Multiscale effects of the calcimimetic drug, etelcalcetide on bone health of rats with secondary hyperparathyroidism induced by chronic kidney disease

Chronic kidney disease-induced secondary hyperparathyroidism (CKD-SHPT) heightens fracture risk through impaired mineral homeostasis and elevated levels of uremic toxins (UTs), which in turn enhance bone remodeling. Etelcalcetide (Etel), a calcium-sensing receptor (CaSR) agonist, suppresses parathyroid hormone (PTH) in hyperparathyroidism to reduce excessive bone resorption, leading to increased bone mass. However, Etel's effect on bone quality, chemical composition, and strength is not well understood. To address these gaps, we established a CKD-SHPT rat model and administered Etel at a human-equivalent dose concurrently with disease induction. The effects on bone and mineral homeostasis were compared with a CKD-SHPT (vehicle-treated group) and a control group (rats without SHPT). Compared with vehicle-treated CKD-SHPT rats, Etel treatment improved renal function, reduced circulating UT levels, improved mineral homeostasis parameters, decreased PTH levels, and prevented mineralization defects. The upregulation of mineralization-promoting genes by Etel in CKD-SHPT rats might explain its ability to prevent mineralization defects. Etel preserved both trabecular and cortical bones with attendant suppression of osteoclast function, besides increasing mineralization. Etel maintained the number of viable osteocytes to the control level, which could also contribute to its beneficial effects on bone. CKD-SHPT rats displayed increased carbonate substitution of matrix and mineral, decreased crystallinity, mineral-to-matrix ratio, and collagen maturity, and these changes were mitigated by Etel. Further, Etel treatment prevented CKD-SHPT-induced deterioration in bone strength and mechanical behavior. Based on these findings, we conclude that in CKD-SHPT rats, Etel has multiscale beneficial effects on bone that involve remodeling suppression, mineralization gene upregulation, and preservation of osteocytes.

Combined diosmin and bisoprolol attenuate cobalt chloride-induced cardiotoxicity and endothelial dysfunction through modulating miR-143-3P/MAPK/MCP-1, ERK5/CXCR4, Orai-1/STIM-1 signaling pathways

Even while accelerated cardiomyocyte apoptosis is one of the primary causes of cardiac damage, the underlying mechanism is still mostly unknown. In addition to examining potential protective effects of bisoprolol and diosmin against CoCl2-induced cardiac injury, the goal of this study was to identify potential mechanisms regulating the hypoxic cardiac damage caused by cobalt chloride (CoCl2). For a period of 21 days except Cocl2 14 days from the first day of the experiment, rats were split into the following groups: Normal control group, rats received vehicle only (2 ml/kg/day, p.o.), (Cocl2, 150 mg/kg/day, p.o.), bisoprolol (25 mg/kg/day, p.o.); diosmin (100 mg/kg/day, p.o.) and bisoprolol + diosmin + Cocl2 groups. At the end of the experimental period, serum was taken for estimation of cardiac function, lipid profile, and pro/anti-inflammatory cytokines. Moreover, tissue samples were collected for evaluation of oxidative stress, endothelial dysfunction, α-SMA, PKC-α, MiR-143-3P, MAPK, ERK5, MCP-1, CXCR4, Orai-1, and STIM-1. Diosmin and bisoprolol, either alone or in combination, enhance heart function by reducing abnormalities in the electrocardiogram and the hypotension brought on by CoCl2. Additionally, they significantly ameliorate endothelial dysfunction by downregulating the cardiac expressions of α-SMA, PKC-α, MiR-143-3P, MAPK, ERK5, MCP-1, CXCR4, Orai-1, and STIM-1. Bisoprolol and diosmin produced modulatory activity against inflammatory state, redox balance, and atherogenic index concurrently. Together, diosmin and bisoprolol, either alone or in combination, significantly reduced all the cardiac alterations brought on by CoCl2. The capacity to obstruct hypoxia-induced α-SMA, PKC-α, MiR-143-3P/MAPK/MCP-1, MiR-143-3P/ERK5/CXCR4, Orai-1/STIM-1 signaling activation, as well as their anti-inflammatory, antioxidant, and anti-apoptotic properties, may be responsible for these cardio-protective results.

