Parathyroid Hormone Receptor Research Articles

Non-oxidized PTH (n-oxPTH) is associated with graft loss in kidney transplant recipients

Elevated parathyroid hormone (PTH) concentrations were reported to be associated with chronic renal allograft failure. However, measurements of PTH are challenging, because PTH can occur either as non-oxidized (n-ox) or oxidized (ox) PTH. Only n-ox PTH is a PTH receptor agonist. The intact PTH (iPTH) concentrations measured routinely in clinical practice, however, equals non-oxidized PTH (n-oxPTH) plus oxidized PTH (oxPTH). In CKD patients, the majority of the circulating PTH is oxidized. We measured iPTH, oxPTH and n-oxPTH at study entry in 600 kidney transplant recipients (KTRs). They were followed for graft loss for 3 years. Graft loss was defined as need for initiation of renal replacement therapy. Thirty-eight patients had graft loss during the 3 years follow-up. OxPTH correlated very well with iPTH (R2 = 0.997, p < 0.0001), whereas the correlation between n-oxPTH and iPTH was much weaker (R2 = 0.762, p < 0.0001). Compared to KTRs without graft loss, KTRs with graft loss had significantly higher levels of iPTH, oxPTH, and n-oxPTH (p < 0.0001 in all cases). After adjusting for confounding factors in cox proportional hazards analysis, only n-oxPTH, but not oxPTH neither iPTH, was significantly associated with graft loss (Hazard ratio (HR): 1.02, 95% CI: 1.01–1.03, p = 1.84 × 10−3). The very close correlation between oxPTH and iPTH measurements suggests that conventional iPTH measurements most likely describe oxidative stress rather than PTH bioactivity. Only non-oxidized PTH but not oxidized PTH nor intact PTH is associated with graft loss in stable kidney transplant recipients.

OR07-01 Identification of the First Case of Acquired Autoimmune Parathyroid Hormone (PTH) Resistance Due to PTH1 Receptor (PTH1R) Autoantibodies

Background: Here we describe a patient who presented with symptomatic hypocalcemia and a biochemical picture suggestive of PTH resistance. PTH resistance is a hallmark of pseudohypoparathyroidism, a heterogeneous group of rare disorders caused by genetic or epigenetic alterations of PTH/PTHrP signaling. However, PTH receptor-related autoimmune etiology has not been identified as the underlying mechanism for PTH resistance. Here we describe the first case of acquired autoimmune PTH resistance that is secondary to PTH1R autoantibodies. Clinical Case: A 60-year-old African-American woman, who previously had normal calcium homeostasis, presented with acute, symptomatic hypocalcemia, hyperphosphatemia and markedly elevated serum PTH, consistent with parathyroid hormone resistance. She did not have other hormone resistance or a clinical phenotype suggestive of pseudohypoparathyroidism. Whole-exome sequencing and GNAS methylation analysis revealed no genetic or epigenetic defects of the PTH/PTHrP signaling pathway. Treatment with Calcitriol and Calcium supplements was initiated with good clinical response. Within 10 years of follow-up, the patient developed autoimmune hypothyroidism, alopecia and an unusual form of membranous glomerulonephritis, raising the suspicion for an autoimmune etiology for PTH resistance. Luciferase immunoprecipitation system assay identified antibodies against PTH1R with mapping to the N-terminal extracellular ligand-binding domain (amino acids 1- 178). Using an in vitro biological assay in GP-2.3 cells, we found that the antibodies derived from the patient’s serum blocked PTH downstream signaling via Gsalpha/cAMP/protein kinase A pathway in a concentration-dependent manner.The patient’s autoantibody profile led to the diagnosis of additional autoimmune diseases, including atrophic gastritis and Sjogren syndrome. Lymphocyte immunophenotyping using flow cytometry revealed an overall normal B and T cell profile, but with decreased frequencies and numbers of switched and non-switched memory B cell subsets and an increased frequency and number of the CD8+ naïve cell population. Genes associated with autoimmune inflammatory disorders were sequenced but no pathologic changes were detected. Conclusions: Identification of the first case of autoimmune PTH resistance secondary to PTH1R autoantibodies extends the etiologic spectrum of hypoparathyroidism and should be considered when a patient presents with findings consistent with pseudohypoparathyroidism, especially in the presence of additional autoimmune diseases.

