Diabetes-induced Osteoporosis Research Articles

Diabetes-induced osteoporosis. Review

The literature review highlights the impact of osteoporosis on the health of the population. The attention is focused on one of the secondary osteoporosis types, diabetes‑induced osteoporosis (DIO). The mechanisms of bone mass loss are highlighted, description is given to the interaction between osteoblasts and osteoclasts, the role of immune cells in the process of osteoporosis under conditions of hyperglycemia. The risk factors of DIO in type 1 and type 2 diabetes mellitus (DM) and the causes of bone mineral density reduction are described. Special attention is focused on the phenomenon of immunoporosis, which can lead to the creation and further development of new approaches to the targeted treatment of osteoporosis.
 High incidence of fractures in patients with type 1 diabetes (DM1) is caused by both negative hyperglycemia effects on the bone architectonics, and effects of hypoglycemia that raises the risk of falls. Along with hyperglycemic‑mediated processes in bone, the state of the microcirculatory bed, muscle tissue, and peripheral nervous system is important in DIO pathogenesis. In‑depth study of immunoporosis will contribute to the creation of new and development of existing approaches to the targeted osteoporosis treatment. Literature data show that incidence of any fractures’ is increased in three times in DM1 patients. The correlation between hyperglycemia, insulin, insulin‑like growth factor, anabolic hormones and C‑peptide with the development of diabetes‑induced osteoporosis has been revealed. Despite the lower date of fractures in DM2, comparing to the DM1, the main reasons for fractures include the high risk of falls, accumulation of advanced glycosylation end‑products, the low level of bone tissue metabolism, as well as obesity and insulin resistance. The effects of hypoglycemic drugs on fracture risk and bone mineral density have been characterized. Metformin and glucagon‑like peptide‑1 receptor agonists have the most favorable fracture safety profile. It has been suggested that bisphosphonates, androgens, and receptor activator of nuclear factor‑kappa B ligand (RANKL) inhibitor may be the most effective drugs against osteoporosis in patients with DM.

Text Mining and Drug Discovery Analysis: A Comprehensive Approach to Investigate Diabetes-Induced Osteoporosis.

Purpose: Osteoporosis (OP) and diabetes are prevalent diseases in orthopedic and endocrinology departments, with OP potentially arising as a complication of diabetes. However, the mechanism underlying diabetes-induced osteoporosis (DOP) remains enigmatic, and drug discovery in this domain is restricted, hindering research into the DOP's etiology and treatment. With the ultimate goal of preventing OP in diabetic patients, the objective of this study is to mine the genes and pathways linked to DOP using bioinformatics and databases. Method: The present study employed text mining as the initial approach to retrieve genes commonly associated with diabetes and OP. Subsequently, functional annotation was conducted to investigate the roles and functionalities. In order to explore the interactions between proteins relevant to DOP, we constructed protein-protein interaction (PPI) networks. Furthermore, to obtain key genes and candidate drugs for DOP treatment, we conducted drug-gene interaction (DGI) analysis, complemented by a thorough examination of transcriptional factors (TFs)-miRNA co-regulation. Results: The results through text mining revealed 110 genes that are commonly associated with both diabetes and OP. Subsequent enrichment analysis narrowed down the list to 95 symbols that were involved in PPI analysis. After DGI analysis, we identified 7 genes targeted by 11 drugs, which represent candidates for treating DOP. Conclusion: This study unveils ANDECALIXIMAB, SILTUXIMAB, OLOKIZUMAB, SECUKINUMAB, and IXEKIZUMAB as promising potential drugs for DOP treatment, demonstrating the significance of utilizing text mining and pathway analysis to investigate disease mechanisms and explore existing therapeutic options.

An update on the role of antihyperglycemic agents in diabetoporosis

Abstract Diabetes mellitus is a chronic disorder that progresses globally at an alarming rate. The impact of this disorder is severe as it deteriorates the quality of life due to its associated diseases such as kidney disease, cardiovascular disease, obesity, and neurological disorders and also disturbs bone metabolism. One of the major complications of diabetes is osteoporosis, which is frequently brought on by diabetes. Bone abnormalities and a higher risk of fractures are linked to both type type-1 diabetes and type-2 diabetes and hence diabetes is regarded as one of the risk factors for the occurrence of osteoporosis. In view of this, there is a need to assess the therapeutic role of hypoglycemic agents in the treatment of osteoporosis. Glucagon-like peptide-1 (GLP-1) agonist, a hypoglycemic class could be a novel and promising drug target in the management of osteoporosis due to its additional role in the bone remodeling process. It has also been reported that GLP-1 agonists can increase bone mineral density, improve bone quality, and prevent fractures in diabetic patients. This review highlights the recent findings by which antidiabetic medications are used in the treatment of diabetes-induced osteoporosis and also gives an insight into its pathophysiology and possible mechanisms that are involved in the treatment of diabetes-induced osteoporosis. However, more research is required to fully understand the therapeutic role and unique mechanism of GLP-1 agonists in the bone remodeling process.

