Advanced Glycation End Products, Diabetes, and Bone Strength

Prevalence of osteoporosis in chronic diseases: an umbrella review of 283 observational studies from 13 systematic reviews

INTRODUCTION

Osteoporosis is a disease characterized by decreased bone mineral density and deterioration of bone microarchitecture, which increases fracture risk. In the context of various chronic pathologies, this condition may present an even higher prevalence, impacting morbidity, mortality, and healthcare burden.

OBJECTIVE

To synthesize and compare available evidence from systematic reviews on the prevalence of osteoporosis across different chronic diseases.

METHODOLOGY

An umbrella review following PRISMA guidelines was conducted, focusing on systematic reviews (with or without meta-analysis) reporting prevalence data of osteoporosis in adults with at least one chronic disease. Databases, including PubMed/MEDLINE, Scopus, Web of Science, and EMBASE, were searched, covering publications between 2009 and 2023, without language restrictions. Two independent reviewers performed study selection and data extraction, resolving discrepancies through consensus. A risk of bias assessment was conducted using the ROBIS tool. Prevalence estimates reported in each review were analyzed, classifying diseases according to the magnitude of the percentages found.

RESULTS

Thirteen systematic reviews were evaluated (twelve included meta-analyses). The highest prevalence of osteoporosis was observed in patients with Chronic Obstructive Pulmonary Disease (up to 36.8%) and diabetes mellitus (approximately 27.7%). Other conditions, such as rheumatoid arthritis, multiple sclerosis, liver cirrhosis, and celiac disease, showed variable prevalence but were equally relevant in clinical terms. Methodological heterogeneity, both in diagnostic criteria and populations, was a notable factor.

CONCLUSIONS

The results highlight the need for systematic assessment of bone health in patients with chronic diseases, particularly those with a higher prevalence of osteoporosis. These findings underscore the importance of timely screening strategies and multidisciplinary approaches to prevent fractures and optimize comprehensive care.

CLINICAL TRIAL NUMBER

Not applicable.

Correlation between diabetes mellitus and refracture risk in patients with osteoporotic fractures: a retrospective cohort study

BACKGROUND

Diabetes and osteoporosis are frequent long-term conditions. There is little information on the relationship between diabetes and the risk of refracture in people who have osteoporotic fractures (OPFs), even though both conditions have been individually associated with increased fracture risk.

METHODS

We conducted a retrospective cohort study using the Osteoporotic Fracture Registry System of the Affiliated Kunshan Hospital of Jiangsu University. The study included 2,255 patients aged 50 years or older who were admitted with OPFs, comprising 107 with diabetes and 2,148 without. The risk of refracture within 1, 3, and 5 years was evaluated using Cox proportional hazard regression models based on whether or not a diabetes diagnosis was made during the admission assessment. Furthermore, the rates of refracture between individuals with and without diabetes were compared using Kaplan-Meier curves.

RESULTS

In patients with OPFs, diabetes was significantly positively correlated with refracture risk. For the follow-up periods of 1, 3, and 5 years, the hazard ratios (HRs) in the fully adjusted model were 2.83 (95% confidence interval [CI]: 1.09 to 7.39, P-value = 0.033), 2.65 (95% CI: 1.27 to 5.52, P-value = 0.009), and 2.72 (95% CI: 1.39 to 5.32, P-value = 0.004), respectively.

CONCLUSIONS

The findings highlight the importance of monitoring bone health and implementing preventative interventions in individuals with diabetes, since they reveal that diabetic patients face a risk of refracture that is more than twice as high as that of non-diabetic individuals.

Skeletal stem and progenitor cells in bone physiology, ageing and disease

Skeletal stem cells (SSCs) and related progenitors with osteogenic potential, collectively termed skeletal stem and/or progenitor cells (SSPCs), are crucial for providing osteoblasts for bone formation during homeostatic tissue turnover and fracture repair. Besides mediating normal bone physiology, they also have important roles in various metabolic bone diseases, including osteoporosis. SSPCs are of tremendous interest because they represent prime future targets for osteoanabolic therapies and bone regenerative medicine. Remarkable progress has been made in characterizing various SSC and SSPC populations in postnatal bone. SSPCs exist in the periosteum and within the bone marrow stroma, including subsets localizing around arteriolar and sinusoidal blood vessels; they can display osteogenic, chondrogenic, adipogenic and/or fibroblastic potential, and exert critical haematopoiesis-supportive functions. However, much remains to be clarified. By the current markers, bona fide SSCs are commonly contained within broader SSPC populations characterized by considerable heterogeneity and overlap, whose common versus specific functions in health and disease have not been fully unravelled. Here, we review the present knowledge of the identity, fates and relationships of SSPC populations in the postnatal bone environment, their contributions to bone maintenance, the changes observed upon ageing, and the effect of metabolic diseases such as osteoporosis and diabetes mellitus.

Fracture Risk Assessment in Metabolic Syndrome in Terms of Secondary Osteoporosis Potential. A Narrative Review

Osteoporosis is a major global public health problem with the associated bone fractures contributing significantly to both morbidity and mortality. In many countries, osteoporotic fractures will affect one in three women and one in five men over the age of 50. Similarly, diabetes, obesity, and metabolic syndrome (MetS) are among the leading public health problems due to their worldwide prevalence and burden on health budgets. Although seemingly disparate, metabolic disorders are known to affect bone health, and the interaction between fat and bone tissue is increasingly well understood. For example, it is now well established that diabetes mellitus (both type 1 and 2) is associated with fracture risk. In this narrative review, we focus on the potential link between MetS and bone health as expressed by bone mineral density and fracture risk. This narrative review demonstrates the association of MetS and its components with increased fracture risk, and also highlights the need for fracture risk assessment in patients with obesity and MetS.

Chronic Kidney Disease and Osteoarthritis: Current Understanding and Future Research Directions

Chronic kidney disease (CKD) is a significant public health concern. Osteoarthritis (OA), a common form of arthritis, has been shown to have a dramatically increased prevalence, particularly among individuals aged 40-50 and older, in the presence of CKD. Furthermore, CKD may exacerbate the progression and impact of OA. A survey study revealed that 53.9% of CKD patients undergoing long-term hemodialysis were diagnosed with OA. These findings underscore the potential association between CKD and OA. Uremic toxins, such as indoxyl sulfate, p-cresyl sulfate, transforming growth factor-β, and advanced glycation end-products, are regarded as potential risk factors in various CKD-related conditions, affecting bone and joint metabolism. However, whether these factors serve as a bridging mechanism between CKD and OA comorbidities, as well as their detailed roles in this context, remains unclear. Addressing the progression of OA in CKD patients and identifying effective treatment and prevention strategies is an urgent challenge that warrants immediate attention. This review focuses on describing and discussing the molecular pathological mechanisms underlying CKD-associated OA and the possible therapeutic strategies.

