Salmon calcitonin: a review of current and future therapeutic indications

Tuning the double lipidation of salmon calcitonin to introduce a pore-like membrane translocation mechanism

A widespread strategy to increase the transport of therapeutic peptides across cellular membranes has been to attach lipid moieties to the peptide backbone (lipidation) to enhance their intrinsic membrane interaction. Efforts in vitro and in vivo investigating the correlation between lipidation characteristics and peptide membrane translocation efficiency have traditionally relied on end-point read-out assays and trial-and-error-based optimization strategies. Consequently, the molecular details of how therapeutic peptide lipidation affects it's membrane permeation and translocation mechanisms remain unresolved. Here we employed salmon calcitonin as a model therapeutic peptide and synthesized nine double lipidated analogs with varying lipid chain lengths. We used single giant unilamellar vesicle (GUV) calcein influx time-lapse fluorescence microscopy to determine how tuning the lipidation length can lead to an All-or-None GUV filling mechanism, indicative of a peptide mediated pore formation. Finally, we used a GUVs-containing-inner-GUVs assay to demonstrate that only peptide analogs capable of inducing pore formation show efficient membrane translocation. Our data provided the first mechanistic details on how therapeutic peptide lipidation affects their membrane perturbation mechanism and demonstrated that fine-tuning lipidation parameters could induce an intrinsic pore-forming capability. These insights and the microscopy based workflow introduced for investigating structure-function relations could be pivotal for optimizing future peptide design strategies.

Molecular Insights into the Effects of F16L and F19L Substitutions on the Conformation and Aggregation Dynamics of Human Calcitonin

Human calcitonin (hCT) regulates calcium-phosphorus metabolism, but its amyloid aggregation disrupts physiological activity, increases thyroid carcinoma risk, and hampers its clinical use for bone-related diseases like osteoporosis and Paget's disease. Improving hCT with targeted modifications to mitigate amyloid formation while maintaining its function holds promise as a strategy. Understanding how each residue in hCT's amyloidogenic core affects its structure and aggregation dynamics is crucial for designing effective analogues. Mutants F16L-hCT and F19L-hCT, where Phe residues in the core are replaced with Leu as in nonamyloidogenic salmon calcitonin, showed different aggregation kinetics. However, the molecular effects of these substitutions in hCT are still unclear. Here, we systematically investigated the folding and self-assembly conformational dynamics of hCT, F16L-hCT, and F19L-hCT through multiple long-time scale independent atomistic discrete molecular dynamics (DMD) simulations. Our results indicated that the hCT monomer primarily assumed unstructured conformations with dynamic helices around residues 4-12 and 14-21. During self-assembly, the amyloidogenic core of hCT14-21 converted from dynamic helices to β-sheets. However, substituting F16L did not induce significant conformational changes, as F16L-hCT exhibited characteristics similar to those of wild-type hCT in both monomeric and oligomeric states. In contrast, F19L-hCT exhibited substantially more helices and fewer β-sheets than did hCT, irrespective of their monomers or oligomers. The substitution of F19L significantly enhanced the stability of the helical conformation for hCT14-21, thereby suppressing the helix-to-β-sheet conformational conversion. Overall, our findings elucidate the molecular mechanisms underlying hCT aggregation and the effects of F16L and F19L substitutions on the conformational dynamics of hCT, highlighting the critical role of F19 as an important target in the design of amyloid-resistant hCT analogs for future clinical applications.

Triple-Hybrid BioScaffold Based on Silk Fibroin, Chitosan, and nano-Biphasic Calcium Phosphates: Preparation, Characterization of Physiochemical and Biopharmaceutical Properties

Bioscaffolds, which promote cell regeneration and restore tissues' functions, have emerged as significant need in clinic. The hybrid of several biomaterials in a bioscaffold renders clinically advanced and relevant properties for applications yet add challenges in cost efficiency, production, and clinical investigation. This study proposes a facile and sustainable method to formulate a triple-hybrid bioscaffold based on Vietnamese cocoon origin Silk Fibroin, Chitosan, and nano-Biphasic Calcium Phosphates (nano-BCP) that can be easily molded, has high porosity (55-80%), and swelling capacity that facilitates cell proliferation and nutrient diffusion. Notably, their mechanical properties, in particular compressive strength, can easily be tuned in a range from 50 - 200 kPa by changing the amount of nano-BCP addition, which is comparable to the successful precedents for productive cell regeneration. The latter parts investigate the biopharmaceutical properties of a representative bioscaffold, including drug loading and release studies with two kinds of active compounds, salmon calcitonin and methylprednisolone. Furthermore, the bioscaffold is highly biocompatible as the results of hemocompatibility and hemostasis tests, as well as ovo chick chorioallantoic membrane investigation. The findings of the study suggest the triple-hybrid scaffold as a promising platform for multi-functional drug delivery and bone defect repair.

Metabolic bone disorders and the promise of marine osteoactive compounds

Metabolic bone disorders and associated fragility fractures are major causes of disability and mortality worldwide and place an important financial burden on the global health systems. These disorders result from an unbalance between bone anabolic and resorptive processes and are characterized by different pathophysiological mechanisms. Drugs are available to treat bone metabolic pathologies, but they are either poorly effective or associated with undesired side effects that limit their use. The molecular mechanism underlying the most common metabolic bone disorders, and the availability, efficacy, and limitations of therapeutic options currently available are discussed here. A source for the unmet need of novel drugs to treat metabolic bone disorders is marine organisms, which produce natural osteoactive compounds of high pharmaceutical potential. In this review, we have inventoried the marine osteoactive compounds (MOCs) currently identified and spotted the groups of marine organisms with potential for MOC production. Finally, we briefly examine the availability of in vivo screening and validation tools for the study of MOCs.

A novel endomorphin-2/salmon calcitonin hybrid peptide with enhancing anti-allodynic and anti-anxiety effects

Pain, a worldwide problem with a high incidence and complex pathogenesis, has attracted the attention of pharmaceutical enterprises for the development of safer and more effective drugs. Extensive experimental and clinical evidence has demonstrated the analgesic effects of two endogenous peptides: endomorphin-2 (EM-2) and salmon calcitonin (sCT). However, EM-2 has limitations, such as poor ability to cross the blood-brain barrier (BBB) and little therapeutic effect in chronic pain due to rapid in vivo proteolysis. Herein, we propose the design of a novel hybrid peptide TEM2CT by combining EM-2, sCT16-21, and the cell-penetrating peptide HIV-1 trans-activator protein (TAT) with the aim of enhancing their analgesic effects. TEM2CT treatment attenuated nociceptive behavior in both acute and chronic pain mouse models, exhibiting increased anti-allodynic and anti-anxiety effects compared to sCT treatment. Furthermore, TEM2CT also regulated the excitability of pyramidal neurons in the anterior cingulate cortex (ACC) in spared nerve injury (SNI) model mice. The improved efficacy of this hybrid peptide provides a promising strategy for developing analgesic drugs.

Role of Calcitonin and Strontium Ranelate in Osteoporosis

Background

Both Strontium Ranelate (SR) and Calcitonin (CT) can be used to treat osteoporosis. Calcitonin was actually one of the very initial medicines used to treat osteoporosis, especially in postmenopausal cases. However, the fracture prevention effect of Calcitonin is only proven to be in vertebrae and that too with nasal route only. When comparing Calcitonin with other conventional medications in treating osteoporosis, Calcitonin has got no additional advantages. Strontium Ranelate has got double effect, i.e., less bone resorption and more bone formation. Therefore, it can lead to an increase in bone mass significantly. Strontium Ranelate has been proven to decrease the risk of non-vertebral fractures as well as vertebral fractures.

Conclusion

Both Calcitonin and Strontium Ranelate are used only as a second-line therapy for the treatment of osteoporosis and not as first-line therapy, mainly because of their safety concern and also because they do not provide any advantages compared to other therapy for the treatment of osteoporosis.

Future targets for migraine treatment beyond CGRP

BACKGROUND

Migraine is a disabling and chronic neurovascular headache disorder. Trigeminal vascular activation and release of calcitonin gene-related peptide (CGRP) play a pivotal role in the pathogenesis of migraine. This knowledge has led to the development of CGRP(-receptor) therapies. Yet, a substantial proportion of patients do not respond to these treatments. Therefore, alternative targets for future therapies are warranted. The current narrative review provides a comprehensive overview of the pathophysiological role of these possible non-CGRP targets in migraine.

