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Molecular and Cellular Biology, September 2008, p. 5184-5195, Vol. 28, No. 17
0270-7306/08/$08.00+0     doi:10.1128/MCB.01990-06
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Increased Insulin Action in SKIP Heterozygous Knockout Mice ^,

Takeshi Ijuin,^1, Y. Eugene Yu,^2,3, Kiyohito Mizutani,⁶ Annie Pao,² Sanshiro Tateya,⁴ Yoshikazu Tamori,⁴ Allan Bradley,⁵ and Tadaomi Takenawa^1*

Division of Lipid Biochemistry, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan,¹ Department of Cancer Genetics and Genetics Program, Roswell Park Cancer Institute, Buffalo, New York,² New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, New York,³ Division of Diabetes, Metabolism and Endocrinology, Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan,⁴ Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom,⁵ Neurobiology of Disease Laboratory, Genetics and Aging Research Unit, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts⁶

Received 24 October 2006/ Returned for modification 22 January 2007/ Accepted 27 May 2008

Insulin controls glucose homeostasis and lipid metabolism, and insulin impairment plays a critical role in the pathogenesis of diabetes mellitus. Human skeletal muscle and kidney enriched inositol polyphosphate phosphatase (SKIP) is a member of the phosphatidylinositol 3,4,5-trisphosphate phosphatase family (T. Ijuin et al. J. Biol. Chem. 275:10870-10875, 2000; T. Ijuin and T. Takenawa, Mol. Cell. Biol. 23:1209-1220, 2003). Previous studies showed that SKIP negatively regulates insulin-induced phosphatidylinositol 3-kinase signaling (Ijuin and Takenawa, Mol. Cell. Biol. 23:1209-1220, 2003). We now have generated mice with a targeted mutation of the mouse ortholog of the human SKIP gene, Pps. Adult heterozygous Pps mutant mice show increased insulin sensitivity and reduced diet-induced obesity with increased Akt/protein kinase B (PKB) phosphorylation in skeletal muscle but not in adipose tissue. The insulin-induced uptake of 2-deoxyglucose into the isolated soleus muscle was significantly enhanced in Pps mutant mice. A hyperinsulinemic-euglycemic clamp study also revealed a significant increase in the rate of systemic glucose disposal in Pps mutant mice without any abnormalities in hepatic glucose production. Furthermore, in vitro knockdown studies in L6 myoblast cells revealed that reduction of SKIP expression level increased insulin-stimulated Akt/PKB phosphorylation and 2-deoxyglucose uptake. These results imply that SKIP regulates insulin signaling in skeletal muscle. Thus, SKIP may be a promising pharmacologic target for the treatment of insulin resistance and diabetes.

Published ahead of print on 23 June 2008.

Supplemental material for this article may be found at http://mcb.asm.org/.

T.I. and Y.E.Y. contributed equally to this work.