SAT-153 PTHrP Mediated Hypercalcemia

PTHrp mediated hypercalcemiaIntroduction:PTHrp is a normal gene product, which helps tooth eruption and mammary gland development. However, PTHrp production in an adult is mostly related to solid tumor malignancy. The homology of PTHrp to PTH from the 1st to 13th amino acids decided the similar mechanism of acting at PTH-1 receptor on increasing bone resorption and calcium reabsorption at the distal renal tubule. Lung cancer is known to secrete PTHrp and PTHrp secreting hepatic cellular carcinoma (HCC) is exceedingly rare. It’s only been documented in case reports. Two cases of PTHrp secreting atypical HCC are included in this case report.Case presentation:67 year old with history of alcohol abuse with 17.8 x 8.8 cm mass in the left hepatic lobe presented with acute encephalopathy and calcium of 14.4 mg/dl. Patient was treated with zolendronic acid 4mg, IV fluid and calcitonin. Patient has a PTH level of 7 pg/ml and PTHrp level of 335 pg/ml. Bone turnover marker Beta crosslaps of 1595 pg/ml. 25-hydroxy vitD of 25 ng/ml and 1,25 dihydroxy vitD of 42 pg/ml. Liver biopsy demonstrated moderately differentiated hepatocellular carcinoma. The undifferentiated portion was positive with CD56, CAM 5.2 suggestive of neuroendocrine differentiation and epithelial lineage. Patient had negative metastatic bone scan and no pathologic fractures. Second case is a 63 year old male with NASH cirrhosis was admitted for hypercalcemia of 13.2 mg/dl. Patient was found to have metastatic atypical hepatocellular carcinoma and L4 vertebral lesion. PTHrp was 30 pg/ml and PTH 14 pg/ml. Bone turnover marker Beta crosslaps of 405 pg/ml. 25-hydroxy vitD of 48 ng/ml and 1,25 dihydroxy vitD of 9 pg/ml. Patient expired prior to biopsy.Discussion:4 cases of similar HCC were found in the literature. The treatment approach was resection of tumor, chemo or ablation. Hypercalcemia is controlled with reduction of the tumor burden and rarely by zolendronic acid alone. Both of presented cases were too advanced for surgery or chemo treatment. When tumor was not amendable for treatment, the hypercalcemia was not controllable long term. A small size study in japan administering 10mg alendronate via hepatic artery rather than IV route for patients with HCC showed enhancement of the apoptosis of HCC in addition to controlling hypercalcemia. An animal study on anti-PTHrp monoclonal murine antibody showed improved mortality of PTHrp producing pancreatic carcinoma (FA-6) in transplanted nude mice.Conclusion:Most of the patients with PTHrp mediated hypercalcemia have advance cancer that is not amendable for surgery or chemotherapy. A non-invasive treatment approach other than alendronate should be investigated to control PTHrp mediated hypercalcemia.

SAT-340 Familial Hypocalciuric Hypercalcemia Due to a C.571G&amp;gt;A (p.Glu191Lys) Variant in the GNA11 Gene

Background: Familial hypocalciuric hypercalcemia (FHH) type 1 is caused by inactivating pathogenic variants in the calcium sensing receptor (CASR) gene and clinically presents with serum hypercalcemia, low urine calcium excretion, and inappropriately normal PTH response. In a minority of patients with CASR-negative FHH (up to 26%), variants in AP2S1 are linked to FHH type 3. Similarly, inactivating pathogenic variants in the GNA11 gene have been shown to cause FHH type 2 in up to 10% of CASR and AP2S1 negative cases.1 Clinical case: A four-month old male presented to the ED for symptoms of polyphagia and polyuria. Biochemical evaluation found a serum calcium of 11.9 mg/dL (8.7-11.0 mg/dL), magnesium 2.4 mg/dL (1.6-2.3 mg/dL), 25-OH Vit D 38 ng/mL (30 -100 mg/dL) and intact PTH 27.8 pg/mL (15-65 pg/mL). His further labwork fit clinically with FHH with a urine calcium-creatinine ratio < 0.09 (<= 0.20), accompanied by a serum calcium level of 11.9 mg/dL and iCal of 1.48 mmol/L (1.13 – 1.37 mmol/L). Subsequent monitoring of serum calcium levels showed improvement with time, along with improvement in polyphagia and polyuria.Of note, mother also has a history of hypercalcemia that was diagnosed at age fifteen as part of a rheumatology evaluation. At diagnosis, her calcium was 12.1 mg/dL (9.3-10.6 mg/dL), Mg 2.3 mg/dL, phosphorous 3.3 mg/dL (2.3-4.8 mg/dL), intact PTH 39 pg/mL, and urine calcium-creatinine ratio of 0.04 (<= 0.20). She was treated with calcitonin, during which she developed hypercalciuria with elevated PTH of 88 pg/mL. A parathyroid uptake scan was concerning for adenomatous changes in the right upper parathyroid gland, but she was subsequently lost to follow-up without additional evaluation.Sequencing of the AP2S1, CASR, CDC73, CYP24A1, GCM2, GNA11, MEN1, PTH1R, or SLC34A1 genes by Next-generation sequencing methodology was completed in the patient and only revealed a maternally inherited missense variant of unknown significance of c.571G>A (p.Glu191Lys) in GNA11. This G to A transition in exon 4 substitutes a glutamic acid for a lysine at codon 191 of a highly conserved amino acid. This variant has not been previously reported in affected individuals nor has it been observed in the healthy population per the gnomAD population database. It is predicted to be deleterious/probably damaging by in silico tools (SIFT, PolyPhen2). Conclusion: To our knowledge, this is the first case demonstrating the presence of a c.571G>A (p.Glu191Lys) variant in the GNA11 gene, in a child with familial hypocalciuric hypercalcemia as well as in his affected mother. In cases with strong suspicion of FHH despite negative CASR and AP2S1 analyses, genetic analysis of GNA11 should also be considered.Reference:(1) Hovden, S., Rejnmark, L., Ladefoged, S., & Nissen, P. (2017). AP2S1 and GNA11 mutations – not a common cause of familial hypocalciuric hypercalcemia, European Journal of Endocrinology, 176(2), 177-185.