FINDINGS

We covered targets of the metabotropic receptors (pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP), amylin, and adrenomedullin), intracellular targets (nitric oxide (NO), phosphodiesterase-3 (PDE3) and -5 (PDE5)), and ion channels (potassium, calcium, transient receptor potential (TRP), and acid-sensing ion channels (ASIC)). The majority of non-CGRP targets were able to induce migraine-like attacks, except for (i) calcium channels, as it is not yet possible to directly target channels to elucidate their precise involvement in migraine; (ii) TRP channels, activation of which can induce non-migraine headache; and (iii) ASICs, as their potential in inducing migraine attacks has not been investigated thus far. Drugs that target its receptors exist for PACAP, NO, and the potassium, TRP, and ASIC channels. No selective drugs exist for the other targets, however, some existing (migraine) treatments appear to indirectly antagonize responses to amylin, adrenomedullin, and calcium channels. Drugs against PACAP, NO, potassium channels, TRP channels, and only a PAC₁ antibody have been tested for migraine treatment, albeit with ambiguous results.

CONCLUSION

While current research on these non-CGRP drug targets has not yet led to the development of efficacious therapies, human provocation studies using these targets have provided valuable insight into underlying mechanisms of migraine headaches and auras. Further studies are needed on these alternative therapies in non-responders of CGRP(-receptor) targeted therapies with the ultimate aim to pave the way towards a headache-free future for all migraine patients.

Managing Early Onset Osteoporosis: The Impact of Premature Ovarian Insufficiency on Bone Health

Premature ovarian insufficiency is a reproductive endocrine disorder characterized by the cessation of ovarian function before the age of 40 years. Although the etiopathology of POI remains largely unknown, certain causative factors have been identified. Individuals affected by POI are at an increased risk of experiencing bone mineral density (BMD) loss. Hormonal replacement therapy (HRT) is recommended for patients with POI to mitigate the risk of decreased BMD, starting from the time of diagnosis until reaching the average age of natural menopause. Various studies have compared the dose-effect relationship of estradiol supplementation, as well as different HRT formulations on BMD. The impact of oral contraception on reduced BMD or the potential benefits of adding testosterone to estrogen replacement therapy are still subjects of ongoing discussion. This review provides an overview of the latest advancements in the diagnosis, evaluation, and treatment of POI as it relates to BMD loss.

Role of nanotechnology in the prolonged release of drugs by the subcutaneous route

INTRODUCTION

Subcutaneous physiology is distinct from other parenteral routes that benefit the administration of prolonged-release formulations. A prolonged-release effect is particularly convenient for treating chronic diseases because it is associated with complex and often prolonged posologies. Therefore, drug-delivery systems focused on nanotechnology are proposed as alternatives that can overcome the limitations of current therapeutic regimens and improve therapeutic efficacy.

AREAS COVERED

This review presents an updated systematization of nanosystems, focusing on their applications in highly prevalent chronic diseases. Subcutaneous-delivered nanosystem-based therapies comprehensively summarize nanosystems, drugs, and diseases and their advantages, limitations, and strategies to increase their translation into clinical applications. An outline of the potential contribution of quality-by-design (QbD) and artificial intelligence (AI) to the pharmaceutical development of nanosystems is presented.

EXPERT OPINION

Although recent academic research and development (R&D) advances in the subcutaneous delivery of nanosystems have exhibited promising results, pharmaceutical industries and regulatory agencies need to catch up. The lack of standardized methodologies for analyzing in vitro data from nanosystems for subcutaneous administration and subsequent in vivo correlation limits their access to clinical trials. There is an urgent need for regulatory agencies to develop methods that faithfully mimic subcutaneous administration and specific guidelines for evaluating nanosystems.

Expression of the Calcitonin Receptor-like Receptor (CALCRL) in Normal and Neoplastic Tissues

Little information is available concerning protein expression of the calcitonin receptor-like receptor (CALCRL) at the protein level. Here, we developed a rabbit monoclonal antibody, 8H9L8, which is directed against human CALCRL but cross-reacts with the rat and mouse forms of the receptor. We confirmed antibody specificity via Western blot analyses and immunocytochemistry using the CALCRL-expressing neuroendocrine tumour cell line BON-1 and a CALCRL-specific small interfering RNA (siRNA). We then used the antibody for immunohistochemical analyses of various formalin-fixed, paraffin-embedded specimens of normal and neoplastic tissues. In nearly all tissue specimens examined, CALCRL expression was detected in the capillary endothelium, smooth muscles of the arterioles and arteries, and immune cells. Analyses of normal human, rat, and mouse tissues revealed that CALCRL was primarily present in distinct cell populations in the cerebral cortex; pituitary; dorsal root ganglia; epithelia, muscles, and glands of the larger bronchi; intestinal mucosa (particularly in enteroendocrine cells); intestinal ganglia; exocrine and endocrine pancreas; arteries, capillaries, and glomerular capillary loops in the kidneys; the adrenals; Leydig cells in the testicles; and syncytiotrophoblasts in the placenta. In the neoplastic tissues, CALCRL was predominantly expressed in thyroid carcinomas, parathyroid adenomas, small-cell lung cancers, large-cell neuroendocrine carcinomas of the lung, pancreatic neuroendocrine neoplasms, renal clear-cell carcinomas, pheochromocytomas, lymphomas, and melanomas. In these tumours with strong expression of CALCRL, the receptor may represent a useful target structure for future therapies.

Composite Separable Microneedles for Transdermal Delivery and Controlled Release of Salmon Calcitonin for Osteoporosis Therapy

A composite separable microneedles (MNs) system consisting of silk fibroin (SF) needle tips and hyaluronic acid (HA) base is developed for transdermal delivery of salmon calcitonin (sCT) for therapy of osteoporosis. Poly(ethylene glycol) (PEG) is used to modulate the conformation structure of SF to achieve controllable sustained release of sCT. The prepared MNs can effectively penetrate the skin stratum corneum. After application to the skin, the HA base is dissolved within 2 min, allowing these SF drug depots to be implanted into the skin for controllable sustained release of sCT. The release kinetics of sCT can be controlled by regulating the conformation of SF with PEG and the interaction between sCT peptide and SF proteins. Compared with traditional needle injection, delivery of sCT using optimized HA-PEG/SF MNs shows better trabecular bone repair for ovariectomized-induced osteoporosis in mice. The proposed MNs system provides a new noninjection strategy for therapy of osteoporosis.

Chemical Synthesis of Proteins with Base-Labile Posttranslational Modifications Enabled by a Boc-SPPS Based General Strategy Towards Peptide C-Terminal Salicylaldehyde Esters

Chemical synthesis of proteins bearing base-labile post-translational modifications (PTMs) is a challenging task. For instance, O-acetylation and S-palmitoylation PTMs cannot survive Fmoc removal conditions during Fmoc-solid phase peptide synthesis (SPPS). In this work, we developed a new Boc-SPPS-based strategy for the synthesis of peptide C-terminal salicylaldehyde (SAL) esters, which are the key reaction partner in Ser/Thr ligation and Cys/Pen ligation. The strategy utilized the semicarbazone-modified aminomethyl (AM) resin, which could support the Boc-SPPS and release the peptide SAL ester upon treatment with TFA/H₂ O and pyruvic acid. The non-oxidative aldehyde regeneration was fully compatible with all the canonical amino acids. Armed with this strategy, we finished the syntheses of the O-acetylated protein histone H3(S10ac, T22ac) and the hydrophobic S-palmitoylated peptide derived from caveolin-1.

Construction of Active Protein Materials: Manipulation on Morphology of Salmon Calcitonin Assemblies with Enhanced Bone Regeneration Effect

The effect of protein drugs is always limited by their relatively low stability and fast degradation property; thus, various elegant efforts have been made to improve the bioactivity and biocompatibility of the protein drugs. Here, an alternative way is proposed to solve this problem. By simply adding a limited amount of small-molecular regulator, which tunes the subtle balance of protein-protein interactions (PPIs) and disulfide bond formation, the self-assembly property of the protein drug can be regulated, forming an "active protein material" itself. This means that, the resulting biomaterial is dominated by the protein drug and water, with significantly enhanced bone regeneration effect compared to the virgin protein in vitro and in vivo, through multivalent effect between the protein and receptor and the retarded degradation of the assembled proteins. In this active protein material, the protein drug is not only the active drug, but also the drug carrier, which greatly increases the drug-loading efficiency of the biomaterial, indicating the advantages of the easy preparation, high efficiency, and low cost of the active protein material with a bright future in biomedical applications.

