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A 3-day dietary manipulation affects muscle glycogen and results in modifications of carbohydrate and fat metabolism during exercise when hyperglycaemic

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Abstract

Purpose

The effect of hyperglycaemia on exercise with low and elevated muscle glycogen on glucose utilization (GUR), carbohydrate and fat oxidation, hormonal and metabolite responses, as well as rating of perceived exertion (RPE) were explored.

Methods

Five healthy trained males were exercised for 90 min at 70% V̇O2max in two trials, while glucose was infused intravenously at rates to “clamp” blood glucose at 12 mM. On one occasion, participants were ‘loaded’ with carbohydrate (CHO-L), whilst on a separate occasion, participants were glycogen depleted (CHO-D). Prior exercise and dietary manipulations produced the ‘loaded’ and ‘depleted’ states.

Results

The CHO-L and CHO-D conditions resulted in muscle glycogen concentrations of 377 and 159 mmol/g dw, respectively. Hyperglycaemia elevated plasma insulin concentrations with higher levels for CHO-L than for CHO-D (P < 0.01). Conversely, CHO-D elevated plasma adrenaline and noradrenaline higher than CHO-L (P < 0.05). Plasma fat metabolites (NEFA, β-hydroxybutyrate, and glycerol) were higher under CHO-D than CHO-L (P < 0.01). The resultant was that the rates of total carbohydrate and fat oxidation were elevated and depressed for loaded CHO-L vs CHO-D respectively (P < 0.01), although no difference was found for GUR (P > 0.05). The RPE over the exercise period was higher for CHO-D than CHO-L (P < 0.05).

Conclusion

Hyperglycaemia during exercise, when muscle glycogen is reduced, attenuates insulin but promotes catecholamines and fat metabolites. The effect is a subsequent elevation of fat oxidation, a reduction in CHO oxidation without a concomitant increase in GUR, and an increase in RPE.

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Abbreviations

ANOVA:

Analysis of variance

CHO-D:

Carbohydrate depleted

CHO-L:

Carbohydrate loaded

CHO:

Carbohydrate

GUR:

Glucose utilization rate

NEFA:

Non-esterified fatty acids

RIA:

Radioimmunoassay

RPE:

Rating of perceived exertion

V̇O2max :

Maximal oxygen update

β-HB:

β-Hydroxybutyrate

References

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Author information

Authors and Affiliations

Authors

Contributions

D.P.M and I.T.C carried out the majority of the study data collection, with I.T.C also providing medical supervision throughout the study. J.J.M, A.T.H, and D.P.M conceived and developed the original study idea and supervised the project. J.J.M led the write up of the study manuscript, with input from all authors. All authors read and approved the manuscript.

Corresponding author

Correspondence to James J. Malone.

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Conflict of interest

The authors declare that they have no conflict of interest.

Additional information

Communicated by Peter Krustrup.

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Iain T. Campbell: Currently retired from Department of Anaesthesia, Wythenshawe Hospital, Manchester, UK.

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Malone, J.J., MacLaren, D.P.M., Campbell, I.T. et al. A 3-day dietary manipulation affects muscle glycogen and results in modifications of carbohydrate and fat metabolism during exercise when hyperglycaemic. Eur J Appl Physiol 120, 873–882 (2020). https://doi.org/10.1007/s00421-020-04326-4

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  • DOI: https://doi.org/10.1007/s00421-020-04326-4

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