Editors' ChoiceMetabolism

Red Hot Chili Peppers Rock Obesity Research

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Science Translational Medicine  24 Jul 2013:
Vol. 5, Issue 195, pp. 195ec123
DOI: 10.1126/scitranslmed.3006986

Brown fat, a heat-producing organ in human infants and hibernating mammals, was shown recently to be present in human adults and to participate in energy expenditure. Although brown fat seems to be a logical target for obesity treatments that enhance the organ’s ability to burn energy, disappointing studies show that most obese people display undetectable levels of brown-fat metabolism. Now, a study by Yoneshiro et al. shows that hope remains in the quest to target brown fat for weight loss.

The authors treated participants who displayed low or undetectable brown-fat metabolism (as assessed by fluorodeoxyglucose positron emission tomography) with 6 weeks of daily exposure to cold (17°C for 2 hours), which resulted in significant activation of brown fat—and thus energy expenditure—in 50% of the study participants. These individuals lost an average of 5.2% of their body fat mass over a 6-week period after cold treatment. Cold exposure is known to be a powerful physiological stimulus for brown-fat metabolism, which is mediated through activation of the sympathetic nervous system by transient receptor potential (TRP) channels in the periphery. Capsinoids—small molecules that are naturally present in red chili peppers—were also shown to activate TRP channels in both in vitro and in animal models and, therefore, might mimic the effect of cold exposure on activation of brown fat. Indeed, daily ingestion of capsinoids for 6 weeks resulted in an increase in brown-fat metabolic activity and energy expenditure among a second cohort with low or undetectable brown-fat activity before treatment.

This study demonstrates loss of body fat in humans by recruitment of brown fat and provides a rationale for long-term studies to assess the safety and efficacy of capsinoid therapeutics as a weight-loss strategy. Although chronic exposure to cold is not a practical treatment approach, an odorless and tasteless chili-pepper extract may be a convenient alternative.

T. Yoneshiro et al., Recruited brown adipose tissue as an antiobesity agent in humans. J. Clin. Invest., published online 15 July 2013 (10.1172/JCI67803). [Full Text]

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