The use of intermittent human parathyroid hormone as a treatment for osteoporosis

Osteoporosis-pseudoglioma syndrome in four new patients: identification of two novel LRP5 variants and insights on patients' management using bisphosphonates therapy

This study describes the clinical, radiological, and molecular data of four new patients with osteoporosis-pseudoglioma syndrome and assesses their response to bisphosphonate therapy.

INTRODUCTION

Osteoporosis-pseudoglioma syndrome (OPPG) is a very rare disorder characterized mainly by severe juvenile osteoporosis and congenital blindness. OPPG is caused by biallelic mutations in the gene encoding low-density lipoprotein receptor-related protein 5 (LRP5).

METHODS

We present the clinical, radiological, and molecular findings of four new patients with OPPG from Egypt. We also assessed patients' response to oral and intravenous bisphosphonate therapy.

RESULTS

All patients had reduced bone mineral density (BMD) with variable number of fractures per year, in addition to bone abnormalities and the characteristic eye phenotype associated with OPPG. Mutation analyses of LRP5 gene revealed three different homozygous variants including two novel ones, c.7delG (p.A3Qfs*80) and c.3280G > A (p.E1094K). The c.3280G > A (p.E1094K) was recurrent in two unrelated patients who shared a unique haplotype suggesting a possible founder effect. The use of bisphosphonate therapy was beneficial; however, intravenous bisphosphonate administration led to a more favorable response.

CONCLUSION

Our study described the phenotypic and genetic features of four patients with OPPG and identified two new LRP5 variants, thus expanding the mutational spectrum of OPPG. In addition, our study reinforces the efficiency of using intravenous bisphosphonates in the management of patients with OPPG.

Management of primary and secondary osteoporosis in children

Osteoporosis in children differs from adults in terms of definition, diagnosis, monitoring and treatment options. Primary osteoporosis comprises primarily of osteogenesis imperfecta (OI), but there are significant other causes of bone fragility in children that require treatment. Secondary osteoporosis can be a result of muscle disuse, iatrogenic causes, such as steroids, chronic inflammation, delayed or arrested puberty and thalassaemia major. Investigations involve bone biochemistry, dual-energy X-ray absorptiometry scan for bone densitometry and vertebral fracture assessment, radiographic assessment of the spine and, in some cases, quantitative computed tomography (QCT) or peripheral QCT. It is important that bone mineral density (BMD) results are adjusted based on age, gender and height, in order to reflect size corrections in children. Genetics are being used increasingly for the diagnosis and classification of various cases of primary osteoporosis. Bone turnover markers are used less frequently in children, but can be helpful in monitoring treatment and transiliac bone biopsy can assist in the diagnosis of atypical cases of osteoporosis. The management of children with osteoporosis requires a multidisciplinary team of health professionals with expertise in paediatric bone disease. The prevention and treatment of fragility fractures and improvement of the quality of life of patients are important aims of a specialised service. The drugs used most commonly in children are bisphosphonates, that, with timely treatment, can give good results in improving BMD and reshaping vertebral fractures. The data regarding their effect on reducing long bone fractures are equivocal. Denosumab is being used increasingly for various conditions with mixed results. There are more drugs trialled in adults, but these are not yet licenced for children. Increasing awareness of risk factors for paediatric osteoporosis, screening and referral to a specialist team for appropriate management can lead to early detection and treatment of asymptomatic fractures and prevention of further bone damage.

Effects of teriparatide on bone mineral density and quality of life in Duchenne muscular dystrophy related osteoporosis: a case report

Duchenne muscular dystrophy (DMD) is an X-linked recessive muscle disease characterized by secondary osteoporosis and increased fractures. We describe the case of a 20-year-old boy with DMD suffering from back pain due to multiple vertebral fractures who was treated with teriparatide. Improvement of bone density, pain, and quality of life was achieved. DMD is an X-linked recessive muscle disease with secondary osteoporosis and related frequently occurring fractures. To date, only bisphosphonates have been used to treat osteoporosis in DMD. Black bear parathyroid hormone has been previously reported to enhance bone mass in the dystrophin-deficient mouse. This study reports the positive effect of osteoanabolic treatment with once-daily recombinant human parathyroid hormone 1-34 (rhPTH 1-34, teriparatide) in a 20-year-old DMD boy suffering from multiple vertebral fractures causing back pain. Bone formation and resorption markers (osteocalcin and C-telopeptide of type I collagen, respectively), as expected, increased within 6 months and intensity of back pain early decreased, with no pain reported after 6 months at visual analog scale. Over a 18-month period of treatment with teriparatide, bone mineral density and quality of life, assessed by the 36-item short-form questionnaire, considerably improved and no side effects were reported. Further studies on large cohorts are warranted to test the efficacy of this promising treatment for DMD related osteoporosis.

