Physiology of cold exposed humans and the implications for type 2 diabetes

Abstract

Muscle glycogen use and glucose uptake during cold exposure increases with shivering intensity. We hypothesized that cold exposure, with shivering, would subsequently increase glucose tolerance. Fifteen healthy men (age = 26 ± 5 yr, body mass index = 23.9 ± 2.5 kg m -2 ) completed two experimental trials after an overnight fast. Cold exposure (10°C) was applied during the first trial, via a waterperfused suit, to induce at least 1 h of shivering in each participant. For comparison, a thermoneutral (32°C) condition was applied during the second trial, under identical conditions, for the same duration as determined during the cold exposure. After the thermal exposures, participants rested under a duvet for 90 min which was followed by a 3-h oral glucose tolerance test. Skin temperature (mean ± SE) decreased at the end of the cold exposure compared to before (26.9 ± 0.3 vs. 33.7 ± 0.1°C, P < 0.001). Total energy expenditure during the 1 h of shivering was larger than during the timematched thermoneutral condition (619 ± 23 vs. 309 ± 7 kJ, P < 0.001). Cold exposure increased the areas under the glucose and insulin curves by 4.8% (P = 0.066) and 24% (P = 0.112), respectively. The Matsuda and insulin-glucose indices changed after cold exposure by −21% (P = 0.125), and 30% (P = 0.100), respectively. Cold exposure did not subsequently increase glucose tolerance. Instead, the Matsuda and insulin-glucose indices suggest insulin resistance post-shivering.