The Impact of Type 2 Diabetes on Bone Fracture Healing

Altered Secretome of Diabetic Monocytes Could Negatively Influence Fracture Healing-An In Vitro Study

Diabetes mellitus is a main risk factor for delayed fracture healing and fracture non-unions. Successful fracture healing requires stimuli from different immune cells, known to be affected in diabetics. Especially, application of mononuclear cells has been proposed to promote wound and fracture healing. Thus, aim was to investigate the effect of pre-/diabetic conditions on mononuclear cell functions essential to promote osteoprogenitor cell function. We here show that pre-/diabetic conditions suppress the expression of chemokines, e.g., CCL2 and CCL8 in osteoprogenitor cells. The associated MCP-1 and MCP-2 were significantly reduced in serum of diabetics. Both MCPs chemoattract mononuclear THP-1 cells. Migration of these cells is suppressed under hyperglycemic conditions, proposing that less mononuclear cells invade the site of fracture in diabetics. Further, we show that the composition of cytokines secreted by mononuclear cells strongly differ between diabetics and controls. Similar is seen in THP-1 cells cultured under hyperinsulinemia or hyperglycemia. The altered secretome reduces the positive effect of the THP-1 cell conditioned medium on migration of osteoprogenitor cells. In summary, our data support that factors secreted by mononuclear cells may support fracture healing by promoting migration of osteoprogenitor cells but suggest that this effect might be reduced in diabetics.

Beneficial effect of dietary geranylgeraniol on glucose homeostasis and bone microstructure in obese mice is associated with suppression of proinflammation and modification of gut microbiome

Geranylgeraniol (GGOH) is found in edible oils such as olive, linseed, and sunflower oils, which have favorable metabolic effects. However, it is unknown whether these physiological benefits are mediated through the gut microbiome. Thus, the purpose of this study was to test the hypothesis that GGOH supplementation would improve glucose homeostasis and benefit the bone microstructure in obese mice through suppression of inflammation and modification of gut microbiota composition. Thirty-six male C57BL/6J mice were divided into 3 groups: a low-fat diet, a high-fat diet (HFD), and an HFD supplemented with 800 mg GGOH/kg diet (GG) for 14 weeks. Glucose and insulin tolerance tests were measured at baseline and end of study. The concentrations of adipokine cytokines (resistin, leptin, monocyte chemoattractant protein-1, interleukin-6) were measured via ELISA. Bone microarchitecture and quality were measured by micro-CT. Microbiome analysis was performed using 16S rRNA amplicon sequencing on cecal content. Relative to the HFD group, the GG group: (1) improved glucose tolerance and insulin sensitivity; (2) reduced production of pro-inflammatory adipokines, (3) increased serum procollagen I intact N-terminal propeptide (bone formation marker) concentrations, while decreasing serum collagen type 1 cross-linked C-telopeptide (bone resorption marker) levels, and (4) increased stiffness at both femur and LV-4 and cortical thickness at femoral midshaft. Compared to the HFD group, the GG group had an increased abundance of Butyricicoccus pullicaecorum and decreased Dorea longicatena in the cecal microbiome. Collectively, GGOH improves glucose homeostasis and bone microstructure in obese mice, probably via suppression of pro-inflammation and modification of microbiome composition.

Nicorandil decreases oxidative stress in slow- and fast-twitch muscle fibers of diabetic rats by improving the glutathione system functioning

AIMS/INTRODUCTION

Myopathy is a common complication of any diabetes type, consisting in failure to preserve mass and muscular function. Oxidative stress has been considered one of the main causes for this condition. This study aimed to search if Nicorandil, a KATP channel opener, could protect slow- and fast-twitch diabetic rat muscles from oxidative stress, and to unveil its possible mechanisms.

MATERIALS AND METHODS

Diabetes was induced in male Wistar rats by applying intraperitoneally streptozotocin (STZ) at 100 mg/kg doses. Nicorandil (3 mg/kg/day) was administered along 4 weeks. An insulin tolerance test and assessment of fasting blood glucose (FBG), TBARS, reduced (GSH), and disulfide (GSSG) glutathione levels, GSH/GSSG ratio, and mRNA expression of glutathione metabolism-related genes were performed at end of treatment in soleus and gastrocnemius muscles.

RESULTS

Nicorandil significantly reduced FBG levels and enhanced insulin tolerance in diabetic rats. In gastrocnemius and soleus muscles, Nicorandil attenuated the oxidative stress by decreasing lipid peroxidation (TBARS), increasing total glutathione and modulating GPX1-mRNA expression in both muscle's types. Nicorandil also increased GSH and GSH/GSSG ratio and downregulated the GCLC- and GSR-mRNA in gastrocnemius, without significative effect on those enzymes' mRNA expression in diabetic soleus muscle.

CONCLUSIONS

In diabetic rats, Nicorandil attenuates oxidative stress in slow- and fast-twitch skeletal muscles by improving the glutathione system functioning. The underlying mechanisms for the modulation of glutathione redox state and the transcriptional expression of glutathione metabolism-related genes seem to be fiber type-dependent.

The Effect of Controlled Diabetes and Hyperglycemia on Implant Placement with Simultaneous Horizontal Guided Bone Regeneration: A Clinical Retrospective Analysis

Diabetes represents a challenge in implant therapy because hyperglycemia may negatively affect bone regeneration, directly compromising clinical outcomes and increasing clinical failures. The aim of this retrospective study is to analyse the prognostic significance of HbA1c levels in patients undergoing implant placement associated with horizontal guided bone regeneration. Thirty-four patients were divided into 3 groups according to their HbA1c levels: nondiabetic normoglycemic patients (HbA1c < 5.7%), nondiabetic hyperglycemic patients (HbA1c < 6.5%), and controlled diabetic patients (HbA1c < 7%). Primary outcomes were dimensional changes in height (VDH) and width (DW) of the peri-implant defect. Secondary outcomes were evaluations of periodontal parameters of adjacent tooth sites, wound healing, marginal bone loss (MBL), and survival and success rates. At T₁ (6 months), mean VDH values in groups 1, 2, and 3 were, respectively, 0.07, 0.5, and 0.25 mm. Mean DW values in those same groups were, respectively, 0.07, 0.38, and 0.33 mm. HbA1c levels were not statistically related to VDH and DW values at T₁. No statistically significant differences were observed in MBL between groups (p = 0.230). Implant survival and success rates were, respectively, 98% and 96%. Simultaneous guided bone regeneration is a feasible procedure for the treatment of horizontal bone deficiencies in controlled diabetic patients.

Recurrent mandibular fractures: a retrospective study over 17 years on aetiology, demographics, fracture patterns, and management

Recurrent fractures of the mandible are rare, however in Darwin, Australia, their occurrence is relatively frequent. This retrospective study identified 127 patients with 148 recurrent mandibular fractures treated at Royal Darwin Hospital between 2000 and 2017. Age, sex, ethnicity, marital status, aetiology, risk factors, anatomical location of the fractures, fracture patterns, and management of the fractures were analysed. The majority of patients were male (85.8%) (P < 0.001); 62.8% were unmarried (P < 0.001) and 72.4% were indigenous (P < 0.001). Alcohol was involved in 79.1% of cases (P < 0.001) and assault was the most common mechanism of injury (84.5%) (P < 0.001). The angle of the mandible was the most common site (P < 0.001), and recurrent fractures were more likely to occur at sites different to a previous fracture fixation site (P < 0.001). Smoking, alcohol abuse, and diabetes were strongly associated with recurrent fractures (all P < 0.001). Most patients were managed with open reduction internal fixation. In conclusion, recurrent fractures of the mandible frequently involved the angle of the mandible and occurred at different sites. Their incidence was more common among the unmarried, male, and indigenous population, and smoking, alcohol abuse, and diabetes were found to be significant risk factors.

