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Caffeine, Insulin, Exercise!
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Posted by: w8lifter
Caffeine-Induced Impairment of Insulin Action but Not Insulin Signaling in Human Skeletal Muscle Is Reduced by Exercise
Farah S.L. Thong1, Wim Derave2, Bente Kiens3, Terry E. Graham1, Birgitte Ursų4, Jųrgen F.P. Wojtaszewski3, Bo F. Hansen4, and Erik A. Richter3
1 Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Canada
2 Department of Kinesiology, Faculty of Physical Education and Physiotherapy, Catholic University Leuven, Leuven, Belgium
3 Copenhagen Muscle Research Centre, Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Copenhagen, Denmark
4 Diabetes Biology, Novo Nordisk, Bagsvaerd, Denmark
We investigated the effects of caffeine ingestion on skeletal muscle glucose uptake, glycogen synthase (GS) activity, and insulin signaling intermediates during a 100-min euglycemic-hyperinsulinemic (100 µU/ml) clamp. On two occasions, seven men performed 1-h one-legged knee extensor exercise at 3 h before the clamp. Caffeine (5 mg/kg) or placebo was administered in a randomized, double-blind fashion 1 h before the clamp. During the clamp, whole-body glucose disposal was reduced (P < 0.05) in caffeine (37.5 ± 3.1 µmol · min-1 · kg-1) vs. placebo (54.1 ± 2.9 µmol · min-1 · kg-1). In accordance, the total area under the curve over 100 min (AUC0100 min) for insulin-stimulated glucose uptake in caffeine was reduced (P < 0.05) by 50% in rested and exercised muscle. Caffeine also reduced (P < 0.05) GS activity before and during insulin infusion in both legs. Exercise increased insulin sensitivity of leg glucose uptake in both caffeine and placebo. Insulin increased insulin receptor tyrosine kinase (IRTK), insulin receptor substrate 1-associated phosphatidylinositol (PI) 3-kinase activities, and Ser473 phosphorylation of protein kinase B (PKB)/Akt significantly but similarly in rested and exercised legs. Furthermore, insulin significantly decreased glycogen synthase kinase-3 (GSK-3) activity equally in both legs. Caffeine did not alter insulin signaling in either leg. Plasma epinephrine and muscle cAMP concentrations were increased in caffeine. We conclude that 1) caffeine impairs insulin-stimulated glucose uptake and GS activity in rested and exercised human skeletal muscle; 2) caffeine-induced impairment of insulin-stimulated muscle glucose uptake and downregulation of GS activity are not accompanied by alterations in IRTK, PI 3-kinase, PKB/Akt, or GSK-3 but may be associated with increases in epinephrine and intramuscular cAMP concentrations; and 3) exercise reduces the detrimental effects of caffeine on insulin action in muscle.
Posted by: The_Chicken_Daddy
Damn, i've been after that study for ages!
you must be some kinda genius to have found it!
Posted by: w8lifter
Oooops, sorry CD....Thanks 
Posted by: The_Chicken_Daddy
haha no worries.
If i posted it it would have probably been ignored...
Posted by: w8lifter
Not by me! 
Posted by: Fat Cell
I can't ignore you! Since your so hot at finding things, Dan Duchaine (RIP) once told me, I can not find
reference in any physiology books, Caffieine affects insulin via the Randall (1 "l" or 2?) Cycle!
FC
Posted by: thleckey
Nice web site. No more coffe for me dammit
Posted by: CDWetzelberger
I read your post twice w8lifter and IM still not sure what it means! So caffeine reduces the uptake of insulin in muscle tissue and this is bad because insulin helps create muscle?
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