Advanced glycation end product 3 (AGE3) suppresses the mineralization of mouse stromal ST2 cells and human mesenchymal stem cells by increasing TGF-β expression and secretion

Systemic Factors Affecting Prognosis and Outcomes in Periodontal Disease

This review delves into the effects of autoimmune conditions like rheumatoid arthritis, inflammatory disorders such as irritable bowel syndrome, cardiovascular disease, diabetes, infectious ailments like human immunodeficiency virus, and their medications on periodontal therapy outcomes. It also explores the influence of hormones. Understanding these systemic factors is crucial for optimizing periodontal health and treatment efficacy. The review underscores the necessity of considering these variables in periodontal care. Other vital systemic factors are addressed elsewhere in this special edition.

Potential Metabolic Pathways Involved in Osteoporosis and Evaluation of Fracture Risk in Individuals with Diabetes

Diabetes has a significant global prevalence. Chronic hyperglycemia affects multiple organs and tissues, including bones. A large number of diabetic patients develop osteoporosis; however, the precise relationship between diabetes and osteoporosis remains incompletely elucidated. The activation of the AGE-RAGE signaling pathway hinders the differentiation of osteoblasts and weakens the process of bone formation due to the presence of advanced glycation end products. High glucose environment can induce ferroptosis of osteoblasts and then develop osteoporosis. Hyperglycemia also suppresses the secretion of sex hormones, and the reduction of testosterone is difficult to effectively maintain bone mineral density. As diabetes therapy, thiazolidinediones control blood glucose by activating PPAR-γ. Activated PPAR-γ can promote osteoclast differentiation and regulate osteoblast function, triggering osteoporosis. The effects of metformin and insulin on bone are currently controversial. Currently, there are no appropriate tools available for assessing the risk of fractures in diabetic patients, despite the fact that the occurrence of osteoporotic fractures is considerably greater in diabetic individuals compared to those without diabetes. Further improving the inclusion criteria of FRAX risk factors and clarifying the early occurrence of osteoporosis sites unique to diabetic patients may be an effective way to diagnose and treat diabetic osteoporosis and reduce the risk of fracture occurrence.

The RAGE signaling in osteoporosis

Osteoporosis (OP), characterized by an imbalance of bone remodeling between formation and resorption, has become a health issue worldwide. The receptor for advanced glycation end product (RAGE), a transmembrane protein in the immunoglobin family, has multiple ligands and has been involved in many chronic diseases, such as diabetes and OP. Increasing evidence shows that activation of the RAGE signaling negatively affects bone remodeling. Ligands, such as advanced glycation end products (AGEs), S100, β-amyloid (Aβ), and high mobility group box 1 (HMGB1), have been well documented that they may negatively regulate the proliferation and differentiation of osteoblasts and positively stimulate osteoclastogenesis by activating the expression of RAGE. In this review, we comprehensively discuss the structure of RAGE and its biological functions in the pathogenesis of OP. The research findings suggest that RAGE signaling has become a potential target for the therapeutic management of OP.

Role of Advanced Glycation End-Products and Oxidative Stress in Type-2-Diabetes-Induced Bone Fragility and Implications on Fracture Risk Stratification

Type 2 diabetes (T2D) and osteoporosis (OP) are major causes of morbidity and mortality that have arelevant health and economic burden. Recent epidemiological evidence suggests that both of these disorders are often associated with each other and that T2D patients have an increased risk of fracture, making bone an additional target of diabetes. As occurs for other diabetic complications, the increased accumulation of advanced glycation end-products (AGEs) and oxidative stress represent the major mechanisms explaining bone fragility in T2D. Both of these conditions directly and indirectly (through the promotion of microvascular complications) impair the structural ductility of bone and negatively affect bone turnover, leading to impaired bone quality, rather than decreased bone density. This makes diabetes-induced bone fragility remarkably different from other forms of OP and represents a major challenge for fracture risk stratification, since either the measurement of BMD or the use of common diagnostic algorithms for OP have a poor predictive value. We review and discuss the role of AGEs and oxidative stress on the pathophysiology of bone fragility in T2D, providing some indications on how to improve fracture risk prediction in T2D patients.

Effects of advanced glycation end products (AGEs) on the differentiation potential of primary stem cells: a systematic review

The formation and accumulation of advanced glycation end products (AGEs) have been associated with aging and the development, or worsening, of many degenerative diseases, such as atherosclerosis, chronic kidney disease, and diabetes. AGEs can accumulate in a variety of cells and tissues, and organs in the body, which in turn induces oxidative stress and inflammatory responses and adversely affects human health. In addition, under abnormal pathological conditions, AGEs create conditions that are not conducive to stem cell differentiation. Moreover, an accumulation of AGEs can affect the differentiation of stem cells. This, in turn, leads to impaired tissue repair and further aggravation of diabetic complications. Therefore, this systematic review clearly outlines the effects of AGEs on cell differentiation of various types of primary isolated stem cells and summarizes the possible regulatory mechanisms and interventions. Our study is expected to reveal the mechanism of tissue damage caused by the diabetic microenvironment from a cellular and molecular point of view and provide new ideas for treating complications caused by diabetes.

Preventing Disused Bone Loss through Inhibition of Advanced Glycation End Products

Bone loss occurs in astronauts during long-term space flight, but the mechanisms are still unclear. We previously showed that advanced glycation end products (AGEs) were involved in microgravity-induced osteoporosis. Here, we investigated the improvement effects of blocking AGEs formation on microgravity-induced bone loss by using the AGEs formation inhibitor, irbesartan. To achieve this objective, we used a tail-suspended (TS) rat model to simulate microgravity and treated the TS rats with 50 mg/kg/day irbesartan, as well as the fluorochrome biomarkers injected into rats to label dynamic bone formation. To assess the accumulation of AGEs, pentosidine (PEN), non-enzymatic cross-links (NE-xLR), and fluorescent AGEs (fAGEs) were identified in the bone; 8-hydroxydeoxyguanosine (8-OHdG) was analyzed for the reactive oxygen species (ROS) level in the bone. Meanwhile, bone mechanical properties, bone microstructure, and dynamic bone histomorphometry were tested for bone quality assessment, and Osterix and TRAP were immunofluorescences stained for the activities of osteoblastic and osteoclastic cells. Results showed AGEs increased significantly and 8-OHdG expression in bone showed an upward trend in TS rat hindlimbs. The bone quality (bone microstructure and mechanical properties) and bone formation process (dynamic bone formation and osteoblastic cells activities) were inhibited after tail-suspension, and showed a correlation with AGEs, suggesting the elevated AGEs contributed to the disused bone loss. After being treated with irbesartan, the increased AGEs and 8-OHdG expression were significantly inhibited, suggesting irbesartan may reduce ROS to inhibit dicarbonyl compounds, thus suppressing AGEs production after tail-suspension. The inhibition of AGEs can partially alter the bone remodeling process and improve bone quality. Both AGEs accumulation and bone alterations almost occurred in trabecular bone but not in cortical bone, suggesting AGEs effects on bone remodeling under microgravity are dependent on the biological milieu.