Osteogenic effect of an adiponectin-derived short peptide that rebalances bone remodeling: a potential disease-modifying approach for postmenopausal osteoporosis therapy

Adiponectin, an adipokine, regulates metabolic processes, including glucose flux, lipid breakdown, and insulin response, by activating adiponectin receptors 1 and 2 (AdipoR1 and AdipoR2). We have previously shown that globular adiponectin (gAd), an endogenous form of adiponectin, has osteoanabolic and anti-catabolic effects in rodent models of postmenopausal osteopenia. Moreover, we reported the identification of a 13-mer peptide (ADP-1) from the collagen domain of adiponectin, which exhibited significant adiponectin-mimetic properties. Since the clinical development of gAd is constrained by its large size, here, we investigated the osteogenic property of ADP-1. ADP-1 induced osteoblast differentiation more potently than gAd. ADP-1 elicited osteoblast differentiation through two downstream pathways that involved the participation of adiponectin receptors. Firstly, it enhanced mitochondrial biogenesis and OxPhos, leading to osteoblast differentiation. Secondly, it activated the Akt-glycogen synthase kinase 3β-Wnt pathway, thereby increasing osteoblast differentiation. Additionally, ADP-1 suppressed the production of receptor-activator of nuclear kappa B ligand from osteoblasts, enabling it to act as a dual-action molecule (suppressing osteoclast function besides promoting osteoblast function). In osteopenic ovariectomized rats, ADP-1 increased bone mass and strength and improved trabecular integrity by stimulating bone formation and inhibiting bone resorption. Furthermore, by increasing ATP-producing intermediates within the tricarboxylic acid cycle in bones, ADP-1 likely fueled osteoblast function. Given its dual-action mechanism and high potency, ADP-1 offers a unique opportunity to address the unmet clinical need to reset the aberrant bone remodeling in osteoporosis to normalcy, potentially offering a disease-modifying impact.

Hakai, a novel Runx2 interacting protein, augments osteoblast differentiation by rescuing Runx2 from Smurf2-mediated proteasome degradation

Runt-related transcription factor 2 (Runx2) is a key regulator of osteoblast differentiation and bone formation. In Runx2-deficient embryos, skeletal development ceases at the cartilage anlage stage. These embryos die of respiratory failure upon birth and display a complete absence of bone and cartilage mineralization. Here, we identified Hakai, a type of E3 ubiquitin ligase as a potential Runx2 interacting partner through affinity pulldown-based proteomic approach. Subsequently, we observed that similar to Runx2, Hakai was downregulated in osteopenic ovariectomized rats, suggesting its involvement in bone formation. Consistent with this observation, Hakai overexpression significantly enhanced osteoblast differentiation in mesenchyme-like C3H10T1/2 as well as primary rat calvaria osteoblast (RCO) cells in vitro. Conversely, overexpression of a catalytically inactive Hakai mutant (C109A) exhibited minimal to no effect, whereas Hakai depletion markedly reduced endogenous Runx2 levels and impaired osteogenic differentiation in both C3H10T1/2 and RCOs. Mechanistically, Hakai physically interacts with Runx2 and enhances its protein turnover by rescuing it from Smad ubiquitination regulatory factor 2 (Smurf2)-mediated proteasome degradation. Wild-type Hakai but not Hakai-C109A inhibited Smurf2 protein levels through proteasome-mediated degradation. These findings underscore Hakai's functional role in bone formation, primarily through its positive modulation of Runx2 protein turnover by protecting it from Smurf2-mediated ubiquitin-proteasomal degradation. Collectively, our results demonstrate Hakai as a promising novel therapeutic target for osteoporosis.

