Analysis of anti-osteoporosis function of chlorogenic acid by gene microarray profiling in ovariectomy rat model

Characterization and preparation of food-derived peptides on improving osteoporosis: A review

Osteoporosis is a systemic bone disease characterized by reduced bone mass and deterioration of the microstructure of bone tissue, leading to an increased risk of fragility fractures and affecting human health worldwide. Food-derived peptides are widely used in functional foods due to their low toxicity, ease of digestion and absorption, and potential to improve osteoporosis. This review summarized and discussed methods of diagnosing osteoporosis, treatment approaches, specific peptides as alternatives to conventional drugs, and the laboratory preparation and identification methods of peptides. It was found that peptides interacting with RGD (arginine-glycine-aspartic acid)-binding active sites in integrin could alleviate osteoporosis, analyzed the interaction sites between these osteogenic peptides and integrin, and further discussed their effects on improving osteoporosis. These may provide new insights for rapid screening of osteogenic peptides, and provide a theoretical basis for their application in bone materials and functional foods.

Osteogenic mechanism of chlorogenic acid and its application in clinical practice

Natural polyphenols may have a role in counteracting oxidative stress, which is associated with aging and several bone-related diseases. Chlorogenic acid (CGA) is a naturally occurring polyphenolic compound formed by the esterification of caffeic and quininic acids with osteogenic, antioxidant, and anti-inflammatory properties. This review discusses the potential of CGA to enhance osteogenesis by increasing the osteogenic capacity of mesenchymal stem cells (MSCs), osteoblast survival, proliferation, differentiation, and mineralization, as well as its ability to attenuate osteoclastogenesis by enhancing osteoclast apoptosis and impeding osteoclast regeneration. CGA can be involved in bone remodeling by acting directly on pro-osteoclasts/osteoblasts or indirectly on osteoclasts by activating the nuclear factor kB (RANK)/RANK ligand (RANKL)/acting osteoprotegerin (OPG) system. Finally, we provide perspectives for using CGA to treat bone diseases.

Secoisolariciresinol diglucoside regulates estrogen receptor expression to ameliorate OVX-induced osteoporosis

OBJECTIVE

Secoisolariciresinol diglucoside (SDG) is a phytoestrogen that has been reported to improve postmenopausal osteoporosis (PMOP) caused by estrogen deficiency. In our work, we aimed to investigate the mechanism of SDG in regulating the expressions of ERs on PMOP model rats.

METHODS

Ovariectomization (OVX) was used to establish PMOP model in rats. The experiment was allocated to Sham, OVX, SDG and raloxifene (RLX) groups. After 12-week treatment, micro-CT was used to detect the transverse section of bone. Hematoxylin and Eosin staining and Safranine O-Fast Green staining were supplied to detect the femur pathological morphology of rats. Estradiol (E2), interleukin-6 (IL-6), bone formation and bone catabolism indexes in serum were detected using ELISA. Alkaline phosphatase (ALP) staining was used to detect the osteogenic ability of chondrocytes. Immunohistochemistry and Western blot were applied to detect the protein expressions of estrogen receptors (ERs) in the femur of rats.

RESULTS

Compared with the OVX group, micro-CT results showed SDG could lessen the injury of bone and improve femoral parameters, including bone mineral content (BMC) and bone mineral density (BMD). Pathological results showed SDG could reduce pathological injury of femur in OVX rats. Meanwhile, SDG decreased the level of IL-6 and regulated bone formation and bone catabolism indexes. Besides, SDG increased the level of E2 and conversed OVX-induced decreased the expression of ERα and ERβ.

CONCLUSION

The treatment elicited by SDG in OVX rats was due to the reduction of injury and inflammation and improvement of bone formation index, via regulating the expression of E2 and ERs.