Dihydrocaffeic Acid-Decorated Iron Oxide Nanomaterials Effectively Inhibit Human Calcitonin Aggregation

To date, more than 30 human peptides or proteins have been found to form amyloid fibrils, most of which are associated with human diseases. However, currently, no cure for amyloidosis exists. Therefore, development of therapeutic strategies to inhibit amyloid formation is urgently required. Although the role of some amyloidogenic proteins has not been identified in certain diseases, their self-assembling behavior largely affects their bioactivity. Human calcitonin (hCT) is a hormone peptide containing 32 amino acids and is secreted by the parafollicular cells of the thyroid gland in the human body. It can regulate the concentration of calcium ions in the blood and block the activity of osteoclasts. Therefore, calcitonin has also been considered a therapeutic peptide. However, the aggregation of hCT hinders this process, and hCT has been replaced by salmon calcitonin in drug formulations. Recently, iron oxide nanomaterials have been developed as potential materials for various applications owing to their high biocompatibility, low toxicity, and ease of functionalization. In this study, nanoparticles (NPs) were prepared using a simple chemical coprecipitation method. We first demonstrated that dopamine-conjugated Fe₃O₄ inhibited hCT aggregation, similar to what we found when carbon dots were used as core materials in the previous study. Later, we continued to simplify the preparation process, that is, the mixing of dihydrocaffeic acid (DCA) and iron oxide NPs, to maintain their stability and inhibitory effect against hCT aggregation. Furthermore, DCA-decorated Fe₃O₄ can dissociate preformed hCT amyloid fibrils. This appears to be one of the most promising ways to stabilize hCT in solution and may be helpful for amyloidosis treatment.

Thermo-Sensitive mPEG-PA-PLL Hydrogel for Drug Release of Calcitonin

The oral route is the most popular way of drug administration because of good patient compliance and ease of use. However, the oral delivery of peptides and proteins is difficult, mainly due to poor oral bioavailability. In past decades, researchers have developed several strategies to improve oral bioavailability by avoiding losing activity in the gastrointestinal (GI) tract and enhancing the intestinal permeability of these drugs. Methoxy poly(ethylene glycol)-poly(l-alanine) (mPEG-PA) is a thermo-sensitive hydrogel exhibiting a sol-to-gel phase transition property. This characteristic is appropriate for encapsulating peptide or protein drugs. To enhance the adhesion ability to intestinal mucus, a thermo-sensitive polymer, mPEG-PA, modified with charged amino acid lysine was developed. This positively charged material would help to bind the negatively charged mucin in mucus. The synthesis was conducted by individually synthesizing mPEG-PA and poly(l-lysine) (PLL) of different lengths via ring-opening polymerization. Then, mPEG-PA and PLL were combined using an NHS ester reaction to synthesize the triblock copolymer (mPEG-PA-PLL). Biocompatibility and the release of calcitonin from the synthesized hydrogel particles under different pH were examined. The initial data showed that the newly design material had a promising potential for the oral delivery of peptide drugs.

Tyrosine 12 of human calcitonin modulates its amyloid formation, membrane binding, and bioactivity

Irreversible aggregation greatly limits the bioavailability and therapeutic activity of peptide-based drugs, so preventing protein or peptide aggregation is a common issue in drug formulation. Human calcitonin (hCT), a peptide hormone secreted by thyroidal parafollicular cells, can regulate blood calcium levels and maintain bone structure. Hence, it can be used as a treatment for metabolic bone diseases, such as osteoporosis and Paget's disease. However, hCT has a relatively high propensity to form amyloid fibrils that hinder its biological function and limit its pharmaceutical potential. In previous studies, we demonstrated, along with other research groups, that modifying specific residues of hCT is sufficient to prevent hCT aggregation. We proceeded to find the key residues that regulate the aggregation of hCT for a better understanding of the mechanism of hCT aggregation. In this work, we used amyloid propensity prediction software and found that Tyr12 may play a key role in regulating hCT aggregation. Thus, we propose three human calcitonin variants (Y12E, Y12P, Y12R) for hCT non-amyloidogenic substituents and examined the aggregation characteristics of variants using multiple biophysical techniques. Y12E showed the best anti-aggregation propensity and can work as inhibitor of hCT aggregation. We also found this residue is crucial for membrane binding and receptor binding. The data presented herein provides an overview of Tyr12 that should be carefully considered in peptide design.

Beyond CGRP: The calcitonin peptide family as targets for migraine and pain

The CGRP system has emerged as a key pharmacological target for the treatment of migraine. However, some individuals who suffer from migraine have low or no response to anti-CGRP or other treatments, suggesting the need for additional clinical targets. CGRP belongs to the calcitonin family of peptides, which includes calcitonin, amylin, adrenomedullin and adrenomedullin 2. These peptides display a range of pro-nociceptive and anti-nociceptive actions, in primary headache conditions such as migraine. Calcitonin family peptides also show expression at sites relevant to migraine and pain. This suggests that calcitonin family peptides and their receptors, beyond CGRP, may be therapeutically useful in the treatment of migraine and other pain disorders. This review considers the localisation of the calcitonin family in peripheral pain pathways and discusses how they may contribute to migraine and pain. LINKED ARTICLES: This article is part of a themed issue on Advances in Migraine and Headache Therapy (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.3/issuetoc.

Examination of Effective Buccal Absorption of Salmon Calcitonin Using Cell-Penetrating Peptide-Conjugated Liposomal Drug Delivery System

Introduction

The buccal route has been considered an attractive alternative delivery route for injectable formulations. Cell-penetrating peptides (CPPs) are gaining increased attention for their cellular uptake and tissue permeation effects. This study was aimed to evaluate the in vitro and ex vivo permeation-enhancing effect of penetratin-conjugated liposomes for salmon calcitonin (sCT) in TR146 human buccal cells and porcine buccal tissues.

Methods

Penetratin was conjugated to phospholipids through a maleimide-thiol reaction. Liposomes were prepared and sCT was encapsulated using a thin-film hydration method. Physical properties such as particle size, zeta potential, encapsulation efficiency, and morphological images via transmission electron microscopy were obtained. Cellular uptake studies were conducted using flow cytometry (FACS) and confocal laser scanning microscopy (CLSM). A cell permeation study was performed using a Transwell^® assay, and permeation through porcine buccal tissue was evaluated. The amount of sCT permeated was quantified using an ELISA kit and was optically observed using CLSM.

Results

The particle size of penetratin-conjugated liposomes was approximately 123.0 nm, their zeta potential was +29.6 mV, and their calcitonin encapsulation efficiency was 18.0%. In the cellular uptake study using FACS and CLSM, stronger fluorescence was observed in penetratin-conjugated liposomes compared with the solution containing free sCT and control liposomes. Likewise, the amount of sCT permeated from penetratin-conjugated liposomes was higher than that from the free sCT solution and control liposomes by 5.8-fold across TR146 cells and 91.5-fold across porcine buccal tissues.

Conclusion

Penetratin-conjugated liposomes are considered a good drug delivery strategy for sCT via the buccal route.

Systemic therapies for preventing or treating aromatase inhibitor-induced musculoskeletal symptoms in early breast cancer

BACKGROUND

Adjuvant aromatase inhibitors (AI) improve survival compared to tamoxifen in postmenopausal women with hormone receptor-positive stage I to III breast cancer. In approximately half of these women, AI are associated with aromatase inhibitor-induced musculoskeletal symptoms (AIMSS), often described as symmetrical pain and soreness in the joints, musculoskeletal pain and joint stiffness. AIMSS may have significant and prolonged impact on women's quality of life. AIMSS reduces adherence to AI therapy in up to a half of women, potentially compromising breast cancer outcomes. Differing systemic therapies have been investigated for the prevention and treatment of AIMSS, but the effectiveness of these therapies remains unclear.

OBJECTIVES

To assess the effects of systemic therapies on the prevention or management of AIMSS in women with stage I to III hormone receptor-positive breast cancer.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, WHO International Clinical Trials Registry Platform (ICTRP) and Clinicaltrials.gov registries to September 2020 and the Cochrane Breast Cancer Group (CBCG) Specialised Register to March 2021.  SELECTION CRITERIA: We included all randomised controlled trials that compared systemic therapies to a comparator arm. Systemic therapy interventions included all pharmacological therapies, dietary supplements, and complementary and alternative medicines (CAM). All comparator arms were allowed including placebo or standard of care (or both) with analgesia alone. Published and non-peer-reviewed studies were eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened studies, extracted data, and assessed risk of bias and certainty of the evidence using the GRADE approach. Outcomes assessed were pain, stiffness, grip strength, safety data, discontinuation of AI, health-related quality of life (HRQoL), breast cancer-specific quality of life (BCS-QoL), incidence of AIMSS, breast cancer-specific survival (BCSS) and overall survival (OS). For continuous outcomes, we used vote-counting by reporting how many studies reported a clinically significant benefit within the confidence intervals (CI) of the mean difference (MD) between treatment arms, as determined by the minimal clinically importance difference (MCID) for that outcome scale. For dichotomous outcomes, we reported outcomes as a risk ratio (RR) with 95% CI.

