Hyperglycemia induced and intrinsic alterations in type 2 diabetes-derived osteoclast function

Shared genetic architecture between periodontal disease and type 2 diabetes: a large scale genome-wide cross-trait analysis

PURPOSE

To investigate the relationship between abnormal glucose metabolism, type 2 diabetes (T2D), and periodontal disease (PER) independent of Body Mass Index (BMI), we employed a genome-wide cross-trait approach to clarify the association.

METHODS

Our study utilized the most extensive genome-wide association studies conducted for populations of European ancestry, including PER, T2D, fasting glucose, fasting insulin, 2-hour glucose after an oral glucose challenge, HOMA-β, HOMA-IR (unadjusted or adjusted for BMI) and HbA1c.

RESULTS

With this approach, we were able to identify pleiotropic loci, establish expression-trait associations, and quantify global and local genetic correlations. There was a significant positive global genetic correlation between T2D (rg = 0.261, p = 2.65 × 10-13), HbA1c (rg = 0.182, p = 4.14 × 10-6) and PER, as well as for T2D independent of BMI (rg = 0.158, p = 2.34 × 10-6). A significant local genetic correlation was also observed between PER and glycemic traits or T2D. We also identified 62 independent pleiotropic loci that impact both PER and glycemic traits, including T2D. Nine significant pathways were identified between the shared genes between T2D, glycemic traits and PER. Genetically liability of HOMA-βadjBMI was causally associated with the risk of PER.

CONCLUSION

Our research has revealed a genetic link between T2D, glycemic traits, and PER that is influenced by biological pleiotropy. Notably, some of these links are not related to BMI. Our research highlights an underlying link between patients with T2D and PER, regardless of their BMI.

Advantages and Limitations of Diabetic Bone Healing in Mouse Models: A Narrative Review

Diabetes represents a major risk factor for impaired fracture healing. Type 2 diabetes mellitus is a growing epidemic worldwide, hence an increase in diabetes-related complications in fracture healing can be expected. However, the underlying mechanisms are not yet completely understood. Different mouse models are used in preclinical trauma research for fracture healing under diabetic conditions. The present review elucidates and evaluates the characteristics of state-of-the-art murine diabetic fracture healing models. Three major categories of murine models were identified: Streptozotocin-induced diabetes models, diet-induced diabetes models, and transgenic diabetes models. They all have specific advantages and limitations and affect bone physiology and fracture healing differently. The studies differed widely in their diabetic and fracture healing models and the chosen models were evaluated and discussed, raising concerns in the comparability of the current literature. Researchers should be aware of the presented advantages and limitations when choosing a murine diabetes model. Given the rapid increase in type II diabetics worldwide, our review found that there are a lack of models that sufficiently mimic the development of type II diabetes in adult patients over the years. We suggest that a model with a high-fat diet that accounts for 60% of the daily calorie intake over a period of at least 12 weeks provides the most accurate representation.

Influence of type 2 diabetes on immunohistochemical detection of TRAF6, cFos and NFATC1 in the gingiva in cases of chronic periodontitis

Type 2 diabetes (T2D) and chronic periodontitis (CP) are common diseases worldwide. Although T2D increases the severity of CP and alveolar bone loss, the mechanism of this is not well understood. We investigated using immunohistochemistry the expression of three osteoclast proteins, TRAF6, cFos and NFATc1, in gingival tissues. Gingival tissues were obtained from three groups: HC group, healthy controls; CP group, patients with CP; T2D + CP group, patients with both T2D and CP. Strong immunostaining for TRAF6, cFos and NFATc1 was observed in the gingival epithelium as well as in inflammatory cells in the CP and T2D + CP groups. Immunostaining was most intense in the T2D + CP group. We found strong up-regulation of TRAF6, cFos and NFATC1 in gingiva tissue of subjects with both T2D and CP, which corroborates our hypothesis that T2D potentiates osteoclastogenesis in CP.

Metformin attenuates diabetes-induced osteopenia in rats is associated with down-regulation of the RAGE-JAK2-STAT1 signal axis

Background

Osteopenia and fragile fractures are diabetes-associated complications. Many hypoglycemic drugs have effects on bone metabolism. Metformin, as is a prescribed medication for type 2 diabetes mellitus (T2DM), had been reported to have osteoprotective effects beyond its hypoglycemic effect, however the potential mechanism behind these effects remains unclear. In this study, we aimed to investigate the comprehensive effects of metformin on bone metabolism in T2DM rat model and elucidate the potential mechanism.

Methods

Goto-Kakizaki spontaneous T2DM rats with significant hyperglycemia were treated with/without metformin for 20 weeks. Glucose tolerance was tested and all rats were weighed every two weeks. The osteoprotective effects of metformin in diabetic rats were determined by quantifying serum bone biomarkers, μ-CT imaging, histological staining, bone histomorphometry, and biomechanical properties analyses. Potential targets of metformin in the treatment of T2DM and osteoporosis were predicted using network pharmacology. The effects of metformin on mesenchymal stem cells (C3H10) cultured in high glucose medium were evaluated by CCK-8 assay, alkaline phosphatase (ALP) staining, qPCR and western blotting.

Results

This study demonstrated that metformin significantly attenuated osteopenia, decreased serum glucose and glycated serum protein (GSP) levels, improved bone microarchitecture, and biomechanical properties in GK rats with T2DM. Metformin significantly increased biomarkers of bone formation, and significantly decreased muscle ubiquitin C (Ubc) expression. Network pharmacology analysis found that signal transducer and activator of transcription1 (STAT1) would be a potential target of metformin for regulating bone metabolism. Metformin increased C3H10 ​cell viability in vitro, alleviated ALP inhibition caused by hyperglycemia, increased the osteogenic gene expression of runt-related transcription factor 2 (RUNX2), collagen type I alpha 1 (Col1a1), osteocalcin (OCN), and ALP, while suppressing RAGE and STAT1 expression. Metformin also increased the protein expression of Osterix and decreased that of RAGE, p-JAK2, and p-STAT1.

Conclusions

Our results demonstrate that metformin attenuated osteopenia and improved bone microarchitecture in GK rats with T2DM and significantly promoted stem cell osteogenic differentiation under high glucose condition. The effects of metformin on bone metabolism are closely associated with the suppression of RAGE-JAK2-STAT1 signaling axis.

The translational potential of this article

Our research provides experiment evidence and potential mechanistic rationale for the use of metformin as an effective candidate for diabetes-induced osteopenia treatment.

Human umbilical cord mesenchymal stem cells accelerate and increase implant osseointegration in diabetic rats

OBJECTIVE

This study was conducted to assess the effect of hUCMSCs injection on the osseointegration of dental implant in diabetic rats via Runt-related Transcription Factor 2 (Runx2), Osterix (Osx), osteoblasts, and Bone Implant Contact (BIC).

METHODOLOGY

The research design was a true experimental design using Rattus norvegicus Wistar strain. Rattus norvegicus were injected with streptozotocin to induce experimental diabetes mellitus. The right femur was drilled and loaded with titanium implant. Approximately 1 mm from proximal and distal implant site were injected with hUCMSCs. The control group was given only gelatin solvent injection. After 2 and 4 weeks of observation, the rats were sacrificed for further examination around implant site using immunohistochemistry staining (RUNX2 and Osterix expression), hematoxylin eosin staining, and bone implant contact area. Data analysis was done using ANOVA test.

RESULTS

Data indicated a significant difference in Runx2 expression (p<0.001), osteoblasts (p<0.009), BIC value (p<0.000), and Osterix expression (p<0.002). In vivo injection of hUCMSCs successfully increased Runx2, osteoblasts, and BIC value significantly, while decreased Osterix expression, indicating an acceleration of the bone maturation process.

CONCLUSION

The results proved hUCMSCs to accelerate and enhance implant osseointegration in diabetic rat models.