Comparative Pharmacokinetic Study of 5 Active Ingredients after Oral Administration of Zuogui Pill in Osteoporotic Rats with Different Syndrome Types

Zuogui Pill is a kidney-yin-tonifying formula in traditional Chinese medicine that is widely used to manage osteoporosis with kidney-yin-deficiency in China. Herein, an efficient and accurate high-performance liquid chromatography-tandem mass spectrometry method was developed to determine the concentrations of 5 bioactive compounds in rat plasma following oral administration of Zuogui Pill. Because drug absorption and distribution differ under physiological and pathological conditions, the established method was used to quantify blood components and dynamic change in osteoporotic rats with different syndrome types. Moreover, integrated pharmacokinetic study was conducted to describe the overall pharmacokinetic characteristics of traditional Chinese medicine. The results showed that the absorption, distribution, and metabolism of Zuogui Pill varied widely under different states. The bioavailability of most active components showed significant advantages in osteoporotic rats with kidney-yin-deficiency, which corresponds to the opinion that Zuogui Pill has the effect of nourishing kidney-yin. It is hoped that this finding could interpret the pharmacodynamic substances and mechanism of Zuogui Pill in the treatment of osteoporosis with kidney-yin-deficiency.

GC-MS and LC-TOF-MS profiles, toxicity, and macrophage-dependent in vitro anti-osteoporosis activity of Prunus africana (Hook f.) Kalkman Bark

Osteoporosis affects millions of people worldwide. As such, this study assessed the macrophage-dependent in vitro anti-osteoporosis, phytochemical profile and hepatotoxicity effects in zebrafish larvae of the stem bark extracts of P. africana. Mouse bone marrow macrophages (BMM) cells were plated in 96-well plates and treated with P. africana methanolic bark extracts at concentrations of 0, 6.25, 12.5, 25, and 50 µg/ml for 24 h. The osteoclast tartrate-resistant acid phosphatase (TRAP) activity and cell viability were measured. Lipopolysaccharides (LPS) induced Nitrite (NO) and interleukin-6 (IL-6) production inhibitory effects of P. africana bark extracts (Methanolic, 150 µg/ml) and β-sitosterol (100 µM) were conducted using RAW 264.7 cells. Additionally, inhibition of IL-1β secretion and TRAP activity were determined for chlorogenic acid, catechin, naringenin and β-sitosterol. For toxicity study, zebrafish larvae were exposed to different concentrations of 25, 50, 100, and 200 µg/ml P. africana methanolic, ethanolic and water bark extracts. Dimethyl sulfoxide (0.05%) was used as a negative control and tamoxifen (5 µM) and dexamethasone (40 µM or 80 µM) were positive controls. The methanolic P. africana extracts significantly inhibited (p < 0.001) TRAP activity at all concentrations and at 12.5 and 25 µg/ml, the extract exhibited significant (p < 0.05) BMM cell viability. NO production was significantly inhibited (all p < 0.0001) by the sample. IL-6 secretion was significantly inhibited by P. africana methanolic extract (p < 0.0001) and β-sitosterol (p < 0.0001) and further, chlorogenic acid and naringenin remarkably inhibited IL-1β production. The P. africana methanolic extract significantly inhibited RANKL-induced TRAP activity. The phytochemical study of P. africana stem bark revealed a number of chemical compounds with anti-osteoporosis activity. There was no observed hepatocyte apoptosis in the liver of zebrafish larvae. In conclusion, the stem bark of P. africana is non-toxic to the liver and its inhibition of TRAP activity makes it an important source for future anti-osteoporosis drug development.

Triclosan induced zebrafish immunotoxicity by targeting miR-19a and its gene socs3b to activate IL-6/STAT3 signaling pathway

As a broad-spectrum antibacterial agent, triclosan (TCS) has been confirmed to possess potential immunotoxicity to organisms, but the underlying mechanisms remains unclear. Herein, with the aid of transgenic zebrafish strains Tg (coro1A: EGFP) and Tg (rag2: DsRed), we intuitively observed acute TCS exposure caused the drastic differentiation, abnormal development and distribution of innate immune cells, as well as barriers to formation of adaptive immune T cells. These abnormalities implied occurrence of the cytokine storm, which was further evidenced by expression changes of immune-related genes, and functional biomarkers. Based on transcriptome deep sequencing, target gene prediction and dual luciferase validation, the highly conservative and up-regulated miR-19a was chosen as the research target. Under TCS exposure, miR-19a up-regulation triggered down-regulation of its target gene socs3b, and simultaneously activated the downstream IL-6/STAT3 signaling pathway. Artificial over-expression and knock-down of miR-19a was realized by microinjecting agomir and antagomir, respectively, in 1-2-cell embryos. The miR-19a up-regulation inhibited socs3b expression to activate IL-6/STAT3 pathway, and yielded abnormal changes in the functional cytokine biomarkers, along with the sharp activation of immune responses. These findings disclose the molecular mechanisms regarding TCS-induced immunotoxicity, and offer important theoretical guidance for healthy safety evaluation and disease early warning from TCS pollution.

