Curcumin protects against ovariectomy-induced bone loss and decreases osteoclastogenesis

The potential therapeutic role of curcumin in osteoporosis treatment: based on multiple signaling pathways

Osteoporosis is a common chronic metabolic bone disease caused by disturbances in normal bone metabolism and an imbalance between osteoblasts and osteoclasts. Osteoporosis is characterized by a decrease in bone mass and bone density, leading to increased bone fragility. Osteoporosis is usually treated with medications and surgical methods, but these methods often produce certain side effects. Therefore, the use of traditional herbal ingredients for the treatment of osteoporosis has become a focus of attention and a hot topic in recent years. Curcumin, widely distributed among herbs such as turmeric, tulip, and curcuma longa, contains phenolic, terpenoid, and flavonoid components. Modern pharmacological studies have confirmed that curcumin has a variety of functions including antioxidant and anti-inflammatory properties. In addition, curcumin positively regulates the differentiation and promotes the proliferation of osteoblasts, which play a crucial role in bone formation. Multiple studies have shown that curcumin is effective in the treatment of osteoporosis as it interacts with a variety of signaling pathway targets, thereby interfering with the formation of osteoblasts and osteoclasts and regulating the development of osteoporosis. This review summarized the key signaling pathways and their mechanisms of action of curcumin in the prevention and treatment of osteoporosis and analyzed their characteristics and their relationship with osteoporosis and curcumin. This not only proves the medicinal value of curcumin as a traditional herbal ingredient but also further elucidates the molecular mechanism of curcumin's anti-osteoporosis effect, providing new perspectives for the prevention and treatment of osteoporosis through multiple pathways.

Global Trends in Research of Programmed Cell Death in Osteoporosis: A Bibliometric and Visualized Analysis (2000-2023)

Osteoporosis (OP) is a systemic metabolic bone disease that is characterized by decreased bone mineral density and microstructural damage to bone tissue. Recent studies have demonstrated significant advances in the research of programmed cell death (PCD) in OP. However, there is no bibliometric analysis in this research field. This study searched the Web of Science Core Collection (WoSCC) database for literature related to OP and PCD from 2000 to 2023. This study used VOSviewers 1.6.20, the "bibliometrix" R package, and CiteSpace (6.2.R3) for bibliometric and visualization analysis. A total of 2905 articles from 80 countries were included, with China and the United States leading the way. The number of publications related to PCD in OP is increasing year by year. The main research institutions are Shanghai Jiao Tong University, Chinese Medical University, Southern Medical University, Zhejiang University, and Soochow University. Bone is the most popular journal in the field of PCD in OP, and the Journal of Bone and Mineral Research is the most co-cited journal. These publications come from 14,801 authors, with Liu Zong-Ping, Yang Lei, Manolagas Stavros C, Zhang Wei, and Zhao Hong-Yan having published the most papers. Ronald S. Weinstein was co-cited most often. Oxidative stress and autophagy are the current research hot spots for PCD in OP. This bibliometric study provides the first comprehensive summary of trends and developments in PCD research in OP. This information identifies the most recent research frontiers and hot directions, which will provide a definitive reference for scholars studying PCD in OP.

Nutraceuticals and Functional Foods: A Comprehensive Review of Their Role in Bone Health

Bone health is the result of a tightly regulated balance between bone modeling and bone remodeling, and alterations of these processes have been observed in several diseases both in adult and pediatric populations. The imbalance in bone remodeling can ultimately lead to osteoporosis, which is most often associated with aging, but contributing factors can already act during the developmental age, when over a third of bone mass is accumulated. The maintenance of an adequate bone mass is influenced by genetic and environmental factors, such as physical activity and diet, and particularly by an adequate intake of calcium and vitamin D. In addition, it has been claimed that the integration of specific nutraceuticals such as resveratrol, anthocyanins, isoflavones, lycopene, curcumin, lutein, and β-carotene and the intake of bioactive compounds from the diet such as honey, tea, dried plums, blueberry, and olive oil can be efficient strategies for bone loss prevention. Nutraceuticals and functional foods are largely used to provide medical or health benefits, but there is an urge to determine which products have adequate clinical evidence and a strong safety profile. The aim of this review is to explore the scientific and clinical evidence of the positive role of nutraceuticals and functional food in bone health, focusing both on molecular mechanisms and on real-world studies.

Combined supplementation with hesperidin, phytosterols and curcumin decreases adiposity and improves metabolic health in ovariectomized rats

In recent years many women have looked for alternative therapies to address menopause. Hesperidin, phytosterols and curcumin are bioactive compounds that can ameliorate some cardiovascular risk factors associated with menopause, although there are no data concerning the effects of their combined supplementation. We used ovariectomized (OVX) rats, a postmenopausal model with oestrogen deficiency, to evaluate whether supplementation with a multi-ingredient (MI) including hesperidin, phytosterols and curcumin for 57 days would display beneficial effects against fat mass accretion and metabolic disturbances associated with menopause. Twenty OVX rats were orally supplemented with either MI (OVX-MI) or vehicle (OVX). Furthermore, 10 OVX rats orally received the vehicle along with subcutaneous injections of 17β-oestradiol biweekly (OVX-E2), whereas 10 rats were sham operated and received oral and injected vehicles (control group; SH). MI supplementation partly counteracted the fat mass accretion observed in OVX animals, which was evidenced by decreased total fat mass, adiposity index, the weight of retroperitoneal, inguinal and mesenteric white adipose tissue (MWAT) depots and MWAT adipocyte hypertrophy. These effects were accompanied by a significant decrease in the circulating levels of leptin and the mRNA levels of the fatty acid uptake-related genes Lpl and Cd36 in MWAT. These results were very similar to those observed in OVX-E2 animals. OVX-MI rats also displayed a higher lean body mass, lean/fat mass ratio, adiponectin-to-leptin ratio and insulin sensitivity than their OVX counterparts. Our findings can pave the way for using this MI formulation as an alternative therapy to manage obesity and to improve the cardiometabolic health of menopausal women.

Protective effects of curcumin against osteoporosis and its molecular mechanisms: a recent review in preclinical trials

Osteoporosis (OP) is one of the most common metabolic skeletal disorders and is commonly seen in the elderly population and postmenopausal women. It is mainly associated with progressive loss of bone mineral density, persistent deterioration of bone microarchitecture, and increased fracture risk. To date, drug therapy is the primary method used to prevent and treat osteoporosis. However, long-term drug therapy inevitably leads to drug resistance and specific side effects. Therefore, researchers are constantly searching for new monomer compounds from natural plants. As a candidate for the treatment of osteoporosis, curcumin (CUR) is a natural phenolic compound with various pharmacological and biological activities, including antioxidant, anti-apoptotic, and anti-inflammatory. This compound has gained research attention for maintaining bone health in various osteoporosis models. We reviewed preclinical and clinical studies of curcumin in preventing and alleviating osteoporosis. These results suggest that if subjected to rigorous pharmacological and clinical trials, naturally-derived curcumin could be used as a complementary and alternative medicine for the treatment of osteoporosis by targeting osteoporosis-related mechanistic pathways. This review summarizes the mechanisms of action and potential therapeutic applications of curcumin in the prevention and mitigation of osteoporosis and provides reference for further research and development of curcumin.

AMPK negatively regulates RANKL-induced osteoclast differentiation by controlling oxidative stress

AMP-activated protein kinase (AMPK) is a crucial energy sensor of cellular metabolism under various metabolic stresses, such as oxidative stress and inflammation. AMPK deficiency increases osteoclast numbers and reduces bone mass; however, the precise mechanisms remain unclear. This study aimed to clarify the mechanistic connection between AMPK and osteoclast differentiation, and the potential role of AMPK in the anti-resorptive effects of several phytochemicals. We found that receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL)-induced osteoclast differentiation, osteoclastic gene expression, and activation of mitogen-activated protein kinase (MAPK) and NF-κB were promoted in cells transfected with AMPK siRNA. AMPK knockdown led to defective synthesis of heme oxygenase-1, an antioxidant enzyme, and the upstream mediator, nuclear factor erythroid-2-related factor 2. Furthermore, treatment with N-acetyl-l-cysteine, an antioxidant, abolished osteoclast differentiation and MAPK/NF-κB activation induced by AMPK knockdown. AMPK activators, hesperetin, gallic acid, resveratrol, and curcumin, suppressed osteoclast differentiation via the activation of AMPK. These results suggest that AMPK inhibits RANKL-induced osteoclast differentiation by enhancing antioxidant defense system and regulating oxidative stress. AMPK activation by dietary-derived phytochemicals may be effective for the treatment of bone diseases.

