Focus on primary care postmenopausal osteoporosis: an update

The regulation of MS-KIF18A expression and cross talk with estrogen receptor

This study provides a novel view on the interactions between the MS-KIF18A, a kinesin protein, and estrogen receptor alpha (ERα) which were studied in vivo and in vitro. Additionally, the regulation of MS-KIF18A expression by estrogen was investigated at the gene and protein levels. An association between recombinant proteins; ERα and MS-KIF18A was demonstrated in vitro in a pull down assay. Such interactions were proven also for endogenous proteins in MBA-15 cells were detected prominently in the cytoplasm and are up-regulated by estrogen. Additionally, an association between these proteins and the transcription factor NF-κB was identified. MS-KIF18A mRNA expression was measured in vivo in relation to age and estrogen level in mice and rats models. A decrease in MS-KIF18A mRNA level was measured in old and in OVX-estrogen depleted rats as compared to young animals. The low MS-KIF18A mRNA expression in OVX rats was restored by estrogen treatment. We studied the regulation of MS-KIF18A transcription by estrogen using the luciferase reporter gene and chromatin immuno-percipitation (ChIP) assays. The luciferase reporter gene assay demonstrated an increase in MS-KIF18A promoter activity in response to 10⁻⁸ M estrogen and 10⁻⁷M ICI-182,780. Complimentary, the ChIP assay quantified the binding of ERα and pcJun to the MS-KIF18A promoter that was enhanced in cells treated by estrogen and ICI-182,780. In addition, cells treated by estrogen expressed higher levels of MS-KIF18A mRNA and protein and the protein turnover in MBA-15 cells was accelerated. Presented data demonstrated that ERα is a defined cargo of MS-KIF18A and added novel insight on the role of estrogen in regulation of MS-KIF18A expression both in vivo and in vitro.

Ultrastructural changes in otoconia of osteoporotic rats

The etiology of benign paroxysmal positional vertigo (BPPV) remains obscure in many cases and women are affected more often than men. A recent prospective study, performed in women >50 years of age suffering from recurrent BPPV, showed associated osteopenia or osteoporosis in a large percentage of these patients. These results suggested the possible relationship between recurrent BPPV and a decreased fixation of calcium in bone in women >50 years. To test this hypothesis, an experimental study was performed in adult female rats. Utricular otoconia of female rats in which osteopenia/osteoporosis was induced by bilateral ovariectomy (OVX) were compared to those of sham-operated adult females rats (SHAM), as control group. FIRST STUDY: The morphology of theutricles of OVX and SHAM rats was analyzed with scanning electron microscopy. In osteopenic/osteoporotic rats, the density of otoconia (i.e. the number of otoconia per unit area) was decreased (p = 0.036)and their size was increased (p = 0.036) compared to the control group. SECOND STUDY: To test the role of calcium turnover in such morphological changes, utricular otoconia of 2 other groups of OVX and SHAM rats, previously injected with calcein subcutaneously, were examined by conventional and epifluorescence microscopy. In epifluorescence microscopy, labeling with calcein showed no significant fluorescence in either group. This finding was interpreted as a lack of external calcium turnover into otoconia of adult female rats. The ultrastructural modifications of otoconia in osteopenic/osteoporotic female adult rats as well as the role of estrogenic receptors in the inner ear are discussed. The possible pathophysiological mechanisms which support the relationship between recurrent BPPV in women and the disturbance of the calcium metabolism of osteopenia/osteoporosis are debated.