Dried plum's unique capacity to reverse bone loss and alter bone metabolism in postmenopausal osteoporosis model

Interest in dried plum has increased over the past decade due to its promise in restoring bone and preventing bone loss in animal models of osteoporosis. This study compared the effects of dried plum on bone to other dried fruits and further explored the potential mechanisms of action through which dried plum may exert its osteoprotective effects. Adult osteopenic ovariectomized (OVX) C57BL/6 mice were fed either a control diet or a diet supplemented with 25% (w/w) dried plum, apple, apricot, grape or mango for 8 weeks. Whole body and spine bone mineral density improved in mice consuming the dried plum, apricot and grape diets compared to the OVX control mice, but dried plum was the only fruit to have an anabolic effect on trabecular bone in the vertebra and prevent bone loss in the tibia. Restoration of biomechanical properties occurred in conjunction with the changes in trabecular bone in the spine. Compared to other dried fruits in this study, dried plum was unique in its ability to down-regulate osteoclast differentiation coincident with up-regulating osteoblast and glutathione (GPx) activity. These alterations in bone metabolism and antioxidant status compared to other dried fruits provide insight into dried plum's unique effects on bone.

Pharmacodynamic responses to combined treatment regimens with the calcium sensing receptor antagonist JTT-305/MK-5442 and alendronate in osteopenic ovariectomized rats

Parathyroid hormone (PTH) is the anabolic standard of care for patients with severe osteoporosis. The CaSR allosteric antagonist JTT-305/MK-5442, a PTH secretagogue, could offer an oral osteoanabolic treatment alternative for postmenopausal women with osteoporosis. Here we disclose the pharmacokinetic profile of JTT-305/MK-5442 and its activity on bone remodeling in ovariectomized (OVX) osteopenic rats. Daily treatments (0.3 to 2.4 mg/kg/d) for 12 weeks resulted in plateaued BMD increases (3.8 to 5.3%) at axial and appendicular skeletal sites. However, treatment effects were not statistically significant, in agreement with effects seen in animals treated with low dose PTH (1-84) (5 μg/kg/d). In a consecutive study we tested JTT-305/MK-5442 effects on bone formation in OVX-rats challenged with combined alendronate (ALN) treatment paradigms. At 7 month, JTT-305/MK-5442 treatment significantly increased BMD in lumbar vertebrae (LV), while no change in BMD was observed in femora or tibiae. ALN add-on co-treatment produced incremental increases in LV, distal femur (DF) and proximal tibia (PT) BMD over the respective ALN control. Histological analyses confirmed modest increases in mineralized surface (MS/BS) and bone formation rate (30.5±1.9%) on trabecular surfaces by JTT-305/MK-5442. As expected, ALN administration profoundly reduced bone formation, however, JTT-305/MK-5442 significantly stimulated MS/BS and BFR in ALN treated groups. In summary, JTT-305/MK-5442 acts as a PTH secretagogue in the osteopenic OVX-rat, eliciting consistent, though modest effects on remediation of BMD due to estrogen depletion. Induction of bone formation by JTT-305/MK-5442 at trabecular bone surfaces appears to be resilient to ALN-mediated suppression of bone formation. This study provides for the first time, a mechanistic evaluation of combination treatment of a PTH secretagogue with ALN.

Cnot7-null mice exhibit high bone mass phenotype and modulation of BMP actions

Cnot7 is a recently identified regulator of spermatogenesis in adult mice. Because Cnot7 binds to Tob, a BMP inhibitor shown to be involved in bone metabolism, we examined whether Cnot7 is involved in bone mass regulation by using adult Cnot7 deficient mice. Cnot7-/- mice exhibited a high bone mass phenotype. This was associated with an increase in bone formation rate but not with any alteration in bone resorption parameters. On BMP treatment, Cnot7-/- cells expressed higher levels of alkaline phosphatase compared with control cells. Direct BMP2 injection induced larger bone mass in Cnot7-/- calvaria than control in vivo. These observations revealed that Cnot7 is an endogenous suppressor of bone mass and inhibits BMP actions in osteoblasts.

