Increased Bone Loss Research Articles

Sclerostin and OPG/RANK-L system take part in bone remodeling in patients with acromegaly

IntroductionAcromegaly is a disease characterized by enhanced bone turnover with persistently high vertebral fracture risk. Sclerostin is a glycoprotein, which acts as an inhibitor of bone formation and activates osteoclast-mediated bone resorption. The osteoprotegerin (OPG)/receptor activator for the nuclear factor κ B ligand (RANK-L) system is crucial for controlling bone metabolism.ObjectiveThe study aimed primarily at evaluating sclerostin, OPG, and RANK-L concentrations in patients at different stages of acromegaly activity. The secondary aim was to identify an association of sclerostin with the OPG/RANK-L system and bone mineral density (BMD).Materials and methodsThe study enrolled 126 patients aged 40 to 80 years, including 72 patients with acromegaly and 54 controls (CG). The acromegaly patients were further classified into the following subgroups: active acromegaly (AA), controlled acromegaly (CTA), and cured acromegaly (CA). Blood samples were taken from the participants to measure sclerostin, OPG, RANK-L, growth hormone (GH), and insulin-like growth factor-1 (IGF-1). Dual-energy X-ray absorptiometry was performed at the lumbar spine and hip.ResultsSignificantly lower sclerostin concentrations were observed in acromegaly patients compared with CG (AA, CTA, CA, CTA+CA, AA+CTA+CA vs CG; p < 0.001). Significant differences in OPG concentrations were revealed between the following groups: CTA vs CA (p=0.002), CTA vs CG (p<0.001), CTA+CA vs. CG (p<0.001), and AA+CTA+CA vs. CG (p<0.001). There were no significant differences in RANK-L concentrations between studied groups, regardless of the adopted classification (p>0.05). There were no statistically significant correlations between sclerostin and GH/IGF-1 or BMD. In the AA+CTA+CA group, there was a statistically significant positive correlation between SCL and OPG concentrations (r=0.271; p=0.022). A significant negative correlation between SCL and RANK-L was found in the AA group (r=-0.738; p=0.046).ConclusionsPatients with acromegaly have lower sclerostin concentrations than healthy controls, which may be a result of a compensatory mechanism to increased bone loss. The influence of the GH/IGF-I axis on bone remodeling may be mediated in part by the OPG/RANK-L system. The interaction between SCL and OPG/RANK-L system in acromegaly should be further elucidated.

Association between dietary vitamin E and osteoporosis in older adults in the United States.

Increased oxidative stress due to aging can lead to increased bone loss. The most abundant form of vitamin E, namely α-tocopherol, has high antioxidant properties and biological activity; however, its effect on osteoporosis has not been well studied in humans. We aimed to investigate the association between dietary vitamin E (α-tocopherol) and osteoporosis among older adults in the United States. This cross-sectional study analyzed data on older adults in the United States aged ≥50 years from the 2007-2010, 2013-2014 and 2017-2020 pre-pandemic cycles of the National Health and Nutrition Examination Survey. Sample-weighted multivariate regression models were used, with adjustments for relevant confounders. This study comprised 5,800 individuals with available data on dietary intake and bone mineral density of hip and spine. The mean participant age was 61.4 (standard deviation, 8.7) years, and approximately 9.9% had osteoporosis. High vitamin E intake was significantly associated with a reduced risk of osteoporosis (odds ratio, 0.96, 95% confidence interval, 0.93-0.98). In addition, there was evidence of interaction between dietary vitamin E and prior fracture on preventing osteoporosis. Our study indicated a linear association between dietary vitamin E levels and osteoporosis in an older population in the United States. Further research is required to explore the potential effects of different forms of vitamin E on osteoporosis.

Why is it necessary to screen for periodontal disease in diabetic patients?

Periodontal diseases include gingivitis (inflammation of gingiva caused by the bacterial biofilm) and periodontitis involving loss of the supporting structures around the teeth, respectively cementum, periodontal ligament and alveolar bone. Diabetes increases the risk of periodontal diseases; the plausible mechanisms are: alterations in the immunoinflammatory response of bacteria, increased bone loss, the decrease in matrix-producing cells to maintain the periodontium, microvascular changes and alteration in collagen synthesis and metabolism. Treatment of periodontitis influence glycemic control in diabetic patients and intervention trial suggests that this can generate a reduction of circulating inflammatory markers and improves metabolic control in diabetic patients. International forums recommend oral examination as a component of medical care for diabetic patients. Our review summarizes current information on the association of diabetes with periodontal disease.

