Abaloparatide, the second generation osteoanabolic drug: Molecular mechanisms underlying its advantages over the first-in-class teriparatide

Zinc finger-inspired peptide-metal-phenolic nanointerface enhances bone-implant integration under bacterial infection microenvironment through immune modulation and osteogenesis promotion

Orthopedic and dental implantations under bacterial infection microenvironment face significant challenges in achieving high-quality bone-implant integration. Designing implant coatings that incorporate both immune defense and anti-inflammation is difficult in conventional single-functional coatings. We introduce a multifunctional nanointerface using a zinc finger-inspired peptide-metal-phenolic nanocoating, designed to enhance implant osseointegration under such conditions. Abaloparatide (ABL), a second-generation anabolic drug for treating osteoporosis, can be integrated into the design of a zinc-phenolic network constructed on the implant surface (ABL@ZnTA). Importantly, the phenolic-coordinated Zn2+ ions in ABL@ZnTA can act as zinc finger motif to co-stabilize the configuration of ABL through multiple molecular interactions, enabling high bioactivity, high loading capacity (1.36 times), and long-term release (>7 days) of ABL. Our results showed that ABL@ZnTA can modulate macrophage polarization from the pro-inflammatory M1 towards the anti-inflammatory M2 phenotype, promoting immune osteogenesis with increased OCN, ALP, and SOD 1 expression. Furthermore, the ABL@ZnTA significantly reduces inflammatory fibrous tissue encapsulation and enhances the long-term stability of the implants, indicated by enhanced binding strength (6 times) and functional connectivity (1.5-3 times) in the rat bone defect model infected by S. aureus. Overall, our research offers a nano-enabled synergistic strategy that balances infection defense and osteogenesis promotion in orthopedic and dental implantations.

FDA's stamp of approval: Unveiling peptide breakthroughs in cardiovascular diseases, ACE, HIV, CNS, and beyond

Peptides exhibit significant specificity and effective interaction with therapeutic targets, positioning themselves as key players in the global pharmaceutical market. They offer potential treatments for a wide range of diseases, including those that pose significant challenges. Notably, the peptide trofinetide (Daybue) marked a groundbreaking achievement by providing the first-ever cure for Rett syndrome, and several peptides have secured FDA approval as first-in-class medications. Furthermore, peptides are expanding their presence in areas traditionally dominated by either small or large molecules. A noteworthy example is the FDA approval of motixafortide (Aphexda) as the first peptide-based chemokine antagonist. Here, the focus will be on the analysis of FDA-approved peptides, particularly those targeting cardiovascular diseases, human immunodeficiency, central nervous system diseases, and various other intriguing classes addressing conditions such as osteoporosis, thrombocytopenia, Cushing's disease, and hypoglycemia, among others. The review will explore the chemical structures of the peptides, their indications and modes of action, the developmental trajectory, and potential adverse effects.

Systematical mutational analysis of teriparatide on anti-osteoporosis activity by alanine scanning

Osteoporosis is a progressive systemic skeletal disease that decreases bone density and bone quality, making them fragile and easy to break. In spite of effective anti-osteoporosis potency, teriparatide, the first anabolic medications approved for the treatment of osteoporosis, was proven to exhibit various side effects. And the relevant structure-activity relationship (SAR) of teriparatide was in need. In this work, we performed a systematical alanine scanning against teriparatide and synthesized 34 teriparatide derivatives. Their biological activities were evaluated and the importance of each residue for anti-osteoporosis activity was also revealed. A remarkable decrease in activity was observed for alanine replacement of the residue Gly12, His14, Ser17, Arg20 and Leu24, showcasing the important role of these residues in teriparatide on anti-osteoporosis activity. On contrary, when Gly13 and Gln30 were mutated to Ala, the peptide derivatives exhibited the significantly increased activities, demonstrating that these two residues could be readily replaced. Our research expanded the peptide library of teriparatide analogues and presented a potential opportunity for designing the more powerful anti-osteoporosis peptide agents.

