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Insulin stimulation of glycogen synthase activity in cultured human fibroblasts from diabetic and control subjects


The influence of insulin on the enzyme glycogen synthase was studied in cultured skin fibroblasts from 5 non-diabetic subjects and 3 diabetic patients. Confluent fibroblast cultures were maintained in serum-free medium for 24 hours before exposure to graduated concentrations of insulin (0.1 to 2000 mU/ml) for one hour. The independent form of glycogen synthase activity (determined in the absence of glucose-6-phosphate) was increased in some experiments by exposure of cells to 0.1 mU of insulin/ml; 1.0mU/ml produced a consistent increase; but at least 1000 mU/ml was required for maximum effect. In the non-diabetic subjects, the mean baseline total activity of glycogen synthase was 0.182 μmol/mg protein/h with 16.8% in the independent form; with 1000 m U of insulin/ml the total activity was 0.167 μmol/mg/h with 45.4% in the independent form. In the diabetic fibroblasts, the mean percentage of glycogen synthase in the independent form was lower than in the control cells at baseline and with all concentrations of insulin utilised; at baseline, total activity was 0.117 μmol/mg protein/h with 11.7% in the independent form while with 1000 mU of insulin/ml the values were 0.146 μmol/mg protein/h and 30.7% respectively. Demonstration of an effect of insulin on glycogen synthase in human fibroblasts provides another phenomenon for comparison in cells from control subjects and diabetic patients.


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Craig, J.W., Huang, L.S. & Larner, J. Insulin stimulation of glycogen synthase activity in cultured human fibroblasts from diabetic and control subjects. Diabetologia 18, 109–113 (1980).

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Key words

  • Glycogen synthase
  • cultured fibroblasts
  • insulin
  • diabetes mellitus