Risperidone accelerates bone loss in mice models of schizophrenia by inhibiting osteoblast autophagy

BackgroundRisperidone (RIS) is the first-line drug in the clinical treatment of schizophrenia, and long-term use may lead to bone loss and even osteoporosis. This study investigated whether the mechanism of RIS-induced bone loss is related to autophagy. MethodsThe schizophrenia mice were established with the administration of MK-801. Then, RIS were injected, or autophagy inducer rapamycin (RAPA) co-injected for 8 weeks. Cognitive performance was determined by the novel object recognition and Open field tests. Bone loss of schizophrenia mice were assessed using microCT, H&E staining, ALP staining, ARS staining and WB, respectively. Autophagy of schizophrenia mice were detected by immunofluorescence, transmission electron microscopy (TEM) and WB, respectively. In addition, osteogenic differentiation of MC3T3-E1 and BMSCs cells were assessed using H&E staining, ALP staining, ARS staining and WB, respectively. ResultsIn the present study, we found that RIS treatment can promote bone loss in schizophrenia mice and inhibit osteogenic differentiation of MC3T3-E1 and BMSCs cells. Interesting, the number of autophagosome and autophagy-related protein expression were decreased after RIS treatment. However, the bone loss and inhibition of osteogenic differentiation induced by RIS in schizophrenia mice were reversed by autophagy inducer RAPA. ConclusionRIS significantly increased bone loss and inhibited osteogenic differentiation in schizophrenia mice; the underlying mechanism entails suppressing osteoblast autophagy.

Preventing Iatrogenic Fibula Fractures Using the Push-Pull Technique: A Biomechanical Comparison of Unicortical Versus Bicortical Post Screws.

Displaced diaphyseal fractures can be reduced using the push-pull technique, wherein a plate is affixed to the distal fragment of the fracture, a post screw is placed proximal to the plate, and a lamina spreader creates distraction. This study evaluated the load to failure and mechanism of failure of bicortical and unicortical post screws during reduction. Four matched pairs of cadaver legs were subjected to a 2-cm oblique osteotomy simulating a displaced, oblique diaphyseal fracture. A 6-hole compression plate was affixed to the distal fragment with 2 unicortical locking screws, and a 12-mm unicortical or 20-mm bicortical screw was inserted as a post screw proximal to the plate. A lamina bone spreader was used to exert a distraction force between the plate and the post screw. A mechanical actuator simulated the distraction procedure until failure. Maximum applied load, displacement, and absorbed energy were recorded and compared across unicortical and bicortical groups by paired t tests. At maximum load, we found statistically significant differences in displacement (P=.003) and energy absorbed (P=.022) between the two groups. All unicortical screws failed through screw toggle and bone cut-out. Bicortical screws failed through bending, with no visible damage to the bone at the screw site. When diaphyseal fractures are significantly shortened and require a greater distraction force to achieve reduction, bicortical screws demonstrate a higher mechanical load to failure and increased bone loss from the screw-removal site. A unicortical post screw may be used if minimal distraction is needed. [Orthopedics. 2024;47(5):308-312.].

Gonadotropic Axis, Bone Mass, and Sarcopenia Assessment After Autologous Hematopoietic Stem Cell Transplantation for Lymphoma.

Gonadal dysfunction, the most frequent endocrine complication in both sexes after autologous hematopoietic cell transplant (HCT) could increase bone loss and sarcopenia, a disease characterized by reduced muscle strength and mass. Sarcopenia is associated with worse survival, lower remission rates, and progression-free survival in patients with lymphoma after HCT. Low bone mass affected approximately 20% of the transplanted patients within 2 years and harms quality of life. This study was conducted in a single center and identified a strong relationship with patients transplanted more recently by LEC (lomustine, etoposide, and cyclophosphamide) conditioning regimen with sarcopenia. Peripheral neuropathy and bone mass changes were also associated with sarcopenia as well, suggesting a relationship with muscle strength loss.

Type VI Collagen Deficiency Causes Enhanced Periodontal Tissue Destruction

The periodontal ligament (PDL) is a fibrillar connective tissue that lies between the alveolar bone and the tooth and is composed of highly specialized extracellular matrix (ECM) molecules and a heterogeneous population of cells that are responsible for collagen formation, immune response, bone formation, and chewing force sensation. Type VI collagen (COL6), a widely distributed ECM molecule, plays a critical role in the structural integrity and mechanical properties of various tissues including muscle, tendon, bone, cartilage, and skin. However, its role in the PDL remains largely unknown. Our study shows that deficiency of COL6 impairs PDL fibrillogenesis and exacerbates tissue destruction in ligature-induced periodontitis (LIP). We found that COL6-deficient mice exhibited increased bone loss and degraded PDL in LIP and that fibroblasts expressing high levels of Col6α2 are pivotal in ECM organization and cell-ECM interactions. Moreover, COL6 deficiency in the PDL led to an increased number of fibroblasts geared toward the inflammatory response. We also observed that cultured COL6-deficient fibroblasts from the PDL exhibited decreased expression of genes related to collagen fiber turnover and ECM organization as well as migration and proliferation. Our findings suggest that COL6 plays a crucial role in the PDL, influencing fibroblast function in fibrillogenesis and affecting the immune response in periodontitis. These insights advance our understanding of the molecular mechanisms underlying PDL maturation and periodontal disease.

