How to manage osteoporosis after the menopause

Hormone-Related and Drug-Induced Osteoporosis: A Cellular and Molecular Overview

Osteoporosis resulting from an imbalance of bone turnover between resorption and formation is a critical health issue worldwide. Estrogen deficiency following a nature aging process is the leading cause of hormone-related osteoporosis for postmenopausal women, while glucocorticoid-induced osteoporosis remains the most common in drug-induced osteoporosis. Other medications and medical conditions related to secondary osteoporosis include proton pump inhibitors, hypogonadism, selective serotonin receptor inhibitors, chemotherapies, and medroxyprogesterone acetate. This review is a summary of the cellular and molecular mechanisms of bone turnover, the pathophysiology of osteoporosis, and their treatment. Nuclear factor-κβ ligand (RANKL) appears to be the critical uncoupling factor that enhances osteoclastogenesis. In contrast, osteoprotegerin (OPG) is a RANKL antagonist secreted by osteoblast lineage cells. Estrogen promotes apoptosis of osteoclasts and inhibits osteoclastogenesis by stimulating the production of OPG and reducing osteoclast differentiation after suppression of IL-1 and TNF, and subsequent M-CSF, RANKL, and IL-6 release. It can also activate the Wnt signaling pathway to increase osteogenesis, and upregulate BMP signaling to promote mesenchymal stem cell differentiation from pre-osteoblasts to osteoblasts rather than adipocytes. Estrogen deficiency leads to the uncoupling of bone resorption and formation; therefore, resulting in greater bone loss. Excessive glucocorticoids increase PPAR-2 production, upregulate the expression of Dickkopf-1 (DKK1) in osteoblasts, and inhibit the Wnt signaling pathway, thus decreasing osteoblast differentiation. They promote osteoclast survival by enhancing RANKL expression and inhibiting OPG expression. Appropriate estrogen supplement and avoiding excessive glucocorticoid use are deemed the primary treatment for hormone-related and glucocorticoid-induced osteoporosis. Additionally, current pharmacological treatment includes bisphosphonates, teriparatide (PTH), and RANKL inhibitors (such as denosumab). However, many detailed cellular and molecular mechanisms underlying osteoporosis seem complicated and unexplored and warrant further investigation.

The midlife transition and the risk of cardiovascular disease and cancer Part I: magnitude and mechanisms

Heart disease and cancer are the leading causes of death in the United States. In women, the clinical appearance of both entities-coronary heart disease and cancer (breast, endometrium, and ovary)-escalate during the decades of the midlife transition encompassing the menopause. In addition to the impact of aging, during the interval between the age of 40 and 65 years, the pathophysiologic components of metabolic syndrome also emerge and accelerate. These include visceral adiposity (measured as waist circumference), hypertension, diabetes, and dyslipidemia. Osteoporosis, osteoarthritis, sarcopenia, depression, and even cognitive decline and dementia appear, and most, if not all, are considered functionally related. Two clinical reports confirm the interaction linking the emergence of disease: endometrial cancer and metabolic syndrome. One describes the discovery of unsuspected endometrial cancer in a large series of elective hysterectomies performed in aged and metabolically susceptible populations. The other is from the Women's Health Initiative Observational Study, which found a positive interaction between endometrial cancer and metabolic syndrome regardless of the presence or absence of visceral adiposity. Both provide additional statistical support for the long-suspected causal interaction among the parallel but variable occurrence of these common entities-visceral obesity, heart disease, diabetes, cancer, and the prevalence of metabolic syndrome. Therefore, 2 critical clinical questions require analysis and answers: 1: Why do chronic diseases of adulthood-metabolic, cardiovascular, endocrine-and, in women, cancers of the breast and endometrium (tissues and tumors replete with estrogen receptors) emerge and their incidence trajectories accelerate during the postmenopausal period when little or no endogenous estradiol is available, and yet the therapeutic application of estrogen stimulates their appearance? 2: To what extent should identification of these etiologic driving forces require modification of the gynecologist's responsibilities in the care of our patients in the postreproductive decades of the female life cycle? Part l of this 2-part set of "expert reviews" defines the dimensions, gravity, and interactive synergy of each clinical challenge gynecologists face while caring for their midlife (primarily postmenopausal) patients. It describes the clinically identifiable, potentially treatable, pathogenic mechanisms driving these threats to quality of life and longevity. Part 2 (accepted, American Journal of Obstetrics & Gynecology) identifies 7 objectives of successful clinical care, offers "triage" prioritization targets, and provides feasible opportunities for insertion of primary preventive care initiatives. To implement these goals, a reprogrammed, repurposed office visit is described.