The Safety and Efficacy of Abaloparatide on Postmenopausal Osteoporosis: A Systematic Review and Meta-analysis

PURPOSE

The aging of the population increases the incidence of postmenopausal osteoporosis, which threatens the health of elderly women. Abaloparatide is a synthetic peptide analogue of the human parathyroid hormone-related protein that has recently been approved for the treatment of postmenopausal osteoporosis. Its efficacy and safety have not been systematically evaluated. Therefore, studies on the efficacy and safety of abaloparatide could be of assistance in the clinical medication of postmenopausal osteoporosis. The aim of this study was to evaluate the clinical efficacy and safety of abaloparatide in postmenopausal osteoporosis.

METHODS

PubMed, Cochrane Library, EMBASE, and Web of Science databases were electronically searched from inception to July 6, 2023, for relevant randomized controlled trials. Two review authors independently conducted the study screening, quality assessment (based on the Risk of Bias Assessment Tool recommended in the Cochrane handbook), and data extraction. Outcome measures included bone mineral density (BMD), bone turnover and metabolic markers, incidence of fractures, and adverse events. Data analyses were processed by using Stata SE15.

FINDINGS

Ultimately, 8 randomized controlled trials, involving a total of 3705 postmenopausal women, were included. Meta-analysis showed that abaloparatide administration significantly increased the BMD of the lumbar vertebrae (standardized mean difference [SMD], 1.28 [95% CI, 0.81-1.76); I2 = 78.5%]), femoral neck (SMD, 0.70 [95% CI, 0.17-1.23; I2 = 75.7%]), and hip bone (SMD, 0.86 [95% CI, 0.53-1.20; I2 = 60.4%]) in postmenopausal women compared with the control group. Type I procollagen N-terminal propeptide, a bone formation marker, was also elevated after abaloparatide administration. The incidence of vertebral fracture was lower in the abaloparatide group than in the control group (risk ratio, 0.13; 95% CI, 0.06-0.26; I2 = 0%). There was no significant difference in the incidence of adverse events between the abaloparatide and the placebo groups (risk ratio, 1.03; 95% CI, 0.99-1.06; I2 = 0%).

IMPLICATIONS

Abaloparatide has a protective effect on women with postmenopausal osteoporosis. It could reduce their risk for vertebral fracture; increase their BMD of the lumbar spine, femoral neck, and hip; and alleviate symptoms and complications of postmenopausal osteoporosis with considerable safety. Limitations of this study include not searching the gray literature and not performing a subgroup analysis. PROSPERO Registration No.: CRD42022370944.

Biodegradable Nanoflowers with Abaloparatide Spatiotemporal Management of Functional Alveolar Bone Regeneration

Post-extraction alveolar bone atrophy greatly hinders the subsequent orthodontic tooth movement (OTM) or implant placement. In this study, we synthesized biodegradable bifunctional bioactive calcium phosphorus nanoflowers (NFs) loaded with abaloparatide (ABL), namely ABL@NFs, to achieve spatiotemporal management for alveolar bone regeneration. The NFs exhibited a porous hierarchical structure, high drug encapsulation efficacy, and desirable biocompatibility. ABL was initially released to recruit stem cells, followed by sustained release of Ca2+ and PO43- for in situ interface mineralization, establishing an osteogenic "biomineralized environment". ABL@NFs successfully restored morphologically and functionally active alveolar bone without affecting OTM. In conclusion, the ABL@NFs demonstrated promising outcomes for bone regeneration under orthodontic condition, which might provide a desirable reference of man-made "bone powder" in the hard tissue regeneration field.

Mesoporous silica nanoparticles: An emerging approach in overcoming the challenges with oral delivery of proteins and peptides

Proteins and peptides (PPs), as therapeutics are widely explored in the past few decades, by virtue of their inherent advantages like high specificity and biocompatibility with minimal side effects. However, owing to their macromolecular size, poor membrane permeability, and high enzymatic susceptibility, the effective delivery of PPs is often challenging. Moreover, their subjection to varying environmental conditions, when administered orally, results in PPs denaturation and structural conformation, thereby lowering their bioavailability. Hence, for effective delivery with enhanced bioavailability, protection of PPs using nanoparticle-based delivery system has gained a growing interest. Mesoporous silica nanoparticles (MSNs), with their tailored morphology and pore size, high surface area, easy surface modification, versatile loading capacity, excellent thermal stability, and good biocompatibility, are eligible candidates for the effective delivery of macromolecules to the target site. This review highlights the different barriers hindering the oral absorption of PPs and the various strategies available to overcome them. In addition, the potential benefits of MSNs, along with their diversifying role in controlling the loading of PPs and their release under the influence of specific stimuli, are also discussed in length. Further, the tuning of MSNs for enhanced gene transfection efficacy is also highlighted. Since extensive research is ongoing in this area, this review is concluded with an emphasis on the potential risks of MSNs that need to be addressed prior to their clinical translation.

