To determine whether defects of muscle glycogen synthase (GS) activity can be acquired by exposure to elevated glucose or insulin levels, human skeletal muscle cells obtained by needle biopsy from normal control subjects were grown in culture for 4–6 weeks followed by 4 days of fusion and differentiation in media containing either normal (5.5 mmol/l glucose and 22 pmol/l insulin) or increased concentrations of glucose (20 mmol/l), insulin (30 micromol/l), or both. After fusion in normal media, acute stimulation by 33 nmol/l insulin for 1 h increased GS fractional velocity (FV) ∼ twofold (from 9.01 ± 1.26 to 16.31 ± 2.40, P < 0.05). Increasing the media glucose concentration alone to 20 mmol/l during fusion had no effect on basal FV but caused a marginal impairment of the insulin-stimulated GS response (from 8.51 ± 1.33 to 12.99 ± 1.90, P = 0.08). Increasing the media insulin concentration to 30 micromol/l during fusion at 5.5 mmol/l glucose also did not alter basal GS FV (10.61 ± 1.69%) but completely abolished the normal insulin-stimulated increase in GS activity (to 11.63 ± 1.55%, NS). The combination of high insulin (30 micromol/l) and high glucose (20 mmol/l) during fusion had no greater effect on the FV of either basal (11.66 ± 2.16%, NS) or insulin-stimulated (9.20 ± 1.80%, NS) GS activity than high insulin alone. Fusion in hyperinsulinemic media altered the kinetic parameters of GS with a near doubling of the basal Km0.1 and Vmax0.1 for uridinediphospho-glucose. Hyperinsulinemia also totally prevented the normal insulin-stimulated threefold increase in the Vmax0.1 and the 65% decrease in the A0.5 for glucose-6-phosphate. GS mRNA and protein expression, determined by RNase protection assay and immunoblotting, respectively, were unaffected by changes in media conditions. We conclude that exposure of human skeletal muscle cells primarily to high insulin induces severe insulin resistance through multiple acquired posttranslational defects, which affect both the kinetic characteristics and absolute activity of the GS enzyme.
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Original Articles|
April 01 1996
Acquired Defects of Glycogen Synthase Activity in Cultured Human Skeletal Muscle Cells: Influence of High Glucose and Insulin Levels
Robert R Henry;
Robert R Henry
Department of Medicine, University of California
San Diego, La Jolla, California
Veterans Affairs Medical Center
San Diego, San Diego, California
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Theodore P Ciaraldi;
Theodore P Ciaraldi
Department of Medicine, University of California
San Diego, La Jolla, California
Veterans Affairs Medical Center
San Diego, San Diego, California
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Sunder Mudaliar;
Sunder Mudaliar
Department of Medicine, University of California
San Diego, La Jolla, California
Veterans Affairs Medical Center
San Diego, San Diego, California
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Leslie Abrams;
Leslie Abrams
Department of Medicine, University of California
San Diego, La Jolla, California
Veterans Affairs Medical Center
San Diego, San Diego, California
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Svetlana E Nikoulina
Svetlana E Nikoulina
Department of Medicine, University of California
San Diego, La Jolla, California
Veterans Affairs Medical Center
San Diego, San Diego, California
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Address correspondence and reprint requests to Dr. Robert R. Henry, VA Medical Center, San Diego (VI11G), 3350 La Jolla Village Dr., San Diego, CA 92161.
Diabetes 1996;45(4):400–407
Article history
Received:
August 28 1995
Revision Received:
November 30 1995
Accepted:
November 30 1995
PubMed:
8603759
Citation
Robert R Henry, Theodore P Ciaraldi, Sunder Mudaliar, Leslie Abrams, Svetlana E Nikoulina; Acquired Defects of Glycogen Synthase Activity in Cultured Human Skeletal Muscle Cells: Influence of High Glucose and Insulin Levels. Diabetes 1 April 1996; 45 (4): 400–407. https://doi.org/10.2337/diab.45.4.400
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