SAT-392 The Role of β-arrestin2 in Bone Catabolic Response to Hyperparathyroidism In Vivo

Primary hyperparathyroidism (PHPT) is an endocrine disorder characterized by elevated parathyroid hormone (PTH) levels and hypercalcemia caused by the overactive parathyroid glands, resulting in negative impacts on the skeleton including bone loss and increased bone fragility1. PTH binds and activates parathyroid hormone type 1 receptor (PTH1R) which primary couples to Gαs, stimulating the downstream effectors that mediate bone remodeling processes2. PTH1R activity is regulated by arrestins, specially β-arrestin2 (β-arr2), through signal termination and receptor internalization2. Previously, we have seen anabolic effects of hyperparathyroidism (cPTH) on trabecular bone in mice overexpressing Gαs3. We hypothesized that increased Gαs protein levels in osteoblasts outcompete β-arr binding to PTH1R, leading to reduced signal termination and increased bone formation. To test this hypothesis, we are testing if the deletion of β-arr2 will also result in an anabolic response to cPTH in this study. The response of β-arr2 knockout (KO) mice to cPTH have yet to be documented. The hypothesis of this study is that β-arr2 KO mice treated with cPTH will exhibit anabolic effects on the trabecular bone. Nine-week-old wild-type (WT) C57BL/6 and β-arr2 KO mice were treated for 14 days with either rPTH1-34 (80ng/g/day) or saline (PBS) using micro-osmotic pumps to simulate hyperparathyroidism. There are 8 groups (n=10 per group) including both sexes, 2 genotypes (WT and KO), and 2 treatment groups (PTH and PBS). Two 30 mg/kg doses of 0.6% calcein green were administered subcutaneously to mice at 7 and 2 days prior to euthanasia to label bones. Decalcified tibiae were embedded in paraffin for histological analysis. Undecalcified tibiae were embedded in plastic for dynamic histomorphometry. Micro-computed tomography (μCT) was used to access bone microarchitecture of femurs and vertebrae followed by biomechanical testing of bone strength. The μCT data of distal femurs show that cPTH treatment increased bone volume in female KO mice (6.864 ± 2.318 vs 4.690 ± 1.555 %; P= 0.0328; n=9 per group) and maintained bone in male KO mice (13.37 ± 2.860 vs 13.38 ± 3.135; P= 0.9968, n= 10) compared to control. Histological analysis show higher osteoclastic activity in both sexes and genotypes when treated with cPTH, suggesting that the anabolic response may be at the level of osteoblasts and osteocytes. These promising results support our hypothesis that arrestin-mediated PTH receptor downregulation plays an importance role in bone weakness associated with hyperparathyroidism. These studies are important for understanding the clinical phenotype of PHPT patients and suggest that inhibition of β-arr2 in PHPT could be a path for drug therapy.

