Mice in which peroxisome proliferator-activated receptor beta (PPARbeta) is selectively ablated in skeletal muscle myocytes were generated to elucidate the role played by PPARbeta signaling in these myocytes. These somatic mutant mice exhibited a muscle fiber-type switching toward lower oxidative capacity that preceded the development of obesity and diabetes, thus demonstrating that PPARbeta is instrumental in myocytes to the maintenance of oxidative fibers and that fiber-type switching is likely to be the cause and not the consequence of these metabolic disorders. We also show that PPARbeta stimulates in myocytes the expression of PGC1alpha, a coactivator of various transcription factors, known to play an important role in slow muscle fiber formation. Moreover, as the PGC1alpha promoter contains a PPAR response element, the effect of PPARbeta on the formation and/or maintenance of slow muscle fibers can be ascribed, at least in part, to a stimulation of PGC1alpha expression at the transcriptional level.
To generate temporally controlled targeted somatic mutations selectively and efficiently in skeletal muscles, we established a transgenic HSA-Cre-ER(T2) mouse line in which the expression of the tamoxifen-dependent Cre-ER(T2) recombinase is under the control of a large genomic DNA segment of the human skeletal muscle alpha-actin gene, contained in a P1-derived artificial chromosome. In this transgenic line Cre-ER(T2) is selectively expressed in skeletal muscles, and Cre-ER(T2)-mediated alteration of LoxP flanked (floxed) target genes is skeletal muscle-specific and strictly tamoxifen-dependent. HSA-Cre-ER(T2) mice should be of great value to analyze gene function in skeletal muscles, and to establish animal models of human skeletal muscle disorders.
Summary The two p160 transcriptional co-regulator family members SRC-1 and TIF2 have important metabolic functions in white and brown adipose tissues, as well as in the liver. To analyze TIF2 cell-autonomous functions in skeletal muscles, we generated TIF2(i)skm-/- mice, in which TIF2 was selectively ablated in skeletal muscle myofibers at adulthood. We found that increased mitochondrial uncoupling in skeletal muscle myocytes protected these mice from decreased muscle oxidative capacities induced by sedentariness, delayed the development of type 2 diabetes and attenuated high caloric diet-induced obesity. Moreover, our results demonstrate that SRC-1 and TIF2 can modulate the expression of the uncoupling protein UCP3 in an antagonistic manner, and that enhanced SRC-1 levels in TIF2-deficient myofibers are critically involved in the metabolic changes of TIF2(i)skm-/- mice. Thus, modulation of the expression and/or activity of these co-regulators represents an attractive way to prevent or treat metabolic disorders.
To cite this article: Bura A, Bachelot-Loza C, Dali Ali F, Aiach M, Gaussem P. Role of the P2Y 12 gene polymorphism in platelet responsiveness to clopidogrel in healthy subjects. J Thromb Haemost 2006;4: 2096-7. Clopidogrel is an inhibitor of platelet function. Its active metabolite irreversibly blocks the platelet ADP receptor P2Y 12 [1] and prevents ischemic events in patients with atherosclerosis [2]. The antiplatelet effect of clopidogrel shows wide interindividual variability and in 5-30% of patients the recommended dose of 75 mg day )1 fails to inhibit platelet aggregation ex vivo [3][4][5]. We examined the role of the gain-of-function polymorphism (H2 allele) of the P2Y 12 gene [6], which encodes the clopidogrel target receptor, in the extent of clopidogrel pharmacodynamic response.To investigate the possible influence of the H2 allele free from confounding factors, such as medications or cardiovascular diseases, we evaluated clopidogrel responsiveness in young healthy subjects during a 1-week oral course of clopidogrel 75 mg day . Among 225 Caucasian men aged 18-35 years screened for the H1H2 genotype [7], we consecutively included 29 healthy volunteers (14 H1H1, 11 H1H2, and 4 H2H2). The study was approved by the Paris-Cochin ethics committee and all the subjects gave their written informed consent. The volunteers were asked to come to the Clinical Investigations Center each day at 09:00 hours where they were given a standard dose of clopidogrel 75 mg once daily for 7 days in the presence of medical staff. Blood samples for pharmacodynamic studies were drawn just before the first clopidogrel intake on days 1, 2, 3, 4, 5, and 7, and on days 9, 10, 11, and 14. Platelet response to 10 lmol L )1 ADP was evaluated with platelet aggregation and vasodilator-stimulated phosphoprotein (VASP) phosphorylation, which is specific for P2Y 12 inhibition. Aggregation studies were performed at baseline, on treatment, and after treatment completion at 37°C using a photometric method on a four-channel aggregometer (Regulest, Amneville, France). ADP-induced aggregation (10 lmol L )1 final concentration, Sigma-Aldrich, St-Quentin Fallavier, France) was reported as maximal aggregation or as a percentage of baseline aggregation. VASP was measured in whole blood at baseline, on day 4 and on day 7 of clopidogrel intake using a flow cytometric assay (Platelet VASPÒ, Diagnostica Stago, Biocytex, Marseille, France) adapted to a Cy-Flow apparatus (Partec GmbH, SteGenevie`ve-des-Bois, France 78.0) in H1H2 subjects; and 79.0% (IQR 76.5; 81.0) in H2H2 subjects (P ¼ 0.25). The aggregation fell significantly between days 1 and 7 of clopidogrel intake in the whole population [median at day 7 (IQR): 54% (45.5; 65.5), P < 0.0001], but the response did not differ between H1H1 subjects and H1H2 + H2H2 subjects (P ¼ 0.58). However, while median platelet aggregation significantly fell in H1H1 [54% (46; 68)] and H1H2 [49% (29; 59)] groups on day 7 of clopidogrel intake, no significant fall occurred in the H2H2 subjects [76% (65; 82), P < 0...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.