Pharmaceutical treatment of bone loss: From animal models and drug development to future treatment strategies

Animal models are fundamental to advance our knowledge of the underlying pathophysiology of bone loss and to study pharmaceutical countermeasures against it. The animal model of post-menopausal osteoporosis from ovariectomy is the most widely used preclinical approach to study skeletal deterioration. However, several other animal models exist, each with unique characteristics such as bone loss from disuse, lactation, glucocorticoid excess, or exposure to hypobaric hypoxia. The present review aimed to provide a comprehensive overview of these animal models to emphasize the importance and significance of investigating bone loss and pharmaceutical countermeasures from perspectives other than post-menopausal osteoporosis only. Hence, the pathophysiology and underlying cellular mechanisms involved in the various types of bone loss are different, and this might influence which prevention and treatment strategies are the most effective. In addition, the review sought to map the current landscape of pharmaceutical countermeasures against osteoporosis with an emphasis on how drug development has changed from being driven by clinical observations and enhancement or repurposing of existing drugs to today's use of targeted anti-bodies that are the result of advanced insights into the underlying molecular mechanisms of bone formation and resorption. Moreover, new treatment combinations or repurposing opportunities of already approved drugs with a focus on dabigatran, parathyroid hormone and abaloparatide, growth hormone, inhibitors of the activin signaling pathway, acetazolamide, zoledronate, and romosozumab are discussed. Despite the considerable progress in drug development, there is still a clear need to improve treatment strategies and develop new pharmaceuticals against various types of osteoporosis. The review also highlights that new treatment indications should be explored using multiple animal models of bone loss in order to ensure a broad representation of different types of skeletal deterioration instead of mainly focusing on primary osteoporosis from post-menopausal estrogen deficiency.

Strategies to improve the physicochemical properties of peptide-based drugs

Peptides are a rapid-growing class of therapeutics with unique and desirable physicochemical properties. Due to disadvantages such as low membrane permeability and susceptibility to proteolytic degradation, peptide-based drugs have limited bioavailability, a short half-life, and rapid in vivo elimination. Various strategies can be applied to improve the physicochemical properties of peptide-based drugs to overcome limitations such as limited tissue residence time, metabolic instability, and low permeability. Applied strategies including backbone modifications, side chain modifications, conjugation with polymers, modification of peptide termini, fusion to albumin, conjugation with the Fc portion of antibodies, cyclization, stapled peptides, pseudopeptides, cell-penetrating peptide conjugates, conjugation with lipids, and encapsulation in nanocarriers are discussed.

Is abaloparatide more efficacious on increasing bone mineral density than teriparatide for women with postmenopausal osteoporosis? An updated meta-analysis

PURPOSE

Osteoporosis poses a challenge to public health, causing fragility fractures, especially in postmenopausal women. Abaloparatide (ABL) is an effective anabolic agent to improve bone formation and resorption among postmenopausal women with osteoporosis. Our meta-analysis aims to assess the effectiveness and safety of ABL versus teriparatide (TPTD) in improving bone mineral density (BMD).

METHODS

We searched Medline, Embase, Web of Science, Cochrane databases and Clinicaltrial.gov until September 2, 2022. We included data from randomized controlled trials (RCTs) and post hoc analyses of RCTs. Outcomes included BMD change from baseline and risks of adverse events. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) tool was used to evaluate the quality of outcomes.

RESULTS

Four studies including 16 subgroups were included in this study. In particular, RCTs with head-to-head comparisons of ABL and TPTD were used in the meta-analysis, and all were from manufacturer-sponsored trials. All parameters in 24 weeks except lumbar spine (versus TPTD) showed significant advantages in the ABL group. Only the results of two subgroups in ABL versus TPTD demonstrated High GRADE quality (femoral neck: weighted mean difference (WMD) = 1.58 [0.52, 2.63]; Total hip: WMD = 1.46 [0.59, 2.32]). However, our fracture data were insufficient. Besides, we found no evident difference in serious adverse events or deaths in either group and the incidence of hypercalcemia in the ABL group lessened by 51% compared with the TPTD group. Nevertheless, compared with placebo, ABL demonstrated higher risks of nausea and palpitations.