Research progress on the role of lncRNA-miRNA networks in regulating adipogenic and osteogenic differentiation of bone marrow mesenchymal stem cells in osteoporosis

Osteoporosis (OP) is characterized by a decrease in osteoblasts and an increase in adipocytes in the bone marrow compartment, alongside abnormal bone/fat differentiation, which ultimately results in imbalanced bone homeostasis. Bone marrow mesenchymal stem cells (BMSCs) can differentiate into osteoblasts and adipocytes to maintain bone homeostasis. Several studies have shown that lncRNAs are competitive endogenous RNAs that form a lncRNA-miRNA network by targeting miRNA for the regulation of bone/fat differentiation in BMSCs; this mechanism is closely related to the corresponding treatment of OP and is important in the development of novel OP-targeted therapies. However, by reviewing the current literature, it became clear that there are limited summaries discussing the effects of the lncRNA-miRNA network on osteogenic/adipogenic differentiation in BMSCs. Therefore, this article provides a review of the current literature to explore the impact of the lncRNA-miRNA network on the osteogenic/adipogenic differentiation of BMSCs, with the aim of providing a new theoretical basis for the treatment of OP.

Understanding the mechanistic potential of plant based phytochemicals in management of postmenopausal osteoporosis

Postmenopausal osteoporosis, an epidemic disorder is defined as a loss in bone mineral density and a greater possibility of fractures in older women. It is a multifactorial disease under the control of various genetic, hormonal, and environmental factors. Insufficiency of estrogen hormone, leads to postmenopausal osteoporosis. Hormone replacement therapy (HRT), despite being the most effective treatment, it is associated with the risk of breast cancer and cardiovascular disorders. This review seeks to compile the most recent information on medicinal plants and natural compounds used to treat and prevent postmenopausal osteoporosis. Furthermore, the origin, chemical constituents and the molecular mechanisms responsible for this therapeutic and preventive effect are also discussed. Literature research was conducted using PubMed, Science direct, Scopus, Web of Science, and Google Scholar. Different plant extracts and pure compounds exerts their antiosteoporotic activity by inhibition of RANKL and upregulation of OPG. RANKL signaling regulates osteoclast formation, characterized by increased bone turnover and osteoprotegrin is a decoy receptor for RANKL thereby preventing bone loss from excessive resorption. In addition, this review also includes the chemical structure of bioactive compounds acting on NFκB, TNF α, RUNX2. In conclusion, we propose that postmenopausal osteoporosis could be prevented or treated with herbal products.

Oxidative stress: A common pathological state in a high-risk population for osteoporosis

Osteoporosis is becoming a major concern in the field of public health. The process of bone loss is insidious and does not directly induce obvious symptoms. Complications indicate an irreversible decrease in bone mass. The high-risk populations of osteoporosis, including postmenopausal women, elderly men, diabetic patients and obese individuals need regular bone mineral density testing and appropriate preventive treatment. However, the primary changes in these populations are different, increasing the difficulty of effective treatment of osteoporosis. Determining the core pathogenesis of osteoporosis helps improve the efficiency and efficacy of treatment among these populations. Oxidative stress is a common pathological state secondary to estrogen deficiency, aging, hyperglycemia and hyperlipemia. In this review, we divided oxidative stress into the direct effect of reactive oxygen species (ROS) and the reduction of antioxidant enzyme activity to discuss their roles in the development of osteoporosis. ROS initiated mitochondrial apoptotic signaling and suppressed osteogenic marker expression to weaken osteogenesis. MAPK and NF-κB signaling pathways mediated the positive effect of ROS on osteoclast differentiation. Antioxidant enzymes not only eliminate the negative effects of ROS, but also directly participate in the regulation of bone metabolism. Additionally, we also described the roles of proinflammatory factors and HIF-1α under the pathophysiological changes of inflammation and hypoxia, which provided a supplement of oxidative stress-induced osteoporosis. In conclusion, our review showed that oxidative stress was a common pathological state in a high-risk population for osteoporosis. Targeted oxidative stress treatment would greatly optimize the therapeutic schedule of various osteoporosis treatments.

Recent Trends in Hydroxyapatite Supplementation for Osteoregenerative Purposes

Bone regeneration has gained attention in the biomedical field, which has led to the development of materials and synthesis methods meant to improve osseointegration and cellular bone activity. The properties of hydroxyapatite, a type of calcium phosphate, have been researched to determine its advantages for bone tissue engineering, particularly its biocompatibility and ability to interact with bone cells. Recently, the advantages of utilizing nanomolecules of hydroxyapatite, combined with various substances, in order to enhance and combine their characteristics, have been reported in the literature. This review will outline the cellular and molecular roles of hydroxypatite, its interactions with bone cells, and its nano-combinations with various ions and natural products and their effects on bone growth, development, and bone repair.

Combining dual-targeted liquid metal nanoparticles with autophagy activation and mild photothermal therapy to treat metastatic breast cancer and inhibit bone destruction

Although mild photothermal therapy (mild-PTT) avoids treatment bottleneck of the traditional PTT, the application of mild-PTT in deep and internal tumors is severely restricted due to thermal resistance, limited irradiation area and penetration depth. In addition, bone resorption caused by tumor colonization in distal bone tissue exacerbates tumor progression. Here, a strategy was developed for the treatment of bone metastasis and alleviation of bone resorption, which was based on liquid metal (LM) nanoparticle to resist thermal resistance induced by mild-PTT via autophagy activation. Briefly, LM and autophagy activator (Curcumin, Cur) were loaded into zeolitic imidazolate framework-8 (ZIF-8), which was then functionalized with hyaluronic acid/alendronate (CLALN). CLALN exhibited good photothermal performance, drug release ability under acidic environment, specifical recognition and aggregation at bone metastasis sites. CLALN combined with mild-PPT dramatically inhibited tumor progress by inducing the impaired autophagy and reduced the expression of programmed cell death ligand 1 (PD-L1) protein triggered by mild-PTT, resisting thermal resistance and alleviating the immunosuppression. Besides, CLALN combined with mild-PPT effectively alleviated osteolysis compared with only CLALN or mild-PPT. Our experiments demonstrated that this multi-functional LM-based nanoparticle combined with autophagy activation provided a promising therapeutic strategy for bone metastasis treatment. STATEMENT OF SIGNIFICANCE: Due to the limited light penetration, photothermal therapy (PTT) has limited inhibitory effect on tumor cells colonized in the bone. In addition, nonspecific heat diffusion of PTT may accidentally burn normal tissues and damage peripheral blood vessels, which can block the accumulation of drugs in deep tumors. Here, a multifunctional liquid metal based mild-PTT delivery system is designed to inhibit tumor growth and bone resorption by modulating the bone microenvironment and activating autophagy "on demand". It can overcome the treatment bottleneck of traditional PTT and improve the treatment effect of mild-PTT by resisting photothermal resistance and immune suppression. In addition, it also exhibits favorable heat/acid-responsive drug release performance and can specifically target tumor cells at the site of bone metastases.

