Use of beta-blockers and the risk of hip/femur fracture in the United Kingdom and The Netherlands

Protective Effects of β-Blockers on Bone in Older Adults with Dementia

Increased β-adrenergic receptor activity has been hypothesized to cause bone loss in those with dementia. We investigated the effect of long-term β-blocker use on rate of bone loss in older adults with dementia. We used a linear mixed-effects model to estimate the relationship between long-term β-blocker use and rate of bone loss in participants from the Health Aging and Body Composition study. Records of 1198 participants were analyzed, 44.7% were men. Among the men, 25.2% had dementia and 20.2% were on β-blockers, while in the women, 22.5% had dementia and 16.6% received β-blockers. In the 135 men with dementia, 23 were taking β-blockers, while 15 of 149 women with dementia were using β-blockers. In men with dementia, β-blocker users had 0.00491 g/cm2 less bone mineral density (BMD) loss per year at the femoral neck (i.e., 0.63% less loss per year) than non-users (p < 0.05). No differences were detected in women with or without dementia and men without dementia. β-blockers may be protective by slowing down bone loss in older men with dementia.

Antihypertensive drugs demonstrate varying levels of hip fracture risk: A systematic review and meta-analysis

OBJECTIVE

By aggregating the literature, we evaluated the association between use of specific antihypertensive drugs and the risk of hip fractures compared with nonuse.

STUDY DESIGN AND SETTING

We systematically searched the Pubmed, Embase, and Cochrane databases from inception of each database until July 30, 2020 to identify articles including patients 18 years of age or older reporting on the association between antihypertensive drugs and the risk of hip fracture. Antihypertensive drugs were restricted to thiazides; beta-blockers; calcium-channel blockers; angiotensin-converting enzyme (ACE) inhibitors; and angiotensin receptor blockers. Nonusers encompass all patients that are not using the specific antihypertensive drug that has been reported. Unadjusted odds ratios with 95% confidence intervals (CIs) of the association between antihypertensive drug use and hip fractures were reported. Meta-analysis was performed when a minimum of five studies were identified for each antihypertensive drug class. Quality assessment was done using ROBINS-I tool. The GRADE approach was used to evaluate the certainty of the evidence.

RESULTS

Of 962 citations, 22 observational studies were included; 9 studies had a cohort design and 13 studies were case-control studies. No randomized controlled trials were identified. We found very low certainty of evidence that both thiazides (pooled odds ratio: 0.85, 95% CI 0.73 to 0.99, p = 0.04) as well as beta-blockers (pooled odds ratio: 0.88, 95% CI 0.79 to 0.98, p = 0.02) were associated with a reduced hip fracture risk as compared to specific nonuse. One study, reporting on angiotensin receptor blockers, also suggested a protective effect for hip fractures, whereas we found conflicting findings in four studies for calcium-channel blockers and in two studies for ACE inhibitors.

CONCLUSION

Among 22 observational studies, we found very low certainty of evidence that, compared to specific nonuse of antihypertensive drugs, use of thiazides, beta-blockers, and angiotensin receptor blockers were associated with a reduced protective hip fracture risk, while conflicting findings for calcium-channel blockers and ACE inhibitors were found. Given the low quality of included studies, further research -randomized controlled trials- are needed to definitively assess the causal relationship between specific antihypertensive drug classes and (relatively infrequent) hip fractures.

The modulatory effect and implication of gut microbiota on osteoporosis: from the perspective of "brain-gut-bone" axis

Osteoporosis (OP) is a kind of systemic metabolic disease characterized by decreased bone mass and destruction of the bone microstructure. In recent years, it has become an expected research trend to explore the cross-linking relationship in the pathogenesis process of OP so as to develop reasonable and effective intervention strategies. With the further development of intestinal microbiology and the profound exploration of the gut microbiota (GM), it has been further revealed that the "brain-gut" axis may be a potential target for the bone, thereby affecting the occurrence and progression of OP. Hence, based on the concept of "brain-gut-bone" axis, we look forward to deeply discussing and summarizing the cross-linking relationship of OP in the next three parts, including the "brain-bone" connection, "gut-bone" connection, and "brain-gut" connection, so as to provide an emerging thought for the prevention strategies and mechanism researches of OP.

Telmisartan Prevents Alveolar Bone Loss by Decreasing the Expression of Osteoclasts Markers in Hypertensive Rats With Periodontal Disease

Periodontal disease (PD) is a prevalent inflammatory disease with the most severe consequence being the loss of the alveolar bone and teeth. We therefore aimed to evaluate the effects of telmisartan (TELM), an angiotensin II type 1 receptor (Agtr1) antagonist, on the PD-induced alveolar bone loss, in Wistar (W) and Spontaneous Hypertensive Rats (SHRs). PD was induced by ligating the lower first molars with silk, and 10 mg/kg TELM was concomitantly administered for 15 days. The hemimandibles were subjected to microtomography, ELISA was used for detecting tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), CXCL3, and CCL2, while qRT-PCR was used for analyzing expression of components of renin-angiotensin system (RAS) (Agt, Ace, Agt1r, Agt2r, Ace2, and Masr), and bone markers (Runx2, Osx, Catnb, Alp, Col1a1, Opn, Ocn, Bsp, Bmp2, Trap, Rank, Rankl, CtsK, Mmp-2, Mmp-9, and osteoclast-associated receptor (Oscar)). The SHR + PD group showed greater alveolar bone loss than the W + PD group, what was significantly inhibited by treatment with TELM, especially in the SHR group. Additionally, TELM reduced the production of TNF-α, IL-1β, and CXCL3 in the SHR group. The expression of Agt increased in the groups with PD, while Agtr2 reduced, and TELM reduced the expression of Agtr1 and increased the expression of Agtr2, in W and SHRs. PD did not induce major changes in the expression of bone formation markers, except for the expression of Alp, which decreased in the PD groups. The bone resorption markers expression, Mmp9, Ctsk, and Vtn, was higher in the SHR + PD group, compared to the respective control and W + PD group. However, TELM attenuated these changes and increased the expression of Runx2 and Alp. Our study suggested that TELM has a protective effect on the progression of PD, especially in hypertensive animals, as evaluated by the resorption of the lower alveolar bone. This can be partly explained by the modulation in the expression of Angiotensin II receptors (AT1R and AT2R), reduced production of inflammatory mediators, the reduced expression of resorption markers, and the increased expression of the bone formation markers.