MAIN RESULTS

We included 17 studies with 2034 randomised participants. Four studies assessed systemic therapies for the prevention of AIMSS and 13 studies investigated treatment of AIMSS. Due to the variation in systemic therapy studies, including pharmacological, and CAM, or unavailable data, meta-analysis was limited, and only two trials were combined for meta-analysis. The certainty of evidence for all outcomes was either low or very low certainty. Prevention studies The evidence is very uncertain about the effect of systemic therapies on pain (from baseline to the end of the intervention; 2 studies, 183 women). The two studies, investigating vitamin D and omega-3 fatty acids, showed a treatment effect with 95% CIs that did not include an MCID for pain. Systemic therapies may have little to no effect on grip strength (RR 1.08, 95% CI 0.37 to 3.17; 1 study, 137 women) or on women continuing to take their AI (RR 0.16, 95% 0.01 to 2.99; 1 study, 147 women). The evidence suggests little to no effect on HRQoL and BCS-QoL from baseline to the end of intervention (the same single study; 44 women, both quality of life outcomes showed a treatment effect with 95% CIs that did include an MCID). The evidence is very uncertain for outcomes assessing incidence of AIMSS (RR 0.82, 95% CI 0.63 to 1.06; 2 studies, 240 women) and the safety of systemic therapies (4 studies, 344 women; very low-certainty evidence). One study had a US Food and Drug Administration alert issued for the intervention (cyclo-oxygenase-2 inhibitor) during the study, but there were no serious adverse events in this or any study. There were no data on stiffness, BCSS or OS. Treatment studies The evidence is very uncertain about the effect of systemic therapies on pain from baseline to the end of intervention in the treatment of AIMSS (10 studies, 1099 women). Four studies showed an MCID in pain scores which fell within the 95% CI of the measured effect (vitamin D, bionic tiger bone, Yi Shen Jian Gu granules, calcitonin). Six studies showed a treatment effect with 95% CI that did not include an MCID (vitamin D, testosterone, omega-3 fatty acids, duloxetine, emu oil, cat's claw).  The evidence was very uncertain for the outcomes of change in stiffness (4 studies, 295 women), HRQoL (3 studies, 208 women) and BCS-QoL (2 studies, 147 women) from baseline to the end of intervention. The evidence suggests systemic therapies may have little to no effect on grip strength (1 study, 107 women). The evidence is very uncertain about the safety of systemic therapies (10 studies, 1250 women). There were no grade four/five adverse events reported in any of the studies. The study of duloxetine reported more all-grade adverse events in this treatment group than comparator group. There were no data on the incidence of AIMSS, the number of women continuing to take AI, BCCS or OS from the treatment studies.

AUTHORS' CONCLUSIONS

AIMSS are chronic and complex symptoms with a significant impact on women with early breast cancer taking AI. To date, evidence for safe and effective systemic therapies for prevention or treatment of AIMSS has been minimal. Although this review identified 17 studies with 2034 randomised participants, the review was challenging due to the heterogeneous systemic therapy interventions and study methodologies, and the unavailability of certain trial data. Meta-analysis was thus limited and findings of the review were inconclusive. Further research is recommended into systemic therapy for AIMSS, including high-quality adequately powered RCT, comprehensive descriptions of the intervention/placebo, and robust definitions of the condition and the outcomes being studied.

Identification of Antimicrobial Peptides Isolated From the Skin Mucus of African Catfish, Clarias gariepinus (Burchell, 1822)

Antimicrobial peptides (AMPs) constitute a broad range of bioactive compounds in diverse organisms, including fish. They are effector molecules for the innate immune response, against pathogens, tissue damage and infections. Still, AMPs from African Catfish, Clarias gariepinus, skin mucus are largely unexplored despite their possible therapeutic role in combating antimicrobial resistance. In this study, African Catfish Antimicrobial peptides (ACAPs) were identified from the skin mucus of African Catfish, C. gariepinus. Native peptides were extracted from fish mucus scrapings in 10% acetic acid (v/v) and ultra-filtered using 5 kDa molecular weight cut-off membrane. The extract was purified using C18 Solid-Phase Extraction. The antibacterial activity was determined using the Agar Well Diffusion method and broth-dilution method utilizing Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922). Thereafter, Sephadex G-25 gel filtration was further utilized in bio-guided isolation of the most active fractions prior to peptide identification using Orbitrap Fusion Lumos Tribrid Mass Spectrometry. The skin mucus extracted from African Catfish from all the three major lakes of Uganda exhibited antimicrobial activity on E. coli and S. aureus. Lake Albert's C. gariepinus demonstrated the best activity with the lowest MIC of 2.84 and 0.71 μg/ml on S. aureus and E. coli, respectively. Sephadex G-25 peak I mass spectrometry analysis (Data are available via ProteomeXchange with identifier PXD029193) alongside in silico analysis revealed seven short peptides (11-16 amino acid residues) of high antimicrobial scores (0.561-0.905 units). In addition, these peptides had a low molecular weight (1005.57-1622.05 Da) and had percentage hydrophobicity above 54%. Up to four of these AMPs demonstrated α-helix structure conformation, rendering them amphipathic. The findings of this study indicate that novel AMPs can be sourced from the skin mucus of C. gariepinus. Such AMPs are potential alternatives to the traditional antibiotics and can be of great application to food and pharmaceutical industries; however, further studies are still needed to establish their drug-likeness and safety profiles.

The effect of salmon calcitonin against glutamate-induced cytotoxicity in the C6 cell line and the roles the inflammatory and nitric oxide pathways play

Recent evidence has shown that salmon calcitonin (sCT) has positive effects on the nervous system. However, its effect and mechanisms on glutamate-induced cytotoxicity are still unclear. The current experiment was designed to examine the effect of sCT on glutamate-induced cytotoxicity in C6 cells, involving the inflammatory and nitric oxide stress pathways. The study used the C6 glioma cell line. Four cell groups were prepared to evaluate the effect of sCT on glutamate-induced cytotoxicity. The control group was without any treatment. Cells in the glutamate group were treated with 10 mM glutamate for 24 h. Cells in the sCT group were treated with various concentrations (3, 6, 12, 25, and 50 µg/mL) of sCT for 24 h. Cells in the sCT + glutamate group were pre-treated with various concentrations of sCT for 1 h and then exposed to glutamate for 24 h. The cell viability was evaluated with an XTT assay. Nuclear factor kappa b (NF-kB), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), neuronal nitric oxide synthase (nNOS), nitric oxide (NO), cyclic guanosine monophosphate (cGMP), caspase-3, and caspase-9 levels in the cells were measured by ELISA kits. Apoptosis was detected by flow cytometry method. sCT at all concentrations significantly improved the cell viability in C6 cells after glutamate-induced cytotoxicity (p < 0.001). Moreover, sCT significantly reduced the levels of NF-kB (p < 0.001), TNF-α, and IL-6 levels (p < 0.001). sCT also decreased nNOS, NO, and cGMP levels (P < 0.001). Furthermore, it decreased the apoptosis rate and increased the live-cell rate in the flow cytometry (P < 0.001). In conclusion, sCT has protective effects on glutamate-induced cytotoxicity in C6 glial cells by inhibiting inflammatory and nitric oxide pathways. sCT could be a useful supportive agent for people with neurodegenerative symptoms.

Dopamine-Conjugated Carbon Dots Inhibit Human Calcitonin Fibrillation

The development of biocompatible nanomaterials has become a new trend in the treatment and prevention of human amyloidosis. Human calcitonin (hCT), a hormone peptide secreted from parafollicular cells, plays a major role in calcium–phosphorus metabolism. Moreover, it can be used in the treatment of osteoporosis and Paget’s disease. Unfortunately, it tends to form amyloid fibrils irreversibly in an aqueous solution, resulting in a reduction of its bioavailability and therapeutic activity. Salmon calcitonin is the replacement of hCT as a widely therapeutic agent due to its lower propensity in aggregation and better bioactivity. Herein, we used citric acid to synthesize carbon dots (CDs) and modified their surface properties by a variety of chemical conjugations to provide different functionalized CDs. It was found that dopamine-conjugated CDs can effectively inhibit hCT aggregation especially in the fibril growth phase and dissociate preformed hCT amyloids. Although the decomposition mechanism of dopamine-conjugated CDs is not clear, it seems to be specific to hCT amyloids. In addition, we also tested dopamine-conjugated mesoporous silica nanoparticles in preventing hCT fibrillization. They also can work as inhibitors but are much less effective than CDs. Our studies emphasized the importance of the size and surface functionalization of core materials in the development of nanomaterials as emerging treatments for amyloidosis. On the other hand, proper functionalized CDs would be useful in hCT formulation.

