Calcitonin: a drug of the past or for the future? Physiologic inhibition of bone resorption while sustaining osteoclast numbers improves bone quality

Association of the calcitonin gene (CA) polymorphism with osteoarthritis of the knee in a Mexican mestizo population

Osteoarthritis (OA) is the most common form of destructive joint disease that is characterized by the degeneration of the articular cartilage, synovial membrane, joint capsule, and subchondral bone. The knee is a joint commonly affected for OA. Calcitonin (CT) has been suggested to have chondroprotective effects; therefore, could play a role in the pathogenesis of OA of the knee. Genetic variations in or adjacent to the CT gene may be associated with primary OA development. We conducted a case-control association study in which we examined the correlation between a dinucleotide (cytosine-adenine, CA) repeat polymorphism at the CT locus and OA of the knee in 88 patients with OA and in 111 control subjects from the Mexican mestizo population. Allele A and genotype AG frequencies were significantly higher in patients with OA than in control subjects (56.3 vs. 43.2%; p<0.001 and 40.9 vs. 26.1%; p=0.027, respectively), and were associated with the presence of OA of the knee (odds ratio [OR], 2.62; 95% confidence interval [95% CI], 1.30-5.27, and OR, 1.93; 95% CI, 1.04-3.58, respectively) using a logistic regression model adjusted for gender, age and Body mass index (BMI). The GG genotype was associated with a lower risk of OA development of the knee; thus, it may constitute a protective factor against this disease (OR, 0.40; 95% CI, 0.16-0.98). In summary, we conclude that the dinucleotide CA polymorphism in the CT gene may become a useful marker for genetic studies of OA of the knee in Mexican population.

The effect of oral salmon calcitonin delivered with 5-CNAC on bone and cartilage degradation in osteoarthritic patients: a 14-day randomized study

BACKGROUND

The aim of this study was to investigate the pharmacokinetic and pharmacodynamic parameters of oral salmon calcitonin (oSCT) administered over 14 days to men and women presenting with osteoarthritis (OA).

MATERIALS AND METHODS

The study was a phase-I, 2-week, placebo-controlled, double-blind, double-dummy, randomized, gender-stratified study including 73 subjects aged 57-75 years. Patients had painful OA with a Kellgren and Lawrence index score of I-III. Treatment allocations were; 0.6 mg, 0.8 mg of oSCT, or placebo. Treatment was given twice daily for 14 days. The morning dose was administered between 07:00 and 08:00 at least 30 min before breakfast. The second dose was administered 30 min before evening dinner. On treatment day 1 and 14, the morning dose was followed by 5h of fasting, and blood samples and urine were collected immediately prior to dosing and according to the protocol. Study parameters were: plasma sCT levels, bone resorption by CTX-I (serum C-terminal telopeptide of collagen type I), bone formation by osteocalcin (serum OC), and cartilage degradation by CTX-II (urine C-terminal telopeptide of collagen type II) (clinicaltrials.gov identifier: NCT00486369).

RESULTS

Doses of 0.8 mg compared with 0.6 mg produced significantly higher C(max) and AUC(0-4 hrs), of calcitonin, P=0.03. This resulted in significant reductions in CTX-I and CTX-II, [P<0.0001; P=0.007]. No differences were observed between baseline and follow-up at day 14 in pharmacokinetic and pharmacodynamic parameters. Gender had no observable influence on results.

CONCLUSIONS

oSCT given twice daily with a pre-dinner and morning fasting dosing resulted in reductions in markers of bone resorption and cartilage degradation.

Characterization and management of hypercalcemia following transplantation for osteopetrosis

Autosomal recessive osteopetrosis (OP) is characterized by insufficient osteoclast activity resulting in defective bone resorption and marked increase in skeletal mass and density. OP has been successfully treated with hematopoietic cell transplantation (HCT), secondary to engraftment of donor-derived functioning osteoclasts resulting in remodeling of bone and establishment of normal hematopoiesis. Although hypercalcemia is a common presenting feature of OP, it may be observed following HCT due to engraftment of osteoclasts differentiated from the hematopoietic precursors. To characterize hypercalcemia after HCT-who is at risk, onset, duration and response to treatment-we evaluated 15 patients with OP treated at the University of Minnesota from 2000 to 2009. Hypercalcemia, defined as any single calcium >11.0 mg/100 ml after the first transplant, was found in 40% of patients. Median onset of hypercalcemia was 23 days and the duration was 2-24 days. Hypercalcemia was more common in patients older than 2 years of age at the time of HCT. Treatment with hydration, furosemide and s.c. calcitonin resolved hypercalcemia and resulted in no severe adverse events. In conclusion, hypercalcemia is common in patients with OP within the first 4 weeks after HCT, and more likely in older patients. Isotonic saline, furosemide and s.c. calcitonin were well-tolerated and effective treatments in our study population.

Is bone quality associated with collagen age?

