Hyperglycemia Suppresses RANKL-Induced Osteoclast Differentiation through LXRβ Expression in RAW264.7 Cells

Cnidium officinale Makino: Phytology, Phytochemistry, Toxicology, Pharmacology and Prescriptions (1967-2023)

Cnidium officinale Makino (COM), a perennial herbaceous plant in the Apiaceous family, widely distribute in Eastern Asia and Asia-Temperate. It has a long history application as a traditional medicine for invigorating the blood and removing blood stasis, and also has been employed to diet, pesticide, herbal bathing materials, the cosmetic and skin care industry. However, there has been no associated review of literature in the past half a century (1967-2023). By searching the international authoritative databases and collecting 229 literatures closely related to COM, herewith a comprehensive and systematic review was conducted. The phytology includes plant distribution and botanical characteristics. The phytochemistry covers 8 major categories, 208 compounds in total, and the quantitative determination of 14 monomer compounds, total polyphenols and total flavonoids. The clinical trial in pregnant women and toxic experiments in mice, the pharmacology of 7 aspects and 82 frequently used prescriptions are summarized. It is expected that this paper will provide forward-looking scientific thinking and literature support for the further modern research, development and utilization of COM.

Discovery of Spiro[pyrrolidine-3,3'-oxindole] LXRβ Agonists for the Treatment of Osteoporosis

Osteoclasts have an additional demand for cholesterol compared to normal cells. Liver X receptors (LXRs) are famous for regulation of lipid and cholesterol metabolism. Therefore, we propose that the LXR β agonist can regulate the cholesterol balance in osteoclasts to inhibit osteoclast differentiation. Here, we designed and synthesized a novel LXRβ agonist by introduction of the privileged fragments from anti-osteoporosis agents to the spiro[pyrrolidine-3,3'-oxindole] scaffold which is a novel scaffold of LXR agonists in our previous research. As a result, seven LXRβ agonists inhibited osteoclastogenesis with IC₅₀ values ranging from 0.078 to 0.36 μM. Especially, the most potent LXRβ agonist B9 significantly inhibited RANKL-induced osteoclast differentiation and bone resorption in vitro and in vivo. Furthermore, B9 selectively activated LXRβ to promote intracellular cholesterol exclusion in osteoclasts and reduce extracellular cholesterol uptake and thereby inhibited osteoclast production. This study provides a new strategy to develop LXRβ agonists for osteoporosis.

Hyponatremia elicits gene expression changes driving osteoclast differentiation and functions

Growing evidence indicates that chronic hyponatremia represents a significant risk for bone loss, osteoporosis, and fractures in our aging population. Our prior studies on a rat model of the syndrome of inappropriate antidiuretic hormone secretion indicated that chronic hyponatremia causes osteoporosis by increasing osteoclastic bone resorption, thereby liberating stored sodium from bone. Moreover, studies in RAW264.7 pre-osteoclastic cells showed increased osteoclast formation and resorptive activity in response to low extracellular fluid sodium ion concentration (low [Na+]). These studies implicated a direct stimulatory effect of low [Na+] rather than the low osmolality on cultured osteoclastic cells. In the present cellular studies, we explored gene expression changes triggered by low [Na+] using RNA sequencing and gene ontology analysis. Results were confirmed by mouse whole genome microarray, and quantitative RT-PCR. Findings confirmed gene expression changes supporting osteoclast growth and differentiation through stimulation of receptor activator of nuclear factor kappa-B ligand (RANKL), and PI3K/Akt pathways, and revealed additional pathways. New findings on low [Na+]-induced upregulation of lysosomal genes, mitochondrial energy production, MMP-9 expression, and osteoclast motility have supported the significance of osteoclast transcriptomic responses. Functional assays demonstrated that RANL and low [Na+] independently enhance osteoclast functions. Understanding the molecular mechanisms of hyponatremia-induced osteoporosis provides the basis for future studies identifying sodium-sensing mechanisms in osteoclasts, and potentially other bone cells, and developing strategies for treatment of bone fragility in the vulnerable aging population most affected by both chronic hyponatremia and osteoporosis. ISSUE SECTIONS: Signaling Pathways; Parathyroid, Bone, and Mineral Metabolism.

