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.
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.
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).
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.
"Beta2-adrenergic (Beta2-AR) agonists are a widely-used therapy for asthma due to their actions on bronchial dilation. Beta2-AR agonists have been previously shown to cause catabolic effects in mouse and rat bone  . The findings of β-AR agonists in human osteoclast-like cells have further demonstrated direct stimulation of β-AR agonists on osteoclast activity in vitro . "
[Show abstract][Hide abstract] ABSTRACT: DMPC and DSPC liposomes were prepared via thin film hydration method followed by sonication. Propranolol solution was incorporated into liposomes at hydration stage. TEM images showed the sizes of DSPC and DMPC were around 88 and 137 nm, respectively. The highest encapsulation ratio of propranolol was approximately 70% using DSPC/CHO/OCT liposomes, which release the drug over 60% in 24 h and reached 100% in 48 h. Both propranolol (10-8-10-6 M) and DSCP liposomes-encapsulated propranolol showed over 1.5-fold increases in the proliferation of human osteoblastic cells hFOB1.19 while differentiation of the cells was approximately doubled by plain and liposomal propranolol, indicating that the stimulatory effects of liposomal propranolol are similar with those of propranolol on human osteoblastic hFOB1.19 cells. The phosphatidylcholine liposomes-encapsulated propranolol prepared in this study potentially possesses anabolic effects in vivo and is also a promising anti-osteoporotic agent in future.
[Show abstract][Hide abstract] ABSTRACT: Different models are used to study the effects of chronic alcohol consumption on bone tissue in the rat. However, the current models take several months to show indices of osteopenia as observed in chronic drinkers. Numerous studies have supported that chronic and intermittent exposure to ethanol vapors has predictive validity as a model of alcohol dependence in humans. However, this model has never been applied to bone research to study its effects on the parameters that define osteopenia. This was the goal of this study in the rat.
Male Wistar rats were exposed to ethanol vapor inhalation (n = 6) or air (controls, n = 6). Animals were exposed to chronic (11 weeks) and intermittent (14 hours a day) ethanol vapor reaching stable blood alcohol levels (BALs; 150 to 250 mg/dl) at the end of the third week of inhalation. After the sacrifice, right and left femur and tibia were dissected free of fat and connective tissue and bone mineral density (BMD) was assessed by dual X-ray absorptiometry. The microarchitecture of the femur was studied using microcomputed tomography.
The BMD of the left and right femurs and the left tibia was lower in the ethanol group compared with the control group. The bone volume fraction (BV/TV) and the bone surface density (BS/TV) were lower in the ethanol group compared with control animals. The trabecular number (Tb.N) was lower in the ethanol group while the trabecular spacing was higher.
The decrease in the BMD, BV/TV, and Tb.N is in the same range as what is observed in human drinkers and what is reported with other animal alcohol models (Lieber–DeCarli liquid diet, ethanol in the tap water). Therefore, this model could be useful to study the effects of chronic alcohol consumption in the bone research field and has the advantage of controlling easily targeted BALs.
Alcoholism Clinical and Experimental Research 07/2012; 37(s1). DOI:10.1111/j.1530-0277.2012.01899.x · 3.21 Impact Factor
"Decreased BFR and osteoblast number without affecting body weight in ob/ob or wt mice Kondo et al. (2005) Low bone mass Reduced bone mass in loaded mice, and unloading no longer further reduced bone mass Pierroz et al. (2005) Low bone mass Reduced BMD gain at total body and spine, and modestly decreased femur lengthening. Clenbuterol or salbutamol: ␤2-AR selective agonists Bonnet et al. (2005) "
[Show abstract][Hide abstract] ABSTRACT: With the rapid aging of the world population, the issue of skeletal health is becoming more prominent and urgent. The bone remodeling mechanism has sparked great interest among bone research societies. At the same time, increasing clinical and experimental evidence has driven attention towards the pivotal role of the sympathetic nervous system (SNS) in bone remodeling. Bone remodeling is thought to be partially controlled by the hypothalamus, a process which is mediated by the adrenergic nerves and neurotransmitters. Currently, new knowledge about the role of the SNS in the development and pathophysiology of osteoporosis is being generated. The aim of this review is to summarize the evidence that proves the involvement of the SNS in bone metabolism and to outline some common osteoporotic diseases that occur under different circumstances. The adrenergic signaling pathway and its neurotransmitters are involved to various degrees of importance in the development of osteoporosis in postmenopause, as well as in spinal cord injury, depression, unloading and the complex regional pain syndrome. In addition, clinical and pharmacological studies have helped to increase the comprehension of the adrenergic signaling pathway. We try to individually examine the contributions of the SNS in osteoporotic diseases from a different perspective. It is our hope that a further understanding of the adrenergic signaling by the SNS will pave the way for conceptualizing optimal treatment regimens for osteoporosis in the near future.
Ageing research reviews 04/2011; 10(2):253-63. DOI:10.1016/j.arr.2011.01.002 · 4.94 Impact Factor
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