14-3-3ζ suppresses RANKL signaling by destabilizing TRAF6

Macrophages are essential regulators of inflammation and bone loss. RANKL, a pro-inflammatory cytokine, is responsible for macrophage differentiation to osteoclasts and bone loss. We recently showed that 14-3-3ζ-knockout (YwhazKO) rats exhibit increased bone loss in the inflammatory arthritis model. 14-3-3ζ is a cytosolic adaptor protein that actively participates in many signaling transductions. However, the role of 14-3-3ζ in RANKL signaling or bone remodeling is unknown. We investigated how 14-3-3ζ affects osteoclast activity by evaluating its role in RANKL signaling. We utilized 14-3-3ζ-deficient primary bone marrow-derived macrophages (BMDMs) obtained from wildtype (Wt) and YwhazKO animals, and RAW cells generated using CRISPR-Cas9. Our results showed that 14-3-3ζ-deficient macrophages, upon RANKL stimulation, have bigger and stronger TRAP-positive multinucleated cells and increased bone resorption activity. The presence of 14-3-3ζ suppressed RANKL-induced MAPK and AKT phosphorylation, transcription factors (NFATC1 and p65) nuclear translocation, and subsequently, gene induction (Rank, Acp5, and Ctsk). Mechanistically, 14-3-3ζ interacts with TRAF6, an essential component of the RANKL receptor complex. Upon RANKL stimulation, 14-3-3ζ-TRAF6 interaction was increased, while RANK-TRAF6 interaction was decreased. Importantly, 14-3-3ζ supported TRAF6 ubiquitination and degradation by the proteasomal pathway, thus dampening the downstream RANKL signaling. Together, we show that 14-3-3ζ regulates TRAF6 levels to suppress inflammatory RANKL signaling and osteoclast activity. To the best of our knowledge, this is the first report on 14-3-3ζ regulation of RANKL signaling and osteoclast activation.

METTL3-mediated pre-miR-665/DLX3 m6A methylation facilitates the committed differentiation of stem cells from apical papilla

Methyltransferase-like 3 (METTL3) is a crucial element of N6-methyladenosine (m6A) modifications and has been extensively studied for its involvement in diverse biological and pathological processes. In this study, we explored how METTL3 affects the differentiation of stem cells from the apical papilla (SCAPs) into odonto/osteoblastic lineages through gain- and loss-of-function experiments. The m6A modification levels were assessed using m6A dot blot and activity quantification experiments. In addition, we employed Me-RIP microarray experiments to identify specific targets modified by METTL3. Furthermore, we elucidated the molecular mechanism underlying METTL3 function through dual-luciferase reporter gene experiments and rescue experiments. Our findings indicated that METTL3+/− mice exhibited significant root dysplasia and increased bone loss. The m6A level and odonto/osteoblastic differentiation capacity were affected by the overexpression or inhibition of METTL3. This effect was attributed to the acceleration of pre-miR-665 degradation by METTL3-mediated m6A methylation in cooperation with the “reader” protein YTHDF2. Additionally, the targeting of distal-less homeobox 3 (DLX3) by miR-665 and the potential direct regulation of DLX3 expression by METTL3, mediated by the “reader” protein YTHDF1, were demonstrated. Overall, the METTL3/pre-miR-665/DLX3 pathway might provide a new target for SCAP-based tooth root/maxillofacial bone tissue regeneration.

Alcohol and Periodontal Disease: A Narrative Review.

The scientific literature dealing with alcohol and alcoholic beverages revealed that these drinks possess an adverse impact on periodontal tissues. Additionally, other principal risk factors include tobacco, smoking, poor oral hygiene, etc. It has been observed that among chronic alcoholics, there are further issues, such as mental, social, and physical effects, that promote alcoholism. These people may have weak immunity for defense against pathogenic organisms and bacteria. Thus, chances of gingival bleeding, swollen gums, bad breath, and increased bone loss are there. Different alcoholic beverages in the market cause less salivation; these beverages contain sugars that promote acid production in the oral cavity by pathogens that demineralize the enamel and damage gum and teeth. This chronic alcohol consumption can progress into different types of oral disorders, including cancer, halitosis, and caries, and is also associated with tobacco and smoking. Chronic alcohol consumption can cause alteration of the oral microbiome and increase oral pathogens, which lead to periodontal disease and an environment of inflammation created in the body due to malnutrition, diminished immunity, altered liver condition, brain damage, and gut microbiota alteration. Heavily colored alcoholic beverages produce staining on teeth and, due to less saliva, may cause other toxic effects on the periodontium. Over-dependency on alcohol leads to necrotizing lesions such as necrotizing gingivitis, necrotizing periodontitis, and necrotizing stomatitis. These pathological impairments instigate severe damage to oral structures. Therefore, proper counseling by the attending dental surgeon and related health professionals is urgently required for the patient on the basis that the individual case needs to go away from the regular heavy consumption of alcohol.