Association of the Sp1 binding site and -1997 promoter variations in COL1A1 with osteoporosis risk: The application of meta-analysis and bioinformatics approaches offers a new perspective for future research

As a complex disease, osteoporosis is influenced by several genetic markers. Many studies have examined the link between the Sp1 binding site +1245 G > T (rs1800012) and -1997 G > T (rs1107946) variations in the COL1A1 gene with osteoporosis risk. However, the findings of these studies have been contradictory; therefore, we performed a meta-analysis to aggregate additional information and obtain increased statistical power to more efficiently estimate this correlation. A meta-analysis was conducted with studies published between 1991-2020 that were identified by a systematic electronic search of the Scopus and Clarivate Analytics databases. Studies with bone mineral density (BMD) data and complete genotypes of the single-nucleotide variations (SNVs) for the overall and postmenopausal female population were included in this meta-analysis and analyzed using the R metaphor package. A relationship between rs1800012 and significantly decreased BMD values at the lumbar spine and femoral neck was found in individuals carrying the "ss" versus the "SS" genotype in the overall population according to a random effects model (p < 0.0001). Similar results were also found in the postmenopausal female population (p = 0.003 and 0.0002, respectively). Such findings might be an indication of increased osteoporosis risk in both studied groups in individuals with the "ss" genotype. Although no association was identified between the -1997 G > T and low BMD in the overall population, those individuals with the "GT" genotype showed a higher level of BMD than those with "GG" in the subgroup analysis (p = 0.007). To determine which transcription factor (TF) might bind to the -1997 G > T in COL1A1, 45 TFs were identified based on bioinformatics predictions. According to the GSE35958 microarray dataset, 16 of 45 TFs showed differential expression profiles in osteoporotic human mesenchymal stem cells relative to normal samples from elderly donors. By identifying candidate TFs for the -1997 G > T site, our study offers a new perspective for future research.

The Effect of Type 2 Diabetes on Bone Biomechanics

PURPOSE OF REVIEW

There is ample evidence that patients with type 2 diabetes (T2D) have increased risk of fracture even though they have normal or high bone mineral density. As a result, poor bone quality is suggested to contribute to skeletal fragility in this population. Thus, our goal was to conduct a comprehensive literature review to understand how bone quality components are altered in T2D and their effects on bone biomechanics and fracture risk.

RECENT FINDINGS

T2D does affect bone quality via alterations in bone microarchitecture, organic matrix, and cellular behavior. Further, studies indicate that bone biomechanical properties are generally deteriorated in T2D, but there are few reports in patients. Additional work is needed to better understand molecular and cellular mechanisms that contribute to skeletal fragility in T2D. This knowledge can contribute to the development of improved diagnostic tools and drug targets to for improved quality of life for those with T2D.

SIRT1 suppresses high glucose and palmitate-induced osteoclast differentiation via deacetylating p66Shc

Findings concerning the role of diabetes mellitus (DM) in osteoclast differentiation are contradictory in vivo and in vitro. Sirtuin 1 (SIRT1) can inhibit RANKL-induced osteoclastogenesis and deacetylate p66Shc suppress its phosphorylation in high glucose (HG)-stimulated human umbilical vein endothelial cells. This study aimed to investigate the role and mechanism of SIRT1 in DM-related osteoclast differentiation. Osteoclast precursors were cultured with HG and palmitate (PA), with or without resveratrol/sirtinol. TRAP staining was used to evaluate osteoclast formation. The expression of SIRT1, RANK, RANKL, OPG, NFATc1, TRAP, c-fos, p66Shc, phospho-p66Shc (S36), phospho-NF-κBp65 (p-p65), and IκB was determined by real-time PCR or western blotting. Lysine acetylation of p66Shc was assayed by immunoprecipitation. Reactive oxygen species (ROS) production was analyzed by DCFH-DA fluorescence. p66Shc siRNA and PDTC were used to confirm the mechanism of SIRT1 in osteoclastogenesis. We found HG and PA enhanced osteoclast differentiation, decreased SIRT1 and OPG expression, and increased levels of RANK, RANKL, NFATc1, TRAP, and c-fos. Upregulation of SIRT1 by resveratrol inhibited HG- and PA-induced osteoclast differentiation, whereas sirtinol further enhanced it. Resveratrol suppressed lysine acetylation and S36 phosphorylation of p66Shc, ROS production, and NF-κB activation induced by HG and PA, while sirtinol boosted these processes. p66Shc siRNA abrogated HG- and PA-induced ROS production and NF-κB activation. In addition, p66Shc siRNA and PDTC greatly suppressed the expression of RANK and RANKL induced by HG and PA. In conclusion, this study confirms the role of DM in osteoclast differentiation in vitro. SIRT1 suppresses HG- and PA-induced osteoclast differentiation via p66Shc/ROS/NF-κB signaling.

