title: Skeletal muscle insulin resistance in normoglycemic subjects with a strong family history of type 2 diabetes is associated with decreased insulin-stimulated insulin receptor substrate-1 tyrosine phosphorylation.
abstract: Normoglycemic subjects with a strong family history of type 2 diabetes are insulin resistant, but the mechanism of insulin resistance in skeletal muscle of such individuals is unknown. The present study was undertaken to determine whether abnormalities in insulin-signaling events are present in normoglycemic, nonobese subjects with a strong family history of type 2 diabetes. Hyperinsulinemic-euglycemic clamps with percutaneous muscle biopsies were performed in eight normoglycemic relatives of type 2 diabetic patients (FH(+)) and eight control subjects who had no family history of diabetes (FH(-)), with each group matched for age, sex, body composition, and ethnicity. The FH(+) group had decreased insulin-stimulated glucose disposal (6.64 +/- 0.52 vs. 8.45 +/- 0.54 mg. kg(-1) fat-free mass. min(-1); P < 0.05 vs. FH(-)). In skeletal muscle, the FH(+) and FH(-) groups had equivalent insulin stimulation of insulin receptor tyrosine phosphorylation. In contrast, the FH(+) group had decreased insulin stimulation of insulin receptor substrate (IRS)-1 tyrosine phosphorylation (0.522 +/- 0.077 vs. 1.328 +/- 0.115 density units; P < 0.01) and association of PI 3-kinase activity with IRS-1 (0.299 +/- 0.053 vs. 0.466 +/- 0.098 activity units; P < 0.05). PI 3-kinase activity was correlated with the glucose disposal rate (r = 0.567, P = 0.02). In five subjects with sufficient biopsy material for further study, phosphorylation of Akt was 0.266 +/- 0.061 vs. 0.404 +/- 0.078 density units (P < 0.10) and glycogen synthase activity was 0.31 +/- 0.06 vs. 0.50 +/- 0.12 ng. min(-1). mg(-1) (P < 0.10) for FH(+) and FH(-) subjects, respectively. Therefore, despite normal insulin receptor phosphorylation, postreceptor signaling was reduced and was correlated with glucose disposal in muscle of individuals with a strong genetic background for type 2 diabetes.
authors.affiliation: Department of Medicine, Diabetes Division, University of Texas Health Science Center at San Antonio, 78229-3900, USA.
authors.forename: W
authors.initials: W
authors.lastname: Pratipanawatr
authors.forename: T
authors.initials: T
authors.lastname: Pratipanawatr
authors.forename: K
authors.initials: K
authors.lastname: Cusi
authors.forename: R
authors.initials: R
authors.lastname: Berria
authors.forename: J M
authors.initials: JM
authors.lastname: Adams
authors.forename: C P
authors.initials: CP
authors.lastname: Jenkinson
authors.forename: K
authors.initials: K
authors.lastname: Maezono
authors.forename: R A
authors.initials: RA
authors.lastname: DeFronzo
authors.forename: L J
authors.initials: LJ
authors.lastname: Mandarino
mesh_terms: D000328:Adult; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D005260:Female; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000494:pharmacology / Q000502:physiology*; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D008499:Medical Records; D018482:Muscle, Skeletal / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011972:Receptor, Insulin / Q000502:physiology; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism*
chemical_list: C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins; D014443:Tyrosine; D011972:Receptor, Insulin