Dual targeted zeolitic imidazolate framework nanoparticles for treating metastatic breast cancer and inhibiting bone destruction

Tumor bone metastasis is still difficult to cure despite the development of various treatment strategies. Drug delivery systems can improve the poor biological distribution of anticancer drugs in tumors. But only a very small number of nanoparticles can cross the physiological barrier to reach the tumor. In addition, the progression of bone metastasis is influenced by tumor cells, osteoclasts and bone matrix. To address these problems, a bone and tumor dual targeted nanocarrier was developed by utilizing NF-κB inhibitor loaded into zeolitic imidazolate framework-8 (ZIF-8) (CZ), which was then coated with hyaluronic acid/alendronate (HA/ALN). The CZ prepared by two-step method had high loading capacity, and the loading efficiency of Cur was to be 47.55 ± 4.03%. HA/ALN functionalization avoided explosive release of reagents and improved the stability of nanoparticles. The dual targeted ZIF-8 nanoparticle (CZ@HA/ALN) had a pH-triggered drug release performance, which effectively inhibited breast cancer cells growth and osteoclastogenesis in vitro. Uptake experiments showed that the conjugation of ALN with HA did not affect targeting ability of HA. Moreover, HA/ALN functionalized nanoparticles were more aggregated at bone metastasis sites than HA functionalized nanoparticles. CZ@HA/ALN could block the PD-1 immune check point, leading to Raw 264.7 cells differentiation into anti-tumor macrophage rather than osteoclast. The antitumor experiments in vivo exhibited that the dual targeted ZIF-8 nanoparticle effectively inhibited bone resorption and tumor progress, thereby improving the bone microenvironment. Therefore, this single but versatile nanoparticle provided a promising therapeutic scheme for bone metastasis treatment.

Effects of Resveratrol, Curcumin and Quercetin Supplementation on Bone Metabolism—A Systematic Review

Phenolic compounds are natural phytochemicals that have recently reported numerous health benefits. Resveratrol, curcumin, and quercetin have recently received the most attention among these molecules due to their documented antioxidant effects. The review aims to investigate the effects of these molecules on bone metabolism and their role in several diseases such as osteopenia and osteoporosis, bone tumours, and periodontitis. The PubMed/Medline, Web of Science, Google Scholar, Scopus, Cochrane Library, and Embase electronic databases were searched for papers in line with the study topic. According to an English language restriction, the screening period was from January 2012 to 3 July 2022, with the following Boolean keywords: (“resveratrol” AND “bone”); (“curcumin” AND “bone”); (“quercetin” AND “bone”). A total of 36 papers were identified as relevant to the purpose of our investigation. The studies reported the positive effects of the investigated phenolic compounds on bone metabolism and their potential application as adjuvant treatments for osteoporosis, bone tumours, and periodontitis. Furthermore, their use on the titanium surfaces of orthopaedic prostheses could represent a possible application to improve the osteogenic processes and osseointegration. According to the study findings, resveratrol, curcumin, and quercetin are reported to have a wide variety of beneficial effects as supplement therapies. The investigated phenolic compounds seem to positively mediate bone metabolism and osteoclast-related pathologies.

Evaluation of quaternization effect on chitosan-HAP composite for bone tissue engineering application

This study attempts to improve the aqueous solubility of chitosan and utilizes it in the fabrication of composites with hydroxyapatite (HAP). The composites were evaluated as a curcumin delivery vehicle for bone regeneration. The chitosan was modified by quaternization, with a quaternization degree of 5 % for low quaternized chitosan (LQC) and 11 % for high quaternized chitosan (HQC). The modified chitosan, at alkaline pH 11, facilitated in situ HAP growth and formed LQC-HAP and HQC-HAP composites. The quaternization weakens intermolecular hydrogen bonds, facilitates interaction with the apatite precursor ions and promotes the growth of HAP. The modification significantly improved drug encapsulation (2.6 fold) but at the cost of a slight decrease in mechanical strength and increase in drug release. The in vitro studies with human osteoblast-like MG-63 cells established that the curcumin-loaded composites, LQC-HAP-C and HQC-HAP-C are biocompatible, encourage proliferation and promote a 2-fold increase in calcium mineralization over drug-free composites. The study exemplifies the reciprocity between quaternization degree and drug load/release properties and also illustrates that the magnitude of the latter reflects bioactivity. Thus, the quaternized chitosan-based HAP composite with tailorable bio-physicochemical properties becomes an interesting drug delivery system in bone regeneration.

Phosphatidylserine liposomes containing curcumin inhibit bone loss in osteoporotic rats: A possible synergy through a common signaling pathway

The present study aimed to investigate the effect of phosphatidylserine liposomes containing curcumin (PSLs-Cur) on the development of osteoporosis induced by glucocorticoids (GCs) in the rat model. PSL-Cur, phosphatidylserine (PSL), curcumin (Cur), and alendronate (AL) drugs as a positive control were administrated orally to evaluate the beneficial effects of 3-week treatments on osteoporotic rats. The biochemical and biomechanical properties of bone parameters as well as gene expression were evaluated in treated rats. Moreover, histomorphometric examinations were performed on the bone tissues of the animals. The results revealed that PSL-Cur oral administration caused a significant improvement in serum markers, mechanical strength, and OPG gene expression rather than PSL or Cur administration in osteoporotic rats. Also, PSL-Cur significantly increased the thickness and volume of cortical and trabecular bone mass in comparison with the untreated osteoporotic group. The results of this study indicated that PSL-Cur had a more inhibitory effect on bone loss induced by GCs compared to AL standard drug. Our findings suggested that PSL-loaded Cur may be an appropriate alternative therapy for glucocorticoid-induced osteoporosis. PRACTICAL APPLICATIONS: Osteoporosis is one of the most serious metabolic chronic diseases that causes fragile bone due to decreased mineral density and microarchitectural deterioration in humans. The osteoprotective effects of curcumin and phosphatidylserine, as a food spice and supplementary diet, respectively, have been shown, previously. However, the low bioavailability of curcumin (Cur) due to its poor absorption, rapid metabolism, and fast systemic elimination, limits its benefits. This deficit can be modified with phosphatidylserine liposome (PSL) formulation that facilitates the gastrointestinal delivery of Cur. Moreover, PSL is known as an osteoprotective agent that may make synergy effect with Cur against GC-induced osteoporosis. In this study, daily oral administration of phosphatidylserine liposomes containing curcumin (PSL-Cur) for 3 weeks, considerably improved biochemical, biomechanical, and gene expression of bone parameters in the treated animals subjected to osteoporosis. PSL-Cur can significantly increase the thickness and volume of cortical and trabecular bone mass as well as the mechanical bone strength in animals. Experimental findings proposed PSL-Cur consumption as a proper and safe supplementary medication in the controlling of bone loss in patients with a high risk of osteoporosis.

Efficacy of nanomicelle curcumin, Nigella sativa oil, and their combination on bone turnover markers and their safety in postmenopausal women with primary osteoporosis and osteopenia: A triple-blind randomized controlled trial

Literature supports the potential effects of nanomicelle curcumin and Nigella sativa on the amelioration of osteoporosis, a health concern of postmenopausal women. This study aimed to evaluate the impacts of nanomicelle curcumin (CUR), Nigella sativa oil (NS), and their combination on bone turnover biomarkers and assess their safety. This triple-blind randomized controlled trial was performed on 120 postmenopausal women aged 50-65 with primary osteoporosis or osteopenia. The subjects were randomly allocated to receive microcrystalline cellulose (placebo), 80 mg of CUR, 1000 mg of NS, or their combination (CUR-NS) for 6 months. All patients were also treated with alendronate (70 mg) and calcium (500 mg), vitamin D (400 IU) supplements. The serum levels of alkaline phosphatase (ALP), osteocalcin (OC), and osteopontin (OP) were measured at the baseline and after the intervention. For safety assessment, the hepatic enzyme levels of aspartate transaminase and alanine transaminase as well as serum urea and creatinine were evaluated. ALP levels were significantly reduced in the NS (p = .029) and CUR-NS (p = .015) groups compared with those in the placebo. After adjustment for the covariates, this effect was still significant in the CUR-NS group (p = .004). The OC levels were decreased in the placebo, CUR, and NS groups, and the OP concentration also was attenuated in all groups through the trial. However, the intergroup differences were not significant for both biomarkers. Evaluating the key renal metabolites and hepatic enzyme levels indicated no toxicity of the administered doses. This study reveals the beneficial effects of CUR-NS on the improvement of some bone turnover biomarkers. These compounds seem to be safe at the current dosage for supplementation in postmenopausal women.