The trajectory of osteoblast progenitor cells in patients with type 2 diabetes and the predictive model for their osteogenic differentiation ability

The fate of osteoprogenitor cells along with the progression of type 2 diabetes (T2DM) and factors determining the fate of those cells remains to be elucidated. This cross-sectional study included 18 normoglycemic, 27 prediabetic, and 73 T2DM to determine osteogenic differentiation across the continuum of dysglycemia and to construct a model to predict the fate of osteoprogenitor cells. This study demonstrated a preserved osteogenic differentiation ability of peripheral blood-derived mononuclear cells (PBMC) isolated from normoglycemic and prediabetic but a progressive decline in their osteogenic differentiation during the progression of T2DM. The rate of osteogenic differentiation rapidly declined by 4-7% annually during the first 10 years of diabetes and then slowed down. A predictive model composed of three independent risk factors, including age, duration of diabetes, and glomerular filtration rate, demonstrated an AuROC of 0.834. With a proposed cut-off of 21.25, this model had 72.0% sensitivity, 87.5% specificity, and 78.9% accuracy in predicting the fate of osteoprogenitor cells. In conclusion, this study provided a perspective on the osteogenic differentiation ability of the osteoprogenitor cells across a continuum of dysglycemia and a predictive model with good diagnostic performance for the prediction of the fate of osteoprogenitor cells in patients with T2DM.

Crosstalk between bone and other organs

Bone has long been considered as a silent organ that provides a reservoir of calcium and phosphorus, traditionally. Recently, further study of bone has revealed additional functions as an endocrine organ connecting systemic organs of the whole body. Communication between bone and other organs participates in most physiological and pathological events and is responsible for the maintenance of homeostasis. Here, we present an overview of the crosstalk between bone and other organs. Furthermore, we describe the factors mediating the crosstalk and review the mechanisms in the development of potential associated diseases. These connections shed new light on the pathogenesis of systemic diseases and provide novel potential targets for the treatment of systemic diseases.

Chairside Screening for Undiagnosed Diabetes and Prediabetes in Patients with Periodontitis

Introduction

Globally, it is estimated that half of all people with diabetes are undiagnosed. Because of the well-documented bidirectional link between diabetes and periodontitis, dentists and dental hygienists may have the possibility to screen a targeted population for diabetes during routine dental visits. The aim of the present study is to investigate the effectiveness of one device for diagnosis of diabetes/prediabetes used in one private dental practice and investigate the correlation between the levels of HbA1c and periodontal parameters.

Methods

Periodontal patients that were never diagnosed with diabetes were asked to fill a risk assessment questionnaire for type 2 diabetes mellitus. PD, CAL, FMBS%, FMPS%, and HbA1c through a prick-finger test were measured before and after periodontal therapy or only once in patients following supportive periodontal therapy.

Results

A total of 98 subjects were screened, and among them, one had diabetes and 30 had prediabetes. The mean value of HbA1c was 5.62% for patients with untreated periodontitis and 5.42% for periodontally treated patients. The diagnosis of diabetes resulted to be correlated to FMBS% and FMPS%, while HbA1c levels were correlated to FMBS%, FMPS%, and periodontitis grade.

Conclusion

The present chairside diabetes-screening protocol allowed a consistent proportion of patients to become aware of their pathological or prepathological condition and to seek proper and timely medical care. Thus, dentists and dental hygienists could provide health promotion services and preventive measures.

Oxidized high mobility group B-1 enhances metastability of colorectal cancer via modification of mesenchymal stem/stromal cells

High mobility group box-1 (HMGB1) is known to be a chemotactic factor for mesenchymal stem/stromal cells (MSCs), but the effect of post-translational modification on its function is not clear. In this study, we hypothesized that differences in the oxidation state of HMGB1 would lead to differences in the function of MSCs in cancer. In human colorectal cancer, MSCs infiltrating into the stroma were correlated with liver metastasis and serum HMGB1. In animal models, oxidized HMGB1 mobilized 3-fold fewer MSCs to subcutaneous tumors compared to reduced HMGB1. Reduced HMGB1 inhibited proliferation of mouse bone marrow MSCs (BM-MSCs) and induced differentiation into osteoblasts and vascular pericytes, whereas oxidized HMGB1 promoted proliferation and increased stemness, and no differentiation was observed. When BM-MSCs pretreated with oxidized HMGB1 were co-cultured with syngeneic cancer cells, cell proliferation and stemness of cancer cells were increased, and tumorigenesis and drug resistance were promoted. In contrast, co-culture with reduced HMGB1-pretreated BM-MSCs did not enhance stemness. In an animal orthotopic transplantation colorectal cancer model, oxidized HMGB1, but not reduced HMGB1, promoted liver metastasis with intratumoral MSC chemotaxis. Thus, oxidized HMGB1 reprograms MSCs and promotes cancer malignancy. The oxidized HMGB1-MSC axis may be an important target for cancer therapy.

Increased BMSC exosomal miR-140-3p alleviates bone degradation and promotes bone restoration by targeting Plxnb1 in diabetic rats

Background

Diabetes mellitus (DM) is considered to be an important factor for bone degeneration disorders such as bone defect nonunion, which is characterized by physical disability and tremendous economy cost to families and society. Exosomal miRNAs of BMSCs have been reported to participate in osteoblastogenesis and modulating bone formation. However, their impacts on the development of bone degeneration in DM are not yet known. The role of miRNAs in BMSCs exosomes on regulating hyperglycemia bone degeneration was investigated in the present study.

Results

The osteogenic potential in bone defect repair of exosomes derived from diabetes mellitus BMSCs derived exosomes (DM-Exos) were revealed to be lower than that in normal BMSCs derived exosomes (N-Exos) in vitro and in vivo. Here, we demonstrate that miR-140-3p level was significantly altered in exosomes derived from BMSCs, ADSCs and serum from DM rats. In in vitro experiments, upregulated miR-140-3p exosomes promoted DM BMSCs differentiation into osteoblasts. The effects were exerted by miR-140-3p targeting plxnb1, plexin B1 is the receptor of semaphoring 4D(Sema4D) that inhibited osteocytes differentiation, thereby promoting bone formation. In DM rats with bone defect, miR-140-3p upregulated exosomes were transplanted into injured bone and accelerated bone regeneration. Besides, miR-140-3p in the exosomes was transferred into BMSCs and osteoblasts and promoted bone regeneration by targeting the plexin B1/RohA/ROCK signaling pathway.

Conclusions

Normal-Exos and miR-140-3p overexpressed-Exos accelerated diabetic wound healing by promoting the osteoblastogenesis function of BMSCs through inhibition plexin B1 expression which is the receptor of Sema4D and the plexin B1/RhoA/ROCK pathway compared with diabetes mellitus-Exos. This offers a new insight and a new therapy for treating diabetic bone unhealing.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01267-2.