Beta-blocker choice and exchangeability in patients with heart failure and chronic obstructive pulmonary disease: an Italian register-based cohort study

Clinical guidelines suggest that for patients with heart failure and concurrent chronic obstructive pulmonary disease (COPD), metoprolol/bisoprolol/nebivolol should be preferred over carvedilol. However, studies suggest a high proportion of carvedilol usage that remains unexplained. Therefore, we aimed to investigate the predictors of carvedilol choice in patients with heart failure and COPD that were naïve to carvedilol or metoprolol/bisoprolol/nebivolol. Caserta Local Health Unit databases (Italy) were used as data sources. Age, sex, chronic/acute comorbidities, and co-medications were included in a logistic regression model to assess predictors of carvedilol choice. Chronic comorbidities include those defined in the Elixhauser comorbidity index and all hospitalizations within two years prior to the first beta-blocker prescription. Comedications include all redeemed prescriptions within one year prior to the beta-blocker prescription. Kernel density estimations were used to assess the overlap in propensity and preference scores distributions for receiving carvedilol and thereby potential beta-blocker exchangeability. Totally, 10091 patients composed the study population; 2011 were exposed to carvedilol. The overlapping of propensity scores distributions was 57%. Accordingly, the exchangeability was not reached. Atrioventricular block (Odds Ratio, OR 8.20; 95% Confidence Interval, 95% CI 1.30–51.80), cerebrovascular thrombosis (OR 7.06; 95% CI 1.14–43.68), chronic kidney disease (OR 4.32; 95% CI 1.16–16.02), and acute heart failure (OR 1.97; 95% CI 1.28–3.03) hospitalizations were statistically significantly associated with carvedilol choice. Analogously, human insulin (OR 3.00; 95% CI 1.24–7.24), fondaparinux (OR 2.47; 95% CI 1.17–5.21) or strontium ranelate (OR 2.03; 95% CI 1.06–3.90) redeemed prescriptions. In conclusion, this study suggests the absence of beta-blockers exchangeability and a preferential choice of carvedilol in patients with heart failure, COPD and concurrent chronic kidney disease, atrioventricular block, cerebrovascular thrombosis, acute heart failure or redeeming human insulin, fondaparinux or strontium ranelate prescriptions. Therefore, it suggests that choice of prescribing carvedilol over metoprolol/bisoprolol/nebivolol is driven by differences in comorbidities and co-treatments.

Atherosclerosis and Osteoporosis. Common Targets for the Effects of Cardiovascular and Anti-osteoporotic Drugs (Part I). The Effect of Cardiovascular Drugs on Bone Strength

Daily use of antihypertensive and lipid-lowering drugs in clinical practice dictates the need for knowledge of their pleiotropic effects. The article presents the results of studies of the effect of cardiovascular drugs, such as statins, beta-blockers, ACE inhibitors, diuretics, calcium antagonists and nitrates on bone mineral density and fractures associated with osteoporosis. The mechanisms of action of drugs on bone mass, markers of bone metabolism, the frequency of fractures in osteoporosis are discussed. Most studies show that the use of cardiac drugs along with a positive effect on the vascular wall, slow bone resorption and increase bone mass. Knowledge of the additional effect on bone metabolism of drugs used in cardiovascular diseases allows to choose an adequate therapy and improve the prognosis of both diseases.

Effects of Leptin on the Skeleton

Leptin originates in adipocytes, including those in bone marrow, and circulates in concentrations 20 to 90 times higher than those in the cerebrospinal fluid. It has direct anabolic effects on osteoblasts and chondrocytes, but it also influences bone indirectly, via the hypothalamus and sympathetic nervous system, via changes in body weight, and via effects on the production of other hormones (e.g., pituitary). Leptin's role in bone physiology is determined by the balance of these conflicting effects. Reflecting this inconsistency, the leptin-deficient mouse has reduced length and bone mineral content of long bones but increased vertebral trabecular bone. A consistent bone phenotype in human leptin deficiency has not been established. Systemic leptin administration in animals and humans usually exerts a positive effect on bone mass, and leptin administration into the cerebral ventricles usually normalizes the bone phenotype in leptin-deficient mice. Reflecting the role of the sympathetic nervous system in mediating the central catabolic effects of leptin on the skeleton, β-adrenergic agonists and antagonists have major effects on bone in mice, but this is not consistently seen in humans. The balance of the central and peripheral effects of leptin on bone remains an area of substantial controversy and might vary between species and according to other factors such as body weight, baseline circulating leptin levels, and the presence of specific pathologies. In humans, leptin is likely to contribute to the positive relationship observed between adiposity and bone density, which allows the skeleton to respond appropriately to changes in soft tissue mass.

Higher sympathetic activity as a risk factor for skeletal deterioration in pheochromocytoma

Despite the potential biological importance of sympathetic activity in human bone metabolism, its effects on bone microarchitecture, a key determinant of bone quality, has not been thoroughly studied. In the present study, we investigated the lumbar spine trabecular bone score (TBS) as an indicator of skeletal deterioration in pheochromocytoma. Among 620 consecutive patients with newly diagnosed adrenal incidentaloma, 29 with histologically confirmed pheochromocytoma (a catecholamine-secreting neuroendocrine tumor) and 266 with nonfunctional adrenal incidentaloma were defined as cases and controls, respectively. After adjustment for confounders, subjects with pheochromocytoma had 2.9% lower lumbar spine TBS than those without pheochromocytoma (P = 0.038). Moreover, urinary normetanephrine level, but not urinary metanephrine level, was inversely correlated with lumbar spine TBS (P = 0.009). Subjects in the highest urinary normetanephrine quartile showed markedly lower lumbar spine TBS than those in the lowest quartile (P = 0.018), in a dose-response manner across increasing urinary normetanephrine quartile categories (P for trend = 0.021). Consistent with the results of previous studies, subjects with pheochromocytoma had significantly lower bone mass at the lumbar spine and higher serum level of C-terminal telopeptide of type I collagen than controls (P = 0.013 and 0.002, respectively). These findings provide clinical evidence that catecholamine excess and the resultant sympathetic overstimulation in pheochromocytoma may contribute to bone fragility, especially in the trabecular bone, through a weak microarchitecture in addition to a lower bone mass and increased bone resorption, and support the possibility of pheochromocytoma as a secondary cause of osteoporosis.

The Time Point-Specific Effect of Beta-Adrenergic Blockade in Attenuating High Fat Diet-Induced Obesity and Bone Loss

We aimed to clarify the key factor determining the effect of beta blocker attenuating high fat diet- induced obesity and bone loss. Six-week-old C57BL/6 male mice were assigned to groups reflecting different relative onset of obesity and beta blocker administration, different diet (control vs. high fat), and treatment (vehicle vs. beta blocker: propranolol). Mice in Group 1 were fed a control diet (CON) or high fat diet (HIGH) with vehicle or propranolol for 12 weeks. Mice in Group 2 were fed a CON or HIGH without pharmaceutical treatment for the first 12 weeks, followed by another 12 weeks of treatment with vehicle or propranolol. Mice in Group 3 were fed a CON without pharmaceutical treatment for the first 12 weeks, followed by stratification into diet-based subgroups and another 12 weeks of treatment with vehicle or propranolol. Propranolol attenuated the HIGH-induced increase in body weight/fat mass in Group 1 mice and in Group 3 mice, but not in Group 2 mice. Propranolol mitigated HIGH-induced reduction in femoral trabecular bone mineral density and bone architecture deterioration in Group 1 mice but not in Group 2 mice. HIGH feeding in Group 3 did not compromise skeletal integrity. Taken together, propranolol attenuates HIGH-induced body weight increases while weight gain is in progress but not once obesity has already been established. HIGH feeding during the growth period results in compromised bone mass/architecture; which can be attenuated by propranolol administration during the growth period, but not by propranolol administration after obesity has already been established.