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

Network pharmacology-based strategy for predicting therapy targets of Sanqi and Huangjing in diabetes mellitus

BACKGROUND

A comprehensive literature search shows that Sanqi and Huangjing (SQHJ) can improve diabetes treatment in vivo and in vitro, respectively. However, the combined effects of SQHJ on diabetes mellitus (DM) are still unclear.

AIM

To explore the potential mechanism of Panax notoginseng (Sanqi in Chinese) and Polygonati Rhizoma (Huangjing in Chinese) for the treatment of DM using network pharmacology.

METHODS

The active components of SQHJ and targets were predicted and screened by network pharmacology through oral bioavailability and drug-likeness filtration using the Traditional Chinese Medicine Systems Pharmacology Analysis Platform database. The potential targets for the treatment of DM were identified according to the DisGeNET database. A comparative analysis was performed to investigate the overlapping genes between active component targets and DM treatment-related targets. We constructed networks of the active component-target and target pathways of SQHJ using Cytoscape software and then analyzed the gene functions. Using the STRING database to perform an interaction analysis among overlapping genes and a topological analysis, the interactions between potential targets were identified. Gene Ontology (GO) function analyses and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were conducted in DAVID.

RESULTS

We screened 18 active components from 157 SQHJ components, 187 potential targets for active components and 115 overlapping genes for active components and DM. The network pharmacology analysis revealed that quercetin, beta-sitosterol, baicalein, etc. were the major active components. The mechanism underlying the SQHJ intervention effects in DM may involve nine core targets (TP53, AKT1, CASP3, TNF, interleukin-6, PTGS2, MMP9, JUN, and MAPK1). The screening and enrichment analysis revealed that the treatment of DM using SQHJ primarily involved 16 GO enriched terms and 13 related pathways.

CONCLUSION

SQHJ treatment for DM targets TP53, AKT1, CASP3, and TNF and participates in pathways in leishmaniasis and cancer.

Bone Remodeling in Mandible of Wistar Rats with Diabetes Mellitus and Osteoporosis

OBJECTIVES

 This study aimed to determine some of bone molecular expressions and its possible bone remodeling pathway between diabetes mellitus (DM) and osteoporosis model in the mandibular bone of Wistar rats.

MATERIALS AND METHODS

 Twenty-seven female Wistar rats were divided randomly into control and treatment groups. Treatment groups were injected with streptozotocin intraperitoneally to induce DM (P1) and underwent bilateral ovariectomy to generate osteoporosis (P2). All groups were terminated after 12 weeks. Immunohistochemical and hematoxylin-eosin staining were performed to determine the expression of Runt-related transcription factor 2 (RUNX2), Osterix, vascular endothelial growth factor (VEGF), receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), tartrate-resistant acid phosphatase (TRAP), and observed the osteoblast and osteoclast. Statistical analysis was performed using one-way analysis of variance.

RESULTS

 The lowest mean of RUNX2 and VEGF expression was found in the P2 group. The lowest mean of Osterix expression was found in the P1 group. Both P1 and P2 groups of osteoblast/osteoclast ratio were decreased. There were no significant differences in the expression of TRAP between all groups; however, increased expression of RANKL/OPG ratio was only found in the P2 group.

CONCLUSION

 DM and osteoporosis induce changes in the bone remodeling pathway which are represented by a decrease in osteoblast biomarkers and an increase in osteoclast biomarkers.

Effect of verapamil on bone mass, microstructure and mechanical properties in type 2 diabetes mellitus rats

Background

Verapamil was mainly used to treat hypertension, cardiovascular disease, inflammation and improve blood glucose in patients with diabetes, but its effects on bone mass, microstructure and mechanical properties were unclear. This study described the effects of verapamil on bone mass, microstructure, macro and nano mechanical properties in type 2 diabetic rats.

Methods

Rat models of type 2 diabetes were treated with verapamil at doses of 4, 12, 24 and 48 mg/kg/day by gavage respectively, twice a day. After 12 weeks, all rats were sacrificed under general anesthesia. Blood glucose, blood lipid, renal function and biochemical markers of bone metabolism were obtained by serum analysis, Micro-CT scanning was used to assess the microstructure parameters of cancellous bone of femoral head, three-point bending test was used to measure maximum load and elastic modulus of femoral shaft, and nano-indentation tests were used to measure indentation moduli and hardnesses of longitudinal cortical bone in femoral shaft, longitudinal and transverse cancellous bones in femoral head.

Results

Compared with T2DM group, transverse indentation moduli of cancellous bones in VER 24 group, longitudinal and transverse indentation moduli and hardnesses of cancellous bones in VER 48 group were significantly increased (p < 0.05). Furthermore, the effects of verapamil on blood glucoses, microstructures and mechanical properties in type 2 diabetic rats were dependent on drug dose. Starting from verapamil dose of 12 mg/kg/day, with dose increasing, the concentrations of P1NP, BMD, BV/TV, Tb. Th, Tb. N, maximum loads, elastic moduli, indentation moduli and hardnesses of femurs in rats in treatment group increased gradually, the concentrations of CTX-1 decreased gradually, but these parameters did not return to the level of the corresponding parameters of normal rats. Verapamil (48 mg/kg/day) had the best therapeutic effect.

Conclusion

Verapamil treatment (24, 48 mg/kg/day) significantly affected nano mechanical properties of the femurs, and tended to improve bone microstructures and macro mechanical properties of the femurs, which provided guidance for the selection of verapamil dose in the treatment of type 2 diabetic patients.

A Review of Coumarins and Coumarin-Related Compounds for Their Potential Antidiabetic Effect

Background and aims:

Worldwide, type 2 diabetes mellitus accounts for a considerable burden of disease, with an estimated global cost of >800 billion USD annually. For this reason, the search for more effective and efficient therapeutic anti-diabetic agents is continuing. Coumarins are naturally derived and synthetic molecules with a wide variety of biological actions. The most common application of these molecules in medicine is for their thrombostatic activity. This study aims to give an overview of the current knowledge about the applicability of these chemical products in the therapeutic strategy against diabetes and its complications.

Methods:

For this purpose, we searched internet databases for publications and abstracts in English that investigated the effects of coumarins or coumarin-like agents with potential anti-diabetic activity.

Results:

The result is that a variety of these agents have proven in in vitro, in silico, and simple animal models to possess properties that may reduce the glucose absorption rate in the intestines, increase the level of insulin, increase the cellular uptake of glucose or reduce the gluconeogenesis. In addition, some of these agents also reduced the level of glycation of peptides in diabetic animal models and showed antioxidant properties.

Conclusion:

In conclusion, we can summarize that coumarins and their related derivatives may be potential antidiabetic agents. Useful formulations with appropriate pharmacokinetic and pharmacodynamic properties must be developed and tested for their efficacy and toxicity in comprehensive animal models before they can enter clinical trials.

Impaired dental implant osseointegration in rat with streptozotocin-induced diabetes

OBJECTIVE

Few studies have reported on the impact of oxidative stress on the dental implant failure. The aim of this study was to investigate the impact of hyperglycemia-induced oxidative stress on dental implant osseointegration in diabetes mellitus (DM).

METHODS

Acid-treated titanium implants were bilaterally placed in the maxillary alveolar ridge of streptozotocin-induced diabetic (DM group) and control rats after extraction of first molars. Histological analysis and micro-push-out test were performed 4 weeks after surgery. Oxidative stress and osteogenic markers in the surrounding bone were quantified by real-time polymerase chain reaction. In the in vitro study, rat bone marrow-derived mesenchymal stem cells (BMMSCs) were cultured on acid-treated titanium discs in a high-glucose (HG) or normal environment. Intracellular reactive oxygen species (ROS), cell proliferation, alkaline phosphatase (ALP) activity, and extracellular calcification were evaluated following antioxidant treatment with N-acetyl-L-cysteine (NAC).

