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

Malone, James J. and MacLaren, Don P. M. and Campbell, Iain T. and Hulton, Andrew T. (2020) A 3-day dietary manipulation affects muscle glycogen and results in modifications of carbohydrate and fat metabolism during exercise when hyperglycaemic. European Journal of Applied Physiology. ISSN 1439-6319

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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 minutes 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.

Item Type: Article
Additional Information and Comments: This is the author's version of an article that was accepted for publication in the European Journal of Applied Physiology. The final publication is available from https://link.springer.com/article/10.1007%2Fs00421-020-04326-4
Keywords: Hyperglycaemia; Hormones; Glucose utilisation; Carbohydrate oxidation; Muscle glycogen; RPE
Faculty / Department: Faculty of Science > School of Health Sciences
Depositing User: James Malone
Date Deposited: 25 Feb 2020 09:54
Last Modified: 25 Feb 2020 09:54
URI: https://hira.hope.ac.uk/id/eprint/3022

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