Peroxisome proliferator-activated receptor alpha (PPARalpha) activators, bezafibrate and Wy-14,643, increase uncoupling protein-3 mRNA levels without modifying the mitochondrial membrane potential in primary culture of rat preadipocytes.
Uncoupling proteins (UCPs) are inner mitochondrial membrane transporters which act as pores for H(+) ions, dissipating the electrochemical gradient that develops during mitochondrial respiration at the expense of ATP synthesis. We have studied the effects of two fibrates, bezafibrate and Wy-14,643, on UCP-3 and UCP-2 mRNA levels in primary monolayer cultures of rat adipocytes and undifferentiated preadipocytes. Treatment with both PPARalpha activators for 24 h up-regulated UCP-3 mRNA levels. Thus, bezafibrate treatment resulted in an 8-fold induction in UCP-3 mRNA levels in preadipocytes compared with the 3.5-fold induction observed in adipocytes. Differences in the induction of UCP-3 between these cells correlated well with the higher expression of PPARalpha and RXRalpha mRNA values in preadipocytes compared to adipocytes. Wy-14,643 caused similar effects on UCP-3 mRNA expression. In contrast to UCP-3, UCP-2 mRNA levels were only slightly modified by bezafibrate in adipocytes. The induction in UCP-3 expression was not accompanied by changes in the mitochondrial membrane potential of rat primary preadipocytes after bezafibrate or Wy-14,643 treatment. Since it has been proposed that UCP-3 could be involved in the regulation of the use of fatty acids as fuel substrates, the UCP-3 induction achieved after bezafibrate and Wy-14, 643 treatment may indicate a higher oxidation of fatty acids, limiting their availability to be stored as triglycerides. This change may result in a reduced rate of conversion of preadipocytes to adipocytes, which directly affects fat depots.
Unidad de Farmacología, Núcleo Universitario de Pedralbes, Barcelona, E-08028, Spain.
A
A
Cabrero
M
M
Alegret
R
R
Sánchez
T
T
Adzet
J C
JC
Laguna
M
M
Vázquez
D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D001629:Bezafibrate / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics*; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D007473:Ion Channels; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins; D020025:Peroxisome Proliferators / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D000071247:Uncoupling Protein 3
D002352:Carrier Proteins; D017931:DNA Primers; D007473:Ion Channels; D024101:Mitochondrial Proteins; D020025:Peroxisome Proliferators; D011743:Pyrimidines; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; C000604394:Ucp3 protein, rat; D000071247:Uncoupling Protein 3; C006253:pirinixic acid; D001629:Bezafibrate