RESULTS

The implant survival rate was 92.9% and 75.0% in control and DM group, respectively. Bone-implant contact and push-out loads were significantly lower in the DM group. Expression of superoxide dismutase 1 at the mRNA level and on immunohistochemistry was significantly lower in the DM group. In vitro experiments revealed that the HG condition significantly increased ROS expression and suppressed the proliferation and extracellular calcification of BMMSCs, while NAC treatment significantly restored ROS expression, cell proliferation, and calcification. The ALP activity of both groups was not significantly different.

CONCLUSION

In diabetes, high-glucose-induced oxidative stress downregulates proliferation and calcification of BMMSCs, impairing osseointegration and leading to implant failure.

AdipoRon Promotes the Osseointegration of Dental Implants in Mice With Type 2 Diabetes Mellitus

AdipoRon is an oral active synthetic small molecule with biological functions similar to adiponectin (APN). It is an APN receptor agonist that can improve insulin resistance and glucose intolerance. However, the role of AdipoRon in bone metabolism and related molecular mechanisms remains to be investigated. To explore the effect of AdipoRon on bone absorption and bone integration of type 2 diabetes mellitus (T2DM) mice with implants, we established surgery-induced model of osseointegration of dental implantation in T2DM mice of C57BL/6 db/db and normal mice homologous to diabetic mice. Micro-CT was used to analyze the femurs with the implant in the mice to detect the bone mass, H&E, and tartrate-resistant acid phosphatase (TRAP), and Safranin O-fast green staining was performed to analyze the bone formation and bone resorption. Bone integration-related markers as Rankl, bone morphogenetic protein 2 (BMP2), osteoprotegerin (OPG), osteopontin (OPN), and runt-related transcription factor 2 (Runx2) were also measured using immunohistochemistry. Our results indicated that diabetic mice showed a lower bone mass and decreased the osteoblast differentiation. AdipoRon attenuated diabetes-impaired bone volume (BV)/total volume (TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), and bone integration-related markers variation and promoted bone hyperplasia as well as repressed the osteoclast formation, especially in diabetic mice. AdipoRon may improve the osseointegration of dental implants in mice with T2DM by promoting osteogenesis and inhibiting bone resorption, and AdipoRon may serve as a promising oral strategy to improve the osseointegration ability of patients with diabetes.

Association between metabolic syndrome and periodontitis: The role of lipids, inflammatory cytokines, altered host response, and the microbiome

Periodontitis has been associated with many systemic diseases and conditions, including metabolic syndrome. Metabolic syndrome is a cluster of conditions that occur concomitantly and together they increase the risk of cardiovascular disease and double the risk of type 2 diabetes. In this review, we focus on the association between metabolic syndrome and periodontitis; however, we also include information on diabetes mellitus and cardiovascular disease, since these two conditions are significantly intertwined with metabolic syndrome. With regard to periodontitis and metabolic syndrome, to date, the vast majority of studies point to an association between these two conditions and also demonstrate that periodontitis can contribute to the development of, or can worsen, metabolic syndrome. Evaluating the effect of metabolic syndrome on the salivary microbiome, data presented herein support the hypothesis that the salivary bacterial profile is altered in metabolic syndrome patients compared with healthy patients. Considering periodontitis and these three conditions, the vast majority of human and animal studies point to an association between periodontitis and metabolic syndrome, diabetes, and cardiovascular disease. Moreover, there is evidence to suggest that metabolic syndrome and diabetes can alter the oral microbiome. However, more studies are needed to fully understand the influence these conditions have on each other.

Strontium-incorporated titanium implant surfaces treated by hydrothermal treatment enhance rapid osseointegration in diabetes: A preclinical vivo experimental study

OBJECTIVES

The aim of the current study was to explore effects of strontium-incorporated titanium implant surfaces by hydrothermal treatment on osseointegration in diabetic rats.

MATERIALS AND METHODS

The surface characteristics of SLA and SLA-Sr surfaces were detected by related instruments. Thirty-six male Sprague-Dawley rats were induced into diabetes, and thirty-six rats were normal. SLA and SLA-Sr implants were, respectively, inserted into bilateral tibial metaphysis of each rat. Percentage of bone-to-implant contact (BIC%) and percentage of bone area (BA%) were analyzed at 4 and 8 weeks after implantation. Immunohistochemistry of osteoprotegerin (OPG) and Wnt5a were conducted at 1 and 4 weeks. Gene expression levels of inflammatory cytokines and related signaling molecules in peri-implant bone tissue were detected at 3 and 7 days.

RESULTS

Strontium was uniformly distributed on SLA-Sr surfaces, and it was released in an effective concentration range. SLA-Sr surfaces showed significantly higher BIC% in diabetic rats at 4 (p < .05) and 8 weeks (p < .05). Besides, it displayed higher BIC% at 4 weeks (p < .05) in normal rats. Also, SLA-Sr surfaces upregulated expression of OPG at 4 weeks (p < .05) in diabetic rats. What's more, SLA-Sr surfaces downregulated inflammation (TNF-α, IL-1β, and IL-6; p < .01) in diabetic rats at 3 days. In addition, expression of Wnt5a and ROR2 was upregulated (p < .05) at 7 days after implantation under diabetes.

CONCLUSION

It is suggested that strontium-incorporated titanium implant surfaces by hydrothermal treatment could enhance implant osseointegration as compared with SLA implant surfaces in diabetic rats.

Glycemic fluctuation exacerbates inflammation and bone loss and alters microbiota profile around implants in diabetic mice with experimental peri-implantitis

BACKGROUND

The impact of glycemic fluctuation under diabetic condition on peri-implantitis in diabetic patients remains unclear. We hypothesized that glycemic fluctuation has greater adverse effect on experimental peri-implantitis, compared with sustained high blood glucose in diabetes.

RESULTS

Maxillary left first and second molars of diabetic db/db mice were extracted and were replaced with one dental implant in the healed edentulous space. Glycemic control or fluctuation were managed by constant or interrupted oral administration of rosiglitazone to these mice. Meanwhile, experimental peri-implantitis was induced by ligation around implants. After 14 weeks, inflammatory responses, and peri-implant bone loss, together with oral microbiota profile were analyzed. Diabetic mice with glycemic fluctuation showed greater peri-implant bone loss, inflammatory cell infiltration, and osteoclastogenesis, compared with mice with sustained hyperglycemia. Compared to sustained hyperglycemia, glycemic fluctuation led to further increase in IL-1β, TNFα, RANKL, TLR2/4, IRAK1, and TRAF6 mRNA expression in peri-implant gingival tissues. Both rosiglitazone-induced glycemic control and glycemic fluctuation caused microbiota profile change in diabetic mice compared to that in uncontrolled hyperglycemic mice.

CONCLUSIONS

This study suggests that glycemic fluctuation may aggravate peri-implantitis inflammation and bone loss, which may be associated with a shift in peri-implant microbial profile towards dysbiotic changes and the activation of TLR2/4-IRAK1-TRAF6 signaling.

Spirulina supplementation improves bone structural strength and stiffness in streptozocin-induced diabetic rats

Spirulina (blue-green algae) contains a wide range of nutrients with medicinal properties which include β-carotene, chromium, and moderate amounts of vitamins B₁₂. This study aims to determine the preventive effect of spirulina against bone fragility linked to type 2 diabetes mellitus. Thirty Sprague-Dawley rats were divided into five groups (n = 6) and diabetes was induced using streptozocin. Rats with a plasma glucose level of 10 mmol/L and above were orally treated for twelve weeks with either a single dose of spirulina, metformin, or a combined dose of spirulina + metformin per day. After the treatment, blood and bones were taken for biochemical analysis, three-dimensional imaging, 3-point biomechanical analysis, histology imaging and gene expression using qPCR. Results showed that diabetes induction and treatment with metformin caused destruction in the trabecular microarchitecture of the femur bone, reduction in serum bone marker and expression of bone formation marker genes in the experimental rats. Spirulina supplementation showed improved trabecular microarchitecture with a denser trabecular network, increased 25-OH vitamin D levels, and lowered the level of phosphate and calcium in the serum. Biomechanical tests revealed increased maximum force, stress strain, young modulus and histology images showed improvement in regular mesh and an increase in osteoblasts and osteocytes. There was an increase in the expression of bone formation marker osteocalcin. The results suggest that spirulina supplementation was more effective at improving bone structural strength and stiffness in diabetic rats compared to metformin. Spirulina may be able to prevent T2DM-related brittle bone, lowering the risk of fracture.