A Dual Peptide Sustained-Release System Based on Nanohydroxyapatite/Polyamide 66 Scaffold for Synergistic-Enhancing Diabetic Rats' Fracture Healing in Osteogenesis and Angiogenesis

Diabetes mellitus impairs fracture healing and function of stem cells related to bone regeneration; thus, effective bone tissue engineering therapies can intervene with those dysfunctions. Nanohydroxyapatite/polyamide 66 (n-HA/PA66) scaffold has been used in fracture healing, whereas the low bioactivity limits its further application. Herein, we developed a novel bone morphogenetic protein-2- (BMP-2) and vascular endothelial growth factor- (VEGF) derived peptides-decorated n-HA/PA66 (BVHP66) scaffold for diabetic fracture. The n-HA/PA66 scaffold was functionalized by covalent grafting of BMP-2 and VEGF peptides to construct a dual peptide sustained-release system. The structural characteristics and peptide release profiles of BVHP66 scaffold were tested by scanning electron microscopy, Fourier transform infrared spectroscopy, and fluorescence microscope. Under high glucose (HG) condition, the effect of BVHP66 scaffold on rat bone marrow mesenchymal stem cells’ (rBMSCs) adherent, proliferative, and differentiate capacities and human umbilical vein endothelial cells’ (HUVECs) proliferative and tube formation capacities was assessed. Finally, the BVHP66 scaffold was applied to fracture of diabetic rats, and its effect on osteogenesis and angiogenesis was evaluated. In vitro, the peptide loaded on the BVHP66 scaffold was in a sustained-release mode of 14 days. The BVHP66 scaffold significantly promoted rBMSCs’ and HUVECs’ proliferation and improved osteogenic differentiation of rBMSCs and tube formation of HUVECs in HG environment. In vivo, the BVHP66 scaffold enhanced osteogenesis and angiogenesis, rescuing the poor fracture healing in diabetic rats. Comparing with single peptide modification, the dual peptide-modified scaffold had a synergetic effect on bone regeneration in vivo. Overall, this study reported a novel BVHP66 scaffold with excellent biocompatibility and bioactive property and its application in diabetic fracture.

Adiponectin regulates osteocytic MLO-Y4 cell apoptosis in a high-glucose environment through the AMPK/FoxO3a signaling pathway

Clinical studies have shown that persistent hyperglycemia following oxidative stress is associated with the apoptosis of osteocytes in diabetics. Adiponectin (APN) can ameliorate oxidative stress, and its receptors have been identified in bone-forming cells. However, the relationship between APN and osteocyte apoptosis has not been fully elucidated. This study aimed to investigate whether APN could prevent osteocyte apoptosis and regulate reactive oxygen species (ROS) generation in a high-glucose environment. Hoechst staining and fluorescence microscopy were used to observe the apoptosis of osteocytic MLO-Y4 cells. Real-time quantitative polymerase chain reaction and Western blot analysis were used to detect the expression of Caspase 3, Caspase 8, and Bcl-2. ROS generation was investigated with an active oxygen kit and fluorescence microscopy. Furthermore, the expression of proteins in the AMPK/FoxO3A signaling pathway was also studied by Western blot analysis. In a high-glucose environment, APN promoted the proliferation of MLO-Y4 osteocytes and the expression of Bcl-2 but inhibited the expression of Caspase 3, Caspase 8, and ROS in a dose-dependent manner. APN promoted the activation of p-AMPK and p-AMPK/AMPK, which reached their highest levels at 10 min and returned to baseline at 30 min. The expression of p-FoxO3A/FoxO3A in both the cytoplasm and nucleus peaked at 15 min, and this expression was returned to baseline at 60 min. In summary, APN has an antiapoptotic effect and regulates ROS generation in MLO-Y4 osteocytes in a high-glucose environment. The AMPK/FoxO3A signaling pathway might be a key signaling pathway that participates in the effect of APN on regulating osteocyte apoptosis in diabetics.

Recovering the osteoblastic differentiation potential of mesenchymal stem cells derived from diabetic rats by photobiomodulation therapy

Autologous cell-based therapy for bone regeneration might be impaired by diabetes mellitus (DM) due to the negative effects on mesenchymal stem cells (MSCs) differentiation. Strategies to recover their osteogenic potential could optimize the results. We aimed to evaluate the effect of photobiomodulation (PBM) therapy on osteoblast differentiation of rats with induced DM. Bone marrow MSCs of healthy and diabetic rats were isolated and differentiated into osteoblasts (OB and dOB, respectively). dOB were treated with PBM therapy every 72 hour (660 nm; 0.14 J; 20 mW; 0.714 W/cm² , and 5 J/cm² ). Cell morphology, viability, gene and protein expression of osteoblastic markers, alkaline phosphatase (ALP) activity, and the mineralized matrix production of dOB-PBM were compared to dOB. PBM therapy improved viability of dOB, increased the gene and protein expression of bone markers, the ALP activity and the mineralized matrix production. PBM therapy represents an innovative therapeutic approach to optimize the treatment of bone defects in diabetic patients.

Application of Platelet Rich Fibrin in Tissue Engineering: Focus on Bone Regeneration

Bone tissue engineering (BTE) is a strategy for reconstructing bone lesions, which is rapidly developing in response to higher demands for bone repairing. Recently, this method, along with the emergence of functionally graded, biocompatible and biodegradable materials, has been expanded. Moreover, scaffolds with chemical, physical and external patterns have induced bone regeneration. However, the maintenance of healthy bone and its regeneration in the human body needs a series of complex and accurate processes. Hence, many studies have been accompanied for reconstructing bone by using blood-derived biomaterials, especially platelet-rich fabricates. The most important reason for using platelet-rich formulations in bone regeneration is based on releasing growth factors from alpha granules in platelets, which can induce osteogenesis. Moreover, the presence of fibrin nano-fiber structures as a constituent can provide a good substrate for cell attachments. This study attempts to review the history, structure, and biology of platelet-rich fibrin (PRF) as well as in vitro, pre-clinical, and clinical studies on the use of PRF for bone regeneration.

Abnormal macrophage polarization impedes the healing of diabetes-associated tooth sockets

Patients with poorly controlled type 2 diabetes mellitus (T2DM) often experience delayed tooth extraction socket (TES) healing. Delayed healing is often associated with an aberrant inflammatory response orchestrated by either M1 pro-inflammatory or M2 anti-inflammatory macrophages. However, the precise mechanism for the attenuated TES healing remains unclear. Here we used diet-induced T2DM mice as a model to study TES. Compared with the control group, the T2DM group showed delayed TES healing and diminished expression of osteogenic and angiogenic genetic profiles. Meanwhile, we detected a more inflammatory profile, with more M1 macrophages and TNF-α expression and less M2 macrophages and PPARγ expression, in TES in the T2DM group when compared to control mice. In vitro co-culture models showed that M1 macrophages inhibited the osteogenic capacity of bone marrow stromal cells and the angiogenic capacity of endothelial cells while M2 macrophages showed an opposite effect. In addition, we constructed a gelatin/β-TCP scaffold with IL-4 to induce macrophage transformation towards M2 polarization. In vitro analyses of the hybrid scaffold revealed sustained release of IL-4 and a phenotype switch to M2 macrophages. Finally, we demonstrated that sustained IL-4 release significantly increased expression of osteogenic and angiogenic genetic profiles and improved TES healing in T2DM mice. Together, we report that increased M1 and decreased M2 macrophage polarization may be responsible for delayed TES healing in T2DM patients through abnormal expression of TNF-α and PPARγ. This imbalance negatively influences osteogenesis and angiogenesis, two of the most important biological factors in bone wound healing. Enhancing M2 macrophage polarization with IL-4 delivery system may represent a potential strategy for promoting the healing of TES in T2DM patients.