PEG-based thermosensitive and biodegradable hydrogels

Injectable thermosensitive hydrogels are free-flowing polymer solutions at low or room temperature, making them easy to encapsulate the therapeutic payload or cells via simply mixing. Upon injection into the body, in situ forming hydrogels triggered by body temperature can act as drug-releasing reservoirs or cell-growing scaffolds. Finally, the hydrogels are eliminated from the administration sites after they accomplish their missions as depots or scaffolds. This review outlines the recent progress of poly(ethylene glycol) (PEG)-based biodegradable thermosensitive hydrogels, especially those composed of PEG-polyester copolymers, PEG-polypeptide copolymers and poly(organophosphazene)s. The material design, performance regulation, thermogelation and degradation mechanisms, and corresponding applications in the biomedical field are summarized and discussed. A perspective on the future thermosensitive hydrogels is also highlighted. STATEMENT OF SIGNIFICANCE: Thermosensitive hydrogels undergoing reversible sol-to-gel phase transitions in response to temperature variations are a class of promising biomaterials that can serve as minimally invasive injectable systems for various biomedical applications. Hydrophilic PEG is a main component in the design and fabrication of thermoresponsive hydrogels due to its excellent biocompatibility. By incorporating hydrophobic segments, such as polyesters and polypeptides, into PEG-based systems, biodegradable and thermosensitive hydrogels with adjustable properties in vitro and in vivo have been developed and have recently become a research hotspot of biomaterials. The summary and discussion on molecular design, performance regulation, thermogelation and degradation mechanisms, and biomedical applications of PEG-based thermosensitive hydrogels may offer a demonstration of blueprint for designing new thermogelling systems and expanding their application scope.

Recent advances in proteolytic stability for peptide, protein, and antibody drug discovery

Introduction: To discover and develop a peptide, protein, or antibody into a drug requires overcoming multiple challenges to obtain desired properties. Proteolytic stability is one of the challenges and deserves a focused investigation.Areas covered: This review concentrates on improving proteolytic stability by engineering the amino acids around the cleavage sites of a liable peptide, protein, or antibody. Peptidases are discussed on three levels including all peptidases in databases, mixtures based on organ and tissue types, and individual peptidases. The technique to identify cleavage sites is spotlighted on mass spectrometry-based approaches such as MALDI-TOF and LC-MS. For sequence engineering, the replacements that have been commonly applied with a higher chance of success are highlighted at the beginning, while the rarely used and more complicated replacements are discussed later. Although a one-size-fits-all approach does not exist to apply to different projects, this review provides a 3-step strategy for effectively and efficiently conducting the proteolytic stability experiments to achieve the eventual goal of improving the stability by engineering the molecule itself.Expert opinion: Improving the proteolytic stability is a spiraling up process sequenced by testing and engineering. There are many ways to engineer amino acids, but the choice must consider the cost and properties affected by the changes of the amino acids.

Effects of Teriparatide versus Salmon Calcitonin Therapy for the Treatment of Osteoporosis in Asia: A Meta-analysis of Randomized Controlled Trials

Objective:

The objective of this meta-analysis was to compare the efficacy and safety of teriparatide versus salmon calcitonin for the treatment of osteoporosis in Asian patients and to investigate whether the results of global studies could be applicable to Asian patients.

Methods:

PubMed, OVID, Cochrane Central Register of Controlled Trials (CENTRAL) and EMBASE up to December 2018 were searched. Eligible randomized controlled trials (RCTs) that compared teriparatide versus salmon calcitonin in Asian osteoporosis population were included. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used for data synthesis, and Cochrane Collaboration software Review Manager 5.3 was used to analyze the pooled data.

Results:

Three RCTs involving 529 patients were included (mean age 68.7 yr; 93.4% females; mean follow-up 6 months); outcome measures included bone mineral density (BMD) of the femoral neck, total hip and lumbar spine; bone markers and adverse events. We found that the period of 6-months of teriparatide treatment was helpful for the improvement of the BMD of lumbar vertebra, however, the improvement of BMD was not significant in the femoral neck and total hip joint. There was a positive correlation between bone-specific alkaline phosphatase (BSAP) and osteocalcin (OCN) and the response of Asian patients to subcutaneous injection of 20 micrograms per day of teriparatide. The proportion of the occurrence of adverse effects was more obvious in the teriparatide group compared with salmon calcitonin, but there was no significant difference.

Conclusion:

Results suggested that the use of teriparatide could improve the lumbar BMD by shortterm (six months) application in Asian osteoporosis patients, which is beneficial to the patients who cannot tolerate adverse events of long-term treatment. The BSAP and OCN bone markers could be useful to monitor the responses of Asian osteoporosis patients to teriparatide treatment. Finally, both of teriparatide and salmon calcitonin were well tolerated by Asian patients.

Efficacy and safety of 18 anti-osteoporotic drugs in the treatment of patients with osteoporosis caused by glucocorticoid: A network meta-analysis of randomized controlled trials

Background

Glucocorticoids are widely used in a variety of diseases, especially autoimmune diseases and inflammatory diseases, so the incidence of glucocorticoid-induced osteoporosis is high all over the world.

Objectives

The purpose of this paper is to use the method of network meta-analysis (NMA) to compare the efficacy of anti-osteoporosis drugs directly and indirectly, and to explore the advantages of various anti-osteoporosis drugs based on the current evidence.

Methods

We searched PubMed, Embase and Cochrane Library for randomized controlled trials (RCTs), of glucocorticoid-induced osteoporosis (GIOP) and compared the efficacy and safety of these drugs by NMA. The risk ratio (RR) and its 95% confidence interval (CI) are used as the influence index of discontinuous data, and the standardized mean difference (SMD) and its 95% CI are used as the influence index of continuous data. The statistical heterogeneity was evaluated by the calculated estimated variance (τ²), and the efficacy and safety of drugs were ranked by the surface under the cumulative ranking curve (SUCRA). The main outcome of this study was the incidence of vertebral fracture after taking several different types of drugs, and the secondary results were the incidence of non-vertebral fracture and adverse events, mean percentage change of lumbar spine (LS) and total hip (TH)bone mineral density (BMD) from baseline to at least 12 months.

Results

Among the different types of anti-GIOP, teriparatide (SUCRA 95.9%) has the lowest incidence of vertebral fracture; ibandronate (SUCRA 75.2%) has the lowest incidence of non-vertebral fracture; raloxifene (SUCRA 98.5%) has the best effect in increasing LS BMD; denosumab (SUCRA 99.7%) is the best in increasing TH BMD; calcitonin (SUCRA 92.4%) has the lowest incidence of serious adverse events.

Conclusions

Teriparatide and ibandronate are effective drugs to reduce the risk of vertebral and non-vertebral fractures in patients with GIOP. In addition, long-term use of raloxifene and denosumab can increase the BMD of LS and TH.

Water/pH dual responsive in situ calcium supplement collaborates simvastatin for osteoblast promotion mediated osteoporosis therapy via oral medication

Calcium supplement is the most commonly adopted treatment for osteoporosis but usually requires high dose and frequency. The modality of calcium supplement is therefore overlooked by current nanomedicine-based osteoporosis therapies without proper oral formulations. Herein, we proposed a tetracycline (Tc) modified and monostearin (MS) coated amorphous calcium carbonate (ACC) platform (TMA) as oral bone targeted and osteoporosis microenvironment (water/pH) responsive carrier for in situ calcium supplement. Moreover, current osteoporosis therapies also fall short of finding suitable molecular target and effective therapeutic regimen to further increase the therapeutic efficacy over available treatment means. As a result, the simvastatin (Sim) was loaded into TMA to construct drug delivery system (TMA/Sim) capable of synergistically activating the bone morphogenetic proteins (BMPs)-Smad pathway to provide a novel therapeutic regimen for osteoblast promotion mediated osteoporosis therapy. Our results revealed that optimized TMA showed high accessibility and oral availability with targeted drug delivery to bone tissue. Most importantly, benefit from the effective in situ calcium supplement and targeted Sim delivery, this therapeutic regime (TMA/Sim) achieved better synergetic effects than conventional combination strategies with promising osteoporosis reversion performance under low calcium dosage (1/10 of commercial calcium carbonate tablet) and significantly attenuated side effects.

