Newer drug treatments: Their effects on fracture prevention

Effects of Ethyl Acetate Extract of Poncirus trifoliata Fruit for Glucocorticoid-Induced Osteoporosis

Poncirus trifoliata fruit (PTF) affects the digestive and cardiovascular systems, and kidney function. The authors studied the effects of ethyl acetate (EtOAc) extract of PTF on the activities of osteoblasts and in an animal model. The main compounds of the EtOAc extract, naringin and poncirin have been confi rmed by HPLC and NMR analysis. Effects of osteoblastic differentiation were mea-sured by alkaline phosphatase (ALP) activity, osteopontin (OPN) protein expression and osteoprotegerin (OPG) mRNA expression in MC3T3-E1 cells. Also, osteoclast differentiation was measured by multinucleated cells (MNCs) formation through tartrate resistance acid phosphatase (TRAP)-positive staining. Bone mineral density (BMD) was measured before and after treatment with EtOAc extract of PTF in prednisolone-induced osteoporotic mice. Dexamethasone (DEX) decreased OPN and OPG expression level in MC3T3-E1 cells and ALP activity was decreased by DEX dose-dependently. EtOAc extract of PTF recovered the levels of ALP activity, and the expression of OPN and OPG in MC3T3-E1 cells treated with DEX. In osteoclast differentiation, multinucleated TRAP-positive cell formation was significantly suppressed by the EtOAc extract of PTF. Total body BMD was restored by EtOAc extract of PTF in prednisolone-induced osteoporotic mice. In conclusion, EtOAc extract of PTF recovered DEX-mediated deteriorations in osteoblastic and osteoclastic functions, and increased BMD in glucocorticoid-induced osteoporosis.

Bone loss in survival motor neuron (Smn(-/-) SMN2) genetic mouse model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is characterized by degenerating lower motor neurons and an increased incidence of congenital bone fractures. Survival motor neuron (SMN) levels are significantly reduced due to deletions/mutations in the telomeric SMN1 gene in these patients. We utilized the Smn(-/-) SMN2 mouse model of SMA to determine the functional role for SMN in bone remodelling. microCT analysis of lumber vertebrae, tibia and femur bones from SMA mice revealed an osteoporotic bone phenotype. Histological analysis demonstrated a thin porous cortex of cortical bone and thin trabeculae at the proximal end of the growth plate in the vertebrae of SMA mice compared to wild-type mice. Histochemical staining of the vertebrae showed the presence of abundant activated osteoclasts on the sparse trabeculae and on the endosteal surface of the thin cortex in SMA mice. Histomorphometric analysis of vertebrae from SMA mice showed an increased number of osteoclasts. Serum TRAcP5b and urinary NTx levels were elevated, consistent with increased bone resorption in these mice. SMA mice showed a significant decrease in the levels of osteoblast differentiation markers, osteocalcin, osteopontin and osterix mRNA expression; however, there were no change in the levels of alkaline phosphatase expression compared to WT mice. SMA mouse bone marrow cultures revealed an increased rate of osteoclast formation (54%) and bone resorption capacity (46%) compared to WT mice. Pre-osteoclast cells from SMA mice showed constitutive up-regulation of RANK receptor signalling molecules critical for osteoclast differentiation. Our results implicate SMN function in bone remodelling and skeletal pathogenesis in SMA. Understanding basic mechanisms of SMN action in bone remodelling may uncover new therapeutic targets for preventing bone loss/fracture risk in SMA.

Integrating a gender dimension into osteoporosis and fracture risk research

BACKGROUND

Sex (referring to the strict biological sense) and gender (referring to the sociocultural dimension) are major determinants of health and disease.

OBJECTIVE

This review examines similarities and differences between the sexes in the prevalence of osteoporosis and fractures, bone- and fall-related risk factors for incident fractures, and the possibilities of fracture prevention, as well as gender differences in the perception of osteoporosis.

METHODS

We reviewed recent English-language publications on sex and gender differences in the context of osteoporosis and fracture risk. We refer to several reviews that provide extensive reference lists on the topics discussed.