Do polyunsaturated fatty acids protect against bone loss in our aging and osteoporotic population?

Age-related bone loss is inevitable in both men and women and there will soon be more people of extreme old age than ever before. Osteoporosis is a common chronic disease and as the proportion of older people, rate of obesity and the length of life increases, a rise in age-related degenerating bone diseases, disability, and prolonged dependency is projected. Fragility fractures are one of the most severe complications associated with both primary and secondary osteoporosis and current treatment strategies target weight-bearing exercise and pharmacological intervention, both with limited long-term success. Obesity and osteoporosis are intimately interrelated, and diet is a variable that plays a significant role in bone regeneration and repair. The Western Diet is characterized by its unhealthy components, specifically excess amounts of saturated fat intake. This review examines the impact of saturated and polyunsaturated fatty acid consumption on chronic inflammation, osteogenesis, bone architecture, and strength and explores the hypothesis that dietary polyunsaturated fats have a beneficial effect on osteogenesis, reducing bone loss by decreasing chronic inflammation, and activating bone resorption through key cellular and molecular mechanisms in our aging population. We conclude that aging, obesity and a diet high in saturated fatty acids significantly impairs bone regeneration and repair and that consumption of ω-3 polyunsaturated fatty acids is associated with significantly increased bone regeneration, improved microarchitecture and structural strength. However, ω-6 polyunsaturated fatty acids were typically pro-inflammatory and have been associated with an increased fracture risk. This review suggests a potential role for ω-3 fatty acids as a non-pharmacological dietary method of reducing bone loss in our aging population. We also conclude that contemporary amendments to the formal nutritional recommendations made by the Food and Nutrition Board may be necessary such that our aging population is directly considered.

Experimental Type 2 Diabetes Differently Impacts on the Select Functions of Bone Marrow-Derived Multipotent Stromal Cells

Bone marrow-derived multipotent stromal cells (BMMSCs) represent an attractive therapeutic modality for cell therapy in type 2 diabetes mellitus (T2DM)-associated complications. T2DM changes the bone marrow environment; however, its effects on BMMSC properties remain unclear. The present study aimed at investigating select functions and differentiation of BMMSCs harvested from the T2DM microenvironment as potential candidates for regenerative medicine. BMMSCs were obtained from Zucker diabetic fatty (ZDF; an obese-T2DM model) rats and their lean littermates (ZL; controls), and cultured under normoglycemic conditions. The BMMSCs derived from ZDF animals were fewer in number, with limited clonogenicity (by 2-fold), adhesion (by 2.9-fold), proliferation (by 50%), migration capability (by 25%), and increased apoptosis rate (by 2.5-fold) compared to their ZL counterparts. Compared to the cultured ZL-BMMSCs, the ZDF-BMMSCs exhibited (i) enhanced adipogenic differentiation (increased number of lipid droplets by 2-fold; upregulation of the Pparg, AdipoQ, and Fabp genes), possibly due to having been primed to undergo such differentiation in vivo prior to cell isolation, and (ii) different angiogenesis-related gene expression in vitro and decreased proangiogenic potential after transplantation in nude mice. These results provided evidence that the T2DM environment impairs BMMSC expansion and select functions pertinent to their efficacy when used in autologous cell therapies.

Macrophage Control of Incipient Bone Formation in Diabetic Mice

Both soft and hard tissue wound healing are impaired in diabetes. Diabetes negatively impacts fracture healing, bone regeneration and osseointegration of endosseous implants. The complex physiological changes associated with diabetes often manifest in immunological responses to wounding and repair where macrophages play a prominent role in determining outcomes. We hypothesized that macrophages in diabetes contribute toward impaired osseous wound healing. To test this hypothesis, we compared osseous wound healing in the mouse calvaria defect model using macrophages from C57BL/6J and db/db mice to direct osseous repair in both mouse strains. Initial analyses revealed that db/db mice macrophages showed an inflamed phenotype in its resting state. Incipient bone regeneration evaluated by μCT indicated that bone regeneration was relatively impaired in the db/db mouse calvaria and in the calvaria of C57BL/6J mice supplemented with db/db macrophages. Furthermore, osteogenic differentiation of mouse mesenchymal stem cells was negatively impacted by conditioned medium from db/db mice compared to C57BL/6J mice. Moreover, miR-Seq analysis revealed an altered miRNA composition in db/db macrophages with up regulated pro-inflammatory miRNAs and down regulated anti-inflammatory miRNAs. Overall, this study represents a direct step toward understanding macrophage-mediated regulation of osseous bone regeneration and its impairment in type 2 diabetes mellitus.

Obesity regulates miR-467/HoxA10 axis on osteogenic differentiation and fracture healing by BMSC-derived exosome LncRNA H19

This study explored the therapeutic effect of bone marrow mesenchymal stem cell‐derived exosomes on the treatment of obesity‐induced fracture healing. Quantitative real‐time PCR was used to detect the expression of lncRNA H19, miR‐467 and Hoxa10 and combined with WB detection to detect osteogenic markers (RUNX2, OPN, OCN). Determine whether exosomes have entered BMSCs by immunofluorescence staining. Alkaline phosphatase (ALP) and alizarin red staining (ARS) staining were used to detect ALP activity and calcium deposition. We found that high‐fat treatment can inhibit the secretion of BMSCs‐derived exosomes and affect the expression of H19 carried by them. In vivo and in vitro experiments show that high‐fat or obesity factors can inhibit the expression of osteogenic markers and reduce the staining activity of ALP and ARS. The treatment of exosomes from normal sources can reverse the phenomenon of osteogenic differentiation and abnormal fracture healing. Further bioinformatics analysis found that miR‐467 as a regulatory molecule of lncRNA H19 and Hoxa10, and we verified the targeting relationship of the three through dual luciferase report experiments. Further, we found similar phenomena in ALP and ARS staining. Bone marrow mesenchymal stem cell‐derived exosomes improve fracture healing caused by obesity.

Is Decreased Local Bone Quality an Independent Risk Factor for Complications Following Fracture Fixation of Facial Bones

PURPOSE

Although osteoporosis is associated with increased risks of complications of fracture fixation in the orthopedic literature, the association between local bone quality (LBQ) and complications of facial fracture fixation is unknown. The authors aim to identify that if decreased LBQ is an independent risk factor for complications following facial fracture fixation?

METHODS

The authors conducted a prospective cohort study on patients over age of 50 years who underwent open reduction and rigid internal fixation for facial fractures. The primary predictor was LBQ (low or normal), decided by a combination of 3 panoramic indices. Other predictors included age, gender, body mass index (BMI), comorbidities, trauma-related characteristics, etc. The outcome variable was the presence of hardware-related, fracture-healing, wound, or neurosensory complications during 2-year follow-up. Univariate and multivariate regressions were performed to identify any significant association between predictor and outcome variables.

RESULTS

The sample was composed of 69 patients (27 females) with an average age of 58.6 ± 8.6 years and BMI of 25 ± 3.8. Low-LBQ patients were significantly older, more females, had lower BMI, mainly injured from falls, had more complications compared to their normal-LBQ counterparts. However, multivariable logistic regressions demonstrated that only age (adjusted OR: 1.12, P = 0.031, 95% CI: 1.01, 1.23) and diabetes (adjusted OR: 12.63, P = 0.029, 95% CI: 1.3, 122.53) were significantly associated with overall complications after confounding adjustment.

