Brown adipose tissue (BAT), which mediates non-shivering thermogenesis, contributes to whole body energy expenditure and weight regulation in rodents. Given the tissue's high energy consumption, understanding the mechanisms that drive BAT recruitment and activation could be useful in the development of novel anti-obesity therapies. In this episode of Author's Take, Takeshi Yoneshiro and Masayuki Saito discuss their recent study in which subjects exposed subjects to a daily cold stimulus for 6 weeks had increased BAT activation and reduced overall fat mass. Yoneshiro and colleagues also observed that treatment with capsinoids, the spicy compounds found in chili peppers, resulted in BAT accumulation and increased energy expenditure in individuals who previously had low or undetectable BAT. These results suggest that methods to increase BAT levels could be used to fight obesity.
Brown adipose tissue (BAT) burns fat to produce heat when the body is exposed to cold and plays a role in energy metabolism. Using fluorodeoxyglucose-positron emission tomography and computed tomography, we previously reported that BAT decreases with age and thereby accelerates age-related accumulation of body fat in humans. Thus, the recruitment of BAT may be effective for body fat reduction. In this study, we examined the effects of repeated stimulation by cold and capsinoids (nonpungent capsaicin analogs) in healthy human subjects with low BAT activity. Acute cold exposure at 19°C for 2 hours increased energy expenditure (EE). Cold-induced increments of EE (CIT) strongly correlated with BAT activity independently of age and fat-free mass. Daily 2-hour cold exposure at 17°C for 6 weeks resulted in a parallel increase in BAT activity and CIT and a concomitant decrease in body fat mass. Changes in BAT activity and body fat mass were negatively correlated. Similarly, daily ingestion of capsinoids for 6 weeks increased CIT. These results demonstrate that human BAT can be recruited even in individuals with decreased BAT activity, thereby contributing to body fat reduction.
Takeshi Yoneshiro, Sayuri Aita, Mami Matsushita, Takashi Kayahara, Toshimitsu Kameya, Yuko Kawai, Toshihiko Iwanaga, Masayuki Saito