Suppressor of cytokine signaling 3 is a physiological regulator of adipocyte insulin signaling.
Many proinflammatory cytokines and hormones have been demonstrated to be involved in insulin resistance. However, the molecular mechanisms whereby these cytokines and hormones inhibit insulin signaling are not completely understood. We observed that several cytokines and hormones that induce insulin resistance also stimulate SOCS3 expression in 3T3-L1 adipocytes and that SOCS3 mRNA is increased in adipose tissue of obese/diabetic mice. We then hypothesized that SOCS3 may mediate cytokine- and hormone-induced insulin resistance. By using SOCS3-deficient adipocytes differentiated from mouse embryonic fibroblasts, we found that SOCS3 deficiency increases insulin-stimulated IRS1 and IRS2 phosphorylation, IRS-associated phosphatidylinositol 3-kinase activity, and insulin-stimulated glucose uptake. Moreover, lack of SOCS3 substantially limits the inhibitory effects of tumor necrosis factor-alpha to suppress IRS1 and IRS2 tyrosine phosphorylation, phosphatidylinositol 3-kinase activity, and glucose uptake in adipocytes. The ameliorated insulin signaling in SOCS3-deficient adipocytes is mainly due to the suppression of tumor necrosis factor-alpha-induced IRS1 and IRS2 protein degradation. Therefore, our data suggest that endogenous SOCS3 expression is a key determinant of basal insulin signaling and is an important molecular mediator of cytokine-induced insulin resistance in adipocytes. We conclude that SOCS3 plays an important role in mediating insulin resistance and may be an excellent target for therapeutic intervention in insulin resistance and type II diabetes.
Shi
Hang
H
Division of Endocrinology, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA.
Tzameli
Iphigenia
I
Bjørbaek
Christian
C
Flier
Jeffrey S
JS
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D000821:Animal Feed; D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005838:Genotype; D005947:Glucose / Q000378:metabolism; D015151:Immunoblotting; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D016207:Cytokines; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526295:Irs1 protein, mouse; C526298:Irs2 protein, mouse; D010750:Phosphoproteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C491411:Socs3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D005947:Glucose