CONCLUSIONS

The results of the present study indicate that reduced LBQ is not an independent risk factor for complications following facial fracture fixation. The increased risk of complications in low-LBQ patients is more likely to be attributed to other age-related comorbidities such as diabetes. Therefore, the authors recommend detailed workup and good control of comorbidities in elderly trauma patient.

Cornelian Cherry Pulp Has Beneficial Impact on Dyslipidemia and Reduced Bone Quality in Zucker Diabetic Fatty Rats

Cornelian cherry (Cornus mas L.) is a medicinal plant with a range of biological features. It is often used as a nutritional supplement in the treatment of diabetes mellitus. Our study was aimed to first investigate the effects of Cornelian cherry pulp on bone quality parameters in Zucker diabetic fatty (ZDF) rats. Moreover, lipid-lowering properties of this fruit were also evaluated. Adult rats (n = 28) were assigned into four groups of seven individuals each: L group (non-diabetic lean rats), C group (diabetic obese rats), and E1 and E2 groups (diabetic obese rats receiving 500 and 1000 mg/kg body weight of Cornelian cherry pulp, respectively, for 10 weeks). Significantly lower levels of triglyceride, total cholesterol and alkaline phosphatase activity were determined in the E2 group versus the C group. A higher dose of Cornus mas also had a beneficial impact on femoral weight, cortical bone thickness, relative volume of trabecular bone and trabecular thickness. We observed elevated density of Haversian systems and accelerated periosteal bone apposition in both treated groups (E1 and E2). Our results clearly demonstrate that Cornelian cherry pulp has a favorable effect on lipid disorder and impaired bone quality consistent with type 2 diabetes mellitus in a suitable animal model.

Individuals with type 2 diabetes mellitus show dimorphic and heterogeneous patterns of loss in femoral bone quality

Type 2 diabetes mellitus (T2DM), a metabolic disease on the rise, is associated with substantial increase in bone fracture risk. Because individuals with T2DM have normal or high bone mineral density (BMD), osteodensitometric measurements of BMD do not predict fracture risk with T2DM. Here, we aim to identify the underlying mechanism of the diabetes-induced fracture risk using a high-resolution multi-scale analysis of human cortical bone with special emphasis on osseous cellular activity. Specifically, we show increased cortical porosity in a subgroup of T2DM individuals accompanied by changed mineralization patterns and glycoxidative damage to bone protein, caused by non-enzymatic glycation of bone by reducing sugar. Furthermore, the high porosity T2DM subgroup presents with higher regional mineralization heterogeneity and lower mineral maturity, whereas in the T2DM subgroup regional higher mineral-to-matrix ratio was observed. Both T2DM groups show significantly higher carboxymethyl-lysine accumulation. Our results show a dimorphic pattern of cortical bone reorganization in individuals afflicted with T2DM and hence provide new insight into the diabetic bone disease leading to increased fracture risk.

Alteration of the Condylar Oral Bone in Obese and Gastric Bypass Mice

Obesity is the main cause of type 2 diabetes mellitus (T2DM). Roux-en-Y gastric bypass (RYGB) surgery is an effective treatment for this obesity-related health problem. However, the adverse effects of T2DM on bone tissue persist or even aggravate after this surgical procedure. As studies on the mandibular condyle bone are scarce, the aim of the present study was to assess its compositional characteristics in T2DM and RYGB conditions. Thirty-two male C57BL/6 mice at 8 weeks of age were randomly assigned to receive either a high-fat or low-fat diet. After 14 weeks of high-fat diet intake, seven obese mice were subjected to RYGB surgery. All animals were euthanized at the age of 30 weeks. Mandibular bones were removed and the trabecular condyle region was assessed using Raman spectroscopy. A decreased mineralization was observed for both T2DM and RYGB condyle bones when compared to controls, with elevated carbonate substitutions for the RYGB group. No compositional differences in crystallinity and presence of advanced glycation end products were found between the groups, with the exception of an increased presence of N-carboxymethyl-lysine in RYGB bone compared to their T2DM counterpart. Site-specific measurements revealed a non-uniform bone composition, with increasing mineralization and carbonate substitutions towards the centre of the mandibular condyle. T2DM and RYGB surgery affect the mandibular condyle bone quality, as investigated at compositional level. Assessment of bone structural properties and remodelling should be carried out to further explore the effects of T2DM and RYGB surgery on this skeleton area.

Proton pump inhibitor use and risk of hip fracture in patients with type 2 diabetes

Type 2 diabetes mellitus (T2DM) is associated with a high rate of comorbidity, including osteoporosis and peptic ulcers. Proton pump inhibitors (PPIs) are a group of acid-suppressing drugs commonly used for treating peptic ulcers. However, observational studies have reported an association between PPI therapy and osteoporotic fractures. This study investigated the association between PPI use and hip fracture (HFx) among patients with T2DM. We conducted this population-based propensity-matched retrospective cohort study using the National Health Insurance Research Database in Taiwan. Patients newly diagnosed with T2DM between 2000 and 2008 were identified. After excluding those who previously used PPIs or suffered HFx, 398,885 patients were recruited (44,341 PPI users; 354,544 non-users). HFx risk data from 2000 to 2013 were collected to calculate the cumulative rate of HFx in these two groups. Sensitivity analyses were conducted to evaluate the effects of PPI dose. After propensity score matching of 1:4, 44,431 and 177,364 patients were assigned to the PPI user and non-user groups, respectively. PPI user group showed an increased risk of HFx with an adjusted hazard ratio of 1.41 (95% CI 1.29–1.54) without dose–response relationship. Thus, there is an increased risk of HFx in patients with T2DM receiving long-term PPI treatment.

Aberrant structure of fibrillar collagen and elevated levels of advanced glycation end products typify delayed fracture healing in the diet-induced obesity mouse model

Impaired fracture healing in patients with obesity-associated type 2 diabetes (T2D) is a significant unmet clinical problem that affects millions of people worldwide. However, the underlying causes are poorly understood. Additionally, limited clinical information is available on how pre-diabetic hyperglycemia in obese individuals impacts bone healing. Here, we use the diet-induced obesity (DIO) mouse (C57BL/6J) model to study the impact of obesity-associated pre-diabetic hyperglycemia on bone healing and fibrillar collagen organization as healing proceeds from one phase to another. We show that DIO mice exhibit defective healing characterized by reduced bone mineral density, bone volume, and bone volume density. Differences in the healing pattern between lean and DIO mice occur early in the healing process as evidenced by faster resorption of the fibrocartilaginous callus in DIO mice. However, the major differences between lean and DIO mice occur during the later phases of endochondral ossification and bone remodeling. Comprehensive analyses of fibrillar collagen microstructure and expression pattern during these phases, using a set of complementary techniques that include histomorphometry, immunofluorescence staining, and second harmonic generation microscopy, demonstrate significant defects in DIO mice. Defects include strikingly sparse and disorganized collagen fibers, as well as pathological accumulation of unfolded collagen triple helices. We also demonstrate that DIO-associated changes in fibrillar collagen structure are attributable, at least in part, to the accumulation of advanced glycation end products, which increase the collagen-fiber crosslink density. These major changes impair fibrillar collagens functions, culminating in defective callus mineralization, remodeling, and strength. Our data extend the understanding of mechanisms by which obesity and its associated hyperglycemia impair fracture healing and underline defective fibrillar collagen microstructure as a novel and important contributor.