The Role of Adipose Stem Cells in Bone Regeneration and Bone Tissue Engineering

Bone regeneration is a complex process that is influenced by tissue interactions, inflammatory responses, and progenitor cells. Diseases, lifestyle, or multiple trauma can disturb fracture healing, which might result in prolonged healing duration or even failure. The current gold standard therapy in these cases are bone grafts. However, they are associated with several disadvantages, e.g., donor site morbidity and availability of appropriate material. Bone tissue engineering has been proposed as a promising alternative. The success of bone-tissue engineering depends on the administered cells, osteogenic differentiation, and secretome. Different stem cell types offer advantages and drawbacks in this field, while adipose-derived stem or stromal cells (ASCs) are in particular promising. They show high osteogenic potential, osteoinductive ability, and immunomodulation properties. Furthermore, they can be harvested through a noninvasive process in high numbers. ASCs can be induced into osteogenic lineage through bioactive molecules, i.e., growth factors and cytokines. Moreover, their secretome, in particular extracellular vesicles, has been linked to fracture healing. The aim of this review is a comprehensive overview of ASCs for bone regeneration and bone tissue engineering.

Diabetoporosis: Role of nitric oxide

Diabetoporosis, diabetic-related decreased bone quality and quantity, is one of the leading causes of osteoporotic fractures in subjects with type 2 diabetes (T2D). This is associated with lower trabecular and cortical bone quality, lower bone turnover rates, lower rates of bone healing, and abnormal posttranslational modifications of collagen. Decreased nitric oxide (NO) bioavailability has been reported within the bones of T2D patients and can be considered as one of the primary mechanisms by which diabetoporosis is manifested. NO donors increase trabecular and cortical bone quality, increase the rate of bone formation, accelerate the bone healing process, delay osteoporosis, and decrease osteoporotic fractures in T2D patients, suggesting the potential therapeutic implication of NO-based interventions. NO is produced in the osteoblast and osteoclast cells by three isoforms of NO synthase (NOS) enzymes. In this review, the roles of NO in bone remodeling in the normal and diabetic states are discussed. Also, the favorable effects of low physiological levels of NO produced by endothelial NOS (eNOS) versus detrimental effects of high pathological levels of NO produced by inducible NOS (iNOS) in diabetoporosis are summarized. Available data indicates decreased bone NO bioavailability in T2D and decreased expression of eNOS, and increased expression and activity of iNOS. NO donors can be considered novel therapeutic agents in diabetoporosis.

3D Environment Is Required In Vitro to Demonstrate Altered Bone Metabolism Characteristic for Type 2 Diabetics

A large British study, with almost 3000 patients, identified diabetes as main risk factor for delayed and nonunion fracture healing, the treatment of which causes large costs for the health system. In the past years, much progress has been made to treat common complications in diabetics. However, there is still a lack of advanced strategies to treat diabetic bone diseases. To develop such therapeutic strategies, mechanisms leading to massive bone alterations in diabetics have to be well understood. We herein describe an in vitro model displaying bone metabolism frequently observed in diabetics. The model is based on osteoblastic SaOS-2 cells, which in direct coculture, stimulate THP-1 cells to form osteoclasts. While in conventional 2D cocultures formation of mineralized matrix is decreased under pre-/diabetic conditions, formation of mineralized matrix is increased in 3D cocultures. Furthermore, we demonstrate a matrix stability of the 3D carrier that is decreased under pre-/diabetic conditions, resembling the in vivo situation in type 2 diabetics. In summary, our results show that a 3D environment is required in this in vitro model to mimic alterations in bone metabolism characteristic for pre-/diabetes. The ability to measure both osteoblast and osteoclast function, and their effect on mineralization and stability of the 3D carrier offers the possibility to use this model also for other purposes, e.g., drug screenings.

Regulation of Osteoclast Differentiation and Activity by Lipid Metabolism

Bone is a dynamic tissue and is constantly being remodeled by bone cells. Metabolic reprogramming plays a critical role in the activation of these bone cells and skeletal metabolism, which fulfills the energy demand for bone remodeling. Among various metabolic pathways, the importance of lipid metabolism in bone cells has long been appreciated. More recent studies also establish the link between bone loss and lipid-altering conditions—such as atherosclerotic vascular disease, hyperlipidemia, and obesity—and uncover the detrimental effect of fat accumulation on skeletal homeostasis and increased risk of fracture. Targeting lipid metabolism with statin, a lipid-lowering drug, has been shown to improve bone density and quality in metabolic bone diseases. However, the molecular mechanisms of lipid-mediated regulation in osteoclasts are not completely understood. Thus, a better understanding of lipid metabolism in osteoclasts can be used to harness bone cell activity to treat pathological bone disorders. This review summarizes the recent developments of the contribution of lipid metabolism to the function and phenotype of osteoclasts.

Serum osteocalcin is associated with subjective stress in people with depression and type 2 diabetes

BACKGROUND

Low serum osteocalcin is a risk factor for type 2 diabetes mellitus (T2DM), and osteocalcin release from bone is associated with an acute stress response in mice. Both diabetes and stress are associated with depression. Here, we assess relationships between serum osteocalcin, depression and subjective stress in people with T2DM.

METHODS

Participants with T2DM (HbA1c above 6.4 %, impaired fasting glucose or impaired glucose tolerance) were assessed for a major depressive episode using the research version of the Structured Clinical Interview for DSM-5 depression criteria (SCID-5RV). Subjective stress over the past month was assessed using the Perceived Stress Scale (PSS). Serum carboxylated (cOCN) and fully decarboxylated (dcOCN) osteocalcin were assayed from fasting morning blood by commercial enzyme-linked immunosorbent assay.

RESULTS

Among 95 participants (mean age 62.4 ± 9.9, 51 % women), 22 % were experiencing a depressive episode (9 men, 12 women). The presence of a depressive episode was not associated with dcOCN or cOCN concentrations; however, higher concentrations of cOCN were associated with higher PSS scores in participants with depression (r = 0.585, p = 0.005). In an analysis of covariance model controlling for age, sex, body mass index, glycemic control (glycosylated hemoglobin), insulin resistance (homeostatic model), depression, and antidepressant use, cOCN was associated with PSS scores (F=10.302, p = 0.002), and this relationship was stronger in those with depression (depression × cOCN interaction F=4.978, p = 0.028). Although associations between dcOCN concentrations and PSS scores did not reach significance, the same trend seen with cOCN concentrations was observed in participants with depression for dcOCN (r=0.365, p=0.10), and for a depression × dcOCN interaction associated with PSS scores in the whole group (F=2.165, p = 0.15).

CONCLUSIONS

Osteocalcin is a neuroendocrine marker associated with perceived chronic stress among people with T2DM experiencing a depressive episode.

Diabetes as a risk factor for periodontal disease-plausible mechanisms

The present narrative review examines the scientific evidence of the biological mechanisms that may link periodontitis and diabetes, as a source of comorbidity. Publications regarding periodontitis and diabetes, in human, animals, and in vitro were screened for their relevance. Periodontal microbiome studies indicate a possible association between altered glucose metabolism in prediabetes and diabetes and changes in the periodontal microbiome. Coinciding with this, hyperglycemia enhances expression of pathogen receptors, which enhance host response to the dysbiotic microbiome. Hyperglycemia also promotes pro-inflammatory response independently or via the advanced glycation end product/receptor for advanced glycation end product pathway. These processes excite cellular tissue destruction functions, which further enhance pro-inflammatory cytokines expression and alteration in the RANKL/osteoprotegerin ratio, promoting formation and activation of osteoclasts. The evidence supports the role of several pathogenic mechanisms in the path of true causal comorbidity between poorly controlled diabetes and periodontitis. However, further research is needed to better understand these mechanisms and to explore other mechanisms.