INTRODUCTION

The molecular mechanisms involved in the determination of bone mass have been gradually understood based on recent analyses. Cnot7 (Ccr4-Not complex 7) is a component of transcriptional Ccr4-Not complex, is conserved from yeast to human, and binds to Tob, but its function in bone is not understood.

MATERIALS AND METHODS

To elucidate the role of involvement of Cnot7 in bone mass determination, we examined the bone of adult male Cnot7-null and heterozygous mice based on microCT analyses, histomorphometry, cell cultures, and in vivo BMP assays.

RESULTS

Cnot7-/- mice showed an increase in bone mass levels by >50% compared with controls. Analyses of the histomorphometric parameters indicated that bone formation activity in Cnot7-/- mice was enhanced, whereas bone resorption activity was not altered. These effects on osteoblasts were cell autonomous because mineralized nodule formation was enhanced in the cultures of bone marrow cells prepared from Cnot7-/- mice. In vitro analyses to elucidate Cnot7 effects revealed that BMP-induced expression of alkaline phosphatase in Cnot7-/- calvaria-derived osteoblastic cells was enhanced compared with controls. Moreover, BMP injection-induced new bone formation in vivo was enhanced in Cnot7-/- mice.

CONCLUSIONS

These observations indicated that Cnot7 is an endogenous suppressor of bone mass in adult mice and inhibits BMP actions.

Effects of hPTH (1-34) and Gosha-jinki-gan on the trabecular bone microarchitecture in ovariectomized rat tibia

Although human parathyroid hormone (1-34) [hPTH (1-34)] was reported to improve osteoporotic bone loss, little is known about the anti-osteoporotic effect of the traditional Chinese medicine, Gosha-jinki-gan (GJG). The purpose of this present study was to clarify and compare the effects of hPTH (1-34) and GJG on trabecular bone microarchitecture in ovariectomized (OVX) rat tibia by using microcomputed tomography (micro-CT). Thirty 12-week-old Sprague-Dawley female rats were underwent ovariectomy (OVX) or sham operation. Four weeks later, the ovariectomized rats were further divided into OVX, OVX + PTH, and OVX + GJG groups. hPTH (1-34) was administered subcutaneously at a dose of 20 microg/kg, 3 times/week, and OVX + GJG group received 0.05% aqueous solution of GJG as the only drinking fluid for 8 weeks respectively. The three-dimensional (3D) trabecular microarchitecture of the bone in the proximal tibial metaphysis was evaluated by micro-CT. In the OVX + PTH group, trabecular bone volume (BV/ TV), number (Tb.N) and thickness (Tb.Th) were significantly increased, structure model index (SMI) and trabecular bone pattern factor (TBPf) decreased when compared with the OVX group. In comparison to the OVX group, BV/TV and Tb.N were significantly greater, while SMI and TBPf had no marked changes in the OVX + GJG group. These results suggest that the administration of hPTH (1-34) restore the trabecular bone volume and improve the microstuctural property as well, while GJG reduce the bone loss without affecting its microstructural property in ovariectomized rats.

Parathyroid hormone induces receptor activity modifying protein-3 (RAMP3) expression primarily via 3',5'-cyclic adenosine monophosphate signaling in osteoblasts

Parathyroid hormone (PTH) has significant anabolic and catabolic effects on bone. We hypothesize that PTH-induced primary response genes are important determinants of osteoblast function. PTH induces osteoblastic gene expression through PTHR1, a heptahelical receptor that triggers cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA), protein kinase C (PKC), and calcium signaling. By using representational difference analysis we found that receptor activity modifying protein-3 (RAMP3) is a PTH-induced primary response gene in osteoblastic cells. RAMP3 is a coactivator that directs calcitonin receptor (CTR) and CTR-like receptor (CRLR) glycosylation, trafficking, and ligand-binding specificity. Our purpose was to characterize PTH-induced RAMP3 messenger ribonucleic acid (mRNA) levels in primary mouse osteoblasts (MOBs) and to determine which signaling pathway mediates this effect. 10 nM PTH maximally induced RAMP3 mRNA levels in MOBs at 4 hours. Protein synthesis inhibition with 3 microg/mL cycloheximide did not affect PTH-induced RAMP3 mRNA levels. Selective activation of cAMP-PKA signaling with, 10 microM forskolin (FSK) and PKC signaling with 1 microM phorbol 12-myristate 13-acetate (PMA) significantly increased RAMP3 mRNA levels, whereas 1 microM ionomycin (a calcium ionophore) had no effect. Pretreatment with 30 microM H89, a PKA inhibitor, significantly blocked PTH- and FSK-induced RAMP3 mRNA levels. Pretreatment with 1 microM PMA, which depletes PKC, had no effect on PTH- and FSK-induced RAMP3 mRNA levels but blocked PMA-induced RAMP3 mRNA levels. 100 nM PTH (3-34), which activates PKC and calcium but not PKA, had no effect on RAMP3 mRNA levels. These findings indicate that RAMP3 is a PTH-induced primary response gene in primary MOBs and that PTH regulates RAMP3 gene expression primarily through the cAMP-PKA pathway.

