Activation of Protein Kinase C-ζ by Insulin and Phosphatidylinositol-3,4,5-(PO4)3 Is Defective in Muscle in Type 2 Diabetes and Impaired Glucose Tolerance
Amelioration by Rosiglitazone and Exercise
Article Figures & Tables
Figures
- FIG. 1.
Effects of insulin administration in vivo (A), PIP3 treatment in vitro (B), and acute exercise (C) on PKC-ζ/λ/ι activity in vastus lateralis muscles of control nondiabetic patients and in patients who have IGT or type 2 diabetes. A: Insulin was administered during the clamp procedure. B: PIP3 (10 μmol/l) was added to assays of equal amounts of aPKCs immunoprecipitated from basal/unstimulated muscle lysates of nondiabetic control subjects and patients with IGT/diabetic patients (results of one patient with IGT and five diabetic patients were comparable and therefore combined). C: Nondiabetic and diabetic patients were subjected to 20 min bicycle exercise. Clear bars reflect basal/unstimulated values; shaded bars reflect stimulated values. Values are means ± SE of the number of patients shown in parentheses. P values were determined by ANOVA.
- FIG. 2.
Effects of insulin administration on IRS-1-dependent PI 3-kinase activity (A), PKB-α enzyme activity (B), and phosphorylation of serine-473 in PKB (C and D) in vastus lateralis muscles of control nondiabetic patients and in patients who have IGT or type 2 diabetes. Insulin was administered during the clamp procedure, and muscle samples were the same as those used in Fig. 1. Clear bars reflect basal/unstimulated values; shaded bars reflect stimulated values. Values are means ± SE of the number of patients shown in parentheses. P values were determined by ANOVA. Note that there was little or no measurable PKB phosphorylation in the absence of insulin treatment, as shown in D (which shows representative immunoblots).
- FIG. 3.
Western analyses of IRS-1, p85 PI 3-kinase, PDK-1, PKC-ζ, combined PKC-ζ/λ/ι, PKC-λ/ι, PKB-α, and GLUT4 glucose transporters in muscles of nondiabetic control subjects (ND or N), patients with IGT, type 2 diabetic patients (DM or D), and type 2 diabetic patients treated with rosiglitazone (RSGZ). Note that comparisons were made between samples of nondiabetic control subjects versus patients with IGT or diabetic patients, or diabetic patients before and after rosiglitazone (RSGZ) treatment, as analyzed on the same immunoblot (note that there are different degrees of chemiluminescence development on different blots, as it is necessary to make comparisons within the same blot). Top: Representative immunoblot comparisons. Bottom: Bar graphs depicting relative means ± SE values of multiple (the number of patients examined is shown in parentheses) immunoblot analyses of insulin-sensitive signaling factors, with nondiabetic values set at 100%. Asterisks indicate P values, as determined by ANOVA.
- FIG. 4.
Effects of rosiglitazone (RSGZ) on insulin-stimulated total-body glucose disposal rates (A), and insulin-stimulated activities of IRS-1-dependent PI 3-kinase (B), PKC-ζ/λ/ι (C), and PKB (D) in vastus lateralis muscle during clamp studies in diabetic patients. Values are means ± SE of the number of patient studies, which is shown in parentheses. P values were determined by ANOVA in A and D and by paired t test in B. For comparison, data from untreated nondiabetic control subjects are included in the figure.
- FIG. 5.
Effects of rosiglitazone (RSGZ) on insulin-stimulated total-body glucose disposal rates (A), and insulin-stimulated activities of IRS-1-dependent PI 3-kinase (B), PKC-ζ/λ/ι (C), and PKB (D) in vastus lateralis muscle during clamp studies in diabetic patients. Shown are findings in individual patients (see Fig. 4 for mean values).
Tables
- TABLE 1
Patient characteristics
Nondiabetic control subjects Subjects with IGT Type 2 Diabetic patients Age (years) 44 ± 2 (18) 43 ± 3 (6) 50 ± 3 (10) BMI 27 ± 1 (18) 34 ± 2 (6) 32 ± 2 (10) P < 0.004 P < 0.03 Fasting plasma glucose (mmol/l) 5.1 ± 0.2 (18) 6.2 ± 0.1 (6) 8.7 ± 1.4 (10) P < 0.001 Serum insulin (pmol) 111 ± 16 (17) 346 ± 124 (6) 235 ± 43 (10) P < 0.004 P < 0.05 Serum C-peptide (ng/ml) 1.46 ± 0.17 (17) 3.63 ± 0.97 (6) 2.63 ± 0.34 (10) P < 0.001 P < 0.03 HbA1c (%) 4.79 ± 0.13 (18) 5.42 ± 0.25 (6) 7.00 ± 0.71 (10) P < 0.0003 Triglycerides (mg/dl) 141 ± 16 (18) 209 ± 39 (6) 209 ± 36 (10) Systolic blood pressure (mmHg) 127 ± 3 (18) 136 ± 76 (6) 139 ± 6 (10) Diastolic blood pressure (mmHg) 76 ± 2 (18) 82 ± 3 (6) 85 ± 2 (10) P < 0.02 Serum free fatty acids (mmol) 0.44 ± 0.03 (17) 0.52 ± 0.08 (4) 0.51 ± 0.04 (10) Glucose disposal rate (mg · kg−1 · min−1) 11.60 ± 1.11 (18) 5.92 ± 1.01 (6) 4.90 ± 0.74 (10) P < 0.004 P < 0.0001 Data are means ± SE (number of determinations). P values versus normal nondiabetic control subjects, by ANOVA.
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