Brown adipose tissue: physiological function and evolutionary significance

The heat-stable modulators of phosphoprotein phosphatase activity have been partially purified from brown adipose tissue. A nonphosphorylatable inhibitor of phosphorylase phosphatase (inhibitor 2) and an activator of phosphohistone phosphatase were similar to the corresponding modulators from muscle and liver in both their physical properties and in their relative effects upon three different preparations of phosphatase. An inhibitor of phosphorylase phosphatase that was only active when phosphorylated was eluted from DEAE-cellulose by 80 mM NaCl (inhibitor 1′). Only a small amount of inhibitor was eluted at 20 mM NaCl (inhibitor 1), which is the concentration that eluted the bulk of the phosphorylatable inhibitor in muscle and liver. Inhibitor 1 and inhibitor 1′ had similar physical properties but differed in their activities towards the different phosphatases. It is suggested that they are different forms of the same protein and that inhibitor 1′ more closely resembles the native inhibitor. The modulators did not compete with each other and were probably not subunits of a phosphatase complex. However, the direction and timing of the changes in their concentration in brown fat during the developmental period indicate that the inhibitors, at least, perform some useful physiological function in the tissue. The concentration of inhibitor 2 was high before birth and for 10 days after birth, when the tissue was proliferating. The concentration of the phosphorylatable inhibitor was highest immediately after birth and for the next 16 days, which is the period of greatest thermogenic activity of brown fat.

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Functional characterization of human brown adipose tissue metabolism

Biochemical Journal ◽

10.1042/bcj20190464 ◽

2020 ◽

Vol 477 (7) ◽

pp. 1261-1286 ◽

Cited By ~ 3

Author(s):

Marie Anne Richard ◽

Hannah Pallubinsky ◽

Denis P. Blondin

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Functional Characterization ◽

Human Infants ◽

Positron Emission ◽

Brown Adipose ◽

Treatment Of Obesity ◽

And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

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