The Effect of Environmental Temperature on Glucose and Insulin After an Oral Glucose Tolerance Test in Healthy Young Men

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Abstract

Objective The purpose of this study was to compare glucose and insulin responses during an oral glucose tolerance test (OGTT) in cold (C), neutral (N), and hot (H) environments. Methods Eleven males completed three 4-hour climate-controlled OGTT trials (C, 7.2°C; N, 22°C; and H, 43°C). Participants remained semireclined for 60 minutes before ingesting a 1.8 g/kg glucose beverage. Skin and rectal core temperatures were continuously monitored. Blood was collected just before glucose ingestion (time 0) and at 15, 30, 60, 90, 120, and 180 minutes, and analyzed for serum glucose, insulin, hematocrit, and hemoglobin. Expired gases were collected upon entering the chamber (-60 minutes), before glucose ingestion (0 minutes), and at 60, 120, and 180 minutes to determine Vo2 and respiratory exchange ratio. Results Rectal core temperature was greater in the H condition compared with both C and N (P <.001). Rectal core temperature was not different between C and N, whereas skin temperature was different across all trials (H greater than N greater than C). The Vo2 was greater in C than in both H and N during all time points. Carbohydrate oxidation was greater in C compared with H and N (P < 0.001). Glucose was higher during H compared with C and N (P ≤ 0.002). Glucose was elevated in C compared with N. Insulin was higher in H compared with C (P = 0.009). Area under the curve for serum glucose was greater in H compared with C and N (P ≤ 0.001); however, there was no significant difference in area under the curve for insulin. Conclusions These data indicate that after an OGTT, glucose and insulin are elevated in a hot environment.

Original languageEnglish
Article number609
Pages (from-to)335-342
Number of pages8
JournalWilderness and Environmental Medicine
Volume26
Issue number3
DOIs
StatePublished - Sep 1 2015

Funding

The authors wish to thank the subjects for their investment in time and energy. This study was supported by a grant award from the Office of Naval Research ( N000140910850 ). The authors declare that they have no competing interests in access to these data or associations with companies involved with products used in this research. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Office of Naval Research or the US government.

FundersFunder number
Office of Naval ResearchN000140910850

    Keywords

    • cold
    • environmental stress
    • heat
    • oral glucose tolerance test

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