Recombinant human parathyroid hormone

Potentials of Neuropeptides as Therapeutic Agents for Neurological Diseases

Despite recent leaps in modern medicine, progress in the treatment of neurological diseases remains slow. The near impermeable blood-brain barrier (BBB) that prevents the entry of therapeutics into the brain, and the complexity of neurological processes, limits the specificity of potential therapeutics. Moreover, a lack of etiological understanding and the irreversible nature of neurological conditions have resulted in low tolerability and high failure rates towards existing small molecule-based treatments. Neuropeptides, which are small proteinaceous molecules produced by the body, either in the nervous system or the peripheral organs, modulate neurological function. Although peptide-based therapeutics originated from the treatment of metabolic diseases in the 1920s, the adoption and development of peptide drugs for neurological conditions are relatively recent. In this review, we examine the natural roles of neuropeptides in the modulation of neurological function and the development of neurological disorders. Furthermore, we highlight the potential of these proteinaceous molecules in filling gaps in current therapeutics.

Engraftment and bone mass are enhanced by PTHrP 1-34 in ectopically transplanted vertebrae (vossicle model) and can be non-invasively monitored with bioluminescence and fluorescence imaging

Evidence exists that parathyroid hormone-related protein (PTHrP) 1-34 may be more anabolic in bone than parathyroid hormone 1-34. While optical imaging is growing in popularity, scant information exists on the relationships between traditional bone imaging and histology and bioluminescence (BLI) and fluorescence (FLI) imaging. We aimed to evaluate the effects of PTHrP 1-34 on bone mass and determine if relationships existed between radiographic and histologic findings in bone and BLI and FLI indices. Vertebrae (vossicles) from mice coexpressing luciferase and green fluorescent protein were implanted subcutaneously into allogenic nude mice. Transplant recipients were treated daily with saline or PTHrP 1-34 for 4 weeks. BLI, FLI, radiography, histology, and µCT of the vossicles were performed over time. PTHrP 1-34 increased bioluminescence the most after 2 weeks, fluorescence at all time points, and decreased the time to peak bioluminescence at 4 weeks (P ≤ 0.027), the latter of which suggesting enhanced engraftment. PTHrP 1-34 maximized vertebral body volume at 4 weeks (P < 0.0001). The total amount of bone observed histologically increased in both groups at 2 and 4 weeks (P ≤ 0.002); however, PTHrP 1-34 exceeded time-matched controls (P ≤ 0.044). A positive linear relationship existed between the percentage of trabecular bone and (1) total bioluminescence (r = 0.595; P = 0.019); (2) total fluorescence (r = 0.474; P = 0.074); and (3) max fluorescence (r = 0.587; P = 0.021). In conclusion, PTHrP 1-34 enhances engraftment and bone mass, which can be monitored non-invasively by BLI and FLI.

Sost down-regulation by mechanical strain in human osteoblastic cells involves PGE2 signaling via EP4

Sclerostin is a potent inhibitor of bone formation which is down-regulated by mechanical loading. To investigate the mechanisms involved we subjected Saos2 human osteoblastic cells to short periods of dynamic strain and used quantitative reverse transcriptase polymerase chain reaction to compare their responses to unstrained controls. Strain-induced Sost down-regulation was recapitulated by cyclo-oxygenase-2-mediated PGE2, acting through the EP4 receptor, whereas strain-related up-regulation of osteocalcin was mediated by the EP2 receptor. Strain-related Sost regulation required extracellular signal-regulated kinase signaling, whereas osteocalcin required protein kinase C. These findings indicate early divergence in the signaling pathways stimulated by strain and establish PGE2/EP4 as the pathway used by strain to regulate Sost expression.

Antifracture efficacy of currently available therapies for postmenopausal osteoporosis