Bone Health in Adrenal Disorders

Secondary osteoporosis resulting from specific clinical disorders may be potentially reversible, and thus continuous efforts to find and adequately treat the secondary causes of skeletal fragility are critical to ameliorate fracture risk and to avoid unnecessary treatment with anti-osteoporotic drugs. Among the hyperfunctional adrenal masses, Cushing's syndrome, pheochromocytoma, and primary aldosteronism are receiving particularly great attention due to their high morbidity and mortality mainly by increasing cardiovascular risk. Interestingly, there is accumulating experimental and clinical evidence that adrenal hormones may have direct detrimental effects on bone metabolism as well. Thus, the present review discusses the possibility of adrenal disorders, especially focusing on pheochromocytoma and primary aldosteronism, as secondary causes of osteoporosis.

Lower Bone Mass and Higher Bone Resorption in Pheochromocytoma: Importance of Sympathetic Activity on Human Bone

CONTEXT

Despite the apparent biological importance of sympathetic activity on bone metabolism in rodents, its role in humans remains questionable.

OBJECTIVE

To clarify the link between the sympathetic nervous system and the skeleton in humans.

DESIGN, SETTING, AND PATIENTS

Among 620 consecutive subjects with newly diagnosed adrenal incidentaloma, 31 patients with histologically confirmed pheochromocytoma (a catecholamine-secreting neuroendocrine tumor) and 280 patients with nonfunctional adrenal incidentaloma were defined as cases and controls, respectively.

RESULTS

After adjustment for confounders, subjects with pheochromocytoma had 7.2% lower bone mass at the lumbar spine and 33.5% higher serum C-terminal telopeptide of type 1 collagen (CTX) than those without pheochromocytoma (P = 0.016 and 0.001, respectively), whereas there were no statistical differences between groups in bone mineral density (BMD) at the femur neck and total hip and in serum bone-specific alkaline phosphatase (BSALP) level. The odds ratio (OR) for lower BMD at the lumbar spine in the presence of pheochromocytoma was 3.31 (95% confidence interval, 1.23 to 8.56). However, the ORs for lower BMD at the femur neck and total hip did not differ according to the presence of pheochromocytoma. Serum CTX level decreased by 35.2% after adrenalectomy in patients with pheochromocytoma, whereas serum BSALP level did not change significantly.

CONCLUSIONS

This study provides clinical evidence showing that sympathetic overstimulation in pheochromocytoma can contribute to adverse effects on human bone through the increase of bone loss (especially in trabecular bone), as well as bone resorption.

Effect of Beta-Blockers on Number of Osteoblasts and Osteoclasts in Alveolar Socket Following Tooth Extraction in Wistar Rats

STATEMENT OF THE PROBLEM

Various researchers have suggested the use of β2-adrenergic receptor antagonists in prevention or treatment of bone resorption.

PURPOSE

This study aimed to evaluate the effect of β2-adrenergic receptor antagonists on number of osteoclasts and osteoblasts involved in the healing of extraction socket of maxillary first molar in rats.

MATERIALS AND METHOD

Maxillary first molars of 40 rats were extracted and divided into two groups. The test group received 0.1 mg/kg propranolol intraperitoneally daily. The controls received normal saline. At days 7, 14, 21 and 28 post-extraction, 5 rats were euthanized from each group. Maxillary bone was resected and the mean number of osteoblasts and osteoclasts in tooth socket was measured.

RESULTS

After 1 week, the number of osteoclasts in the controls was significantly higher than the test group. A significant increase in the number of osteoclasts in both groups at week 1 was observed compared to the following weeks (p< 0.05). The number of osteoblasts in the controls at second week reached its maximum rate but stayed constant in the 3rd and 4th weeks. Osteoblasts in the test group increased similar to the controls but reached its maximum at 3rd week and showed a significant increase compared to the controls (p< 0.05).

CONCLUSION

β2 adrenergic receptor antagonists decrease the number of osteoclasts and increase the number of osteoblasts during extraction socket healing.

The IMI PROTECT project: purpose, organizational structure, and procedures

The Pharmacoepidemiological Research on Outcomes of Therapeutics by a European ConsorTium (PROTECT) initiative was a collaborative European project that sought to address limitations of current methods in the field of pharmacoepidemiology and pharmacovigilance. Initiated in 2009 and ending in 2015, PROTECT was part of the Innovative Medicines Initiative, a joint undertaking by the European Union and pharmaceutical industry. Thirty-five partners including academics, regulators, small and medium enterprises, and European Federation of Pharmaceuticals Industries and Associations companies contributed to PROTECT. Two work packages within PROTECT implemented research examining the extent to which differences in the study design, methodology, and choice of data source can contribute to producing discrepant results from observational studies on drug safety. To evaluate the effect of these differences, the project applied different designs and analytic methodology for six drug-adverse event pairs across several electronic healthcare databases and registries. This papers introduces the organizational structure and procedures of PROTECT, including how drug-adverse event and data sources were selected, study design and analyses documents were developed, and results managed centrally.

Clonidine increases bone resorption in humans

SUMMARY

Inhibition of sympathetic signaling to bone reduces bone resorption in rodents. In contrast, we show that pharmacological reduction of the sympathetic tone increases bone resorption in humans in vivo. This effect does not appear to be mediated via a direct pharmacological effect on the osteoclast.

INTRODUCTION

Inhibition of sympathetic signaling to bone reduces bone resorption in rodents. It is uncertain whether a similar role for the sympathetic nervous system exists in humans. The sympathetic tone can be reduced by clonidine, which acts via alpha-2-adrenergic receptors in the brainstem. Our objective was to determine the effect of clonidine on bone turnover in humans.

METHODS

The acute effect of a single oral dose of 0.3 mg clonidine on serum bone turnover markers (C-terminal cross-linking telopeptides of collagen type I (CTx), a marker for bone resorption, and procollagen type 1 N propeptide (P1NP), a marker for bone formation) was determined in a randomized crossover design in 12 healthy volunteers, aged 18-70 years. In addition, we assessed the effect of clonidine on the number of tartrate-resistant acid phosphatase-positive multinucleated cells (TRAcP(+) MNCs) and bone resorption.

RESULTS

CTx concentrations increased after clonidine treatment compared to the control condition (p = 0.035). P1NP concentrations were not affected by clonidine (p = 0.520). In vitro, clonidine had no effect on the number of TRAcP(+) MNCs (p = 0.513) or on bone resorption (p = 0.996).

CONCLUSIONS

We demonstrated that clonidine increases bone resorption in humans in vivo. This effect does not appear to be mediated via a direct effect on the osteoclast.

Bridging differences in outcomes of pharmacoepidemiological studies: design and first results of the PROTECT project

Background:

Observational pharmacoepidemiological (PE) studies on drug safety have produced discrepant results that may be due to differences in design, conduct and analysis.

