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Cold acclimation increased brown adipose tissue, enhanced thermogenic potential
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Daily exposure to cold temperatures appears to not only increase the body’s volume of metabolically active brown adipose tissue, but also enhance its oxidative and thermogenic capabilities, according to study results.
Researchers enrolled six healthy, lean men aged 23 years with a BMI of 24.5 and body surface area of 2.01 m2. The men participated in two metabolic investigational sessions designed to test the effects of cold exposure to overall and tissue-specific metabolism. For 4 weeks, these non–cold-acclimated participants underwent 2 hours of daily cold exposure, achieved through the circulation of 10°C water through a liquid-conditioned suit. This regimen was replicated 5 consecutive days per week during the study period.
The researchers measured entire body metabolic heat production via indirect respiratory calorimetry, as well as whole body and muscle-specific shivering intensity and patterns.
Tissue oxidative metabolism was measured through CT and PET scans, and fasting glucose uptake was determined by administering a bolus of 18F-fluorodeoxyglucose (FDG) 2 hours after cold-acclimation sessions. The total brown adipose tissue (BAT) volume of activity on scans of the entire body was assessed based on 18F-FDG uptake during cold exposure of more than 1.5 standard uptake value units.
These measurements were taken before and after 4 weeks of cold acclimation.
The researchers found that after the 4-week acclimation regimen, there was a 45% increase in BAT volume of activity, from 66 mL to 95 mL (P<.05), and a more than twofold increase in cold-induced total BAT oxidative metabolism, from 0.725 mL/sec-1 to 1.591 mL/sec-1 (P<.05). There was no significant difference in shivering intensity before vs. after cold acclimation — 2.1% maximal voluntary contraction vs. 2% maximal voluntary contraction. There was an increase in fractional glucose uptake in BAT after cold acclimation, from 0.035 min-1 to 0.048 min-1, as well as a trend toward an increase in net glucose uptake, from 163 nmol/g-1/min-1 to 209 nmol/g-1/min-1.
“We showed that total BAT volume of activity increases significantly as a result of repeated controlled daily cold exposure, and that this change in mass is paralleled by an increase in BAT oxidative capacity,” the researchers wrote. “Therefore, the contribution of BAT to non-shivering thermogenesis must necessarily increase during cold-acclimation in humans.”
Disclosure: The researchers report no relevant financial disclosures.
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