MON-365 Novel Use of Abaloparatide to Augment Spinal Fusion in Patient Undergoing Cervicothoracic Revision Surgery

Objective To present a case of using Abaloparatide (PTHrP 1–34 analogue) to promote spinal fusion in a patient with history of cervical instability s/p multiple cervical operations with non-union. Case Presentation 66 year-old female with a history of multiple sclerosis, obesity and hypothyroidism underwent neurosurgical evaluation of neck pain. She was found to have cervical spinal stenosis causing neck pain, radiculopathy, motor deficits and ataxia. Initially underwent anterior cervical discectomy and fusion which temporarily alleviated symptoms before suffering nonunion. Subsequently underwent two additional surgeries which also eventually failed. She presented to our facility for revision corpectomy and spinal fusion. Given her history of nonunion, endocrinology was consulted for evaluation of metabolic bone disease. No known personal or family history of metabolic bones disease. No history of chronic steroid use. Initial endocrine evaluation excluded common pathologies. A decision was made to pursue anabolic osteoporosis therapy to attempt to augment the spinal fusion process. Patient started on Abaloparatide 80mcg daily 2 weeks post procedure with planned 12-week therapy course. Cervical CT at 3 and 6 months showed post-surgical cervicothoracic fusion with no signs of non-union. Discussion Abaloparatide is a 34 amino acid synthetic analogue of parathyroid hormone related peptide (PTHrP) which works by selectively activating PTH1 receptor found on osteoblasts. Currently anabolic therapies are only FDA approved for treatment of osteoporosis but there is reported off label use in cases of spinal fusions, arthroplasty and fracture healing. Studies have shown that presence of PTH and PTHrP are necessary for fracture healing. Animal studies have also shown that intermittent PTH promotes spinal fusion. This case represents a novel use for Abaloparatide to augment spinal fusion in a human clinical model. Conclusion Further studies are warranted to better understand mechanism of action, drug timing and duration for optimal treatment of anabolic therapies in bone fractures and healing. The use of anabolic therapies like Abaloparatide can be considered in patients undergoing spinal fusion surgery at high risk for non-union or undergoing revision for failed fusion.ReferencesO’Loughlin PF, Cunningham ME, Bukata SV et al. Parathyroid Hormone Augments spinal fusion, fusion mass, and fusion mass quality in a rabbit spinal fusion model. Spine 2009 January; 34: 121–130

A new neuropeptide insect parathyroid hormone iPTH in the red flour beetle Tribolium castaneum.

In the postgenomics era, comparative genomics have advanced the understanding of evolutionary processes of neuropeptidergic signaling systems. The evolutionary origin of many neuropeptidergic signaling systems can be traced date back to early metazoan evolution based on the conserved sequences. Insect parathyroid hormone receptor (iPTHR) was previously described as an ortholog of vertebrate PTHR that has a well-known function in controlling bone remodeling. However, there was no sequence homologous to PTH sequence in insect genomes, leaving the iPTHR as an orphan receptor. Here, we identified the authentic ligand insect PTH (iPTH) for the iPTHR. The taxonomic distribution of iPTHR, which is lacking in Diptera and Lepidoptera, provided a lead for identifying the authentic ligand. We found that a previously described orphan ligand known as PXXXamide (where X is any amino acid) described in the cuttlefish Sepia officinalis has a similar taxonomic distribution pattern as iPTHR. Tests of this peptide, iPTH, in functional reporter assays confirmed the interaction of the ligand-receptor pair. Study of a model beetle, Tribolium castaneum, was used to investigate the function of the iPTH signaling system by RNA interference followed by RNA sequencing and phenotyping. The results suggested that the iPTH system is likely involved in the regulation of cuticle formation that culminates with a phenotype of defects in wing exoskeleton maturation at the time of adult eclosion. Moreover, RNAi of iPTHRs also led to significant reductions in egg numbers and hatching rates after parental RNAi.

Improved GPCR ligands from nanobody tethering

Antibodies conjugated to bioactive compounds allow targeted delivery of therapeutics to cell types of choice based on that antibody’s specificity. Here we develop a new type of conjugate that consists of a nanobody and a peptidic ligand for a G protein-coupled receptor (GPCR), fused via their C-termini. We address activation of parathyroid hormone receptor-1 (PTHR1) and improve the signaling activity and specificity of otherwise poorly active N-terminal peptide fragments of PTH by conjugating them to nanobodies (VHHs) that recognize PTHR1. These C-to-C conjugates show biological activity superior to that of the parent fragment peptide in vitro. In an exploratory experiment in mice, a VHH-PTH peptide conjugate showed biological activity, whereas the corresponding free peptide did not. The lead conjugate also possesses selectivity for PTHR1 superior to that of PTH(1-34). This design approach, dubbed “conjugation of ligands and antibodies for membrane proteins” (CLAMP), can yield ligands with high potency and specificity.

