Whole body heat exposure modulates acute glucose metabolism

Abstract

AIM: Exercise modulates glucose tolerance and homeostasis in both healthy and diabetic individuals. Heat stress is a fundamental element of exercise. The acute glycemic response and alterations in glucose clearance following whole body passive heat stress in the absence of muscle activity has yet to be examined in humans. Knowledge of this relationship may prove useful, particularly in populations with compromised glucoregulation from reduced activity. PURPOSE: To determine insulin/glucose levels before and after an acute bout of heat stress in healthy, lean individuals and examine the effects of whole body heat stress (WBHS) and exercise on acute glucose tolerance in an expanded cohort. METHODS: Ten subjects (24.1 ± 0.7 years) participated in a randomized control/WBHS session (up to 30 minutes at 73 °C) with fasting glucose (FG) and insulin drawn at baseline, immediately after and 30 minutes post heat stress. In the follow-up experiment, 20 anthropometrically diverse subjects (24.6 ± 2.1 years) underwent an oral glucose tolerance test (OGTT) under the conditions above. RESULTS: FG levels rose 10% immediately following heat stress (8.6 (±5.6) mg/dl, p < .01) and returned to near baseline levels 30 minutes following WBHS. Insulin release showed its greatest increase at 30 minutes post WBHS (2.7 ± 3.5) uU/ml p < .05). WBHS resulted in a decrease in glucose uptake [AUC increased 8.2% (1430.6 ± 1957.03) mg/dl (p = .005)], particularly in nonlean individuals. CONCLUSION: WBHS modulates physiologic markers of metabolism. An acute bout of WBHS increases glucose and insulin levels in healthy individual and decreases glucose uptake in response to a glucose challenge, particularly those who are non-lean.