VK2 promotes osteogenic differentiation of BMSCs against high glucose exposure via modulation of intracellular oxidative stress.

Diabetic osteoporosis (DOP) has gradually gained public attention. The clinical manifestations of DOP include bone mass loss, bone microstructural damage, and increased bone fragility. Intracellular reactive oxygen species (ROS) production was significantly increased under high glucose (HG) conditions, with deleterious effects on bone mesenchymal stem cells (BMSCs) proliferation and osteogenic differentiation. Vitamin K2 (VK2) has been demonstrated to promote bone formation both in vitro and in vivo. However, its potential role in diabetes-induced osteoporosis remains unelucidated. This study aims to verify whether VK2 treatment could relieve the deleterious effects of high glucose on BMSCs and delay the progression of osteoporosis. The results revealed that the HG environment downregulated the expression of osteogenesis-related proteins. Correspondingly, VK2 treatment reversed the osteogenic phenotype of BMSCs under HG conditions. In addition, using an established diabetes-induced osteoporosis rat model, we found that VK2 administration could restore bone mass and microstructure. In conclusion, our results provide a promising therapeutic option in the clinical treatment of DOP.

Efficacy of a Novel Pleiotropic MMP-Inhibitor, CMC2.24, in a Long-Term Diabetes Rat Model with Severe Hyperglycemia-Induced Oral Bone Loss.

CMC2.24, a novel 4-(phenylaminocarbonyl)-chemically-modified-curcumin, is a pleiotropic MMP-Inhibitor of various inflammatory/collagenolytic diseases including periodontitis. This compound has demonstrated efficacy in host modulation therapy along with improved resolution of inflammation in various study models. The objective of current study is to determine the efficacy of CMC2.24 in reducing the severity of diabetes, and its long-term role as an MMP-inhibitor, in a rat model. Twenty-one adult male Sprague-Dawley rats were randomly distributed into three groups: Normal (N), Diabetic (D) and Diabetic+CMC2.24 (D+2.24). All three groups were orally administered vehicle: carboxymethylcellulose alone (N, D), or CMC2.24 (D+2.24; 30mg/kg/day). Blood was collected at 2-months and 4-months' time-point. At completion, gingival tissue and peritoneal washes were collected/analyzed, and jaws examined for alveolar bone loss by micro-CT. Additionally, sodium hypochlorite(NaClO)-activation of human-recombinant (rh) MMP-9 and its inhibition by treatment with 10μM CMC2.24, Doxycycline, and Curcumin were evaluated. CMC2.24 significantly reduced the levels of lower-molecular-weight active-MMP-9 in plasma. Similar trend of reduced active-MMP-9 was also observed in cell-free peritoneal and pooled gingival extracts. Thus, treatment substantially decreased conversion of pro- to actively destructive proteinase. Normalization of the pro-inflammatory cytokine (IL-1ß, resolvin-RvD1), and diabetes-induced osteoporosis was observed in presence of CMCM2.24. CMC2.24 also exhibited significant anti-oxidant activity by inhibiting the activation of MMP-9 to a lower-molecular-weight (82kDa) pathologically active form. All these systemic and local effects were observed in the absence of reduction in severity of hyperglycemia. CMC2.24 reduced activation of pathologic active-MMP-9, normalized diabetic osteoporosis, and promoted resolution of inflammation but had no effect on the hyperglycemia in diabetic rats. This study also highlights the role of MMP-9 as an early/sensitive biomarker in the absence of change in any other biochemical parameter. CMC2.24 also inhibited significant activation of pro-MMP-9 by NaOCl (oxidant) adding to known mechanisms by which this compound treats collagenolytic/inflammatory diseases including periodontitis.

S-Equol enhances osteoblastic bone formation and prevents bone loss through OPG/RANKL via the PI3K/Akt pathway in streptozotocin-induced diabetic rats.