The midlife transition and the risk of cardiovascular disease and cancer Part II: strategies to maximize quality of life and limit dysfunction and disease

Chronic dysfunction, disabilities, and complex diseases such as cardiovascular disease, diabetes mellitus type 2, osteoporosis and certain cancers, among other burdens, emerge and accelerate in midlife women. Previously in part l, we described the clinical and laboratory research findings that more readily explain and clarify the underlying pathogenetic mechanisms driving these clinical burdens, including new findings on how in particular visceral obesity and the emergence and acceleration of various components of metabolic syndrome-glucotoxicity and lipotoxicity-and a chronic systemic inflammatory state abetted by the loss of ovarian production of estradiol and the inevitable inroads of aging generate this spectrum of clinical problems. These research insights translate into opportunities for effective care strategies leading to prevention, amelioration, possible correction, and enhanced quality of life. To achieve these goals, updated detailed diagnostic, management, and therapeutic guidelines implemented by a reprogrammed and repurposed "menopause" office visit are described. A triage mechanism-when to refer to other specialists for further care-is emphasized. The previously polarized views of menopausal hormone therapy have narrowed significantly, leading to the construction of a more confident, unified, and wider clinical application. Accordingly, a menopausal hormone therapy program providing maximum benefit and minimum risk, accompanied by an algorithm for enhanced shared decision making, is included.

Prevention of diseases after menopause

Women may expect to spend more than a third of their lives after menopause. Beginning in the sixth decade, many chronic diseases will begin to emerge, which will affect both the quality and quantity of a woman's life. Thus, the onset of menopause heralds an opportunity for prevention strategies to improve the quality of life and enhance longevity. Obesity, metabolic syndrome and diabetes, cardiovascular disease, osteoporosis and osteoarthritis, cognitive decline, dementia and depression, and cancer are the major diseases of concern. Prevention strategies at menopause have to begin with screening and careful assessment for risk factors, which should also include molecular and genetic diagnostics, as these become available. Identification of certain risks will then allow directed therapy. Evidence-based prevention for the diseases noted above include lifestyle management, cessation of smoking, curtailing excessive alcohol consumption, a healthy diet and moderate exercise, as well as mentally stimulating activities. Although the most recent publications from the follow-up studies of the Women's Health Initiative do not recommend menopause hormonal therapy as a prevention strategy, these conclusions may not be fully valid for midlife women, on the basis of the existing data. For healthy women aged 50-59 years, estrogen therapy decreases coronary heart disease and all-cause mortality; this interpretation is entirely consistent with results from other randomized, controlled trials and observational studies. Thus. as part of a comprehensive strategy to prevent chronic disease after menopause, menopausal hormone therapy, particularly estrogen therapy may be considered as part of the armamentarium.

Expression of TGF-β1 in the blood during fracture repair in an estrogen-deficient rat model

OBJECTIVES

Previous studies have reported that osteoporosis due to estrogen deficiency influences fracture healing. Transforming growth factor (TGF-b) has been found to be involved in fracture healing via the regulation of the differentiation and activation of osteoblasts and osteoclasts. The current study aimed to determine the effects of estrogen on the expression of TGF-β1 during fracture healing in ovariectomized rats.

METHODS

Thirty female Sprague-Dawley rats weighing 200-250 g were assigned to: (i) a sham-operated group that was given a normal saline; (ii) an ovariectomized control group that was given a normal saline; or (iii) an ovariectomized + estrogen (100 mg/kg/day) group that was treated with conjugated equine estrogen. The right femur of all rats was fractured, and a Kirschner wire was inserted six weeks post-ovariectomy. Treatment with estrogen was given for another six weeks post-fracture. At the end of the study, blood samples were taken, and the right femur was harvested and subjected to biomechanical strength testing.