Disruption of the aldehyde dehydrogenase 2 gene increases the bone anabolic response to intermittent PTH treatment in an ovariectomized mouse model.

Aldehyde dehydrogenase 2 (ALDH2) is the enzyme that oxidizes the acetaldehyde produced by alcohol metabolism. This variant not only affects the response to alcohol but is also associated with several diseases, such as esophageal cancer, myocardial infarction, and particularly osteoporosis. In our previous study, we reported that compared to wild-type (WT) mice, Aldh2 knockout (KO) mice naturally have a strong bone formation ability, and high expression of parathyroid hormone receptor (PTHR1) in osteocytes. The effect of the Aldh2 gene on bone metabolism in response to intermittent PTH treatment is unknown. The purpose of this study was to clarify the effect of the Aldh2 gene on the bone anabolic response to intermittent PTH treatment in ovariectomized mice. Female KO and WT mice were ovariectomized at 8weeks of age. At 14weeks of age, the KO and WT mice were divided into vehicle-treated (Veh) and PTH-treated (PTH) groups (i.e., the WT-Veh, WT-PTH, KO-Veh and KO-PTH groups). PTH (1-34) and vehicle were subcutaneously administered to each group at a dose of 40μg/kg body weight (BW) five times per week for 4weeks. Micro-CT showed that the bone volume (BV), trabecular number (Tb.N), connectivity density (Conn.D), and cortical thickness (Ct.Th) values in the KO-PTH mice were significantly higher than those in the KO-Veh mice. Histomorphometric analysis showed that the BV, Tb.N, and mineral apposition rate (MAR) values in the KO-PTH group were significantly higher than those in the KO-Veh group. The mRNA expression level of PTHR1 in the KO-PTH group was significantly increased and that of p21 in the KO-PTH group was significantly decreased compared with the levels in the KO-Veh group. The expression of PTHR in osteocytes from the KO-PTH group was also significantly increased compared with that in osteocytes from the KO-Veh group. Furthermore, cell cultures revealed that the ALP+CFU-f/total CFU-f percentage was significantly higher in the KO-PTH group than in the KO-Veh group. We concluded that in ovariectomized Aldh2 KO mice, the bone anabolic response to intermittent PTH treatment was significantly enhanced compared to that in WT mice, which may be mediated by the high expression level of PTHR1.

PTH and cardiovascular risk

Cardiovascular diseases remain the leading cause of non-communicable chronic diseases, are related to high morbidity and mortality and are associated to a huge impact on healthcare budgets. Biomarkers play an important role for the diagnosis and prognosis of cardiovascular diseases and are recognized tools for value-based care. Parathyroid hormone (PTH) is a major systemic calcium-regulating hormone and an important regulator of bone and mineral homeostasis. PTH 1-84, the biologically active hormone produced by the parathyroid glands and secreted into the systemic circulation, exerts its biological effects through the interaction of its first 34 amino acids with PTH receptors. PTH levels are raised in several cardio-renal disorders and hyperparathyroidism have detrimental effects on the heart and cardiac cells such as cardiac hypertrophy, remodeling and arrhythmias. High circulating PTH levels, through an increase in intracellular calcium, contribute also to the impairment of mitochondrial function and ATP production and to oxidative stress as well as inflammation states and, at the end, to cardiomyocytes necrosis. The interplay between PTH, fibroblast growth factor 23 and aldosterone is also detrimental for cardiovascular system and participate to endothelial dysfunction. Measurement of PTH levels could be therefore relevant in high risk individuals and could provide added value to established cardiac biomarkers for the sub-phenotyping of patients and treatment selection.

Different effects of Wnt/\u03b2-catenin activation and PTH activation in adult and aged male mice metaphyseal fracture healing