Stretch-induced PTH-related protein gene expression in osteoblasts

Mechanical forces play a critical role in regulating skeletal mass and structure. We report that mechanical loading induces PTHrP in osteoblast-like cells and that TREK-2 stretch-activated potassium channels seem to be involved in this induction. Our data suggest PTHrP as a candidate endogenous mediator of the anabolic effects of mechanical force on bone.

INTRODUCTION

Mechanical force has anabolic effects on bone. The PTH-related protein (PTHrP) gene is known to be mechanically inducible in smooth muscle cells throughout the organism, and N-terminal PTH and PTHrP products have been reported to have anabolic effects in bone. We explored the idea that PTHrP might be a candidate mediator of the effects of mechanical force on bone.

MATERIALS AND METHODS

Mechanical loading was applied by swelling osteoblast-like cells in hypotonic solution and/or by application of cyclical stretch through a FlexerCell apparatus. RNase protection assay and real-time quantitative PCR analysis were used to assay PTHrP gene expression.

RESULTS AND CONCLUSION

Stretching UMR201-10B osteoblast-like cells by swelling in hypotonic solutions rapidly increased PTHrP mRNA. This induction was insensitive to gadolinium and nifedipine, to the removal of extracellular calcium, and to depletion of endoplasmic reticulum calcium, indicating that neither stretch-activated cation channels, L-type calcium channels, nor ER calcium is involved in the induction of PTHrP. The TREK family potassium channels are activated by both stretch and intracellular acidosis, and we identified these channels in osteoblast-like cells by PCR. Intracellular acidification increased PTHrP mRNA expression in UMR-201-10B cells, and siRNA targeted against the TREK-2 gene reduced endogenous TREK-2 expression and dampened PTHrP mRNA induction. Cyclical stretch also induced PTHrP in UMR-201-10B osteoblast-like cells and in MLO-A5 post-osteoblast-pre-osteocyte cells, the latter a stage in the osteoblastic differentiation program that is likely to be a key target of force in vivo. Our evidence suggests PTHrP as a candidate mediator of the anabolic effects of mechanical force on bone.

Prostaglandins E(2) and F(2alpha) enhance differentiation of cementoblastic cells

BACKGROUND

The prostaglandins (PG) E(2) and PGF(2alpha) are important cytokines in periodontal physiology and pathology. PGE(2) and PGF(2alpha) alter cell function by binding and activating the plasmamembrane G-protein-coupled PG receptors. In this study, we examined the PGE(2) and PGF(2alpha) effects on the immortalized cementoblastic OCCM cells.

METHODS

Confluent OCCM cells were treated with PGE(2), PGF(2alpha), specific activators/inhibitors of the EP prostanoid receptors, a specific activator of the FP prostanoid receptor, and direct activators/inhibitors of the protein kinase C (PKC) signaling pathway. Mineral nodule formation was assessed by the von Kossa stain.

RESULTS

PGE(2) and PGF(2alpha) significantly increased mineralization of OCCM cells. The EP1 and EP3 PG receptor activators 16,16-dimethyl-prostaglandin E(2) and sulprostone, also increased mineralization. In contrast, specific activators of the EP2 or the EP2/EP3/EP4 receptors did not have any effect. Fluprostenol, a specific activator of the FP receptor, significantly increased mineralization of OCCM cells. FP and EP (1 or 3) receptors signal through activation of the protein kinase C (PKC) pathway. Indeed, phorbol 12-myristate 13-acetate (PMA), a direct activator of the PKC pathway, significantly increase OCCM mineralization, while pre-treatment of OCCM cells with the PKC inhibitor GF109203x (bisindolylmaleimide) significantly decreased mineralization.