Purpose:

The pharmacoepidemiology work-package (WP2) of the Pharmacoepidemiological Research on Outcomes of Therapeutics by a European ConsorTium (PROTECT) project aims at developing, testing and disseminating methodological standards for design, conduct and analysis of pharmacoepidemiological studies applicable to different safety issues using different databases across European countries. This article describes the selection of the safety issues and the description of the databases to be systematically studied.

Methods:

Based on two consensus meetings and a literature search, we selected five drug-adverse event (AE) pairs to be evaluated in different databases. This selection was done according to pre-defined criteria such as regulatory and public health impact, and the potential to investigate a broad range of methodological issues.

Results:

The selected drug-AE pairs are: 1) inhaled long-acting beta-2 agonists and acute myocardial infarction; 2) antimicrobials and acute liver injury; 3) antidepressants and/or benzodiazepines and hip fracture; 4) anticonvulsants and suicide/suicide attempts; and 5) calcium channel blockers and malignancies. Six European databases, that will be used to evaluate the drug-AE pairs retrospectively, are also described.

Conclusion:

The selected drug-AE pairs will be evaluated in PE studies using common protocols. Based on consistencies and discrepancies of these studies, a framework for guiding methodological choices will be developed. This will increase the usefulness and reliability of PE studies for benefit-risk assessment and decision-making.

Additive effects of zoledronic acid and propranolol on bone density and biochemical markers of bone turnover in osteopenic ovariectomized rats

OBJECTIVES

The present study was designed to investigate further the efficacy and safety of zoledronic acid (ZOL) and propranolol (PRO) as monotherapy and combination therapy in a rat model of postmenopausal osteoporosis.

METHODS

Female Wistar rats were ovariectomized (OVX) or sham-operated at 3 months of age. Twelve weeks post-surgery, rats were randomized into six groups: (1) sham + vehicle; (2) OVX + vehicle; (3) OVX + ZOL (100 μg/kg, i.v. single dose); (4) OVX + ZOL (50 μg/kg, i.v. single dose); (5) OVX + PRO (0.1 mg/kg, s.c. 5 days per week); (6) OVX + ZOL (50 μg/kg, i.v. single dose) + PRO (0.1 mg/kg, s.c. 5 days per week) for 12 weeks. After treatment, femurs were tested for bone density, porosity and trabecular micro-architecture. Biochemical markers in serum and urine were also determined.

RESULTS

Combined treatment with ZOL plus PRO corrected decrease in serum calcium and increase in serum alkaline phosphatase and tartarate resistant acid phosphatase level better than single-drug therapy using ZOL or PRO. Moreover, combined treatment with ZOL plus PRO corrected increase in urine calcium, phosphorous and creatinine level better than single-drug therapy using ZOL or PRO. Combination therapy using ZOL plus PRO also preserved the trabecular micro-architecture and cortical bone porosity.

CONCLUSION

These data suggest that combined treatment with ZOL plus PRO could be more effective approach for treating severe osteoporosis in humans.

Effect of combined treatment with zoledronic acid and propranolol on mechanical strength in an rat model of disuse osteoporosis

OBJECTIVES

A model that uses right hind-limb unloading of rats is used to study the consequences of skeletal unloading during various conditions like space flights and prolonged bed rest in elderly. This study was aimed to investigate the additive effects of antiresorptive agent zoledronic acid (ZOL), alone and in combination with propranolol (PRO) in a rat model of disuse osteoporosis.

METHODS

In the present study, 3-month-old male Wistar rats had their right hind-limb immobilized (RHLI) for 10 weeks to induce osteopenia, then were randomized into four groups: 1- RHLI positive control, 2- RHLI plus ZOL (50 μg/kg, i.v. single dose), 3- RHLI plus PRO (0.1mg/kg, s.c. 5 days per week), 4- RHLI plus PRO (0.1mg/kg, s.c. 5 days per week) plus ZOL (50 μg/kg, i.v. single dose) for another 10 weeks. One group of non-immobilized rats was used as negative control. At the end of treatment, the femurs were removed and tested for bone porosity, bone mechanical properties, and bone dry and ash weight.

RESULTS

With respect to improvement in the mechanical strength of the femoral mid-shaft, the combination treatment with ZOL plus PRO was more effective than ZOL or PRO monotherapy. Moreover, combination therapy using ZOL plus PRO was more effective in improving dry bone weight and preserved the cortical bone porosity better than monotherapy using ZOL or PRO in right hind-limb immobilized rats.

CONCLUSIONS

These data suggest that this combined treatment with ZOL plus PRO should be recommended for the treatment of disuse osteoporosis.

Do effects of propranolol on the skeletal system depend on the estrogen status?

BACKGROUND

Propranolol, a nonselective β-adrenergic receptor antagonist, was reported to favorably affect the skeletal system in different animal models. The aim of the study was to investigate whether the effects of propranolol on the skeletal system depend on the estrogen status.

METHODS

The in vivo experiments were carried out on the following groups of mature female Wistar rats: sham-operated control rats, sham-operated rats receiving propranolol, ovariectomized (OVX) control rats, OVX rats receiving propranolol, OVX rats receiving estradiol, OVX rats receiving estradiol and propranolol. Propranolol hydrochloride (10 mg/kg po) and/or estradiol (0.1 mg/kg po) were administered daily for 4 weeks. Bone mass, mineral and calcium content, macrometric and histomorphometric parameters, and mechanical properties were examined. In vitro, effects of estradiol and propranolol on the formation of mouse osteoclasts and on the mRNA expression of genes related to osteoclastogenesis, bone formation and mineralization, as well as adrenergic and estrogen signalling in mouse osteoblasts were investigated.

RESULTS AND CONCLUSION

Propranolol exerted some favorable effects on the rat skeletal system in vivo, independently of the estrogen status. However, in vitro studies indicated a possibility of some antagonistic relations between the estradiol and propranolol effects.

The combination therapy with zoledronic Acid and propranolol improves the trabecular microarchitecture and mechanical property in an rat model of postmenopausal osteoporosis

We conducted the present study to investigate the therapeutic effects of propranolol (PRO), alone and in combination with the antiresorptive agent ZOL, in a rat model of postmenopausal osteoporosis. Female Wistar rats were OVX or sham-operated at 3 months of age. Twelve weeks after surgery, rats were randomized into six groups: (1) sham + vehicle, (2) OVX + vehicle, (3) OVX + ZOL (100  μ g/kg, i.v. single dose), (4) OVX + ZOL (50  μ g/kg, i.v. single dose), (5) OVX + PRO (0.1 mg/kg, s.c. 5 days per week), and (6) OVX + ZOL (50  μ g/kg, i.v. single dose) + PRO (0.1 mg/kg, s.c. 5 days per week) for 12 weeks. At the end of treatment study, various bone parameters were evaluated. With respect to improvement in the mechanical strength of the lumbar spine and the femoral mid-shaft, the combination treatment of ZOL and PRO was more effective than each drug administered as a monotherapy. Moreover, combination therapy using ZOL and PRO preserved the trabecular microarchitecture better than single-drug therapy using ZOL or PRO in OVX rats. These data suggest that combination therapy with ZOL plus PRO represents a potentially useful therapeutic option for patients with osteoporosis.

