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1 Department of Biochemistry, University of Wisconsin, Madison, WI, USA
2 Department of Biochemistry, University of Wisconsin, Madison, WI, USA; Department of Nutritional Sciences, University of Wisconsin, Madison, WI, USA
* To whom correspondence should be addressed. E-mail: ntambi{at}biochem.wisc.edu.
Stearoyl-CoA desaturase (SCD) catalyzes the synthesis of oleate (C18:1) and
palmitoleate (C16:1) which are the main monounsaturated fatty acids of membrane
phospholipids (PL), triglycerides (TG), wax esters and cholesterol esters. Previously, we
showed SCD1 deficiency elevates insulin signaling components and downregulates
protein-tyrosine phosphatase 1B in muscle a major insulin sensitive tissue. Here we
found that in the brown adipose tissue another insulin sensitive tissue, the basal tyrosine
phosphorylation of the insulin receptor (IR), and insulin receptor substrates (IRS-1 and
IRS-2) were upregulated in SCD1-/- mice compared to the wild-type mice. The
association of IRS-1 and IRS-2 with 
p85 subunit of phosphatidylinositol 3-kinase as
well as the Akt-Ser 473 and Akt-Thr 308 phosphorylation are also elevated in the SCD1-
/- mice. The mRNA expression, protein levels, and activity of the protein-tyrosine
phosphatase-1B (PTP-1B) implicated in the attenuation of the insulin signal, are reduced
in the SCD1-/- mice. The content of glucose transporter 4 in the plasma membrane
increased 2.5 fold and this was accompanied by a 6-fold increase in glucose uptake in
BAT of SCD1-/- mice. The increased glucose uptake was associated with higher
glycogen synthase activity and glycogen accumulation. In presence of insulin, [U-
14C]glucose incorporation into glycogen was increased in BAT of SCD1-/- mice. Taken
together, these studies illustrate increased insulin signaling and increased glycogen
metabolism in BAT of SCD1-/- mice.
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