Severe bone alterations under beta2 agonist treatments: bone mass, microarchitecture and strength analyses in female rats.
OBJECTIVE
Beta2 adrenergic agonists are widely used in therapeutics and as doping agents by athletes. However, their effects on bone tissue, especially bone microarchitecture, remain poorly understood. Using three-dimensional (3D) microtomography, dual-energy X-ray absorptiometry, biomechanical testing and enzyme-linked immunosorbent assay, we evaluated the effects of two beta2 agonists, clenbuterol and salbutamol, on bone in growing rats.


METHODS
Twelve-week-old Wistar female rats (N = 39), divided in 3 groups, received during 6 weeks either salbutamol (4 mg/kg/day), clenbuterol (2 mg/kg/day) or normal saline (0.5 ml/kg/day) by subcutaneous injections.


RESULTS
After 6 weeks, the salbutamol and clenbuterol groups displayed lower bone mineral content (BMC), femoral length and cortical width than controls. Clenbuterol treatment further reduced bone mineral density. Bone microarchitecture was clearly altered by clenbuterol, as evidenced by lower trabecular number (-40.40%; P < 0.001), connectivity and trabecular bone volume (-42.85%; P < 0.001), leading to lower ultimate force. Clenbuterol significantly increased muscle mass (P < 0.01) and reduced fat mass when compared to controls. Salbutamol did not seem to have any effect on bone microarchitecture or body composition. Both beta2 agonists increased the bone resorption marker (C-terminal collagen crosslinks) without any change of a bone formation marker. At the end of the treatment, a drop in leptin was seen in the clenbuterol group only. Leptin levels were correlated with BMC (r = 0.69, P = 0.003).


CONCLUSIONS
These results confirm the deleterious effect of beta2 agonists on bone mass and show the negative effects of clenbuterol on trabecular bone microarchitecture. Bone loss occurred independently from muscle mass but was related to fat mass. A leptin-mediated effect on bone tissue seems likely. These pathophysiological effects may have important consequences in human therapeutics and doping.
Bonnet
N
N
Inserm U 658, CTI and ATOSEP, Orleans Regional Hospital and University of Orleans, 1, rue porte Madeleine, France. nicolas.bonnet15@wanadoo.fr
Benhamou
C L
CL
Brunet-Imbault
B
B
Arlettaz
A
A
Horcajada
M N
MN
Richard
O
O
Vico
L
L
Collomp
K
K
Courteix
D
D
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000420:Albuterol / Q000494:pharmacology*; D000818:Animals; D001696:Biomechanical Phenomena; D001835:Body Weight / Q000187:drug effects; D015519:Bone Density / Q000187:drug effects / Q000502:physiology; D001842:Bone and Bones / Q000033:anatomy & histology / Q000187:drug effects* / Q000502:physiology; D002113:Calcification, Physiologic / Q000187:drug effects / Q000502:physiology; D002976:Clenbuterol / Q000494:pharmacology*; D003094:Collagen / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D050152:Intra-Abdominal Fat / Q000187:drug effects; D020738:Leptin / Q000097:blood; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D009132:Muscles / Q000033:anatomy & histology / Q000187:drug effects; D015675:Osteocalcin / Q000032:analysis; D010012:Osteogenesis / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D000318:Adrenergic beta-Agonists; D020738:Leptin; D015675:Osteocalcin; D003094:Collagen; D000420:Albuterol; D002976:Clenbuterol