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- Friedrichsen, M., et al.
(författare)
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Differential aetiology and impact of phosphoinositide 3-kinase (PI3K) and Akt signalling in skeletal muscle on in vivo insulin action
- 2010
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 53:9, s. 1998-2007
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis Insulin resistance in skeletal muscle is a key factor in the development of type 2 diabetes and although some studies indicate that this could be partly attributed to reduced content and activity of various proximal and distal insulin signalling molecules, consensus is lacking. We therefore aimed to investigate the regulation of proximal insulin signalling in skeletal muscle and its effect on glucose metabolism in a large non-diabetic population. Methods We examined 184 non-diabetic twins with gold-standard techniques including the euglycaemic-hyperinsulinaemic clamp. Insulin signalling was evaluated at three key levels, i.e. the insulin receptor, IRS-1 and V-akt murine thymoma viral oncogene (Akt) levels, employing kinase assays and phospho-specific western blotting. Results Proximal insulin signalling was not associated with obesity, age or sex. However, birthweight was positively associated with IRS-1-associated phosphoinositide 3-kinase (PI3K; IRS-1-PI3K) activity (p=0.04); maximal aerobic capacity ((V) over dotO(2max)), paradoxically, was negatively associated with IRS-1-PI3K (p=0.02) and Akt2 activity (p=0.01). Additionally, we found low heritability estimates for most measures of insulin signalling activity. Glucose disposal was positively associated with Akt-308 phosphorylation (p<0.001) and Akt2 activity (p=0.05), but not with insulin receptor tyrosine kinase or IRS-1-PI3K activity. Conclusions/interpretation With the exception of birthweight, 'classical' modifiers of insulin action, including genetics, age, sex, obesity and (V) over dotO(2max), do not seem to mediate their most central effects on whole-body insulin sensitivity through modulation of proximal insulin signalling in skeletal muscle. We also demonstrated an association between Akt activity and in vivo insulin sensitivity, suggesting a role of Akt in control of in vivo insulin resistance and potentially in type 2 diabetes.
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| 3. |
- 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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