Deep learning-based harmonization of trabecular bone microstructures between high- and low-resolution CT imaging.

Osteoporosis is a bone disease related to increased bone loss and fracture-risk. The variability in bone strength is partially explained by bone mineral density (BMD), and the remainder is contributed by bone microstructure. Recently, clinical CT has emerged as a viable option for in vivo bone microstructural imaging. Wide variations in spatial-resolution and other imaging features among different CT scanners add inconsistency to derived bone microstructural metrics, urging the need for harmonization of image data from different scanners. This paper presents a new deep learning (DL) method for the harmonization of bone microstructural images derived from low- and high-resolution CT scanners and evaluates the method's performance at the levels of image data as well as derived microstructural metrics. We generalized a three-dimensional (3D) version of GAN-CIRCLE that applies two generative adversarial networks (GANs) constrained by the identical, residual, and cycle learning ensemble (CIRCLE). Two GAN modules simultaneously learn to map low-resolution CT (LRCT) to high-resolution CT (HRCT) and vice versa. Twenty volunteers were recruited. LRCT and HRCT scans of the distal tibia of their left legs were acquired. Five-hundred pairs of LRCT and HRCT image blocks of voxels were sampled for each of the twelve volunteers and used for training in supervised as well as unsupervised setups. LRCT and HRCT images of the remaining eight volunteers were used for evaluation. LRCT blocks were sampled at 32 voxel intervals in each coordinate direction and predicted HRCT blocks were stitched to generate a predicted HRCT image. Mean±standard deviation of structural similarity (SSIM) values between predicted and true HRCT using both 3DGAN-CIRCLE-based supervised (0.84±0.03) and unsupervised (0.83±0.04) methods were significantly (p<0.001) higher than the mean SSIM value between LRCT and true HRCT (0.75±0.03). All Tb measures derived from predicted HRCT by the supervised 3DGAN-CIRCLE showed higher agreement (CCC [0.956 0.991]) with the reference values from true HRCT as compared to LRCT-derived values (CCC [0.732 0.989]). For all Tb measures, except Tb plate-width (CCC=0.866), the unsupervised 3DGAN-CIRCLE showed high agreement (CCC [0.920 0.964]) with the true HRCT-derived reference measures. Moreover, Bland-Altman plots showed that supervised 3DGAN-CIRCLE predicted HRCT reduces bias and variability in residual values of different Tb measures as compared to LRCT and unsupervised 3DGAN-CIRCLE predicted HRCT. The supervised 3DGAN-CIRCLE method produced significantly improved performance (p<0.001) for all Tb measures as compared to the two DL-based supervised methods available in the literature. 3DGAN-CIRCLE, trained in either unsupervised or supervised fashion, generates HRCT images with high structural similarity to the reference true HRCT images. The supervised 3DGAN-CIRCLE improves agreements of computed Tb microstructural measures with their reference values and outperforms the unsupervised 3DGAN-CIRCLE. 3DGAN-CIRCLE offers a viable DL solution to retrospectively improve image resolution, which may aid in data harmonization in multi-site longitudinal studies where scanner mismatch is unavoidable.

CHRONIC STRESS RESULTS IN INCREASED PAIN PERCEPTION IN OSTEOARTHRITIS IN VIVO

Osteoarthritis (OA) affects the whole joint and leads to chronic pain. The sympathetic nervous system (SNS) seems to be involved in OA pathogenesis, as indicated by in vitro studies as well as by our latest work demonstrating that sympathectomy in mice results in increased subchondral bone volume in the OA knee joint. We assume that chronic stress may lead to opposite effects, such as an increased bone loss in OA due to an elevated sympathetic tone. Therefore, we analyzed experimental OA progression in mice exposed to chronic stress. OA was induced in male C57BL/6J mice by surgical destabilization of the medial meniscus (DMM) and Sham as well as non-operated mice served as controls. Half of these groups were exposed to chronic unpredictable mild stress (CUMS). After 12 weeks, chronic stress efficiency was assessed using behavioral tests. In addition to measuring body weight and length, changes in subchondral bone were analyzed by μCT. Dynamic Weight Bearing system was used to monitor OA-related pain. Histological scoring will be conducted to investigate the severity cartilage degeneration and synovial inflammation. CUMS resulted in increased anxiety and significant decrease in body weight gain in all CUMS groups compared to non-CUMS groups. CUMS also increased serum corticosterone in healthy mice, with even higher levels in CUMS mice after DMM surgery. CUMS had no significant effect on subchondral bone, but subarticular bone mineral density and trabecular thickness were increased. Moreover, CUMS resulted in significant potentiation of DMM-associated pain. Our results suggest that the autonomic imbalance with increased sympathetic nervous activity induced by chronic stress exacerbates the severity of OA pain perception. We expect significantly increased cartilage degeneration as well as more severe synovial inflammation in CUMS DMM mice compared to DMM mice.