Update on the use of bisphosphonates in the management of postmenopausal osteoporosis by obstetricians-gynecologists

Obstetricians-gynecologists often have a special and long-term relationship with their patients and are ideally placed to assess their fracture risk and to institute appropriate therapy for osteoporosis. Assessment of risk factors according to the World Health Organization and more recent guidelines (e.g., age, smoking history, previous fracture, parental fracture, corticosteroid use, weight) enables the clinician to target patients for testing of bone mineral density by techniques such as dual-energy x-ray absorptiometry at the proximal femur. The current therapy of choice is an oral bisphosphonate, which has proven efficacy in increasing bone mineral density, reducing bone-turnover markers, and reducing fracture rates. Their main drawback is inconvenient dosing requirements, which necessitates taking the drug in the morning at least 30 minutes before the first meal or drink of the day; this may contribute to poor adherence with therapy and suboptimal outcomes. The availability of daily or weekly (alendronate and risedronate) or monthly (ibandronate) bisphosphonates means that patients can have therapy at their preferred frequency, and along with education regarding lifestyle issues such as nutrition, exercise, smoking, and alcohol use, and measures to reduce tripping in the home, should reduce the prevalence of osteoporotic fractures.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians Learning Objectives: After completion of this article, the reader should be able to recall that there are high-risk fracture patients, explain that Ob/Gyn physicians should target their diagnostic and treatment options to these patients, and state that there are ways that increase compliance to recommended bisphosphonates in addition to the recommended lifestyle changes.

SVEP1 expression is regulated in estrogen-dependent manner

The SVEP1 protein comprises modules related to the selectin super family and other motifs found in cell surface molecules. Earlier, we demonstrated that SVEP1 is expressed in osteogenic cells both in vivo and in vitro; in the current study we elaborate on the regulation of SVEP1 by 17beta-Estradiol (17betaE2). SVEP1 message is expressed in vivo by bone marrow cells of sham-operated rats, but not in estrogen-depleted ovariectomized (OVX) rats. We demonstrated that 17betaE2 treatment increases the level of the SVEP1 expression in cultured osteoblasts. SVEP1 was identified also in breast carcinoma (BC) cells known to reside in bone when metastasized from the primary tumor. SVEP1 expression was demonstrated by immunohistochemistry and fluorescence-activated cell sorting (FACS) on various BC cell lines. The chromatin immunoprecipitation (ChIP) assay was applied to analyze the estrogen receptor (ER) binding to the putative SVEP1 promoter. We demonstrated that treatment with 17betaE2 or ICI 182,780 affects this binding and regulates the mRNA and protein levels of SVEP1 in BC cells. We propose that SVEP1 may serve as a useful biomarker for studying the mechanism of cells interactions within the local microenvironment affected by estrogen.

Benign paroxysmal positional vertigo in older women may be related to osteoporosis and osteopenia

Benign paroxysmal positional vertigo (BPPV), so-called canalolithiasis and cupulolithiasis, usually occurs after head trauma or viral vestibular neuritis. In many cases, the cause remains obscure, and it often affects women more than 50 years old. The goal of this work was to study a possible relationship between BPPV and osteopenia or osteoporosis. Thirty-two women, whose ages ranged from 50 to 85 years (median age, 69 years), who had BPPV and were free of any other otoneurologic history, were selected. The diagnosis of osteopenia or osteoporosis was confirmed by a bone mineral density measurement made with dual x-ray absorptiometry of spine and hip (T-score). The BPPV was unilateral in 26 patients and bilateral in 6 patients. Our results showed osteopenia or osteoporosis in 24 of the 32 patients (75%) with BPPV. The T-scores were compared in 3 age groups to those of 83 healthy women. The patients with BPPV had a significantly lower (p < .026) T-score in all groups. Possible pathophysiological mechanisms are discussed to explain the apparent correlation between BPPV and osteopenia or osteoporosis.

Osteoporotic vertebral fractures

Osteoporosis is a significant public health problem. Vertebral fractures are the most common fracture in patients with osteoporosis, occurring in approximately 750,000 cases each year. The fractures may cause acute or chronic pain, reduce the quality of life, and shorten life expectancy. Several medications are available that reduce the risk of fracture. Vertebroplasty and kyphoplasty (balloon-inflated expansion of collapsed vertebrae followed by injection of bone cement) may reduce or relieve pain in selected patients. Although surgery is rarely necessary for the management of osteoporotic vertebral fractures, it may be indicated for other reasons. No studies have been conducted to determine if the outcome of spinal fusion is different in patients with osteoporosis and, if it is, whether management of the patient's osteoporosis will improve the outcome.