Long-term denervation impairs insulin receptor substrate-1-mediated insulin signaling in skeletal muscle.
Long-term denervation is associated with insulin resistance. To investigate the molecular bases of insulin resistance, the downstream signaling molecules of insulin receptor including insulin receptor substrate-1 (IRS-1) and phosphatidylinositol 3-kinase (PI 3-K) were examined in skeletal muscle of rats after 7 days of denervation. Long-term denervation attenuated insulin-stimulated activation of the initial steps of the intracellular signaling pathway. Insulin-stimulated tyrosine phosphorylation of insulin receptor was reduced to 36% (P < .005), as was the phosphorylation of IRS-1 to 34% (P < .0001) of control. While insulin receptor protein level was unchanged, the protein expression of IRS-1 was significantly decreased in denervated muscles. Insulin-stimulated percent tyrosine phosphorylation of IRS-1, normalized to the IRS-1 protein expression, was also reduced to 55% (P < .01) of control in denervated muscle. Denervation caused a decline in the insulin-induced binding of p85 regulatory subunit of PI 3-K to IRS-1 to 61% (P < .001) and IRS-1-associated PI 3-K activity to 57% (P < .01). These results provide evidence that long-term denervation results in insulin resistance because of derangements at multiple points, including tyrosine phosphorylation of insulin receptor and its downstream signaling molecule, IRS-1, protein expression of IRS-1, and activation of PI 3-K.
Hirose
M
M
Department of Anesthesia and Critical Care, Harvard Medical School, Boston, MA, USA.
Kaneki
M
M
Sugita
H
H
Yasuhara
S
S
Ibebunjo
C
C
Martyn
J A
JA
Iebunjo
C
C
D000818:Animals; D003714:Denervation / Q000009:adverse effects* / Q000379:methods; D004789:Enzyme Activation / Q000187:drug effects; D006614:Hindlimb; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000294:innervation* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021122:Protein Subunits; D051381:Rats; D017207:Rats, Sprague-Dawley; D011972:Receptor, Insulin / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors
D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D010750:Phosphoproteins; D021122:Protein Subunits; D019000:Phosphotyrosine; D019869:Phosphatidylinositol 3-Kinases; D011972:Receptor, Insulin