β-Adrenergic receptor antagonists and fracture risk: a meta-analysis of selectivity, gender, and site-specific effects

By meta-analysis, the risk of fracture was 15% lower in patients treated with β-adrenergic blockers compared to controls independent of gender, fracture site, and dose. This might be attributable to β1-selective blockers.

INTRODUCTION

The aim of this study is to determine by meta-analysis whether β-adrenergic blockers (BBs) reduce fracture risk and whether the effect, if demonstrable, is dependent upon selectivity, dose, gender, or fracture site.

METHODS

A literature search was performed in electronic databases MEDLINE, EMBASE, and reference sections of relevant articles to identify eligible studies. Adjusted estimates of fracture risk effect size (ES) were pooled across studies using fixed or random-effects (RE) meta-analysis as appropriate. Dose-related effects were evaluated using meta-regression. To explore the relative efficacy of β1-selective blockers in comparison to nonselective BBs, adjusted indirect comparison was performed.

RESULTS

A total of 16 studies (7 cohort and 9 case-control studies), involving 1,644,570 subjects, were identified. The risk of any fracture was found to be significantly reduced in subjects receiving BBs as compared to control subjects (16 studies, RE pooled ES = 0.86, 95% CI 0.78-0.93; I(2) = 87 %). In a sensitivity analysis limited to those studies deemed to be most robust, the BB effect to reduce fracture risk was sustained (four studies, pooled ES = 0.79, 95% CI 0.67-0.94; I(2) = 96%). The risk of a hip fracture was lower in both women and men receiving BBs (women: pooled ES = 0.86, 95% CI 0.80-0.91; I(2) = 1% and men: pooled ES = 0.80, 95% CI 0.71-0.90; I(2) = 0%). Similar risk reductions were found for clinical vertebral and forearm fractures, although statistical significance was not reached. The reduction in risk did not appear to be dose-related (test for a linear trend p value 0.150). Using adjusted indirect comparisons, it was estimated that β1-selective agents were significantly more effective than nonselective BBs in reducing the risk of any fracture (six studies, β1-selective blockers vs. nonselective BBs: RE pooled ES = 0.82, 95% CI = 0.69-0.97).

CONCLUSIONS

The findings suggest that the risk of fracture is approximately 15% lower in patients treated with BBs compared to controls independent of gender, fracture site, and dose. This risk reduction might be associated with the effects of β1-selective blockers.

Prophylactic Effects of Propranolol versus the Standard Therapy on a New Model of Disuse Osteoporosis in Rats

Disuse by bed rest, limb immobilization, or space flight causes rapid bone loss by arresting bone formation and accelerating bone resorption. Propranolol (a non-selective β-adrenergic antagonist) has been shown to improve bone properties by increasing bone formation and decreasing bone resorption in an ovariectomy-induced rat model. However, no studies have yet compared the osteoprotective properties of propranolol with well-accepted therapeutic interventions for the treatment and prevention of immobilization/disuse osteoporosis. To clarify this, we investigated the effects of propranolol compared with zoledronic acid and alfacalcidol in a new animal model of immobilization/disuse osteoporosis. Three-month-old male Wistar rats were divided into five groups with six animals in each group: (1) immobilized (IMM) control; (2) normal control; (3) IMM + zoledronic acid (50 μg/kg, intravenous single dose); (4) IMM + alfacalcidol (0.5 μg/kg, per oral daily); (5) IMM + propranolol (0.1 mg/kg, subcutaneously 5 days/week) for 10 weeks. In groups 1 and 3-5, the right hindlimb was immobilized. At the end of treatment, the femurs were removed and tested for bone porosity, bone mechanical properties, and cortical microarchitecture. Treatment with propranolol induced greater reductions in the bone porosity of the right femur and improved the mechanical properties of the femoral mid-shaft femur in comparison to the IMM control. Moreover, treatment with propranolol also improved the microarchitecture of cortical bones when compared with the IMM control, as indicated by scanning electron microscopy. The anti-osteoporotic property of propranolol was comparable with zoledronic acid and alfacalcidol. This study shows that the bone resorption induced by immobilization/disuse in rats can be suppressed by treatment with propranolol.

Osteoprotective effect of propranolol in ovariectomized rats: a comparison with zoledronic acid and alfacalcidol

BACKGROUND

Currently β-adrenergic receptor blockers are considered to be potential drugs under investigation for preventive or therapeutic effect in osteoporosis. However, there is no published data showing the comparative study of β-blockers with well accepted agents for the treatment of osteoporosis. To address this question, we compared the effects of propranolol with well accepted treatments like zoledronic acid and alfacalcidol in an animal model of postmenopausal osteoporosis.

METHODS

Five days after ovariectomy, 36 ovariectomized (OVX) rats were divided into 6 equal groups, randomized to treatments zoledronic acid (100 μg/kg, intravenous single dose); alfacalcidol (0.5 μg/kg, oral gauge daily); propranolol (0.1 mg/kg, subcutaneously 5 days per week) for 12 weeks. Untreated OVX and sham OVX were used as controls. At the end of treatment serum calcium and alkaline phosphatase were assayed. Femurs were removed and tested for bone density, bone porosity, bone mechanical properties and trabecular micro-architecture.

RESULTS

Propranolol showed a significant decrease in alkaline phosphatase levels and bone porosity in comparison to OVX control. Moreover, propranolol significantly improved bone density, bone mechanical properties and inhibited the deterioration of trabecular microarchitecture when compared with OVX control. The osteoprotective effect of propranolol was comparable with zoledronic acid and alfacalcidol.

CONCLUSIONS

Based on this comparative study, the results strongly suggest that propranolol can be a candidate therapeutic drug for the management of postmenopausal osteoporosis.

β1 selectivity of β-blockers and reduced risk of fractures in elderly hypertension patients

INTRODUCTION

Hypertension and osteoporosis are prevalent in the elderly population. Treatments beneficial to both conditions would be helpful. We examined the protective effect of β-blockers (BBs) and their receptor selectivity against fractures compared to other antihypertensives.

MATERIALS AND METHODS

A retrospective cohort was assembled using the Korean Health Insurance Review and Assessment Service database from January 2005 to June 2006. The cohort consisted of 501,924 patients (ages 65 and older) on single-drug therapy for hypertension. Participants were followed to either the date of the first fracture, date of death or end of the study period (30 June 2006), whichever came first. Cox's proportional hazard model was used to calculate the adjusted hazard ratio (aHR) and 95% confidence interval (CI) by sex, adjusting for confounders. Risk of fractures by BBs according to β1 selectivity was compared to non BBs measured in aHR.