Fibrillation of Human Calcitonin and Its Analogs: Effects of Phosphorylation and Disulfide Reduction

Some therapeutic peptides self-assemble in solution to form ordered, insoluble, β-sheet-rich amyloid fibrils. This physical instability can result in reduced potency, cause immunogenic side effects, and limit options for formulation. Understanding the mechanisms of fibrillation is key to developing rational mitigation strategies. Here, amide hydrogen-deuterium exchange with mass spectrometric analysis (HDX-MS) coupled with proteolytic digestion was used to identify the early stage interactions leading to fibrillation of human calcitonin (hCT), a peptide hormone important in calcium metabolism. hCT fibrillation kinetics was sigmoidal, with lag, growth, and plateau phases as shown by thioflavin T and turbidity measurements. HDX-MS of fibrillating hCT (pH 7.4; 25°C) suggested early involvement of the N-terminal (1-11) and central (12-19) fragments in interactions during the lag phase, whereas C-terminal fragments (20-32 and 26-32) showed limited involvement during this period. The residue-level information was used to develop phosphorylated hCT analogs that showed modified fibrillation that depended on phosphorylation site. Phosphorylation in the central region resulted in complete inhibition of fibrillation for the phospho-Thr-13 hCT analog, whereas phosphorylation in the N-terminal and C-terminal regions inhibited but did not prevent fibrillation. Reduction of the Cys1-Cys7 disulfide bond resulted in faster fibrillation with involvement of different hCT residues as indicated by pulsed HDX-MS. Together, the results demonstrate that small structural changes have significant effects on hCT fibrillation and that understanding these effects can inform the rational development of fibrillation-resistant hCT analogs.

Impurities identification and quantification for calcitonin salmon by liquid chromatography-high resolution mass spectrometry

Calcitonin salmon is an important peptide pharmaceutical, which is mainly used for the treatment of osteoporosis and hypercalcemia. Structurally related peptide impurities in a peptide pharmaceutical probably have side effect or even toxicity, thus needs to be carefully characterized according to pharmacopoeia. With the improvement of analytical techniques, liquid chromatography-high resolution mass spectrometry (LC-HRMS) has become a pivotal technique for the identification and quantification of structurally related peptide impurities in peptide materials. In this study, an LC-HRMS-based method has been developed for the identification and quantification of structurally related peptide impurities in calcitonin salmon material. With this method, 7 peptide impurities (> 1 mg/g) in United States Pharmacopoeia (USP) reference standard and 9 peptide impurities (> 1 mg/g) in European Pharmacopoeia (EP) reference standard were identified and accurately quantified. Besides the peptide impurities reported by USP and EP, several new impurities such as [7-Dehydroalanine] calcitonin salmon, triple-sulfate-calcitonin salmon, [26-Proline] calcitonin salmon, [14-Glutamic acid] calcitonin salmon, [20-Glutamic acid] calcitonin salmon, [26-Aspartic acid] calcitonin salmon, calcitonin salmon acid were observed in the reference standard materials studied. The total mass fractions of all structurally related peptide impurities in calcitonin salmon study materials were estimated to be 57.4 mg/g for USP and 46.3 mg/g for EP with associated expended uncertainties at a 95 % confidence level of 5.2 mg/g (k = 2) and 3.1 mg/g (k = 2), respectively.

Thermosensitive Polysaccharide Hydrogel As a Versatile Platform for Prolonged Salmon Calcitonin Release and Calcium Regulation

The common pathological characteristic of osteoporosis and hypercalcemia is the disorder of calcium homeostasis. Currently, salmon calcitonin (sCT), a clinical regenerative medicine, is an attractive chioice to regulate calcium metabolism for alleviation of osteoporosis and hypercalcemia. Unfortunately, serum sCT is quickly cleared in vivo, leading to its short half-life. Here, we designed a versatile hydrogel, based on salmon calcitonin-oxidized calcium alginate (sCT-OCA) conjugate and hydroxypropyl chitin (HPCH). The release profile showed that sCT could be released from HPCH hydrogels loaded with sCT-OCA conjugate (sCT-OCA-HPCH) for at least 28 days with conformation stability. The cellular test demonstrated that the biocompatible sCT-OCA-HPCH, compared with sCT formulation, had capacity in up-regulating alkaline phosphatase activity (∼63% increase) and promoting calcium to deposit into extracellular matrix (∼42% increase). These results indicated that thermosensitive sCT-OCA-HPCH hydrogel herein is a versatile platform for many applications such as calcium metabolism regulation, osteoporosis treatment, and hypercalcemia therapy.

A New 1,25 Dihydroxy Vitamin D Analog with Strong Bone Anabolic Activity in OVX Rats with Little or no Bone Resorptive Activity

A new 1α,25-dihydroxy vitamin D₃ analog (2-methylene-22(E)-(24R)-22-dehydro-1α,24,25-trihydroxy-19-norvitamin D₃ or WT-51) has been tested as a possible therapeutic for osteoporosis. It is 1/10th as active as 1,25(OH)₂ D₃ in binding affinity for the vitamin D receptor but is at least 200 times more active than 1,25(OH)₂ D₃ and equal to that of 2MD (2-methylene-19-nor-(20S)-1α,25(OH)₂ D₃ , an analog previously tested in postmenopausal women), in supporting bone formation by isolated osteoblasts in culture. However, in contrast to 2MD, it is virtually inactive on bone resorption in vivo. WT-51 markedly increased bone mass (lumbar and femur) in ovariectomized (OVX) female rats. Further, bone strength tested by the three-point bending system is significantly increased by WT-51. Thus, WT-51 is an attractive candidate for the treatment of postmenopausal osteoporosis. © 2019 American Society for Bone and Mineral Research.

Flash Fabrication of Orally Targeted Nanocomplexes for Improved Transport of Salmon Calcitonin across the Intestine

Salmon calcitonin (sCT) is a potent calcium-regulating peptide hormone and widely applied for the treatment of some bone diseases clinically. However, the therapeutic usefulness of sCT is hindered by the frequent injection required, owing to its short plasma half-life and therapeutic need for a high dose. Oral delivery is a popular modality of administration for patients because of its convenience to self-administration and high patient compliance, while orally administered sCT remains a great challenge currently due to the existence of multiple barriers in the gastrointestinal (GI) tract. Here, we introduced an orally targeted delivery system to increase the transport of sCT across the intestine through both the paracellular permeation route and the bile acid pathway. In this system, sCT-based glycol chitosan-taurocholic acid conjugate (GC-T)/dextran sulfate (DS) ternary nanocomplexes (NC-T) were produced by a flash nanocomplexation (FNC) process in a kinetically controlled mode. The optimized NC-T exhibited well-controlled properties with a uniform and sub-60 nm hydrodynamic diameter, high batch-to-batch reproducibility, good physical or chemical stability, as well as sustained drug release behaviors. The studies revealed that NC-T could effectively improve the intestinal uptake and permeability, owing to its surface functionalization with the taurocholic acid ligand. In the rat model, orally administered NC-T showed an obvious hypocalcemia effect and a relative oral bioavailability of 10.9%. An in vivo assay also demonstrated that NC-T induced no observable side effect after long-term oral administration. As a result, the orally targeted nanocomplex might be a promising candidate for improving the oral transport of therapeutic peptides.

Calcitonin Receptor N-Glycosylation Enhances Peptide Hormone Affinity by Controlling Receptor Dynamics

The class B G protein-coupled receptor (GPCR) calcitonin receptor (CTR) is a drug target for osteoporosis and diabetes. N-glycosylation of asparagine 130 in its extracellular domain (ECD) enhances calcitonin hormone affinity with the proximal GlcNAc residue mediating this effect through an unknown mechanism. Here, we present two crystal structures of salmon calcitonin-bound, GlcNAc-bearing CTR ECD at 1.78 and 2.85 Å resolutions and analyze the mechanism of the glycan effect. The N130 GlcNAc does not contact the hormone. Surprisingly, the structures are nearly identical to a structure of hormone-bound, N-glycan-free ECD, which suggested that the GlcNAc might affect CTR dynamics not observed in the static crystallographic snapshots. Hydrogen-deuterium exchange mass spectrometry and molecular dynamics simulations revealed that glycosylation stabilized a β-sheet adjacent to the N130 GlcNAc and the N-terminal α-helix near the peptide-binding site while increasing flexibility of the peptide-binding site turret loop. These changes due to N-glycosylation increased the ligand on-rate and decreased its off-rate. The glycan effect extended to RAMP-CTR amylin receptor complexes and was also conserved in the related CGRP receptor. These results reveal that N-glycosylation can modulate GPCR function by altering receptor dynamics.

Thermosensitive Hydrogel Based on Poly(2-Ethyl-2-Oxazoline)-Poly(D,L-Lactide)-Poly(2-Ethyl-2-Oxazoline) for Sustained Salmon Calcitonin Delivery

This study developed a thermosensitive hydrogel based on poly(2-ethyl-2-oxazoline)-poly(D,L-lactide)-poly(2-ethyl-2-oxazoline) (PPP) for the delivery of salmon calcitonin to improve the hypocalcemic effect. The tube inversion and rheological tests revealed that the copolymer solution underwent temperature-dependent sol-gel-sol transitions. Observation by scanning electron microscopy (SEM) showed that the hydrogel exhibited a porous three-dimensional network. The swelling test demonstrated that there was a maximum swelling ratio at low temperature (25°C) as compared with the high temperature (37°C). In vitro release revealed that the PPP hydrogel were capable of sustained release of salmon calcitonin (sCT). The in vivo biodegradability study indicated the good degradability of PPP hydrogel. More importantly, the in vivo retention time of the hydrogel in situ was significantly prolonged after subcutaneous injection of the PPP hydrogel compared to the F127 hydrogel. In vivo pharmacodynamics analysis showed that the hypocalcemic effect of both PPP and F127 hydrogel was significantly greater than that of sCT solution, and the mean serum Ca reduction effect could be maintained for 24 h of PPP hydrogel, indicating that PPP hydrogel could achieve a significant enhanced hypocalcemic effect. In conclusion, the PPP hydrogel has been shown to be prospective as a controlled release carrier for injection delivery of protein drugs.