The Association between Accumulation of Toxic Advanced Glycation End-Products and Cytotoxic Effect in MC3T3-E1 Cells

In diabetic patients, the metabolism of excess glucose increases the toxicity of the aldehyde group of sugar. Aldehydes, including glyceraldehyde (GA), react with intracellular proteins to form advanced glycation end-products (AGEs), which deteriorate bone quality and cause osteoporosis. One of the causes of osteoporotic fractures is impaired osteoblast osteogenesis; however, the cytotoxic effects of aldehydes and the subsequent formation of AGEs in osteoblasts have not yet been examined in detail. Therefore, the present study investigated the cytotoxicity of intracellular GA and GA-derived AGEs, named toxic AGEs (TAGE), in the mouse osteoblastic cell line MC3T3-E1. Treatment with GA induced MC3T3-E1 cell death, which was accompanied by TAGE modifications in several intracellular proteins. Furthermore, the downregulated expression of Runx2, a transcription factor essential for osteoblast differentiation, and collagen correlated with the accumulation of TAGE. The GA treatment also reduced the normal protein levels of collagen in cells, suggesting that collagen may be modified by TAGE and form an abnormal structure. Collectively, the present results show for the first time that GA and TAGE exert cytotoxic effects in osteoblasts, inhibit osteoblastic differentiation, and decrease the amount of normal collagen. The suppression of GA production and associated accumulation of TAGE has potential as a novel therapeutic target for osteoporosis under hyperglycemic conditions.

Advanced glycation end products promote osteoporosis by inducing ferroptosis in osteoblasts

Advanced glycation end products (AGEs) have been widely reported to play an important role in osteoporosis (OP), particularly in diabetes-related OP. The aim of the present study was to investigate the effect of AGEs on osteoblast function and the underlying mechanisms. The level of bone mineral density (BMD), serum AGEs and fasting blood glucose (FBG) was measured in patients with OP and healthy individuals, and the correlation between AGE levels and BMD or FBG was then analyzed. For the in vitro experiments, the hFOB1.19 osteoblast cell line was cultured in medium containing AGEs and serum from healthy individuals or patients with OP, and with or without type-2 diabetes mellitus (T2DM). Cell proliferation, differentiation, mineralization, apoptosis and ferroptosis were evaluated using Cell Counting Kit-8 and alkaline phosphatase (ALP) assays, Alizarin red and TUNEL staining, iron indicator, lipid peroxidation tests and western blot analysis, respectively. In a separate set of experiments, the ferroptosis inhibitor, deferoxamine (DFO), was also added to the culture medium of cells treated with AGEs and serum from patients with OP and T2DM. The results demonstrated that patients with OP had a higher level of serum AGEs and FBG compared with that in healthy individuals. The level of serum AGEs in patients with OP was negatively correlated with BMD, but was positively correlated with FBG. In addition, AGEs and serum from patients with OP markedly inhibited hFOB1.19 cell proliferation, ALP production and mineralized nodule formation. Apoptosis and ferroptosis were significantly promoted by AGEs and serum from patients with OP. Moreover, serum from OP patients with T2DM caused stronger effect than that from OP patients with normal FBG. However, DFO reversed the effects induced by AGEs and serum from patients with OP and T2DM on hFOB1.19 cells. Collectively, AGEs could disrupt the functions of osteoblasts by inducing cell ferroptosis, thus contributing to OP.

Advanced glycation end productions and tendon stem/progenitor cells in pathogenesis of diabetic tendinopathy

Tendinopathy is a challenging complication observed in patients with diabetes mellitus. Tendinopathy usually leads to chronic pain, limited joint motion, and even ruptured tendons. Imaging and histological analyses have revealed pathological changes in various tendons of patients with diabetes, including disorganized arrangement of collagen fibers, microtears, calcium nodules, and advanced glycation end product (AGE) deposition. Tendon-derived stem/ progenitor cells (TSPCs) were found to maintain hemostasis and to participate in the reversal of tendinopathy. We also discovered the aberrant osteochondrogenesis of TSPCs in vitro. However, the relationship between AGEs and TSPCs in diabetic tendinopathy and the underlying mechanism remain unclear. In this review, we summarize the current findings in this field and hypothesize that AGEs could alter the properties of tendons in patients with diabetes by regulating the proliferation and differentiation of TSPCs in vivo.

LncRNA ORLNC1 Promotes Bone Marrow Mesenchyml Stem Cell Pyroptosis Induced by Advanced Glycation End Production by Targeting miR-200b-3p/Foxo3 Pathway

Bone marrow mesenchymal stem cells (BMSCs) are a type of adult stem cells that originate from the mesoderm and have important roles in the body because of their self-renewal and multidirectional differentiation potential. Now it has been proved that BMSCs are closely related to the development of osteoporosis (OP). There is growing evidence that lncRNAs are involved in regulating the pyroptosis of BMSCs. And advanced glycation end-products (AGEs) have been recognized as NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome activators. In this study, we aimed to explore the role of lncRNA ORLNC1 (NONMMUT016106.2) on the pyroptosis of BMSCs under CML (Nε-(carboxymethyl) lysine, the most common AGEs) treatment and its specific molecular mechanisms. Our study revealed that CML treatment promoted pyroptosis of BMSCs and upregulated ORLNC1 expression. As a competing endogenous RNA (ceRNA) of miR-200b-3p, the level of ORLNC1 was negatively correlated with miR-200b-3p. Foxo3 was a target of miR-200b-3p and ORLNC1 promoted BMSCs pyroptosis induced by CML through targeting miR-200b-3p/Foxo3 pathway.

Platelet-Rich Plasma Suppresses Inflammation Reaction of Rat Articular Chondrocytes via Wingless-Related Integration Site/β-Catenin Axis

Our study aims to elucidate the role of platelet-rich plasma (PRP) in rats chondrocytes inflammation and mechanism. PRP was obtained from 8 weeks old rats. Then, the knee joint of bilateral hind limbs was dissected and articular chondrocytes were obtained in super-clean table after dislocation and identified at the second generation during culture and passage. Chondrocytes were divided into control group 1 (addition of saline), control group 2 (IWP-2, Wnt/β-catenin axis inhibitor) and experimental group (PRP) followed by analysis of mRNA levels of glycogen synthase kinase-3 (GSK-3β), low-density lipoprotein receptor-associated protein 5 (LRP5), Wnt1 and β-catenin by RT-PCR, IL-1 and TNF-α after 1 week by ELISA. The second generation articular chondrocytes presented polygonal or triangular cell morphology, positive for collagen II and toluidine blue staining. PRP addition significantly reduced GSK-3β and LRP5 mRNA level, and increased β-catenin and Wnt1 mRNA levels in chondrocytes. Meanwhile, it suppressed IL-1 and TNF-α secretion and Wnt protein production inhibitor 2. PRP might suppresses inflammatory factors production of rat articular chondrocytes through inhibiting Wnt/β-catenin axis.

High glucose promotes mineralization via bone morphogenetic protein 4-Smad signals in early stage of osteoblast differentiation

Diabetes mellitus is associated with bone fragility. Although osteoblast maturation is disturbed in patients with diabetes mellitus, the involvement of high glucose (HG) in different stages of osteoblast maturation is unclear. We used MC3T3-E1 cells, a murine osteoblastic cell line. The cells were incubated in high glucose medium (16.5 and 27.5 mM) with three different time courses: throughout 21 days, only first 7 days (early stage) and only last 7 days (late stage). Mineralization assay showed that HG throughout 21 days increased mineralization compared with control (5.5 mM). In the time course experiment, HG increased mRNA expression of Alp, osteocalcin (Ocn), runt-related transcription factor 2 and osterix on days 3 and 5. By contrast, long-term treatment with HG (14 and 21 days) decreased expression of these osteoblastic markers. HG only during early stage enhanced mineralization, while HG only during late stage had no effects. HG increased the expression of bone morphogenetic protein (BMP) 4 and enhanced phosphorylation of Smad1/5/8. Treatment with a BMP receptor antagonist LDN193189 prevented the HG-induced mineralization during early stage of osteoblast differentiation, indicating that HG in the early stage promotes mineralization by BMP4. In conclusion, the study demonstrates that continuous HG treatment might enhance early osteoblast differentiation but disturbs osteoblast maturation, and that BMP-4-Smad signal might be involved in the HG-induced differentiation and mineralization of osteoblasts.

