Severe impairment in liver insulin signaling fails to alter hepatic insulin action in conscious mice
Christoph Buettner, … , Silvana Obici, Luciano Rossetti
Christoph Buettner, … , Silvana Obici, Luciano Rossetti
Published May 2, 2005
Citation Information: J Clin Invest. 2005;115(5):1306-1313. https://doi.org/10.1172/JCI23109.
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Article Metabolism

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

Abstract

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.

Authors

Christoph Buettner, Rima Patel, Evan D. Muse, Sanjay Bhanot, Brett P. Monia, Rob McKay, Silvana Obici, Luciano Rossetti

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Figure 1

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Treatment with IR-ASO decreases liver IR protein levels in mice. (A) Pro...
Treatment with IR-ASO decreases liver IR protein levels in mice. (A) Protocol of ASO treatment in mice. Mice received i.p. injections of either IR-ASO or control-ASO on days 1 and 4 (7 and 3 days prior to the insulin clamp/insulin signaling studies, respectively). Catheters were inserted in the jugular vein 3 days prior to the clamp studies. (B) IR protein expression in livers of animals treated with IR-ASO or scrambled control-ASO (con-ASO). Livers from mice treated with a low dose (50 mg/kg body weight) of ASO (left panel) or with a high dose (100 mg/kg body weight) of ASO (right panel) were analyzed by Western blot with antiserum against IR. Membranes were stripped and reprobed with antiserum against β-actin for normalization purposes. Note protein dilutions of 1:4 and 1:10 of liver extracts from rats treated with scrambled ASO (last 2 samples on the right) were used for quantification purposes. IR protein is virtually undetectable in IR-ASO–treated mice, whereas a dilution of 1:10 in the control livers still shows a clearly detectable band. Thus, we estimate that the IR protein is downregulated by more than 95% in liver of IR-ASO rats. (C) IR expression in kidney and testis fat. We used the same dilution method as described for B. Samples were derived from the same animals in the same order as for the liver samples in Figure 1B, right panel. (D) Muscle and hypothalamus IR expression were not affected by treatment with IR-ASO.