Chlorogenic acid protects human chondrocyte C28/I2 cells from oxidative stress-induced cell death through activation of autophagy

AIMS

The development of osteoarthritis (OA), the most common form of arthritis, is commonly associated with oxidative stress. Indeed, the lack of antioxidant responses largely increases OA incidence. OA is a leading cause of disability in the elderly, which reduces the quality of life and places high socioeconomic burdens on them. Several polyphenolic compounds, including chlorogenic acid (CGA), have shown cytoprotective effects via their antioxidant activity, but the exact mechanism (s) remain elusive. In this study, we demonstrated how CGA protects human chondrocytes against H₂O₂-induced apoptosis.

MATERIALS AND METHODS

The cytoprotective effect by CGA in 500 μM hydrogen peroxide-treated C28/I2 cells was evaluated by cell viability, TUNEL assay, and Western blotting analyses, and autophagy assessment was further performed by AO and MDC staining and tandem mRFP-GFP fluorescence analyses.

KEY FINDINGS

Treatment of CGA to the human chondrocytes under oxidative stress significantly decreased apoptosis markers, such as cleaved caspase 3 and cleaved PARP, and increased anti-apoptotic marker Bcl-xL and the antioxidant response proteins NRF2 and NF-κB. Furthermore, CGA-dependent activation of antioxidant response proteins NRF2 and NF-κB and its protective effects in chondrocytes depended on autophagy. Indeed, CGA treatment and autophagy induction significantly decreased reactive oxygen species (ROS)-induced apoptosis.

SIGNIFICANCE

CGA exhibited the protective effect to human chondrocyte C28/I2 cells against oxidative stress-induced cell death by activating autophagy. These findings indicate that CGA is a potential therapeutic agent for the development of OA drugs.

Chlorogenic Acid Promotes Osteogenic Differentiation of Human Dental Pulp Stem Cells Through Wnt Signaling

Periodontal disease (PD) is one of the main causes of periodontal bone resorption and tooth loss in adults. How to repair the alveolar bone effectively has always been a challenge. This study was designed to clarify the effects and the underlying molecular mechanisms of chlorogenic acid (CGA) on osteogenic differentiation of human dental pulp stem cells (hDPSCs). In this study, we used CGA to treat hDPSCs. The osteogenic experiment showed that CGA can promote hDPSCs osteogenic differentiation. RNA-Seq and quantitative real-time polymerase chain reaction showed that CGA treatment enhanced the expression of the osteogenesis genes for frizzled-related protein (FRZB) and pyruvate dehydrogenase kinase 4 (PDK4) and inhibit the expression of the osteoclastogenesis genes such as those for asporin (ASPN) and cytokine-like 1 (CYTL1). Western blot analysis showed that besides FRZB, CGA treatment also caused reduction of both active and total β-catenin, while increased the total calcium/calmodulin-dependent kinase II (CamKII), the phosphorylated CamKII (pCamKII) and the phosphorylated cAMP-response element-binding protein (pCREB). Likely, the increased osteogenesis was associated with reduced canonical Wnt/β-catenin signaling but increased noncanonical Wnt/Ca²⁺ signaling. The results suggested that CGA can promote the osteogenic differentiation of hDPSCs by regulating Wnt signaling. These findings will serve as a foundation for further studies on how to repair defective alveolar bone for the patients with PD.

