Temperature-acclimated brown adipose tissue modulates insulin sensitivity in humans.
Level 3 - non-randomized controlled study
Prospective non-randomized crossover study
PubMed 24954193 · doi:10.2337/db14-0513
What was done
Five healthy men participated in a 4-month prospective crossover study involving four consecutive 1-month blocks of overnight temperature acclimation in a controlled facility: 24 °C (baseline, month 1), 19 °C (mild cold, month 2), 24 °C (washout, month 3), and 27 °C (warm, month 4). Researchers evaluated brown adipose tissue (BAT) abundance and activity, cold-induced thermogenesis (CIT), diet-induced thermogenesis (DIT), postprandial insulin sensitivity, and circulating and tissue-specific expression of leptin and adiponectin.
What was found
Sequential monthly acclimation reversibly modulated BAT, increasing its abundance and activity during mild cold (19 °C) and suppressing it during warm conditions (27 °C) (P < 0.05), independent of seasonal variation (P < 0.01). Cold acclimation did not alter CIT, but significantly increased DIT (P < 0.05) and enhanced postprandial insulin sensitivity (P < 0.05). Circulating and adipose tissue levels (but not skeletal muscle levels) of leptin and adiponectin showed reciprocal changes concordant with improved insulin sensitivity. Numerical values for outcomes were not reported in the abstract.
Why it matters
This study demonstrates that human brown adipose tissue volume and activity are dynamically plastic and reversible in response to ambient temperature, and that cold-induced BAT expansion correlates with improved postprandial glucose metabolism.
Limits
The study is limited by an extremely small sample size (n = 5) comprising only healthy men, limiting generalizability to women or individuals with metabolic disease. The intervention used a fixed sequential order of temperature exposures rather than a randomized order, leaving open potential period or carryover effects.
Cited by
- context Young healthy men who wore a cooling suit set to 50°F for 2 hours daily for 1 month experienced an almost 50% increase in brown adipose tissue.