The effect of acute exercise on glycogen synthesis rate in obese subjects studied by super(13)C MRS

• Published in: European journal of applied physiology Vol. 111; no. 2; pp. 275 - 283
• Main Authors: Graaf, Marinette, Haan, Jacco H, Smits, Paul, Mulder, Alexandra H, Heerschap, Arend, Tack, Cees J
• Format: Journal Article
• Language: English
• Published: 01.02.2011
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-010-1650-0

In obesity, insulin-stimulated glucose uptake in skeletal muscle is decreased. We investigated whether the stimulatory effect of acute exercise on glucose uptake and subsequent glycogen synthesis was normal. The study was performed on 18 healthy volunteers, 9 obese (BMI=32.6 plus or minus 1.2kg/m super(2), mean plus or minus SEM) and 9 lean (BMI=22.0 plus or minus 0.9kg/m super(2)), matched for age and gender. All participants underwent a euglycemic hyperinsulinemic clamp, showing reduced glucose uptake in the obese group (P=0.01), during which they performed a short intense local exercise (single-legged toe lifting). Dynamic glucose incorporation into glycogen in the gastrocnemius muscle before and after exercise was assessed by super(13)C magnetic resonance spectroscopy combined with infusion of [1- super(13)C]glucose. Blood flow was measured to investigate its potential contribution to glucose uptake. Before exercise, glycogen synthesis rate tended to be lower in obese subjects compared with lean (78 plus or minus 14 vs. 132 plus or minus 24 mu mol/kg muscle/min; P=0.07). Exercise induced highly significant rises in glycogen synthesis rates in both groups, but the increase in obese subjects was reduced compared with lean (112 plus or minus 15 vs. 186 plus or minus 27 mu mol/kg muscle/min; P=0.03), although the relative increase was similar (184 plus or minus 35 vs. 202 plus or minus 51%; P=0.78). After exercise, blood flow increased equally in both groups, without a temporal relationship with the rate of glycogen synthesis. In conclusion, this study shows a stimulatory effect of a short bout of acute exercise on insulin-induced glycogen synthesis rate that is reduced in absolute values but similar in percentages in obese subjects. These results suggest a shared pathway between insulin- and exercise-induced glucose uptake and subsequent glycogen synthesis.