The Effects of Diabetes and Diabetic Medications on Bone Health

The incidence and prevalence of diabetes continues to increase, and proper understanding of the adverse effects on bone metabolism is important. This review attempts to discuss the pathophysiology of the effects of diabetes and diabetic medications on bone metabolism and bone health. In addition, this review will address the mechanisms resulting in increased fracture risk and delayed bone healing to better treat and manage diabetic patients in the orthopedic clinical setting.

Chronic hyperglycemia as a risk factor in implant therapy

It has been estimated that by 2030, the number of patients with diabetes aged > 64 years will be > 82 million in underdeveloped countries, and > 48 million in developed countries. Chronic hyperglycemia delays wound healing by reducing the expression of growth factors in the wound fluid and re-epithelialization. Impaired wound healing in patients with diabetes has also been associated with inhibition of the production of stromal cell-derived factor-1alpha by several tissues including bone marrow, brain, heart, spleen, and gingivae. Chronic hyperglycemia interferes with the osseointegration of implants by deferring the expression of fibronectin and integrins. Results from experimental studies have shown a significantly higher bone-to-implant contact around implants placed in healthy animals compared with animals with streptozotocin-induced diabetes. Moreover, persistent hyperglycemia plays a role in abnormal differentiation of osteoclasts, thereby making bone tissue more susceptible to resorption. Furthermore, persistent hyperglycemia has also been associated with increased peri-implant soft tissue inflammation (increased peri-implant bleeding on probing and probing depth) and crestal bone loss. Clinical studies have shown that under optimal glycemic control dental implants can show success and survival rates of up to 100% in patients diagnosed with diabetes. Although patients with diabetes can undergo dental implant therapy and can exhibit implant survival similar to those in systemically healthy individuals, the contribution of glycemic control and regular oral hygiene maintenance cannot be disregarded.

Clinical performance of titanium-zirconium implants with a hydrophilic surface in patients with controlled type 2 diabetes mellitus: 2-year results from a prospective case-control clinical study

OBJECTIVE

Analyze the 2-year clinical performance of single-unit titanium-zirconium (TiZr) alloy narrow-diameter (3.3 mm) dental implants with a hydrophilic surface (Straumann® Roxolid®, SLActive®) in patients with controlled type 2 diabetes mellitus (T2DM), measured using the glycated hemoglobin A (HbA1c) concentration test, compared with results in individuals without T2DM.

MATERIAL AND METHODS

The studied sample consisted of 28 patients, 14 with T2DM (study group) and 14 without (control group). The plaque index, bleeding on probing, probing depth, clinical attachment level, gingival biotype, and marginal bone loss (MBL) at the site of the implants were assessed. HbA1c levels were assessed in all patients during each checkup.

RESULTS

Two years after implant placement and prosthetic restoration no implant failures were reported in either group, resulting in 100% survival and success rates in both groups. No statistically significant differences in MBL were found between the control and study groups (p > 0.05).

CONCLUSIONS

Within the limitations of this study, it can be concluded that reduced-diameter TiZr alloy implants with a hydrophilic surface represent a safe and predictable treatment option for patients with well-controlled T2DM. The clinical performance was comparable with that observed in individuals without T2DM in the medium term.

CLINICAL RELEVANCE

The narrow implants placed in patients with T2DM with well-controlled glycemia (HbA1c) showed a marginal bone loss and success and survival rates similar to those of the control group without DM2, in the medium term.

Host response and peri-implantitis

Considering the absence of predictable and effective therapeutic interventions for the treatment of peri-implantitis, scientific evidence concerning the host response profile around dental implants could be important for providing in the future a wider preventive and/or therapeutic window for this peri-implant lesion, indicating biomarkers that provide quantifiable measure of response to peri-implant therapy. Moreover, a better knowledge of pattern of host osteo-immunoinflammatory modulation in the presence of peri-implantitis could either benefit the early diagnostic of the disease or to cooperate to prognostic information related to the status of the peri-implant breakdown. Finally, new evidences concerning the host profile of modulators of inflammation and of osseous tissue metabolism around dental implants could explain the individual susceptibility for developing peri-implant lesions, identifying individuals or sites with increased risk for peri-implantitis. The focus of this chapter was, based on a systematically searched and critically reviewed literature, summarizing the existing knowledge in the scientific research concerning the host osteo-immunoinflammatory response to the microbiological challenge related to periimplantitis.

Trauma in the Diabetic Limb

Poorly controlled diabetes with comorbid manifestations negatively affects outcomes in lower extremity trauma, increasing the risk of short-term and long-term complications. Management strategies of patients with diabetes that experience lower extremity trauma should also include perioperative management of hyperglycemia to reduce adverse and serious adverse events.

Leukocyte- and platelet-rich fibrin as graft material improves microRNA-21 expression and decreases oxidative stress in the calvarial defects of diabetic rabbits

OBJECTIVE

Leukocyte- and platelet-rich fibrin (L-PRF) represents a natural, low-cost product which may promote tissue healing by mechanisms not fully elucidated. Diabetes mellitus (DM) disrupts bone healing by inducing inflammation and oxidative stress (OS), mechanisms regulated by microRNAs (miRs). The aim of the present study was to investigate the microRNA-21 (miR-21) involvement in diabetic bone regeneration using L-PRF alone or in combination with a standard grafting material.

DESIGN

After the induction of diabetes (alloxan 100 mg/kg), four cranial osteotomies were made in diabetic (n = 12) and non-diabetic (n = 12) rabbits: one was left empty and the remaining three were grafted with L-PRF, bovine hydroxyapatite (Bio-Oss^®) and L-PRF + Bio-Oss®. Two and eight weeks postoperatively, the samples were harvested for miR-21 expression (Real-time RT-PCR) and enzyme-linked immunosorbent assay analyses.

RESULTS

Diabetic rabbits showed decreased miR-21 and matrix metalloproteinase-9 (MMP-9) protein expression while increased malondialdehyde (MDA) levels two weeks postoperatively; however, there were no significant differences in miR-21 and MMP-9 levels between diabetic and non-diabetic rabbits in samples taken eight weeks postoperatively. Application of L-PRF and L-PRF + Bio-Oss^® improved miR-21 and MMP-9 and decreased MDA levels while Bio-Oss® alone enhanced superoxide dismutase (SOD) activity levels in diabetic rabbits.

CONCLUSION

L-PRF alone or in combination with bovine hydroxyapatite as bone graft could be beneficial in DM since it seems to improve inflammation-modulatory miR-21 expression and decreases oxidative stress.

Lower serum osteocalcin concentrations in patients with type 2 diabetes and relationships with vascular risk factors among patients with coronary artery disease

BACKGROUND

Lower serum concentrations of the osteoblast-derived protein, osteocalcin, have been associated with poorer glycemic control, insulin resistance and atherosclerosis, and with the development of type 2 diabetes (T2DM).

METHODS

This study compares concentrations of two physiological forms of osteocalcin, carboxylated (cOCN) and uncarboxylated (unOCN), between participants with T2DM (n = 20) and age-, gender- and body mass index (BMI)-matched participants without T2DM (n = 40) among patients with coronary artery disease (CAD), and it explores relationships between osteocalcin concentrations and cardiovascular risk factors.

