ToxSci Advance Access published online on June 30, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn130
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PPAR alpha, more than PPAR delta, mediates the hepatic and skeletal muscle alterations induced by the PPAR agonist GW0742


* Safety Assessment Department, GlaxoSmithKline, Research Triangle Park, NC 27709 USA; Brenda.X.Faiola{at}gsk.com, James.G.Falls{at}gsk.com, Richard.A.Peterson{at}gsk.com, Connie.A.Cummings{at}gsk.com, Beth.H.Romach{at}gsk.com, Richard.T.Miller{at}gsk.com
Department of Toxicology, Alcon Research Labs, Fort Worth, TX 76134 USA; Nancy.Bordelon{at}AlconLabs.com
Safety Assessment Department, GlaxoSmithKline, The Frythe, UK; Brodies3{at}yahoo.com
Corresponding author: Brenda Faiola, PhD, DABT, PO Box 13398, 5 Moore Dr., Research Triangle Park, NC 27709, Phone: 919-483-5075, Fax: 919-483-6858, e-mail: Brenda.x.Faiola{at}gsk.com
Received April 1, 2008; revision received June 16, 2008; accepted June 23, 2008
| Abstract |
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Therapeutic use of certain peroxisome proliferator-activated receptor (PPAR) alpha agonists (fibrates) for the treatment of dyslipidemia has infrequently been associated with the untoward side effect of myopathy. With interest in PPAR
as a therapeutic target, this study assessed whether a PPAR
agonist induced similar hepatic and skeletal muscle alterations as noted with some fibrates. PPAR
null (KO) and corresponding wild type (WT) mice were administered toxicological dosages of a potent PPAR
agonist tool ligand (GW0742; which also has weak PPAR
agonist activity) or a potent PPAR
agonist (WY–14,643) for 10 days. Increases in liver weights and clinical chemistry indicators of skeletal muscle damage and/or liver injury were more pronounced in WT mice compared with KO mice administered the PPAR
agonist. Likewise, the incidence and severity of skeletal myopathy were greater in WT mice given GW0742 compared with KO mice. Ultrastructural and immunohistochemical analyses revealed significant peroxisome proliferation in muscle and liver of WT mice treated with each agonist; however, KO animals showed little or no evidence of hepatic and muscle peroxisome proliferation. PMP-70 protein expression in liver was consistent with these results. The hepatomegaly, hepatic and skeletal muscle peroxisome proliferation, and skeletal myopathy induced by this PPAR
ligand was predominantly mediated by its cross-activation of PPAR
, though PPAR
agonism contributed slightly to these effects.
Key Words: Peroxisome proliferator-activated receptor; myopathy; mice.
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