Osteoporosis is a systemic bone disease characterized by low bone mass and bone mineral density, and deterioration of the underlying structure of bone tissue. These changes lead to an increase in bone fragility and an increased risk for fracture, which are the clinical consequences of osteoporosis. The classical triad for consideration in osteoporosis is morbidity, mortality and cost. Vertebral fracture is an important source of morbidity in terms of pain and spinal deformity. On the other hand, hip fracture is associated with the worst outcomes and is widely regarded as a life-threatening event in the elderly; it is the source of the bulk of the cost of the disease in contemporary healthcare. The prevention of osteoporosis-associated fracture should include fall prevention, calcium supplementation and lifestyle advice, as well as pharmacological therapy using agents with proven antifracture efficacy. The most commonly used osteoporosis treatments in Europe are the bisphosphonates alendronate, risedronate, ibandronate and zoledronic acid; the selective estrogen receptor modulator (SERM) raloxifene; teriparatide; and strontium ranelate. Recent additions include the biological therapy denosumab and the SERM bazedoxifene. In this review, we explore the antifracture efficacy of these agents with the aim of simplifying treatment decisions. These treatments can be broadly divided according to their mode of action. The antiresorptive agents include the bisphosphonates, the SERMs and denosumab, while the bone-forming agents include parathyroid hormone and teriparatide. Strontium ranelate appears to combine both antiresorptive and anabolic activities. We collated data on vertebral and hip fracture efficacy from the pivotal 3-year phase III trials, all of which had a randomized, double-blind, placebo-controlled design. The relative reductions in risk in the osteoporosis trials range from 30% to 70% for vertebral fracture and 30% to 51% for hip fracture. This translates into 3-year number needed to treat values of between 9 and 21 for vertebral fracture and from 48 upwards for hip fracture. International guidelines agree that agents that have been shown to decrease vertebral, nonvertebral and hip fractures should be used preferentially over agents that only demonstrate vertebral antifracture efficacy. This is the case for alendronate, risedronate, zoledronic acid, denosumab and strontium ranelate. Finally, therapeutic decisions should be based on a balance between benefits and risks of treatment, which must be carefully considered in each particular case both by the physician and the patient. Indeed, no single agent is appropriate for all patients and, therefore, treatment decisions should be made on an individual basis, taking into account all measures of treatment effect and risk before making informed judgments about the best individual treatment option.

Profile of teriparatide in the management of postmenopausal osteoporosis

One out of every 2 women within postmenopause are at risk of fracture due to osteoporosis. Fortunately, a growing arsenal of therapies is becoming available to treat this disease and prevent fracture. A new class of anabolic agents has emerged within the last decade that brought with it a new concept in osteoporosis therapy: building new stronger bone rather than simply inhibiting bone turnover. Evidence is accumulating to understand how to best utilize these new agents, and which patients benefit most. This article will review the effectiveness, risks, timing and clinical uses of teriparatide in postmenopausal osteoporosis.

Mechanical loading enhances the anabolic effects of intermittent parathyroid hormone (1-34) on trabecular and cortical bone in mice

The separate and combined effects of intermittent parathyroid hormone (iPTH) (1-34) and mechanical loading were assessed at trabecular and cortical sites of mouse long bones. Female C57BL/6 mice from 13 to 19 weeks of age were given daily injections of vehicle or PTH (1-34) at low (20 microg/kg/day), medium (40 microg/kg/day) or high (80 microg/kg/day) dose. For three alternate days per week during the last two weeks of this treatment, the tibiae and ulnae on one side were subjected to a single period of non-invasive, dynamic axial loading (40 cycles at 10 Hz with 10-second intervals between each cycle). Two levels of peak load were used; one sufficient to engender an osteogenic response, and the other insufficient to do so. The whole tibiae and ulnae were analyzed post-mortem by micro-computed tomography with a resolution of 5 microm. Treatment with iPTH (1-34) modified bone structure in a dose- and time-dependent manner, which was particularly evident in the trabecular region of the proximal tibia. In the tibia, loading at a level sufficient by itself to stimulate osteogenesis produced an osteogenic response in the low-dose iPTH (1-34)-treated trabecular bone and in the proximal and middle cortical bone treated with all doses of iPTH (1-34). In the ulna, loading at a level that did not by itself stimulate osteogenesis was osteogenic at the distal site when combined with high-dose iPTH (1-34). At both levels of loading, there were synergistic effects in cortical bone volume of the proximal tibia and distal ulna between loading and high-dose iPTH (1-34). Images of fluorescently labelled bones confirmed that such synergism resulted from increases in both endosteal and periosteal bone formation. No woven bone was induced by iPTH (1-34) or either level of loading alone, whereas the combination of iPTH (1-34) and the "sufficient" level of loading stimulated woven bone formation on endosteal and periosteal surfaces of the proximal cortex in the tibiae. Together, these data suggest that in female C57BL/6 mice, under some but not all circumstances, mechanical loading exerts an osteogenic response with iPTH (1-34) in trabecular and cortical bone.

Protein therapeutics: a summary and pharmacological classification

Once a rarely used subset of medical treatments, protein therapeutics have increased dramatically in number and frequency of use since the introduction of the first recombinant protein therapeutic--human insulin--25 years ago. Protein therapeutics already have a significant role in almost every field of medicine, but this role is still only in its infancy. This article overviews some of the key characteristics of protein therapeutics, summarizes the more than 130 protein therapeutics used currently and suggests a new classification of these proteins according to their pharmacological action.

