Clenbuterol, a β2-adrenergic agonist, reciprocally alters PGC-1 alpha and RIP140 and reduces fatty acid and pyruvate oxidation in rat skeletal muscle

Abstract

a ␤2-adrenergic agonist, reciprocally alters PGC-1 alpha and RIP140 and reduces fatty acid and pyruvate oxidation in rat skeletal muscle. Am J Physiol Regul Integr Comp Physiol 302: R373-R384, 2012. First published November 9, 2011 doi:10.1152/ajpregu.00183.2011.-Clenbuterol, a ␤2-adrenergic agonist, reduces mitochondrial content and enzyme activities in skeletal muscle, but the mechanism involved has yet to be identified. We examined whether clenbuterol-induced changes in the muscles' metabolic profile and the intrinsic capacity of mitochondria to oxidize substrates are associated with reductions in the nuclear receptor coactivator PGC-1 alpha and/or an increase in the nuclear corepressor RIP140. In rats, clenbuterol was provided in the drinking water (30 mg/l). In 3 wk, this increased body (8%) and muscle weights (12-17%). In red (R) and white (W) muscles, clenbuterol induced reductions in mitochondrial content (citrate synthase: R, 27%; W, 52%; cytochrome-c oxidase: R, 24%; W, 34%), proteins involved in fatty acid transport (fatty acid translocase/CD36: R, 36%; W, 35%) and oxidation [␤-hydroxyacyl CoA dehydrogenase (␤-HAD): R, 33%; W, 62%], glucose transport (GLUT4: R, 8%; W, 13%), lactate transport monocarboxylate transporter (MCT1: R, 61%; W, 37%), and pyruvate oxidation (PDHE1␣, R, 18%; W, 12%). Concurrently, only red muscle lactate dehydrogenase activity (25%) and MCT4 (31%) were increased. Palmitate oxidation was reduced in subsarcolemmal (SS) (R, 30%; W, 52%) and intermyofibrillar (IMF) mitochondria (R, 17%; W, 44%) along with reductions in ␤-HAD activity (SS: R, 17%; W, 51%; IMF: R, 20%; W, 57%). Pyruvate oxidation was only reduced in SS mitochondria (R, 20%; W, 28%), but this was not attributable solely to PDHE1␣, which was reduced in both SS (R, 21%; W, 20%) and IMF mitochondria (R, 15%; W, 43%). These extensive metabolic changes induced by clenbuterol were associated with reductions in PGC-1␣ (R, 37%; W, 32%) and increases in RIP140 (R, 23%; W, 21%). This is the first evidence that clenbuterol appears to exert its metabolic effects via simultaneous and reciprocal changes in the nuclear receptor coactivator PGC-1␣ and the nuclear corepressor RIP140. mitochondria; oxidative capacity CLENBUTEROL, A ␤2-ADRENERGIC agonist, induces skeletal and cardiac muscle hypertrophy, due to increased protein synthesis and a concomitant decrease in protein degradation in this tissue (2,46,50). This ␤2-adrenergic agonist is a commonly prescribed bronchodilator treatment for asthmatic patients, while its anabolic properties have led to its illegal use in animal meat production and doping in sports. Nevertheless, it has been found that the treatment with this clenbuterol provoked deleterious effects on the cardiovascular system (1) and bone mass (12), as well as impairing exercise performance (16,32). The mechanistic bases of the maladaptations induced by clenbuterol in skeletal muscle remain largely unknown.Chronic administration of clenbuterol induces the transition from slow to fast muscle fiber types (35,49,53,56) a...

Effects of Chronic Administration of Clenbuterol on Contractile Properties and Calcium Homeostasis in Rat Extensor Digitorum Longus Muscle

“…In rats, two studies have demonstrated negative effects of chronic clenbuterol treatment on exercise performance evaluated with the run-to-exhaustion treadmill [34], swimming or sprinting protocol tests [35]. Increased skeletal muscle fatigability was also reported following clenbuterol treatment in rat [7], an effect associated with reduced skeletal muscle oxidative capacity [36], [37], [38]. Moreover, muscle hypertrophy following chronic clenbuterol treatment increases the isometric force in fast-twitch skeletal muscle [7].…”

Mitochondrial dysfunction in heart failure

“…In contrast, acute excessive β-adrenergic stimulation in humans does not increase mitochondrial protein synthesis or markers of mitochondrial biogenesis in skeletal muscle [125]. Also the administration of the β2 agonist, clenbuterol, to human subjects induces skeletal and cardiac hypertrophy due to increased protein synthesis and decreased protein degradation [126], and decreases mitochondrial content and function measured as fatty acid and pyruvate oxidation by altering PGC1α signaling [127]. These observations suggest a potential contribution of adrenergic stimulation to the skeletal muscle energy deficit in HF.…”

Chronic Post-Exercise Lactate Administration with Endurance Training Increases Glycogen Concentration and Monocarboxylate Transporter 1 Protein in Mouse White Muscle

“…Red and white tibialis anterior (TA) muscle samples were homogenized as previously described (19,20) using lysis buffer (1% Triton X-100, 50 mm Tris-HCl, 1 mm EDTA, 1 mm EGTA, 50 mm sodium fluoride, 10 mm sodium beta-glycerol phosphate, 5 mm sodium pyrophosphate, and 2 mm dithiothreitol, pH 7.5) containing 10 mg/mL of pepstatin A, aprotinin, and leupeptin; 1 mm of Na orthovanadate, and 0.177 mg/mL of phenylmethylsulfonyl fluoride. Protein concentrations were measured by the Bradford method.…”