RESULTS

Concentrations of unOCN (2.71 ± 1.86 vs. 4.70 ± 2.03 ng/mL; t = -3.635, p = 0.001) and cOCN (8.70 ± 2.27 vs. 10.77 ± 3.69 ng/mL; t = -2.30, p = 0.025) were lower in participants with T2DM. In participants without T2DM, concentrations of cOCN were associated with fitness (VO_2Peak rho = 0.317, p = 0.047) and lower body fat (rho = -0.324, p = 0.041). In participants with T2DM, lower unOCN was associated with HbA1c (rho = -0.516, p = 0.020). Higher body mass was associated with higher unOCN (rho = 0.423, p = 0.009) in participants without T2DM, but with lower concentrations of both unOCN (rho = -0.590, p = 0.006) and cOCN (rho = -0.632, p = 0.003) in participants with T2DM.

CONCLUSION

In patients with CAD, lower osteocalcin concentrations were related to type 2 diabetes, and to adverse fitness, metabolic and obesity profiles.

Update on the impact of type 2 diabetes mellitus on bone metabolism and material properties

The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide, especially as a result of our aging society, high caloric intake and sedentary lifestyle. Besides the well-known complications of T2DM on the cardiovascular system, the eyes, kidneys and nerves, bone strength is also impaired in diabetic patients. Patients with T2DM have a 40-70% increased risk for fractures, despite having a normal to increased bone mineral density, suggesting that other factors besides bone quantity must account for increased bone fragility. This review summarizes the current knowledge on the complex effects of T2DM on bone including effects on bone cells, bone material properties and other endocrine systems that subsequently affect bone, discusses the effects of T2DM medications on bone and concludes with a model identifying factors that may contribute to poor bone quality and increased bone fragility in T2DM.

Osteoclasts in bone regeneration under type 2 diabetes mellitus

Diabetes mellitus (DM) affects hundreds of million people worldwide and the impaired bone healing is an important DM-related complication. Understanding how DM affects the activities of osteoclasts and the underlying mechanisms is crucial to the development of effective approaches for accelerating bone healing in DM condition. To date, however, the influence of DM on osteoclasts remains obscure and controversial. In this study, we established a type 2 DM (T2DM) alveolar bone defect model, which closely simulates the pathogenesis of human T2DM, to explore the diabetic osteoclast activity during bone regeneration. We found that a high glucose concentration diminished the formation of osteoclasts, and the differentiation and function of osteoclasts from T2DM rats were suppressed. The degradation of matrix by osteoclasts was significantly reduced at a high glucose concentration. In vivo experiments further indicated that T2DM inhibited osteoclastogenesis and osteoclast activity, and delayed the degradation of matrix during the alveolar bone regeneration in T2DM rats. Our work clarifies the influence of T2DM on osteoclasts, and provides valuable insights for the design of novel scaffolding materials that target on osteoclasts for T2DM bone regeneration. STATEMENT OF SIGNIFICANCE: Impaired bone healing is one of the diabetes mellitus (DM)-related complications. Understanding how DM affects osteoclast activity and scaffolding matrix degradation is pivotal to the development of effective approaches for accelerating bone healing in DM condition. Currently, the influences of DM on osteoclast activity and matrix degradation in bone defect areas, however, remain controversial and obscure. Herein, we established a type 2 DM (T2DM) alveolar bone defect model and our results show that T2DM inhibited osteoclastogenesis and osteoclast activity, and delayed the degradation of scaffolding matrix. Our work clarifies the influence of T2DM on osteoclasts and matrix degradation, and provides insights for the design of novel scaffolding materials that target on osteoclasts for T2DM bone regeneration.

Hyponatremia Is Associated With Increased Osteoporosis and Bone Fractures in Patients With Diabetes With Matched Glycemic Control

Context

Patients with diabetes mellitus are at increased risk for bone fragility fracture secondary to multiple mechanisms. Hyperglycemia can induce true dilutional hyponatremia. Hyponatremia is associated with gait instability, osteoporosis, and increased falls and bone fractures, and studies suggest that compromised bone quality with hyponatremia may be independent of plasma osmolality. We performed a case-control study of patients with diabetes mellitus matched by median glycated hemoglobin (HbA1c) to assess whether hyponatremia was associated with increased risk of osteoporosis and/or fragility fracture.

Design

Osteoporosis (n = 823) and fragility fracture (n = 840) cases from the MedStar Health database were matched on age of first HbA1c ≥6.5%, sex, race, median HbA1c over an interval from first HbA1c ≥6.5% to the end of the encounter window, diabetic encounter window length, and type 1 vs type 2 diabetes mellitus with controls without osteoporosis (n = 823) and without fragility fractures (n = 840), respectively. Clinical variables, including coefficient of glucose variation and hyponatremia (defined as serum [Na⁺] <135 mmol/dL within 30 days of the end of the diabetic window), were included in a multivariate analysis.

Results

Multivariate conditional logistic regression models demonstrated that hyponatremia within 30 days of the outcome measure was independently associated with osteoporosis and fragility fractures (osteoporosis OR 3.09; 95% CI, 1.37 to 6.98; fracture OR, 6.41; 95% CI, 2.44 to 16.82).

Conclusions

Our analyses support the hypothesis that hyponatremia is an additional risk factor for osteoporosis and fragility fracture among patients with diabetes mellitus.

Characteristics of bone strength and metabolism in type 2 diabetic model Tsumura, Suzuki, Obese Diabetes mice

OBJECTIVE

Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by hyperglycemia, hyperinsulinemia, and complications such as obesity and osteoporosis. The Tsumura, Suzuki, Obese Diabetes (TSOD) mouse is an animal model of spontaneous obese T2DM. However, bone metabolism in TSOD mice is yet to be investigated. The objective of the present study was to investigate the effects of T2DM on bone mass, metabolism, microstructure, and strength in TSOD mice.

METHODS

We determined the following parameters in TSOD mice and Tsumura, Suzuki, Non-obesity (TSNO) mice (as controls): serum glucose levels; serum insulin levels; bone mass; bone microstructure; bone metabolic markers; and bone strength. We also performed the oral glucose tolerance test and examined histological sections of the femur. We compared these data between both groups at pre-diabetic (10 weeks) and established (20 weeks) diabetic conditions.

RESULTS

Bone strength, such as extrinsic mechanical properties, increased with age in the TSOD mice and intrinsic material properties decreased at both 10 weeks and 20 weeks. Bone resorption marker levels in TSOD mice were significantly higher than those in the control mice at both ages, but there was no significant difference in bone formation markers between the groups. Bone mass in TSOD mice was lower than that in controls at both ages. The trabecular bone volume at the femoral greater trochanter increased with age in the TSOD mice. The femoral mid-diaphysis in TSOD mice was more slender and thicker than that in TSNO mice at both ages.

CONCLUSIONS

Bone mass of the femur was lower in TSOD mice than in TSNO mice because hyperinsulinemia during pre-diabetic and established diabetic conditions enhanced bone resorption due to high bone turnover. In addition, our data suggest that the bone mass of the femur was significantly reduced as a result of chronic hyperglycemia during established diabetic conditions in TSOD mice. We suggest that bone strength in the femur deteriorated due to the reduction of bone mass and because the femoral mid-diaphysis was more slender in TSOD mice.

Human amnion-derived mesenchymal stem cells promote osteogenesis of human bone marrow mesenchymal stem cells against glucolipotoxicity

Epidemiological evidence suggests that diabetes mellitus (DM) is an important factor in promoting periodontitis. It not only affects the attachment of connective tissue but also causes loss of alveolar bone. Hence, there is an urgent need to find an effective treatment for DM‐induced bone deficiency. This study aimed to investigate the effects of human amniotic mesenchymal stem cells (HAMSCs) on the proliferation and osteogenic differentiation of DM‐induced human bone marrow mesenchymal stem cells (HBMSCs). High glucose and palmitic acid (GP) were used to mimic DM‐induced glucolipotoxicity. The proliferation levels were measured using flow cytometry. Alkaline phosphatase activity substrate assays, Alizarin red S staining, and western blotting were used to investigate osteogenic differentiation. Oxidative stress was measured by assaying the levels of reactive oxygen species. This study found that glucolipotoxicity caused by GP remarkably inhibited cell proliferation and osteogenesis, and upregulated the oxidative stress level in HBMSCs. However, HAMSCs attenuated HBMSC dysfunction through antioxidant activity by influencing p38 mitogen‐activated protein kinase and vascular endothelial growth factor secretion. In conclusion, our findings indicate that HAMSCs might be suitable for treating DM‐mediated bone deficiency.

