Daily Cold Exposure Increases Brown Adipose Tissue-Derived Thermogenesis in Adult Humans

Abstract

Recent studies examining brown adipose tissue (BAT) metabolism in adult humans have provided convincing evidence of its thermogenic potential and role in taking up circulating glucose and fatty acids under acute mild cold exposure. In contrast, early indications suggest that BAT metabolism is defective in obesity and type 2 diabetes (T2D), which may have important pathological and therapeutic implications. Although, many mammalian models have demonstrated the adaptability of this tissue through chronic cold exposure, little is known about its plasticity in humans. Using electromyography combined with positron emission tomography with 11C-acetate and 18F-fluorodeoxyglucose, shivering intensity and BAT oxidative metabolism and glucose uptake prior to and following 4 weeks of cold acclimation were examined. Non-acclimated healthy, lean men were exposed to 10°C, 2 hours daily for 4 weeks (5 days/week), using a liquid-conditioned suit (LCS). This acclimation protocol elicited a 45% increase in BAT volume (from 66±30 to 95±28 mL, P<0.05) and a 2.2-fold increase in the total BAT oxidative metabolism index (from 0.725±0.300 to 1.591±0.326 mL•sec-1, P<0.05) without a change in shivering intensity (from 2.1±0.7 to 2.0±0.5 %MVC), despite similar cold-induced increases in metabolic rate (0.513±0.037 and 0.516±0.038 L/min, pre- and post-acclimation, respectively). Fractional and net glucose uptake in BAT were also similar pre- and post-acclimation (from 0.035±0.014 to 0.048±0.012 min-1 and from 163±60 to 209±50 nmol•g-1•min-1). These results demonstrate an increased capacity of BAT-derived thermogenesis following a 4-week cold acclimation period in healthy men. This research was supported by NSERC (grant RGPIN/326967-2011) and the Canadian Diabetes Association (grant OG 3-10-2970-AC).