RESULTS

The percentage change in the plasma TGF-β1 level before treatment was significantly lower in the ovariectomized control and estrogen groups when compared with the sham group (p<0.001). After six weeks of treatment, the percentage change in the plasma TGF-β1 level in the estrogen group was significantly higher compared with the level in the ovariectomized control group (p = 0.001). The mean ultimate force was significantly increased in the ovariectomized rats treated with estrogen when compared with the ovariectomized control group (p = 0.02).

CONCLUSION

These data suggest that treatment with conjugated equine estrogen enhanced the strength of the healed bone in estrogen-deficient rats by most likely inducing the expression of TGF-β1.

Piper sarmentosum enhances fracture healing in ovariectomized osteoporotic rats: a radiological study

INTRODUCTION

Osteoporotic fractures are common during osteoporotic states. Piper sarmentosum extract is known to possess antioxidant and anti-inflammatory properties.

OBJECTIVES

To observe the radiological changes in fracture calluses following administration of a Piper sarmentosum extract during an estrogen-deficient state.

METHODS

A total of 24 female Sprague-Dawley rats (200-250 g) were randomly divided into 4 groups: (i) the sham-operated group; (ii) the ovariectomized-control group; (iii) the ovariectomized + estrogen-replacement therapy (ovariectomized-control + estrogen replacement therapy) group, which was supplemented with estrogen (100 μg/kg/day); and (iv) the ovariectomized + Piper sarmentosum (ovariectomized + Piper sarmentosum) group, which was supplemented with a water-based Piper sarmentosum extract (125 mg/kg). Six weeks after an ovariectomy, the right femora were fractured at the mid-diaphysis, and a K-wire was inserted. Each group of rats received their respective treatment for 6 weeks. Following sacrifice, the right femora were subjected to radiological assessment.

RESULTS

The mean axial callus volume was significantly higher in the ovariectomized-control group (68.2 ± 11.74 mm³) than in the sham-operated, estrogen-replacement-therapy and Piper sarmentosum groups (20.4 ± 4.05, 22.4 ± 4.14 and 17.5 ± 3.68 mm³, respectively). The median callus scores for the sham-operated, estrogen-replacement-therapy and Piper sarmentosum groups had median (range, minimum - maximum value) as 1.0 (0 - 2), 1.0 (1 - 2) and 1.0 (1 - 2), respectively, which were significantly lower than the ovariectomized-control group score of 2.0 (2 - 3). The median fracture scores for the sham-operated, estrogen-replacement-therapy and Piper sarmentosum groups were 3.0 (3 - 4), 3.0 (2 - 3) and 3.0 (2 - 3), respectively, which were significantly higher than the ovariectomized-control group score of 2.0 (1 - 2) (p<0.05).

CONCLUSION

The Piper sarmentosum extract improved fracture healing, as assessed by the reduced callus volumes and reduced callus scores. This extract is beneficial for fractures in osteoporotic states.

Isosorbide mononitrate versus alendronate for postmenopausal osteoporosis

OBJECTIVE

To compare the effectiveness, safety, and affordability of isosorbide mononitrate with alendronate for postmenopausal osteoporosis.

METHODS

A randomized controlled trial of 60 postmenopausal women with osteoporosis. Participants were randomly assigned to receive either 20 mg daily of isosorbide mononitrate or 70 mg weekly of alendronate for 12 months. Bone mineral density (BMD) was measured using dual X-ray absorptiometry (DXA) at baseline and after 12 months.

RESULTS

Both groups showed significant improvement in BMD. Isosorbide mononitrate yielded a comparable effect to alendronate for BMD and T-score at the end of the follow-up period. For BMD and T score the mean differences between the 2 groups were -0.005 (95% CI, -0.02 to 0.03) and 0.31 (95% CI, -0.03 to 0.64), respectively. A 10.8% and 12.1% change in BMD after 12 months was seen for isosorbide mononitrate and alendronate, respectively.

CONCLUSION

Isosorbide mononitrate is comparable to alendronate. Nitric oxide donors may be an effective and affordable therapy to improve bone mineral density.