Vitamin D and Calcium and Bioavailability of Calcium in Various Calcium Salts.

The active form of vitamin D, 1,25D3, plays an important function in the metabolism of calcium. The recommended daily INTAKE of Calcium varies from 1300 mg/day during adolescence to 1200 mg/day after the age of 50 years. Similarly, for vitamin D, the recommended daily intake varies from 400 IU/day during adolescence to 1000 IU/day after the age of 70 years. There is an intricate inter-play of homeostasis of calcium led by vitamin D and PTH at various sites like intestine, kidney, and bones. The increased fracture risk due to bone loss and osteoporosis creates a burden on the patient, healthcare provider as well as the health system. As the population grows old worldwide gradually, the long-term sequelae like pain, loss of independence, and institutionalized care will become more pervasive. Behavioral change to incorporate a healthy lifestyle, including optimal calcium and vitamin D intake and physical exercise in adolescence, form the important foundation in the program for osteoporosis prevention. Increased emphasis on lifestyle modification and nutrition should be given during times of increased bone loss in old age and after menopause.

BORS/BJR TRAVELLING FELLOWSHIP ABSTRACT: THE EFFECT OF INCREASING BONE LOSS ON THE PRIMARY STABILITY OF METAPHYSEAL SLEEVES IN THE PROXIMAL TIBIA. AN EXPERIMENTAL STUDY USING SAWBONE TIBIAS

AbstractApproximately 20% of primary and revision Total Knee Arthroplasty (TKA) patients require multiple revisions, which are associated with poor survivorship, with worsening outcomes for subsequent revisions. For revision surgery, either endoprosthetic replacements or metaphyseal sleeves can be used for the repair, however, in cases of severe defects that are deemed “too severe” for reconstruction, endoprosthetic replacement of the affected area is recommended. However, endoprosthetic replacements have been associated with high complication rates (high incidence rates of prosthetic joint infection), while metaphyseal sleeves have a more acceptable complication profile and are therefore preferred. Despite this, no guidance exists as to the maximal limit of bone loss, which is acceptable for the use of metaphyseal sleeves to ensure sufficient axial and rotational stability. Therefore, this study assessed the effect of increasing bone loss on the primary stability of the metaphyseal sleeve in the proximal tibia to determine the maximal bone loss that retains axial and rotational stability comparable to a no defect control.Methodsto determine the pattern of bone loss and the average defect size that corresponds to the clinically defined defect sizes of small, medium and large defects, a series of pre-operative x-rays of patients with who underwent revision TKA were retrospectively analysed. Ten tibiae sawbones were used for the experiment. To prepare the bones, the joint surface was resected the typical resection depth required during a primary TKA (10mm). Each tibia was secured distally in a metal pot with perpendicular screws to ensure rotational and axial fixation to the testing machine. Based on X-ray findings, a fine guide wire was placed 5mm below the cut joint surface in the most medial region of the plateau. Core drills (15mm, 25mm and 35mm) corresponding to small, medium and large defects were passed over the guide wire allowing to act at the centre point, before the bone defect was created. The test was carried out on a control specimen with no defect, and subsequently on a Sawbone with a small, medium or large defect. Sleeves were inserted using the published operative technique, by trained individual using standard instruments supplied by the manufacturers. Standard axial pull-out (0 – 10mm) force and torque (0 – 30°) tests were carried out, recording the force (N) vs. displacement (mm) curves.ResultsA circular defect pattern was identified across all defects, with the centre of the defect located 5mm below the medial tibial base plate, and as medial as possible. Unlike with large defects, small and medium sized defects reduced the pull-out force and torque at the bone-implant interface, however, these reductions were not statistically significant when compared to no bony defect.ConclusionsThis experimental study demonstrated that up to 35mm radial defects may be an acceptable “critical limit” for bone loss below which metaphyseal sleeve use may still be appropriate. Further clinical assessment may help to confirm the findings of this experimental study. This study is the first in the literature to aim to quantify “critical bone loss” limit in the tibia for revision knee arthroplasty.Declaration of Interest(a) fully declare any financial or other potential conflict of interest

SAT182 Effects Of An Orally Bioavailable Nonpeptide Parathyroid Hormone Receptor Type 1 (PTH1R) Antagonist In Rodent Models Of Primary Hyperparathyroidism (PHPT)

