Calcitonin therapy in osteoporosis

[Austrian guidance for the pharmacological treatment of osteoporosis in postmenopausal women--update 2009]

Osteoporosis is a systemic skeletal disease characterized by diminished bone mass and deterioration of bone microarchitecture, leading to increased fragility and subsequent increased fracture risk. Therapeutic measures therefore aim at reducing individual fracture risk. In Austria, the following drugs, all of which have been proven to reduce fracture risk, are currently registered for the treatment of postmenopausal osteoporosis: alendronate, risedronate, etidronate, ibandronate, raloxifene, teriparatide (1-34 PTH), 1-84 PTH, strontium ranelate and salmon calcitonin. Fluorides are still available, but their role in daily practice has become negligible. Currently, there is no evidence that a combination of two or more of these drugs could improve anti-fracture potency. However, treatment with PTH should be followed by the treatment with an anticatabolic drug such as bisphosphonates. Calcium and vitamin D constitute an important adjunct to any osteoporosis treatment.

Construction of a recombinant eukaryotic expression plasmid containing human calcitonin gene and its expression in NIH3T3 cells

AIM

To construct a recombinant eukaryotic expression plasmid containing human calcitonin (hCT) gene and express the gene in murine fibroblast NIH3T3 cells.

MATERIALS AND METHODS

A murine Igkappa-chain leader sequence and hCT gene were synthesized and cloned into pCDNA3.0 to form the pCDNA3.0-Igkappa-hCT eukaryotic expression vector, which was transfected into NIH3T3 cells. The mRNA and protein expressions and secretion of hCT were detected. Primarily cultured osteoclasts were incubated with the supernatant of pCDNA3.0-Igk-hCT-transfected NIH3T3 cells, and their numbers were counted and morphology observed.

RESULTS

The expression and secretion of hCT were successfully detected in pCDNA3.0-Igk-hCT-transfected NIH3T3 cells. The number of osteoclasts was decreased and the cells became crumpled when they were incubated with the supernatant of pCDNA3.0-Igk-hCT-transfected NIH3T3 cells.

CONCLUSION

A recombinant eukaryotic expression vector containing hCT gene was successfully constructed and expressed in NIH3T3 cells. The secreted recombinant hCT inhibited the growth and morphology of osteoclasts.

A high throughput protein formulation platform: case study of salmon calcitonin

PURPOSE

The feasibility of using high throughput spectroscopy for characterization and selection of physically stable protein formulations was studied.

MATERIALS AND METHODS

A hundred aqueous formulations of salmon calcitonin (sCT) were prepared using 20 buffer compositions. The solutions had pH values between 2.5 and 10.5. The stability of the sCT formulations was analyzed over 1 week by the following assays: (1) protein concentration, (2) volume control by measuring pathlength, (3) turbidity (absorbance at 350 nm), (4) intrinsic tyrosine fluorescence, (5) 1-anilino-naphthalene-8-sulfonate (ANS) fluorescence, (6) Nile Red fluorescence. Addition of the dyes (Nile Red and ANS) was used to study protein conformational changes.

RESULTS

After 1 day, 27 out of the 100 formulations of salmon calcitonin were stable. After 7 days, 12 stable sCT formulations remained. The best salmon calcitonin formulation was in 10 mM sodium acetate buffer with pH values between 3.5 and 5.5.

CONCLUSIONS

The findings are in accordance with the sCT formulations that were patented and used commercially. This can be considered as a proof of concept for the high throughput protein formulation platform.

Pharmacokinetics and pharmacodynamics of exenatide following alternate routes of administration

Exenatide is a 39-amino acid peptide incretin mimetic approved for adjunctive treatment of type 2 diabetes. It shares several glucoregulatory activities with the mammalian hormone, glucagon-like peptide-1 (GLP-1). In clinical use, subcutaneous exenatide injections demonstrate glucoregulatory and weight loss effects with sustained plasma concentrations in the 50-100 pM range. We investigated the pharmacokinetics of exenatide in normoglycemic rats and biological activity in diabetic db/db mice after delivery to various epithelial surfaces of the intestinal and respiratory tracts. In rats, elimination kinetics were similar for all routes of administration (median k(e) 0.017 min(-1)). Bioavailability (versus intravenous administration) and C(max) per unit dose differed markedly. For gastrointestinal administration, sublingual administration invoked the highest bioavailability (0.37%); in db/db mice, potentially therapeutic concentrations were obtainable. In contrast, intraduodenal bioavailability was low (0.0053%). In regard to respiratory surfaces, bioavailability of intratracheal exenatide was up to 13.6%, and for nasal administration, 1.68%. Both routes of administration produced therapeutic plasma concentrations and glucose-lowering in db/db mice. At high doses, aerosolized exenatide also achieved effective concentrations and glucose-lowering. In summary, the intestinal tract seems to have limited potential as a route of exenatide administration, with sublingual being most promising. In contrast, the respiratory tract appears to be more viable, comparing favorably with the clinically approved subcutaneous route. Despite little optimization of the delivery formulation, exenatide bioavailability compared favorable to that of several commercially available bioactive peptides.

