Insulin signal transduction in skeletal muscle from glucose-intolerant relatives of type 2 diabetic patients [corrected].
To determine whether defects in the insulin signal transduction cascade are present in skeletal muscle from prediabetic individuals, we excised biopsies from eight glucose-intolerant male first-degree relatives of patients with type 2 diabetes (IGT relatives) and nine matched control subjects before and during a euglycemic-hyperinsulinemic clamp. IGT relatives were insulin-resistant in oxidative and nonoxidative pathways for glucose metabolism. In vivo insulin infusion increased skeletal muscle insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation (P = 0.01) and phosphatidylinositide 3-kinase (PI 3-kinase) activity (phosphotyrosine and IRS-1 associated) in control subjects (P < 0.02) but not in IGT relatives (NS). The incremental increase in insulin action on IRS-1 tyrosine phosphorylation was lower in IGT relatives versus control subjects (P < 0.05). The incremental defects in signal transduction noted for IRS-1 and PI 3-kinase may be attributed to elevated basal phosphorylation/activity of these parameters, because absolute phosphorylation/activity under insulin-stimulated conditions was similar between IGT relatives and control subjects. Insulin increased Akt serine phosphorylation in control subjects and IGT relatives, with a tendency for reduced phosphorylation in IGT relatives (P = 0.12). In conclusion, aberrant phosphorylation/activity of IRS-1, PI 3-kinase, and Akt is observed in skeletal muscle from relatives of patients with type 2 diabetes with IGT. However, the elevated basal activity of these signaling intermediates and the lack of a strong correlation between these parameters to glucose metabolism suggests that other defects of insulin signal transduction and/or downstream components of glucose metabolism may play a greater role in the development of insulin resistance in skeletal muscle from relatives of patients with type 2 diabetes.
Storgaard
H
H
Department of Endocrinology, Hvidovre Hospital and Clinical Trial Unit, University of Copenhagen, Copenhagen, Denmark.
Song
X M
XM
Jensen
C B
CB
Madsbad
S
S
Björnholm
M
M
Vaag
A
A
Zierath
J R
JR
D000328:Adult; D001706:Biopsy; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D015309:Glucose Clamp Technique; D018149:Glucose Intolerance / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D015227:Lipid Peroxidation; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction
D001786:Blood Glucose; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D019000:Phosphotyrosine; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C526292:IRS1 protein, human; C494918:AKT1 protein, human