This study aimed to explore whether S-Equol delays diabetes-induced osteoporosis and the molecular mechanisms underlying its therapeutic effects. Thirty-five male Sprague-Dawley rats were randomized into five groups. The diabetic osteoporosis (DOP) group and three S-Equol treatment groups were intraperitoneally injected with streptozotocin (STZ) to develop a DOP model. After the 12-week intervention, bone transformation indicators were detected using an enzyme-linked immunosorbent assay kit; bone mineral density (BMD) and bone microstructure were obtained using dual-energy X-ray absorptiometry and microCT; morphological changes in the bone tissue were investigated using HE staining; bone morphogenetic proteins were detected using immunohistochemical staining. ROS17/2.8 cells were cultured in vitro, and Cell Counting Kit-8 was used to test the protective effects of S-Equol in osteoblastic cells in a high-fat and high-glucose environment. Furthermore, the expression of osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL), estrogen receptor β(ERβ), phosphorylated Akt (pAKT)/protein kinase B (AKT), and osteocalcin (OC) in bone tissue and ROS17/2.8 cells was assessed using reverse transcription polymerase chain reaction (RT-PCR) and western blotting. To determine whether ERβ and phosphatidylinositol 3' -kinase (PI3K)/AKT signaling pathways are involved in the process, LY294002 (PI3K signaling pathway inhibitor) and small interfering RNA targeting ERβ mRNA (si-ERβ) were used to verify the function of the ERβ-mediated PI3K/AKT pathway in this process. After the 12-week intervention, S-Equol enhanced BMD, improved bone microarchitecture in DOP rats (P < 0.05), and improved markers of bone metabolism (P < 0.05). In vitro, 10-6 mmol/L S-Equol was selected to significantly protect osteoblasts from high- and high-glucose environments (P < 0.05). Gene expression of OPG, ERβ, pAKT/AKT, and OC was upregulated compared to the DOP group, and RANKL was downregulated compared to the DOP group (P < 0.05) both in bone tissue and osteoblastic cells. The promotion of OPG and pAKT/AKT is mediated by LY294002 and siERβ. S-Equol binds to ERβ to regulate OPG/RANKL via the PI3K/AKT pathway and improve DOP. Our results demonstrate the potential role of S-Equol in the treatment of DOP by targeting ERβ. Thus, S-Equol may have the potential to be an adjuvant drug for treating DOP.

Impaired vertebral development following hyperglycemic induction and recovery in Danio rerio

Diabetes mellitus is a chronic metabolic condition that can result in numerous comorbidities, including diabetes‐induced osteoporosis. Regardless of age, diabetics are at an increased risk of bone fracture as a result of decreased bone quality and mass. In the Clark lab we have previously established a glucose immersion model of hyperglycemic induction in larval zebrafish (Danio rerio). Zebrafish are a viable model to study diabetic complications as they glucoregulate similar to mammals and have robust regenerative abilities previously shown to regenerate pancreatic b‐cells, peripheral nerves, cardiac muscle, and fins. Given the negative impact diabetes has on bones, we hypothesized that hyperglycemia would negatively impact vertebral development; but given zebrafish’s ability to regenerate we also hypothesized that after a recovery from hyperglycemia, the vertebrae would have a similar phenotype to controls. Larval zebrafish were incubated in 120 mM glucose solution (treatment), or egg water (control), for seven days beginning five days post fertilization (dpf). To assess vertebral development following a recovery period, zebrafish were placed in normal egg water for an additional ten days, and control fish were kept in egg water for an equal amount of time. Using alizarin red to visualize mineralized vertebrae after 7‐day incubation in glucose solution (12dpf) showed a reduced percentage of zebrafish with any mineralized vertebrae compared to controls (****p&lt;0.0001). The vertebrae that were present following treatment had significantly less area of mineralized centra compared to controls (****p&lt;0.0001). This suggests that hyperglycemia negatively impacted initial vertebral development. Following recovery (22 dpf), the treatment fish had significantly reduced total body length than controls (****p&lt;0.0001). Treatment fish continued to have significantly less mineralized centra area (****p&lt;0.0001) and significantly increased area of intervertebral domain (****p&lt;0.0001) when compared to size matched controls. This suggests that the vertebrae of treatment fish are mineralizing and expanding into the intervertebral domain at a slower rate than controls. Additionally, glucose‐treated fish had significantly reduced percentage of fish with mineralized neural (****p&lt;0.0001) and hemal (****p&lt;0.0001) arches present on their vertebra compared to controls. These results suggest a dramatic impairment of vertebral development that extends beyond both treatment and recovery periods, leading us to believe the reduced mineralization may be responsible for the behavioral deficits through reductions in their ability to swim. Furthermore, our results may indicate profound effects of gestation and childhood diabetes on the skeletal development of children. Future experiments will investigate osteoblast and chondrocyte populations following hyperglycemic induction and recovery to elucidate the mechanisms that result in impaired vertebral mineralization. This discovery would guide further research into potential therapeutics for diabetes‐induced osteoporosis.

