Stimulation of uncoupling protein 1 expression in brown adipocytes by naturally occurring carotenoids.
OBJECTIVE
To assess the effect of naturally occurring carotenoids on brown adipocyte proliferation and differentiation. The rationale behind is that certain carotenoids have provitamin A activity in mammals, and that one of the active forms of vitamin A, (retinoic acid) is known to behave as a transcriptional activator of the key gene for brown fat thermogenesis, the one encoding the uncoupling protein thermogenin (UCP1).


METHODS
Confluent primary cultures of mice brown adipocytes were treated with various concentrations of carotenoids. Cell morphology, total culture protein content, the DNA synthesis rate, and the levels of UCP1, retinoic acid receptor alpha (RARalpha) and retinoid X receptor alpha (RXRalpha) were analysed.


RESULTS
Treatment with beta-carotene, alpha-carotene and lutein promoted UCP1 expression in a dose-dependent manner, with an effectiveness that was related to their potency as vitamin A precursors. Cell morphology, total culture protein content at confluence and DNA synthesis rate were unaffected after carotenoid treatment up to 10 microM.


CONCLUSIONS
The results indicate that carotenoids can positively affect the expression of UCP1 without altering brown adipocyte proliferation.
Dept. Biologia Fonamental i Ciéncies de la Salut, Universitat de les Illes Balears, Valldemossa, Palma de Mallorca, Spain.
F
F
Serra
M L
ML
Bonet
P
P
Puigserver
J
J
Oliver
A
A
Palou
D017667:Adipocytes / Q000378:metabolism; D002001:Adipose Tissue, Brown / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002338:Carotenoids / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002455:Cell Division; D002478:Cells, Cultured; D007473:Ion Channels; D014975:Lutein / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D024101:Mitochondrial Proteins; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D014157:Transcription Factors / Q000378:metabolism; D000071256:Uncoupling Protein 1; D019207:beta Carotene / Q000378:metabolism
D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D014157:Transcription Factors; C000604372:Ucp1 protein, mouse; D000071256:Uncoupling Protein 1; D019207:beta Carotene; D002338:Carotenoids; D014975:Lutein