Effects of IL-15 on rat brown adipose tissue: uncoupling proteins and PPARs.
OBJECTIVE
Interleukin-15 (IL-15) plays an important role in lipid metabolism as its administration to rats causes a marked depletion of white adipose tissue (WAT). This reduction in fat mass seems to be caused by and related to hipotriglyceridemia as a result of a lower hepatic lipogenesis and an increased fatty acid oxidation. We have previously observed that IL-15 treatment induces the expression of uncoupling proteins (UCPs) in muscle. The aim of this study was to investigate the effects of IL-15 on brown adipose tissue (BAT), and in particular on genes related to lipid metabolism in this tissue.


METHODS
Male Wistar rats were treated daily with IL-15 for 7 days. Adipose tissues were collected and the mRNA content of UCPs, peroxisome proliferator-activated receptors (PPARs) and several genes implicated in fatty acid transport and oxidation were evaluated on BAT.


RESULTS
IL-15 treatment in rats causes a decrease in the mass of both WAT and BAT (35 and 24%, respectively). In BAT, an important upregulation of the mRNA content of thermogenic proteins (UCP1 and UCP3), lipid-related transcription factors (PPARdelta and PPARalpha) and other proteins implicated in membrane transport (fatty acid translocase (FAT) and fatty acid transport protein (FATP)), mitochondrial transport (carnitine palmitoyl transferase-I (CPT-I) and CPT-II) and consumption (acyl-CoA synthetase 4 (ACS4)) of fatty acids was observed as a consequence of the treatment.


CONCLUSIONS
The changes observed in BAT suggest that IL-15 could be implicated in lipid consumption in this tissue by regulating lipid oxidation and probably thermogenesis, processes mediated by UCPs and PPARs.
Almendro
Vanessa
V
Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Barcelona, Barcelona, Spain.
Fuster
Gemma
G
Busquets
Sílvia
S
Ametller
Elisabet
E
Figueras
Maite
M
Argilés
Josep M
JM
López-Soriano
Francisco J
FJ
D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D005227:Fatty Acids / Q000378:metabolism; D019409:Interleukin-15 / Q000502:physiology*; D007473:Ion Channels / Q000378:metabolism*; D050356:Lipid Metabolism / Q000502:physiology; D008297:Male; D024101:Mitochondrial Proteins / Q000378:metabolism*; D010084:Oxidation-Reduction; D047493:PPAR alpha / Q000378:metabolism*; D047494:PPAR delta / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D022722:Thermogenesis / Q000502:physiology; D000071256:Uncoupling Protein 1; D000071247:Uncoupling Protein 3
D005227:Fatty Acids; D019409:Interleukin-15; D007473:Ion Channels; D024101:Mitochondrial Proteins; D047493:PPAR alpha; D047494:PPAR delta; D012333:RNA, Messenger; C000604373:Ucp1 protein, rat; C000604394:Ucp3 protein, rat; D000071256:Uncoupling Protein 1; D000071247:Uncoupling Protein 3