CONCLUSION

ABL demonstrated a beneficial effect on BMD compared to both placebo and TPTD for postmenopausal women with osteoporosis. ABL also had insignificantly lowered adverse event risk than TPTD. ABL is an alternative for patients with postmenopausal osteoporosis.

Abaloparatide outperforms teriparatide in protecting against alveolar bone loss in experimental periodontitis

BACKGROUND

The aim of this study was to compare the effects of two osteoanabolic drugs, abaloparatide (ABL) and teriparatide (TPTD), on protecting alveolar bone in experimental periodontitis.

METHODS

Twenty-four 9-week-old, male, Sprague-Dawley rats were placed with silk suture around the right maxillary second molar, and then were randomly divided into three groups, that is, the ABL, TPTD, and saline group, receiving intermittent subcutaneous injections of ABL (80 μg/kg), TPTD (80 μg/kg) or saline respectively every other day for 4 weeks. Samples on both sides were assessed through micro-computerized tomography, histological, and immunohistochemical analysis. Mouse pre-osteoblast MC3T3 cell was cultured with lipopolysaccharide (LPS) and treated with ABL or TPTD, before assays of cell proliferation, alkaline phosphatase (ALP) activity and real-time polymerase chain reaction.

RESULTS

On the ligature side, both ABL and TPTD significantly reduced alveolar bone loss, and ABL had significantly better effects with higher expression of runt-related transcription factor 2 (RUNX2) and Bglap (formerly called osteocalcin); meanwhile, the ligature induced osteoclastogenesis and down-regulation of osteoprotegerin (OPG) was affected by neither drug. On the non-ligature side, ABL also showed better osteoanabolic effects. In vitro studies revealed that, in the presence of LPS, ABL, and TPTD similarly promoted MC3T3 proliferation, whereas ABL induced higher ALP activity and osteoblastic gene expression compared to TPTD.

CONCLUSION

Both ABL and TPTD protect and regenerate alveolar bone in experimental periodontitis, and ABL behaves even better than TPTD at the same dose, attributed to its stronger osteoanabolic effects in this context.

A standardized extract of Coleus forskohlii root protects rats from ovariectomy-induced loss of bone mass and strength, and impaired bone material by osteogenic and anti-resorptive mechanisms

INTRODUCTION

In obese humans, Coleus forskohlii root extract (CF) protects against weight gain owing to the presence of forskolin, an adenylate cyclase (AC) activator. As AC increases intracellular cyclic adenosine monophosphate (cAMP) levels in osteoblasts that has an osteogenic effect, we thus tested the skeletal effects of a standardized CF (CFE) in rats.

METHODS

Concentrations of forskolin and isoforskolin were measured in CFE by HPLC. CFE and forskolin (the most abundant compound present in CFE) were studied for their osteogenic efficacy in vitro by alkaline phosphatase (ALP), cAMP and cyclic guanosine monophosphate (cGMP) assays. Femur osteotomy model was used to determine the osteogenic dose of CFE. In growing rats, CFE was tested for its osteogenic effect in intact bone. In adult ovariectomized (OVX) rats, we assessed the effect of CFE on bone mass, strength and material. The effect of forskolin was assessed in vivo by measuring the expression of osteogenic genes in the calvarium of rat pups.

RESULTS

Forskolin content in CFE was 20.969%. CFE increased osteoblast differentiation and intracellular cAMP and cGMP levels in rat calvarial osteoblasts. At 25 mg/kg (half of human equivalent dose), CFE significantly enhanced calcein deposition at the osteotomy site. In growing rats, CFE promoted modeling-directed bone formation. In OVX rats, CFE maintained bone mass and microarchitecture to the level of sham-operated rats. Moreover, surface-referent bone formation in CFE treated rats was significantly increased over the OVX group and was comparable with the sham group. CFE also increased the pro-collagen type-I N-terminal propeptide: cross-linked C-telopeptide of type-I collagen (PINP : CTX-1) ratio over the OVX rats, and maintained it to the sham level. CFE treatment decreased the OVX-induced increases in the carbonate-to-phosphate, and carbonate-to-amide-I ratios. CFE also prevented the OVX-mediated decrease in mineral crystallinity. Nanoindentation parameters, including modulus and hardness, were decreased by OVX but CFE maintained these to the sham levels. Forskolin stimulated ALP, cAMP and cGMP in vitro and upregulated osteogenic genes in vivo.

