DEPRESSION OF LIPOGENESIS IN SWINE ADIPOSE-TISSUE BY SPECIFIC DIETARYFATTY-ACIDS

y The objective of this study was to document the influence of specifi c dietary fatty acids on rates of lipid synthesis and sensitivity to i nsulin in porcine adipose tissue. Weanling pigs were assigned to one o f six groups, and each group was fed diets containing 10 g/100 g of ad ded cornstarch or 10 g/100 g of added fatty acid. The fatty acid-enric hed diets contained either a combination of 14:1 plus 16:1 (14:1/16:1 diet), 16:0, 18:0, 18:1, or 18:2 (n-6). With the exception of the corn starch diet, all diets contained approximately 35% 14:0. Subcutaneous adipose tissue samples were collected at slaughter from the area overl ying the first cranial vertebra. Fresh samples were incubated for 2 h in 20 mM glucose and 0, 10, 100 or 1,000 mu U/mL of porcine insulin. T he smallest adipocytes were observed in adipose tissue from pigs fed t he 16:0 or 18:2 diets. Glucose incorporation into lipids was greater ( P <.05) in adipose tissue from cornstarch-fed pigs than in adipose tis sue from the other treatment groups. Lipogenesis was 67, 53, 35, 32, a nd 20% lower (P <.05) in adipose tissue from 16: 0-, 14:1/16:1-, 18:0- , 18:2-, and 18:1-fed pigs, respectively, than in adipose tissue from the cornstarch-fed pigs. Insulin increased lipogenesis by 19% (P <.05) in adipose tissue from the cornstarch-fed pigs and by 15 to 40% (P <. 05) in adipose tissue from the 14:1/16:1-fed pigs. Insulin did not sti mulate lipogenesis (P >.4) in adipose tissue from pigs fed the 16:0, 1 8:0, or 18:1 diets. The data suggest that fatty acid chain length and unsaturation are determinants in the effects of dietary fat and insuli n on de novo lipogenesis.