Brown and beige fat in humans: thermogenic adipocytes that control energy and glucose homeostasis
Labros Sidossis, Shingo Kajimura
Labros Sidossis, Shingo Kajimura
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Review

Brown and beige fat in humans: thermogenic adipocytes that control energy and glucose homeostasis

Abstract

Brown adipose tissue (BAT), a specialized fat that dissipates energy to produce heat, plays an important role in the regulation of energy balance. Two types of thermogenic adipocytes with distinct developmental and anatomical features exist in rodents and humans: classical brown adipocytes and beige (also referred to as brite) adipocytes. While classical brown adipocytes are located mainly in dedicated BAT depots of rodents and infants, beige adipocytes sporadically reside with white adipocytes and emerge in response to certain environmental cues, such as chronic cold exposure, a process often referred to as “browning” of white adipose tissue. Recent studies indicate the existence of beige adipocytes in adult humans, making this cell type an attractive therapeutic target for obesity and obesity-related diseases, including type 2 diabetes. This Review aims to cover recent progress in our understanding of the anatomical, developmental, and functional characteristics of brown and beige adipocytes and discuss emerging questions, with a special emphasis on adult human BAT.

Authors

Labros Sidossis, Shingo Kajimura

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Figure 2

Developmental origins of brown and beige adipocytes.

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Developmental origins of brown and beige adipocytes. (A) Classical brown...
(A) Classical brown adipocytes originate from a subset of dermomyotomes that express En1, Pax7, and Myf5. Classical brown adipocytes express several markers, including Ucp1, Pgc1a, and Cidea, and classical brown-selective markers, such as Zic1. (B) Beige adipocytes in WAT originate from MYF5-negative PDGFRα-positive precursors of mesodermes. A subset of beige adipocytes arises from MYH11-positive smooth muscle–like precursors. Beige adipocyte differentiation is induced by environmental cues, such as chronic cold exposure, exercise, and PPARγ agonists. Beige adipocytes express several markers, including Ucp1, Pgc1a, and Cidea, and beige-selective markers, such as Cd137, Tbx1, Tmed26, and Cited1. These cells may be derived from (i) defined beige precursors, (ii) directed differentiation from white precursors, or (iii) transdifferentiation from white adipocytes in a differentiated state. The dashed lines represent hypothetical models that require further investigation.