Fifty shades of brown: The functions, diverse regulation and evolution of brown adipose tissue

When the cold gets under your skin: Evidence for brown adipose tissue activity in Samoan adults

OBJECTIVES

Brown adipose tissue (BAT) is a heat-producing organ aiding nonshivering thermogenesis (NST) during cold stress. Due to its potential cold-adaptive role BAT has been predominantly studied in cold and temperate climate populations, but not among warm-climate adults. This work explores if BAT activity can be inferred in Samoans.

MATERIALS AND METHODS

We inferred BAT activity by comparing metabolic rate and surface heat dissipation using indirect calorimetry and thermal imaging between room temperature and cold exposure among Samoans (N = 61, females: n = 38) from 'Upolu Island, Samoa. BAT activity was inferred using ANOVA linear regression models with the variables measured at cold exposure as outcomes. T-tests were used to compare changes in surface temperature between room temperature and cold exposure.

RESULTS

Metabolic rate significantly increased after cooling. In both the supraclavicular area, a known BAT location, and the sternum, a non-BAT location, temperatures decreased significantly upon cold exposure. Differences in supraclavicular temperatures between room temperature and cold were significantly smaller than differences in sternum temperatures between exposures. These results suggest that BAT thermogenesis occurred in known BAT-locations and thus contributed to NST during cooling.

CONCLUSIONS

This study adds to our understanding of BAT activity across different populations and climates. Further study may illuminate whether the cold-adaptive properties of BAT may have played a role in the successful expansion of populations across the globe, including warm-climate groups.

Beyond BMI

This review examined the origins of the concept of the BMI in the work of Quetelet in the 19th century and its subsequent adoption and use in tracking the course of the pandemic of obesity during the 20th century. In this respect, it has provided a valuable international epidemiological tool that should be retained. However, as noted in this review, the BMI is deficient in at least three ways. First, it does not measure body fat distribution, which is probably a more important guide to the risk of excess adiposity than the BMI itself. Second, it is not a very good measure of body fat, and thus its application to the diagnosis of obesity or excess adiposity in the individual patient is limited. Finally, the BMI does not provide any insights into the heterogeneity of obesity or its genetic, metabolic, physiological or psychological origins. Some of these mechanisms are traced in this review.

Brown Adipose Tissue: New Challenges for Prevention of Childhood Obesity. A Narrative Review

Pediatric obesity remains a challenge in modern society. Recently, research has focused on the role of the brown adipose tissue (BAT) as a potential target of intervention. In this review, we revised preclinical and clinical works on factors that may promote BAT or browning of white adipose tissue (WAT) from fetal age to adolescence. Maternal lifestyle, type of breastfeeding and healthy microbiota can affect the thermogenic activity of BAT. Environmental factors such as exposure to cold or physical activity also play a role in promoting and activating BAT. Most of the evidence is preclinical, although in clinic there is some evidence on the role of omega-3 PUFAs (EPA and DHA) supplementation on BAT activation. Clinical studies are needed to dissect the early factors and their modulation to allow proper BAT development and functions and to prevent onset of childhood obesity.