RESULTS

Among 501,924 (65% female), the incidence density of fractures in non BB users was 29.3 and 48.2 per 1000 person-years for men and women, respectively, which was higher than in BB users (17.2 for men and 30.5 for women). Compared to BB users, non BB users showed an increased risk of all fracture [aHR 1.56 (95% CI, 1.42-1.72) in men and 1.44 (95% CI, 1.36-1.51) in women] and hip fracture [aHR 2.17 (95% CI 1.45-3.24) in men and 1.61 (95% CI 1.31-1.98) in women] after adjusting for confounding variables. Compared to BBs, the risks of all fractures in α-blockers, calcium channel blockers, diuretics, and renin-angiotensin-aldosterone system blockers were significantly higher (1.72, 1.77, 1.58, 1.29 in men; 2.11, 1.50, 1.46, 1.22 in women, respectively). Compared to non BBs, β1 selective BBs showed a lower risk of fracture (39% for men and 33% for women) after adjusting for confounding factors. On the contrary, non-selective BBs were not protective against fracture.

CONCLUSION

Our results suggested that β1 selective BBs reduce the risk of fractures compared to other classes of antihypertensives in an elderly population, which could have practical applications for strategies to control and prevent adverse outcomes from both hypertension and osteoporosis in this population.

Association between beta-blockers and fracture risk: a Bayesian meta-analysis

BACKGROUND

The association between beta-blockers (BB) and fracture risk is controversial, due largely to conflicting findings from previous studies. The present study sought to evaluate the effect of BB on fracture risk by using a Bayesian meta-analysis approach.

METHODS AND RESULTS

We systematically retrieved 13 observational studies on the association between BB use and fracture risk. This meta-analysis involved more than 907,000 men and women with mean/median age of individual studies ranging from 43 to 81 years. We used a hierarchical Bayesian random effects model to synthesize the results. BB use was associated with an average 17% reduction in the risk of any fracture (risk ratio [RR] 0.83; 95% credible interval [CrI]: 0.71-0.93), hip fracture (RR 0.83; 95% CrI: 0.70-0.92) and vertebral fracture (RR 0.81; 95% CrI: 0.61-0.99). The probability that BB use reduces fracture risk by at least 10% was 0.91.

CONCLUSIONS

Beta-blockers are associated with reduced risk of fracture in older adults, but the effect size is likely to be modest.

Determining the Incidence of Adult Fractures: How Accurate Are Emergency Department Data?

Various research methods have been used to obtain skeletal fracture data and report the incidence of fractures. A large number of British studies have used data collected in emergency departments, and not data derived from orthopaedic units. We hypothesised that fracture data will differ depending upon the methodology employed to capture it. Two commonly used sources of fracture data at our institution were compared, (the Emergency Department (ED) database and the Orthopaedic Trauma Unit (OTU) database), using a cohort of adult patients from our defined population as the study sample. We performed univariate analyses to identify differences between groups with accurate and inaccurate ED fracture diagnoses. We then performed a binary logistic regression analysis to determine the best predictors of diagnostic accuracy. In one year, 7,449 patients were referred to the OTU. Three-quarters were referred with fractures. The overall false positive fracture referral rate was 25%. Several fracture subtypes were commonly overdiagnosed in the ED. Regression analysis showed that patient age, patient gender, and the seniority of the referring clinician were independently predictive of an accurate fracture diagnosis. We suggest that studies making use of ED fracture data may potentially overestimate the incidence of adult fractures.

Heart drugs that affect bone

There have been important developments in our understanding of the mechanisms underlying the development of osteoporosis, and several of these mechanisms also underlie atherosclerosis. Drugs given to treat cardiovascular disease may impact on bone health in either a beneficial or a harmful way. There is evidence that nitrates are beneficial to bone, but evidence for the benefit of statins, thiazide diuretics, and β-blockers is weaker. By contrast, it is likely to be that some drugs such as loop-acting diuretics are harmful to bone, whereas evidence for harm caused by drugs such as warfarin is weaker. These observations point towards opportunities for new drug development for bone diseases, and possibly the development of treatments that will benefit more than one disease.

Calibration of FRAX ® 3.1 to the Dutch population with data on the epidemiology of hip fractures

The FRAX tool has been calibrated to the entire Dutch population, using nationwide (hip) fracture incidence rates and mortality statistics from the Netherlands. Data used for the Dutch model are described in this paper.

INTRODUCTION

Risk communication and decision making about whether or not to treat with anti-osteoporotic drugs with the use of T-scores are often unclear for patients. The recently developed FRAX models use easily obtainable clinical risk factors to estimate an individual's 10-year probability of a major osteoporotic fracture and hip fracture that is useful for risk communication and subsequent decision making in clinical practice. As of July 1, 2010, the tool has been calibrated to the total Dutch population. This paper describes the data used to develop the current Dutch FRAX model and illustrates its features compared to other countries.

METHODS

Age- and sex-stratified hip fracture incidence rates (LMR database) and mortality rates (Dutch national mortality statistics) for 2004 and 2005 were extracted from Dutch nationwide databases (patients aged 50+ years). For other major fractures, Dutch incidence rates were imputed, using Swedish ratios for hip to osteoporotic fracture (upper arm, wrist, hip, and clinically symptomatic vertebral) probabilities (age- and gender-stratified). The FRAX tool takes into account age, sex, body mass index (BMI), presence of clinical risk factors, and bone mineral density (BMD).

RESULTS

Fracture incidence rates increased with increasing age: for hip fracture, incidence rates were lowest among Dutch patients aged 50-54 years (per 10,000 inhabitants: 2.3 for men, 2.1 for women) and highest among the oldest subjects (95-99 years; 169 of 10,000 for men, 267 of 10,000 for women). Ten-year probability of hip or major osteoporotic fracture was increased in patients with a clinical risk factor, lower BMI, female gender, a higher age, and a decreased BMD T-score. Parental hip fracture accounted for the greatest increase in 10-year fracture probability.

CONCLUSION

The Dutch FRAX tool is the first fracture prediction model that has been calibrated to the total Dutch population, using nationwide incidence rates for hip fracture and mortality rates. It is based on the original FRAX methodology, which has been externally validated in several independent cohorts. Despite some limitations, the strengths make the Dutch FRAX tool a good candidate for implementation into clinical practice.

Effects of propranolol on the development of glucocorticoid-induced osteoporosis in male rats

Glucocorticoid-induced osteoporosis is the most frequently occurring type of secondary osteoporosis. Antagonists of β-adrenergic receptors are now considered to be potential drugs under investigation for osteoporosis. The aim of the present study was to investigate the effects of propranolol, a nonselective β-receptor antagonist, on the skeletal system of mature male rats and on the development of bone changes induced by glucocorticoid (prednisolone) administration. The experiments were performed on 24-week-old male Wistar rats. The effects of prednisolone 21-hemisuccinate sodium salt (7 mg/kg, sc daily) or/and propranolol hydrochloride (10 mg/kg, ip daily) administered for 4 weeks on the skeletal system were studied. Bone and bone mineral mass in the tibia, femur and L-4 vertebra, length and diameter of the long bones, mechanical properties of tibial metaphysis, femoral diaphysis and femoral neck, bone histomorphometric parameters and turnover markers in serum were determined. Prednisolone-induced unfavorable skeletal changes led to disorders in bone mechanical properties. Propranolol not only did not improve bone parameters, but even caused deleterious effects on the skeletal system. Concurrent administration of propranolol with prednisolone did not counteract the changes induced by prednisolone. The results of this study may help to understand the equivocal results of human studies on the effects of β-blockers on the skeletal system. It is possible that the drugs exert biphasic effects on the skeletal system, both favorable and deleterious, depending on the dose or individual susceptibility.

