Supraclavicular thermography does not isolate a brown adipose tissue signal during room temperature β-adrenergic stimulation in adults.
Taylor R Ewell, Christina M N Cheng, Matthew C Bomar et al.
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In 30 seconds
Two randomized, single-blind, placebo-controlled crossover trials studied thermogenic responses to β-adrenergic stimulation in healthy adults. During graded intravenous isoproterenol infusion, energy expenditure rose at all doses, reaching a mean increase of 0.20 [0.13, 0.26] kcal/min at 24 ng/kg fat-free mass/min. Infrared thermography showed supraclavicular warming at the highest dose, but the sternum warmed more, indicating that the supraclavicular signal was not regionally specific. Mirabegron increased energy expenditure without raising supraclavicular temperature; vitamin C did not augment thermogenesis.
Key findings
- Isoproterenol increased energy expenditure at each dose; at 24 ng/kg fat-free mass/min, the mean difference was 0.20 [0.13, 0.26] kcal/min.
- At the highest isoproterenol dose, supraclavicular temperature rose by 0.56°C [0.24, 0.88], while sternum warming exceeded it by 0.70°C [0.28, 1.12].
- Mirabegron increased energy expenditure by 0.07 [0.04, 0.10] kcal/min without increasing supraclavicular skin temperature (p = 0.29).
- Vitamin C did not augment thermogenesis.
Why it matters
Infrared thermography of the supraclavicular region is sometimes used to assess brown adipose tissue activity. These findings show that, during room-temperature β-adrenergic stimulation, local warming may not distinguish a BAT-related signal from temperature changes elsewhere. Interpreting supraclavicular skin temperature alone as evidence of BAT activation could therefore overstate what this measure establishes.
What to keep in mind
The trials assessed acute responses under room-temperature conditions in healthy adults; the findings do not establish how well thermography reflects BAT activity in other populations or settings.