On-demand release of a selective MMP-13 blocker from an enzyme-responsive injectable hydrogel protects cartilage from degenerative progression in osteoarthritis

In osteoarthritis (OA), the degradation of cartilage is primarily driven by matrix metalloprotease-13 (MMP-13). Hence, the inhibition of MMP-13 has emerged as an attractive target for OA treatment. Among the various approaches that are being explored for MMP-13 regulation, blocking of the enzyme with specific binding molecules appears to be a more promising strategy for preventing cartilage degeneration. To enhance effectiveness and ensure patient compliance, it is preferable for the binding molecule to exhibit sustained activity when administered directly into the joint. Herein, we present an enzyme-responsive hydrogel that was designed to exhibit on-demand, the sustained release of BI-4394, a potent and highly selective MMP-13 blocker. The stable and compatible hydrogel was prepared using triglycerol monostearate. The efficacy of the hydrogel to prevent cartilage damage was assessed in a rat model of OA induced by anterior cruciate ligament transection (ACLT). The results revealed that in comparison to the rats administrated weekly with intra-articular BI-4394, the hydrogel implanted rats had reduced levels of inflammation and bone erosion. In comparison to untreated control, the cartilage in animals administered with BI-4394/hydrogel exhibited significant levels of collagen-2 and aggrecan along with reduced MMP-13. Overall, this study confirmed the potential of BI-4394 delivery using an enzyme-responsive hydrogel as a promising treatment option to treat the early stages of OA by preventing further cartilage degradation.

RING finger E3 ligase, RNF138 inhibits osteoblast differentiation by negatively regulating Runx2 protein turnover

A few ubiquitin ligases have been shown to target Runx2, the key osteogenic transcription factor and thereby regulate bone formation. The regulation of Runx2 expression and function are controlled both at the transcriptional and posttranslational levels. Really interesting new gene (RING) finger ubiquitin ligases of which RNF138 is a member are important players in the ubiquitin-proteasome system, contributing to the regulation of protein turnover and cellular processes. Here, we demonstrated that RNF138 negatively correlated with Runx2 protein levels in osteopenic ovariectomized rats which implied its role in bone loss. Accordingly, RNF138 overexpression potently inhibited osteoblast differentiation of mesenchyme-like C3H10T1/2 as well primary rat calvarial osteoblast (RCO) cells in vitro, whereas overexpression of catalytically inactive mutant RNF138Δ18-58 (lacks RING finger domain) had mild to no effect. Contrarily, RNF138 depletion copiously enhanced endogenous Runx2 levels and augmented osteogenic differentiation of C3H10T1/2 as well as RCOs. Mechanistically, RNF138 physically associates within multiple regions of Runx2 and ubiquitinates it leading to its reduced protein stability in a proteasome-dependent manner. Moreover, catalytically active RNF138 destabilized Runx2 which resulted in inhibition of its transactivation potential and physiological function of promoting osteoblast differentiation leading to bone loss. These findings underscore the functional involvement of RNF138 in bone formation which is primarily achieved through its modulation of Runx2 by stimulating ubiquitin-mediated proteasomal degradation. Thus, our findings indicate that RNF138 could be a promising novel target for therapeutic intervention in postmenopausal osteoporosis.

The Role of Osteogenic Effect and Vascular Function in Bone Health in Hypertensive Rats: A Study of Anti-hypertensive and Hemorheologic Drugs

Vascular dysfunction contributes to the development of osteopenia in hypertensive patients, as decreased blood supply to bones results in tissue damage and dysfunction. The effect of anti-hypertensive medicines on bone mass in hypertensive individuals is inconclusive because of the varied mechanism of their action, and suggests that reducing blood pressure (BP) alone is insufficient to enhance bone mass in hypertension. Pentoxifylline (PTX), a hemorheological drug, improves blood flow by reducing blood viscosity and angiogenesis, also has an osteogenic effect. We hypothesized that improving vascular function is critical to increasing bone mass in hypertension. To test this, we screened various anti-hypertensive drugs for their in vitro osteogenic effect, from which timolol and hydralazine were selected. In adult female spontaneously hypertensive rats (SHRs), timolol and hydralazine did not improve vascular function and bone mass, but PTX improved both. In female SHR animals, PTX restored bone mass, strength and mineralization, up to the level of normotensive control rats. In addition, we observed lower blood vasculature in the femur of adult SHR animals, and PTX restored them. PTX also restored the bone vascular and angiogenesis parameters that had been impaired in OVX SHR compared to sham SHR. This study demonstrates the importance of vascular function in addition to increased bone mass for improving bone health as achieved by PTX without affecting BP, and suggests a promising treatment option for osteoporosis in hypertensive patients, particularly at-risk postmenopausal women.

