5/12/2023 0 Comments Human japanese activation keyResults and DiscussionĪcute effects of cold exposure on BAT thermogenesis. This is the first report of successful recruitment of BAT leading to reduced body fat in humans. Our results showed that human BAT could be recruited even in individuals who had lost BAT, thereby contributing to body fat reduction. The present study explored how to reactivate and recruit human BAT by examining the effects of chronic stimulation by cold and capsinoids on BAT in healthy adults with low or undetectable activities of BAT. Stimulation of TRP channels by capsinoids is effective for enhancement of BAT thermogenesis and upregulation of uncoupling protein 1 (UCP1), a key molecule of BAT thermogenesis, in mice ( 14). This pathway is also activated by some food ingredients, such as capsaicin and capsinoids, nonpungent capsaicin analogs ( 13, 14). It is known that the stimulatory effects of cold on BAT are mediated through the activation of the sympathetic nervous system, initiated by peripheral stimulation of transient receptor potential (TRP) channels in sensory neurons ( 8, 12). ( 7) reported increased BAT activity after weight loss in obese patients given gastric banding surgery, suggesting the effectiveness of successful recruitment of BAT in body fat reduction in humans.Ĭold exposure is the most powerful and physiological stimulus for BAT activation, both in small rodents and in humans ( 2, 8– 11). It is therefore expected that the reactivation and/or recruitment of BAT may protect against the onset of obesity and related metabolic disorders in humans. We previously reported that the body fat content of subjects with undetectable activities of BAT increased with age, while those of subjects with detectable activities of BAT remained unchanged from 20s to 40s ( 6), which suggests that the age-related decrease in BAT activity accelerates the accumulation of body fat. The prevalence and activity of human BAT, as assessed by FDG-PET/CT, are inversely related to body fat content and decrease with age ( 2– 4). Recent studies using fluorodeoxyglucose-PET (FDG-PET) in combination with CT revealed that adult humans have considerable amounts of BAT ( 2– 5). Introductionīrown adipose tissue (BAT), a site of nonshivering thermogenesis, shows promise in combating obesity, since it contributes to the regulation of whole-body energy expenditure (EE) and body fat content in small rodents ( 1). These results demonstrate that human BAT can be recruited even in individuals with decreased BAT activity, thereby contributing to body fat reduction. Similarly, daily ingestion of capsinoids for 6 weeks increased CIT. Changes in BAT activity and body fat mass were negatively correlated. Daily 2-hour cold exposure at 17☌ for 6 weeks resulted in a parallel increase in BAT activity and CIT and a concomitant decrease in body fat mass. Cold-induced increments of EE (CIT) strongly correlated with BAT activity independently of age and fat-free mass. Acute cold exposure at 19☌ for 2 hours increased energy expenditure (EE). 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. Thus, the recruitment of BAT may be effective for body fat reduction. 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. The combined results suggest that a variable indoor environment with frequent cold exposures might be an acceptable and economic manner to increase energy expenditure and may contribute to counteracting the current obesity epidemic.īrown adipose tissue (BAT) burns fat to produce heat when the body is exposed to cold and plays a role in energy metabolism. The observed physiological acclimation is in line with the subjective changes in temperature sensation upon cold acclimation, the subjects judged the environment warmer, felt more comfortable in the cold, and reported less shivering. Based on cell-specific markers and on uncoupling protein-1 (characteristic of both BAT and beige/brite cells), this study did not show “browning” of abdominal subcutaneous white adipose tissue upon cold acclimation. Respiration measurements in permeabilized fibers and isolated mitochondria revealed no significant contribution of skeletal muscle mitochondrial uncoupling to the increased NST. No sex differences in BAT presence and activity were found either before or after cold acclimation. Here, we show that a 10-day cold acclimation protocol in humans increases BAT activity in parallel with an increase in nonshivering thermogenesis (NST). In recent years, it has been shown that humans have active brown adipose tissue (BAT) depots, raising the question of whether activation and recruitment of BAT can be a target to counterbalance the current obesity pandemic.
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