HO-1 in Bone Biology: Potential Therapeutic Strategies for Osteoporosis

Osteoporosis is a prevalent bone disorder characterized by bone mass reduction and deterioration of bone microarchitecture leading to bone fragility and fracture risk. In recent decades, knowledge regarding the etiological mechanisms emphasizes that inflammation, oxidative stress and senescence of bone cells contribute to the development of osteoporosis. Studies have demonstrated that heme oxygenase 1 (HO-1), an inducible enzyme catalyzing heme degradation, exhibits anti-inflammatory, anti-oxidative stress and anti-apoptosis properties. Emerging evidence has revealed that HO-1 is critical in the maintenance of bone homeostasis, making HO-1 a potential target for osteoporosis treatment. In this Review, we aim to provide an introduction to current knowledge of HO-1 biology and its regulation, focusing specifically on its roles in bone homeostasis and osteoporosis. We also examine the potential of HO-1-based pharmacological therapeutics for osteoporosis and issues faced during clinical translation.

Herbal Preparation (Bromelain, Papain, Curcuma, Black Pepper) Enhances Mineralization and Reduces Glucocorticoid-Induced Osteoporosis in Zebrafish

Natural foods with antioxidant properties, such as curcuma, papain, bromelain and black pepper, have been indicated as a potential natural therapeutic approach against osteoporosis. Zebrafish are an excellent animal model to study the effects of herbal preparations on osteogenesis and bone metabolism, both in physiological and in pathological conditions. Our study was aimed at evaluating whether curcuma-bromelain-papain-pepper herbal preparation (CHP) administered in embryos and adult fish is capable of promoting bone wellness in physiological and osteoporotic conditions. The effect of CHP has been studied in embryonic osteogenesis and glucocorticoid-induced osteoporosis (GIOP) in an adult fish model in which drug treatment induces a bone-loss phenotype in adult scales very similar to that which characterizes the bones of human patients. CHP prevented the onset of the osteoporotic phenotype in the scales of GIOP in adult zebrafish, with the osteoblastic and osteoclastic metabolic activity maintaining unaltered. CHP is also able to attenuate an already established GIOP phenotype, even if the alteration is in an advanced phase, partially restoring the normal balance of the bone markers alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) and stimulating anabolic reparative processes. The results obtained indicated CHP as a potential integrative antioxidant therapy in human bone-loss diseases.

Polyphenols-loaded electrospun nanofibers in bone tissue engineering and regeneration

Bone is a complex structure with unique cellular and molecular process in its formation. Bone tissue regeneration is a well-organized and routine process at the cellular and molecular level in humans through the activation of biochemical pathways and protein expression. Though many forms of biomaterials have been applied for bone tissue regeneration, electrospun nanofibrous scaffolds have attracted more attention among researchers with their physicochemical properties such as tensile strength, porosity, and biocompatibility. When drugs, antibiotics, or functional nanoparticles are taken as additives to the nanofiber, its efficacy towards the application gets increased. Polyphenol is a versatile green/phytochemical small molecule playing a vital role in several biomedical applications, including bone tissue regeneration. When polyphenols are incorporated as additives to the nanofibrous scaffold, their combined properties enhance cell attachment, proliferation, and differentiation in bone tissue defect. The present review describes bone biology encompassing the composition and function of bone tissue cells and exemplifies the series of biological processes associated with bone tissue regeneration. We have highlighted the molecular mechanism of bioactive polyphenols involved in bone tissue regeneration and specified the advantage of electrospun nanofiber as a wound healing scaffold. As the polyphenols contribute to wound healing with their antioxidant and antimicrobial properties, we have compiled a list of polyphenols studied, thus far, for bone tissue regeneration along with their in vitro and in vivo experimental biological results and salient observations. Finally, we have elaborated on the importance of polyphenol-loaded electrospun nanofiber in bone tissue regeneration and discussed the possible challenges and future directions in this field.

The effect of nanomicelle curcumin supplementation and Nigella sativa oil on the expression level of miRNA-21, miRNA-422a, and miRNA-503 gene in postmenopausal women with low bone mass density: A randomized, triple-blind, placebo-controlled clinical trial with factorial design

This study aimed to investigate the effect of nanomicelle curcumin (CUR), Nigella sativa oil (NS), and CUR and NS on the plasma levels of miR-21, miR-422a, and miR-503 expression in postmenopausal women with low bone mass density (BMD). This randomized, triple-blind, placebo-controlled clinical trial with a factorial design was conducted on 120 postmenopausal women from the integrated healthcare system, Tabriz-Iran. The BMD was determined using dual-energy X-ray absorptiometry (DEXA). Women were randomly divided into four groups of 30 participants: (a) CUR (80 mg) and placebo of NS, (b) NS (1,000 mg) and placebo of CUR, (c) CUR (80 mg) and NS (1,000 mg), and (d) both placebos (containing microcrystalline cellulose). The plasma level of miRNA-21, miRNA-422a, and miRNA-503 was determined by qRT-PCR. The expression level of miRNAs at the baseline was similar. At the end of the intervention, only the expression level of miRNA-21 changed statistically significantly between the four groups (p = .037) and between the NS and placebo groups (p = .005). Also, its expression in the two groups receiving NS (p = .037) and NS-CUR (p = .043) was significantly increased. NS and NS-CUR supplementation can increase the expression level of miRNA-21 in postmenopausal women with low bone density, and bring perspective to further studies of the target.

Bioactivity and Delivery Strategies of Phytochemical Compounds in Bone Tissue Regeneration

Plant-derived secondary metabolites represent a reservoir of phytochemicals for regenerative medicine application because of their varied assortment of biological properties including anti-oxidant, anti-inflammatory, antibacterial, and tissue remodeling properties. In addition, bioactive phytochemicals can be easily available, are often more cost-effective in large-scale industrialization, and can be better tolerated compared to conventional treatments mitigating the long-lasting side effects of synthetic compounds. Unfortunately, their poor bioavailability and lack of long-term stability limit their clinical impact. Nanotechnology-based delivery systems can overcome these limitations increasing bioactive molecules’ local effectiveness with reduction of the possible side effects on healthy bone. This review explores new and promising strategies in the area of delivery systems with particular emphasis on solutions that enhance bioavailability and/or health effects of plant-derived phytochemicals such as resveratrol, quercetin, epigallocatechin-3-gallate, and curcumin in bone tissue regeneration.

Experimental and clinical reports on anti-inflammatory, antioxidant, and immunomodulatory effects of Curcuma longa and curcumin, an updated and comprehensive review

Curcuma longa (C. longa) or turmeric is a plant with a long history of use in traditional medicine, especially for treating inflammatory conditions C. longa and its main constituent, curcumin (CUR), showed various pharmacological effects such as antioxidant and anti-microbial properties. The updated knowledge of anti-inflammatory, antioxidant, and immunomodulatory effects of C. longa and CUR is provided in this review article. Pharmacological effects of C. longa, and CUR, including anti-inflammatory, antioxidant, and immunomodulatory properties, were searched using various databases and appropriate keywords until September 2020. Various studies showed anti-inflammatory effects of C. longa and CUR, including decreased white blood cell, neutrophil, and eosinophil numbers, and its protective effects on serum levels of inflammatory mediators such as phospholipase A2 and total protein in different inflammatory disorders. The antioxidant effects of C. longa and CUR were also reported in several studies. The plant extracts and CUR decreased malondialdehyde and nitric oxide levels but increased thiol, superoxide dismutase, and catalase levels in oxidative stress conditions. Treatment with C. longa and CUR also improved immunoglobulin E (Ig)E, pro-inflammatory cytokine interleukin 4 (IL)-4, transforming growth factor-beta, IL-17, interferon-gamma levels, and type 1/type 2 helper cells (Th1)/(Th2) ratio in conditions with disturbance in the immune system. Therefore C. longa and CUR showed anti-inflammatory, antioxidant, and immunomodulatory effects, indicating a potential therapeutic effect of the plant and its constituent, CUR, for treating of inflammatory, oxidative, and immune dysregulation disorders.