Knee arthroplasty and risk of hip fracture: a population-based, case-control study

The majority of knee arthroplasties (KAs) are performed in patients with osteoarthritis (OA). Although bone mass may be increased in these patients, subjects with knee OA may have an increased risk of hip fracture, possibly due to an increased severity of falls. However, in patients with KAs, risk of hip fracture has not been studied extensively. We evaluated the association between KAs and hip fracture risk in a population-based case-control study using the Dutch PHARMO Record Linkage System (1991-2002, n = 33,104). Cases were patients with a first admission for hip fracture; controls were matched by age, gender, and geographic location. Neither group had a previous history of fracture. Time since first KA was calculated. Analyses were adjusted for disease and drug history. A 54% increased hip fracture risk was found in patients who underwent KA (adjusted [adj.] OR = 1.54, 95% CI 1.19-2.00). We found a strong effect modification by age in these patients: the youngest patients (aged 18-70 years) were at more increased risk for hip fracture (adj. OR = 2.76, 95% CI 1.16-6.59), while we could not detect a statistical increase in patients aged >80 years. Furthermore, the association tended to be greater during the first few years after surgery, although it did not reach statistical significance. We found that KAs are associated with a 54% increased risk of hip fracture, in particular among adult patients aged <71 years old. Fracture risk assessment could be considered in patients who are about to undergo a KA.

Carvedilol ameliorates low-turnover bone disease in non-obese type 2 diabetes

BACKGROUND

Diabetic bone disease is a major complication in diabetes mellitus and is characterized by low-turnover bone formation. Recent studies have demonstrated that oxidative stress could be associated with diabetic bone disease and that β-adrenergic antagonists could increase bone formation. Our study investigated the effect of carvedilol (β-blocker), possessing an antioxidant effect, on diabetic bone disease.

METHODS

We used the non-obese, type 2 diabetes model Spontaneously Diabetic Torii (SDT) rats in this study. Sprague-Dawley rats were used as controls (control, n = 6). SDT rats were divided into four groups: diabetic (DM, n = 8), DM+insulin (DM+I, n = 7), DM+carvedilol (DM+C, n = 8), and DM+N-acetylcysteine (DM+N, n = 10) at 20 weeks. The rats were sacrificed at 30 weeks, after which blood and urine samples, bone mineral density, histomorphometry, and oxidative stress were evaluated.

RESULTS

The number of 8-hydroxydeoxyguanosine-positive cells in bone tissue was significantly lower in the DM+C and DM+N groups than in the DM group. Mineral apposition rate and bone formation rate per bone surface in the DM+C and DM+N groups were significantly higher than those in the DM group, and these parameters were better in the DM+C group than in the DM+N group.

CONCLUSION

Our data suggest that carvedilol has stronger effects on diabetic low-turnover bone disease beyond that which can be attributed to its antioxidative stress mechanism.

Dopaminergic drugs and the risk of hip or femur fracture: a population-based case-control study

SUMMARY

The effect of dopaminergic medication on the risk of hip/femur fractures is not clear. Our results showed a nearly twofold increased risk of hip/femur fractures in current dopaminergic drug users. Concomitant use of antidepressants further increased this risk. Fracture risk assessment may be warranted in elderly users of dopaminergic drugs.

INTRODUCTION

Dopaminergic drugs, often used in the treatment of Parkinson's disease, have several pharmacological effects that may increase or decrease the risk of falling and fractures. Thus, the effect of dopaminergic medication on the risk of hip/femur fractures is not clear. The objective of the study was to examine the effect of dopaminergic medication and concomitant use of psychotropics on the risk of hip/femur fractures taking into account the timing of dopaminergic drug use.

METHODS

A population-based case-control study in the PHARMO database was conducted for the period 1991 to 2002. Cases were patients aged 18 years and older with a first hip or femur fracture and matched to four control patients by year of birth, sex and geographical region.

RESULTS

The study population included 6,763 cases and 26,341 controls. Current use of dopaminergic drugs (1-30 days before the index date) was associated with an increased risk of hip/femur fractures compared to never use (OR(adj) 1.76, 95% CI = 1.39-2.22), but this excess risk rapidly dropped to baseline levels when treatment had been discontinued >1 year ago. Concomitant use of antidepressants among current dopaminergic drug users further increased the risk of hip/femur fractures (OR(adj) 3.51, 95% CI = 2.10-5.87) while there was no additional risk with concomitant use of other psychotropics.

CONCLUSIONS

Although the observed association between dopaminergic drugs and fracture risk may not be entirely causal, due to absence of information on the (severity of the) underlying disease, fracture risk assessment may be warranted in elderly users of dopaminergic drugs.

The roles of the sympathetic nervous system in osteoporotic diseases: A review of experimental and clinical studies

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.

Evolution of β-blockers: from anti-anginal drugs to ligand-directed signalling

Sir James Black developed β-blockers, one of the most useful groups of drugs in use today. Not only are they being used for their original purpose to treat angina and cardiac arrhythmias, but they are also effective therapeutics for hypertension, cardiac failure, glaucoma, migraine and anxiety. Recent studies suggest that they might also prove useful in diseases as diverse as osteoporosis, cancer and malaria. They have also provided some of the most useful tools for pharmacological research that have underpinned the development of concepts such as receptor subtype selectivity, agonism and inverse agonism, and ligand-directed signalling bias. This article examines how β-blockers have evolved and indicates how they might be used in the future.

β2-Adrenergic receptor signaling in osteoblasts contributes to the catabolic effect of glucocorticoids on bone

The sympathetic nervous system is a physiological regulator of bone homeostasis. Autonomic nerves are indeed present in bone, bone cells express the β2-adrenergic receptors (β2AR), and pharmacological or genetic disruption of sympathetic outflow to bone induces bone gain in rodents. These recent findings implied that conditions that affect β2AR signaling in osteoblasts and/or sympathetic drive to bone may contribute to bone diseases. In this study, we show that dexamethasone stimulates the expression of the β2AR in differentiated primary calvarial osteoblasts, as measured by an increase in Adrβ2 mRNA and β2AR protein level after short-term dexamethasone treatment. Isoproterenol-induced cAMP accumulation and the expression of the β2AR target gene Rankl were also significantly increased after dexamethasone pretreatment, indicating that dexamethasone promotes the responsiveness of differentiated osteoblasts to adrenergic stimulation. These in vitro results led to the hypothesis that glucocorticoid-induced bone loss, provoked by increased endogenous or high-dose exogenous glucocorticoids given for the treatment of inflammatory diseases, might, at least in part, be mediated by increased sensitivity of bone-forming cells to the tonic inhibitory effect of sympathetic nerves on bone formation or their stimulatory effect on bone resorption. Supporting this hypothesis, both pharmacological and genetic β2AR blockade in mice significantly reduced the bone catabolic effect of high-dose prednisolone in vivo. This study emphasizes the importance of sympathetic nerves in the regulation of bone homeostasis and indicates that this neuroskeletal signaling axis can be modulated by hormones or drugs and contribute to enhance pathological bone loss.