N,N-Dimethylformamide inhibits high glucose-induced osteoporosis via attenuating MAPK and NF-κB signalling

AimsThe role of N,N-dimethylformamide (DMF) in diabetes-induced osteoporosis (DM-OS) progression remains unclear. Here, we aimed to explore the effect of DMF on DM-OS development.MethodsDiabetic models of mice, RAW 264.7 cells, and bone marrow macrophages (BMMs) were established by streptozotocin stimulation, high glucose treatment, and receptor activator of nuclear factor-κB ligand (RANKL) treatment, respectively. The effects of DMF on DM-OS development in these models were examined by micro-CT analysis, haematoxylin and eosin (H&E) staining, osteoclast differentiation of RAW 264.7 cells and BMMs, H&E and tartrate-resistant acid phosphatase (TRAP) staining, enzyme-linked immunosorbent assay (ELISA) of TRAP5b and c-terminal telopeptides of type 1 (CTX1) analyses, reactive oxygen species (ROS) analysis, quantitative reverse transcription polymerase chain reaction (qRT-PCR), Cell Counting Kit-8 (CCK-8) assay, and Western blot.ResultsThe established diabetic mice were more sensitive to ovariectomy (OVX)-induced osteoporosis, and DMF treatment inhibited the sensitivity. OVX-treated diabetic mice exhibited higher TRAP5b and c-terminal telopeptides of type 1 (CTX1) levels, and DMF treatment inhibited the enhancement. DMF reduced RAW 264.7 cell viability. Glucose treatment enhanced the levels of TRAP5b, cathepsin K, Atp6v0d2, and H+-ATPase, ROS, while DMF reversed this phenotype. The glucose-increased protein levels were inhibited by DMF in cells treated with RANKL. The expression levels of antioxidant enzymes Gclc, Gclm, Ho-1, and Nqo1 were upregulated by DMF. DMF attenuated high glucose-caused osteoclast differentiation by targeting mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signalling in BMMs.ConclusionDMF inhibits high glucose-induced osteoporosis by targeting MAPK and NF-κB signalling.Cite this article: Bone Joint Res 2022;11(4):200–209.

Formononetin attenuates osteoclast differentiation and calcium loss by mediating transcription factor AP-1 in type I diabetic mice.

Formononetin (FMN) has been reported as a prospective antiosteoporotic medication. However, the antiosteoporotic properties of FMN are still unclear in a mouse model with diabetes-induced osteoporosis.An osteoporotic or osteopenic mouse model with type I diabetes mellitus (T1DM) was established using streptozotocin (40 mg/kg) injection for 5 consecutive days. After 12 weeks with FMN intragastric administration (0.5, 5, 20 mg/kg), the antiosteoporotic activity of FMN was evaluated in T1DM mice.FMN supplementation effectively improves Ca excretion and trabecular bone degeneration and impedes osteoclast differentiation and function to attenuate hyperglycemia-induced bone deterioration. In addition, FMN inhibited activating protein 1 (AP-1) and osteoclast-specific gene expression, Nfatc1, Ctsk, and TRAP.The administration of FMN has a beneficial effect to attenuate hyperglycemia-induced bone deteriorations, including osteoclastogenesis, trabecular bone, and Ca loss. Our study provided a prospective medication for the treatment of T1DM-related osteopenia or osteoporosis with FMN.

E26 transformation-specific 1 is implicated in the inhibition of osteogenic differentiation induced by chronic high glucose by directly regulating Runx2 expression.