Curcumin inhibits the migration of osteoclast precursors and osteoclastogenesis by repressing CCL3 production

Background

Curcumin can inhibit the osteoclastogenesis and the migration of several cells including macrophages. Osteoclast precursors (OCPs) are known to exist as bone marrow-derived macrophages (BMMs). This study aims to explore whether curcumin can prevent the fusion and differentiation of OCPs to mature osteoclasts by inhibiting OCP migration.

Methods

In this study, we investigated the role of curcumin in regulating the production of several chemokines (CCL2, CCL3 and CX3CL1) and the migration of OCPs by ELISA, Western blotting and Transwell assays. Furthermore, we explored the role of curcumin in the chemokines-related osteoclastogenesis using pharmacological intervention and virus infection, and used ovariectomized (OVX) mice (osteoporosis model) to explore the effect of curcumin on the production of specific chemokine in vivo.

Results

The results showed that curcumin significantly reduced the production of CCL3 in OCPs. Moreover, curcumin-inhibited the migration of OCPs was not affected by CCR1 (Receptor of CCL3) overexpression. Remarkably, curcumin-reduced osteoclastogenesis was significantly reversed by CCL3 addition, while CCR1 overexpression did not increase the osteoclastogenesis in the presence of curcumin. Furthermore, in vivo assays also showed that curcumin significantly reduced the production of CCL3 in OCPs in the trabecular bone of OVX mice.

Conclusions

In conclusion, curcumin prevents the migration of OCPs by reducing CCL3 production, ultimately inhibiting the formation of mature osteoclasts. Therefore, our study provides the clues for improving the clinical strategies of osteoporosis, dental implantation or orthodontic treatment.

Bone-Specific Metabolism of Dietary Polyphenols in Resorptive Bone Diseases

SCOPE

Curcumin prevents bone loss in resorptive bone diseases and inhibits osteoclast formation, a key process driving bone loss. Curcumin circulates as an inactive glucuronide that can be deconjugated in situ by bone's high β-glucuronidase (GUSB) content, forming the active aglycone. Because curcumin is a common remedy for musculoskeletal disease, effects of microenvironmental changes consequent to skeletal development or disease on bone curcumin metabolism are explored.

METHODS AND RESULTS

Across sexual/skeletal development or between sexes in C57BL/6 mice ingesting curcumin (500 mg kg-1 ), bone curcumin metabolism and GUSB enzyme activity are unchanged, except for >twofold higher (p < 0.05) bone curcumin-glucuronide substrate levels in immature (4-6-week-old) mice. In ovariectomized (OVX) or bone metastasis-bearing female mice, bone substrate levels are also >twofold higher. Aglycone curcumin levels tend to increase proportional to substrate such that the majority of glucuronide distributing to bone is deconjugated, including OVX mice where GUSB decreases by 24% (p < 0.01). GUSB also catalyzes deconjugation of resveratrol and quercetin glucuronides by bone, and a requirement for the aglycones for anti-osteoclastogenic bioactivity, analogous to curcumin, is confirmed.

CONCLUSION

Dietary polyphenols circulating as glucuronides may require in situ deconjugation for bone-protective effects, a process influenced by bone microenvironmental changes.

Curcumin Protects Osteoblasts From Oxidative Stress-Induced Dysfunction via GSK3β-Nrf2 Signaling Pathway

Osteoblasts dysfunction, induced by oxidative stress (OS), is one of major pathological mechanisms for osteoporosis. Curcumin (Cur), a bioactive antioxidant compound, isolated from Curcumin longa L, was regarded as a strong reactive oxygen species (ROS) scavenger. However, it remains unveiled whether Cur can prevent osteoblasts from OS-induced dysfunction. To approach this question, we adopted a well-established OS model to investigate the preventive effect of Cur on osteoblasts dysfunction by measuring intracellular ROS production, cell viability, apoptosis rate and osteoblastogenesis markers. We showed that the pretreatment of Cur could significantly antagonize OS so as to suppress endogenous ROS production, maintain osteoblasts viability and promote osteoblastogenesis. Inhibiting Glycogen synthase kinase (GSK3β) and activating nuclear factor erythroid 2 related factor 2 (Nrf2) could significantly antagonize the destructive effects of OS, which indicated the critical role of GSK3β-Nrf2 signaling. Furthermore, Cur also abolished the suppressive effects of OS on GSK3β-Nrf2 signaling pathway. Our findings demonstrated that Cur could protect osteoblasts against OS-induced dysfunction via GSK3β-Nrf2 signaling and provide a promising way for osteoporosis treatment.

Curcumin suppresses osteogenesis by inducing miR-126a-3p and subsequently suppressing the WNT/LRP6 pathway

Curcumin, a natural phenolic biphenyl compound derived from the plant Curcuma longa, modulates multiple steps of carcinogenesis partly by affecting the expression of miRNAs. Interestingly, cancer development shares many of the same signalling pathways with bone formation. Reduced bone mass creates favourable conditions for tumor metastasis. However, the effects and mechanism of curcumin on bone formation and osteogenesis are relatively unknown and controversial. We demonstrated that curcumin inhibited osteogenesis of human adipose-derived mesenchymal stem cells (hADSCs) in a concentration-dependent manner. In hADSCs, curcumin modulates the expression of a series of miRNAs, including miR-126a-3p, during osteogenesis. Overexpression or inhibition of miR-126a-3p is required for the effect of curcumin on osteogenesis. Further investigation indicated that miR-126a-3p directly targets and inhibits LRP6 through binding to its 3’-UTR, and then blocks WNT activation. Our findings suggest that the use of curcumin as an anti-tumor agent may lead to decreased bone mass through the suppression of osteogenesis. Knowing whether the long-term or high doses use of curcumin will cause decreased bone mass and bone density, which might increase the potential threat of tumor metastasis, also requires a neutral assessment of the role of curcumin in both regulating bone formation and bone absorption.

Beta-Glucuronidase Catalyzes Deconjugation and Activation of Curcumin-Glucuronide in Bone

The biological basis for documented in vivo bone-protective effects of turmeric-derived curcumin is unclear since curcumin is barely detectable in serum, being rapidly conjugated to form what is thought to be an inactive glucuronide. Studies were therefore undertaken to test the postulate that antiresorptive effects of curcumin require deconjugation within bone to form the bioactive aglycone and that β-glucuronidase (GUSB), a deconjugating enzyme expressed by hematopoietic marrow cells, facilitates this site-specific transformation. Consistent with this postulate, aglycone, but not glucuronidated, curcumin inhibited RANKL-stimulated osteoclastogenesis, a key curcumin target in bone. Aglycone curcumin, expressed relative to total curcumin, was higher in bone marrow than in serum of curcumin-treated C57BL/6J mice, while remaining a minor component. Ex vivo, under conditions preventing further metabolism of the unstable aglycone, the majority of curcumin-glucuronide delivered to marrow in vivo was hydrolyzed to the aglycone, a process that was inhibited by treatment with saccharolactone, a GUSB inhibitor, or in mice having reduced (C3H/HeJ) or absent (mps/mps) GUSB activity. These findings suggest that curcumin, despite low systemic bioavailability, may be enzymatically activated (deconjugated) within GUSB-enriched bone to exert protective effects, a metabolic process that could also contribute to bone-protective effects of other highly glucuronidated dietary polyphenols.

Comparison between curcumin and all-trans retinoic acid in the osteogenic differentiation of mouse bone marrow mesenchymal stem cells

The use of bone marrow mesenchymal stem cells (BMSCs) has great potential in cell therapy, particularly in the orthopedic field. BMSCs represent a valuable renewable cell source that have been successfully utilized to treat damaged skeletal tissue and bone defects. BMSCs can be induced to differentiate into osteogenic lineages via the addition of inducers to the growth medium. The present study examined the effects of all-trans retinoic acid (ATRA) and curcumin on the osteogenic differentiation of mouse BMSCs. Morphological changes, the expression levels of the bone-associated gene markers bone morphogenetic protein 2, runt-related transcription factor and osterix during differentiation, an in vitro mineralization assay, and changes in osteocalcin expression revealed that curcumin supplementation promoted the osteogenic differentiation of BMSCs. By contrast, the application of ATRA increased osteogenic differentiation during the early stages, but during the later stages, it decreased the mineralization of differentiated cells. In addition, to the best of our knowledge, the present study is the first to examine the effect of curcumin on the osteogenic potency of mouse embryonic fibroblasts (MEFs) after reprogramming with human lim mineralization protein (hLMP-3), which is a positive osteogenic regulator. The results revealed that curcumin-supplemented culture medium increased hLMP-3 osteogenic potency compared with that of MEFs cultured in the non-supplemented medium. The present results demonstrate that enrichment of the osteogenic culture medium with curcumin, a natural osteogenic inducer, increased the osteogenic differentiation capacity of BMSCs as well as that of MEFs reprogrammed with hLMP-3.