Impact of High Glucose on Bone Collagenous Matrix Composition, Structure, and Organization: An Integrative Analysis Using an Ex Vivo Model

Diabetes mellitus is a widespread metabolic disorder linked to numerous systemic complications, including adverse effects on skeletal health, such as increased bone fragility and fracture risk. Emerging evidence suggests that high glucose may disrupt the extracellular matrix (ECM) of bone, potentially altering its composition and organization. Collagen, the primary organic component of the ECM, is critical for maintaining structural integrity and biomechanical properties. However, definitive evidence and a comprehensive understanding of the molecular mechanisms through which high glucose impacts the ECM and collagen remain elusive. This study employed an ex vivo embryonic chicken femur model to investigate the effects of high glucose on the collagenous matrix. A comprehensive approach integrating histological evaluation, histomorphometry, ATR-FTIR spectroscopy, and proteomics was adopted to unravel structural, biochemical, and molecular changes in the ECM. Histomorphometric analysis revealed disrupted collagen fibril architecture, characterized by altered fibril diameter, alignment, and spatial organization. ATR-FTIR spectroscopy highlighted biochemical modifications, including non-enzymatic glycation that impaired collagen crosslinking and reduced matrix integrity. Proteomic profiling unveiled significant alterations in ECM composition and function, including downregulation of key collagen crosslinking enzymes and upregulation of inflammatory and coagulation pathways. High glucose profoundly disrupts the collagenous matrix of bone, weakening its structural integrity and organization. These findings emphasize the critical impact of high glucose environments on extracellular matrix composition and bone quality, offering insights into the mechanisms behind diabetic bone fragility and guiding future research toward targeted therapeutic strategies.

The Effect of Carnosine Supplementation on Musculoskeletal Health in Adults with Prediabetes and Type 2 Diabetes: A Secondary Analysis of a Randomized Controlled Trial

BACKGROUND/OBJECTIVES

Type 2 diabetes (T2D) is associated with an increased risk of adverse musculoskeletal outcomes likely due to heightened chronic inflammation, oxidative stress, and advanced glycation end-products (AGE). Carnosine has been shown to have anti-inflammatory, anti-oxidative, and anti-AGE properties. However, no clinical trials have examined the impact of carnosine on musculoskeletal health in adults with prediabetes or T2D.

METHODS

In a randomized, double-blind clinical trial, 49 participants with prediabetes or T2D and without existing musculoskeletal conditions were assigned to receive either 2 g/day carnosine or matching placebo for 14 weeks. Whole-body dual-energy X-ray absorptiometry (DXA) was used to assess body composition, and peripheral quantitative computed tomography (pQCT) was used to assess bone health at the distal and proximal tibia.

RESULTS

Forty-three participants completed this study. Carnosine supplementation had no effect on change in hand grip strength (HGS) or upper-limb relative strength (HGS/lean mass) versus placebo. Change in appendicular lean mass, percentage of body fat, visceral fat area, proximal tibial cortical volumetric bone mineral density (vBMD), distal tibial trabecular vBMD, and stress-strain index did not differ with carnosine compared to placebo. Fourteen weeks of carnosine supplementation did not improve muscle strength, body composition, or bone health in adults with prediabetes or T2D.

CONCLUSIONS

Carnosine supplementation may not be an effective approach for improving musculoskeletal health in adults with prediabetes and T2D without musculoskeletal conditions. However, appropriately powered trials with longer duration are warranted to confirm our findings. The trial was registered at clinicaltrials.gov (NCT02917928).

Glycemic status and bone health: investigating the impact of glycosylated hemoglobin on bone density in South Indian adults

Objective

To investigate the relationship between glycosylated Hemoglobin (HbA1c) levels and bone mineral density (BMD) in individuals with varying glycemic statuses, including diabetes, prediabetes, and controls.

Methods

This cross-sectional study conducted in Bengaluru, India, included 336 participants aged 20 to 60. Blood samples were taken to assess fasting blood glucose, HbA1c, and lipid profile. Participants were divided into tertiles based on HbA1c levels: low(HbA1c ≤ 5.5%), moderate(HbA1c > 5.5-6.0%), and high(HbA1c ≥ 6.1%).Dual energy-X-ray absorptiometry(DXA) measured hip, spine, and total BMD as indicators of bone health.

Results

Intermediate and high HbA1c tertiles had a significantly higher hip and total BMD compared to low HbA1c tertiles (p < 0.001 and p = 0.006 for hip and total BMD). Spine BMD was comparable between the three groups. After adjusting for age, gender and BMI, a potential independent effect of glycemic control on hip BMD was observed (Low vs. intermediate and high glycemic status: β: 0.041, 95% C.I.: 0.003, 0.078, p = 0.034).

Conclusion

Elevated HbA1c might be associated with higher hip and overall BMD as observed through DXA. Nonetheless, this doesn't necessarily imply better bone health; further evaluation is advised to prevent fractures.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01473-9.

Advanced glycosylation end products promote the progression of CKD-MBD in rats, and its natural inhibitor, quercetin, mitigates disease progression

Chronic kidney disease-mineral and bone metabolism disorder (CKD-MBD) is a common chronic kidney disease (CKD)-associated complication that increases the risk of metabolic bone diseases, fractures, osteoblastic trans-differentiation of vascular smooth muscle cells, and cardiovascular events. SD rats were randomised into five groups with six rats per group: sham, CKD, CKD + advanced glycosylation end products (AGEs), CKD + Quercetin, and CKD + AGEs + Quercetin. The protective effects of AGEs and quercetin on SD rats were assessed by renal function, renal pathology, bone metabolism, osteoblastic trans-differentiation of vascular smooth muscle cells, and the receptor for AGE (RAGE) expression. Compared with the control group, rats in the CKD and CKD + AGEs groups had significantly lower body weight, higher serum AGEs levels, impaired renal function, increased levels of oxidative stress in the kidney and bone marrow tissues, lower femoral bone mineral density (BMD), callus mineralised volume fraction (mineralised bone volume/total volume), abnormal serum bone metabolism levels, and increased renal tissue, bone tissue, and abdominal aorta RAGE expression levels, and the RAGE downstream NF-κB signalling pathway was upregulated. Quercetin significantly improved renal dysfunction, attenuated serum AGE levels, reduced oxidative stress levels in the kidney and bone marrow tissues, and downregulated RAGE expression in the kidney, bone, and abdominal aorta and the RAGE downstream NF-κB signalling pathway in rats with CKD. AGEs are involved in the pathogenesis of CKD-MBD by promoting osteoblastic trans-differentiation of vascular smooth muscle cells and abnormal bone metabolism. Quercetin plays a role in the prevention and treatment of CKD-MBD by reducing the production of AGEs.

Mineral and cross-linking in collagen fibrils: The mechanical behavior of bone tissue at the nano-scale

The mineralized collagen fibril is the main building block of hard tissues and it directly affects the macroscopic mechanics of biological tissues such as bone. The mechanical behavior of the fibril itself is determined by its structure: the content of collagen molecules, minerals, and cross-links, and the mechanical interactions and properties of these components. Advanced glycation end products (AGEs) form cross-links between tropocollagen molecules within the collagen fibril and are one important factor that is believed to have a major influence on the tissue. For instance, it has been shown that brittleness in bone correlates with increased AGEs densities. However, the underlying nano-scale mechanisms within the mineralized collagen fibril remain unknown. Here, we study the effect of mineral and AGEs cross-linking on fibril deformation and fracture behavior by performing destructive tensile tests using coarse-grained molecular dynamics simulations. Our results demonstrate that after exceeding a critical content of mineral, it induces stiffening of the collagen fibril at high strain levels. We show that mineral morphology and location affect collagen fibril mechanics: The mineral content at which this stiffening occurs depends on the mineral's location and morphology. Further, both, increasing AGEs density and mineral content lead to stiffening and increased peak stresses. At low mineral contents, the mechanical response of the fibril is dominated by the AGEs, while at high mineral contents, the mineral itself determines fibril mechanics.