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.

An update on the evidence for pathogenic mechanisms that may link periodontitis and diabetes

AIM

To provide an update of the review by Taylor (Journal of Clinical Periodontology, 2013, 40, S113) regarding the scientific evidence of the biological association between periodontitis and diabetes.

METHODS

Literature searches were performed using MeSH terms, keywords and title words and were published between 2012 and November 2016. All publications were screened for their relevance. The data from the articles were extracted and summarized in tables and a narrative review.

RESULTS

Small-scale molecular periodontal microbiome studies indicate a possible association between altered glucose metabolism in pre-diabetes and diabetes and changes in the periodontal microbiome, with no evidence for casual relationships. Clinical and animal studies found elevated gingival levels of IL1-β, TNF-α, IL-6, RANKL/OPG and oxygen metabolites in poorly controlled diabetes. In addition, individuals with diabetes and periodontitis exhibit high levels of circulating TNF-α, CRP and mediators of oxidative stress, and successful periodontal treatment reduces their levels.

CONCLUSIONS

The elevated pro-inflammatory factors in the gingiva of patients with poorly controlled diabetes suggest a biological pathway that may aggravate periodontitis. Some evidence suggests that the systemic inflammatory burden in periodontitis has the potential to affect diabetes control, but no studies addressed the impact of successful periodontal therapy on the pathophysiological mechanisms involved in systemic complications of diabetes.

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

There have been reports that hyperglycemia suppresses osteoclast (OCL) differentiation, although the underlying mechanism is poorly understood. Here we demonstrated that high glucose suppresses OCL differentiation through activation of liver X receptor (LXR) β, a recently reported glucose-sensing nuclear receptor. The effect of hyperglycemia on osteoclastogenesis was tested in RAW264.7 cells, a murine macrophage cell line. Cells were treated with receptor activator of NF-κB ligand (RANKL) under normoglycemic (5.5 mM glucose), normoglycemic with high osmotic pressure (5.5 mM glucose + 10.0 mM mannitol), and hyperglycemic (15.5 mM glucose) conditions. RANKL-induced osteoclastogenesis was significantly suppressed by high-glucose treatment. Mannitol treatment also significantly suppressed osteoclastogenesis, but the inhibitory effect was lower than for high-glucose treatment. The suppression of mRNA expression of Lxrβ by RANKL was significantly restored by high glucose, but not mannitol. Additionally, the deactivation of Lxrβ by siRNA attenuated high-glucose-induced suppression of osteoclastogenesis. Although further validation of the underlying pathway is necessary, targeting LXRβ is a potential therapeutic approach to treating osteoporosis.

Bone defect regeneration and cortical bone parameters of type 2 diabetic rats are improved by insulin therapy

Zucker Diabetic Fatty (ZDF) rats represent an established model of type 2 diabetes mellitus (T2DM) and display several features of human diabetic bone disease, including impaired osteoblast function, decreased bone strength, and delayed bone healing. Here, we determined whether glycemic control by insulin treatment prevents skeletal complications associated with diabetes. Subcritical femur defects were created in diabetic (fa/fa) and non-diabetic (+/+) ZDF rats. Diabetic rats were treated once daily with long-lasting insulin glargin for 12weeks for glycemic control. Insulin treatment successfully maintained serum levels of glycated hemoglobin, while untreated diabetic rats showed a 2-fold increase. Trabecular and cortical bone mass measured by μCT were decreased in diabetic rats. Insulin treatment increased bone mass of the cortical, but not of the trabecular bone compartment. Dynamic histomorphometry revealed a lower bone formation rate at the trabecular and periosteal cortical bone in diabetic animals and decreased serum procollagen type 1 N-terminal propeptide (P1NP, -49%) levels. Insulin treatment partially improved these parameters. In T2DM, serum levels of tartrate-resistant acid phosphatase (TRAP, +32%) and C-terminal telopeptide (CTX, +49%) were increased. Insulin treatment further elevated TRAP levels, but did not affect CTX levels. While diabetes impaired bone defect healing, glycemic control with insulin fully reversed these negative effects. In conclusion, insulin treatment reversed the adverse effects of T2DM on bone defect regeneration in rats mainly by improving osteoblast function and bone formation. This article is part of a Special Issue entitled Bone and diabetes.

Diminished Chondrogenesis and Enhanced Osteoclastogenesis in Leptin-Deficient Diabetic Mice (ob/ob) Impair Pathologic, Trauma-Induced Heterotopic Ossification

Diabetic trauma patients exhibit delayed postsurgical wound, bony healing, and dysregulated bone development. However, the impact of diabetes on the pathologic development of ectopic bone or heterotopic ossification (HO) following trauma is unknown. In this study, we use leptin-deficient mice as a model for type 2 diabetes to understand how post-traumatic HO development may be affected by this disease process. Male leptin-deficient (ob/ob) or wild-type (C57BL/6 background) mice aged 6-8 weeks underwent 30% total body surface area burn injury with left hind limb Achilles tenotomy. Micro-CT (μCT) imaging showed significantly lower HO volumes in diabetic mice compared with wild-type controls (0.70 vs. 7.02 mm(3), P < 0.01) 9 weeks after trauma. Ob/ob mice showed evidence of HO resorption between weeks 5 and 9. Quantitative real time PCR (qRT-PCR) demonstrated high Vegfa levels in ob/ob mice, which was followed by disorganized vessel growth at 7 weeks. We noted diminished chondrogenic gene expression (SOX9) and diminished cartilage formation at 5 days and 3 weeks, respectively. Tartrate-resistant acid phosphatase stain showed increased osteoclast presence in normal native bone and pathologic ectopic bone in ob/ob mice. Our findings suggest that early diminished HO in ob/ob mice is related to diminished chondrogenic differentiation, while later bone resorption is related to osteoclast presence.

Bone remodelling markers in hypertensive patients with and without diabetes mellitus: link between bone and glucose metabolism

OBJECTIVE

Growing evidence suggests the presence of a complex interplay between hypertension as well as type 2 diabetes mellitus (DM) and osteoporosis. The present study was designed to investigate a possible effect of type 2 DM on bone remodelling markers such as osteoprotegerin and N-terminal propeptide of type 1 collagen (P1NP) in hypertensive patients.

DESIGN AND METHODS

The 100 study participants were divided into three groups according to the presence of DM and hypertension: group one included diabetic hypertensive subjects, group 2 included hypertensive subjects without diabetes and group 3 included subjects without hypertension and without DM (controls). Blood sampling for metabolic parameters, including osteoprotegerin, P1NP, adiponectin, fasting glucose, HbA1c , CRP, homeostasis model assessment-insulin resistance, homeostasis model assessment-beta function was performed.

RESULTS

Circulating P1NP increased from group 1 to group 3 in a continuous fashion. P1NP was significantly lower in hypertensive subjects with DM (group 1), than in groups 2 and 3 (p < 0.0001). P1NP, was marginally lower in diabetic hypertensive subjects as compared with nondiabetic subjects with hypertension (p = 0.079). Circulating osteoprotegerin did not differ significantly between groups (p = 0.593).

CONCLUSIONS

In the present study, bone formation marker, P1NP, was significantly lower in diabetic hypertensive subjects as compared with nondiabetic subjects with and without hypertension. P1NP was inversely associated with parameters of glucose homeostasis such as fasting glucose, HbA1c and positively with homeostasis model assessment-beta cell function. Type 2 DM was associated with an adverse effect on bone formation independently of age, sex and exposure to anti-diabetic drugs.