Chronic high glucose (HG) plays a crucial role in the pathogenesis of diabetes-induced osteoporosis by inhibiting the differentiation and proliferation of osteoblasts. This study aims to examine the role of E26 transformation-specific 1 (ETS1) in the inhibition of osteoblast differentiation and proliferation caused by chronic HG, as well as the underlying mechanism. Chronic HG treatment downregulated ETS1 expression and inhibited differentiation and proliferation of MC3T3-E1 cells. Downregulation of ETS1 expression inhibited the differentiation and proliferation of MC3T3-E1 cells under normal glucose conditions, and ETS1 overexpression attenuated the damage to cells exposed to chronic HG. In addition, ETS1 overexpression reversed the decrease in runt-related transcription factor 2 (Runx2) expression in MC3T3-E1 cells treated with chronic HG. Using chromatin immunoprecipitation (ChIP) and luciferase reporter assays, we confirmed that ETS1 directly bound to and increased the activity of the Runx2 promoter. In summary, our study suggested that ETS1 was involved in the inhibitory effect of chronic HG on osteogenic differentiation and proliferation and may be a potential therapeutic target for diabetes-induced osteoporosis.

Bergapten: A review of its pharmacology, pharmacokinetics, and toxicity.

Bergapten is a natural furocoumarin, also known as 5-methoxypsoralen, and its medicinal value has been paid more and more attention. By sorting out the pharmacological literature of bergapten, we found that bergapten has a wide range of pharmacological effects, including neuroprotection, organ protection, anticancer, antiinflammatory, antimicrobial, and antidiabetes effects. However，bergapten has complex impacts on the hepatic metabolic enzyme. Moreover, pharmacokinetic studies showed that bergapten has higher absolute bioavailability and can cross the blood-brain barrier and has a great potential for treating brain disease, but the mechanism needs further clarification to make greater use of its ability to treat brain diseases. Furthermore, the phototoxicity of bergapten combined with ultraviolet light has always been mentioned. In view of its wide range of pharmacological activities, bergapten is expected to be a potential drug candidate for the treatment of diabetes and diabetes-induced osteoporosis, epilepsy, Alzheimer's disease, depression, and cancer. However, further studies are needed to elucidate its molecular mechanisms and targets. The phototoxicity of bergapten as a side effect should be further avoided. On the other hand, the photoactivation of bergapten in the anticancer aspect can be better utilized.

Pharmacological Effects of Fructus Ligustri Lucidi on Neuroinflammation and Exploration of Active Compound Based on the Interaction with CaSR

Background The onset of depression and the lack of effectiveness in antidepressant medication may be related to the overall activation of the neuroinflammatory response. The calcium-sensing receptor (CaSR), widely expressed in various types of cells in the nervous system, participates in inflammatory responses. Our studies had revealed that the extract of Fructus Ligustri Lucidi (FLL) could exert beneficial effects on improving bone metabolism of diabetic rats and mice via acting on renal CaSR. The effects of FLL on neuroinflammation and the role of FLL in protecting from neuropsychiatric diseases remain elusive. The present work aimed to study the pharmacological mechanisms by which FLL and its active compound inhibit neuroinflammation from the view of modulating CaSR. Methods ：Mice were treated with the phenol glycosides extract of FLL for 14 consecutive days before intraperitoneally injected with lipopolysaccharide (LPS) on the 15th day to establish acute model of depression. The allosteric sites of CaSR were predicted and its interaction with phenol glycosides was analyzed by Schördinger Maestro package. After treatment of streptozotocin-induced diabetic mice with ligustroflavone for 8 weeks, calcium balance and bone properties as well as renal CaSR signaling were measured. BV2 microglia cells were incubated with different doses of ligustroflavone before CaSR agonist cinacalcet was added to the medium to stimulate CaSR. The production of inflammatory response, like NLRP3 inflammasome, and the release of IL-1β, MCP-1, and Rantes as well as morphological changes of the cells were detected. Results Pretreatment of mice with the phenol glycosides of FLL inhibited LPS-triggered depression-like behaviors by reducing the release of inflammatory factors and attenuating the neuroinflammation via affecting the CaSR pathway. Phytochemical work clarified the main compounds like ligustroflavone contained in FLL phenol glycosides extract. Docking analysis found that ligustroflavone interacted well with the allosteric site of CaSR and had the potency as CaSR antagonist. Treatment of diabetic mice with ligustroflavone maintained calcium homeostasis by antagonizing CaSR in kidney, consequently protecting from diabetes-induced osteoporosis. Our ongoing study demonstrated that pre-incubation of microglia cells with ligustroflavone significantly inhibited the activation of microglials and repressed the cinacalcet-induced activation of NLRP3 inflammasome signaling and the increase in levels of inflammatory mediators, including cytokines and chemokines, by antagonizing CaSR. Conclusion: FLL exerted beneficial effects on protecting from depressive-like behaviors by suppressing neuroinflammation via acting on CaSR in brain tissue. Ligustroflavone might be a potential active compound as a candidate of CaSR antagonist.