Characteristics of Bone Strength and Metabolism in Type 2 Diabetic Model Nagoya Shibata Yasuda Mice

We evaluated the suitability of Nagoya Shibata Yasuda (NSY) mice as an animal model for examining the influence of a glucose metabolism disorder on bone integrity, using Institute of Cancer Research (ICR) mice as controls. We selected six NSY and ICR mice each that were matched for weight, and measured serum glucose levels, serum insulin levels, and conducted an oral glucose tolerance test. Histological sections of the femurs of both mouse lines were prepared, and the bone strength, mass, and microstructure of the femur were compared, along with bone metabolism. Serum glucose levels were significantly higher in the NSY mice than in the control mice, but body weight and serum insulin levels did not differ between the groups. Bone mass, microstructure, and strength of the femur, and bone metabolism were lower in the NSY mice than in the control mice. In the cortical bone of the femur in the NSY mice, several parts were not stained with eosin, demonstrating a strong negative correlation between serum glucose levels and bone mineral density; however, there was a negative correlation between serum glucose levels and bone metabolic markers. The bone turnover rate in the NSY mice was decreased by hyperglycemia, resulting in a thinner and shorter femur, reduced cortical and trabecular areas, and lower bone mass compared to those of the control mice. Collectively, these results suggest deteriorated bone strength of the femur in NSY mice, serving as a useful model for studying the link between glucose metabolism and bone integrity.

Transcriptional activation of glucose transporter 1 in orthodontic tooth movement-associated mechanical response

The interplay between mechanoresponses and a broad range of fundamental biological processes, such as cell cycle progression, growth and differentiation, has been extensively investigated. However, metabolic regulation in mechanobiology remains largely unexplored. Here, we identified glucose transporter 1 (GLUT1)—the primary glucose transporter in various cells—as a novel mechanosensitive gene in orthodontic tooth movement (OTM). Using an in vivo rat OTM model, we demonstrated the specific induction of Glut1 proteins on the compressive side of a physically strained periodontal ligament. This transcriptional activation could be recapitulated in in vitro cultured human periodontal ligament cells (PDLCs), showing a time- and dose-dependent mechanoresponse. Importantly, application of GLUT1 specific inhibitor WZB117 greatly suppressed the efficiency of orthodontic tooth movement in a mouse OTM model, and this reduction was associated with a decline in osteoclastic activities. A mechanistic study suggested that GLUT1 inhibition affected the receptor activator for nuclear factor-κ B Ligand (RANKL)/osteoprotegerin (OPG) system by impairing compressive force-mediated RANKL upregulation. Consistently, pretreatment of PDLCs with WZB117 severely impeded the osteoclastic differentiation of co-cultured RAW264.7 cells. Further biochemical analysis indicated mutual regulation between GLUT1 and the MEK/ERK cascade to relay potential communication between glucose uptake and mechanical stress response. Together, these cross-species experiments revealed the transcriptional activation of GLUT1 as a novel and conserved linkage between metabolism and bone remodelling.

A glucose-transporting protein is key to helping teeth respond to orthodontic implants, say researchers in China. Implants apply forces to teeth and the periodontal ligament (PDL) that holds them in place, causing bone to grow on one side and be absorbed into the body on the other. Yanheng Zhou and co-workers at Peking University in Beijing showed that GLUT1, a protein that transports glucose through cell membranes, was greatly upregulated in rat, mouse and human PDL cells subjected to mechanical force. They also injected some of the mice with a GLUT1 inhibitor and found that the treatment greatly decreased the distance moved by the teeth. This could be attributed to a decline in the activity of cells that break down bone tissue and a failure in signalling channels when GLUT1 is inhibited.