Influence of clenbuterol on bone metabolism in exercised or sedentary rats

Abstract

This paper reports that the selective beta(2)-adrenergic receptor agonist clenbuterol affects bone metabolism in growing 3-mo-old male Wistar rats treated over 8 wk. Thirty-two 3-mo-old growing Wistar rats weighing 234 +/- 2 g were assigned to a progressive isometric force, strength-training exercise program plus oral clenbuterol (2 mg x kg body wt(-1) x day(-1)) for 5 days each week, exercise program without clenbuterol 5 days each week, no exercise program plus oral clenbuterol (2 mg x kg(-1) x day(-1)) for 5 days each week, or no exercise without clenbuterol 5 days each week. At the end of 8 wk, lean mass, fat mass, and right total femoral, distal metaphyseal femoral, and diaphyseal femoral bone mineral density were measured by Hologic QDR 4,500 dual X-ray absorptiometry (DEXA) technique. Left femoral bones were harvested after death on day 58, and femoral resistance was determined by three-point bending testing. We found that fat mass was decreased in rats given strength training exercise and decreased further in rats treated with clenbuterol. Lean mass was increased in clenbuterol-treated animals. Strength-training exercise appeared to have no effect on bone mineral density, serum osteocalcin, or urinary deoxypyridinoline. However, clenbuterol treatment decreased femoral length, diameter, bone mineral density, and mechanical resistance. Clenbuterol had no effect on osteocalcin but increased urinary deoxypyridinoline. We concluded that clenbuterol treatment decreased bone mineral density and increased bone resorption independent of the level of exercise rats were given.

Alteration of Trabecular Bone under Chronic β2 Agonists Treatment

“…The higher CTx levels in salbutamol and clenbuterol groups compared with controls and the absence of differences in osteocalcin levels confirm the deleterious effects induced by these two substances. Similar results were obtained with clenbuterol by Cavalie et al, who showed an increase in urinary deoxypyridinoline excretion, linked to an increased bone resorption (2). Our study adds a certain amount of new data.…”

“…A decrease in BMC under clenbuterol treatment has been observed in male femur by Cavalie et al, who suggested that this effect might be due to a stimulation of osteoclastogenesis (2). Kellenberg et al and Togari et al observed a stimulation of osteoclastogenesis after treatment in vitro of MC3T3-E1 osteoblast cells with epinephrine or isoproterenol (14,26).…”

“…Is the effect of ␤2 adrenergic agonists on bone attenuated or potentiated by physical activity? Cavalie et al did not find any BMD difference in tibia between running and sedentary rats treated with clenbuterol, suggesting that this kind of exercise does not reduce the negative effect of ␤2 agonists on bone (2).…”

Double disruption of α2A- and α2C -adrenoceptors results in sympathetic hyperactivity and high-bone-mass phenotype

“…(7) Regardless of the evidence that b 2 -AR signaling is a key element in the regulation of bone remodeling, both pharmacologic and genetic experiments have produced inconclusive results. (12,13) Of note, the administration of b-adrenergic agonists such as salbutamol, (9,14) clenbuterol, (9,15) formoterol, and salbutamol (16) was shown to promote beneficial effects on bone mass of rats. On the other hand, the positive effects of beta blockers are not always detectable.…”

Effects of clenbuterol enantiomers on growth of young male rats

“…But in the present study we have no data about such. Cavalie et al 38) reported that CB decreased femoral length, diameter, and BMD of male rats, and it had no effect on osteocalcin, which is an active marker of osteoblast in plasma, but increased urinary de- Values are means ± S.D. Significant difference CONT and (+)-S-CLEB, **P < 0.01, *P < 0.05 Significant difference CONT and (-)-R-CLEB, † † P < 0.01, † P < 0.05 such drugs effectively in the treatment of disease without adverse side effects.…”