Curcumin in tissue engineering: A traditional remedy for modern medicine

Curcumin is the principal polyphenolic compound present in turmeric with broad applications in tissue engineering and regenerative medicine. It has some important inherent properties with the potential to facilitate tissue healing, including anti-inflammatory, anti-oxidant, and antibacterial activities. Therefore, curcumin has been used for the treatment of various damaged tissues, especially wound injuries. There are different forms of curcumin, among which nano-formulations are of a great importance in regenerative medicine. It is also important to design sophisticated delivery systems for controlled/localized delivery of curcumin to the target tissues and organs. Although there are many reports on the advantages of this compound, further research is required to fully explore its clinical usage. The review describes the physicochemical and biological properties of curcumin and the current state of the evidence on its applications in tissue engineering. © 2018 BioFactors, 45(2):135-151, 2019.

Dose-response assessment of chemically modified curcumin in experimental periodontitis

BACKGROUND

CMC2.24, a novel tri-ketonic chemically modified compound based on natural di-ketonic curcumin, has been shown to reduce bone loss and inflammatory mediators in experimental periodontitis, however, a potential dose-response relationship was not determined. The purpose of this study was to assess the effects of different doses of CMC2.24 on inflammation and bone resorption in vivo and also to describe on the effects of CMC2.24 on macrophage response.

METHODS

CMC2.24 was administered daily to animals for 28 days by oral gavage, at the following doses: 0 (control), 1, 3, 10, and 30 mg/kg of body weight. Experimental periodontitis was induced by injections of lipopolysaccharide (LPS) into the gingival tissues. Outcomes assessed were bone resorption, detection of tartrate-resistant acid phosphatase, and determination of gene expression. In vitro, macrophages (RAW264.7) were treated with different concentrations of CMC2.24: 1, 3, 10, and 30 μM and then subjected to different activation stimuli. Gene expression, phagocytic activity, production of reactive oxygen species (ROS) and cytokine production were evaluated.

RESULTS

CMC2.24 inhibited bone resorption, osteoclastogenesis, and tumor necrosis factor (TNF)-α expression in vivo. These beneficial responses reached maximum levels at a dose of 1 mg/kg, i.e. no dose-dependent effect. In vitro, CMC2.24 reduced the production of TNF-α and interleukin-10, inhibited phagocytic activity and stimulated production of ROS. A dose-dependent effect was observed only for ROS production.

CONCLUSION

Low doses of CMC2.24 (1 mg/kg/day) administered orally were sufficient to significantly inhibit alveolar bone resorption associated with the experimental periodontal disease; whereas in vitro macrophage inflammatory gene expression and phagocytosis were reduced, whereas production of ROS was stimulated.

Combination therapy of curcumin and alendronate modulates bone turnover markers and enhances bone mineral density in postmenopausal women with osteoporosis

OBJECTIVE

This study evaluated the effects of combination therapy of curcumin and alendronate on BMD and bone turnover markers in postmenopausal women with osteoporosis.

SUBJECTS AND METHODS

In a randomized, double-blind trial study, 60 postmenopausal women were divided into three groups: control, alendronate, and alendronate + curcumin. Each group included 20 patients. Total body, total hip, lumbar spine and femoral neck BMDs were measured by dual-energy X-ray absorptiometry (DXA) at baseline and after 12 months of therapy. Bone turnover markers such as bone-specific alkaline phosphatase (BALP), osteocalcin and C-terminal cross-linking telopeptide of type I collagen (CTx) were measured at the outset and 6 months later.

RESULTS

Patients in the control group suffered a significant decrease in BMD and increased bone turnover markers at the end of study. The group treated with only alendronate showed significantly decreased levels of BALP and CTx and increased levels of osteocalcin compared to the control group. The alendronate group also showed significant increases in the total body, total hip, lumbar spine and femoral neck BMDs at the end of study compared to the control group. In the curcumin + alendronate group, BALP and CTx levels decreased and osteocalcin levels increased significantly at the end of study compared to the control and alendronate groups. BMD indexes also increased in four areas significantly at the end of study compared to the control and alendronate groups.

CONCLUSION

The combination of curcumin and alendronate has beneficial effects on BMD and bone turnover markers among postmenopausal women with osteoporosis. Arch Endocrinol Metab. 2018;62(4):438-45.

Dehydrodiconiferyl Alcohol Inhibits Osteoclast Differentiation and Ovariectomy-Induced Bone Loss through Acting as an Estrogen Receptor Agonist

Estrogen deficiency after menopause increases bone loss by activating RANKL-induced osteoclast differentiation. Dehydrodiconiferyl alcohol (DHCA), a lignan originally isolated from Cucurbita moschata, has been thought to be a phytoestrogen based on its structure. In this study, we tested whether DHCA could affect RANKL-induced osteoclastogenesis in vitro and ovariectomy-induced bone loss in vivo. In RAW264.7 cells, DHCA inhibited RANKL-induced differentiation of osteoclasts. Consistently, expression of the six osteoclastogenic genes induced by RANKL was down-regulated. DHCA was also shown to suppress the NF-κB and p38 MAPK signaling pathways by activating AMPK. Data from transient transfection assays suggested that DHCA might activate the estrogen receptor signaling pathway. Effects of DHCA on RANKL-induced osteoclastogenesis were reduced when cells were treated with specific siRNA to ERα, but not to ERβ. Interestingly, DHCA was predicted from molecular docking simulation to bind to both ERα and ERβ. Indeed, data from an estrogen receptor competition assay revealed that DHCA acted as an agonist on both estrogen receptors. In the ovariectomized (Ovx) mouse model, DHCA prevented Ovx-induced bone loss by inhibiting osteoclastogenesis. Taken together, our results suggest that DHCA may be developed as an efficient therapeutic for osteoporosis by regulating osteoclastogenesis through its estrogenic effects.

Effects of Curcumin on Bone Loss and Biochemical Markers of Bone Turnover in Patients with Spinal Cord Injury

BACKGROUND

Osteoporosis is one of the most common problems of patients with spinal cord injuries (SCIs). The current study aimed to evaluate the antiosteoporotic effects of curcumin on densitometry parameters and biomarkers of bone turnovers among patients with SCI.

MATERIALS AND METHODS

The current controlled clinical trial was conducted among 100 patients with SCI referred to an outpatient clinic of rehabilitation in Ilam City, Iran, in 2013-2015. The intervention group received 110/mg/kg/day curcumin for 6 months and the control group received placebo. Bone mineral density (BMD) was measured in all patients. The level of procollagen type I N-terminal propeptide, serum carboxy-terminal telopeptide of type I collagen, osteocalcin, and bone-specific alkaline phosphates were compared before and after study.

RESULTS

BMD indicators of lumbar, femoral neck, and total hip in the control group significantly decreased compared with the beginning of study. However, in the curcumin group, a significant increase was observed in BMD indicators of lumbar, femoral neck, and hip at the end of study compared with the beginning. There was also a significant difference between interventional and control groups for the mean BMD of femoral neck and hip at the end of study (0.718 ± 0.002 g/cm² vs. 0.712 ± 0.003 g/cm² and 0.742 ± 0.031 g/cm² vs. 0.692 ± 0.016 g/cm², respectively).

CONCLUSIONS

Curcumin, via modulation of densitometry indices and bone resorption markers, showed inhibitory effects on the process of osteoporosis. Treatment with curcumin was significantly associated with a decrease in the osteoporosis progression and bone turnover markers of patients with SCI after 6 months.

