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Cell Rep. 2013 Dec 12;5(5):1196-203. doi: 10.1016/j.celrep.2013.10.044. Epub 2013 Nov 27.

UCP1 in brite/beige adipose tissue mitochondria is functionally thermogenic.

Author information

1
Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden.
2
Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden. Electronic address: jan@metabol.su.se.

Abstract

The phenomenon of white fat "browning," in which certain white adipose tissue depots significantly increase gene expression for the uncoupling protein UCP1 and thus supposedly acquire thermogenic, fat-burning properties, has attracted considerable attention. Because the mRNA increases are from very low initial levels, the metabolic relevance of the change is unclear: is the UCP1 protein thermogenically competent in these brite/beige-fat mitochondria? We found that, in mitochondria isolated from the inguinal "white" adipose depot of cold-acclimated mice, UCP1 protein levels almost reached those in brown-fat mitochondria. The UCP1 was thermogenically functional, in that these mitochondria exhibited UCP1-dependent thermogenesis with lipid or carbohydrate substrates with canonical guanosine diphosphate (GDP) sensitivity and loss of thermogenesis in UCP1 knockout (KO) mice. Obesogenic mouse strains had a lower thermogenic potential than obesity-resistant strains. The thermogenic density (UCP1-dependent oxygen consumption per g tissue) of inguinal white adipose tissue was maximally one-fifth of interscapular brown adipose tissue, and the total quantitative contribution of all inguinal mitochondria was maximally one-third of all interscapular brown-fat mitochondria, indicating that the classical brown adipose tissue depots would still predominate in thermogenesis.

PMID:
24290753
DOI:
10.1016/j.celrep.2013.10.044
[Indexed for MEDLINE]
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