Differential responses of bone to angiotensin II and angiotensin(1-7): beneficial effects of ANG(1-7) on bone with exposure to high glucose.

Osteoporosis, diabetes, and hypertension are common concurrent chronic disorders. This study aimed to explore the respective effects of angiotensin II (ANG II) and angiotensin(1-7) [ANG(1-7)], active peptides in the renin-angiotensin system, on osteoblasts and osteoclasts under high-glucose level, as well as to investigate the osteo-preservative effects of ANG II type 1 receptor (AT1R) blocker and ANG(1-7) in diabetic spontaneously hypertensive rats (SHR). ANG II and ANG(1-7), respectively, decreased and increased the formation of calcified nodules and alkaline phosphatase activity in MC3T3-E1 cells under high-glucose level, and respectively stimulated and inhibited the number of matured osteoclasts and pit resorptive area in RANKL-induced bone marrow macrophages. Olmesartan and Mas receptor antagonist A779 could abolish those effects. ANG II and ANG(1-7), respectively, downregulated and upregulated the expressions of osteogenesis factors in MC3T3-E1 cells. ANG II promoted the expressions of cathepsin K and MMP9 in RAW 264.7 cells, whereas ANG(1-7) repressed these osteoclastogenesis factors. ANG II rapidly increased the phosphorylation of Akt and p38 in RAW 264.7 cells, whereas ANG(1-7) markedly reduced the phosphorylation of p38 and ERK under high-glucose condition. After treatments of diabetic SHR with valsartan and ANG(1-7), a significant increase in trabecular bone area, bone mineral density, and mechanical strength was only found in the ANG(1-7)-treated group. Treatment with ANG(1-7) significantly suppressed the increase in renin expression and ANG II content in the bone of SHR. Taken together, ANG II/AT1R and ANG(1-7)/Mas distinctly regulated the differentiation and functions of osteoblasts and osteoclasts upon exposure to high-glucose condition. ANG(1-7) could protect SHR from diabetes-induced osteoporosis.

Curcumin protects bone biomechanical properties and microarchitecture in type 2 diabetic rats with osteoporosis via the TGFβ/Smad2/3 pathway.

Type 2 diabetic osteoporosis (T2DOP) has become a common secondary cause of osteoporosis that accelerates bone loss and leads to bone fractures. The aim of the current study was to investigate the association between the anti-osteoporotic effect of curcumin (Cur) and the transforming growth factor (TGF)β/Smads signaling pathway. Male Sprague-Dawley rats were used in the experiments. The type 2 diabetes mellitus (T2DM) animals were treated with Cur for 8 weeks and blood lipid markers, bone microstructure and bone biomechanics were then evaluated. The mRNA expression levels of TGFβ1, type I TGFβ receptor (TβRI), TβRII and Smad2/3 were determined using reverse transcription-quantitative PCR (RT-qPCR) and immunohistochemistry. The body weight of rats with type 2 diabetes-induced osteoporosis increased (P<0.05), while the lipid (total cholesterol, triglyceride and low-density lipoprotein) and fasting blood glucose levels were decreased by Cur (P<0.05). In addition, Cur significantly improved bone biomechanical properties (maximum load, breaking load, elastic load and the bone rigidity coefficient) and preserved bone microarchitecture (P<0.05). The RT-qPCR and IHC results revealed that Cur increased TGFβ1, TβRI, TβRII and Smad2/3 expression levels and promoted Smad2/3 phosphorylation in bones. The present results also indicated that Cur regulated lipid and glucose levels, improved bone biomechanical properties and preserved bone microarchitecture, and that these effects may be mediated via TGFβ/Smad2/3 pathway activation.

Tubeimoside I suppresses diabetes-induced bone loss in rats, osteoclast formation, and RANKL-induced nuclear factor-κB pathway

Type 2 diabetes mellitus is often companied with osteoporosis, a process which involves osteoclast activation. In this study, we found tubeimoside I, a natural compound isolated from the Chinese medicinal herb Bolbostemma paniculatum (Maxim) Franquet (Cucurbitaceae), significantly ameliorated the decrease of bone mass in type 2 diabetes-induced osteoporosis in rats. It appears that tubeimoside I exerts this protecting effect through inhibiting osteoclast formation and function. Futhermore, our study showed that tubeimoside I inhibits NF-κB transcriptional activation and degradation of IκBα. Collectively, our results reveal that tubeimoside I attenuates osteoclastogenesis through down-regulating NF-κB signaling pathway, and is a potential candidate for the treatment of bone-destructive diseases like type 2 diabetic osteoporosis.