CONCLUSION

CFE, likely due to the presence of forskolin displayed a bone-conserving effect via osteogenic and anti-resorptive mechanisms resulting in the maintenance of bone mass, microarchitecture, material, and strength.

Abaloparatide and teriparatide enhance mandibular growth in adolescent rats with site-specific and mechano-related effects

OBJECTIVE

Teriparatide (TPTD) and abaloparatide (ABL) are two osteoanabolic drugs targeting parathyroid hormone (PTH)1R signalling. This study aimed to investigate the effects of TPTD and ABL on the adolescent mandibular growth.

METHOD

In total, 70 4-week-old male Sprague-Dawley rats were randomly divided into 14 groups, treated with intermittent TPDT or ABL at various doses, accompanied by mandibular advancement (MA) or not. 3D printing was used to fabricate an innovative splint for MA. After a 4-week treatment, morphological measurement, histological and immunohistochemical analysis were performed. Mandibular condylar chondrocytes (MCCs) were treated with TPTD or ABL, followed by CCK-8 assay, alcian blue staining, real time-PCR and immunofluorescent staining.

RESULT

In vivo, TPTD or ABL alone increased the condylar length and cartilage thickness, with up-regulated SOX9 and COL II, whilst down-regulated COL X; however, when combined with MA, the promotive effects were attenuated. TPTD or ABL alone increased the mandibular body height and mandibular angle width, whilst increased the mandibular body length and alveolar bone width when combined with MA. In vitro, TPTD or ABL enhanced the MCC proliferation, glycosaminoglycan synthesis, COL II and SOX9 expression, whilst down-regulated COL X, Ihh and PTH1R expression.

CONCLUSION

Both ABL and TPTD enhance mandibular growth in adolescent rats with site-specific and mechano-related effects, including propelling chondrogenesis at the condylar cartilage and promoting bone apposition at other mechano-responsive sites. They behave as promising drugs for mandibular growth modification, and in general ABL seems more potent than TPTD in this context.

Advancement in the Treatment of Osteoporosis and the Effects on Bone Healing

Osteoporosis (OP) is a major global health concern, with aging being one of the most important risk factors. Osteoarthritis (OA) is also an age-related disorder. Patients with OP and/or OA may be treated surgically for fractures or when their quality of life is impaired. Poor bone quality due to OP can seriously complicate the stability of a bone fixation construct and/or surgical fracture treatment. This review summarizes the current knowledge on the pathophysiology of normal and osteoporotic bone healing, the effect of a bone fracture on bone turnover markers, the diagnosis of a low bone mineral density (BMD) before surgical intervention, and the effect of available anti-osteoporosis treatment. Interventions that improve bone health may enhance the probability of favorable surgical outcomes. Fracture healing and the treatment of atypical femoral fractures are also discussed.

Molecular insights into the distinct signaling duration for the peptide-induced PTH1R activation

The parathyroid hormone type 1 receptor (PTH1R), a class B1 G protein-coupled receptor, plays critical roles in bone turnover and Ca²⁺ homeostasis. Teriparatide (PTH) and Abaloparatide (ABL) are terms as long-acting and short-acting peptide, respectively, regarding their marked duration distinctions of the downstream signaling. However, the mechanistic details remain obscure. Here, we report the cryo-electron microscopy structures of PTH- and ABL-bound PTH1R-Gs complexes, adapting similar overall conformations yet with notable differences in the receptor ECD regions and the peptide C-terminal portions. 3D variability analysis and site-directed mutagenesis studies uncovered that PTH-bound PTH1R-Gs complexes display less motions and are more tolerant of mutations in affecting the receptor signaling than ABL-bound complexes. Furthermore, we combined the structural analysis and signaling assays to delineate the molecular basis of the differential signaling durations induced by these peptides. Our study deepens the mechanistic understanding of ligand-mediated prolonged or transient signaling.