Sequential treatment with intermittent low-dose human parathyroid hormone (1-34) and bisphosphonate enhances large-size skeletal reconstruction by vascularized bone transplantation

Vascularized bone transplantation enables reconstruction of large skeletal defects, but this process needs a long time. Since short-term intermittent parathyroid hormone (PTH) enhances rat fracture healing, we investigated the effects of 4-week intermittent low-dose (10 microg/kg/day) or high-dose (100 microg/kg/day) PTH followed by 4-week vehicle, low-dose or high-dose intermittent PTH, or zoledronic acid (ZOL, 2 micro/kg/week), a potent bisphosphonate, on large skeletal reconstruction by vascularized tibial grafting in rats. Compared to 8-week vehicle, 8-week low-dose PTH did not significantly increase the serum osteocalcin level as well as the urinary deoxypyridinoline level, while 4-week low-dose or high-dose PTH followed by 4-week ZOL decreased both of these levels. Eight-week PTH increased the bone mass of the graft and strength of the reconstructed skeleton in a dose-dependent manner; notably, the reconstructed skeleton showed an obviously higher response to PTH compared to the contralateral nonoperated femur. In contrast, 4-week PTH followed by 4-week vehicle reduced these effects and caused local bone loss at the host-graft junctions. Four-week PTH followed by 4-week ZOL did not induce such bone loss; however, 4-week high-dose PTH followed by 4-week ZOL caused a large callus in the distal cortical junction. Four-week PTH followed by 4-week ZOL increased the bone mass and strength similarly to 8-week PTH. These preliminary findings suggest, for the first time, that sequential treatment with short-term intermittent low-dose PTH and bisphosphonate as well as long-term intermittent low-dose PTH treatment enhance large skeletal reconstruction by vascularized bone transplantation, though early timing of sequential antiresorptive treatment could result in delay of bone repair.

Métabolisme minéral osseux: données récentes et perspectives relatives à l’ostéogenèse

Important data have recently been added to our knowledge of bone mineral metabolism in children. Molecular pathophysiology of several pediatric syndromes has been clarified. Specially, the components of endocrine and metabolic regulations are tightly related with regard to the trophicity of bone. On another hand, the impact of several therapeutics of bone diseases like biphosphonates, parathormone (PTH) or growth hormone on bone anabolism is now strongly emphasized. All these points are important for the becoming of bone pediatric diseases in the adult life. Here we analyze the essential components of mineral metabolism and of its regulation in view of the recent biological data, like PTH/PTHrP (PTH-related peptide)-evoked cell signaling, the role of FGF 23 (Fibroblast growth factor 23) in hypophosphatemia and the regulation of vitamin D metabolism by 1alpha-hydroxylase. Inter-relation of these regulating elements is present in several genetic diseases and in the Mc Cune Albright syndrome. Relationships between metabolic and endocrine factors are analyzed considering their impact on PTH secretion and osteogenesis.

Osteosarcoma associated with hyperparathyroidism

The fourth case in the literature is presented of a patient with the rare association of hyperparathyroidism and osteosarcoma. A 56-year-old woman presented with hyperparathyroidism and a lesion in the tibia. Initial diagnosis was brown tumor. Histology, however, revealed osteosarcoma, and the patient was treated accordingly. The experimental induction of osteosarcoma by parathormone in rodent studies makes this finding alarming, considering the increasing use of parathormone in the treatment of osteoporosis. The mechanism by which osteosarcoma is induced in humans cannot be explained based on current knowledge of mechanisms of action of parathyroid hormone.

Targeted deletion of histidine decarboxylase gene in mice increases bone formation and protects against ovariectomy-induced bone loss

Targeted disruption of the histidine decarboxylase gene (HDC(-/-)), the only histamine-synthesizing enzyme, led to a histamine-deficient mice characterized by undetectable tissue histamine levels, impaired gastric acid secretion, impaired passive cutaneous anaphylaxis, and decreased mast cell degranulation. We used this model to study the role of histamine in bone physiology. Compared with WT mice, HDC(-/-) mice receiving a histamine-free diet had increased bone mineral density, increased cortical bone thickness, higher rate of bone formation, and a marked decrease in osteoclasts. After ovariectomy, cortical and trabecular bone loss was reduced by 50% in HDC(-/-) mice compared with WT. Histamine deficiency protected the skeleton from osteoporosis directly, by inhibiting osteoclastogenesis, and indirectly, by increasing calcitriol synthesis. Quantitative RT-PCR showed elevated 25-hydroxyvitamin D-1alpha-hydroxylase and markedly decreased 25-hydroxyvitamin D-24-hydroxylase mRNA levels. Serum parameters confirming this indirect effect included elevated calcitriol, phosphorus, alkaline phosphatase, and receptor activator of NF-kappaB ligand concentrations, and suppressed parathyroid hormone concentrations in HDC(-/-) mice compared with WT mice. After ovariectomy, histamine-deficient mice were protected from bone loss by the combination of increased bone formation and reduced bone resorption.