The association of type 2 diabetes-related characteristics with fracture risk at different sites

AIM

To determine the association of diabetes-related characteristics with fractures at different sites in individuals with type 2 diabetes (T2D).

MATERIALS AND METHODS

We conducted a cohort study using the Clinical Practice Research Datalink (CPRD) GOLD. Patients aged over 30 years with T2D were identified within the CPRD. Patients were followed from the start of diabetes treatment until the end of data collection, death, or the occurrence of a fracture. Cox proportional hazards models were used to estimate the hazard ratios for the association of the individual characteristics (diabetes duration, glycated haemoglobin [HbA1c] level, and microvascular complications) with fracture risk, adjusted for demographics, comorbidities and comedication.

RESULTS

A diabetes duration of >10 years was associated with an increased risk of any fracture and major osteoporotic fractures (MOFs), while a diabetes duration of >8 years was associated with an increased hip fracture risk, compared to a duration <2 years. An HbA1c level <6% was associated with an increased fracture risk compared to HbA1c values of 6% to <7%. The presence of one or two microvascular complications was associated with an increased risk of any fracture and MOFs and the presence of two microvascular complications was associated with an increased hip fracture risk, compared to no microvascular complications.

CONCLUSION

In conclusion, our study shows that a diabetes duration of 10 years or more, strict glycaemic control resulting in HbA1c levels below 6%, and/or the presence of at least one microvascular complication increased the risk of any fracture, hip fractures, MOFs, and humerus fractures, but not ankle, scapula or skull fractures.

Osteoking prevents bone loss and enhances osteoblastic bone formation by modulating the AGEs/IGF-1/β-catenin/OPG pathway in type 2 diabetic db/db mice

Type 2 diabetic osteoporosis (T2DOP) is a skeletal metabolic syndrome characterized by impaired bone remodeling due to type 2 diabetes mellitus, and there are drawbacks in the present treatment. Osteoking (OK) is widely used for treating fractures and femoral head necrosis. However, OK is seldom reported in the field of T2DOP, and its role and mechanism of action need to be elucidated. Consequently, this study investigated whether OK improves bone remodeling and the mechanisms of diabetes-induced injury. We used db/db mice as a T2DOP model and stimulated MC3T3-E1 cells (osteoblast cell line) with high glucose (HG, 50 mM) and advanced glycation end products (AGEs, 100 µg/mL), respectively. The effect of OK on T2DOP was assessed using a combined 3-point mechanical bending test, hematoxylin and eosin staining, and enzyme-linked immunosorbent assay. The effect of OK on enhancing MC3T3-E1 cell differentiation and mineralization under HG and AGEs conditions was assessed by an alkaline phosphatase activity assay and alizarin red S staining. The AGEs/insulin-like growth factor-1(IGF-1)/β-catenin/osteoprotegerin (OPG) pathway-associated protein levels were assayed by western blot analysis and immunohistochemical staining. We found that OK reduced hyperglycemia, attenuated bone damage, repaired bone remodeling, increased tibial and femoral IGF-1, β-catenin, and OPG expression, and decreased receptor activator of nuclear kappa B ligand and receptor activator of nuclear kappa B expression in db/db mice. Moreover, OK promoted the differentiation and mineralization of MC3T3-E1 cells under HG and AGEs conditions, respectively, and regulated the levels of AGEs/IGF-1/β-catenin/OPG pathway-associated proteins. In conclusion, our results suggest that OK may lower blood glucose, alleviate bone damage, and attenuate T2DOP, in part through activation of the AGEs/IGF-1/β-catenin/OPG pathway.

A Review of Animal Models for Studying Bone Health in Type-2 Diabetes Mellitus (T2DM) and Obesity

Preclinical research on diabetes and obesity has been carried out in various animal models over the years. These animal models are developed from genetic manipulation that affects their body metabolism, chemical-induced procedures, diet alteration/modifications, or combinations of the aforementioned approaches. The diabetic and obesity animal models have allowed researchers to not only study the pathological aspect of the diseases but also enable them to screen and explore potential therapeutic compounds. Besides several widely known complications such as macrovascular diseases, diabetic neuropathy, nephropathy and retinopathy, type 2 diabetes mellitus is also known to affect bone health. There is also evidence to suggest obesity affects bone health. Therefore, continuous research needs to be conducted to find a remedy or solution to this matter. Previous literature reported evidence of bone loss in animal models of diabetes and obesity. These findings, as highlighted in this review, further augment the suggestion of an inter-relationship between diabetes, obesity and bone loss.

Bone effects of metformin monotherapy and its combination with teneligliptin: A 12-week follow-up study in patients with type 2 diabetes mellitus

AIMS

The skeletal effects of metformin monotherapy and in combination with teneligliptin are not well illustrated in patients with T2DM. To address this, we conducted an observational study to evaluate the effect of these oral hypoglycemic agents on bone turnover markers.

METHODS

We recruited patients with T2DM and first-ever prescribed metformin monotherapy or metformin combined with teneligliptin from a tertiary care teaching hospital in New Delhi, North India. Both bone formation and resorption markers, IL-6 and PTD, were estimated along with glycated hemoglobin at baseline and 12 weeks.

RESULTS

In both groups, hbA1c levels decreased significantly from baseline to 12 weeks. In the metformin-treated group, β-CTX, sRANKL, IL-6, and PTD decreased significantly, and no significant changes were observed in P1NP, OC, BAP, or OPG at 12 weeks from baseline. In the metformin + teneligliptin group, BAP, β-CTX, sRANKL, IL-6, and PTD decreased significantly, and no significant changes were observed in P1NP, OC, or OPG after 12 weeks from baseline.

CONCLUSIONS

The positive bone outcome of metformin or teneligliptin was linked to bone resorption rather than bone formation and was independent of changes in HbA1c or PTD. However, these results must be confirmed with well-designed RCTs with more extended follow-up periods.

Metabolic regulation of skeletal cell fate and function

Bone development and bone remodelling during adult life are highly anabolic processes requiring an adequate supply of oxygen and nutrients. Bone-forming osteoblasts and bone-resorbing osteoclasts interact closely to preserve bone mass and architecture and are often located close to blood vessels. Chondrocytes within the developing growth plate ensure that bone lengthening occurs before puberty, but these cells function in an avascular environment. With ageing, numerous bone marrow adipocytes appear, often with negative effects on bone properties. Many studies have now indicated that skeletal cells have specific metabolic profiles that correspond to the nutritional microenvironment and their stage-specific functions. These metabolic networks provide not only skeletal cells with sufficient energy, but also biosynthetic intermediates that are necessary for proliferation and extracellular matrix synthesis. Moreover, these metabolic pathways control redox homeostasis to avoid oxidative stress and safeguard cell survival. Finally, several intracellular metabolites regulate the activity of epigenetic enzymes and thus control the fate and function of skeletal cells. The metabolic profile of skeletal cells therefore not only reflects their cellular state, but can also drive cellular activity. Insight into skeletal cell metabolism will thus not only advance our understanding of skeletal development and homeostasis, but also of skeletal disorders, such as osteoarthritis, diabetic bone disease and bone malignancies.