Sympathetic neural influence on bone metabolism in microgravity (Review)

Bone loss is one of the most important complications for astronauts who are exposed to long-term microgravity in space and also for bedridden elderly people. Recent studies have indicated that the sympathetic nervous system plays a role in bone metabolism. This paper reviews findings concerning with sympathetic influences on bone metabolism to hypothesize the mechanism how sympathetic neural functions are related to bone loss in microgravity. Animal studies have suggested that leptin stimulates hypothalamus increasing sympathetic outflow to bone and enhances bone resorption through noradrenaline and β-adrenoreceptors in bone. In humans, even though there have been some controversial findings, use of β-adrenoblockers has been reported to be beneficial for prevention of osteoporosis and bone fracture. On the other hand, microneurographically-recorded sympathetic nerve activity was enhanced by exposure to microgravity in space as well as dry immersion or long-term bed rest to simulate microgravity. The same sympathetic activity became higher in elderly people whose bone mass becomes generally reduced. Our recent findings indicated a significant correlation between muscle sympathetic nerve activity and urinary deoxypyridinoline as a specific marker measuring bone resorption. Based on these findings we would like to propose a following hypothesis concerning the sympathetic involvement in the mechanism of bone loss in microgravity: An exposure to prolonged microgravity may enhance sympathetic neural traffic not only to muscle but also to bone. This sympathetic enhancement increases plasma noradrenaline level and inhibits osteogenesis and facilitates bone resorption through β-adrenoreceptors in bone to facilitate bone resorption to reduce bone mass. The use of β-adrenoblockers to prevent bone loss in microgravity may be reasonable.

Association between beta-blocker use and fracture risk: the Dubbo Osteoporosis Epidemiology Study

INTRODUCTION

In animal model, mice treated with beta-blockers (BB) had increased bone mass. In humans, high bone mass is associated with reduce fracture risk. The present study sought to test the hypothesis that BB use is associated with reduced fracture risk.

MATERIALS AND METHODS

Data from 3488 participants (1285 men) aged 50 years and above in the Dubbo Osteoporosis Epidemiology Study (DOES) were analyzed. Baseline characteristics of participants were obtained at the initial visit which had taken place between 1989 and 1993. Bone mineral density (BMD) at the lumbar spine and femoral neck was measured by dual energy X-ray absorptiometry (GE-LUNAR Corp, Madison, WI). Two hundred and sixty two (20%) men and 411 (19%) women had been on BB, as ascertained by direct interview and verification with medication history. The incidence of fragility fractures was ascertained during the follow-up period (1989-2008).

RESULTS

In men, BB use was associated with higher BMD at the femoral neck (0.96 versus 0.92 g/cm², P < 0.01), higher lumbar spine (1.32 versus 1.25 g/cm², P < 0.01), and lower fracture risk than those not on BB (odds ratio [OR]: 0.49; 95% CI: 0.32-0.75). In women, BB users also had higher femoral neck BMD (0.83 versus 0.81 g/cm², P < 0.01), higher lumbar spine BMD (1.11 versus 1.06 g/cm², P < 0.01), and lower risk of fracture than non-users (OR 0.68, 95% CI: 0.53-0.87). The associations between BB use and fracture risk were independent of age, BMD, and clinical risk factors. Subgroup analysis suggested that the association was mainly found in selective BB, not in non-selective BB.

CONCLUSION

Beta-blockers use, particularly selective BB, was associated with reduced fracture risk in both men and women, and the association was independent of BMD.

Investigational anabolic therapies for osteoporosis

IMPORTANCE OF THE FIELD

Anabolic therapy, or stimulating the function of bone-forming osteoblasts, is the preferred pharmacological intervention for osteoporosis.

AREAS COVERED IN THIS REVIEW

We reviewed bone anabolic agents currently under active investigation. The bone anabolic potential of IGF-I and parathyroid hormone-related protein is discussed in the light of animal data and human studies. We also discuss the use of antagonists of the calcium-sensing receptor (calcilytics) as orally administered small molecules capable of transiently elevating serum parathyroid hormone (PTH). Further, we reviewed novel anabolic agents targeting members of the wingless tail (Wnt) signaling family that regulate bone formation including DKK-1, sclerostin, Thp1, and glycogen synthase kinase 3beta. We have also followed up on the promise shown by beta-blockers in modulating the activity of sympathetic nervous system, thus affecting bone anabolism. We give critical consideration to neutralizing the activity of activin A, a negative regulator of bone mass by soluble activin receptor IIA, as a strategy to promote bone formation.

WHAT THE READER WILL GAIN

Update on various strategies to promote osteoblast function currently under evaluation.

TAKE HOME MESSAGE

In spite of favorable results in experimental models, none of these strategies has yet achieved the ultimate goal of providing an alternative to injectable PTH, the sole anabolic therapy in clinical use.

Use of organic nitrates and the risk of hip fracture: a population-based case-control study

CONTEXT

Use of organic nitrates has been associated with increased bone mineral density. Moreover, a large Danish case-control study reported a decreased fracture risk. However, the association with duration of nitrate use, dose frequency, and impact of discontinuation has not been extensively studied.

OBJECTIVE

Our objective was to evaluate the association between organic nitrates and hip fracture risk.

METHODS

A case-control study was conducted using the Dutch PHARMO Record Linkage System (1991-2002, n = 6,763 hip fracture cases and 26,341 controls). Cases had their first admission for hip fracture, whereas controls had not sustained any fracture after enrollment. Current users of organic nitrates were patients who had received a prescription within 90 d before the index date. The analyses were adjusted for disease and drug history.

RESULTS

Current use of nitrates was not associated with a decreased risk of hip fracture [adjusted odds ratio (OR) = 0.93; 95% confidence interval (CI) = 0.83-1.04]. Those who used as-needed medication only had a lower risk of hip fracture (adjusted OR = 0.83; 95% CI = 0.63-1.08) compared with users of maintenance medication only (adjusted OR = 1.17; 95% CI = 0.97-1.40). No association was found between duration of nitrate use and fracture risk.

CONCLUSIONS

Our overall analyses showed that risk of a hip fracture was significantly lower among users of as-needed organic nitrates, when compared with users of maintenance medication. Our analyses of hip fracture risks with duration of use did not further support a beneficial effect of organic nitrates on hip fracture, although residual confounding may have masked beneficial effects.