Calcitonin and Bone Physiology: In Vitro, In Vivo, and Clinical Investigations

Calcitonin was discovered as a peptide hormone that was known to reduce the calcium levels in the systemic circulation. This hypocalcemic effect is produced due to multiple reasons such as inhibition of bone resorption or suppression of calcium release from the bone. Thus, calcitonin was said as a primary regulator of the bone resorption process. This is the reason why calcitonin has been used widely in clinics for the treatment of bone disorders such as osteoporosis, hypercalcemia, and Paget's disease. However, presently calcitonin usage is declined due to the development of efficacious formulations of new drugs. Calcitonin gene-related peptides and several other peptides such as intermedin, amylin, and adrenomedullin (ADM) are categorized in calcitonin family. These peptides are known for the structural similarity with calcitonin. Aside from having a similar structure, these peptides have few overlapping biological activities and signal transduction action through related receptors. However, several other activities are also present that are peptide specific. In vitro and in vivo studies documented the posttreatment effects of calcitonin peptides, i.e., positive effect on bone osteoblasts and their formation and negative effect on osteoclasts and their resorption. The recent research studies carried out on genetically modified mice showed the inhibition of osteoclast activity by amylin, while astonishingly calcitonin plays its role by suppressing osteoblast and bone turnover. This article describes the review of the bone, the activity of the calcitonin family of peptides, and the link between them.

[Calcitonin as an analgesic agent: review of mechanisms of action and clinical applications]

BACKGROUND AND OBJECTIVES

Calcitonin is a polypeptide hormone regulating the metabolism calcium in the body. For many years calcitonin has been used to maintain and improve bone mineral density and to reduce the fracture rate. Many studies showed that calcitonin had analgesic role in several painful circumstances. This pain-ameliorating effect is irrelevant to its osteoclastic inhibitory effect and mechanisms like altering Na+ channel and serotonin receptor expression or hypothesis including the endorphin-mediated mechanism were used to explain this effect. In this study we performed a thorough review on the role of calcitonin as an analgesic agent in different scenarios and investigated the fact that calcitonin can be a feasible medication to relieve pain.

METHOD

Many studies focused on the analgesic effect of calcitonin in several painful circumstances, including acute pains related to vertebral fractures, metastasis, migraine and reflex sympathetic dystrophy as well as neuropathic pains related to spinal injuries or diabetes, and phantom pain. Also, calcitonin was showed to be a useful additive to local anesthesia in the case of controlling postoperative pain or trigeminal neuralgia more effectively. However we faced some contradictory data for conditions like lumbar canal stenosis, complex regional pain syndrome, phantom pain and malignancies.

CONCLUSION

This study showed that calcitonin could be helpful analgesic agent in different painful situations. Calcitonin can be considered an eligible treatment for acute pains related to vertebral fractures and a feasible alternative for the treatment of the acute and chronic neuropathic pains where other medications might fail.

Calcitonin as an analgesic agent: review of mechanisms of action and clinical applications

Background and objectives

Calcitonin is a polypeptide hormone regulating the metabolism of calcium in the body. For many years calcitonin has been used to maintain and improve bone mineral density and to reduce the fracture rate. Many studies showed that calcitonin had analgesic role in several painful circumstances. This pain-ameliorating effect is irrelevant to its osteoclastic inhibitory effect and mechanisms like altering Na+ channel and serotonin receptor expression or hypothesis including the endorphin-mediated mechanism were used to explain this effect. In this study we performed a thorough review on the role of calcitonin as an analgesic agent in different scenarios and investigated the fact that calcitonin can be a feasible medication to relieve pain.

Method

Many studies focused on the analgesic effect of calcitonin in several painful circumstances, including acute pains related to vertebral fractures, metastasis, migraine and reflex sympathetic dystrophy as well as neuropathic pains related to spinal injuries or diabetes, and phantom pain. Also, calcitonin was showed to be a useful additive to local anesthesia in the case of controlling postoperative pain or trigeminal neuralgia more effectively. However we faced some contradictory data for conditions like lumbar canal stenosis, complex regional pain syndrome, phantom pain and malignancies.

Conclusion

This study showed that calcitonin could be helpful analgesic agent in different painful situations. Calcitonin can be considered an eligible treatment for acute pains related to vertebral fractures and a feasible alternative for the treatment of the acute and chronic neuropathic pains where other medications might fail.

Effects of Salmon Calcitonin on the Concentrations of Monoamines in Periaqueductal Gray in Formalin Test

Background:

The receptors of salmon calcitonin, located on certain areas of the brain such as the periaqueductal gray matter, are responsible for pain modulation.

Aims:

The effects of intracerebroventricular injection of salmon calcitonin on the behavioral response to pain and on the levels of monoamines in the periaqueductal gray were explored using a biphasic animal model of pain.

Study Design:

Animal experiment.

Methods:

A total of 45 male rats were divided into four groups (n=6). Salmon calcitonin was injected into the lateral ventricle of the brain (1.5 nmol, with a volume of 5 μL). After 20 min, 2.5% formalin was subcutaneously injected into the right leg claw, and pain behavior was recorded on a numerical basis. At the time of the formalin test, the periaqueductal gray area was microdialized. High-performance liquid chromatography method was used to gauge the levels of monoamines and their metabolites.

Results:

Intracerebroventricular injections of salmon calcitonin resulted in pain reduction in the formalin test (p<0.05). The dialysate concentrations of serotonin, dopamine, norepinephrine, 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic, and 4-hydroxy-3-methoxyphenylglycol increased in the periaqueductal gray area in different phases of the formalin pain test (p<0.05).

Conclusion:

Salmon calcitonin reduced pain by increasing the concentrations of monoamines and the metabolites derived from them in the periaqueductal gray area.

Development and characterization of supramolecular calcitonin assembly and assessment of its interactions with the bone remodelling process

Osteoporosis is the most common metabolic bone disease, which poses an immense socio-economic burden on the society. Human calcitonin, though safe, is not considered as a therapeutic option because of its high tendency to self-associate to form amyloid fibrils thereby affecting its potency. To circumvent this issue we harnessed the inherent capacity of aggregation and developed an assemblage of human calcitonin monomers, [Supramolecular Calcitonin Assembly (SCAI)], which releases biologically active calcitonin monomers in a sustained manner for a period of at least three weeks. AFM and FT-IR analysis showed that SCA-I is amorphous aggregates of calcitonin monomers. Both SCA-I and monomer released from it demonstrated superior anti-osteoclast activity and proteolytic stability in-vitro. SCA-I upon single injection significantly improved bone formation markers and reduced bone resorption markers in ovariectomized (OVX) rat model of postmenopausal osteoporosis. Micro-CT analysis revealed that calcitonin released from SCA-I exhibits its beneficial effect on cortical bone more profoundly compared to trabecular bone. This study demonstrates that SCA-I is more effective compared to the human calcitonin monomers on osteoclasts and has site-specific effect on bone in a model of post-menopausal osteoporosis. This approach opens up an innovative way to use and study the function of human calcitonin.

Activation of amylin receptors attenuates alcohol-mediated behaviours in rodents

Alcohol expresses its reinforcing properties by activating areas of the mesolimbic dopamine system, which consists of dopaminergic neurons projecting from the ventral tegmental area to the nucleus accumbens. The findings that reward induced by food and addictive drugs involve common mechanisms raise the possibility that gut-brain hormones, which control appetite, such as amylin, could be involved in reward regulation. Amylin decreases food intake, and despite its implication in the regulation of natural rewards, tenuous evidence support amylinergic mediation of artificial rewards, such as alcohol. Therefore, the present experiments were designed to investigate the effect of salmon calcitonin (sCT), an amylin receptor agonist and analogue of endogenous amylin, on various alcohol-related behaviours in rodents. We showed that acute sCT administration attenuated the established effects of alcohol on the mesolimbic dopamine system, particularly alcohol-induced locomotor stimulation and accumbal dopamine release. Using the conditioned place preference model, we demonstrated that repeated sCT administration prevented the expression of alcohol's rewarding properties and that acute sCT administration blocked the reward-dependent memory consolidation. In addition, sCT pre-treatment attenuated alcohol intake in low alcohol-consuming rats, with a more evident decrease in high alcohol consumers in the intermittent alcohol access model. Lastly, sCT did not alter peanut butter intake, blood alcohol concentration and plasma corticosterone levels in mice. Taken together, the present data support that amylin signalling is involved in the expression of alcohol reinforcement and that amylin receptor agonists could be considered for the treatment of alcohol use disorder in humans.