Age-Influenced Receptors of Advanced Glycation End Product Overexpression Associated With Osteogenic Differentiation Impairment in Patients With Type 2 Diabetes

Preclinical studies have found impaired osteogenic differentiation to be associated with type 2 diabetes (T2DM), which is related to skeletal accumulation of advanced glycation end products (AGEs). Our previous study also showed impaired osteogenic differentiation in peripheral blood-derived mononuclear cells (PBMC) isolated from patients with long-standing T2DM, which is conceivably due to the overexpression of receptor of advance glycation end products (RAGE) and the enhancement of cellular apoptosis. However, the existence of RAGE overexpression in earlier stages of diabetes remains unclear, as do the factors influencing that RAGE overexpression. This cross-sectional study enrolled 40 patients with T2DM treated with metformin monotherapy and 30 age-matched non-diabetic controls (NDM) to investigate the overexpression of RAGE in PBMC derived from patients with earlier stage diabetes, as well as to explore its determining factors. Almost all (90%) PBMC-isolated from NDM (NDM-pD) expressed osteoblast-specific genes including ALPL, BGLAP, COL1A1, and RUNX2/PPAR while only 40% of PBMC-derived from diabetic patients (DM-pD) expressed those genes. By using age- and pentosidine-matched NDM-pD as a reference, AGER and BAX/BCL2 expression in PBMC isolated from diabetic patients showing impaired osteoblast-specific gene expression (DM-iD) were 6.6 and 5 folds higher than the reference while AGER and BAX/BCL2 expression in DM-pD were comparable to the reference. AGER expression showed a significant positive correlation with age (r=0.470, p=0.003). The multivariate analysis demonstrated that both age and AGER expression correlated with the potential for osteogenic differentiation in the PBMC isolated from patients with diabetes. In conclusion, this study showed osteogenic differentiation impairment in approximately half of PBMC derived from type 2 diabetic patients receiving metformin monotherapy. Both AGER and BAX/BCL2 overexpression were demonstrated only in PBMC-isolated from diabetic patients with poor osteogenic differentiation. Therefore, this study not only illustrated the existence of RAGE overexpression in PBMC derived from patients with early stages of T2DM but also strengthened the linkage between that RAGE overexpression and the retardation of osteogenic differentiation. Age was also shown to be a positive influencing factor for RAGE overexpression. Furthermore, both age and RAGE overexpression were demonstrated as independent risk factors for determining osteogenic differentiation potential of the PBMC-isolated from T2DM.

Correlation of Osteoporosis in Patients With Newly Diagnosed Type 2 Diabetes: A Retrospective Study in Chinese Population

This study aimed to explore the risk factors attributed to osteoporosis in newly type 2 diabetes mellitus (T2DM) patients. This study aimed to recruit 244 T2DM patients and 218 non-diabetic controls. We collected demographic characteristics, medical history, bone mineral density and biomarkers including bone specific alkaline phosphatase (BALP), osteocalcin, N-terminal peptide of type I procollagen (P1NP), tartrate-resistant acid phosphatase 5b (TRCAP-5b), β-Cross Laps of type I collagen-containing cross-linked C-telopeptide (β-CTX), 25-hydroxyvitamin D, parathyroid hormone were recorded or detected. Bone mineral density (BMD) was our primary outcome. Based on the result of BMD, we divided both the control group and T2DM group into three subgroups: normal bone mass, osteopenia and osteoporosis. In control group, we found age, sex, menopausal status, BMI, P1NP, BALP, TRACP-5b, osteocalcin, and corrected serum calcium are differential among three subgroups. In T2DM group, we found age, sex, menopausal status, drinking status, BMI, HbA1c, TRACP-5b and OC were differential among three subgroups. In T2DM and control groups, age, female, postmenopausal status, BALP, TRACP-5b and osteocalcin were positively correlated while BMI was negatively correlated with osteoporosis. In control group, β-CTX was positively correlated with osteoporosis. In T2DM group, HbA1c and corrected serum calcium concentration were positively correlated with osteoporosis. After further adjustment of age, BMI in male, TRACP-5b was positively correlated with the risk of osteoporosis in newly diagnosed T2DM. After adjusted of age, BMI and menopausal status in female, OC was positively correlated with the risk of osteoporosis in newly diagnosed T2DM and controls. In female T2DM, BALP and P1NP were positively correlated with the risk of osteoporosis. In conclusion, age, BMI and menopausal status are common risk factors for osteoporosis in diabetic and non-diabetic patients, however TRACP-5b, BALP and osteocalcin are special risk factors for osteoporosis in newly diagnosed T2DM patients but not non-diabetic patients, which may be applied to identify osteoporosis risk in T2DM patients, but this result needs to be proven with fracture data.

Executive summary of clinical practice guide on fracture risk in lifestyle diseases

Accumulating evidence has shown that patients with lifestyle diseases such as type 2 diabetes mellitus, chronic kidney disease, and chronic obstructive pulmonary disease are at increased risk of osteoporotic fracture. Fractures deteriorate quality of life, activities of daily living, and mortality as well as a lifestyle disease. Therefore, preventing fracture is an important issue for those patients. Although the mechanism of the lifestyle diseases-induced bone fragility is still unclear, not only bone mineral density (BMD) reduction but also bone quality deterioration are involved in it. Because fracture predictive ability of BMD and FRAX^® is limited, especially for patients with lifestyle diseases, the optimal management strategy should be established. Thus, when the intervention of the lifestyle diseases-induced bone fragility is initiated, the deterioration of bone quality should be taken into account. We here review the association between lifestyle diseases and fracture risk and proposed an algorism of starting anti-osteoporosis drugs for patients with lifestyle diseases.

Advanced glycation end products in musculoskeletal system and disorders

The human population is ageing globally, and the number of old people is increasing yearly. Diabetes is common in the elderly, and the number of diabetic patients is also increasing. Elderly and diabetic patients often have musculoskeletal disorder, which are associated with advanced glycation end products (AGEs). AGEs are heterogeneous molecules derived from non-enzymatic products of the reaction of glucose or other sugar derivatives with proteins or lipids, and many different types of AGEs have been identified. AGEs are a biomarker for ageing and for evaluating disease conditions. Fluorescence, spectroscopy, mass spectrometry, chromatography, and immunological methods are commonly used to measure AGEs, but there is no standardized evaluation method because of the heterogeneity of AGEs. The formation of AGEs is irreversible, and they accumulate in tissue, eventually causing damage. AGE accumulation has been confirmed in neuromusculoskeletal tissues, including bones, cartilage, muscles, tendons, ligaments, and nerves, where they adversely affect biomechanical properties by causing charge changes and forming cross-linkages. AGEs also bind to receptors, such as the receptor for AGEs (RAGE), and induce inflammation by intracellular signal transduction. These mechanisms cause many varied aging and diabetes-related pathological conditions, such as osteoporosis, osteoarthritis, sarcopenia, tendinopathy, and neuropathy. Understanding of AGEs related pathomechanism may lead to develop novel methods for the prevention and therapy of such disorders which affect patients' quality of life. Herein, we critically review the current methodology used for detecting AGEs, and present potential mechanisms by which AGEs cause or exacerbate musculoskeletal disorders.