Abstract Disclosure: A.S. Antwan: Employee; Self; Crinetics Pharmaceuticals. E. Rico-Bautista: Employee; Self; Crinetics Pharmaceuticals. J. Pontillo: Employee; Self; Crinetics Pharmaceuticals. S. Wang: Employee; Self; Crinetics Pharmaceuticals. M. Johns: Employee; Self; Crinetics Pharmaceuticals. B. Ramms: Employee; Self; Crinetics Pharmaceuticals. M.A. Fowler: Employee; Self; Crinetics Pharmaceuticals. J.B. Nguyen: Employee; Self; Crinetics. A.A. Castellanos Gonzalez: Employee; Self; Crinetics. B. Fleck: Employee; Self; Crinetics Pharmaceuticals. K. Retting: Employee; Self; Crinetics Pharmaceuticals. D. Dalvie: Employee; Self; Crinetics Pharmaceuticals. S.F. Betz: Employee; Self; Crinetics Pharmaceuticals. S. Markison: Employee; Self; Crinetics Pharmaceuticals. Primary hyperparathyroidism (PHPT) is a condition resulting from an over-secretion of parathyroid hormone (PTH) from one or more overactive parathyroid glands. PTH is a peptide hormone that regulates blood calcium concentrations through effects on bone, intestines, and kidney. PTH acts on parathyroid hormone receptor type 1 (PTH1R) in the kidney to increase calcium reabsorption and block phosphate reabsorption. The loss of phosphate ions then causes an increase in ionized calcium in the blood and cAMP in the urine. At the bone, continuous PTH infusion stimulates osteoclast activity while inhibiting osteoblast activity, leading to breakdown of bone and release of calcium into the extracellular fluid. Conditions that cause excess PTH, such as PHPT, result in elevated concentrations of plasma calcium, increased bone loss, increased fracture risk, and higher susceptibility to kidney stone development. PHPT affects approximately 100,000 patients per year, but many patients are asymptomatic and remain undiagnosed. While a partial or total parathyroidectomy may be suitable for patients diagnosed with severe cases of PHPT, there are limited treatment options for those who do not meet the criteria or do not wish to undergo surgery. The goals for medicinal treatment are to normalize blood calcium levels and urinary calcium excretion, as well as increase bone mineral density to reduce fracture risk. Blocking PTH action directly via a potent PTH1R antagonist may provide an important new therapeutic mechanism to treat patients with PHPT. Using iterative medicinal chemistry and pharmacology, Crinetics has identified several potent and orally bioavailable PTH1R antagonists with good drug-like properties. Lead molecules were evaluated in vivo in preclinical rodent models for their ability to suppress the effects of excess PTH on serum calcium, bone turnover, and cAMP levels in the kidney. One of these compounds, ANT-5, was characterized as a potent negative allosteric modulator of both human and rat PTH1R. In rats, oral administration of ANT-5 dose-dependently suppressed PTH-induced hypercalcemia. ANT-5 also suppressed PTH-stimulated urinary cAMP in rats, indicating its ability to inhibit the actions of PTH in the kidney. We further evaluated the effect of ANT-5 in a rodent model of continuous PTH infusion-induced bone turnover. Once-daily oral administration of ANT-5 mitigated PTH-induced bone resorption, suggesting that inhibiting PTH1R may have beneficial clinical effects on bone density. The culmination of these studies has led to a subset of candidate molecules that are being evaluated in safety studies to identify the compound(s) suitable for evaluation in human clinical trials. Support: Crinetics Pharmaceuticals. Presentation: Saturday, June 17, 2023

THU413 Does Continuous Positive Airway Pressure Affect Bone Loss Process In The Population Of Sleep Apnea?