Impact of Astaxanthin on Diabetes Pathogenesis and Chronic Complications

Oxidative stress (OS) plays a pivotal role in diabetes mellitus (DM) onset, progression, and chronic complications. Hyperglycemia-induced reactive oxygen species (ROS) have been shown to reduce insulin secretion from pancreatic β-cells, to impair insulin sensitivity and signaling in insulin-responsive tissues, and to alter endothelial cells function in both type 1 and type 2 DM. As a powerful antioxidant without side effects, astaxanthin (ASX), a xanthophyll carotenoid, has been suggested to contribute to the prevention and treatment of DM-associated pathologies. ASX reduces inflammation, OS, and apoptosis by regulating different OS pathways though the exact mechanism remains elusive. Based on several studies conducted on type 1 and type 2 DM animal models, orally or parenterally administrated ASX improves insulin resistance and insulin secretion; reduces hyperglycemia; and exerts protective effects against retinopathy, nephropathy, and neuropathy. However, more experimental support is needed to define conditions for its use. Moreover, its efficacy in diabetic patients is poorly explored. In the present review, we aimed to identify the up-to-date biological effects and underlying mechanisms of ASX on the ROS-induced DM-associated metabolic disorders and subsequent complications. The development of an in-depth research to better understand the biological mechanisms involved and to identify the most effective ASX dosage and route of administration is deemed necessary.

Effect of the Abnormal Expression of BMP-4 in the Blood of Diabetic Patients on the Osteogenic Differentiation Potential of Alveolar BMSCs and the Rescue Effect of Metformin: A Bioinformatics-Based Study

The success rate of oral implants is lower in type 2 diabetes mellitus (T2DM) patients than in nondiabetic subjects; functional impairment of bone marrow-derived mesenchymal stem cells (BMSCs) is an important underlying cause. Many factors in the blood can act on BMSCs to regulate their biological functions and influence implant osseointegration, but which factors play important negative roles in T2DM patients is still unclear. This study is aimed at screening differentially expressed genes in the blood from T2DM and nondiabetic patients, identifying which genes impact the osteogenic differentiation potential of alveolar BMSCs in T2DM patients, exploring drug intervention regimens, and providing a basis for improving implant osseointegration. Thus, a whole-blood gene expression microarray dataset (GSE26168) of T2DM patients and nondiabetic controls was analyzed. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) results, differentially expressed genes and signaling pathways related to BMSC osteogenic differentiation were screened, and major risk genes were extracted based on the mean decrease Gini coefficient calculated using the random forest method. Bone morphogenetic protein-4 (BMP-4), with significantly low expression in T2DM blood, was identified as the most significant factor affecting BMSC osteogenic differentiation potential. Subsequently, metformin, a first-line clinical drug for T2DM treatment, was found to improve the osteogenic differentiation potential of BMSCs from T2DM patients via the BMP-4/Smad/Runx2 signaling pathway. These results demonstrate that low BMP-4 expression in the blood of T2DM patients significantly hinders the osteogenic function of BMSCs and that metformin is effective in counteracting the negative impact of BMP-4 deficiency.

Functionally engineered extracellular vesicles improve bone regeneration

Lineage specific differentiation of host mesenchymal stem cells (MSCs) is a necessary step for bone repair/regeneration. Clinically, growth factors such as bone morphogenetic protein 2 (BMP2) are used to enhance/hasten this process to heal critical sized defects. However, the clinical application of such growth factors is fraught with dosage challenges as well as immunological and ectopic complications. The identification of extracellular vesicles (EVs) as active components of the MSC secretome suggest alternative approaches to enhancing bone regeneration. Based on our earlier studies on the properties of EVs from lineage specified MSCs, this study sought to engineer EVs to enhance osteogenic differentiation. To generate MSC EVs with enhanced osteoinductive abilities, genetically modified human bone marrow derived MSCs (HMSCs) were generated by constitutively expressing BMP2. We hypothesized that these cells would generate functionally engineered EVs (FEEs) with enhanced osteoinductive properties. Our results show that these FEEs maintained the general physical and biochemical characteristics of naïve HMSC EVs in the form of size distribution, EV marker expression and endocytic properties but show increased bone regenerative potential compared to MSC EVs in a rat calvarial defect model in vivo. Mechanistic studies revealed that although BMP2 was constitutively expressed in the parental cells, the corresponding EVs (FEEs) do not contain BMP2 protein as an EV constituent. Further investigations revealed that the FEEs potentiate the BMP2 signaling cascade possibly due to an altered miRNA composition. Collectively, these studies indicate that EVs' functionality may be engineered by genetic modification of the parental MSCs to induce osteoinduction and bone regeneration. SIGNIFICANCE STATEMENT: With mounting evidence for the potential of MSC EVs in treatment of diseases and regeneration of tissues, it is imperative to evaluate if they can be modified for application specificity. The results presented here indicate the possibility for generating Functionally Engineered EVs (FEEs) from MSC sources. As a proof of concept approach, we have shown that EVs derived from genetically modified MSCs (BMP2 overexpression) can be effective as biomimetic substitutes for growth factors for enhanced tissue-specific regeneration (bone regeneration) in vivo. Mechanistic studies highlight the role of EV miRNAs in inducing pathway-specific changes. We believe that this study will be useful to researchers evaluating EVs for regenerative medicine applications.

Morphological Characteristics and Correction of Long Tubular Bone Regeneration under Chronic Hyperglycemia Influence

Introduction

Unsatisfactory consequences of bone regeneration disorders in diabetes mellitus (DM) patients, their high prevalence, complication number, and difficulties in treatment require further study and deeper understanding of reparative osteogenesis mechanisms under chronic hyperglycemia and finding new effective and affordable approaches to their treatment. Therefore, the aim of our work was to study the histological, ultramicroscopic, and histomorphometric features of reparative osteogenesis in rats with chronic hyperglycemia (CH), as well as to investigate the possibility of platelet-rich plasma (PRP) use in a fracture area in order to correct the negative effects of CH on reparative osteogenesis processes. Study Object and Methods. The studies were performed on 70 white laboratory rats, mature males, which were divided into the following groups: control group, animals with posttraumatic tibial defect under conditions of CH exposure, rats with experimental CH that were administered with PRP into the bone defect, and animals for the assessment of glucose homeostasis and confirmation of simulated CH. Light microscopy was performed using an Olympus BH-2 microscope (Japan). Ultramicroscopic examination was performed using REM-102 scanning electron microscope. The statistical analysis was performed using SPSS-17 software package.

Results

The formation of new bone tissue in animals with CH did not occur after two weeks. Only on the 30th day of reparative osteogenesis the newly formed woven bone tissue was 61.54% of the total regenerated area. It was less than the reference value by 22.89% (P < 0.001). On the 14th day of reparative osteogenesis, the regenerated area in a group of animals with CH and PRP injection consisted of connective tissue by 68.94% (4.94% less than in animals with CH (P < 0.001)) and woven bone tissue by 31.06%, (13.51% less than in the control group (P < 0.001)). On the 30th day, the area of woven bone tissue in a regenerate of this group was less than that of the control group by 12.41% (P < 0.001).

Conclusion

Thus, chronic hyperglycemia contributes to inflammation delay within the bone defect site, which makes the process of reparative osteogenesis more prolonged. The results of chronic hyperglycemia effect on bone regeneration are also impairment of osteogenic cell proliferation and shift of their differentiation towards the fibrocartilage regenerate formation. The PRP corrects the negative impact of chronic hyperglycemia on reparative osteogenesis, promoting more rapid inflammatory infiltrate removal from the bone defect site and osteogenic beam formation and remodeling of woven bone into lamellar membranous bone tissue.

Inhibition of GDF11 could promote bone healing in the tooth extraction socket and facilitate mesenchymal stem cell osteogenic differentiation in T2DM pigs

BACKGROUND

Growth differentiation factor 11 (GDF11) might be a key factor responsible for the weakening of mesenchymal stem cell (MSC) osteogenic differentiation in tooth extraction sockets in patients with type 2 diabetes mellitus (T2DM). This study aimed to confirm that inhibition of GDF11 could promote bone healing in tooth extraction sockets and facilitate MSC osteogenic differentiation under T2DM conditions.