Rehmannia glutinosa Libosch Extracts Prevent Bone Loss and Architectural Deterioration and Enhance Osteoblastic Bone Formation by Regulating the IGF-1/PI3K/mTOR Pathway in Streptozotocin-Induced Diabetic Rats.

Rehmanniae Radix Praeparata (RR, named as Shudihuang in traditional Chinese medicine), the steamed roots of Rehmannia glutinosa Libosch (Scrophulariaceae), has been demonstrated to have anti-diabetic and anti-osteoporotic activities. This study aimed to explore the protective effect and underlying mechanism of RR on diabetes-induced bone loss. It was found that RR regulated the alkaline phosphatase activity and osteocalcin level, enhanced bone mineral density, and improved the bone microarchitecture in diabetic rats. The catalpol (CAT), acteoside (ACT), and echinacoside (ECH) from RR increased the proliferation and differentiation of osteoblastic MC3T3-E1 cells injured by high glucose and promoted the production of IGF-1 and expression of related proteins in BMP and IGF-1/PI3K/mammalian target of rapamycin complex 1 (mTOR) signaling pathways. The verifying tests of inhibitors of BMP pathway (noggin) and IGF-1/PI3K/mTOR pathway (picropodophyllin) and molecular docking of IGF-1R further indicated that CAT, ACT, and ECH extracted from RR enhanced bone formation by regulating IGF-1/PI3K/mTOR signaling pathways. These findings suggest that RR may prove to be a promising candidate drug for the prevention and treatment of diabetes-induced osteoporosis.

Zinc Supplementation Increased Bone Mineral Density, Improves Bone Histomorphology, and Prevents Bone Loss in Diabetic Rat.

Diabetic osteoporosis (DOP) is a complication of diabetes, with the characteristics of bone mineral density (BMD) reduction and bone structure destruction. Zinc was reported has a benefit effect on postmenopausal osteoporosise, it was also has hypoglycemic effect, whether zinc was beneficial on diabetes-induced osteoporosis has not been reported. So in the present study, we established a diabetic rat model by streptozotocin injection (60mg/kg), and administered zinc sulfate by oral gavage to investigate the protective effects of zinc on DOP and the underline possible mechanism. Thirty six Sprague Dawley rats were divided into T1DM group (diabetic rats), control group (vehicle treatment), and T1DM-Zinc group (diabetic rats administered zinc sulfate 0.25mg/kg by oral gavage). The bone histomorphological parameters, serum bone metabolism markers (including ALP, OPG, RUNX 2, and RANKL), BMD, and bone marrow adipocyte numbers were detected after eight weeks of zinc sulfate treatment. The results showed zinc sulfate administration (0.25mg/kg/d) decreased blood glucose, increased the BMD, decreased serum ALP, and RANKL, increased serum OPG and RUNX 2 levels, as well as OPG/RANKL ratio of T1DM rats. Meanwhile, the bone histomorphological parameters, bone marrow adipocytes numbers were returned to be normal. The RUNX 2, and OPG mRNA expression levels in bone tissues of T1DM-Zinc group rats were increased after zinc sulfate treatment compared with the diabetic rats (P < 0.05). Those indicating that zinc sulfate can prevent DOP, the protective mechanism were mainly related to its hypoglycemic effect, bone marrow lipogenesis inhibition effect, OPG/RANKL ratio and RUNX 2 up-regulation effect.

Icariin Prevents Diabetes-Induced Bone Loss in Rats by Reducing Blood Glucose and Suppressing Bone Turnover.