Assessment of the Therapeutic Potential of Melatonin for the Treatment of Osteoporosis Through a Narrative Review of Its Signaling and Preclinical and Clinical Studies

Melatonin is a bioamine produced primarily in the pineal gland, although peripheral sites, including the gut, may also be its minor source. Melatonin regulates various functions, including circadian rhythm, reproduction, temperature regulation, immune system, cardiovascular system, energy metabolism, and bone metabolism. Studies on cultured bone cells, preclinical disease models of bone loss, and clinical trials suggest favorable modulation of bone metabolism by melatonin. This narrative review gives a comprehensive account of the current understanding of melatonin at the cell/molecular to the systems levels. Melatonin predominantly acts through its cognate receptors, of which melatonin receptor 2 (MT2R) is expressed in mesenchymal stem cells (MSCs), osteoblasts (bone-forming), and osteoclasts (bone-resorbing). Melatonin favors the osteoblastic fate of MSCs, stimulates osteoblast survival and differentiation, and inhibits osteoclastogenic differentiation of hematopoietic stem cells. Produced from osteoblastic cells, osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B ligand (RANKL) critically regulate osteoclastogenesis and melatonin by suppressing the osteoclastogenic RANKL, and upregulating the anti-osteoclastogenic OPG exerts a strong anti-resorptive effect. Although the anti-inflammatory role of melatonin favors osteogenic function and antagonizes the osteoclastogenic function with the participation of SIRT signaling, various miRNAs also mediate the effects of the hormone on bone cells. In rodent models of osteoporosis, melatonin has been unequivocally shown to have an anti-osteoporotic effect. Several clinical trials indicate the bone mass conserving effect of melatonin in aging/postmenopausal osteoporosis. This review aims to determine the possibility of melatonin as a novel class of anti-osteoporosis therapy through the critical assessment of the available literature.

Therapeutic peptides: current applications and future directions

Peptide drug development has made great progress in the last decade thanks to new production, modification, and analytic technologies. Peptides have been produced and modified using both chemical and biological methods, together with novel design and delivery strategies, which have helped to overcome the inherent drawbacks of peptides and have allowed the continued advancement of this field. A wide variety of natural and modified peptides have been obtained and studied, covering multiple therapeutic areas. This review summarizes the efforts and achievements in peptide drug discovery, production, and modification, and their current applications. We also discuss the value and challenges associated with future developments in therapeutic peptides.

Histochemical characteristics on minimodeling-based bone formation induced by anabolic drugs for osteoporotic treatment

Modeling, the changes of bone size and shape, often takes place at the developmental stages, whereas bone remodeling-replacing old bone with new bone-predominantly occurs in adults. Unlike bone remodeling, bone formation induced by modeling i.e., minimodeling (microscopic modeling in cancellous bone) is independent of osteoclastic bone resorption. Although recently-developed drugs for osteoporotic treatment could induce minimodeling-based bone formation in addition to remodeling-based bone formation, few reports have demonstrated the histological aspects of minimodeling-based bone formation. After administration of eldecalcitol or romosozumab, unlike teriparatide treatment, mature osteoblasts formed new bone by minimodeling, without developing thick preosteoblastic layers. The histological characteristics of minimodeling-based bone formation is quite different from remodeling, as it is not related to osteoclastic bone resorption, resulting in convex-shaped new bone and smooth cement lines called arrest lines. In this review, we will show histological properties of minimodeling-based bone formation by osteoporotic drugs.

Synthesis and Evaluation of Galloyl Conjugates of Flavanones as BMP-2 Upregulators with Promising Bone Anabolic and Fracture Healing Properties

The molecular hybridization concept led us to design a series of galloyl conjugates of flavanones that have potent osteoblast differentiation ability in vitro and promote bone formation in vivo. An array of in vitro studies, especially gene expression of osteogenic markers, evinced compound 5e as the most potent bone anabolic agent, found to be active at 1 pM, which was then further assessed for its osteogenic potential in vivo. From in vivo studies on rat calvaria and a fracture defect model, we inferred that compound 5e, at an oral dose of 5 mg/(kg day), increased the expression of osteogenic genes (RUNX2, BMP-2, Col1, and OCN) and the bone formation rate and significantly promoted bone regeneration at the fracture site, as evidenced by the increased bone volume/tissue fraction compared with vehicle-treated rats. Furthermore, structure-activity relationship studies and pharmacokinetic studies suggest 5e as a potential bone anabolic lead for future osteoporosis drug development.