METHODS

Three streptozotocin-induced T2DM pig models and two control pig models were established. The T2DM pigs were treated with an intrasocket injection of GDF11 inhibitor in the left mandible, whereas the right side was maintained for natural healing. The postextraction socket healing of the T2DM pigs was compared with that of nondiabetic controls. Healing was quantitatively verified by microcomputed tomography, and the GDF11 expression level was detected. MSCs from T2DM pig sockets were cultured and treated with a GDF11 inhibitor. The osteogenic differentiation ability of MSCs was also compared among groups.

RESULTS

The expression of GDF11 in the tooth extraction sockets from T2DM pigs increased significantly post extraction. Bone healing was promoted by periodic injection of the GDF11 inhibitor into the extraction sockets of T2DM pigs. Furthermore, the osteogenic differentiation ability of T2DM-MSCs was improved in pigs treated with the GDF11 inhibitor.

CONCLUSIONS

GDF11 inhibition could promote bone healing in the tooth extraction socket and facilitate MSC osteogenic differentiation under T2DM conditions. GDF11 could be a potential therapeutic target for undesirable alveolar bone healing in T2DM patients.

Osteoprotegerin in diabetic osteopathy

AIM

The aim of this study is to evaluate the relationship between OPG and the degree of glycaemic control in a population of elderly subjects.

METHODS AND RESULTS

Data presented included 172 elderly subjects, of whom 107 were hospitalized for a hip fracture and 65 were non fractured outpatients. All participants received a multidimensional geriatric evaluation and underwent blood sampling. HbA1c, OPG, CTX and OC were measured and DXA scans were performed. Carotid intima-media thickness (IMT) was measured in all outpatients. Diabetic patients had more comorbidities, higher mean values of lumbar spine and femoral neck BMD and T-score, lower circulating levels of OC and CTX, and higher circulating levels of OPG compared to non-diabetic subjects. OPG was directly correlated with HbA1c. This association was most evident in non-fractured elderly subjects. Moreover, diabetic patients with IMT>1.5 mm had greater mean values of OPG than non-diabetic subjects with high IMT and than elderly subjects with IMT < 1.5 mm, with and without T2DM.

CONCLUSIONS

Diabetic patients have reduced circulating levels of OC and CTX, and elevated serum levels of OPG, suggesting a state of low bone turnover. Reduced bone turnover causes an increase of BMD and could lead to a poor bone quality. OPG and HbA1c were directly correlated and OPG mean values were higher in diabetic patients with poor glucose control. Diabetic osteopathy could be considered a late complication of T2DM, directly related with the degree of glucose control and the duration of the disease.

A Study of the Relationship between the Polymorphism and Mutation of rs682429 and rs3781590 in the LRP5 Gene and Bone Metabolism in Postmenopausal Type 2 Diabetic Women in Xinjiang

OBJECTIVE

To explore the expression of the polymorphism and mutation of rs682429 and rs3781590 in the low-density lipoprotein receptor-related protein 5 (LRP5) genotype and to analyse the relationship of bone mineral density (BMD) and bone metabolism markers in postmenopausal women with type-2 diabetes mellitus (T2DM) in Xinjiang, China, to provide a basis for prevention and treatment of the disease.

METHODS

A total of 136 postmenopausal women were included in the study. According to the results of an oral glucose tolerance test (OGTT) and dual-energy X-ray (DEXA) determination of BMD, the study subjects were divided into 4 groups: group A: normal OGTT+normal bone mass group; group B: normal OGTT+osteoporotic (OP) group; group C: T2DM+normal bone mass group; group D: T2DM+osteoporotic (OP) group. Calcium (Ca), phosphorus (P), alkaline phosphatase (ALP), and clinical biochemical data were determined; haemoglobin A1c (HbA1c) was measured by HPLC; BMD of the femoral neck, hip, and lumbar spine (L1-4) was measured by dual-energy X-ray (DEXA); and the rs682429 and rs3781590 polymorphisms of the LRP5 gene were detected by time-of-flight mass spectrometry (TOF MS).

RESULTS

(1) The rs682429 polymorphism of the LRP5 genotype distribution was statistically significant (P < 0.05) in group B compared with group A. (2) The triglycerides (TG) of women with the CT/TT genotype (mutant type) were higher than those of women with the CC genotype (wild type) (2.37 ± 1.30 vs. 1.52 ± 0.83, P < 0.05) at the rs3781590 site of the LRP5 gene in group D. (3) Multiple linear regression analysis showed that TG (β = 0.034, P < 0.05) and body mass index (BMI) (β = 0.013, P < 0.05) were the influencing factors of BMD (L1-4) in T2DM patients. TG (β = 0.022, P < 0.05), BMI (β = 0.009, P < 0.05), and duration of menopause (β = 0.005, P < 0.05) were the influencing factors of BMD (hip).

CONCLUSION

(1) The rs682429 polymorphism site in the LRP5 gene may be involved in bone metabolism in postmenopausal women from Xinjiang. (2) The rs3781590 mutation in the LRP5 gene from these subjects may be involved in lipid metabolism. (3) Among postmenopausal women with type 2 diabetes mellitus and bone mass abnormality in the Xinjiang Shihezi area, high BMI and TG are protective factors against increased BMD. Duration of menopause is a risk factor for increased BMD.

Effect of gomisin A on osteoblast differentiation in high glucose-mediated oxidative stress

BACKGROUND

Gomisin A is a lignan isolated from the hexane of Schisandra chinensis fruit extract with antioxidant properties. Oxidative stress mediated by high glucose is one of the major complications of diabetes mellitus.

PURPOSE

This study investigates the role of gomisin A in osteoblast differentiation under high glucose-induced oxidative stress in MC3T3 E1 cells and determines its relationship with heme oxygenase-1 (HO-1) and mitochondrial biogenesis.

METHODS

MC3T3 E1 cells were treated by gomisin A following induced by high glucose levels and glucose oxidase to investigate the inhibitory effect of gomisin A against high glucose oxidative stress. Western blot analysis, alizarin red staining, alkaline phosphatase (ALP) activity, analysis of reactive oxygen species (ROS) and confocal microscopy were used to determine mitochondrial biogenesis, oxidative stress, osteoblast differentiation and mineralization. To analyze the role of HO-1, the MC3T3 E1 cells were treated with the HO-1 inhibitor zinc protoporphyrin IX (ZnPP).

RESULTS

Gomisin A enhanced the expression of HO-1, increased mitochondrial biogenesis factors (peroxisome proliferator-activated receptor gamma coactivator 1-alpha, nuclear respiratory factor-1, and mitochondrial transcription factor A), antioxidant enzymes (copper-zinc superoxide dismutases and manganese superoxide dismutase), osteoblast differentiation molecules (bone morphogenic protein-2/7, osteoprotegerin and Runt-related transcription factor-2) and mineralization by upregulation of ALP and alizarin red staining, which were decreased by ZnPP and high glucose oxidative stress. Similarly, gomisin A inhibited ROS which was increased by ZnPP and the high glucose-mediated oxidative stress.

CONCLUSIONS

The findings demonstrated the antioxidative effects of gomisin A, and its role in mitochondrial biogenesis and osteoblast differentiation. It potentially regulated osteoblast differentiation under high glucose-induced oxidative stress via upregulation of HO-1 and maintenance of mitochondrial homeostasis. Thus, gomisin A may represent a potential therapeutic agent for prevention of bone fragility fractures and implant failure triggered by diabetes.