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.

Morroniside attenuates high glucose-induced BMSC dysfunction by regulating the Glo1/AGE/RAGE axis

Objectives

High glucose (HG)–mediated bone marrow mesenchymal stem cell (BMSC) dysfunction plays a key role in impaired bone formation induced by type 1 diabetes mellitus (T1DM). Morroniside is an iridoid glycoside derived from the Chinese herb Cornus officinalis, and it has abundant biological activities associated with cell metabolism and tissue regeneration. However, the effects and underlying mechanisms of morroniside on HG‐induced BMSC dysfunction remain poorly understood.

Materials and methods

Alkaline phosphatase (ALP) staining, ALP activity and Alizarin Red staining were performed to assess the osteogenesis of BMSCs. Quantitative real‐time PCR and Western blot (WB) were used to investigate the osteo‐specific markers, receptor for advanced glycation end product (RAGE) signalling and glyoxalase‐1 (Glo1). Additionally, a T1DM rat model was used to assess the protective effect of morroniside in vivo.

Results

Morroniside treatment reverses the HG‐impaired osteogenic differentiation of BMSCs in vitro. Morroniside suppressed advanced glycation end product (AGEs) formation and RAGE expression by triggering Glo1. Moreover, the enhanced osteogenesis due to morroniside treatment was partially blocked by the Glo1 inhibitor, BBGCP2. Furthermore, in vivo, morroniside attenuated bone loss and improved bone microarchitecture accompanied by Glo1 upregulation and RAGE downregulation.

Conclusions

These findings suggest that morroniside attenuates HG‐mediated BMSC dysfunction partly through the inhibition of AGE‐RAGE signalling and activation of Glo1 and may be a potential treatment for diabetic osteoporosis.

Effects of high glucose conditions on the expansion and differentiation capabilities of mesenchymal stromal cells derived from rat endosteal niche

Background

Mesenchymal stromal cells in the endosteal niche lining compact bone (CB-MSCs) represent a heterogeneous population, all of which contribute to bone repair and remodelling. Hyperglycaemia associated with type 2 diabetes mellitus (T2DM) can delay and impair the bone healing process. Therefore, this study investigated the influences of high (25 mM) glucose conditions on CB-MSC populations isolated from male Wistar rats, versus normal (5.5 mM) glucose conditions; in terms of proliferation (population doublings, PDs), senescence characteristics, stem cell marker expression, colony forming efficiencies (CFEs); and osteogenic/adipogenic differentiation, following extended culture in vitro.

Results

CB-MSCs under both normoglycaemic and hyperglycaemic conditions demonstrated similar morphologies and rapid exponential growth to >300PDs, although high glucose conditions promoted more rapid and persistent proliferation beyond ~50PDs, with few indications of senescence. Limited senescence was confirmed by minimal SA-β-galactosidase staining, low senescence marker (p53, p21^waf1, p16^INK4a) expression and positive telomere maintenance marker (rTERT, TR) expression. However, telomere lengths varied throughout culture expansion, with hyperglycaemia significantly reducing telomere lengths at PD50 and PD200. Furthermore, CB-MSCs expanded in normal and high glucose conditions remained non-transformed, exhibiting similar MSC (CD73/CD90/CD105), multipotency (CD146) and embryonic (Slug, Snail) markers throughout extended culture, but negligible hematopoietic (CD34/CD45) or pluripotency (Nanog, Oct4) markers. Hyperglycaemia significantly increased CFEs at PD50 and PD100, which decreased at PD200. CB-MSC osteogenic differentiation was also inhibited by hyperglycaemia at PD15, PD100 and PD200, but not at PD50. Hyperglycaemia inhibited CB-MSC adipogenic differentiation to a lesser extent at PD15 and PD50, with reduced adipogenesis overall at PD100 and PD200.

Conclusion

This study demonstrates the limited negative impact of hyperglycaemia on the proliferative and stem cell characteristics of heterogeneous CB-MSC populations, although minor sub-population(s) appear more susceptible to these conditions leading to impaired osteogenic/adipogenic differentiation capabilities. Such findings potentially highlight the impact of hyperglycaemia on CB-MSC bone repair capabilities in situ.

Glycolaldehyde-modified advanced glycation end-products inhibit differentiation of human monocytes into osteoclasts via upregulation of IL-10

Diabetes patients are at high risk of bone fracture due to accumulation of advanced glycation end products (AGEs) and low bone turnover. Although AGEs inhibit osteoblast functions, little is known about their roles in regulation of human osteoclast differentiation. The aim of this study was to determine the roles of AGEs in regulation of human osteoclast differentiation. Human CD14⁺ monocytes collected from healthy individuals were stimulated in vitro with conventional cytokines to induce osteoclast differentiation. Simultaneously, glucose-modified AGEs-BSA (Glu-AGEs-BSA) and glycolaldehyde-modified AGEs-BSA (Glyco-AGEs-BSA) were added to analyze their role in regulation of osteoclast differentiation. Human CD14⁺ cells expressed endogenous receptor for AGE (RAGE). Stimulation with Glyco-AGEs-BSA, but not Glu-AGEs-BSA, reduced the number of tartrate-resistant acid phosphatase-positive cells in a dose-dependent manner and suppressed mRNA expression of nuclear factor of activated T-cells 1 and cathepsin K. Glyco-AGEs-BSA up-regulated pro-inflammatory cytokines and anti-inflammatory cytokine IL-10. The addition of IL-10-neutralizing antibodies abrogated the suppressive effect of Glyco-AGEs-BSA on osteoclast differentiation. Stimulation of Glyco-AGE-BSA resulted in nuclear factor (NF)-κB phosphorylation, and addition of an inhibitor of κB kinase suppressed IL-10 production. We conclude that Glyco-AGEs-BSA inhibited human osteoclast differentiation through induction of IL-10 expression via NF-κB. It can be assumed that AGE bioaccumulation in diabetic patients increases the risk of bone fracture, through inhibition of osteoclast differentiation, reduction of bone turnover, and disruption of bone remodeling.

Advanced Glycation End Products (AGEs), Receptor for AGEs, Diabetes, and Bone: Review of the Literature

Diabetes compromises bone cell metabolism and function, resulting in increased risk of fragility fracture. Advanced glycation end products (AGEs) interact with the receptor for AGEs (RAGE) and can make a meaningful contribution to bone cell metabolism and/or alter function. Searches in PubMed using the key words "advanced glycation end-product," "RAGE," "sRAGE," "bone," and "diabetes" were made to explain some of the clinical outcomes of diabetes in bone metabolism through the AGE-RAGE signaling pathway. All published clinical studies were included in tables. The AGE-RAGE signaling pathway participates in diabetic complications, including diabetic osteopathy. Some clinical results in diabetic patients, such as reduced bone density, suppressed bone turnover markers, and bone quality impairment, could be potentially due to AGE-RAGE signaling consequences. However, the AGE-RAGE signaling pathway has some helpful roles in the bone, including an increase in osteogenic function. Soluble RAGE (sRAGE), as a ligand decoy, may increase in either conditions of RAGE production or destruction, and then it cannot always reflect the AGE-RAGE signaling. Recombinant sRAGE can block the AGE-RAGE signaling pathway but is associated with some limitations, such as accessibility to AGEs, an increase in other RAGE ligands, and a long half-life (24 hours), which is associated with losing the beneficial effect of AGE/RAGE. As a result, sRAGE is not a helpful marker to assess activity of the RAGE signaling pathway. The recombinant sRAGE cannot be translated into clinical practice due to its limitations.

