Dietary Fat Is a Lipid Source in 2,3,7,8-Tetrachlorodibenzo-ρ-Dioxin (TCDD)-Elicited Hepatic Steatosis in C57BL/6 Mice

2,3,7,8-Tetrachlorodibenzo-ρ-dioxin (TCDD) increases fatty acid (FA) transport and FA levels resulting in hepatic steatosis in mice. Diet as a source of lipids was investigated using customized diets, stearoyl-CoA desaturase 1 (Scd1) null mice, and 14C-oleate (18:1n9) uptake studies. C57BL/6 mice fed with 5, 10, or 15 % fat or 50, 60 or 70 % carbohydrate diets exhibited increased relative liver weight following gavage with 30 µg/kg TCDD for 168 h. He-patic lipid extract analysis from mice fed with 5, 10, and 15 % fat diets identified a dose-dependent increase in total FAs induced by TCDD. Mice fed with fat diet also exhibited a dose-dependent increase in the dietary essential linoleic (18:2n6) and α-linolenic (18:3n3) acids. No dose-dependent FA increase was detected on carbohydrate diets, suggesting dietary fat as a source of lipids in TCDD-induced steatosis as opposed to de novo lipogenesis. TCDD also induced oleate levels threefold in Scd1 null mice tha