Inhibition of microRNA-222 up-regulates TIMP3 to promotes osteogenic differentiation of MSCs from fracture rats with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is the most common diabetes and has numerous complications. Recent studies demonstrated that T2DM compromises bone fracture healing in which miR-222 might be involved. Furthermore, tissue inhibitor of metalloproteinase 3 (TIMP-3) that is the target of miR-222 accelerates fracture healing. Therefore, we assume that miR-222 could inhibit TIMP-3 expression. Eight-week-old rats were operated femoral fracture or sham, following the injection of streptozotocin (STZ) to induce diabetes one week later in fractured rats, and then, new generated tissues were collected for measuring the expression of miR-222 and TIMP-3. Rat mesenchymal stem cells (MSCs) were isolated and treated with miR-222 mimic or inhibitor to analyse osteogenic differentiation. MiR-222 was increased in fractured rats and further induced in diabetic rats. In contrast, TIMP-3 was reduced in fractured and further down-regulated in diabetic rats. Luciferase report assay indicated miR-222 directly binds and mediated TIMP-3. Furthermore, osteogenic differentiation was suppressed by miR-222 mimic and promoted by miR-222 inhibitor. miR-222 is a key regulator that is promoted in STZ-induced diabetic rats, and it binds to TIMP3 to reduce TIMP-3 expression and suppressed MSCs' differentiation.

Glucagon-like peptide-1 receptor agonists and risk of bone fracture in patients with type 2 diabetes: A meta-analysis of randomized controlled trials

AIMS

To evaluate the association between glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and the risk of bone fracture in patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

We conducted a systematic literature search in PubMed, Embase, the Cochrane Library, and Web of Science from inception to 28 February 2018 and identified eligible randomized controlled trials. The following data were extracted from each study: first author, year of publication, sample size, patient characteristics, study design, intervention drug, control drug, follow-up time, and incident bone fracture events. A meta-analysis was conducted using Review Manager 5.3 software to calculate the odds ratio (OR) and 95% confidence intervals (CI) for dichotomous variables.

RESULTS

A total of 38 studies with 39 795 patients with T2DM were included. There were 241 incident bone fracture cases (107 in the GLP-1 RAs group and 134 in the control group). Compared with patients who received placebo and other anti-diabetic drugs, those who received GLP-1 RAs treatment showed a pooled OR of 0.71 (95% CI, 0.56-0.91) for bone fracture. Subgroup analysis showed that treatments with liraglutide and lixisenatide were associated with significantly reduced risk of bone fractures (ORs, 0.56; 95% CI, 0.38-0.81 and 0.55; 95% CI, 0.31-0.97, respectively). However, other GLP-1 RAs did not show superiority to placebo or other anti-diabetic drugs. Moreover, these beneficial effects were dependent on the duration of GLP-1 RAs treatment, only a GLP-1 RAs treatment period of more than 52 weeks could significantly lower the risk of bone fracture in patients with T2DM (OR, 0.71; 95% CI, 0.56-0.91).

CONCLUSIONS

Compared with placebo and other anti-diabetic drugs, liraglutide and lixisenatide were associated with a significant reduction in the risk of bone fractures, and the beneficial effects were dependent on the duration of treatment.

Role of Nrf2 in Fracture Healing: Clinical Aspects of Oxidative Stress

Fracture healing is a natural process that recapitulates embryonic skeletal development. In the early phase after fracture, reactive oxygen species (ROS) are produced under inflammatory and ischemic conditions due to vessel injury and soft tissue damage, leading to cell death. Usually, such damage during the course of fracture healing can be largely prevented by protective mechanisms and functions of antioxidant enzymes. However, intrinsic oxidative stress can cause excessive toxic radicals, resulting in irreversible damage to cells associated with bone repair during the fracture healing process. Clinically, patients with type-2 diabetes mellitus, osteoporosis, habitual drinkers, or heavy smokers are at risk of impaired fracture healing due to elevated oxidative stress. Although increased levels of oxidative stress markers upon fracture and effects of antioxidants on fracture healing have been reported, a detailed understanding of what causes impaired fracture healing under intrinsic conditions of oxidative stress is lacking. Nuclear factor erythroid 2-related factor 2 (Nrf2) has been identified as a key transcriptional regulator of the expression of antioxidants and detoxifying enzymes. It further not only plays a crucial role in preventing degenerative diseases in multiple organs, but also during fracture healing. This narrative review evaluates the influence of intrinsic oxidative stress on fracture healing and sheds new light on the intriguing role of Nrf2 during bone regeneration in pathological fractures.

Impact of Diabetes Mellitus on Bone Health

Long-term exposure to a diabetic environment leads to changes in bone metabolism and impaired bone micro-architecture through a variety of mechanisms on molecular and structural levels. These changes predispose the bone to an increased fracture risk and impaired osseus healing. In a clinical practice, adequate control of diabetes mellitus is essential for preventing detrimental effects on bone health. Alternative fracture risk assessment tools may be needed to accurately determine fracture risk in patients living with diabetes mellitus. Currently, there is no conclusive model explaining the mechanism of action of diabetes mellitus on bone health, particularly in view of progenitor cells. In this review, the best available literature on the impact of diabetes mellitus on bone health in vitro and in vivo is summarised with an emphasis on future translational research opportunities in this field.

Lentiviral‑mediated Shh reverses the adverse effects of high glucose on osteoblast function and promotes bone formation via Sonic hedgehog signaling

Patients with diabetes tend to have an increased incidence of osteoporosis, which may be associated with hyperglycemia; however, the pathogenic mechanisms governing this interaction remain unknown. The present study sought to investigate whether elevated extracellular glucose levels of bone mesenchymal stem cells (BMSCs) could influence osteoblastic differentiation and whether the intracellular Sonic hedgehog (Shh) pathway could adjust the effects. Furthermore, to verify the results in vivo, a rat tooth extraction model was constructed. BMSCs were incubated in eight types of culture medium, including low glucose (LG), LG + lentivirus (Lenti), LG + Lenti-small interfering RNA (Lenti-siRNA), LG + Lenti-Shh, high glucose (HG), HG + Lenti, HG + Lenti-siRNA and HG + Lenti-Shh. The lentiviral transfection efficiency was observed using a fluorescence microscope; protein and mRNA expression was detected by western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The matrix mineralization and alkaline phosphatase (ALP) activity of BMSCs were examined by Alizarin red staining and ALP activity assays, respectively. The expression of osteogenesis-related genes in BMSCs were quantified by RT-qPCR. The alveolar ridge reduction was measured and histological sections were used to evaluate new bone formation in the tooth socket. With high concentrations of glucose, Shh expression, matrix mineralization nodules formation, ALP activity and the levels of bone morphogenic protein 4 (BMP4), bone sialoprotein (BSP) and osteopontin (OPN) expression were greatly reduced compared with LG and corresponding control groups. Whereas activated Shh signaling via Lenti-Shh could increase the number of matrix mineralization nodules, ALP activity, and the expression levels of BMP4, BSP and OPN in BMSCs. Additionally, in vivo assays demonstrated that Lenti-Shh induced additional bone formation. Collectively, the results of the present study indicated that HG inhibited the Shh pathway in osteoblasts and resulted in patterning defects during osteoblastic differentiation and bone formation, while the activation of Shh signaling could suppress these deleterious effects.