Impaired Bone Regenerative Effect of Exosomes Derived from Bone Marrow Mesenchymal Stem Cells in Type 1 Diabetes

Stem cell‐derived exosomes have exhibited promise for applications in tissue regeneration. However, one major problem for stem cell‐derived exosome therapies is identifying appropriate source cells. In the present study, we aimed to compare the bone regenerative effect of exosomes secreted by bone marrow mesenchymal stem cells (BMSCs) derived from type 1 diabetes rats (dBMSC‐exos) and exosomes secreted by BMSCs derived from normal rats (nBMSC‐exos). BMSCs were isolated from rats with streptozotocin‐induced diabetes and normal rats. dBMSC‐exos and nBMSC‐exos were isolated by an ultracentrifugation method and identified. The effects of dBMSC‐exos and nBMSC‐exos on the proliferation and migration of BMSCs and human umbilical vein endothelial cells (HUVECs) were investigated. The effects of exosomes on the osteogenic differentiation of BMSCs and the angiogenic activity of HUVECs were compared. Finally, a rat calvarial defect model was used to compare the effects of exosomes on bone regeneration and neovascularization in vivo. In vitro, dBMSC‐exos and nBMSC‐exos both enhanced the osteogenic differentiation of BMSCs and promoted the angiogenic activity of HUVECs, but nBMSC‐exos had a greater effect than dBMSC‐exos. Similarly, in vivo, both dBMSC‐exos and nBMSC‐exos promoted bone regeneration and neovascularization in rat calvarial defects, but the therapeutic effect of nBMSC‐exos was superior to that of dBMSC‐exos. The present study demonstrates for the first time that the bone regenerative effect of exosomes derived from BMSCs is impaired in type 1 diabetes, indicating that for patients with type 1 diabetes, the autologous transplantation of BMSC‐exos to promote bone regeneration may be inappropriate. stem cells translational medicine2019;8:593–605

Effect of type 2 diabetes mellitus on treatment outcomes of patients with postmenopausal osteoporosis: a retrospective study

Objectives

The aim of this study is to investigate the effect of type 2 diabetes mellitus (T2DM) on the treatment outcomes of patients with postmenopausal osteoporosis (PMOP).

Material and method

Thirty-five patients who had been diagnosed as PMOP by lumbar and/or femoral neck bone mineral density screening (BMD) and who had comorbid T2DM were included in the study. Thirty-five patients who had been diagnosed as PMOP but who had no comorbidity including DM constituted the control group. Demographic features, biochemical parameters, femoral and lumbar T scores were all recorded. All patients were treated with bisphosphonate, calcium and vitamin D and the same parameters were evaluated at the end of the first and fifth year.

Results

Lumbar T scores and serum osteocalcin levels before treatment were significantly lower in the DM + PMOP group (p < 0,05). At the end of 5 years, despite the lumbar T score having increased, the femoral T score was found to be significantly lower in the DM + PMOP group. In the PMOP group, there was significant improvement in the T scores and serum osteocalcin levels following a 5-year treatment period (p < 0,05).

Conclusions

T2DM has unfavorable effects on treatment prognosis in patients with PMOP. Different risk factors of PMOP which differ in the general population maybe more important when evaluating fracture risk in patients wtih T2DM.

Diabetes Mellitus-induced Bone Fragility

Accumulating evidence has shown that the risk of osteoporotic fractures is increased in patients with diabetes mellitus (DM). Thus, DM-induced bone fragility has been recently recognized as a diabetic complication. Because the fracture risk is independent of the reduction in bone mineral density, deterioration of the bone quality may be the main cause of bone fragility. Although its mechanism remains poorly understood, accumulated collagen cross-links of advanced glycation end-products (AGEs) and dysfunctions of osteoblast and osteocyte may be involved. Previous studies have suggested that various diabetes-related factors, such as chronic hyperglycemia, insulin, insulin-like growth factor-I, AGEs, and homocysteine, are associated with the risk of bone fragility caused by impaired bone formation and bone remodeling. Furthermore, several anti-diabetic drugs are known to affect bone metabolism and fracture risk. We herein review the association between DM and fracture risk as well as the mechanism of DM-induced bone fragility based on recent evidence.

1α,25-dihydroxyvitamin D3 promotes osseointegration of titanium implant via downregulating AGEs/RAGE pathway in T2DM

Diabetes-induced advanced glycation end products (AGEs) overproduction would result in compromised osseointegration of titanium implant and high rate of implantation failure. 1α,25-dihydroxyvitamin D3 (1,25VD3) plays a vital role in osteogenesis, whereas its effects on the osseointegration and the underlying mechanism are unclear. The purpose of this study was to investigate that 1,25VD3 might promote the defensive ability of osseointegration through suppressing AGEs/RAGE in type 2 diabetes mellitus. In animal study, streptozotocin-induced diabetic rats accepted implant surgery, with or without 1,25VD3 intervention for 12 weeks. After sacrificed, the serum AGEs level, bone microarchitecture and biomechanical index of rats were measured systematically. In vitro study, osteoblasts differentiation capacity was analyzed by alizarin red staining, alkaline phosphatase assay and western blotting, after treated with BSA, AGEs, AGEs with RAGE inhibitor and AGEs with 1,25VD3. And the expression of RAGE protein was detected to explore the mechanism. Results showed that 1,25VD3 could reverse the impaired osseointegration and mechanical strength, which possibly resulted from the increased AGEs. Moreover, 1,25VD3 could ameliorate AGEs-induced damage of cell osteogenic differentiation, as well as downregulating the RAGE expression. These data may provide a theoretical basis that 1,25VD3 could work as an adjuvant treatment to against poor osseointegration in patients with type 2 diabetes mellitus.

Higher dialysate calcium concentration is associated with incident myocardial infarction among diabetic patients with low bone turnover: a longitudinal study

This is a longitudinal study on 53,560 hemodialysis patients from the Japan Renal Data Registry. Predictor was D[Ca] ≥3.0 vs 2.5 mEq/L. Outcomes were the first CV events during 1-year observation period. Association of D[Ca] with CV events and effect modifications were tested using multivariate logistic regression analyses. Diabetes mellitus (DM) was a significant effect modifier for association of higher D[Ca] and myocardial infarction (MI) (OR: 1.26 (1.03-1.55) among DM and 0.86 (0.72-1.03) among non-DM, p for interaction <0.01). The effect size was not affected by further adjustment for serum albumin-corrected Ca or intact parathyroid hormone (iPTH) levels, but was attenuated by adjustment for intradialytic change in serum Ca concentration (ΔCa) (1.16 [0.89-1.51]). Among DM, D[Ca] ≥3.0 mEq/L was significantly associated with MI in the first tertile of corrected Ca or iPTH ≤60 pg/ml (p for interaction 0.03 and 0.03, respectively). In conclusion, higher D[Ca] was associated with incident MI in DM, especially with low serum Ca or iPTH levels. Attenuation of the effect size by adjustment for ΔCa and stratified analyses suggest that larger Ca influx during dialysis with higher D[Ca] in patients suggestive of low bone turnover leads to vascular calcification and subsequent MI in DM.

