Increased insulin action in SKIP heterozygous knockout mice.
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.
Ijuin
Takeshi
T
Division of Lipid Biochemistry, Kobe University Graduate School of Medicine, Kobe 650-0017, Hyogo, Japan.
Yu
Y Eugene
YE
Mizutani
Kiyohito
K
Pao
Annie
A
Tateya
Sanshiro
S
Tamori
Yoshikazu
Y
Bradley
Allan
A
Takenawa
Tadaomi
T
D050154:Adiposity / Q000187:drug effects; D000483:Alleles; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002460:Cell Line; D004032:Diet; D005247:Feeding Behavior / Q000187:drug effects; D018390:Gene Targeting; D005854:Germ Cells / Q000187:drug effects / Q000201:enzymology; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D006579:Heterozygote; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology; D010641:Phenotype; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects
D007328:Insulin; C531212:Pps protein, mouse; D010744:Phosphoric Monoester Hydrolases; D005947:Glucose