Polo Like Kinase 4 (PLK4) impairs human bone marrow mesenchymal stem cell (BMSC) viability and osteogenic differentiation

Human bone marrow mesenchymal stem cell (hBMSC) viability and osteogenic differentiation play a critical role in bone disorders such as osteoporosis. In the present study, we identified the aberrant PLK4 upregulation in osteoporosis and downregulation in BMSCs during osteogenic differentiation. In isolated hBMSCs, PLK4 overexpression significantly inhibited, whereas PLK4 knockdown promoted cell viability and hBMSC osteogenic differentiation. For molecular mechanism, PLK4 overexpression decreased, whereas PLK4 knockdown increased WNT1 and β-catenin protein levels and the phosphorylation of Smad1/5/8. The Wnt/β-catenin signaling antagonist Dickkopf 1 (DKK1) or the BMP-Smads antagonist LDN193189 dramatically suppressed hBMSC osteoblast differentiation, and partially attenuated the promotive effects of PLK4 knockdown on hBMSC osteogenic differentiation. Altogether, PLK4 overexpression impairs hBMSC viability and osteogenic differentiation potential, possibly through the Wnt/β-catenin signaling and BMP/Smads signaling.

Viburnum opulus L. Juice Phenolic Compounds Influence Osteogenic Differentiation in Human Osteosarcoma Saos-2 Cells

Bone mass loss occurs with a decrease in osteoblast proliferation and differentiation, or the enhancement of bone resorption, which further leads to the impairment of bone mineral density and increase in bone fracture. Recent studies suggest that some phenolic compounds found in food play positive role in bone metabolism. High content of phenolic compounds with potential beneficial effects on bone metabolism have been identified in the Viburnum opulus fruit. The aim of the study was to determine the influence of V. opulus fresh juice (FJ) and juice purified by solid phase extraction (PJ) on osteogenesis processes with osteosarcoma Saos-2 cell lines. V. opulus purified juice revealed stronger potential as an inducer of Saos-2 osteogenic differentiation. Saos-2 cells matrix mineralization was evaluated with alkaline phosphatase (ALP) activity measurement and alizarin red S staining. Gene expression analysis showed the elevation of the mRNA levels of Runt-related transcription factor 2 (RUNX2), ALP, collagen type 1 and osteonectin, whereas the nuclear factor-κB ligand and osteoprotegerin ratio (RANKL/OPG) decreased. Furthermore, V. opulus was able to diminish the secretion of pro-inflammatory cytokines Il6 and TNFα, however had no effect on vascular endothelial growth factor (VEGF). It decreased intracellular oxidative stress and induced DNA repair, but had no effect on the growth inhibition of lactic acid beneficial microorganisms.

Polyphenol-Rich Foods and Osteoporosis

BACKGROUND

Osteoporosis is a metabolic disease affecting the bone mineral density and thus compromise the strength of the bones. Disease prevention through diet is the objective of the study and discussion. Among the several nutrients investigated, the intake of phenols seems to influence bone mineral density by acting as free radical scavengers, preventing oxidation-induced damage to bone cells. In addition, the growing understanding of the bone remodelling process supports the theory that inflammation significantly contributes to the etiopathogenesis of osteoporosis.

METHODS

To provide an overview of current evidence on polyphenol-rich foods and osteoporosis prevention we made a comprehensive review of the literature focusing on the state of art of the topic.

RESULTS

Some polyphenol-rich foods, including olive oil, fruit and vegetable, tea and soy, seem to be beneficial for preventing osteoporosis disease and its progression. The mechanism is still partly unknown and may involve different pathways which include inflammation and other disease reactions.

CONCLUSIONS

However, further research is needed to better understand the mechanisms regulating the molecular interaction between osteoporosis incidence and progression and polyphenol-rich foods. The current evidence suggests that dietary intervention with polyphenol rich foods may be useful to prevent incidence and progression of this condition.