BackgroundFractures in older men are not uncommon and need to be healed as soon as possible to avoid related complications. Anti-osteoporotic drugs targeting Wnt/β-catenin and PTH (parathyroid hormone) to promote fracture healing have become an important direction in recent years. The study is to observe whether there is a difference in adult and aged situations by activating two signal paths.MethodsA single cortical hole with a diameter of 0.6 mm was made in the femoral metaphysis of Catnblox(ex3) mice and wild-type mice. The fracture healing effects of CA (Wnt/β-catenin activation) and PTH (activated by PTH (1–34) injections) were assessed by X-ray and CT imaging on days 7, 14, and 21 after fracture. The mRNA levels of β-catenin, PTH1R(Parathyroid hormone 1 receptor), and RUNX2(Runt-related transcription factor 2) in the fracture defect area were detected using RT-PCR. Angiogenesis and osteoblasts were observed by immunohistochemistry and osteoclasts were observed by TRAP (Tartrate-resistant Acid Phosphatase).ResultAdult CA mice and adult PTH mice showed slightly better fracture healing than adult wild-type (WT) mice, but there was no statistical difference. Aged CA mice showed better promotion of angiogenesis and osteoblasts and better fracture healing than aged PTH mice.ConclusionThe application of Wnt/β-catenin signaling pathway drugs for fracture healing in elderly patients may bring better early effects than PTH signaling pathway drugs, but the long-term effects need to be observed.

Primary cilia mediate parathyroid hormone receptor type 1 osteogenic actions in osteocytes and osteoblasts via Gli activation.

Mechanical stimulation of primary cilia in osteocytes and osteoblasts has been proposed as a mechanism that participates in bone cell survival and skeletal remodeling. Among different signaling pathways stimulated by primary cilia, the hedgehog signaling pathway has been associated with the regulation of bone development. Parathyroid hormone (PTH)-related protein (PTHrP) signaling through PTH 1 receptor (PTH1R) also regulates bone cell survival and remodeling and has been associated with the hedgehog pathway during skeletal development. We hypothesize that primary cilia and PTH1R concomitantly regulate bone remodeling and cell survival and aim to describe the mechanisms that mediate these effects in osteocytes and osteoblasts. Colocalization of PTH1R with primary cilia was observed in control and PTHrP-stimulated MLO-Y4 osteocytic and MC3T3-E1 osteoblastic cells. Activation of PTH1R by PTHrP increased cell survival, osteoblast gene expression (osteocalcin, runt-related transcription factor 2, and bone alkaline phosphatase) and the expression of the hedgehog transcription factor Gli-1 in osteocytes and osteoblasts. These effects were abrogated by small interfering RNAs for the primary cilia protein IFT88 or by a primary cilia specific inhibitor (chloral hydrate). Preincubation of MLO-Y4 osteocytic and MC3T3-E1 osteoblastic cells with the Gli-1 antagonist GANT61 inhibited PTHrP prosurvival actions but did not affect PTHrP-induced overexpression of osteogenic genes. Mechanical stimulation by fluid flow increased the number of primary cilia-presenting cells in osteocytes and osteoblasts. We propose that PTH1R activation induces prosurvival actions via primary cilia- and Gli-1-dependent mechanism and modulates osteogenic responses via a primary cilia-dependent and Gli-1-independent pathway in osteocytes and osteoblasts.

Lead Optimization and Avoidance of Reactive Metabolite Leading to PCO371, a Potent, Selective, and Orally Available Human Parathyroid Hormone Receptor 1 (hPTHR1) Agonist.

We have previously shown that the oral administration of the small molecule hPTHR1 agonist PCO371 and its lead compound, 1 (CH5447240) results in PTH-like calcemic and hypophostemic activity in thyroparathyroidectomized rats. However, 1 was converted to a reactive metabolite in a human liver microsome assay. In this article, we report on the modification path that led to an enhancement of PTHR1 agonistic activity and reduction in the formation of a reactive metabolite to result in a potent, selective, and orally active PTHR1 agonist 1-(3,5-dimethyl-4-(2-((4-oxo-2-(4-(trifluoromethoxy)phenyl)-1,3,8-triazaspiro[4.5]dec-1-en-8-yl)sulfonyl)ethyl)phenyl)-5,5-dimethylimidazolidine-2,4-dione (PCO371, 16c). This compound is currently being evaluated in a phase 1 clinical study for the treatment of hypoparathyroidism.

Parathyroid hormone receptor 1 (PTHR1) is a prognostic indicator in canine osteosarcoma

Osteosarcoma (OS) is the most common malignant primary bone tumour in humans and dogs. Several studies have established the vital role of parathyroid hormone-related protein (PTHrP) and its receptor (PTHR1) in bone formation and remodeling. In addition, these molecules play a role in the progression and metastasis of many human tumour types. This study investigated the expression of PTHR1 and PTHrP in canine OS tissues and assessed their prognostic value. Formalin-fixed, paraffin-embedded tissue samples from 50 dogs diagnosed with primary OS were immunolabeled with antibodies specific for PTHR1 and PTHrP. The immunostaining intensity of tumours from patients with OS was correlated with survival time. Both PTHR1 and PTHrP were detected in all OS samples (n = 50). Dogs with OS tumours showing high immunostaining intensity for PTHR1 (n = 36) had significantly shorter survival times (p = 0.028, Log Rank; p = 0.04, Cox regression) when compared with OS that had low immunostaining intensity for PTHR1 (n = 14).PTHrP immunostaining intensity did not correlate with survival time (p > 0.05). The results of this study indicate that increased expression of PTHR1 antigen in canine OS is associated with poor prognosis. This suggests that PTHR1 may be useful as a prognostic indicator in canine OS.

