Abstract
We investigated if a bout of exercise in a hot environment (HEAT) would reduce the postprandial hyperglycemia induced by glucose ingestion. The hypothesis was that HEAT stimulating carbohydrate oxidation and glycogen use would increase the disposal of an ingested glucose load [i.e., oral glucose tolerance test (OGTT); 75 g of glucose]. Separated by at least 1 wk, nine young healthy individuals underwent three trials after an overnight fast in a randomized order. Two trials included 50 min of pedaling at 58 ± 5% V_ O2max either in a thermoneutral (21 ± 1°C; NEUTRAL) or in a hot environment (33 ± 1°C; HEAT) eliciting similar energy expenditure (503 ± 101 kcal). These two trials were compared with a no-exercise trial (NO EXER). Twenty minutes after exercise (or rest), subjects underwent an OGTT, while carbohydrate oxidation (CHOxid, using indirect calorimetry) plasma blood glucose, insulin concentrations (i.e., [glucose], [insulin]), and double tracer glucose kinetics ([U-13C] glucose ingestion and [6,6-2H2] glucose infusion) were monitored for 120 min. At rest, [glucose], [insulin], and rates of appearance/disappearance of glucose in plasma (glucose Ra/Rd) were similar among trials. During exercise, heart rate, tympanic temperature, [glucose], glycogen oxidation, and total CHOxid were higher during HEAT than NEUTRAL (i.e., 149 ± 35 vs. 124 ± 31 lmol·kg-1·min-1, P = 0.010). However, during the following OGTT, glucose Rd was similar in HEAT and NEUTRAL trials (i.e., 25.1 ± 3.6 vs. 25.2 ± 5.3 lmol·kg-1·min-1, P = 0.981). Insulin sensitivity (i.e., ISIndexMATSUDA) only improved in NEUTRAL compared with NO EXER (10.1 ± 4.6 vs. 8.8 ± 3.7 au; P = 0.044). In summary, stimulating carbohydrate use with exercise in a hot environment does not improve postprandial plasma glucose disposal or insulin sensitivity in a subsequent OGTT.
Original language | English |
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Pages (from-to) | E648-E662 |
Number of pages | 15 |
Journal | American Journal of Physiology - Endocrinology and Metabolism |
Volume | 326 |
Issue number | 5 |
Early online date | 30 Apr 2024 |
DOIs | |
Publication status | Published - 31 May 2024 |
Externally published | Yes |
Data Availability Statement
Data will be made available upon reasonable request.Funding
This work was partially funded by a grant from the Spanish Ministry of Science and Innovation PID2020-116159RB-I00 and European Community funds.
Funders | Funder number |
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Ministerio de Ciencia e Innovacion | PID2020-116159RB-I00 |
Ministerio de Ciencia e Innovacion |
Keywords
- exercise
- glucose kinetics
- hyperthermia
- insulin resistance
- stable isotopes
ASJC Scopus subject areas
- General Medicine