Severe impairment in liver insulin signaling fails to alter hepatic insulin action in conscious mice.

Insulin exerts its potent effects on hepatic glucose fluxes via direct and indirect mechanisms. Whereas a liver-specific insulin receptor (IR) knockout (LIRKO) mouse exhibits glucose intolerance as well as insulin resistance, it is unclear whether a more acute decrease in the expression of hepatic IR would be sufficient to induce hepatic insulin resistance. Here we report that the downregulation of hepatic IR expression by up to 95% does not modify hepatic insulin action. The i.p. administration (2 injections over 1 week) of an antisense oligodeoxynucleotide (ASO) directed to reduce insulin expression downregulated hepatic IR expression in C57BL6J mice. A high dose of IR-ASO decreased IR protein approximately 95%, while a control-ASO failed to modify IR expression. At this dose, the IR-ASO also decreased IR expression in adipose tissue but did not significantly decrease IR expression in hypothalamus or skeletal muscle. Insulin action was assessed with insulin clamp studies in conscious mice. The rate of glucose infusion during the clamp studies was comparable in control-ASO- and IR-ASO-treated mice. Importantly, the depletion of liver IR protein markedly impaired downstream insulin signaling in the liver, but it failed to modify the rate of glucose production. Thus, near ablation of liver IR does not alter insulin action on glucose production.

Antisense oligonucleotides to poly(ADP-ribose) polymerase-2 ameliorate colitis in interleukin-10-deficient mice.

poly(ADP-ribose) polymerase-2 (PARP-2) is a newly described member of the PARP family of nuclear enzymes. Previous studies have shown pharmacological inhibition of PARP activity to have a beneficial role in attenuating inflammation. We developed a chemically modified 2'-O-(2-methoxy)ethyl antisense oligonucleotide (ISIS 110251) inhibitor of PARP-2 and tested it for efficacy in the interleukin (IL)-10-deficient mouse. In tissue culture, ISIS 110251 reduced PARP-2 mRNA expression in a concentration- and sequence-specific manner. In 129 Sv/Ev mice, ISIS 110251 reduced PARP-2 mRNA in liver by 80%. This reduction was dependent upon treatment duration and was independent of the method of delivery. In interleukin-10-deficient mice with established colitis, treatment with ISIS 110251 normalized colonic epithelial barrier and transport function, reduced proinflammatory cytokine secretion and inducible nitric-oxide synthase activity, and attenuated inflammation. Our data demonstrate that selective inhibition of PARP-2 activity results in a marked improvement of colonic inflammatory disease in a mouse model of chronic colitis and a normalization of colonic function.