Metoprolol represses PGC1alpha-mediated carnitine palmitoyltransferase-1B expression in the diabetic heart.
We have previously shown that metoprolol decreases carnitine palmitoyltransferase-1 (CPT-1) activity, a mechanism which may partly explain its beneficial effects in heart failure. It is possible that this effect occurs as a result of repression of cardiac CPT-1B expression. CPT-1B is induced by the transcription factors peroxisome proliferator activated receptor-alpha (PPAR-alpha) and PPAR-gamma-coactivator 1alpha (PGC1alpha) and repressed by upstream stimulatory factor-2 (USF-2). We therefore hypothesized that metoprolol represses CPT-1B by increasing USF-2-mediated repression of PGC1alpha. Male Wistar Rats were divided into 4 groups: control, control treated with metoprolol for 5 weeks, diabetic and diabetic treated with metoprolol for 5 weeks. After termination, the expression of CPT-1 isoforms, PPAR-alpha, PGC1alpha USF-1 and USF-2, as well as downstream targets were measured. Binding of PPAR-alpha, PGC1alpha and USF-2 to PGC1alpha was measured using coimmunoprecipitation. The occupation of PPAR-alpha and MEF-2A consensus sites in the CPT-1B promoter was measured using chromatin immunoprecipitation assays. Chronic metoprolol treatment decreased the expression of CPT-1B in diabetic hearts. The expression of USF-2 was increased by metoprolol in both control and diabetic hearts, but the association of USF-2 with PGC1alpha was increased by metoprolol only in diabetic hearts. Metoprolol prevented the increase in PGC1alpha occupation of the CPT-1B promoter region observed in the diabetic heart without affecting PPAR-alpha occupation. Metoprolol decreases CPT-1B expression by decreasing PGC1alpha-mediated coactivation of PPAR-alpha and MEF-2A. This is associated with increased PGC1alpha/ USF-2 binding, suggesting that USF-2 mediates the metoprolol-induced repression of PGC1alpha.
Sharma
Vijay
V
Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, Canada.
Dhillon
Pavan
P
Parsons
Hannah
H
Allard
Michael F
MF
McNeill
John H
JH
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000187:drug effects* / Q000235:genetics; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D047468:Immunoprecipitation / Q000379:methods; D026161:MADS Domain Proteins / Q000187:drug effects / Q000378:metabolism; D064326:MEF2 Transcription Factors; D008297:Male; D008790:Metoprolol / Q000008:administration & dosage / Q000494:pharmacology*; D018006:Myogenic Regulatory Factors / Q000187:drug effects / Q000378:metabolism; D047493:PPAR alpha / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D020033:Protein Isoforms; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism; D051720:Upstream Stimulatory Factors / Q000187:drug effects / Q000235:genetics
D000319:Adrenergic beta-Antagonists; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; C578037:MEF2A protein, rat; D018006:Myogenic Regulatory Factors; D047493:PPAR alpha; D020033:Protein Isoforms; D014157:Transcription Factors; D051720:Upstream Stimulatory Factors; C497187:Usf2 protein, rat; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; D002334:Carnitine O-Palmitoyltransferase; D008790:Metoprolol