Production and identification of peptides with activity promoting osteoblast proliferation from meat dregs of Pinctada martensii

As a by-product of pearl production, Pinctada martensii meat dregs have a high level of protein but cannot be fully utilized. In this study, P. martensii meat dregs were first hydrolyzed by three pepsin enzymes, resulting in neutral proteinase enzymatic hydrolysate that had a higher effect on stimulating the proliferation of MC3T3-E1 cells, and cell proliferation increases of 37.37 ± 0.03%. Subsequently, after purification of alcohol precipitation, ultrafiltration, and Superdex G-25 gel chromatography, five fractions were further separated and purified in which fraction ZP2 could effectively improve cell proliferation induced an increase of 43.95 ± 0.03% in MC3T3-E1 cells growth. Consequently, with the help of alkaline phosphatase and methyl thiazolyl tetrazolium assay, five novel peptides (FDNEGKGKLPEEY, FWDGRDGEVDGFK, VLQTDNDALGKAK, IVLDSGDGVTH, and MVAPEEHP) derived from fraction ZP2 with the strongest osteogenic activity were screened, and their sequences were identified using Orbitrap Fusion Lumos Tribrid Orbital liquid chromatography-mass spectrometry. Therefore, the research results demonstrated that P. martensii meat could be used as a promising material for producing food additives for improving osteoporosis. PRACTICAL APPLICATIONS: In this study, after enzymolysis and purification, the fraction ZP2, derived from Pinctada martensii meat dregs were found to have a better activity of promoting osteoblast proliferation, showing the higher osteogenic activity with an increase of 43.95 ± 0.03% in terms of cell proliferation. It is beneficial to realize the high value and resource utilization of P. martensii meat dregs as a by-product of pearl production. The research demonstrated that the meat dregs of P. martensii could be used as an attractive material for producing active peptides in functional foods. In addition, the molecular weight of the peptides we identified from the ZP2 fraction is suitable for the proliferation of MC3T3-E1 cells, which lays a foundation for the further synthesis of peptides that promote the high proliferation activity of osteocytes.

Parathyroid hormone and its related peptides in bone metabolism

Parathyroid hormone (PTH) is an 84-amino-acid peptide hormone that is secreted by the parathyroid gland. It has different administration modes in bone tissue through which it promotes bone formation (intermittent administration) and bone resorption (continuous administration) and has great potential for application in sbone defect repair. PTH regulates bone metabolism by binding to PTH1R. PTH plays an osteogenic role by acting directly on mesenchymal stem cells, cells with an osteoblastic lineage, osteocytes, and T cells. It also participates as an osteoclast by indirectly acting on osteoclast precursor cells and osteoclasts and directly acting on T cells. In these cells, PTH activates the Wnt signaling, cAMP/PKA, cAMP/PKC, and RANKL/RANK/OPG pathways and other signaling pathways. Although PTH(1-34), also known as teriparatide, has been used clinically, it still has some disadvantages. Developing improved PTH-related peptides is a potential solution to teriparatide's shortcomings. The action mechanism of these PTH-related peptides is not exactly the same as that of PTH. Thus, the mechanisms of PTH and PTH-related peptides in bone metabolism were reviewed in this paper.

Therapeutic potential of phosphodiesterase inhibitors in the treatment of osteoporosis: Scopes for therapeutic repurposing and discovery of new oral osteoanabolic drugs

