title: Muscle damage impairs insulin stimulation of IRS-1, PI 3-kinase, and Akt-kinase in human skeletal muscle.
abstract: Physiological stress associated with muscle damage results in systemic insulin resistance. However, the mechanisms responsible for the insulin resistance are not known; therefore, the present study was conducted to elucidate the molecular mechanisms associated with insulin resistance after muscle damage. Muscle biopsies were obtained before (base) and at 1 h during a hyperinsulinemic-euglycemic clamp (40 mU x kg(-1) x min(-1)) in eight young (age 24+/-1 yr) healthy sedentary (maximal O(2) consumption, 49.7+/-2.4 ml x kg(-1) x min(-1)) males before and 24 h after eccentric exercise (ECC)-induced muscle damage. To determine the role of cytokines in ECC-induced insulin resistance, venous blood samples were obtained before (control) and 24 h after ECC to evaluate ex vivo endotoxin-induced mononuclear cell secretion of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-1beta. Glucose disposal was 19% lower after ECC (P<0.05). Insulin-stimulated insulin receptor substrate (IRS)-1 tyrosine phosphorylation was 45% lower after ECC (P<0.05). Insulin-stimulated phosphatidylinositol (PI) 3-kinase, Akt (protein kinase B) serine phosphorylation, and Akt activity were reduced 34, 65, and 20%, respectively, after ECC (P < 0.05). TNF-alpha, but not IL-6 or IL-1beta production, increased 2.4-fold 24 h after ECC (P<0.05). TNF-alpha production was positively correlated with reduced insulin action on PI 3-kinase (r = 0.77, P = 0.04). In summary, the physiological stress associated with muscle damage impairs insulin stimulation of IRS-1, PI 3-kinase, and Akt-kinase, presumably leading to decreased insulin-mediated glucose uptake. Although more research is needed on the potential role for TNF-alpha inhibition of insulin action, elevated TNF-alpha production after muscle damage may impair insulin signal transduction.
authors.affiliation: Noll Physiological Research Center, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: L F
authors.initials: LF
authors.lastname: Del Aguila
authors.forename: R K
authors.initials: RK
authors.lastname: Krishnan
authors.forename: J S
authors.initials: JS
authors.lastname: Ulbrecht
authors.forename: P A
authors.initials: PA
authors.lastname: Farrell
authors.forename: P H
authors.initials: PH
authors.lastname: Correll
authors.forename: C H
authors.initials: CH
authors.lastname: Lang
authors.forename: J R
authors.initials: JR
authors.lastname: Zierath
authors.forename: J P
authors.initials: JP
authors.lastname: Kirwan
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D016207:Cytokines / Q000096:biosynthesis; D015444:Exercise; D005215:Fasting / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood / Q000502:physiology*; D055504:Insulin Receptor Substrate Proteins; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000502:physiology
chemical_list: D001786:Blood Glucose; D016207:Cytokines; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C526292:IRS1 protein, human; C494918:AKT1 protein, human