Molecular Basis for Hormone Recognition and Activation of Corticotropin-Releasing Factor Receptors.

Corticotropin-releasing factor (CRF) and the three related peptides urocortins 1-3 (UCN1-UCN3) are endocrine hormones that control the stress responses by activating CRF1R and CRF2R, two members of class B G-protein-coupled receptors (GPCRs). Here, we present two cryoelectron microscopy (cryo-EM) structures of UCN1-bound CRF1R and CRF2R with the stimulatory G protein. In both structures, UCN1 adopts a single straight helix with its N terminus dipped into the receptor transmembrane bundle. Although the peptide-binding residues in CRF1R and CRF2R are different from other members of class B GPCRs, the residues involved in receptor activation and G protein coupling are conserved. In addition, both structures reveal bound cholesterol molecules to the receptor transmembrane helices. Our structures define the basis of ligand-binding specificity in the CRF receptor-hormone system, establish a common mechanism of class B GPCR activation and G protein coupling, and provide a paradigm for studying membrane protein-lipid interactions for class B GPCRs.

Functional Analysis of PTH1R Variants Found in Primary Failure of Eruption

Although many variants of the parathyroid hormone 1 receptor (PTH1R) gene are known to be associated with primary failure of eruption (PFE), the mechanisms underlying the link remains poorly understood. We here performed functional analyses of PTH1R variants reported in PFE patients—namely, 356C>T (P119L), 395C>T (P132L), 439C>T (R147C), and 1148G>A (R383Q)—using HeLa cells with a lentiviral vector-mediated genetic modification. Two particular variants, P119L and P132L, had severe reduction in a level of N-linked glycosylation when compared with wild-type PTH1R, whereas the other 2 showed modest alteration. PTH1R having P119L or P132L showed marked decrease in the affinity to PTH1-34, which likely led to severely impaired cAMP accumulation upon stimulation in cells expressing these mutants, highlighting the importance of these 2 amino acid residues for ligand-mediated proper functioning of PTH1R. To further gain insights into PTH1R functions, we established the induced pluripotent stem cell (iPSC) lines from a patient with PFE and the heterozygous P132L mutation. When differentiated into osteoblastic-lineage cells, PFE-iPSCs showed no abnormality in mineralization. The mRNA expression of RUNX2, SP7, and BGLAP, the osteoblastic differentiation-related genes, and that of PTH1R were augmented in both PFE-iPSC-derived cells and control iPSC-derived cells in the presence of bone morphogenetic protein 2. Also, active vitamin D3 induced the expression of RANKL, a major key factor for osteoclastogenesis, equally in osteoblastic cells derived from control and PFE-iPSCs. In sharp contrast, exposure to PTH1-34 resulted in no induction of RANKL mRNA expression in the cells expressing P132L variant PTH1R, consistent with the idea that a type of heterozygous PTH1R gene mutation would spoil PTH-dependent response in osteoblasts. Collectively, this study demonstrates a link between PFE-associated genetic alteration and causative functional impairment of PTH1R, as well as a utility of iPSC-based disease modeling for future elucidation of pathogenesis in genetic disorders, including PFE.

Mangiferin suppresses human metastatic osteosarcoma cell growth by down-regulating the expression of metalloproteinases-1/2 and parathyroid hormone receptor 1

The study evaluates the protective effect of mangiferin on osteosarcoma cell proliferation and metastasis. Saos-2 and U2OS cells were treated with mangiferin (25, 50, 75 and 100 µM) for 72 h. Mangiferin reduced the cell viability, invasion, and cell adhesion and migration rate. Matrix metalloproteinases-2/9 (MMP-2/9) mRNA expression was reduced significantly, while the levels of tissue inhibitors of metalloproteinases-1/2 (TIMP-1/2) were elevated in Saos-2 and U2OS cells. Mangiferin treatment significantly reduced parathyroid hormone receptor 1 (PTHR1) mRNA and protein expression by more than 0.5-fold in both osteosarcoma cells. In addition, the immunofluorescent analysis also showed decreased PTHR1 expression following treatment with mangiferin. In summary, we have demonstrated that treatment with mangiferin reduces cell viability, proliferation, invasion, adhesion and migration, and induces apoptosis of osteosarcoma cells. Therefore, treatment with mangiferin can be effective agent in inhibiting growth and inducing apoptosis in osteosarcoma cells. Our experimental results provide evidence for the therapeutic effect of mangiferin in osteosarcoma cells.