Underlying Mechanisms Between Diabetes Mellitus and Osteoporosis

Several studies have linked diabetes mellitus with an increased risk of bone fractures. Patients with type 1 diabetes have lower bone mineral density and patients with type 2 diabetes have an increased risk of fracture despite normal or high bone mineral density, measured by dual energy x-ray absorptiometry. Different mechanisms have been proposed in the pathophysiology of bone disease in diabetic patients. The mechanisms involved include microvasculature changes, advanced glycation end products accumulation, and altered osteoblast–osteoclast function with increased sclerostin, decreased insulin-like growth factor 1 (IGF1), decreased osteocalcin, and other molecular alterations, leading to a decrease in bone turnover and altered bone quality. Other factors, such as increased risk of falls related to diabetic neuropathy and diabetic retinopathy have also been proposed. Different diagnostic methods have been described for the study of bone disease in patients with diabetes, due to the lack of correlation between bone mineral density measured by dual x-ray absorptiometry and the fracture risk in this group of patients. These methods include the evaluation of bone turnover markers, the FRAX score, the trabecular bone score, and the evaluation of microarchitecture with high-resolution peripheral quantitative tomography. This editorial provides a short overview of the underlying mechanisms between diabetes mellitus and osteoporosis, and the diagnostic methods used to evaluate these patients.

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.

Interaction between bone and glucose metabolism [Review]

Accumulating evidence has shown that bone and glucose metabolism are closely associated with each other. Since the risk of osteoporotic fractures is increased in patients with diabetes mellitus (DM), osteoporosis is recently recognized as one of diabetic complications, called DM-induced bone fragility. Previous studies showed that collagen cross-links of advanced glycation end products (AGEs) and dysfunctions of osteoblast and osteocyte are involved in DM-induced bone fragility. Circulating levels of AGEs and homocysteine are increased in patients with DM, and they directly impair the functions of osteoblast and osteocyte, resulting in decreased bone formation and bone remodeling. On the other hand, bone is recently recognized as an endocrine organ. Previous studies based on in vitro and animal studies showed that osteocalcin, which is specifically expressed in osteoblasts and secreted into the circulation, may regulate glucose homeostasis. Although several clinical studies reported the relationship between osteocalcin and glucose metabolism, further large-scale and intervention studies are necessary to confirm the beneficial effects of osteocalcin on glucose metabolism in human. It has been shown that adenosine monophosphate-activated protein kinase (AMPK), an intracellular energy sensor, is involved in bone metabolism. Adiponectin and metformin stimulate osteocalcin expression and the differentiation of osteoblasts via AMPK activation. Also, AMPK activation protects against oxidative stress-induced apoptosis of osteocytes. These findings suggest that AMPK in osteoblasts and osteocytes may be a therapeutic target for DM-induced bone fragility.

Impaired osteogenic differentiation and enhanced cellular receptor of advanced glycation end products sensitivity in patients with type 2 diabetes

Preclinical studies have demonstrated impaired osteoblast differentiation in type 2 diabetes (T2DM), which is related to skeletal accumulation of advanced glycation end products (AGEs). However, the role of AGE in osteoblast differentiation in patients with T2DM is unclear. This cross-sectional study was performed to investigate osteoblast differentiation and its association with serum pentosidine and soluble receptor of AGEs (sRAGE). Twenty-seven patients with T2DM and 15 age-matched controls were included to measure sRAGE and osteogenic differentiation in mononuclear cells derived from peripheral blood. The mononuclear cells isolated from patients with T2DM showed a significantly lower rate of osteogenic differentiation (7.4% vs 86.7%, p < 0.0001) with a lower level of ALPL, COL1A1, and BGLAP expression than those of controls by 11-, 44-, and 15-fold respectively, together with nonvisualized mineralization by alizarin red S staining. The levels of pentosidine and sRAGE were comparable in both groups. AGER expression was significantly higher in the T2DM group. BAX expression was also significantly higher in the T2DM group, and showed a strong correlation with AGER expression (r = 0.86, p < 0.0001). Fasting plasma glucose (FPG) level, AGER expression, and BAX expression showed a strong correlation with osteogenic differentiation defects on univariate analysis. However, only FPG showed a correlation with this defect in a multivariate analysis. In conclusion, patients with T2DM showed impairment of osteoblast differentiation, and FPG was an independent risk factor for this impairment. Moreover, T2DM showed a higher cellular sensitivity for activation of receptor of AGEs and higher cellular apoptosis, which may contribute to the defect in osteoblast differentiation.

Evaluation of circulating sRAGE in osteoporosis according to BMI, adipokines and fracture risk: a pilot observational study

Background

Osteoporosis is a systemic metabolic disease based on age-dependent imbalance between the rates of bone formation and bone resorption. Recent studies on the pathogenesis of this disease identified that bone remodelling impairment, at the base of osteoporotic bone fragility, could be related to protein glycation, in association to oxidative stress. The glycation reactions lead to the generation of glycation end products (AGEs) which, in turn, accumulates into bone, where they binds to the receptor for AGE (RAGE). The aim of this study is to investigate the potential role of circulating sRAGE in osteoporosis, in particular evaluating the correlation of sRAGE with the fracture risk, in association with bone mineral density, the fracture risk marker FGF23, and lipid metabolism.

Results

Circulating level of soluble RAGE correlate with osteopenia and osteoporosis level. Serum sRAGE resulted clearly associated on the one hand to bone fragility and, on the other hand, with BMI and leptin. sRAGE is particularly informative because serum sRAGE is able to provide, as a single marker, information about both the aspects of osteoporotic disease, represented by bone fragility and lipid metabolism.

Conclusions

The measure serum level of sRAGE could have a potential diagnostic role in the monitoring of osteoporosis progression, in particular in the evaluation of fracture risk, starting from the prevention and screening stage, to the osteopenic level to osteoporosis.

Advanced Glycation End Product 3 (AGE3) Increases Apoptosis and the Expression of Sclerostin by Stimulating TGF-β Expression and Secretion in Osteocyte-Like MLO-Y4-A2 Cells

Advanced glycation end products (AGEs) cause bone fragility due to deterioration in bone quality. We previously reported that AGE3 induced apoptosis and inhibited differentiation via increased transforming growth factor (TGF)-β signaling in osteoblastic cells. Additionally, we demonstrated that AGE3 increased apoptosis and sclerostin expression and decreased receptor activator of nuclear factor-κB ligand (RANKL) expression in osteocyte-like cells. However, it remains unclear whether TGF-β signaling is involved in the effects of AGEs on apoptosis and the expression of sclerostin and RANKL in osteocytes. Effects of AGE3 on apoptosis of mouse osteocyte-like MLO-Y4-A2 cells were examined by DNA fragmentation ELISA. Expression of TGF-β, sclerostin, and RANKL was evaluated using real-time PCR, Western blotting, and ELISA kits. To block TGF-β signaling, we used SD208, a TGF-β type I receptor kinase inhibitor. AGE3 (200 µg/mL) significantly increased apoptosis and mRNA expression of Sost, the gene encoding sclerostin, and decreased Rankl mRNA expression in MLO-Y4-A2 cells. AGE3 significantly increased the expression of TGF-β. Co-incubation of SD208 with AGE3 significantly rescued AGE3-induced apoptosis in a dose-dependent manner. Moreover, SD208 restored AGE3-increased mRNA and protein expression of sclerostin. In contrast, SD208 did not affect AGE3-decreased mRNA and protein expression of RANKL. These findings suggest that AGE3 increases apoptosis and sclerostin expression through increasing TGF-β expression in osteocytes, and that AGE3 decreases RANKL expression independent of TGF-β signaling.

