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Clinical Trial
. 2005 Oct 15;568(Pt 2):665-76.
doi: 10.1113/jphysiol.2005.089839. Epub 2005 Jul 28.

Short-term exercise training in humans reduces AMPK signalling during prolonged exercise independent of muscle glycogen

Glenn K McConell  1 , Robert S Lee-Young, Zhi-Ping Chen, Nigel K Stepto, Ngan N Huynh, Terry J Stephens, Benedict J Canny, Bruce E Kemp
Affiliations
Clinical Trial

Short-term exercise training in humans reduces AMPK signalling during prolonged exercise independent of muscle glycogen

Glenn K McConell et al. J Physiol. .

Abstract

We examined the effect of short-term exercise training on skeletal muscle AMP-activated protein kinase (AMPK) signalling and muscle metabolism during prolonged exercise in humans. Eight sedentary males completed 120 min of cycling at 66 +/- 1% , then exercise trained for 10 days, before repeating the exercise bout at the same absolute workload. Participants rested for 72 h before each trial while ingesting a high carbohydrate diet (HCHO). Exercise training significantly (P < 0.05) attenuated exercise-induced increases in skeletal muscle free AMP: ATP ratio and glucose disposal and increased fat oxidation. Exercise training abolished the 9-fold increase in AMPK alpha2 activity observed during pretraining exercise. Since training increased muscle glycogen content by 93 +/- 12% (P < 0.01), we conducted a second experiment in seven sedentary male participants where muscle glycogen content was essentially matched pre- and post-training by exercise and a low CHO diet (LCHO; post-training muscle glycogen 52 +/- 7% less than in HCHO, P < 0.001). Despite the difference in muscle glycogen levels in the two studies we obtained very similar results. In both studies the increase in ACCbeta Ser(221) phosphorylation was reduced during exercise after training. In conclusion, there is little activation of AMPK signalling during prolonged exercise following short-term exercise training suggesting that other factors are important in the regulation of glucose disposal and fat oxidation under these circumstances. It appears that muscle glycogen is not an important regulator of AMPK activation during exercise in humans when exercise is begun with normal or high muscle glycogen levels.

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Figures

Figure 1
Figure 1. Muscle glycogen content (A), AMPK α1 activity (B), and AMPK α2 activity (C) at rest (0 min), after 30 min, and at the completion of exercise (End) at 66 ± 1% (HCHO □) and 67 ± 1% (LCHO ▪) of pretraining V˙O2peak conducted pre- and post-10-days of exercise training
Data are means ±s.e.m. For muscle glycogen, n = 7 (HCHO and LCHO); for AMPK activity n = 5 (HCHO) and n = 7 (LCHO). *Significantly different from corresponding pre-training value, P < 0.001; §significant time effect (in both HCHO and LCHO), P < 0.01; †significant trial effect (pre-training versus post-training in both HCHO and LCHO), P < 0.01; ‡significantly different from HCHO, P < 0.001.
Figure 2
Figure 2. Relationship between skeletal muscle AMPK α2 activity and AMPf (μM) at rest, after 30 min and at the completion of exercise at 66 ± 1% (HCHO) and 67 ± 1% (LCHO) of pretraining V˙O2peak conducted pre- and post-10-days of exercise training
Inset shows ratio of AMPK α2 activity (pmol min−1 (mg protein)−1) to AMPf (μM) after 30 min of exercise and at the completion of exercise at 66 ± 1% (HCHO) and 67 ± 1% (LCHO) of pre-training V˙O2peak conducted pre- and post-10-days of exercise training. n = 7 for LCHO and n = 4 for HCHO since there was no AMPf measurement for one participant in HCHO.
Figure 3
Figure 3. ACC-β Ser221 phosphorylation at rest (0 min), after 30 min and at the completion of exercise (End) at 66 ± 1% (HCHO □) and 67 ± 1% (LCHO ▪) of pretraining V˙O2peak conducted pre- and post-10-days of exercise training
Affinity purified muscle ACCβ were immunoblotted with phospho-peptide antibody ACC-β-Ser221 and horseradish peroxidase-conjugated Streptavidin. A, representative immunoblot. B, mean quantitative densitometric data. Data are means ±s.e.m.n = 5 (HCHO) and n = 7 (LCHO), except for 0 where n = 6 for LCHO. *Significantly different from corresponding pre-training value, P < 0.05; §significant time effect (in both HCHO and LCHO), P < 0.01.
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Comment in

  • Governor recalled! Now what?
    Brooks GA. Brooks GA. J Physiol. 2005 Oct 15;568(Pt 2):355. doi: 10.1113/jphysiol.2005.095257. Epub 2005 Aug 4. J Physiol. 2005. PMID: 16081480 Free PMC article. No abstract available.

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