A Novel Photoreactive Excipient to Probe Peptide-Matrix Interactions in Lyophilized Solids

Excipients used in lyophilized protein drug products are often selected by a trial-and-error method, in part, because the analytical methods used to detect protein-excipient interactions in lyophilized solids are limited. In this study, photolytic labeling was used to probe interactions between salmon calcitonin (sCT) and excipients in lyophilized solids. Two diazirine-derived photo-excipients, photo-leucine (pLeu) and photo-glucosamine (pGlcN), were incorporated into lyophilized solids containing sCT, together with an unlabeled excipient (sucrose or histidine) at prelyophilization pH values from 6 to 9.9. Commercially available pLeu was selected as an ionizable photo-excipient and amino acid analog, while pGlcN was synthesized as an analog of sugar-based excipients. Photolytic labeling was induced by exposing the solids to UV light (365 nm, 30-60 min), and the resulting products were identified and quantified with liquid-chromatography mass spectrometry. The distribution of photo-reaction products was affected by the photoreactive reagent used, the type of unlabeled excipient, and the solution pH before lyophilization. When other components of the solid were identical, the extent and sites of labeling on sCT were different for pGlcN and pLeu. The results suggest that ionizable and nonionizable excipients interact differently with sCT in lyophilized solids and that photo-excipients can be used to map these interactions.

Protective effects of calcitonin on IL-1 stimulated chondrocytes by regulating MMPs/TIMP-1 ratio via suppression of p50-NF-κB pathway

The aim of this study was to investigate the effects and underlying mechanisms of calcitonin (CT) on interleukin 1 beta (IL-1β) stimulated human chondrocytes. IL-1β (5 ng/mL) was added into chondrocytes to establish osteoarthritis (OA) model in vitro. Different concentrations of CT (0.1, 0.5, 1, 5, 10 and 50 nM) were used for treating IL-1β stimulated chondrocytes. Cell viability of chondrocytes was measured by cell counting kit-8 (CCK8) method. Western blotting was performed to evaluate the expression of matrix metalloproteinases (MMP-13), tissue inhibitor of metalloproteinases 1 (TIMP-1), p50 and p38. CT inhibited MMP-13 expression and promoted TIMP-1 expression in the IL-1β stimulated human chondrocytes. The CT-mediated alteration of MMP-13/TIMP-1 ratio was partially attributed to the inactivation of the p50- nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway by suppressing p50 in IL-1β stimulated chondrocytes. CT might play a protective role in IL-1β stimulated OA model via p50-NF-κB pathway.

Abbreviations: CT: calcitonin; IL-1β: interleukin-1β; MMP-13: matrix metalloproteinases-13; TIMP-1: tissue inhibitors of metalloproteinases-1.

The Activity of Peptides of the Calcitonin Family in Bone

Calcitonin was discovered over 50 yr ago as a new hormone that rapidly lowers circulating calcium levels. This effect is caused by the inhibition of calcium efflux from bone, as calcitonin is a potent inhibitor of bone resorption. Calcitonin has been in clinical use for conditions of accelerated bone turnover, including Paget's disease and osteoporosis; although in recent years, with the development of drugs that are more potent inhibitors of bone resorption, its use has declined. A number of peptides that are structurally similar to calcitonin form the calcitonin family, which currently includes calcitonin gene-related peptides (αCGRP and βCGRP), amylin, adrenomedullin, and intermedin. Apart from being structurally similar, the peptides signal through related receptors and have some overlapping biological activities, although other activities are peptide specific. In bone, in vitro studies and administration of the peptides to animals generally found inhibitory effects on osteoclasts and bone resorption and positive effects on osteoblasts and bone formation. Surprisingly, studies in genetically modified mice have demonstrated that the physiological role of calcitonin appears to be the inhibition of osteoblast activity and bone turnover, whereas amylin inhibits osteoclast activity. The review article focuses on the activities of peptides of the calcitonin family in bone and the challenges in understanding the relationship between the pharmacological effects and the physiological roles of these peptides.

Emerging hormonal-based combination pharmacotherapies for the treatment of metabolic diseases

Obesity and its comorbidities, such as type 2 diabetes mellitus and cardiovascular disease, constitute growing challenges for public health and economies globally. The available treatment options for these metabolic disorders cannot reverse the disease in most individuals and have not substantially reduced disease prevalence, which underscores the unmet need for more efficacious interventions. Neurobiological resilience to energy homeostatic perturbations, combined with the heterogeneous pathophysiology of human metabolic disorders, has limited the sustainability and efficacy of current pharmacological options. Emerging insights into the molecular origins of eating behaviour, energy expenditure, dyslipidaemia and insulin resistance suggest that coordinated targeting of multiple signalling pathways is probably necessary for sizeable improvements to reverse the progression of these diseases. Accordingly, a broad set of combinatorial approaches targeting feeding circuits, energy expenditure and glucose metabolism in concert are currently being explored and developed. Notably, several classes of peptide-based multi-agonists and peptide-small molecule conjugates with superior preclinical efficacy have emerged and are currently undergoing clinical evaluation. Here, we summarize advances over the past decade in combination pharmacotherapy for the management of obesity and type 2 diabetes mellitus, exclusively focusing on large-molecule formats (notably enteroendocrine peptides and proteins) and discuss the associated therapeutic opportunities and challenges.

Intra-articular delivery of a nanocomplex comprising salmon calcitonin, hyaluronic acid, and chitosan using an equine model of joint inflammation

Polyelectrolyte nanoparticle constructs (NPs) comprising salmon calcitonin (sCT), chitosan (CS), and hyaluronic acid (HA) were previously established as having anti-inflammatory potential when injected via the intra-articular (i.a.) route to a mouse model. We attempted to translate the formulation to a large animal model, the lipopolysaccharide (LPS)-stimulated equine model of joint inflammation. The aim was to manufacture under aseptic conditions to produce sterile pyrogen-free NPs, to confirm physicochemical characteristics, and to test toxicity and efficacy in a pilot study. NP dispersions were successfully formulated using pharmaceutical-grade source materials and were aseptically manufactured under GMP-simulated conditions in a grade A modular aseptic processing workstation. The NP formulation had no detectable pathogen or endotoxin contamination. NPs were then tested versus a lactated Ringer's solution control following single i.a. injections to the radiocarpal joints of two groups of four horses pre-treated with LPS, followed by arthrocentesis at set intervals over 1 week. There was no evidence of treatment-related toxicity over the period. While there were no differences between clinical read-outs of the NP and the control, two synovial fluid-derived biomarkers associated with cartilage turnover revealed a beneficial effect of NPs. In conclusion, NPs comprising well-known materials were manufactured for an equine i.a.-injectable pilot study and yielded no NP-attributable toxicity. Evidence of NP-associated benefit at the level of secondary endpoints was detected as a result of decreases in synovial fluid inflammatory biomarkers.

Type II Na+-phosphate Cotransporters and Phosphate Balance in Teleost Fish

Teleost fish are excellent models to study the phylogeny of the slc34 gene family, Slc34-mediated phosphate (P_i) transport and how Slc34 transporters contribute P_i homeostasis. Fish need to accumulate P_i from the diet to sustain growth. Much alike in mammals, intestinal uptake in fish is partly a paracellular and partly a Slc34-mediated transcellular process. Acute regulation of P_i balance is achieved in the kidney via a combination of Slc34-mediated secretion and/or reabsorption. A great plasticity is observed in how various species perform and combine the different processes of secretion and reabsorption. A reason for this diversity is found in one or two whole genome duplication events followed by potential gene loss; consequently, teleosts exhibit distinctly different repertoires of Slc34 transporters. Moreover, due to habitats with vastly different salinity, teleosts face the challenge of either preserving water in a hyperosmotic environment (seawater) or excreting water in hypoosmotic freshwater. An additional challenge in understanding teleost P_i homeostasis are the genome duplication and retention events that diversified peptide hormones such as parathyroid hormone and stanniocalcin. Dietary P_i and non-coding RNAs also regulate the expression of piscine Slc34 transporters. The adaptive responses of teleost Slc34 transporters to e.g. P_i diets and vitamin D are informative in the context of comparative physiology, but also relevant in applied physiology and aquaculture. In fact, P_i is essential for teleost fish growth but it also exerts significant adverse consequences if over-supplied. Thus, investigating Slc34 transporters helps tuning the physiology of commercially valuable teleost fish in a confined environment.