Protective effect of apigenin on ovariectomy-induced bone loss in rats

Recent studies have shown that apigenin not only inhibits bone resorption by osteoclasts but also induces osteoclast apoptosis. However, the influence of apigenin on osteoporosis in animals is relatively unknown. The purpose of this study was to examine the bone-protective effects of apigenin in estrogen-deficient ovariectomized rats. Three-month-old female Sprague-Dawley rats were either sham-operated or ovariectomized and fed AIN-93G diet for 7 weeks to induce bone loss. To confirm bone loss, we used a newly developed non-invasive technique involving zoom-in micro-computed tomography. Apigenin was administered at a dose of 10 mg/kg three times a week for 15 weeks. Our results indicate that apigenin not only increased the mineral content and density of the trabecular bone at the neck of the left femur, but also decreased body weight and dietary consumption. Moreover, our biochemical results indicate that apigenin has a positive effect on bone turnover. The present data suggest that apigenin should be considered for use in the treatment of osteoporosis.

Redefining osteoporosis treatment: Who to treat and how long to treat

Osteoporosis is a common disease that is associated with increased risk of fractures and serious clinical consequences. Bone mineral density (BMD) testing is used to diagnose osteoporosis, estimate the risk of fracture, and monitor changes in BMD over time. Combining clinical risk factors for fracture with BMD is a better predictor of fracture risk than BMD or clinical risk factors alone. Methodologies are being developed to use BMD and validated risk factors to estimate the 10-year probability of fracture, and then combine fracture probability with country-specific economic assumptions to determine cost-effective intervention thresholds. The decision to treat is based on factors that also include availability of therapy, patient preferences, and co-morbidities. All patients benefit from nonpharmacological lifestyle treatments such a weight-bearing exercise, adequate intake of calcium and vitamin D, fall prevention, avoidance of cigarette smoking and bone-toxic drugs, and moderation of alcohol intake. Patients at high risk for fracture should be considered for pharmacological therapy, which can reduce fracture risk by about 50%.

New mechanisms and targets in the treatment of bone fragility

Bone modelling and remodelling are cell-mediated processes responsible for the construction and reconstruction of the skeleton throughout life. These processes are chiefly mediated by locally generated cytokines and growth factors that regulate the differentiation, activation, work and life span of osteoblasts and osteoclasts, the cells that co-ordinate the volumes of bone resorbed and formed. In this way, the material composition and structural design of bone is regulated in accordance with its loading requirements. Abnormalities in this regulatory system compromise the material and structural determinants of bone strength producing bone fragility. Understanding the intercellular control processes that regulate bone modelling and remodelling is essential in planning therapeutic approaches to prevention and treatment of bone fragility. A great deal has been learnt in the last decade. Clinical trials carried out exclusively with drugs that inhibit bone resorption have identified the importance of reducing the rate of bone remodelling and so the progression of bone fragility to achieved fracture reductions of approx. 50%. These trials have also identified limitations that should be placed upon interpretation of bone mineral density changes in relation to treatment. New resorption inhibitors are being developed, based on mechanisms of action that are different from existing drugs. Some of these might offer resorption inhibition without reducing bone formation. More recent research has provided the first effective anabolic therapy for bone reconstruction. Daily injections of PTH (parathyroid hormone)-(1–34) have been shown in preclinical studies and in a large clinical trial to increase bone tissue mass and reduce the risk of fractures. The action of PTH differs from that of the resorption inhibitors, but whether it is more effective in fracture reduction is not known. Understanding the cellular and molecular mechanisms of PTH action, particularly its interactions with other pathways in determining bone formation, is likely to lead to new therapeutic developments. The recent discovery through mouse genetics that PTHrP (PTH-related protein) is a crucial bone-derived paracrine regulator of remodelling offers new and interesting therapeutic targets.

[Antiosteoporosis medication: useful monitoring, and how long should such treatment be continued?]

The improved options for effective treatment of osteoporosis and the shift to treatment strategies based on each patient's absolute fracture risk raise new questions in daily clinical care. Which patient should have what osteoprotective therapy and when and for how long? What techniques can be used to assess the individual effects of novel therapeuties? Are the results yielded by these techniques affected by concomitant factors? What specific characteristics need to be taken account of in rheumatological clinics and how should we deal with these? What is the impact of patient compliance on the assessment of therapeutic effects? This review is intended to shed some light on these questions and on the new DVO guidelines in daily practice with reference to the ambulatory setting.