Cascade Reactions Catalyzed by Gold Hybrid Nanoparticles Generate CO Gas Against Periodontitis in Diabetes

The treatment of diabetic periodontitis poses a significant challenge due to the presence of local inflammation characterized by excessive glucose concentration, bacterial infection, and high oxidative stress. Herein, mesoporous silica nanoparticles (MSN) are embellished with gold nanoparticles (Au NPs) and loaded with manganese carbonyl to prepare a carbon monoxide (CO) enhanced multienzyme cooperative hybrid nanoplatform (MSN-Au@CO). The Glucose-like oxidase activity of Au NPs catalyzes the oxidation of glucose to hydrogen peroxide (H2O2) and gluconic acid，and then converts H2O2 to hydroxyl radicals (•OH) by peroxidase-like activity to destroy bacteria. Moreover, CO production in response to H2O2, together with Au NPs exhibited a synergistic anti-inflammatory effect in macrophages challenged by lipopolysaccharides. The underlying mechanism can be the induction of nuclear factor erythroid 2-related factor 2 to reduce reactive oxygen species, and inhibition of nuclear factor kappa-B signaling to diminish inflammatory response. Importantly, the antibacterial and anti-inflammation effects of MSN-Au@CO are validated in diabetic rats with ligature-induced periodontitis by showing decreased periodontal bone loss with good biocompatibility. To summarize, MSN-Au@CO is fabricate to utilize glucose-activated cascade reaction to eliminate bacteria, and synergize with gas therapy to regulate the immune microenvironment, offering a potential direction for the treatment of diabetic periodontitis.

Bone canonical Wnt signaling is downregulated in type 2 diabetes and associates with higher advanced glycation end-products (AGEs) content and reduced bone strength

Type 2 diabetes (T2D) is associated with higher fracture risk, despite normal or high bone mineral density. We reported that bone formation genes (SOST and RUNX2) and advanced glycation end-products (AGEs) were impaired in T2D. We investigated Wnt signaling regulation and its association with AGEs accumulation and bone strength in T2D from bone tissue of 15 T2D and 21 non-diabetic postmenopausal women undergoing hip arthroplasty. Bone histomorphometry revealed a trend of low mineralized volume in T2D (T2D 0.249% [0.156-0.366]) vs non-diabetic subjects 0.352% [0.269-0.454]; p=0.053, as well as reduced bone strength (T2D 21.60 MPa [13.46-30.10] vs non-diabetic subjects 76.24 MPa [26.81-132.9]; p=0.002). We also showed that gene expression of Wnt agonists LEF-1 (p=0.0136) and WNT10B (p=0.0302) were lower in T2D. Conversely, gene expression of WNT5A (p=0.0232), SOST (p<0.0001), and GSK3B (p=0.0456) were higher, while collagen (COL1A1) was lower in T2D (p=0.0482). AGEs content was associated with SOST and WNT5A (r=0.9231, p<0.0001; r=0.6751, p=0.0322), but inversely correlated with LEF-1 and COL1A1 (r=-0.7500, p=0.0255; r=-0.9762, p=0.0004). SOST was associated with glycemic control and disease duration (r=0.4846, p=0.0043; r=0.7107, p=0.00174), whereas WNT5A and GSK3B were only correlated with glycemic control (r=0.5589, p=0.0037; r=0.4901, p=0.0051). Finally, Young's modulus was negatively correlated with SOST (r=-0.5675, p=0.0011), AXIN2 (r=-0.5523, p=0.0042), and SFRP5 (r=-0.4442, p=0.0437), while positively correlated with LEF-1 (r=0.4116, p=0.0295) and WNT10B (r=0.6697, p=0.0001). These findings suggest that Wnt signaling and AGEs could be the main determinants of bone fragility in T2D.

Mineral and cross-linking in collagen fibrils: The mechanical behavior of bone tissue at the nano-scale

The mineralized collagen fibril is the main building block of hard tissues and it directly affects the macroscopic mechanics of biological tissues such as bone. The mechanical behavior of the fibril itself is determined by its structure: the content of collagen molecules, minerals, and cross-links, and the mechanical interactions and properties of these components. Advanced-Glycation-Endproducts (AGEs) cross-linking between tropocollagen molecules within the collagen fibril is one important factor that is believed to have a major influence on the tissue. For instance, it has been shown that brittleness in bone correlates with increased AGEs densities. However, the underlying nano-scale mechanisms within the mineralized collagen fibril remain unknown. Here, we study the effect of mineral and AGEs cross-linking on fibril deformation and fracture behavior by performing destructive tensile tests using coarse-grained molecular dynamics simulations. Our results demonstrate that after exceeding a critical content of mineral, it induces stiffening of the collagen fibril at high strain levels. We show that mineral morphology and location affect collagen fibril mechanics: The mineral content at which this stiffening occurs depends on the mineral's location and morphology. Further, both, increasing AGEs density and mineral content lead to stiffening and increased peak stresses. At low mineral contents, the mechanical response of the fibril is dominated by the AGEs, while at high mineral contents, the mineral itself determines fibril mechanics.

Total serum pentosidine quantification using liquid chromatography-tandem mass spectrometry

Pentosidine (PEN) is an Advanced Glycation End-product (AGE) that is known to accumulate in bone collagen with aging and contribute to fracture risk. The PEN content in bone is correlated with serum PEN, making it an attractive, potential osteoporosis biomarker. We sought to develop a method for quantifying PEN in stored serum. After conducting a systematic narrative review of PEN quantification methodologies, we developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for quantifying total serum PEN. Our method is both sensitive and precise (LOD 2 nM, LOQ 5 nM, %CV < 6.5 % and recovery 91.2-100.7 %). Our method is also equivalent or better than other methods identified in our review. Additionally, LC-MS/MS avoids the pitfalls and limitations of using fluorescence as a means of detection and could be adapted to investigate a broad range of AGE compounds.

Scopoletin: a review of its pharmacology, pharmacokinetics, and toxicity

Scopoletin is a coumarin synthesized by diverse medicinal and edible plants, which plays a vital role as a therapeutic and chemopreventive agent in the treatment of a variety of diseases. In this review, an overview of the pharmacology, pharmacokinetics, and toxicity of scopoletin is provided. In addition, the prospects and outlook for future studies are appraised. Scopoletin is indicated to have antimicrobial, anticancer, anti-inflammation, anti-angiogenesis, anti-oxidation, antidiabetic, antihypertensive, hepatoprotective, and neuroprotective properties and immunomodulatory effects in both in vitro and in vivo experimental trials. In addition, it is an inhibitor of various enzymes, including choline acetyltransferase, acetylcholinesterase, and monoamine oxidase. Pharmacokinetic studies have demonstrated the low bioavailability, rapid absorption, and extensive metabolism of scopoletin. These properties may be associated with its poor solubility in aqueous media. In addition, toxicity research indicates the non-toxicity of scopoletin to most cell types tested to date, suggesting that scopoletin will neither induce treatment-associated mortality nor abnormal performance with the test dose. Considering its favorable pharmacological activities, scopoletin has the potential to act as a drug candidate in the treatment of cancer, liver disease, diabetes, neurodegenerative disease, and mental disorders. In view of its merits and limitations, scopoletin is a suitable lead compound for the development of new, efficient, and low-toxicity derivatives. Additional studies are needed to explore its molecular mechanisms and targets, verify its toxicity, and promote its oral bioavailability.