Abstract Disclosure: Y. Chen: None. A. Suresh: None. S. Haile: None. Z. Perciuleac: None. B. Soni: None. A. Cuevas Velazquez: None. A. Amirian: None. C. Udeh: None. L. Sangha: None. B. Ravichander: None. K. Aljassani: None. R. Joshi: None. A. Atrash: None. N. Ramesh: None. J. Sta. Cruz: None. S. Al-saadi: None. Introduction: Patients with obstructive sleep apnea (OSA) were reported to have higher risk of developing osteoporosis or increased bone loss. One of the theories suggested nocturnal hypoxia led to imbalanced osteoclastic activity and contributed to bone loss. Continuous Positive Airway Pressure (CPAP) is the first-line treatment for OSA, which improves airway obstruction and limits hypoxia. This study attempts to evaluate if compliant with CPAP therapy reduces bone loss. Methods: This retrospective study included patients who visited UPMC Central Pa. sleep medicine clinic from January 2010 to October 2022 with diagnosis of OSA and have at least two dual-energy X-ray absorptiometry (DEXA) after the OSA diagnosis. Patients’ records of CPAP usage on two databases, Respironics and Resmed, were used to assess the compliance of the therapy. The definition of compliance is average usage of 4hrs/night; frequency of use being 70% or above. Patient demographics, CPAP compliance, bone mineral density (BMD) and T-scores of two DEXAs were obtained. All data after diagnosis of active malignancy, hyperparathyroidism, end stage renal disease, or after patient received osteoporosis pharmacological treatment are excluded. Annual change of BMD was calculated with the difference of BMD between the two DEXA scans divided by the study interval. Two-sample t-test and chi-square test were used for analysis. Results: 265 patients were included for analysis, with 254 female (95.8%), 92.1% Caucasian, mean age 68.3 years old, mean BMI 36.7kg/m2. 165 patients were compliant and 100 were non-compliant. The two groups were identical on demographic data including age, sex, ethnicities. The median of annual BMD changes at L-spine, left femur neck, left femur total, and left radius were 0.003, −0.003, −0.002, −0.002 g/cm2 respectively in compliant group and 0.003, 0, −0.006, −0.002 g/ cm2 in non-compliant group. The annual changes of T-scores were 0, −0.043, 0, −0.036 for the compliant group and 0, 0, −0.051, −0.034 for non-compliant group. No significant within-group or between-group difference in annual bone density reduction on BMD or T-score was noted in our analysis. Discussions: Our study did not reveal the benefit of treating OSA on bone loss. Small sample size could be the leading factor for the limited effect size. Retrospective study design also restricted our study population to predominantly postmenopausal Caucasian female. Further adjustments for possible confounding factors including BMI and age might be beneficial. Future study with prospective design, larger sample size, and diverse population is encouraged to discover the effect of CPAP therapy on BMD preservation. Presentation: Thursday, June 15, 2023

Genetic polymorphism of interleukins 6 and 17 correlated with apical periodontitis: A Cross-sectional study.

Interleukins 6 and 17 act in bone resorption in the presence of infections of endodontic origin for host defense. Genetic polymorphisms may be associated with increased bone loss, represented by areas of large periapical lesions. This study aimed to verify the frequency of interleukin 6 and 17 gene polymorphism in patients with asymptomatic apical periodontitis or chronic apical abscess and to verify the existence of correlations between periapical lesion area with age, gender, and presence of the polymorphism, in the studied population, in the state of Pernambuco. A population consisting of thirty diagnosed individuals was included. The area of the lesions was measured in mm². Genomic DNA was extracted and genotyping was performed by Polymerase Chain Reaction Restriction Fragment Length Polymorphism for interleukin 6 (rs 1800795) and interleukin 17 (rs 2275913). Fisher's exact, chi-square, and odds ratio tests were used. A logistic regression analysis was also performed using sex, age, and the presence of polymorphism as covariates, in addition to linear regression to test the relationship between age and lesion area. All tests used a significance level of 0.05% (p ≤0.05%). There was no statistical significance in the occurrence of large areas of periapical lesions correlated with age, sex, and diagnosis, nor in the distribution of alleles in the polymorphism of interleukins 6 and 17 in the studied groups. The frequency of homozygous and heterozygous polymorphism was high. The polymorphism of these interleukins is not correlated with the increase in the areas of asymptomatic periapical inflammatory lesions.

Characteristics of mandibular anterior alveolar bone in patients with different degrees of periodontitis: a retrospective study based on CBCT.

To investigate the alveolar bone characteristics of mandibular anterior teeth in patients with periodontitis. 100 patients with periodontitis were selected and grouped according to the degrees of alveolar bone resorption, age, gender, and tooth type. The labial thickness of the alveolar bone, the degree of alveolar bone resorption, angulation between the long axis of teeth and alveolar process, alveolar bone height and density of the mandibular anterior teeth were measured. There were significant differences in alveolar bone morphology between these three groups. Compared with the mild and moderate groups, the severe group showed that the alveolar bone in the half of the root crown was thickened, the alveolar bone height was decreased, the cancellous alveolar bone density was increased, and the cortical alveolar bone density was decreased. The resorption of alveolar bone was characterized by greater resorption of proximal bone than that of labial bone with increased bone loss. There were also differences in alveolar bone characteristics among patients of different ages, genders, and tooth types. The morphology of the mandibular anterior alveolar bone changed accordingly with the degree of periodontitis. Labial alveolar bone thickness and cortical alveolar bone density were negatively correlated with the degree of periodontitis, while alveolar bone height and cancellous alveolar bone density were positively correlated with the degree of periodontitis. These results allow clinicians to better understand the alveolar bone morphology of the mandibular anterior teeth in patients with periodontitis, facilitating better treatment design and avoiding complications.

Azilsartan inhibits inflammation-triggered bone resorption and osteoclastogenesis in vivo via suppression of TNF-α expression in macrophages.