Intranasal delivery: physicochemical and therapeutic aspects

Interest in intranasal (IN) administration as a non-invasive route for drug delivery continues to grow rapidly. The nasal mucosa offers numerous benefits as a target issue for drug delivery, such as a large surface area for delivery, rapid drug onset, potential for central nervous system delivery, and no first-pass metabolism. A wide variety of therapeutic compounds can be delivered IN, including relatively large molecules such as peptides and proteins, particularly in the presence of permeation enhancers. The current review provides an in-depth discussion of therapeutic aspects of IN delivery including consideration of the intended indication, regimen, and patient population, as well as physicochemical properties of the drug itself. Case examples are provided to illustrate the utility of IN dosing. It is anticipated that the present review will prove useful for formulation scientists considering IN delivery as a delivery route.

Genome-wide linkage analysis to identify chromosomal regions affecting phenotypic traits in the chicken. III. Skeletal integrity

Two unique chicken F(2) populations generated from a broiler breeder male line and 2 genetically distinct inbred (>99%) chicken lines (Leghorn and Fayoumi) were used for whole genome QTL analysis. Twelve phenotypic skeletal integrity traits (6 absolute and 6 relative traits) were measured or calculated, including bone mineral content, bone mineral density, tibia length, shank length, shank weight, and shank length:shank weight. All traits were also expressed as a percentage of BW at 8 wk of age. Birds were genotyped for 269 microsatellite markers across the entire genome. The QTL affecting bone traits in chickens were detected by the QTL express program. Significance levels were obtained using the permutation test. For the 12 traits, a total of 56 significant QTL were detected at the 5% chromosome-wise significance level, of which 14 and 10 were significant at the 5% genome-wise level for the broiler-Leghorn cross and broiler-Fayoumi cross, respectively. Phenotypic variation for each trait explained by all detected QTL across the genome ranged from 12.0 to 35.6% in the broiler-Leghorn cross and 2.9 to 31.3% in the broiler-Fayoumi cross. Different QTL profiles identified between the 2 related F(2) crosses for most traits suggested that genetic background is an important factor for QTL analysis. Study of associations of biological candidate genes with skeletal integrity traits in chickens will reveal new knowledge of understanding biological process of skeletal homeostasis. The results of the current study have identified markers for bone strength traits, which may be used to genetically improve skeletal integrity in chickens by MAS, and to identify the causal genes for these traits.

The early stages of amyloid formation: biophysical and structural characterization of human calcitonin pre-fibrillar assemblies

Amyloid fibril formation is a nucleation dependent process characterized by a lag-phase prior to the appearance of detectable amyloid fibrils. While the three-dimensional structure of amyloid fibrils at atomic resolution is just beginning to be elucidated, the early process of monomers assembly into oligomers is less understood. Understanding the dynamic processes that lead to the formation of these intermediates is highly important as these assemblies might be the most pathological ones. Here, we investigated the biophysical and structural features characterizing the early stage assemblies formed by the human hormone calcitonin. We calculated the initial nucleus size by experimentally determining the dependence between the lag-time length and the hCT concentrations. We used size exclusion chromatography and dynamic light scattering in order to characterize the dynamic growth process of preliminary intermediates transformed into larger structures. The early structures were visualized using high-resolution transmission electron microscopy. Annular pore-like structures were observed along with protofibrilar structures. This observed morphology is similar to structures revealed during the fibrillization processes of beta-amyloid, alpha-synuclein, and islet amyloid polypeptide, suggesting that these intermediates represent a generic early structure conformation. The results introduced here imply that a variety of intermediate assemblies are formed during the early stages of amyloid fibril formation. The characterizing of their structural features and assembly kinetics will contribute to the rational design of inhibitors directed towards early structure assemblies.

Evaluation of the quantitative capability of a home-made cone-beam micro computed tomography system

Quantitative computed tomography provides the most accurate form of bone mineral density measurement. It is very useful in several applications when used with micro computed tomography (microCT). The objective of this study is to evaluate the quantitative capability of iterative and analytic reconstruction with and without energy-based beam hardening calibration using a home-made microCT. Due to the fact that the source of X-rays in the microCT is poly-energetic and the linear attenuation coefficient varies with the energy of the X-ray photons, a specific correction is presented in this study that resolves the poly-energetic effect. Then, a 3D distribution of the linear attenuation coefficient is reconstructed from the ordered subsets using the maximum likelihood and T-FDK algorithms. These algorithms were both developed for cone-beam microCT. The images reconstructed by the two algorithms with/without correction are presented. A region of interest analysis is used to evaluate the results from two algorithms and their advantages and disadvantages are discussed. The quantitative capability is better when the image is reconstructed using the iterative method along with a beam hardening correction.

Nanotechnology: intelligent design to treat complex disease

The purpose of this expert review is to discuss the impact of nanotechnology in the treatment of the major health threats including cancer, infections, metabolic diseases, autoimmune diseases, and inflammations. Indeed, during the past 30 years, the explosive growth of nanotechnology has burst into challenging innovations in pharmacology, the main input being the ability to perform temporal and spatial site-specific delivery. This has led to some marketed compounds through the last decade. Although the introduction of nanotechnology obviously permitted to step over numerous milestones toward the development of the "magic bullet" proposed a century ago by the immunologist Paul Ehrlich, there are, however, unresolved delivery problems to be still addressed. These scientific and technological locks are discussed along this review together with an analysis of the current situation concerning the industrial development.

Rehabilitation of the Older Adult with an Osteoporosis-Related Fracture

Osteoporosis is the most common metabolic bone disease and is clinically silent until it manifests in the form of fracture. When this occurs, significant deformity and disability can result. Appropriate rehabilitation of fracture includes antiosteoporotic medication; exercise programs; fall prevention; orthoses, such as bracing and hip protectors; and the minimally invasive procedures vertebroplasty and kyphoplasty.