Insulin resistant states are commonly associated with both increased circulating levels of tumor necrosis factor (TNF)- and hepatic overproduction of very low density lipoproteins (VLDL). Here, we provide evidence that increased TNF- can directly stimulate the hepatic assembly and secretion of apolipoprotein B (apoB) 100-containing VLDL1, using the Syrian golden hamster, an animal model that closely resembles humans in hepatic VLDL-apoB100 metabolism. In vivo TNF- infusion for 4 hours in chow-fed hamsters induced whole-body insulin resistance based on euglycemic hyperinsulinemic clamp studies. Immunoprecipitation and immunoblotting analysis of livers from TNF--treated hamsters indicated decreased tyrosine phosphorylation of insulin receptor (IR)-, IR substrate (IRS)-1 (Tyr), Akt (ser⁴⁷³), p38, ERK1/2, and JNK, but increased serine phosphorylation of IRS-1 (ser³⁰⁷) and Shc. TNF- infusion also significantly increased hepatic production of total circulating apoB100 and VLDL-apoB100 in both fasting and postprandial (fat load) states. Ex vivo experiments, using cultured primary hepatocytes from hamsters, also showed TNF--induced VLDL-apoB100 oversecretion, an effect that was blocked by TNF receptor 2 antibody. Unexpectedly, TNF- decreased the sterol regulatory element binding protein (SREBP)-1c mass and mRNA levels, but significantly increased microsomal triglyceride transfer protein (MTP) mass and mRNA levels in primary hepatocytes. In summary, these data provide direct evidence that TNF- induces whole-body insulin resistance and impairs hepatic insulin signaling accompanied by overproduction of apoB100-containing VLDL particles, an effect likely mediated via TNF receptor 2.