Advanced glycation end products are not associated with bone mineral density, trabecular bone score, and bone turnover markers in adults with and without type 1 diabetes: a cross-sectional study

It is unclear if AGEs are involved in the bone fragility of type 1 diabetes (T1D). We evaluated whether skin AGEs by skin autofluorescence and serum AGEs (pentosidine, carboxymethyl-lysine [CML]) are independently associated with BMD by DXA (lumbar spine, hip, distal radius), trabecular bone score (TBS), serum bone turnover markers (BTMs: CTX; P1NP; osteocalcin), and sclerostin in participants with and without T1D. Linear regression models were used, with interaction terms to test effect modification by T1D status. In participants with T1D, correlations between skin and serum AGEs as well as between AGEs and 3-year HbA1C were evaluated using Spearman's correlations. Data are mean ± SD or median (interquartile range). We included individuals who participated in a cross-sectional study and had BMD and TBS assessment (106 T1D/65 controls, 53.2% women, age 43 ± 15 yr, BMI 26.6 ± 5.5 kg/m2). Participants with T1D had diabetes for 27.6 ± 12.3 yr, a mean 3-yr HbA1C of 7.5 ± 0.9% and skin AGEs of 2.15 ± 0.54 arbitrary units. A subgroup of 65 T1D/57 controls had BTMs and sclerostin measurements, and those with T1D also had serum pentosidine (16.8[8.2-32.0] ng/mL) and CML [48.0 ± 16.8] ng/mL) measured. Femoral neck BMD, TBS, and BTMs were lower, while sclerostin levels were similar in participants with T1D vs controls. T1D status did not modify the associations between AGEs and bone outcomes. Skin AGEs were significantly associated with total hip and femoral neck BMD, TBS, BTMs, and sclerostin before, but not after, adjustment for confounders. Serum AGEs were not associated with any bone outcome. There were no significant correlations between skin and serum AGEs or between AGEs and 3-yr HbA1C. In conclusion, skin and serum AGEs are not independently associated with BMD, TBS, BTMs, and sclerostin in participants with relatively well-controlled T1D and participants without diabetes.

Trabecular bone score in adults with type 1 diabetes: a meta-analysis

Type 1 diabetes mellitus (T1DM) is associated with a disproportionately high fracture rate despite a minimal decrease in bone mineral density. Though trabecular bone score (TBS), an indirect measure of bone architecture, is lower in adults with T1DM, the modest difference is unlikely to account for the large excess risk and calls for further exploration.

INTRODUCTION

Fracture rates in type 1 diabetes mellitus (T1DM) are disproportionately high compared to the modestly low bone mineral density (BMD). Distortion of bone microarchitecture compromises bone quality in T1DM and is indirectly measured by trabecular bone score (TBS). TBS could potentially be used as a screening tool for skeletal assessment; however, there are inconsistencies in the studies evaluating TBS in T1DM. We performed this meta-analysis to address this knowledge gap.

METHODS

An electronic literature search was conducted using PubMed, Scopus, and Web of Science resources (all-year time span) to identify studies relating to TBS in T1DM. Cross-sectional and retrospective studies in adults with T1DM were included. TBS and BMD data were extracted for pooled analysis. Fracture risk could not be analyzed as there were insufficient studies reporting it.

RESULT

Data from six studies were included (T1DM: n = 378 and controls: n = 286). Pooled analysis showed a significantly lower TBS [standardized mean difference (SMD) =  - 0.37, 95% CI - 0.52 to - 0.21; p < 0.00001] in T1DM compared to controls. There was no difference in the lumbar spine BMD (6 studies, SMD - 0.06, 95% CI - 0.22 to 0.09; p = 0.43) and total hip BMD (6 studies, SMD - 0.17, 95% CI - 0.35 to 0.01; p = 0.06) in the case and control groups.

CONCLUSIONS

Adults with T1DM have a lower TBS but similar total hip and lumbar spine BMD compared to controls. The risk attributable to the significant but limited difference in TBS falls short of explaining the large excess propensity to fragility fracture in adults with T1DM. Further studies on clarification of the mechanism and whether TBS is suited to screen for fracture risk in adults with T1DM are necessary.

Diabetes-related Screw Loosening: The Distinction of Surgical Sites and the Relationship among Diabetes, Implant Stabilization and Clinical Outcomes

OBJECTIVES

Diabetes mellitus (DM) is correlated with poor clinical outcomes in spinal surgery. However, the effect of it on screw stabilization has not been investigated. The aim of this study was to evaluate the screw loosening rate and postoperative outcomes in diabetic patients and to identify potential risk factors associated with loosening.

METHODS

This was a retrospective study. Two hundred and forty-three patients who received cervical or lumbar internal fixation between 2015 and 2019 were enrolled. Screw loosening was assessed on radiography, and clinical outcomes were evaluated by the improvement of visual analogue scale (VAS), Oswestry disability index (ODI) or Japanese Orthopaedic Association (JOA) scores. The relationship of DM, screw loosening and clinical outcomes were analyzed with chi-square tests and regression analyses.

RESULTS

One hundred and twenty-two patients (50.2%) with diabetes were included in this study. Diabetes led to the increase of the rate of screw loosening in the lumbar spine, while the loosening rate did not vary significantly in the cervical spine. The occurrence of screw loosening in the lumbar spine was more likely to be associated with clinical outcomes for motor performance including walking and sitting. However, no significant effect on JOA and VAS scores in the cervical spine of screw loosening was found. Moreover, the history of DM affected the outcomes of the patients who underwent spinal surgery.

CONCLUSION

DM had an adverse effect on screw stabilization. The impaired improvement of clinical outcomes in diabetics after spinal surgery was related to screw loosening. In addition to the direct effects on operative wounds and neural function, the impact on the screws due to DM was also worth noting.

Intra-articular site-specific distribution of advanced glycation end products in the shoulder of patients with diabetes mellitus having rotator cuff tears

BACKGROUND

Advanced glycation end products (AGEs) are compounds formed due to aging and diabetes mellitus (DM). They activate NADPH oxidase (NOX) by binding to their receptors, thereby increasing the production of reactive oxygen species (ROS), which cause oxidative stress. In this study, we investigated the effects of AGEs on the tissues of the shoulder joint (such as rotator cuff synovium, and capsule) in patients with DM having rotator cuff tears.

