Postmarathon paradox: insulin resistance in the face of glycogen depletion.
Acute physical exercise enhances insulin sensitivity in healthy subjects. We examined the effect of a 42-km marathon run on insulin sensitivity and lipid oxidation in 19 male runners. In the morning after the marathon run, basal serum free fatty acid concentration was 2.2-fold higher, muscle glycogen content 37% lower (P < 0.01), glycogen synthase fractional activity 56% greater (P < 0.01), and glucose oxidation reduced by 43% (P < 0.01), whereas lipid oxidation was increased by 55% (P < 0.02) compared with the control study. During euglycemic-hyperinsulinemic clamp, whole body glucose disposal was decreased by 12% (P < 0.01) because of a 36% lower glucose oxidation rate (P < 0.05), whereas the rate of lipid oxidation was 10-fold greater (P < 0.02) than in the control study. After the marathon, muscle glycogen content correlated positively with lipid oxidation (r = 0.60, P < 0.05) and maximal aerobic power (Vo2peak; r = 0.61, P < 0.05). Vo2peak correlated positively with basal lipid oxidation (r = 0.57, P < 0.05). In conclusion, 1) after the marathon run, probably because of increased lipid oxidation, the insulin-stimulated glucose disposal is decreased despite muscle glycogen depletion and the activation of glycogen synthase; 2) the contribution of lipid oxidation in energy expenditure is increased in proportion to physical fitness; 3) these adaptations of fuel homeostasis may contribute to the maintenance of physical performance after prolonged exercise.
Tuominen
J A
JA
Department of Medicine, Helsinki University Central Hospital, Finland.
Ebeling
P
P
Bourey
R
R
Koranyi
L
L
Lamminen
A
A
Rapola
J
J
Sane
T
T
Vuorinen-Markkola
H
H
Koivisto
V A
VA
D000328:Adult; D001769:Blood / Q000378:metabolism; D004734:Energy Metabolism; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000172:deficiency* / Q000378:metabolism; D006006:Glycogen Synthase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007333:Insulin Resistance; D050356:Lipid Metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins; D009132:Muscles / Q000033:anatomy & histology / Q000378:metabolism; D010084:Oxidation-Reduction; D010807:Physical Endurance; D012333:RNA, Messenger / Q000378:metabolism; D012420:Running
D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C495692:SLC2A4 protein, human; D006003:Glycogen; D006006:Glycogen Synthase; D005947:Glucose