Recruited brown adipose tissue as an antiobesity agent in humans

Abstract

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.

Figure 1. Contribution of BAT to whole-body EE.

(A and B) FDG-PET/CT images of subjects with detectable (A) and undetectable (B) activities of BAT. (C) Whole-body EE at 27°C and after 2-hour cold exposure at 19°C. (D) CIT. (E) Fat-free mass. (F–H) Relationships of fat-free mass to EE at 27°C (F), EE at 19°C (G) and CIT (H). (I) BAT activity. (J–L) Relationship of BAT activity to EE at 27°C (J), EE at 19°C (K), and CIT (L). *P < 0.05; **P < 0.01; ***P < 0.001.

Figure 2. BAT recruitment by chronic cold exposure.

FDG-PET/CT images (A) and BAT activity (B) of 8 subjects before and after the 6-week daily cold exposure. SUV of both sides of the neck was plotted.

Figure 3. Effects of chronic stimulation by cold and capsinoids.

(A and B) Body composition after cold (A) and capsinoid (B) stimulation. An outlier (×) was excluded from the analysis. (C) Change in body fat mass after repeated cold exposure. (D and E) CIT after repeated cold exposure (D) and daily ingestion of capsinoids (E). (F and G) Relationships of repeated cold-induced change in BAT activity (data as in Figure 2B) to those in body fat mass (F) and CIT (G). (H) Relationship between repeated cold-induced changes in CIT and body fat mass. *P < 0.05; **P < 0.01.