The trans-10,cis-12 isomer of conjugated linoleic acid downregulates stearoyl-CoA desaturase 1 gene expression in 3T3-L1 adipocytes

Conjugated linoleic acids (CL4) are a group of positional and geometric con jugated dienoic isomers of linoleic acid. The objective of this study was t o determine the effects of the cis-9,trans-11 and trans-10,cis-12 isomers o f conjugated linoleic acid on lipid composition and gene expression during the differentiation of mouse 3T3-L1 preadipocytes. Treatment of differentia ting 3T3-L1 preadipocytes with trans-10,cis-12 conjugated linoleic acid (CL A) resulted in a dose-dependent decrease in the expression of the stearoyl- Coa desaturase 1 gene (SCD1). The expression of other adipocyte genes such as adipose P2 (aP2), fatty acid synthase (FAS), SCD2 and the key adipogenic transcription factors, peroxisome proliferator-activated receptor gamma 2 (PPAR gamma 2) and CCAAT enhancer binding protein alpha (C/EBP alpha), rema ined elevated. Cells treated with trans-10,cis-12 CLA exhibited smaller lip id droplets, with reduced levels of the major monounsaturated fatty acids, palmitoleate and oleate. By contrast, the cis-9,trans-11 isomer did not alt er adipocyte gene expression. Repression of the stearoyl-CoA desaturase gen e expression in adipocytes by the trans-10,cis-12 somer may contribute to t he mechanisms by which CLA reduces body fat in mice.