RESULTS

The incidence of fractures is higher in boys than in girls. The burden of fractures in adults increases with age, and it starts earlier and is higher in adult women than in adult men. With life expectancy increasing, the annual number of fractures is likely to increase substantially. Fractures in adults contribute to increased mortality (more in men than in women), increased morbidity (equal in men and women), and high costs (greater for women than for men). Adult men experience fewer fractures than women do. Men build larger bones with better microarchitecture while they are growing and thereafter have less increase in bone remodeling. Furthermore, they develop bone loss at a later age. Compared with their female counterparts, fewer older men are hypogonadic, and life expectancy is shorter for men than for women. There are multiple reasons for the differences in the incidences of fractures between men and women, related to the many factors associated with both bone and falls that influence fracture risk from the molecular and cellular level to the organ level. Sex hormones play a central and essential role in the physiology of bone by direct and indirect mechanisms (eg, by interfering with the growth hormone and insulin-like growth factor-1 axis). Case-finding strategies to identify patients at highest risk for fractures, including bone densitometry and clinical risk factors, are much better documented at the population level in women than in men. Drug therapies that reduce the risk of a broad spectrum of fractures, even in the short term, are more clearly demonstrated in randomized controlled studies in women than in men. Drug therapy is more widely available for women with osteoporosis,but it is rarely given to men with osteoporosis. Differences in the perception of osteoporosis between men and women are even less well documented.

CONCLUSIONS

In general, osteoporosis is underdiagnosed and undertreated in women but even more so in men, and is related to limits in the patient's and the physician's awareness at all clinical stages, from case finding to compliance with and persistence of therapy. Furthermore, the lay perception of a healthy lifestyle, the level of social isolation, networking within the health care system, and opportunities for screening appear to contribute to gender differences in participating in osteoporosis prevention and therapy. These aspects of health care deserve further attention and research.

Congenital bone fractures in spinal muscular atrophy: functional role for SMN protein in bone remodeling

Spinal muscular atrophy is the second most common fatal childhood disorder. Core clinical features include muscle weakness caused by degenerating lower motor neurons and a high incidence of bone fractures and hypercalcemia. Fractures further compromise quality of life by progression of joint contractures or additional loss of motor function. Recent observations suggest that bone disease in spinal muscular atrophy may not be attributed entirely to lower motor neuron degeneration. The presence of the spinal muscular atrophy disease-determining survival motor neuron gene (SMN), SMN expression, and differential splicing in bone-resorbing osteoclasts was recently discovered. Its ubiquitous expression and the differential expression of splice variants suggest that SMN has specific roles in bone cell function. SMN protein also interacts with osteoclast stimulatory factor. Mouse models of human spinal muscular atrophy disease suggest a potential role of SMN protein in skeletal development. Dual energy x-ray absorptiometry analysis demonstrated a substantial decrease in total bone area and poorly developed caudal vertebra in the mouse model. These mice also had pelvic bone fractures. Studies delineating SMN signaling mechanisms and gene transcription in a cell-specific manner will provide important molecular insights into the pathogenesis of bone disease in children with spinal muscular atrophy. Moreover, understanding bone remodeling in spinal muscular atrophy may lead to novel therapeutic approaches to enhance skeletal health and quality of life. This article reviews the skeletal complications associated with spinal muscular atrophy and describes a functional role for SMN protein in osteoclast development and bone resorption activity.

Picking a bone with contemporary osteoporosis management: Nutrient strategies to enhance skeletal integrity

Epidemic rates of osteoporosis in the western world have yielded intense efforts to develop management approaches to combat this potentially devastating disorder; recent research has unveiled innovative strategies which hold considerable promise for prevention of skeletal compromise and amelioration of suboptimal bone health. According to many algorithms and practice directives, the contemporary assessment and management of osteoporosis focuses heavily on determination of fracture risk and pharmaceutical intervention for those patients deemed to be at high risk. While routine recommendations for calcium and vitamin D have been incorporated into most regimens, disproportionately little attention has been given to recent research elucidating improved bone health and diminution in fracture rates experienced by patients receiving specific nutrients. In mainstream medical practice, clinical analysis and management of nutritional or dietary issues is sometimes perceived as unconventional, primitive or unsophisticated health care. Recent evidence-based research, however, supports intervention with adequate amounts of specific nutrients including vitamin D, strontium, vitamin K, and essential fatty acids in the prevention and primary management of osteoporosis.