The Synergic Effect of Terpenoid and Steroidal Saponins Can Improve Bone Healing, by Promoting the Osteogenic Commitment of Adipose Mesenchymal Stem Cells: An In Vitro Study

Bone regeneration involves several biological processes that consistently impact the quality of tissue healing. An important step consists of the local recruitment and differentiation of mesenchymal stem cells that migrate in the site to regenerate from bone marrow. Mesenchymal stem cells (MSCs) may be pushed towards osteogenic commitment by specific substances, often naturally present in plants. Yunnan Baiyao (YB) is a Chinese herbal medicine, mainly working through the synergic effect of terpenoid and steroidal saponins. YB is well known for its numerous biomedical effects, including the ability to favor improved bone tissue healing. In our in vitro study, we used adipose mesenchymal stem cells (ADSCs) as a study-model: We selected samples to harvest and isolate ADSCs and investigate their viability; moreover, we performed bone-related gene expression to evaluate the differentiation of MSCs. To confirm this behavior, we analyzed alkaline phosphate activity and calcium deposition, with ADSCs cultured in basal and osteogenic media, with YB at different concentrations in the medium, and at different time-points: 7, 14 and 21 days. Our results indicate that the synergic effect of terpenoid and steroidal saponins slightly favor the late ADSCs differentiation towards the osteoblasts phenotype. In osteogenic committed cells, the treatment with the lower dose of YB promoted the up-regulation of the alkaline phosphatase gene (ALPL) at day seven and 14 (p < 0.01); at day 21, the alkaline phosphatase (ALP) activity showed a slight increase, although in basal condition it maintains low rates. We assume that such molecular synergy can promote the osteogenic commitment of adipose mesenchymal stem cells, thus improving the timing and the quality of bone healing.

Local Application of Semaphorin 3A Combined with Adipose-Derived Stem Cell Sheet and Anorganic Bovine Bone Granules Enhances Bone Regeneration in Type 2 Diabetes Mellitus Rats

Bone tissue regeneration is considered to be the optimal solution for bone loss. However, diabetic patients have a greater risk of poor bone healing or bone grafting failure than nondiabetics. The purpose of this study was to investigate the influence of the complexes of an adipose-derived stem cell sheet (ASC sheet) and Bio-Oss® bone granules on bone healing in type 2 diabetes mellitus (T2DM) rats with the addition of semaphorin 3A (Sema3A). The rat ASC sheets showed stronger osteogenic ability than ASCs in vitro, as indicated by the extracellular matrix mineralization and the expression of osteogenesis-related genes at mRNA level. An ASC sheet combined with Bio-Oss® bone granules promoted bone formation in T2DM rats as indicated by microcomputed tomography (micro-CT) and histological analysis. In addition, Sema3A promoted the osteogenic differentiation of ASC sheets in vitro and local injection of Sema3A promoted T2DM rats' calvarial bone regeneration based on ASC sheet and Bio-Oss® bone granule complex treatment. In conclusion, the local injection of Sema3A and the complexes of ASC sheet and Bio-Oss® bone granules could promote osseous healing and are potentially useful to improve bone healing for T2DM patients.

Molecular mechanisms linking peri-implantitis and type 2 diabetes mellitus revealed by transcriptomic analysis

Aims

To explore molecular mechanisms that link peri-implantitis and type 2 diabetes mellitus (T2DM) by bioinformatic analysis of publicly available experimental transcriptomic data.

Materials and methods

Gene expression data from peri-implantitis were downloaded from the Gene Expression Omnibus database, integrated and differentially expressed genes (DEGs) in peri-implantitis were identified. Next, experimentally validated and computationally predicted genes related to T2DM were downloaded from the DisGeNET database. Protein–protein interaction network (PPI) pairs of DEGs related to peri-implantitis and T2DM related genes were constructed, “hub” genes and overlapping DEG were determined. Functional enrichment analysis was used to identify significant shared biological processes and signaling pathways. The PPI networks were subjected to cluster and specific class analysis for identifying “leader” genes. Module network analysis of the merged PPI network identified common or cross-talk genes connecting the two networks.

Results

A total of 92 DEGs overlapped between peri-implantitis and T2DM datasets. Three hub genes (IL-6, NFKB1, and PIK3CG) had the highest degree in PPI networks of both peri-implantitis and T2DM. Three leader genes (PSMD10, SOS1, WASF3), eight cross-talk genes (PSMD10, PSMD6, EIF2S1, GSTP1, DNAJC3, SEC61A1, MAPT, and NME1), and one signaling pathway (IL-17 signaling) emerged as peri-implantitis and T2DM linkage mechanisms.

Conclusions

Exploration of available transcriptomic datasets revealed IL-6, NFKB1, and PIK3CG expression along with the IL-17 signaling pathway as top candidate molecular linkage mechanisms between peri-implantitis and T2DM.

Joint-Preserving Procedures in Patients with Varus Deformity: Role of Supramalleolar Osteotomies

The most common cause for end-stage ankle osteoarthritis is posttraumatic, sometimes resulting from concomitant supramalleolar deformity. Aims of the supramalleolar osteotomy include restoring the lower-leg axis to improve intraarticular load distribution and retarding degeneration of the tibiotalar joint. Preoperative planning is based on conventional weight-bearing radiographs. Often advanced imaging, including computed tomography and/or MRI, is needed for a better understanding of the underlying problem. Postoperative complications are not uncommon, including progression of tibiotalar osteoarthritis in up to 25% within 5 years of all patients who have supramalleolar osteotomies.

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.

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.

Effect of compliant layers within piezoelectric composites on power generation providing electrical stimulation in low frequency applications

For patients that use tobacco or have diabetes, bone healing after orthopedic procedures is challenging. Direct current electrical stimulation has shown success clinically to significantly improve bone healing in these difficult-to-fuse populations. Energy harvesting with piezoelectric material has gained popularity in the last decade, but is challenging at low frequencies due to material properties that limit total power generation at these frequencies. Stacked generators have been used to increase power generation at lower voltage levels but have not been widely explored as a load-bearing biomaterial to provide DC stimulation. To match structural compliance levels and increase efficiency of power generation at low frequencies, the effect of compliant layers between piezoelectric discs was investigated. Compliant Layer Adaptive Composite Stacks (CLACS) were manufactured using five PZT discs connected electrically in parallel and stacked mechanically in series with a layer of low modulus epoxy between each disc. The stacks were encapsulated, keeping PZT and overall volume constant. Each stack was electromechanically tested by varying load, frequency, and resistance. As compliant layer thickness increased, power generation increased significantly across all loads, frequencies, and resistances measured. As expected, increase in frequency significantly increased power output for all groups. Similarly, an increase applied peak-to-peak mechanical load also significantly increased power output. The novel use of CLACS for power generation under load and frequencies experienced by typical orthopedic implants could provide an effective method to harvest energy and provide power without the use of a battery in multiple low frequency applications.

Semaphorin 3A promotes osteogenic differentiation of BMSC from type 2 diabetes mellitus rats

Bone regeneration is impaired in patients with type 2 diabetes mellitus (T2DM), which leads to non-healing after bone loss. The decreased osteogenic capacity of bone mesenchymal stem cells (BMSCs) might be a main reason. Sema3A, as a powerful protein promoting osteocyte differentiation, shows potential for bone regeneration treatment. BMSCs may be a therapeutic solution. In this study, we divided BMSCs from T2DM rats (BMSCs-D) and normal rats (BMSCs-N), identified their ability to differentiate into different cell types. Then we found decreased expression of Sema3A in BMSCs-D compared with BMSCs-N. Stimulating with Sema3A showed no influence in the proliferation or migration of BMSCs. However, Sema3A stimulation significantly increased the expression of osteogenic‑related genes, including type I collagen, alkaline phosphatase, Runt-related transcription factor 2 (RUNX2), bone morphogenetic protein and osteocalcin. Besides, the osteogenic capacity of BMSCs was also increased by Sema3A stimulation. In conclusion, we proved that exogenous Sema3A stimulation might repair the osteogenic capacity of BMSCs-D, thus providing a new strategy for restoring the impaired bone regeneration ability for T2DM patients.