Association of osteoglycin and FAM5C with bone turnover markers, bone mineral density, and vertebral fractures in postmenopausal women with type 2 diabetes mellitus

OBJECTIVE

Accumulating evidence suggests a reciprocal relationship between muscle and bone. Previous in vitro studies showed that the muscle-derived factors, osteoglycin (OGN) and family with sequence similarity 5, member C (FAM5C), regulate osteoblastic differentiation. However, there are no reports investigating the association between circulating OGN and FAM5C and bone metabolism in humans.

DESIGN

We conducted a cross-sectional study and investigated the association of serum OGN and FAM5C levels and muscle mass examined by whole-body dual-energy x-ray absorptiometry with bone mineral density (BMD), bone turnover markers, and the presence of vertebral fractures (VFs) in 156 postmenopausal women with type 2 diabetes mellitus (T2DM).

RESULTS

Multiple regression analysis adjusted for age, duration of T2DM, body mass index, serum creatinine, and log(hemoglobin A1c) showed that log(OGN) was negatively associated with BMD at the femoral neck (β=-0.17, p=0.014). Serum OGN levels were higher in subjects with VFs than in those without VFs [mean±standard deviation (SD): 100.2±84.7 vs. 74.4±31.7pg/mL, p=0.013]. Moreover, logistic regression analysis adjusted for the confounding factors described above showed that the serum OGN level was positively associated with the presence of VFs (odds ratio=1.84, 95% confidence interval=1.03-3.29 per SD increase, p=0.039). In contrast, neither the serum FAM5C level nor muscle mass indices were associated with bone turnover markers and the presence of VFs.

CONCLUSIONS

The present study showed for the first time that higher serum OGN levels were associated with decreased BMD and increased risk of vertebral fractures in postmenopausal women with T2DM.

Advanced Glycation End Products, Diabetes, and Bone Strength

Diabetic patients have a higher fracture risk than expected by their bone mineral density (BMD). Poor bone quality is the most suitable and explainable cause for the elevated fracture risk in this population. Advanced glycation end products (AGEs), which are diverse compounds generated via a non-enzymatic reaction between reducing sugars and amine residues, physically affect the properties of the bone material, one of a component of bone quality, through their accumulation in the bone collagen fibers. On the other hand, these compounds biologically act as agonists for these receptors for AGEs (RAGE) and suppress bone metabolism. The concentrations of AGEs and endogenous secretory RAGE, which acts as a "decoy receptor" that inhibits the AGEs-RAGE signaling axis, are associated with fracture risk in a BMD-independent manner. AGEs are closely associated with the pathogenesis of this unique clinical manifestation through physical and biological mechanisms in patients with diabetes mellitus.

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.

Osteocalcin, under-carboxylated osteocalcin and osteopontin are not associated with gestational diabetes mellitus but are inversely associated with leptin in non-diabetic women

OBJECTIVE

To measure serum osteocalcin (OC), under-carboxylated osteocalcin (ucOC), osteopontin (OPN), and leptin in pregnant women with gestational diabetes mellitus (GDM) and in healthy pregnant women during pregnancy and after birth and relate these markers to glucose metabolism.

METHODS

This was a prospective study including 60 women with GDM and 60 subjects with normal gestation who were evaluated at gestational week 30 and 6 weeks postpartum. Serum OC, ucOC, OPN, leptin, insulin and insulin resistance were evaluated during the study.

RESULTS

Bone biomarkers and leptin were similar between GDM and normal pregnancy. After delivery, OC, ucOC and OPN increased in both groups, while leptin decreased only in healthy controls. Bone markers did not correlate with insulin and insulin resistance in the two groups, but leptin was positively correlated with insulin and insulin resistance and negatively correlated with bone biomarkers only in healthy women. Furthermore, the women who developed diabetes postpartum had lower levels of OC than women with normal glucose tolerance.

CONCLUSION

GDM is not associated with OC, ucOC, OPN, and leptin and does not correlate with insulin resistance. At postpartum, women who develop diabetes have lower osteocalcin concentrations. Leptin correlates with insulin resistance and bone biomarkers in non-diabetic women.

Effects of high glucose and advanced glycation end products on the expressions of sclerostin and RANKL as well as apoptosis in osteocyte-like MLO-Y4-A2 cells

In diabetes mellitus (DM), high glucose (HG) and advanced glycation end products (AGEs) are involved in bone quality deterioration. Osteocytes produce sclerostin and receptor activator of nuclear factor-кB ligand (RANKL) and regulate osteoblast and osteoclast function. However, whether HG or AGEs directly affect osteocytes and regulate sclerostin and RANKL production is unknown. Here, we examined the effects of HG, AGE2, and AGE3 on the expression of sclerostin and RANKL and on apoptosis in osteocyte-like MLO-Y4-A2 cells. Treatment of the cells with 22 mM glucose, 100 μg/mL either AGE2 or AGE3 significantly increased the expression of sclerostin protein and mRNA; however, both AGEs, but not glucose, significantly decreased the expression of RANKL protein and mRNA. Moreover, treatment of the cells with HG, AGE2, or AGE3 for 72 h induced significant apoptosis. These detrimental effects of HG, AGE2, and AGE3 on sclerostin and RANKL expressions and on apoptosis were antagonized by pretreatment of the cells with 10(-8) M human parathyroid hormone (PTH)-(1-34). Thus, HG and AGEs likely suppress bone formation by increasing sclerostin expression in osteocytes, whereas AGEs suppress bone resorption by decreasing RANKL expression. Together, these processes may cause low bone turnover in DM. In addition, HG and AGEs may cause cortical bone deterioration by inducing osteocyte apoptosis. PTH may effectively treat these pathological processes and improve osteocyte function.

Insights into bone fragility in diabetes: the crucial role of bone quality on skeletal strength

Meta-analyses have revealed that the relative risk of hip fractures in patients with type 1 and type 2 diabetes mellitus is higher than that in non-diabetic subjects. The risk of fracture in patients with diabetes mellitus increases along with a decrease in bone mineral density (BMD) similarly to those in non-diabetic patients. However, the observed risk of fracture is higher than expected one by BMD in both type 1 and type 2 diabetic patients, indicating that precise estimation of bone fragility by BMD values in patients with diabetes is difficult. Bone strength consists of BMD and bone quality, for this reason, poor bone quality is a most suitable and explicable cause for elevated fracture risk in this population. This bone fragility observed in patients with diabetes mellitus is caused by unique pathogenesis in diabetes, suggesting that osteoporosis in diabetic patients may be one of the diabetic complications and that specific diagnostic criteria for this osteoporosis is required. Bone quality indicators closely related to bone fragility are required to be identified to establish a diagnostic method for osteoporosis in patients with diabetes mellitus.