Hypertension is a major risk factor for cardiovascular disease (CVD) and is associated with increased bone loss due to excessive activity of the local renin-angiotensin system (RAS). Angiotensinogen/Angiotensin (ANG) II/Angiotensin II type 1 receptor (AT1R) axis is considered as the core axis regulating RAS activity. Azilsartan is an FDA-approved selective AT1R antagonist that is used to treat hypertension. This study aimed to determine whether azilsartan affects formation of osteoclast, resorption of bone, and the expression of cytokines linked with osteoclastogenesis during lipopolysaccharide (LPS)-triggered inflammation in vivo. In vivo, following a 5-day supracalvarial injection of LPS or tumor necrosis factor-alpha (TNF-α) with or without azilsartan, the proportion of bone resorption and the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells, which are identified as osteoclasts on mice calvariae were counted. The mRNA expression levels of TRAP, cathepsin K, receptor activator of NF-κB ligand (RANKL), and TNF-α were also evaluated. In vitro, the effect of azilsartan (0, 0.01, 0.1, 1, and 10 μM) on RANKL and TNF-α-triggered osteoclastogenesis were investigated. Also, whether azilsartan restrains LPS-triggered TNF-α mRNA and protein expression in macrophages and RANKL expression in osteoblasts were assessed. Furthermore, western blotting for analysis of mitogen-activated protein kinases (MAPKs) signaling was conducted. Azilsartan-treated calvariae exhibited significantly lower bone resorption and osteoclastogenesis than those treated with LPS alone. In vivo, LPS with azilsartan administration resulted in lower levels of receptor activator of RANKL and TNF-α mRNA expression than LPS administration alone. Nevertheless, azilsartan did not show inhibitory effect on RANKL- and TNF-α-triggered osteoclastogenesis in vitro. Compared to macrophages treated with LPS, TNF-α mRNA and protein levels were lower in macrophages treated by LPS with azilsartan. In contrast, RANKL mRNA and protein expression levels in osteoblasts were the same in cells co-treated with azilsartan and LPS and those exposed to LPS only. Furthermore, azilsartan suppressed LPS-triggered MAPKs signaling pathway in macrophages. After 5-day supracalvarial injection, there is no difference between TNF-α injection group and TNF-α with azilsartan injection group. These findings imply that azilsartan prevents LPS-triggered TNF-α production in macrophages, which in turn prevents LPS-Triggered osteoclast formation and bone resorption in vivo.

LincRNA-EPS inhibits caspase-11 and NLRP3 inflammasomes in gingival fibroblasts to alleviate periodontal inflammation.

To investigate the effects of long intergenic noncoding RNA-erythroid prosurvival (lincRNA-EPS) on periodontal inflammation mediated by inflammasomes and to explore its mechanism. Experimental periodontitis was induced in KO (lincRNA-EPS-/- ) and WT (lincRNA-EPS+/+ ) mice to compare the periodontal bone loss and inflammation by using micro-computed tomography, immunofluorescence staining and haematoxylin and eosin staining. The expression and activation of cysteinyl aspartate-specific proteinase-11 (caspase-11) and NOD-like receptor protein 3 (NLRP3) inflammasomes, as well as nuclear factor-kappa B (NF-κB) activation in mouse gingival fibroblasts (MGFs), were measured by real-time quantitative polymerase chain reaction, Western blotting, enzyme-linked immunosorbent and lactate dehydrogenase assays. MGFs were transfected with overexpression plasmids to assess the biological functions of lincRNA-EPS. RNA pull-down and immunoprecipitation experiments were performed to identify the interacting protein of lincRNA-EPS. LincRNA-EPS-expressing lentivirus was locally administered to inflamed periodontal tissues to evaluate its salvage function in periodontitis. The absence of lincRNA-EPS increased bone loss and expression of myeloperoxidase, interleukin-1α (IL-1α) and IL-1β in the inflammatory periodontium. LincRNA-EPS KO MGFs exhibited increased expression and activation of caspase-11/NLRP3 inflammasome components than WT MGFs under lipopolysaccharide (LPS) stimulation. The expression and activation of these molecules were inhibited in lincRNA-EPS overexpressed MGFs. Mechanistically, lincRNA-EPS directly bound to transactive response DNA-binding protein 43 (TDP43) in the nucleus of MGFs, and TDP43 knockdown exerted a similar inhibitory effect on NF-κB activation and the inflammasomes as lincRNA-EPS overexpression. Locally injecting lincRNA-EPS-expressing lentivirus weakened the periodontal damage. LincRNA-EPS inhibits the LPS-induced production and activation of caspase-11 and NLRP3 inflammasomes by suppressing the activation of the NF-κB signalling pathway via interacting with TDP43, thereby alleviating periodontitis.