Innovative evaluation of local injective gel of curcumin on the orthodontic tooth movement in rats

Background

Curcumin is the most active compound in turmeric. It can suppress the nuclear factor kappa-light-chain-enhancer of activated B cells pathway and prevent the osteoclastogenesis procedure. This study aimed to be the first to evaluate the effect of curcumin on the rate of orthodontic tooth movement (OTM).

Materials and Methods

Forty rats were used as follows in each group: (1) negative control: Did not receive any appliance or injection; (2) positive control: received 0.03 cc normal saline and appliance; (3) gelatin plus curcumin (G): Received 0.03 cc hydrogel and appliance; and (4) chitosan plus curcumin (Ch): Received 0.03 cc hydrogel and appliance. They were anesthetized and closed nickel-titanium coil springs were installed between the first molars and central incisors unilaterally as the orthodontic appliance. After 21 days, the rats were decapitated, and the distance between the first and second molars was measured by a leaf gauge. Howship's lacunae, blood vessels, osteoclast-like cells, and root resorption lacunae were evaluated in the histological analysis. Data were analyzed by one-way ANOVA, Tukey's test, and t-test (P < 0.05 consider significant).

Results

No significant difference was found in OTM between groups delivered orthodontic forces. Curcumin inhibited root and bone resorption, osteoclastic recruitment, and angiogenesis significantly.

Conclusion

Curcumin had no significant inhibitory effect on OTM. While it had a significant role on decreasing bone or root resorption (P > 0.05).

Effect of Curcumin on the Diversity of Gut Microbiota in Ovariectomized Rats

Curcumin has been proven to have a weight-loss effect in a menopausal rat model induced by ovariectomy. However, the effects of curcumin on gut microfloral communities of ovariectomized (OVX) rats remains unclear. Here, we used high-throughput 16S rDNA sequencing to explore the effects of curcumin on microbial diversity in the gut of OVX rats. Female Wistar rats were subjected to either ovariectomy or a sham operation (SHAM group). The OVX rats were treated with vehicle (OVX group) or curcumin (CUR group) by oral gavage. After 12-week treatments, the weights of the bodies and uteri of rats were recorded, the levels of estradiol in the serum were assayed by electrochemiluminescence immunoassay (ECLIA). Then, the fragments encompassing V3–V4 16S rDNA hypervariable regions were PCR amplified from fecal samples, and the PCR products of V3–V4 were sequenced on an Illumina MiSeq for characterization of the gut microbiota. Our results showed that, compared to rats in the SHAM group, rats in the OVX group had more weight gain and lower levels of estradiol in the serum, and curcumin could cause significant weight loss in OVX rats but did not increase the levels of estradiol. Sequencing results revealed the presence of 1120, 1114, and 1119 operational taxonomic units (OTUs) found in the SHAM, OVX, and CUR groups, respectively. The percentage of shared OTUs was 86.1603%. Gut microbiota of rats from the SHAM or CUR group had higher levels of biodiversity and unevenness estimations than those from the OVX group. At the phyla level, compared to rats in SHAM group, rats in the OVX group had a higher ratio of phyla Firmicutes and Bacteroidetes in the gut; at the genus level, four differential gut microbiota (Incertae_Sedis, Anaerovorax, Anaerotruncus, and Helicobacter) between SHAM and OVX groups were found, whereas seven differential gut microbiota (Serratia, Anaerotruncus, Shewanella, Pseudomonas, Papillibacter, Exiguobacterium, and Helicobacter) between OVX and CUR groups were found. In conclusion, estrogen deficiency induced by ovariectomy caused changes in the distribution and structure of intestinal microflora in rats, and curcumin could partially reverse changes in the diversity of gut microbiota.

Curcumin Attenuation of Wear Particle-Induced Osteolysis via RANKL Signaling Pathway Suppression in Mouse Calvarial Model

Wear particle-induced chronic inflammation and osteoclastogenesis are two critical factors in the osteolytic process. Curcumin (CUR) is an active compound of the medicinal herb Curcuma longa and has anti-inflammatory and antiosteoclastogenic properties. Our study tested the hypothesis that CUR might attenuate polymethylmethacrylate- (PMMA-) induced inflammatory osteolysis using mouse calvaria osteolysis model in vivo and in vitro. The mice were divided into four groups: phosphate-buffered saline group, CUR, PMMA, and PMMA + CUR groups. Three days before PMMA particle implantation, the mice were intraperitoneally injected with CUR (25 mg/kg/day). Ten days after the operation, the mouse calvaria was harvested for microcomputed tomography, histomorphometry, and molecular biology analysis. As expected, CUR markedly reduced the secretion of tumor necrosis factor-α, interleukin- (IL-) 1β, and IL-6 in the calvarial organ culture. Moreover, CUR suppressed osteoclastogenesis and decreased bone resorption in vivo compared with PMMA-stimulated calvaria. Furthermore, CUR downregulated the osteoclast-specific gene expression and reversed the receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin messenger RNA and protein ratio in PMMA particle-stimulated mice. These results suggest that CUR attenuated PMMA particle-induced inflammatory osteolysis by suppressing the RANKL signaling pathway in the murine calvarium, which could be a candidate compound to prevent and treat AL.

Molecular signaling mechanisms behind polyphenol-induced bone anabolism

For millennia, in the different cultures all over the world, plants have been extensively used as a source of therapeutic agents with wide-ranging medicinal applications, thus becoming part of a rational clinical and pharmacological investigation over the years. As bioactive molecules, plant-derived polyphenols have been demonstrated to exert many effects on human health by acting on different biological systems, thus their therapeutic potential would represent a novel approach on which natural product-based drug discovery and development could be based in the future. Many reports have provided evidence for the benefits derived from the dietary supplementation of polyphenols in the prevention and treatment of osteoporosis. Polyphenols are able to protect the bone, thanks to their antioxidant properties, as well as their anti-inflammatory actions by involving diverse signaling pathways, thus leading to bone anabolic effects and decreased bone resorption. This review is meant to summarize the research works performed so far, by elucidating the molecular mechanisms of action of polyphenols in a bone regeneration context, aiming at a better understanding of a possible application in the development of medical devices for bone tissue regeneration.

Curculactones A and B induced the differentiation of C3H10T1/2 and MC3T3-E1 cells to osteoblasts

Curculactones A and B are rare γ-lactone derivatives obtained from yellow, natural curcumin following γ-irradiation, and are a type of small molecules with a moderate anti-obesity effect. However, the exact role of curculactones A and B in osteoblast differentiation is unknown. In this study, the effects of curculactones A and B on the differentiation of the mesenchymal cell line C3H10T1/2 and pre-osteoblast cell line MC3T3-E1 to osteoblasts were examined. Curculactones A or B could markedly increase the mRNA levels of osteogenic marker genes and alkaline phosphatase (ALP) activity. Collectively, our findings indicate that curculactones A or B induced osteoblast differentiation through osteogenic expression of genes such as distal-less homeobox 5 (Dlx5), runt-related transcription factor 2 (Runx2), ALP, and osteocalcin (OC).

Role of Curcumin in Common Musculoskeletal Disorders: a Review of Current Laboratory, Translational, and Clinical Data

The Indian spice turmeric, in which the active and dominant biomolecule is curcumin, has been demonstrated to have significant medicinal properties, including anti-inflammatory and anti-neoplastic effects. This promise is potentially very applicable to musculoskeletal disorders, which are common causes of physician visits worldwide. Research at the laboratory, translational and clinical levels that supports the use of curcumin for various musculoskeletal disorders, such as osteoarthritis, osteoporosis, musculocartilaginous disorders, and sarcoma is here in comprehensively summarized. Though more phase I-III trials are clearly needed, thus far the existing data show that curcumin can indeed potentially be useful in treatment of the hundreds of millions worldwide who are afflicted by these musculoskeletal disorders.