METHODS

This study included eight patients with DM who underwent surgical treatment for rotator cuff tears with contracture. The rotator cuff, synovium, and joint capsule were harvested at the time of surgery and evaluated by hematoxylin-eosin staining. Furthermore, immunostaining was used for evaluating AGEs and receptor for AGEs (RAGE), cell activity, ROS, and apoptosis. Quantitative real-time polymerase chain reaction (qPCR) was employed for the cellular evaluation of NOX, interleukins, RAGE, and collagen.

RESULTS

The AGEs and RAGE staining as well as the ratio of ROS and apoptosis were in the following order: rotator cuff > joint capsule > synovium. In contrast, the cellular activity was significantly higher in the synovium than in the other regions. The type I collagen expression (as shown by qPCR) as well as the RAGE and NOX expressions were as follows: rotator cuff > joint capsule > synovium. Conversely, the expression of inflammatory cytokines (i.e., IL-6 and IL-1β) was higher in the synovium than in the other regions.

CONCLUSIONS

Our study is among the first to evaluate the effects of AGEs on each tissue of the shoulder joint in patients with DM having rotator cuff tears and contractures. The accumulation of AGEs in each tissue of the shoulder joint could reveal the locations affected by DM, which can lead to a better understanding of the pathophysiology of DM-related shoulder diseases.

Advanced glycation and glycoxidation end products in bone

Hyperglycemia and oxidative stress, enhanced in diabetes and aging, result in excessive accumulation of advanced glycation and glycoxidation end products (AGEs/AGOEs) in bone. AGEs/AGOES are considered to be "the missing link" in explaining increased skeletal fragility with diabetes, aging, and osteoporosis where increased fracture risk cannot be solely explained by bone mass and/or fall incidences. AGEs/AGOEs disrupt bone turnover and deteriorate bone quality through alterations of organic matrix (collagen and non-collagenous proteins), mineral, and water content. AGEs and AGOEs are also associated with bone fragility in other conditions such as Alzheimer's disease, circadian rhythm disruption, and cancer. This review explains how AGEs and AGOEs accumulate in bone and impact bone quality and bone fracture, and how AGES/AGOEs are being targeted in preclinical and clinical investigations for inhibition or removal, and for prediction and management of diabetic, osteoporotic and insufficiency fractures.

AGEs accumulation with vascular complications, glycemic control and metabolic syndrome: A narrative review

BACKGROUND

Multiple pathogenetic mechanisms are involved in the genesis of various microvascular and macrovascular complications of diabetes mellitus. Of all these, advanced glycation end products (AGEs) have been strongly implicated.

OBJECTIVES

The present narrative review aims to summarize the available literature on the genesis of AGEs and their potential role in the causation of both micro- and macrovascular complications of diabetes mellitus.

RESULTS

Uncontrolled hyperglycemia triggers the formation of AGEs through non-enzymatic glycation reactions between reducing sugars and proteins, lipids, or nucleic acids. AGEs accumulate in bloodstream and bodily tissues under chronic hyperglycemia. AGEs create irreversible cross-linkages of various intra- and extracellular molecules and activate the receptor for advanced glycation end products (RAGE), which stimulates downstream signaling pathways that generate reactive oxygen species (ROS) and contribute to oxidative stress. Additionally, intracellular glycation of mitochondrial respiratory chain proteins by AGEs contributes to the further generation of ROS, which, in turn, sets a vicious cycle that further promotes the production of endogenous AGEs. Through these pathways, AGEs play a principal role in the pathogenesis of various diabetic complications, including diabetic retinopathy, nephropathy, neuropathy, bone disease, atherosclerosis and non-alcoholic fatty liver disease. Multiple clinical studies and meta-analyses have revealed a positive association between tissue or circulating levels of AGEs and development of various diabetic complications. Besides, exogenous AGEs, primarily those derived from diets, promote insulin resistance, obesity, and metabolic syndrome.

CONCLUSIONS

AGEs, triggered by chronic hyperglycemia, play a pivotal role in the pathogenesis of various complications of diabetes mellitus.

Accumulation of advanced glycation end products promotes atrophic nonunion incidence in mice through a CtBP1/2-dependent mechanism

Atrophic nonunion (AN) is a complex and poorly understood pathological condition resulting from impaired fracture healing. Advanced glycation end products (AGEs) have been implicated in the pathogenesis of several bone disorders, including osteoporosis and osteoarthritis. However, the role of AGEs in the development of AN remains unclear. This study found that mice fed a high-AGE diet had a higher incidence of atrophic nonunion (AN) compared to mice fed a normal diet following tibial fractures. AGEs induced two C-terminal binding proteins (CtBPs), CtBP1 and CtBP2, which were necessary for the development of AN in response to AGE accumulation. Feeding a high-AGE diet after fracture surgery in CtBP1/2-/- and RAGE-/- (receptor of AGE) mice did not result in a significant occurrence of AN. Molecular investigation revealed that CtBP1 and CtBP2 formed a heterodimer that was recruited by histone deacetylase 1 (HDAC1) and runt-related transcription factor 2 (Runx2) to assemble a complex. The CtBP1/2-HDAC1-Runx2 complex was responsible for the downregulation of two classes of bone development and differentiation genes, including bone morphogenic proteins (BMPs) and matrix metalloproteinases (MMPs). These findings demonstrate that AGE accumulation promotes the incidence of AN in a CtBP1/2-dependent manner, possibly by modulating genes related to bone development and fracture healing. These results provide new insights into the pathogenesis of AN and suggest new therapeutic targets for its prevention and treatment.

Genetic activation of glycolysis in osteoblasts preserves bone mass in type I diabetes

Type I diabetes (T1D) impairs bone accrual in patients, but the mechanism is unclear. Here in a murine monogenic model for T1D, we demonstrate that diabetes suppresses bone formation resulting in a rapid loss of both cortical and trabecular bone. Single-cell RNA sequencing uncovers metabolic dysregulation in bone marrow osteogenic cells of diabetic mice. In vivo stable isotope tracing reveals impaired glycolysis in diabetic bone that is highly responsive to insulin stimulation. Remarkably, deletion of the insulin receptor reduces cortical but not trabecular bone. Increasing glucose uptake by overexpressing Glut1 in osteoblasts exacerbates bone defects in T1D mice. Conversely, activation of glycolysis by Pfkfb3 overexpression preserves both trabecular and cortical bone mass in the face of diabetes. The study identifies defective glucose metabolism in osteoblasts as a pathogenic mechanism for osteopenia in T1D, and furthermore implicates boosting osteoblast glycolysis as a potential bone anabolic therapy.

Osteoporosis and diabetes - possible links and diagnostic difficulties

Objectives

In this review, the authors aimed to clarify the relationship between the occurrence of osteoporosis and diabetes, analyze the differences between the pathogenesis of osteoporosis in different types of diabetes and propose the most effective diagnostic strategy and fracture risk assessment in diabetic patients.

Material and methods

A analysis of publications in MEDLINE, COCHRANE and SCOPUS databases was performed, searching for reports on the diagnostics, fracture risk assessment, prevention, and treatment of osteoporosis in patients with diabetes mellitus (DM) published in the years 2016-2022. The key words for the search were: diabetes, osteoporosis, and low-energy fracture.

