Abstract
Humans have metabolically active brown adipose tissue (BAT). However, what is the relation between exercise or physical activity with this tissue remains controversial. Therefore, the main aim of the present study is to examine whether cardiorespiratory fitness and muscular strength are associated with brown adipose tissue (BAT) volume and activity after exposure to cold in young, sedentary adults. Cardiorespiratory fitness was determined in 119 young, healthy, sedentary adults (68% women, age 21.9 ± 2.1 years, body mass index 25 ± 4.8 kg/m2) via the maximum treadmill exercise test, and their muscular strength assessed by the handgrip strength test and the 1-repetition maximum bench and leg press tests. Some days later, all subjects were exposed to 2 h of personalized exposure to cold and their cold-induced BAT volume and activity determined by a combination of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography and computed tomography scan. Cardiorespiratory fitness was associated with neither the BAT volume nor BAT activity (P ≥ 0.05). However, handgrip strength with respect to lean body mass was positively (though weakly) associated with BAT activity as represented by the 18F-FDG mean standardised uptake value (SUV) (β = 3.595, R2 = 0.039, P = 0.031) and SUVpeak value (β = 15.314, R2 = 0.037, P = 0.035). The above relationships remained after adjusting for several confounders. No other associations were found. Handgrip strength with respect to lean body mass is positively associated with BAT activity (SUVmean and SUVpeak) in young adults after exposure to cold - but only weakly. Further studies are needed to reveal the relationship between muscular fitness and human BAT characteristics.
Highlights
Humans have metabolically active brown adipose tissue (BAT)[1,2,3]
Whether cardiorespiratory fitness and muscle strength are related to BAT volume and activity remains to be investigated, but based on available evidence, it can be hypothesized that cardiorespiratory fitness is negatively associated with BAT volume and activity
No association was seen between time to exhaustion and BAT volume, BAT SUVmean or BAT SUVpeak (Fig. 1A: β = −0.006, R2 = 0.000, P = 0.850; β = −0.001, R2 = 0.006, P = 0.444; and β = −0.002, R2 = 0.003, P = 0.592, respectively)
Summary
Humans have metabolically active brown adipose tissue (BAT)[1,2,3]. Cold has been shown the main BAT-activating stimulus in humans[2,6,7], but some studies suggest that certain drugs and dietary components[8,9] may provide such a stimulus. Our group reported physical activity levels (measured via accelerometry) not to be associated with BAT volume or activity in a sedentary cohort of young, healthy adults[22]. The aim of the present work was to study the association of cardiorespiratory fitness and muscular strength with BAT volume and activity (determined via 18F-FDG uptake) after exposure to cold in young, sedentary adults
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