Increased Brown Adipose Tissue Oxidative Capacity in Cold-Acclimated Humans

J Clin Endocrinol Metab. 2014 Mar;99(3):E438-46. doi: 10.1210/jc.2013-3901. Epub 2014 Jan 13.

Abstract

Context: Recent studies examining brown adipose tissue (BAT) metabolism in adult humans have provided convincing evidence of its thermogenic potential and role in clearing 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, which may have important pathological and therapeutic implications. Although many mammalian models have demonstrated the phenotypic flexibility of this tissue through chronic cold exposure, little is known about the metabolic plasticity of BAT in humans.

Objective: Our objective was to determine whether 4 weeks of daily cold exposure could increase both the volume of metabolically active BAT and its oxidative capacity.

Design: Six nonacclimated men were exposed to 10°C for 2 hours daily for 4 weeks (5 d/wk), using a liquid-conditioned suit. Using electromyography combined with positron emission tomography with [(11)C]acetate and [(18)F]fluorodeoxyglucose, shivering intensity and BAT oxidative metabolism, glucose uptake, and volume before and after 4 weeks of cold acclimation were examined under controlled acute cold-exposure conditions.

Results: The 4-week acclimation protocol elicited a 45% increase in BAT volume of activity (from 66 ± 30 to 95 ± 28 mL, P < .05) and a 2.2-fold increase in cold-induced total BAT oxidative metabolism (from 0.725 ± 0.300 to 1.591 ± 0.326 mL·s(-1), P < .05). Shivering intensity was not significantly different before compared with after acclimation (2.1% ± 0.7% vs 2.0% ± 0.5% maximal voluntary contraction, respectively). Fractional glucose uptake in BAT increased after acclimation (from 0.035 ± 0.014 to 0.048 ± 0.012 min(-1)), and net glucose uptake also trended toward an increase (from 163 ± 60 to 209 ± 50 nmol·g(-1)·min(-1)).

Conclusions: These findings demonstrate that daily cold exposure not only increases the volume of metabolically active BAT but also increases its oxidative capacity and thus its contribution to cold-induced thermogenesis.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acclimatization*
  • Acetic Acid
  • Adipose Tissue, Brown / anatomy & histology
  • Adipose Tissue, Brown / diagnostic imaging
  • Adipose Tissue, Brown / metabolism*
  • Adult
  • Body Temperature Regulation
  • Carbon Radioisotopes
  • Cold Temperature*
  • Energy Metabolism
  • Fluorodeoxyglucose F18
  • Humans
  • Male
  • Organ Size
  • Oxidation-Reduction
  • Positron-Emission Tomography
  • Young Adult

Substances

  • Carbon Radioisotopes
  • Fluorodeoxyglucose F18
  • Acetic Acid