Results

Bone complications of T1DM are more severe than T2DM, because of the lack of anabolic effect of insulin on bones. In T2DM the risk of fractures is elevated; however, identifying the mechanisms underlying the increased risk of fractures in T2DM is not clear. The FRAX tool is not appropriate for assessing the fracture risk in young patients with T1DM. It is quite useful in older patients with T2DM, but in these patients the calculated fracture risk may be underestimated. In T2DM the fracture risk often does not correspond to BMD value as measured by dual-energy X-ray absorptiometry (DXA). Diagnostic tools such as the trabecular bone score may play a significant role in this group of patients. Conclusions: Optimal strategies to identify and treat high risk individuals require further research and proper definition. The diagnostic criteria for osteoporosis should be clearly defined as well as fracture risk assessment and choice of anti-osteoporotic medication. In all cases of secondary osteoporosis, treatment of the underlying disease is the most important. The relationship between high risk of fractures and diabetes is inseparable, and its full understanding seems to be the key to effective management.

Bone Mineral Density Evaluation Among Type 2 Diabetic Patients in Rural Haryana, India: An Analytical Cross-Sectional Study

Background and objective Diabetes is one of the most prevalent diseases globally, affecting almost all organ systems. The relationship between type 2 diabetes mellitus (T2DM) and bone mineral density (BMD) has been a matter of controversy, and data from developing countries in this regard is highly scarce. Early detection of low BMD in diabetic patients will help prevent further bone loss and risk of fragility fracture. In this study, we aimed to assess the effect of T2DM on BMD among the rural population of Haryana, India. Materials and methods This was a cross-sectional study involving 850 patients between 25 and 60 years of age, including 425 diabetic and 425 non-diabetic subjects (as controls). Calcaneus BMD was measured by using quantitative ultrasound (QUS), and the data were compared against matched parameters in both groups. Results The mean age of diabetics was 42.21 ± 10.5 years and that of non-diabetics was 42.18 ± 10.4 years. The mean BMI was 27.8 ± 4.17 kg/m2 in diabetics and 21.6 ± 3.32 kg/m2 in the non-diabetic control group. BMD values significantly differed between the groups: -4.3 ± 1.23 vs. -2.6 ± 0.34 in diabetics and non-diabetics, respectively (p=0.002). Conclusion A significant difference in BMD was observed between the diabetic and non-diabetic groups. Based on our findings, We recommend that all type 2 diabetics be screened for osteoporosis so that this silent bone loss can be detected in the early phase itself and appropriate preventive measures can be promptly initiated.

A pilot study on the comparative evaluation of residual periodontal ligament in extracted teeth of chronic periodontitis patients with and without type 2 diabetes - Vital function of an occult dimension

Background

Periodontitis is the most common type of periodontal condition, primarily affecting middle-aged people and resulting in tooth loss; when combined with diabetes, it becomes a debilitating condition. The aim of this study is to compare the residual periodontal ligament length in periodontitis patients with and without diabetes.

Materials and Methods

The cross-sectional observational study was conducted in the department of periodontics over 5 months. The patients in the study were divided into two groups. Group 1 comprised patients with periodontitis without type 2 diabetes and Group 2 comprised patients with periodontitis with type 2 diabetes. A total of 100 teeth 50 from each group were collected. The teeth were stained, and the Residual Periodontal Ligament (RPL) of all tooth aspects and surfaces to a total of 544 were measured. Two points were identified for measuring the RPL. The first point was from the apex of the tooth and the second point was the highest marking of the stain. The length from these two points was recorded as the RPL. Following which, means from Groups 1 and 2 were calculated to determine the rate of destruction. The average of the values for each tooth was calculated to determine the percentage of RPL in each tooth and surface. The Mann-Whitney test was used to compare the RPL of the teeth surfaces and Group 1 and Group 2 and P < 0.05 was considered statistically significant.

Results

The RPL was higher in nondiabetic patients, with a mean value of 23.66 mm, when compared to diabetic patients, with a mean RPL of 17.05 mm, implying that diabetic patients showed greater periodontal destruction. Buccal tooth surfaces displayed a mean RPL of 4.24 mm and 6.00 mm, lingual/palatal tooth surfaces with 4.02 mm and 5.91 mm, mesial tooth surfaces with 3.82 mm and 5.64 mm, and distal tooth surfaces showed 4.14 mm and 5.67 mm (diabetic and nondiabetic, respectively) with (P < 0.001) found to be statistically significant.

Conclusion

This study observed that the destruction rate of the periodontal ligament was higher in diabetic teeth than in nondiabetic teeth, implying that patients with metabolic diseases such as type 2 diabetes influence the response of periodontal tissues to periodontitis and that hyperglycemia impacts the periodontal ligament either directly or indirectly.

Fibroblast Growth Factor 23: Potential Marker of Invisible Heart Damage in Diabetic Population

Two-dimensional speckle-tracking echocardiography (2DSTE) detects myocardial dysfunction despite a preserved left ventricular ejection fraction. Fibroblast growth factor 23 (FGF23) has become a promising biomarker of cardiovascular risk. This study aimed to determine whether FGF23 may be used as a marker of myocardial damage among patients with diabetes mellitus type 2 (T2DM) and no previous history of myocardial infarction. The study enrolled 71 patients with a median age of 70 years. Laboratory data were analyzed retrospectively. Serum FGF23 levels were determined using a sandwich enzyme-linked immunosorbent assay. All patients underwent conventional echocardiography and 2DSTE. Baseline characteristics indicated that the median time elapsed since diagnosis with T2DM was 19 years. All subjects were divided into two groups according to left ventricular diastolic function. Individuals with confirmed left ventricular diastolic dysfunction had significantly lower levels of estimated glomerular filtration rate and higher values of hemoglobin A1c. Global circumferential strain (GCS) was reduced in the majority of patients. Only an epicardial GCS correlated significantly with the FGF23 concentration in all patients. The study indicates that a cardiac strain is a reliable tool for a subtle myocardial damage assessment. It is possible that FGF23 may become an early diagnostic marker of myocardial damage in patients with T2DM.

Biochemical Markers of Bone Fragility in Patients with Diabetes. A Narrative Review by the IOF and the ECTS

CONTEXT

The risk of fragility fractures is increased in both type 1 and type 2 diabetes. Numerous biochemical markers reflecting bone and/or glucose metabolism have been evaluated in this context. This review summarizes current data on biochemical markers in relation to bone fragility and fracture risk in diabetes.

METHODS

Literature review by a group of experts from the International Osteoporosis Foundation (IOF) and European Calcified Tissue Society (ECTS) focusing on biochemical markers, diabetes, diabetes treatments and bone in adults.

RESULTS

Although bone resorption and bone formation markers are low and poorly predictive of fracture risk in diabetes, osteoporosis drugs seem to change bone turnover markers in diabetics similarly to non-diabetics, with similar reductions in fracture risk. Several other biochemical markers related to bone and glucose metabolism have been correlated with BMD and/or fracture risk in diabetes, including osteocyte-related markers such as sclerostin, HbA1c and advanced glycation end products (AGEs), inflammatory markers and adipokines, as well as IGF-1 and calciotropic hormones.

