| 1. |
- Goodyear, Laurie J.L, et al.
(författare)
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Glucoseingestion causes GLUT4 translocation in human skeletal muscle
- 1996
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 45:8, s. 1051-1056
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Tidskriftsartikel (refereegranskat)abstract
- In humans, ingestion of carbohydrates causes an increase in blood glucose concentration, pancreatic insulin release, and increased glucose disposal into skeletal muscle. The underlying molecular mechanism for the increase in glucose disposal in human skeletal muscle after carbohydrate ingestion is not known. We determined whether glucoseingestion increases glucose uptake in human skeletal muscle by increasing the number of glucose transporter proteins at the cell surface and/or by increasing the activity of the glucose transporter proteins in the plasma membrane. Under local anesthesia, approximately 1 g of vastus lateralis muscle was obtained from six healthy subjects before and 60 min after ingestion of a 75-g glucose load. Plasma membranes were isolated from the skeletal muscle and used to measure GLUT4 and GLUT1 content and glucosetransport in plasma membrane vesicles. Glucose ingestion increased the plasma membrane content of GLUT4 per gram muscle (3,524 +/- 729 vs. 4,473 +/- 952 arbitrary units for basal and 60 min, respectively; P < 0.005). Transporter-mediated glucosetransport into plasma membrane vesicles was also significantly increased (130 +/- 11 vs. 224 +/- 38 pmol.mg-1.s-1; P < 0.017), whereas the calculated ratio of glucose transport to GLUT4, an indication of transporter functional activity, was not significantly increased 60 min after glucose ingestion (2.3 +/- 0.4 vs. 3.0 +/- 0.5 pmol.GLUT4 arbitrary units-1.s-1; P < 0.17). These results demonstrate that oral ingestion of glucose increases the rate of glucose transport across the plasma membrane and causes GLUT4 translocation in human skeletal muscle. These findings suggest that under physiological conditions the translocation of GLUT4 is an important mechanism for the stimulation of glucose uptake in human skeletal muscle.
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| 2. |
- Thorell, Anders, et al.
(författare)
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Exerciseand insulin cause GLUT-4 translocation in human skeletal muscle
- 1999
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Ingår i: American Journal of Physiology. - : American Physiological Society. - 0002-9513 .- 2163-5773. ; 277:4, s. E733-E741
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Tidskriftsartikel (refereegranskat)abstract
- Studies in rodents have established that GLUT-4 translocation is the major mechanism by which insulin and exercise increase glucose uptake in skeletal muscle. In contrast, much less is known about the translocationphenomenon in human skeletal muscle. In the current study, nine healthy volunteers were studied on two different days. On one day, biopsies of vastus lateralis muscle were taken before and after a 2-h euglycemic- hyperinsulinemic clamp (0.8 mU · kg-1 · min-1). On another day, subjects exercised for 60 min at 70% of maximal oxygen consumption (VO(2max)), a biopsy was obtained, and the same clamp and biopsy procedure was performed as that during the previous experiment. Compared with insulin treatment alone, glucose infusion rates were significantly increased during the postexercise clamp for the periods 0-30 min, 30-60 min, and 60-90 min, but not during the last 30 min of the clamp. Plasma membrane GLUT-4 content was significantly increased in response to physiological hyperinsulinemia (32% above rest), exercise (35%), and the combination of exercise plus insulin(44%). Phosphorylation of Akt, a putative signaling intermediary for GLUT-4 translocation, was increased inresponse to insulin (640% above rest), exercise (280%), and exercise plus insulin (1,000%). These data demonstrate that two normal physiological conditions, moderate intensity exercise and physiological hyperinsulinemia ~56 μU/ml, cause GLUT-4 translocation and Akt phosphorylation in human skeletal muscle.
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| 3. |
- Thorell, Anders, et al.
(författare)
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Surgery-induced insulin resistance in human patients relations to glucoseutilization and transport
- 1999
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Ingår i: American Journal of Physiology. - : American Physiological Society. - 0002-9513 .- 2163-5773. ; 276:4, s. E754-E761
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the underlying molecular mechanisms for surgery-induced insulin resistance in skeletal muscle, six otherwise healthy patients undergoing total hip replacement were studied before, during, and after surgery. Patients were studied under basal conditions and during physiological hyperinsulinemia (60 microU/ml). Biopsies of vastus lateralis muscle were used to measure GLUT-4 translocation, glucose transport, and glycogen synthase activities. Surgery reduced insulin-stimulated glucose disposal (P < 0.05) without altering the insulin-stimulated increase in glucose oxidation or suppression of endogenous glucose production. Preoperatively, insulin infusion increased plasma membrane GLUT-4 in all six subjects (P < 0.05), whereas insulin-stimulated GLUT-4 translocation only occurred in three patientspostoperatively (not significant). Moreover, nonoxidative glucose disposal rates and basal levels of glycogen synthase activities in muscle were reduced postoperatively (P < 0.05). These findings demonstrate that peripheral insulin resistance develops immediately postoperatively and that this condition might be associated with perturbations in insulin-stimulated GLUT-4 translocation as well as nonoxidative glucose disposal, presumably at the level of glycogen synthesis.
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