Curcumin alleviates glucocorticoid-induced osteoporosis through the regulation of the Wnt signaling pathway

It is known that prolonged glucocorticoid (GC) treatment results in osteoporosis. This study aimed to evaluate the protective effects of curcumin on the bones of rats with dexamethasone (DXM)-induced osteoporosis. In the present study, rats were administered DXM for 60 days to induce osteoporosis, and they were then treated with curcumin (100 mg/kg/day) for a further 60 days. H&E staining was used to observe the pathological changes in the femurs. Serum osteocalcin levels and collagen-type I fragments (CTX) were examined as bone metabolism markers. The results revealed that treatment with curcumin attenuated DXM-induced bone injury in femurs, increased the serum levels of osteocalcin and decreased the levels of CTX. In addition, in in vitro experiments, primary rat osteoblasts treated with curcumin at 0.5, 1 and 2 µM were exposed to 100 nM DXM. An MTT assay was used to determine the proliferative ability of the cells. Alkaline phosphatase activity, and the mRNA expression levels of runt-related transcription factor 2 (Runx2), osterix, osteocalcin, collagen, type 1, alpha 1 (Col1A1) and osteonectin were detected to assess transcription factor-associated osteogenic differentiation. The mRNA and protein expression levels of osteoprotegerin (OPG) and receptor activator for nuclear factor-kappa B ligand (RANKL) were detected to assess cytokine-associated osteoclastogenesis. The results demonstrated that curcumin prevented the DXM-induced inhibition of the proliferative ability of the osteoblasts in a dose-dependent manner. In addition, curcumin upregulated the mRNA expression levels of transcription factors that favor osteoblast differentiation and increased the ratio of OPG to RANKL. Moreover, the effects of curcumin on the Wnt signaling pathway were also investigated. RT-qPCR and western blot analysis demonstrated that the Wnt signaling pathway, which was inhibited by DXM, was re-activated upon treatment with curcumin. Immunofluorescence staining revealed that curcumin restored the intranuclear staining of β-catenin in the DXM-stimulated osteoblasts. Collectively, our data demonstrate that curcumin may be a potential therapeutic agent for the treatment of GC-induced osteoporosis.

Curcumin Supplementation Decreases Intestinal Adiposity Accumulation, Serum Cholesterol Alterations, and Oxidative Stress in Ovariectomized Rats

The aim of this study was to investigate the potential of curcumin oral supplementation (50 and 100 mg/Kg/day, for 30 days) in circumventing menopause-associated oxidative stress and lipid profile dysfunctions in a rat ovariectomy (OVX) model. Female Wistar rats were operated and randomly divided into either sham-operated or OVX groups. Sham-operated group (n = 8) and one OVX group (n = 11) were treated with vehicle (refined olive oil), and the other two OVX groups received curcumin at 50 or 100 mg/Kg/day doses (n = 8/group). OVX vehicle-treated animals presented a higher deposition of intestinal adipose tissue as well as increased serum levels of IL-6, LDL, and total cholesterol when compared to sham-operated rats. In addition, several oxidative stress markers in serum, blood, and liver (such as TBARS, carbonyl, reduced-sulphydryl, and nonenzymatic antioxidant defenses) were altered toward a prooxidant status by OVX. Interestingly, curcumin supplementation attenuated most of these parameters to sham comparable values. Thus, the herein presented results show that curcumin may be useful to ameliorate lipid metabolism alterations and oxidative damage associated with hormone deprivation in menopause.

Andrographolide Inhibits Ovariectomy-Induced Bone Loss via the Suppression of RANKL Signaling Pathways

Osteoporosis is a debilitating skeletal disorder with an increased risk of low-energy fracture, which commonly occurs among postmenopausal women. Andrographolide (AP), a natural product isolated from Andrographis paniculata, has been found to have anti-inflammatory, anti-cancer, anti-asthmatic, and neuro-protective properties. However, its therapeutic effect on osteoporosis is unknown. In this study, an ovariectomy (OVX) mouse model was used to evaluate the therapeutic effects of AP on post-menopausal osteoporosis by using micro-computed tomography (micro-CT). Bone marrow-derived osteoclast culture was used to examine the inhibitory effect of AP on osteoclastogenesis. Real time PCR was employed to examine the effect of AP on the expression of osteoclast marker genes. The activities of transcriptional factors NF-κB and NFATc1 were evaluated using a luciferase reporter assay, and the IκBα protein level was analyzed by Western blot. We found that OVX mice treated with AP have greater bone volume (BV/TV), trabecular thickness (Tb.Th), and trabecular number (Tb.N) compared to vehicle-treated OVX mice. AP inhibited RANKL-induced osteoclastogenesis, the expression of osteoclast marker genes including cathepsin K (Ctsk), TRACP (Acp5), and NFATc1, as well as the transcriptional activities of NF-κB and NFATc1. In conclusion, our results suggest that AP inhibits estrogen deficiency-induced bone loss in mice via the suppression of RANKL-induced osteoclastogensis and NF-κB and NFATc1 activities and, thus, might have therapeutic potential for osteoporosis.

Treatment with curcumin alleviates sublesional bone loss following spinal cord injury in rats

This work aimed to investigate the therapeutic effect of curcumin on sublesional bone loss induced by spinal cord injury (SCI) in rats. SCI model in this work was generated in rats by surgical transaction of the cord at the T10-12 level. After the surgery, animals were treated with curcumin (110 mg/kg body mass/day, via oral gavages) for 2 weeks. Treatment of SCI rats with curcumin prevented the reduction of bone mass in tibiae and femurs, preserved bone microstructure including trabecular bone volume fraction, trabecular number, and trabecular thickness in proximal tibiae, and preserved mechanical properties of femoral midshaft. Treatment of SCI rats with curcumin increased osteoblast surface and reduced osteoclast surface in proximal tibiae. Treatment of SCI rats with curcumin increased osteocalcin mRNA expression and reduced mRNA levels of tartrate-resistant acid phosphatase and mRNA ratio of receptor activator of NF-κB ligand/osteoprotegerin in distal femurs. Treatment of SCI rats with curcumin reduced serum and femoral levels of thiobarbituric acid reactive substances. Treatment of SCI rats with curcumin had no significant effect on serum 25(OH)D, but enhanced mRNA and protein expression of vitamin D receptor (VDR) in distal femurs. Treatment of SCI rats with curcumin enhanced mRNA levels of Wnt3a, Lrp5, and ctnnb1 and upregulated protein expression of β-catenin in distal femurs. In conclusions, treatment with curcumin abated oxidative stress, activated VDR, and enhanced Wnt/β-catenin pathway, which might explain its beneficial effect against sublesional bone loss following SCI in rats, at least in part.

Selenoproteins and selenium status in bone physiology and pathology

BACKGROUND

Emerging evidence supports the view that selenoproteins are essential for maintaining bone health.

SCOPE OF REVIEW

The current state of knowledge concerning selenoproteins and Se status in bone physiology and pathology is summarized.

MAJOR CONCLUSIONS

Antioxidant selenoproteins including glutathione peroxidase (GPx) and thioredoxin reductase (TrxR), as a whole, play a pivotal role in maintaining bone homeostasis and protecting against bone loss. GPx1, a major antioxidant enzyme in osteoclasts, is up-regulated by estrogen, an endogenous inhibitor of osteoclastogenesis. TrxR1 is an immediate early gene in response to 1α,25-dihydroxyvitamin D3, an osteoblastic differentiation agent. The combination of 1α,25-dihydroxyvitamin D3 and Se generates a synergistic elevation of TrxR activity in Se-deficient osteoblasts. Of particular concern, pleiotropic TrxR1 is implicated in promoting NFκB activation. Coincidentally, TrxR inhibitors such as curcumin and gold compounds exhibit potent osteoclastogenesis inhibitory activity. Studies in patients with the mutations of selenocysteine insertion sequence-binding protein 2, a key trans-acting factor for the co-translational insertion of selenocysteine into selenoproteins have clearly established a causal link of selenoproteins in bone development. Se transport to bone relies on selenoprotein P. Plasma selenoprotein P concentrations have been found to be positively correlated with bone mineral density in elderly women.

GENERAL SIGNIFICANCE

A full understanding of the role and function of selenoproteins and Se status on bone physiology and pathology may lead to effectively prevent against or modify bone diseases by using Se.