The World Health Organization defines osteoporosis as a systemic disease characterized by decreased bone tissue mass and microarchitectural deterioration, resulting in increased fracture risk. Since this statement, a significant amount of data has been generated showing that these two factors do not cover all risks for fracture. Other independent clinical factors, such as age, as well as aspects related to qualitative changes in bone tissue, are believed to play an important role. The term "bone quality" encompasses a variety of parameters, including the extent of mineralization, the number and distribution of microfractures, the extent of osteocyte apoptosis, and changes in collagen properties. The major mechanism controlling these qualitative factors is bone remodeling, which is tightly regulated by the osteoclast/osteoblast activity. We focus on the relationship between bone remodeling and changes in collagen properties, especially the extent of one posttranslational modification. In vivo, measurements of the ratio between native and isomerized C-telopeptides of type I collagen provides an index of bone matrix age. Current preclinical and clinical studies suggests that this urinary ratio provides information about bone strength and fracture risk independent of bone mineral density and that it responds differently according to the type of therapy regulating bone turnover.

Conjugation of salmon calcitonin to a combed-shaped end functionalized poly(poly(ethylene glycol) methyl ether methacrylate) yields a bioactive stable conjugate

Salmon calcitonin (sCT) was conjugated via its N-terminal cysteine to a comb-shaped end-functionalized poly(poly(ethylene glycol) methyl ether methacrylate) (PolyPEG, 6.5 kDa), and to linear PEG (5 kDa). Conjugate molecular weight and purity was assessed by SEC-HPLC and MALDI-TOF MS. Bioactivity of conjugates was measured by cyclic AMP assay in T47D cells. Calcium and calcitonin levels were measured in rats following intravenous injections. Stability of conjugates was tested against serine proteases, intestinal and liver homogenates and serum. Cytotoxicity of conjugates was assessed by lactate dehydrogenase (LDH) assay and by haemolytic assay of rat red blood cells. Results showed that the two conjugates were of high purity with molecular weights similar to predictions. Both conjugates retained more than 85% bioactivity in vitro and had nanomolar EC(50) values similar to sCT. While both sCT-PolyPEG(6.5 K) and sCT-PEG(5 K) were resistant to metabolism by serine proteases, homogenates and serum, PolyPEG (6.5 K) was more so. Although both conjugates reduced serum calcium to levels similar to those achieved with sCT, PolyPEG(6.5 K) extended the T(1/2) and AUC of serum sCT over values achieved with sCT-PEG and sCT itself. None of PolyPEG, PEG or methacrylic acid displayed significant cytotoxicity. PolyPEG may therefore have potential to improve pharmacokinetic profiles of injected peptides.

An immunohistochemical study of the antinociceptive effect of calcitonin in ovariectomized rats

BACKGROUND

Calcitonin is used as a treatment to reduce the blood calcium concentration in hypercalcemia and to improve bone mass in osteoporosis. An analgesic effect of calcitonin has been observed and reported in clinical situations. Ovariectomized (OVX) rats exhibit the same hormonal changes as observed in humans with osteoporosis and are an animal model of postmenopausal osteoporosis. The aim of this study to investigate antinociceptive effect of calcitonin in OVX rats using the immunohistochemical study.

METHODS

We assessed the antinociceptive effects of calcitonin in an ovariectomized (OVX) rat model, which exhibit osteoporosis and hyperalgesia, using the immunohistochemical method. Fifteen rats were ovariectomized bilaterally, and ten rats were received the same surgery expected for ovariectomy as a sham model. We used five groups: the OVX-CT (n = 5), the sham-CT (n = 5), and the OVX-CT-pcpa (n = 5) groups received calcitonin (CT: 4 U/kg/day), while OVX-vehi (n = 5) and the sham-vehi (n = 5) groups received vehicle subcutaneously 5 times a week for 4 weeks. The OVX-CT-pcpa-group was given traperitoneal injection of p-chlorophenylalanine (pcpa; an inhibitor of serotonin biosynthesis) (100 mg/kg/day) in the last 3 days of calcitonin injection. Two hours after 5% formalin (0.05 ml) subcutaneously into the hind paw, the L5 spinal cord were removed and the number of Fos-immunoreactive (ir) neurons were evaluated using the Mann-Whitney-U test.

RESULTS

The numbers of Fos-ir neurons in the OVX-CT and sham-CT groups were significantly less than in the OVX-vehi and sham-vehi groups, respectively (p = 0.0090, p = 0.0090). The number of Fos-ir neurons in the OVX-CT-pcpa-group was significantly more than that of the OVX-CT-group (p = 0.0283), which means pcpa inhibits calcitonin induced reduction of c-Fos production.

CONCLUSION

The results in this study demonstrated that 1) the increase of c-Fos might be related to hyperalgesia in OVX-rats. 2) Calcitonin has an antinociceptive effect in both OVX and sham rats. 3) The central serotonergic system is involved in the antinociceptive properties of calcitonin.

Anti-resorptives in the management of osteoporosis

Bone-active agents that decrease bone turnover (the anti-resorptive agents) have been, to date, the most thoroughly studied pharmacological agents for the management of osteoporosis in a variety of populations - postmenopausal, male, and glucocorticoid-induced osteoporosis - and have received both Food and Drug Administration (FDA) and Committee for Medicinal Products for Human Use (CHMP) as well as other worldwide registrations for the management of these conditions. While the mechanisms of action of 'anti-resorptives' as a class differ, their effect on increasing bone strength and reducing the risk of fragility fractures share common pathways: an increase in bone mineral content, and a reduction in bone turnover. Within the category of anti-resorptives: estrogen, selective estrogen receptor modulators, tibolone, calcitonin, bisphosphonates and denosumab all reduce vertebral fractures risk, but differ in their ability to reduce the risk of non-vertebral fractures in randomized clinical trials. This chapter will discuss the data on these effects for each class of anti-resorptive agent.