Diabetic Osteoporosis (DOP) is a common metabolic bone disease, characterized by decreased bone mineral density (BMD) and destruction of bone microstructure. It has been reported that icariin is beneficial for estrogen deficiency-induced osteoporosis, and alcohol-induced osteoporosis; whether icariin has protective effects on diabetes-induced osteoporosis has not been reported. In this study, a rat model of diabetic osteoporosis was established by streptozotocin injection, the bone protective effects and potential mechanism of icariin on diabetes-induced bone loss was observed. Thirty 8-week-old female Sprague Dawley rats were divided into control group (vehicle treatment), T1DM (diabetic) group and T1DM-icariin (ICA) group (diabetic rats treated with icariin), 10 rats in each group. The bone histomorphometry parameters, bone mineral density (BMD), serum bone turnover markers, and bone marrow adipogenesis were analyzed after 8 weeks of icariin administration. The results showed consumption of icariin at a doses of 100 mg kg−1 decreased blood glucose, and increased the BMD of diabetic rats. Icariin effectively decreased serum bone turnover marker levels, including CTX-1, ALP, TRACP 5b, osteocalcin, and PINP. Meanwhile, the bone histomorphometry parameters, the number of osteoclasts per bone perimeter were turned to be normal level, and the icariin treatment suppressed bone marrow adipogenesis. The runt-related transcription factor 2 (RUNX 2), as well as the osteoprotegerin (OPG)/receptor activator of nuclear factor-κ B ligand (RANKL) ratio in serum and bone tissues were increased significantly after icariin treatment in diabetic rats. All of the above indicate that oral administration of icariin can prevent diabetic osteoporosis; the effect is mainly related to its ability to reduce blood glucose, inhibit bone turnover and bone marrow adipogenesis, as well as up-regulate bone RUNX 2, and OPG expression.

Methoxsalen and Bergapten Prevent Diabetes-Induced Osteoporosis by the Suppression of Osteoclastogenic Gene Expression in Mice.

This study evaluated whether bergapten and methoxsalen could prevent diabetes-induced osteoporosis and its underlying mechanism. For 10 weeks, bergapten or methoxsalen (0.02%, w/w) was applied to diabetic mice that were provided with a high-fat diet and streptozotocin. Bone mineral density (BMD) and microarchitecture quality were significantly reduced in the diabetic control group; however, both bergapten and methoxsalen reversed serum osteocalcin, bone-alkaline phosphatase and femur BMD. These coumarin derivatives significantly increased bone volume density and trabecular number, whereas they decreased the structure model index of femur tissue in diabetic mice. Conversely, tartrate-resistant acid phosphatase 5 (TRAP) staining revealed that these derivatives reduced osteoclast numbers and formation in diabetic bone tissue. Additionally, both bergapten and methoxsalen tended to downregulate the expression of osteoclast-related genes such as receptor activator of nuclear factor kappa-B ligand (RANKL), nuclear of activated T-cells, cytoplasmic 1 (NFATc1) and TRAP in diabetic femurs, with NFATc1 and TRAP expression showing significant reductions. Our data suggest that both bergapten and methoxsalen prevent diabetic osteoporosis by suppressing bone resorption.

Anthocyanin-rich extract from black rice (Oryza sativa L. Japonica) ameliorates diabetic osteoporosis in rats.

Diabetic osteoporosis (DOP) is a systemic endocrine-metabolic osteopathy which has the characteristics of bone mineral density (BMD) reduction and bone microstructural destruction. Although anthocyanin-rich extract from black rice (AEBR) was reported to have a beneficial effect on diabetic rats, no studies have been performed on whether black rice anthocyanins are beneficial for diabetic osteoporosis. Therefore, in this study, a streptozotocin-induced diabetic rat model was established to investigate the protective effect of AEBR on diabetes-induced osteoporosis and its possible mechanism. AEBR at three doses (0.5, 1.0, and 2.0 g kg-1 d-1) were administered by oral gavage to diabetic rats for 8 weeks. The blood glucose, BMD, bone histomorphometry parameters, serum bone turnover biomarkers, bone marrow adipocyte numbers, as well as osteoprotegerin (OPG), runt-related transcription factor 2 (RUNX 2), and receptor activator of nuclear factor-κ B ligand (RANKL) protein expression in bone and serum were detected. The results indicated that AEBR dose-dependently decreased the blood glucose, increased the BMD, and decreased the serum bone turnover markers. The bone microstructure and osteoclast numbers in bone tissues returned to normal in the high AEBR dosage group; at the same time, the AEBR dose-dependently suppressed bone marrow adipogenesis. The RUNX 2 as well as the OPG/RANKL ratio in diabetic rats' bone tissues increased significantly in the AEBR treatment group. Our results indicate that AEBR administration can ameliorate bone loss caused by diabetes; this is mainly attributed to its inhibition of bone turnover, suppression of bone marrow adipogenesis, and up-regulation of RUNX 2 and the OPG/RANKL expression ratio.