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Antisense oligonucleotides against the lipid phosphatase SHIP2 improve muscle insulin sensitivity in a dietary rat model of the metabolic syndrome

Department of Internal Medicine I, University of Regensburg, Regensburg, Germany

Submitted 31 May 2006 ; accepted in final form 19 February 2007

The lipid phosphatase SH₂ domain-containing lipid phosphatase (SHIP2) has been implicated in the regulation of insulin sensitivity, but its role in the therapy of insulin-resistant states remains to be defined. Here, we examined the effects of an antisense oligonucleotide (AS) therapy directed against SHIP2 on whole body insulin sensitivity and insulin action in liver and muscle tissue in a dietary rodent model of the metabolic syndrome, the high-fat-fed (HF) rat. Whole body insulin sensitivity was examined in vivo by insulin tolerance tests before and after the intraperitoneal application of an AS directed against SHIP2 (HF-SHIP2-AS) or a control AS (HF-Con-AS) in HF rats. Insulin action in liver and muscle was assayed by measuring the activation of protein kinase B (Akt) and insulin receptor substrate (IRS)-1/2 after a portal venous insulin bolus. SHIP2 mRNA and protein content were quantified in these tissues by real-time PCR and immunoblotting, respectively. In HF-SHIP2-AS, whole body glucose disposal after an insulin bolus was markedly elevated compared with HF-Con-AS. In liver, insulin activated Akt similarly in both groups. In muscle, insulin did not clearly activate Akt in HF-Con-AS animals, whereas insulin-induced Akt phosphorylation was sustained in SHIP2-AS-treated rats. IRS-1/2 activation did not differ between the experimental groups. SHIP2 mRNA and protein content were markedly reduced only in muscle. In standard diet-fed controls, SHIP2-AS reduced SHIP2 protein levels in liver and muscle, but it had no significant effect on insulin sensitivity. We conclude that treatment with SHIP2-AS can rapidly improve muscle insulin sensitivity in dietary insulin resistance. The long-term feasability of such a strategy should be examined further.

insulin resistance; obesity; high-fat diet; antisense oligonucleotide therapy; SH₂ domain-containing lipid phosphatase