Peptide hormone sensors using human hormone receptor-carrying nanovesicles and graphene FETs

Hormones within very low levels regulate and control the activity of specific cells and organs of the human body. Hormone imbalance can cause many diseases. Therefore, hormone detection tools have been developed, particularly over the last decade. Peptide hormones have a short half-life, so it is important to detect them within a short time. In this study, we report two types of peptide hormone sensors using human hormone receptor-carrying nanovesicles and graphene field-effect transistors (FETs). Parathyroid hormone (PTH) and glucagon (GCG) are peptide hormones present in human blood that act as ligands to G protein-coupled receptors (GPCRs). In this paper, the parathyroid hormone receptor (PTHR) and the glucagon receptor (GCGR) were expressed in human embryonic kidney-293 (HEK-293) cells, and were constructed as nanovesicles carrying the respective receptors. They were then immobilized onto graphene-based FETs. The two hormone sensors developed were able to detect each target hormone with high sensitivity (ca. 100 fM of PTH and 1 pM of GCG). Also, the sensors accurately recognized target hormones among different types of peptide hormones. In the development of hormone detection tools, this approach, using human hormone receptor-carrying nanovesicles and graphene FETs, offers the possibility of detecting very low concentrations of hormones in real-time.

Regulatory Role of RNA N6-Methyladenosine Modification in Bone Biology and Osteoporosis.

Osteoporosis is a metabolic skeletal disorder in which bone mass is depleted and bone structure is destroyed to the degree that bone becomes fragile and prone to fractures. Emerging evidence suggests that N6-methyladenosine (m6A) modification, a novel epitranscriptomic marker, has a significant role in bone development and metabolism. M6A modification not only participates in bone development, but also plays important roles as writers and erasers in the osteoporosis. M6A methyltransferase METTL3 and demethyltransferase FTO involves in the delicate process between adipogenesis differentiation and osteogenic differentiation, which is important for the pathological development of osteoporosis. Conditional knockdown of the METTL3 in bone marrow stem cells (BMSCs) could suppress PI3K-Akt signaling, limit the expression of bone formation-related genes (such as Runx2 and Osterix), restrain the expression of vascular endothelial growth factor (VEGF) and down-regulate the decreased translation efficiency of parathyroid hormone receptor-1 mRNA. Meanwhile, knockdown of the METTL3 significantly promoted the adipogenesis process and janus kinase 1 (JAK1) protein expression via an m6A-dependent way. Specifically, there was a negative correlation between METTL3 expression and porcine BMSCs adipogenesis. The evidence above suggested that the relationship between METTL3 expression and adipogenesis was inverse, and osteogenesis was positive, respectively. Similarly, FTO regulated for BMSCs fate determination during osteoporosis through the GDF11-FTO-PPARγ axis, prompting the shift of MSC lineage commitment to adipocyte and inhibiting bone formation during osteoporosis. In this systematic review, we summarize the most up-to-date evidence of m6A RNA modification in osteoporosis and highlight the potential role of m6A in prevention, treatment, and management of osteoporosis.

Insensitive to PTH of CD8+ T cells regulate bone marrow mesenchymal stromal cell in aplastic anemia patients.

Aplastic anemia (AA) is a rare disorder characterized by the suppression of bone marrow function resulting in progressive pancytopenia. The pathogenesis of AA is complex and involves an abnormal hematopoietic microenvironment, hematopoietic stem cell/progenitor cell deficiencies, and immunity disorders. However, the underlying mechanism of the disease is still not fully uncovered. In this research, we collected both donor and patient samples and found suppressed proliferation, abnormal differentiation as well as increased apoptosis of patient mesenchymal stem cells (MSCs). Considering the close relationship of parathyroid hormone (PTH) and MSCs differentiation, further studies showed that although patients maintained normal serum PTH level, their CD8+ T cells possessed lower PTH receptors. The insensitive to PTH of patients' CD8+ T cells finally lead to reduced expression of key Wnt factors. In all, bone marrow CD8+ T cells may play an important role in inducing MSCs adipogenesis and osteogenesis imbalancement.