Diabetes and Its Effect on Bone and Fracture Healing

Diabetes mellitus is a metabolic disorder that increases fracture risk, interferes with bone formation, and impairs fracture healing. Type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) both increase fracture risk and have several common features that affect the bone including hyperglycemia and increased advanced glycation end product (AGE) formation, reactive oxygen species (ROS) generation, and inflammation. These factors affect both osteoblasts and osteoclasts leading to increased osteoclasts and reduced numbers of osteoblasts and bone formation. In addition to fracture healing, T1DM and T2DM impair bone formation under conditions of perturbation such as bacteria-induced periodontal bone loss by increasing osteoblast apoptosis and reducing expression of factors that stimulate osteoblasts such as BMPs and growth factors.

Diabetes mellitus related bone metabolism and periodontal disease

Diabetes mellitus and periodontal disease are chronic diseases affecting a large number of populations worldwide. Changed bone metabolism is one of the important long-term complications associated with diabetes mellitus. Alveolar bone loss is one of the main outcomes of periodontitis, and diabetes is among the primary risk factors for periodontal disease. In this review, we summarise the adverse effects of diabetes on the periodontium in periodontitis subjects, focusing on alveolar bone loss. Bone remodelling begins with osteoclasts resorbing bone, followed by new bone formation by osteoblasts in the resorption lacunae. Therefore, we discuss the potential mechanism of diabetes-enhanced bone loss in relation to osteoblasts and osteoclasts.

Influence of Glycemic Control on Peri-Implant Bone Healing: 12-Month Outcomes of Local Release of Bone-Related Factors and Implant Stabilization in Type 2 Diabetics

BACKGROUND

The poor glycemic status seems to be an important factor affecting implant complication rates, including peri-implant bone loss.

PURPOSE

This trial evaluated the influence of glycemic control of type 2 diabetes mellitus (T2DM) patients on implant stabilization and on the levels of bone markers in peri-implant fluid during the healing.

MATERIALS AND METHODS

Systemically healthy patients (SH,n = 19), better-controlled T2DM (BCDM,n = 16), and poorly controlled T2DM (PCDM,n = 16) indicated for implant therapy were recruited. The implant stability quotient (ISQ) was determined at implant placement, 3, 6, and 12 months. Levels of transforming growth factor- β (TGF-β), fibroblast growth factor (FGF), osteopontin (OPN), osteocalcin (OC), and osteoprotegerin (OPG) in the peri-implant fluid were quantified at 15 days, and 3, 6, and 12 months, using the Luminex assay.

RESULTS

OPG and OPN levels were higher in SH at 12 months than at15 days (p < .05), whereas OC and TGF-β were lower in PCDM at 12 months compared with the 15-day and 3-month follow-ups, respectively (p < .05). Inter-group analyses showed lower OPN levels in PCDM compared with SH at 12 months (p < .05). The ISQ was higher at 12 months when compared with baseline and 3 months in SH (p < .05), whereas no differences were observed during follow-up in diabetics, regardless of glycemic control (p > .05). No difference in ISQ was observed among groups over time (p > .05).

CONCLUSION

Poor glycemic control negatively modulated the bone factors during healing, although T2DM, regardless of glycemic status, had no effect on implant stabilization.

Application of VEGFA and FGF-9 enhances angiogenesis, osteogenesis and bone remodeling in type 2 diabetic long bone regeneration

Although bone regeneration is typically a reliable process, type 2 diabetes is associated with impaired or delayed healing processes. In addition, angiogenesis, a crucial step in bone regeneration, is often altered in the diabetic state. In this study, different stages of bone regeneration were characterized in an unicortical bone defect model comparing transgenic type 2 diabetic (db^-/db^-) and wild type (WT) mice in vivo. We investigated angiogenesis, callus formation and bone remodeling at early, intermediate and late time points by means of histomorphometry as well as protein level analyses. In order to enhance bone regeneration, defects were locally treated with recombinant FGF-9 or VEGFA. Histomorphometry of aniline blue stained sections indicated that bone regeneration is significantly decreased in db^-/db^- as opposed to WT mice at intermediate (5 days post operation) and late stages (7 days post operation) of bone regeneration. Moreover, immunohistochemical analysis revealed significantly decreased levels of RUNX-2, PCNA, Osteocalcin and PECAM-1 in db^-/db^- defects. In addition, osteoclastogenesis is impaired in db^-/db^- indicating altered bone remodeling. These results indicate significant impairments in angiogenesis and osteogenesis in type 2 diabetic bones. Importantly, angiogenesis, osteogenesis and bone remodeling could be reconstituted by application of recombinant FGF-9 and, in part, by VEGFA application. In conclusion, our study demonstrates that type 2 diabetes affects angiogenesis, osteogenesis and subsequently bone remodeling, which in turn leads to decreased bone regeneration. These effects could be reversed by local application of FGF-9 and to a lesser degree VEGFA. These data could serve as a basis for future therapeutic applications aiming at improving bone regeneration in the type 2 diabetic patient population.

Osteoclast derivation from mouse bone marrow

Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the organic and inorganic matrices of bone means that they play a key role in regulating skeletal remodeling. Together, osteoblasts and osteoclasts are responsible for the dynamic coupling process that involves both bone resorption and bone formation acting together to maintain the normal skeleton during health and disease. As the principal bone-resorbing cell in the body, changes in osteoclast differentiation or function can result in profound effects in the body. Diseases associated with altered osteoclast function can range in severity from lethal neonatal disease due to failure to form a marrow space for hematopoiesis, to more commonly observed pathologies such as osteoporosis, in which excessive osteoclastic bone resorption predisposes to fracture formation. An ability to isolate osteoclasts in high numbers in vitro has allowed for significant advances in the understanding of the bone remodeling cycle and has paved the way for the discovery of novel therapeutic strategies that combat these diseases. Here, we describe a protocol to isolate and cultivate osteoclasts from mouse bone marrow that will yield large numbers of osteoclasts.

Suppressed bone turnover was associated with increased osteoporotic fracture risks in non-obese postmenopausal Chinese women with type 2 diabetes mellitus

We found that type 2 diabetes mellitus (T2DM) was associated with increased fracture risks in non-obese postmenopausal Chinese women, and suppressed bone turnover might be the underlying mechanism. This is the first study evaluating and explaining the association of T2DM with osteoporotic fracture in Chinese population with such high homogeneity.

INTRODUCTION

The aim of this study was to investigate the association of T2DM with osteoporotic fracture in postmenopausal Chinese women.

METHODS

One thousand four hundred ten postmenopausal women were included and stratified into non-obese population [body mass index (BMI) < 25 kg/m(2)] and obese population (BMI ≥ 25 kg/m(2)). Each type of population was classified into diabetes group, impaired fasting glucose (IFG) group, and normal glucose group. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. Serum C-terminal telopeptide of type I collagen (β-CTX) and serum N-amino terminal prepeptide of type 1 procollagen (P1NP) were quantified. Vertebral fractures (VFs) and non-VFs were assessed by vertebral X-ray and questionnaire, respectively.

RESULTS

Comparing to normal glucose group, diabetes group and IFG group both had lower levels of P1NP and β-CTX, despite population types. Despite having non-decreased BMD, non-obese diabetic patients had higher risks of total fracture and VF than BMI-matched normal glucose subjects (both P < 0.05). Non-obese population was further classified by a mean value of P1NP or β-CTX. Non-obese diabetic patients with low P1NP or high β-CTX had higher fracture risks (both P < 0.05), comparing to non-obese normal glucose subjects with high P1NP or high β-CTX, respectively.

CONCLUSIONS

Type 2 diabetic patients had suppressed bone turnover, which might explain the increased fracture risks, independent of BMD. IFG patients might also have poor bone quality and need early prevention.