Hormonal and non-hormonal oral contraceptives given long-term to pubertal rats differently affect bone mass, quality and metabolism

Introduction

We investigated the effects of hormonal and non-hormonal oral contraceptives (OCs) on bone mass, mineralization, composition, mechanical properties, and metabolites in pubertal female SD rats.

Methods

OCs were given for 3-, and 7 months at human equivalent doses. The combined hormonal contraceptive (CHC) was ethinyl estradiol and progestin, whereas the non-hormonal contraceptive (NHC) was ormeloxifene. MicroCT was used to assess bone microarchitecture and BMD. Bone formation and mineralization were assessed by static and dynamic histomorphometry. The 3-point bending test, nanoindentation, FTIR, and cyclic reference point indentation (cRPI) measured the changes in bone strength and material composition. Bone and serum metabolomes were studied to identify potential biomarkers of drug efficacy and safety and gain insight into the underlying mechanisms of action of the OCs.

Results

NHC increased bone mass in the femur metaphysis after 3 months, but the gain was lost after 7 months. After 7 months, both OCs decreased bone mass and deteriorated trabecular microarchitecture in the femur metaphysis and lumbar spine. Also, both OCs decreased the mineral: matrix ratio and increased the unmineralized matrix after 7 months. After 3 months, the OCs increased carbonate: phosphate and carbonate: amide I ratios, indicating a disordered hydroxyapatite crystal structure susceptible to resorption, but these changes mostly reversed after 7 months, indicating that the early changes contributed to demineralization at the later time. In the femur 3-point bending test, CHC reduced energy storage, resilience, and ultimate stress, indicating increased susceptibility to micro-damage and fracture, while NHC only decreased energy storage. In the cyclic loading test, both OCs decreased creep indentation distance, but CHC increased the average unloading slope, implying decreased microdamage risk and improved deformation resistance by the OCs. Thus, reduced bone mineralization by the OCs appears to affect bone mechanical properties under static loading, but not its cyclic loading ability. When compared to an age-matched control, after 7 months, CHC affected 24 metabolic pathways in bone and 9 in serum, whereas NHC altered 17 in bone and none in serum. 6 metabolites were common between the serum and bone of CHC rats, suggesting their potential as biomarkers of bone health in women taking CHC.

Conclusion

Both OCs have adverse effects on various skeletal parameters, with CHC having a greater negative impact on bone strength.

Diosmin mitigates dexamethasone-induced osteoporosis in vivo: Role of Runx2, RANKL/OPG, and oxidative stress

Secondary osteoporosis is commonly caused by long-term intake of glucocorticoids (GCs), such as dexamethasone (DEX). Diosmin, a natural substance with potent antioxidant and anti-inflammatory properties, is clinically used for treating some vascular disorders. The current work targeted exploring the protective properties of diosmin to counteract DEX-induced osteoporosis in vivo. Rats were administered DEX (7 mg/kg) once weekly for 5 weeks, and in the second week, vehicle or diosmin (50 or 100 mg/kg/day) for the next four weeks. Femur bone tissues were collected and processed for histological and biochemical examinations. The study findings showed that diosmin alleviated the histological bone impairments caused by DEX. In addition, diosmin upregulated the expression of Runt-related transcription factor 2 (Runx2) and phosphorylated protein kinase B (p-AKT) and the mRNA transcripts of Wingless (Wnt) and osteocalcin. Furthermore, diosmin counteracted the rise in the mRNA levels of receptor activator of nuclear factor-kB ligand (RANKL) and the reduction in osteoprotegerin (OPG), both were induced by DEX. Diosmin restored the oxidant/antioxidant equilibrium and exerted significant antiapoptotic activity. The aforementioned effects were more pronounced at the dose level of 100 mg/kg. Collectively, diosmin has proven to protect rats against DEX-induced osteoporosis by augmenting osteoblast and bone development while hindering osteoclast and bone resorption. Our findings could be used as a stand for recommending supplementation of diosmin for patients chronically using GCs.

