Brown adipose tissue oxidative metabolism contributes to energy expenditure during acute cold exposure in humans : Dr. Carpentier

Brown adipose tissue oxidative metabolism contributes to energy expenditure during acute cold exposure in humans

Author Interview: André Carpentier MD FRCPC

Professor Department of Medicine
CIHR-GSK Chair in Diabetes
Centre de recherche clinique Etienne-Le Bel
Université de Sherbrooke

What are the main findings of the study?

The main findings are that healthy men when exposed to cold can significantly increase their caloric expenditure through activation of ‘fat burning’ in the brown fat.

We designed our experiments to minimize shivering in our participants so that energy expenditure from this source is minimized. We quantified brown fat glucose and fat uptake from circulation during the experiments and found that a very small part of the 250 extra kilocalories burned during the 3-hour cold exposure was accounted by these sources. However, there was a significant reduction of the fat stored inside brown fat during the experiment. Furthermore, the more brown fat an individual has, the less the need to shiver to expand the same amount of calories.

Were any of the finding unexpected? 

Unexpected? I was personally sceptical that such a small tissue (brown fat is about 1 to 3% of the total amount of fat in the body) can significantly contribute to energy expenditure. I became convinced by our experimental data. This was a very controversial and unproven issue in humans, although we had solid evidence in small animals thatbrown adipose tissue contribution to energy expenditure can be very important.

What should clinicians and patients take home from your study?

Take home: Please don’t throw yourself naked in the snow and don’t buy expensive cooling devices in the hope to lose weight!

Much more study is needed to determine whether this mechanism can be safely maintained over time and successfully used to tip the balance away from chronic caloric excess. We need to determine how to accomplish this safely in humans.

We also need to find out the potential long-term adaptations of the body in that instance (i.e. whether there would be compensatory increase in energy intake or other counter adaptation of the body to prevent weight loss in that instance).

Ours is a proof-of-concept study. Now we have a potential target to work on. It is only the start. Turning down the heat in your apartment is good to the environment and for your wallet. However, it is premature to claim it would be good for your waist as well.

What  further research are you planning as a result of this study?

This study is funded by the Canadian Diabetes Association. With my colleagues Dr Denis Richard from Laval University, François Haman from University of Ottawa, and Eric Turcotte from University of Sherbrooke, we will now repeat these experiments in subjects with diabetes to determine whether their brown fat display abnormal metabolism and fat burning capacity.

We already know that people with diabetes have less spontaneously active brown fat when assessed by looking at glucose uptake in that tissue. We don’t known whether this means that all brown fat metabolism is lower in these individuals. We don’t know the mechanism of this finding either. We are setting up to do these experiments.

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