Desaturation indices in liver, muscle, and bone of growing male and female mice fed trans-10,cis-12 conjugated linoleic acid.

trans-10,cis-12-CLA (t10,c12-CLA) inhibits lipid deposition in adipose tissue of many species, but it also enhances lipid deposition in liver. We evaluated effects of dietary t10,c12-CLA content and gender on carcass composition, FA profile of selected tissues, and expression of FA synthase (FAS) and stearoyl-CoA desaturase-1 (SCD) mRNA in adipose tissue. Male and female (63 of each) CD-1 mice were assigned a diet containing 0.0, 0.15, or 0.30% t10,c12-CLA at 4 wk of age. Seven mice per dietary group within gender were sacrificed after 2, 4, or 6 wk. The CLA isomer caused dose-dependent reductions in dry carcass weight and fat content, without altering protein content, but carcass fat and epididymal fat pad weights of males were reduced to a greater extent than carcass fat and inguinal fat pad weights of females. FAS and SCD mRNA in adipose tissue was more abundant in females than males, but expression in both genders decreased as the t10,c12-CLA content of the diet increased. Although the weight of gastrocnemius muscle was not influenced by diet, total FA content of the muscle of both genders decreased in response to dietary t10,c12-CLA content. Femur weight of male mice increased as the t10,c12-CLA content of the diet increased, but the weight increase was associated with a reduction in total FA content. The delta 9 desaturation indices for muscle and femur suggested a linear reduction in SCD activity, whereas delta 9 indices for liver indicated linear enhancement of SCD activity. Overall, results suggested that growing male mice were more susceptible than females to t10,c12-CLA inhibition of lipid deposition.