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.

Copper chelating peptides derived from tilapia (Oreochromis niloticus) skin as tyrosinase inhibitor: Biological evaluation, in silico investigation and in vivo effects

Binuclear copper ions at the active site determine the catalysis of tyrosinase (TYR)¹ whose activity can be inhibited by copper's chelation with other compounds. In this study, tilapia (Oreochromis niloticus) skin was used to generate TYR-inhibitory peptides after being treated by different enzymes and 4 h-Alcaline protease hydrolysate exhibited the highest TYR inhibition and copper chelation. Immobilized metal affinity chromatography was used for purifying copper chelating peptides, among which PFRMY (IC₅₀: 0.43 ± 0.08 mg/mL) and RGFTGM (IC₅₀: 1.61 ± 0.04 mg/mL) exhibited the highest TYR-inhibitory capacity and the lowest docking energy. Both two peptides inhibited TYR in a mixed manner and interacted with key residues binding to copper ions within TYR mainly by hydrogen bonds and hydrophobic forces, while PFRMY had a more compact and stable conjugation with TYR. Zebrafish assay revealed that PFRMY reduced not only melanin synthesis but in vivo TYR activity.

The Role of Sympathetic Nerves in Osteoporosis: A Narrative Review

Osteoporosis, a systemic bone disease, is characterized by decreased bone density due to various reasons, destructed bone microstructure, and increased bone fragility. The incidence of osteoporosis is very high among the elderly, and patients with osteoporosis are prone to suffer from spine fractures and hip fractures, which cause great harm to patients. Meanwhile, osteoporosis is mainly treated with anti-osteoporosis drugs that have side effects. Therefore, the development of new treatment modalities has a significant clinical impact. Sympathetic nerves play an important role in various physiological activities and the regulation of osteoporosis as well. Therefore, the role of sympathetic nerves in osteoporosis was reviewed, aiming to provide information for future targeting of sympathetic nerves in osteoporosis.

A novel extraction method enhanced the osteogenic and anti-osteoporosis effect of tea extract without any hepatotoxicity in ovariectomized rats

Tea (Camellia sinensis) has several reported health benefits, including that on bone health attributed to catechins of which the most abundant is epigallocatechin-3-gallate (EGCG). However, several preclinical and clinical studies raise safety concerns about EGCG in tea extract causing acute liver failure. Tea also contains kaempferol, albeit scanty, and it has hepatoprotective and osteogenic effects. Here, we utilized a novel extraction procedure of acid hydrolysis to enhance the osteogenic effect of tea extract while reducing its hepatotoxicity. The resultant extract (USKECSE) has a ~40-fold increase in kaempferol and a 2.5-fold reduction in EGCG content compared with the hydroethanolic extract (USCSE). In a female Sprague Dawley (SD) rat femur osteotomy model, USKECSE (100 mg/kg) but not USCSE promoted bone regeneration. In a rat postmenopausal osteoporosis model induced by bilateral ovariectomy (OVX), USKECSE through an osteogenic mechanism maintained bone mass, strength, and microarchitecture to the levels of ovary-intact rats with no hepatotoxic effect. After a single oral dose (100 mg/kg) of USKECSE to adult rats, kaempferol was detectable for 48 hours, suggesting its significant absorption and distribution in plasma. Peak kaempferol concentration in plasma (C_max) was 483 ng/ml (2 μM), and at this concentration, kaempferol induces osteoblast differentiation. USKECSE had no genotoxicity, and its safety index assessed by preclinical toxicity studies, including safety pharmacology, was >20-fold. Taken together, we report a novel extraction process that enhanced the osteogenicity and concomitantly reduced hepatotoxicity of tea extract with significant kaempferol bioavailability and a favorable systemic safety profile. Based on these data, we propose assessing the USKECSE effect for postmenopausal osteoporosis treatment.