CONCLUSION

We conclude that PGE(2) and PGF(2alpha) exert an anabolic effect on OCCM mineralization through activation of PKC signaling.

Osteoporosis in chronically ill children

Gains in bone mass are very rapid during adolescence and peak bone mass, the most important determinant of osteoporosis, is attained by early adulthood. Glucocorticoids, widely used in children with chronic illness, are known to impact bone mass and quality. In addition, disease and treatment-related factors, nutrient and hormone deficiencies and decreased physical activity may all negatively affect bone mass accrual. Although decreased bone density is increasingly recognized in chronically ill children, current knowledge of the epidemiology, diagnosis and optimal treatment of pediatric secondary osteoporosis is limited. In addition to bone densitometry, biochemical and radiographic tests should be used in the diagnosis of osteoporosis. Bone histomorphometry may be needed in selected situations. At risk children should be advised to ensure sufficient calcium and vitamin D intake and weight bearing physical activity. Growth and pubertal development require careful assessment because of their close correlation with bone formation. Given limited experience with bisphosphonates, it seems prudent to target antiresorptive therapy to those children who have developed symptomatic disease. Ideally this should be done in controlled settings. Early identification and adequate intervention, in selected cases with bisphosphonates, is needed in order to prevent deleterious skeletal complications of osteoporosis in chronically ill children.

Effect of intermittent PTH administration in the periodontitis-associated bone loss in ovariectomized rats

OBJECTIVE

Parathyroid hormone intermittent administration has been considered to treat bone mass decrease in osteoporotic individuals. The present study evaluates whether PTH can affect alveolar bone loss in ovariectomized rats, since estrogen deficiency has been proposed as a risk factor for periodontal disease.

DESIGN AND METHODS

Thirty female rats were set in groups: ovariectomized (Ovx) and Sham operated. Ovx were divided in two groups: Ovx-PTH (1-34) treated and Ovx, which received vehicle. After 1 week, cotton ligature was placed around one lower first molar of all animals to induce periodontal disease. Ovx treated received PTH doses of 40 microg/kg, three times a week for 30 days. After that, the animals were sacrificed, the mandibles extracted, X-rayed and samples prepared for histological evaluation. Histomorphometry was performed using image analyzer software. Scanning electron microscopy (SEM) of the tibias was also performed in all animals to evaluate possible changes in bone structure caused by the estrogen deficiency. Optical densities of the radiographs were measured by aluminum step-wedge equivalent thickness.

RESULTS

Histomorphomery indicated the anabolic PTH effect in ovariectomized rats with significant inhibition of periodontitis manifestation (p<0.05) thus neutralizing the periodontitis inductor effects. The photo densitometry showed a lower mandibular optical density in the ovariectomized group that did not receive PTH (p<0.05). SEM image confirmed the early effect of estrogen deficiency in osseous tissue and PTH anabolic effect.

CONCLUSION

PTH systemic intermittent administration was able to reduce alveolar bone loss in ovariectomized rats, despite the presence of a periodontal disease inductor and estrogen deficiency.

Hormone replacement therapy in women with spinal cord injury – a survey with literature review

STUDY DESIGN

Postal questionnaire survey.

OBJECTIVE

To examine the current use of hormone replacement therapy (HRT) in a sample of menopausal women with spinal cord injury (SCI).

SETTING

National Spinal Injuries Centre (NSIC), Stoke Mandeville Hospital, Aylesbury, UK.

METHOD

A postal questionnaire was sent to 94 women from the NSIC patient database who met the study inclusion criteria (wheelchair dependent, aged 49 years and above, last seen or heard from within the last 3 years).

RESULTS

A total of 59 valid questionnaires were analysed. At the time of the survey, 50 women were menopausal and 11 of them were using HRT, six for menopausal symptoms and five for osteoporosis prevention. Another 11 had used HRT, eight for menopausal symptoms and three for osteoporosis prevention, but had discontinued it. The main reasons for stopping HRT were side effects. Of the 28 women who had never been on HRT, 20 had either enquired about it, or had been offered HRT, but decided against it. Of the nine women who were still premenopausal at the time of the survey, four would consider using HRT.

CONCLUSIONS

Results show that 44% of the menopausal women in our sample have used HRT at some point and 22% still do, mostly for treatment of menopausal symptoms and for osteoporosis prevention. In view of the latest literature findings in able-bodied women, use of HRT for osteoporosis prevention in women with SCI may have to be reconsidered.