulated by low-fat high-carbohydrate diet and down-re gulated by addition of polyunsaturated fatty acids (PUFA). In this study, w e present evidence for an inhibition of chicken SCD1 expression by PUFA usi ng reporter gene constructs in transient transfection assays. This inhibiti on does not involve the peroxisome proliferator-activated receptor pathway, in contrast with what has been observed in rodents. We were able to locali se a PUFA as well as an insulin response element within the -372/+125 bp re gion of the promoter. Sequence analyses of this region allowed identificati on of several cis-regulatory elements: A sterol regulatory element (SRE) an d a juxtaposed NF-Y element which have been shown to be involved in the reg ulation of mouse SCD genes by PUFA. In addition, we identified an overlappi ng Sp1/USF motif, which was described to play a role in insulin/glucose and PUFA regulation of fatty synthase, ATP-citrate-lyase, and leptin genes. Th ese data provide the first characterisation of the chicken SCD1 promoter an d putative cis-sequences involved in the regulation of this gene by PUFA an d insulin. (C) 2001 Academic Press.