| Popis: |
Calorie restriction (CR) (consuming ~60% of ad libitum, AL, intake) improves whole body insulin sensitivity and enhances insulin-stimulated glucose uptake by isolated skeletal muscles. However, little is known about CR-effects on in vivo glucose uptake and insulin signaling in muscle. Accordingly, 9-month-old male AL and CR (initiated when 3-months-old) Fischer 344 x Brown Norway rats were studied using a euglycemic-hyperinsulinemic clamp with plasma insulin elevated to a similar level (~140 µU/ml) in each diet group. Glucose uptake (assessed by infusion of [(14)C]-2-deoxyglucose, 2-DG), phosphorylation of key insulin signaling proteins (insulin receptor, Akt and Akt substrate of 160 kDa, AS160), abundance of GLUT4 and hexokinase proteins, and muscle fiber type composition (myosin heavy chain, MHC, isoform percentages) were determined in four predominantly fast-twitch (epitrochlearis, gastrocnemius, tibialis anterior, plantaris) and two predominantly slow-twitch (soleus, adductor longus) muscles. CR did not result in greater GLUT4 or hexokinase abundance in any of the muscles, and there were no significant diet-related effects on percentages of MHC isoforms. Glucose infusion was greater for CR versus AL rats (P |