Kaempferol promotes bone formation in part via the mTOR signaling pathway

Previous research indicates that kaempferol (Kae) promotes osteogenesis, but its underlying mechanism of action remains unclear. The present study hypothesized that the osteogenic effects of Kae were mediated through mammalian target of rapamycin (mTOR). To validate this hypothesis, bone marrow mesenchymal stem cells (BMSCs) from ovariectomized (OVX) rats were differentiated into osteoblasts. The bone mineral density and bone microarchitecture of the OVX rats was measured in vivo, while osteogenesis was evaluated in vitro via Alizarin Red S staining and alkaline phosphatase activity measurements in cultured BMSCs. The levels of phosphorylated eukaryotic translation initiation factor 4E‑binding protein 1 (p‑4E/BP1) and phosphorylated ribosomal protein S6 kinase B1 (p‑S6K), and the expression of Runt‑related transcription factor 2 and Osterix, were concurrently quantified by western blot analysis. The data suggested that Kae prevented OVX‑induced osteoporosis in rats by promoting osteoblastogenesis. Furthermore, treatment with Kae in rat BMSCs enhanced mineralization, elevated ALP activity, increased the expression levels of Runx‑2 and Osterix and increased the levels of p‑S6K and decreased the levels of p‑4E/BP1 and, consistent with its ability to promote osteoblast differentiation. In contrast, treatment with rapamycin, an mTOR inhibitor, produced the opposite phenotype. Taken together, these data suggested that the protective effects of Kae in BMSCs and in the OVX rat model resulted from the induction of osteogenesis via mTOR signaling, or at least partially via the regulation of downstream effectors of the mTOR pathway.

Rutin suppresses FNDC1 expression in bone marrow mesenchymal stem cells to inhibit postmenopausal osteoporosis

A previous study revealed that rutin is the main component of Eucommia flavonoids that exerts a protective effect against osteopenia. The bone density and trabecular bone number of osteoporosis model rats can be significantly improved after treatment with rutin. Further study using whole gene expression profiling revealed that FNDC1, a fibronectin type III domain-containing protein, may be a novel bone metabolism-related factor that is decreased in rutin-treated rats. The mechanism underlying the effects of rutin treatment on osteoporosis is important to explore. Micro-CT, western blotting, quantitative PCR, transmission electron microscopy, and Alizarin Red mineralization staining assays were performed to evaluate bone density, FNDC1 expression and autophagy to determine whether FNDC1 might play a significant role in rutin-inhibited trabecular bone loss in rats. FNDC1 expression was high in the osteoporosis group, whereas rutin treatment facilitated FNDC1 downregulation. In addition, rutin promoted bone marrow mesenchymal stem cell autophagy by inhibiting phosphorylated Akt in osteoporosis. In summary, our study shows that rutin could regulate FNCD1 level and autophagy through the Akt/mTOR signaling pathway to provide a novel therapeutic strategy for osteoporosis.

Effects of miR-181a-5p abnormal expression on zebrafish (Danio rerio) vascular development following triclosan exposure

Triclosan (TCS), one of the important bactericides, is widely used in personal care products, and its chronic exposure leads to severe toxic effects on the growth and development of blood vessels in zebrafish (Danio rerio). Herein, we screened out three differentially expressed miRNAs (miR-181a-5p, miR-132-3p and miR-128-3p) by sequencing and qRT-PCR analyses of 4-96-hpf TCS-exposed zebrafish, among which miR-181a-5p was found to regulate many signaling pathways involved in fatty acid biosynthesis and phosphatidylimositol signaling systems. By O-dianisidine staining, TCS-exposure resulted in decreased distribution of red blood cells and induced blood hypercoagulable state and thrombotic effects. Defective subintestinal veins (SIVs), and decreased branching and curvature of blood vessels were observed with increasing TCS-exposure concentrations. After microinjection of miR-181a-5p mimic and inhibitor, zebrafish malformation type and percentage were prominently increased such as distorted SIV vessels along with reduced venation and abnormal branches by ALP staining. Overexpressed miR-181a-5p had a greater effect on development and branching patterns of arteries and veins than its knockdown. By laser confocal microscopy observation, the 72-hpf Tg (flk1: mCherry) zebrafish obviously displayed vascular proliferation and ablation in the miR-181a-5p mimic group. Microinjection of miR-181a-5p mimics and inhibitors led to abnormal expressions (20-50%) of two key target genes (pax2a and vash2) by WISH, and increased malformation percentages (18-45%) by IOD analysis. Overexpression of vash2 led to the inhibitory or promoting effects on the expression of PI3K signaling pathway-related genes, proving that the effect of vash2 on development of blood vessels could be realized by inhibiting PI3K signaling pathway. These observations lay theoretical foundation for deep insight into the molecular mechanisms on TCS-induced cardiovascular diseases.