Cyclic nucleotide phosphodiesterases (PDEs) are ubiquitously expressed enzymes that hydrolyze phosphodiester bond in the second messenger molecules including cAMP and cGMP. A wide range of drugs blocks one or more PDEs thereby preventing the inactivation of cAMP/cGMP. PDEs are differentially expressed in bone cells including osteoblasts, osteoclasts and chondrocytes. Intracellular increases in cAMP/cGMP levels in osteoblasts result in osteogenic response. Acting via the type 1 PTH receptor, teriparatide and abaloparatide increase intracellular cAMP and induce osteoanabolic effect, and many PDE inhibitors mimic this effect in preclinical studies. Since all osteoanabolic drugs are injectable and that oral drugs are considered to improve the treatment adherence and persistence, osteogenic PDE inhibitors could be a promising alternative to the currently available osteogenic therapies and directly assessed clinically in drug repurposing mode. Similar to teriparatide/abaloparatide, PDE inhibitors while stimulating osteoblast function also promote osteoclast function through stimulation of receptor activator of nuclear factor kappa-B ligand production from osteoblasts. In this review, we critically discussed the effects of PDE inhibitors in bone cells from cellular signalling to a variety of preclinical models that evaluated the bone formation mechanisms. We identified pentoxifylline (a non-selective PDE inhibitor) and rolipram (a PDE4 selective inhibitor) being the most studied inhibitors with osteogenic effect in preclinical models of bone loss at ≤ human equivalent doses, which suggest their potential for post-menopausal osteoporosis treatment through therapeutic repurposing. Subsequently, we treated pentoxifylline and rolipram as prototypical osteogenic PDEs to predict new chemotypes via the computer-aided design strategies for new drugs, based on the structural biology of PDEs.

A prebiotic, short-chain fructo-oligosaccharides promotes peak bone mass and maintains bone mass in ovariectomized rats by an osteogenic mechanism

In preclinical studies, fructooligosaccharide (FOS) showed beneficial skeletal effects but its effect on peak bone mass (PBM) and bone loss caused by estrogen (E2) deficiency has not been studied, and we set out to study these effects in rats. Short-chain (sc)-FOS had no effect on body weight, body composition, and energy metabolism of ovary intact (sham) and ovariectomized (OVX) rats. scFOS did not affect serum and urinary calcium and phosphorus levels, and on calcium absorption, although an increasing trend was noted in the sham group. Sham and OVX rats given scFOS had better skeletal parameters than their respective controls. scFOS treatment resulted in a higher bone anabolic response but had no effect on the catabolic parameters. scFOS increased serum levels of a short-chain fatty acid, butyrate which is known to have osteogenic effect. Our study for the first time demonstrates that in rats scFOS at the human equivalent dose enhances PBM and protects against E2 deficiency-induced bone loss by selective enhancement of new bone formation, and implicates butyrate in this process.

Abaloparatide and the Spine: A Narrative Review

Osteoporosis is a common and debilitating condition characterized by diminished bone mass and architecture leading to bone fragility. Antiresorptive medicines like bisphosphonates (and less commonly denosumab) are the typical first-line agents for the medical treatment of osteoporosis. However, newer anabolic agents have been shown to improve bone mass and architecture, as well as reduce fracture risk, to a greater degree than traditional antiresorptive therapies. Teriparatide (human recombinant parathyroid hormone (PTH) 1–34, Forteo, Ely Lilly, Indianapolis, IN), which was the first in class to be approved in the United States, is the most widely used anabolic osteoporosis medicine and has shown significant benefit over traditional antiresorptive therapies. However, abaloparatide (synthetic parathyroid-related peptide (PTHrP), Tymlos, Radius Health, Waltham, MA), the second drug in this family, has recently become available for use. In this narrative review, we review the mechanism, effects, and benefits of abaloparatide compared to alternative treatments as well as discuss the current literature in regard to its effect on osteoporosis-related complications in the spine.

Structural insights into emergent signaling modes of G protein-coupled receptors

G protein-coupled receptors (GPCRs) represent the largest family of cell membrane proteins, with >800 GPCRs in humans alone, and recognize highly diverse ligands, ranging from photons to large protein molecules. Very important to human medicine, GPCRs are targeted by about 35% of prescription drugs. GPCRs are characterized by a seven-transmembrane α-helical structure, transmitting extracellular signals into cells to regulate major physiological processes via heterotrimeric G proteins and β-arrestins. Initially viewed as receptors whose signaling via G proteins is delimited to the plasma membrane, it is now recognized that GPCRs signal also at various intracellular locations, and the mechanisms and (patho)physiological relevance of such signaling modes are actively investigated. The propensity of GPCRs to adopt different signaling modes is largely encoded in the structural plasticity of the receptors themselves and of their signaling complexes. Here, we review emerging modes of GPCR signaling via endosomal membranes and the physiological implications of such signaling modes. We further summarize recent structural insights into mechanisms of GPCR activation and signaling. We particularly emphasize the structural mechanisms governing the continued GPCR signaling from endosomes and the structural aspects of the GPCR resensitization mechanism and discuss the recently uncovered and important roles of lipids in these processes.