CONCLUSION

Several biochemical markers and hormonal levels related to bone and/or glucose metabolism have been associated with skeletal parameters in diabetes. Currently, only HbA1c levels seem to provide a reliable estimate of fracture risk, while bone turnover markers could be used to monitor the effects of anti-osteoporosis therapy.

Advanced glycation end products inhibit the osteogenic differentiation potential of adipose-derived stem cells in mice through autophagy

BACKGROUND

Diabetes mellitus (DM) microenvironment will accelerate the accumulation of Advanced glycation end products (AGEs), adipose-derived stem cells (ASCs) have poor osteogenesis in the DM microenvironment. Studies suggest autophagy plays a vital role in osteogenesis, but the mechanism of the altered osteogenic potential of ASCs has not been elucidated. Bone tissue engineering by ASCs is widely used in the treatment of bone defects with diabetic osteoporosis (DOP). Therefore, it is meaningful to explore the effect of AGEs on the osteogenic differentiation potential of ASCs and its potential mechanism for the repair of bone defects in DOP.

MATERIALS AND METHODS

ASCs in C57BL/6 mice were isolated, cultured, then treated with AGEs, subsequently, cell viability and proliferation were detected through Cell Counting Kit 8 assay. 3-Methyladenine (3-MA), an autophagic inhibitor used to inhibit autophagic levels. Rapamycin (Rapa), an autophagy activator that further activated autophagy levels by inhibiting mTOR.The osteogenesis and autophagy changes of ASCs were analyzed by flow cytometry, qPCR, western blot, immunofluorescence, alkaline phosphatase (ALP) and alizarin red staining.

RESULTS

AGEs reduced the autophagy level and osteogenic potential of ASCs. After 3-MA reduced autophagy, the osteogenic potential of ASCs also decreased. AGEs co-treatment with 3-MA, the levels of osteogenesis and autophagy reduced more significantly. When autophagy was activated by Rapa, it was found that it could rescue the reduced osteogenic potential of AGEs.

CONCLUSIONS

AGEs reduce the osteogenic differentiation potential of ASCs through autophagy, and may provide a reference for the treatment of bone defects with diabetes osteoporosis.

Longitudinal alterations in bone morphometry, mechanical integrity and composition in Type-2 diabetes in a Zucker diabetic fatty (ZDF) rat

Individuals with Type-2 Diabetes (T2D) have an increased risk of bone fracture, without a reduction in bone mineral density. It is hypothesised that the hyperglycaemic state caused by T2D forms an excess of Advanced Glycated End-products (AGEs) in the organic matrix of bone, which are thought to stiffen the collagen network and lead to impaired mechanical properties. However, the mechanisms are not well understood. This study aimed to investigate the geometrical, structural and material properties of diabetic cortical bone during the development and progression of T2D in ZDF (fa/fa) rats at 12-, 26- and 46-weeks of age. Longitudinal bone growth was impaired as early as 12-weeks of age and by 46-weeks bone size was significantly reduced in ZDF (fa/fa) rats versus controls (fa/+). Diabetic rats had significant structural deficits, such as bending rigidity, ultimate moment and energy-to-failure measured via three-point bend testing. Tissue material properties, measured by taking bone geometry into account, were altered as the disease progressed, with significant reductions in yield and ultimate strength for ZDF (fa/fa) rats at 46-weeks. FTIR analysis on cortical bone powder demonstrated that the tissue material deficits coincided with changes in tissue composition, in ZDF (fa/fa) rats with long-term diabetes having a reduced carbonate:phosphate ratio and increased acid phosphate content when compared to age-matched controls, indicative of an altered bone turnover process. AGE accumulation, measured via fluorescent assays, was higher in the skin of ZDF (fa/fa) rats with long-term T2D, bone AGEs did not differ between strains and neither AGEs correlated with bone strength. In conclusion, bone fragility in the diabetic ZDF (fa/fa) rats likely occurs through a multifactorial mechanism influenced initially by impaired bone growth and development and proceeding to an altered bone turnover process that reduces bone quality and impairs biomechanical properties as the disease progresses.

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

Background

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

Methods

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

Results

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

Conclusions

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

The translational potential of this article

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

Bone structure and composition in a hyperglycemic, obese, and leptin receptor-deficient rat: Microscale characterization of femur and calvarium

Metabolic abnormalities, such as diabetes mellitus and obesity, can impact bone quantity and/or bone quality. In this work, we characterize bone material properties, in terms of structure and composition, in a novel rat model with congenic leptin receptor (LepR) deficiency, severe obesity, and hyperglycemia (type 2 diabetes-like condition). Femurs and calvaria (parietal region) from 20-week-old male rats are examined to probe bones formed both by endochondral and intramembranous ossification. Compared to the healthy controls, the LepR-deficient animals display significant alterations in femur microarchitecture and in calvarium morphology when analyzed by micro-computed X-ray tomography (micro-CT). In particular, shorter femurs with reduced bone volume, combined with thinner parietal bones and shorter sagittal suture, point towards a delay in the skeletal development of the LepR-deficient rodents. On the other hand, LepR-deficient animals and healthy controls display analogous bone matrix composition, which is assessed in terms of tissue mineral density by micro-CT, degree of mineralization by quantitative backscattered electron imaging, and various metrics extrapolated from Raman hyperspectral images. Some specific microstructural features, i.e., mineralized cartilage islands in the femurs and hyper-mineralized areas in the parietal bones, also show comparable distribution and characteristics in both groups. Overall, the altered bone microarchitecture in the LepR-deficient animals indicates compromised bone quality, despite the normal bone matrix composition. The delayed development is also consistent with observations in humans with congenic Lep/LepR deficiency, making this animal model a suitable candidate for translational research.

Nε-(carboxymethyl)lysine promotes lipid uptake of macrophage via cluster of differentiation 36 and receptor for advanced glycation end products

BACKGROUND

Advanced glycation end products (AGEs) are diabetic metabolic toxic products that cannot be ignored. N^ε-(carboxymethyl)lysine (CML), a component of AGEs, could increase macrophage lipid uptake, promote foam cell formation, and thereby accelerate atherosclerosis. The receptor for AGEs (RAGE) and cluster of differentiation 36 (CD36) were the receptors of CML. However, it is still unknown whether RAGE and CD36 play key roles in CML-promoted lipid uptake.

AIM

Our study aimed to explore the role of RAGE and CD36 in CML-induced mac-rophage lipid uptake.

METHODS

In this study, we examined the effect of CML on lipid uptake by Raw264.7 macrophages. After adding 10 mmol/L CML, the lipid accumulation in macro-phages was confirmed by oil red O staining. Expression changes of CD36 and RAGE were detected with immunoblotting and quantitative real-time polymerase chain reaction. The interaction between CML with CD36 and RAGE was verified by immunoprecipitation. We synthesized a novel N-succinimidyl-4-¹⁸F-fluorobenzoate-CML radioactive probe. Radioactive receptor-ligand binding assays were performed to test the binding affinity between CML with CD36 and RAGE. The effects of blocking CD36 or RAGE on CML-promoting lipid uptake were also detected.

RESULTS

The study revealed that CML significantly promoted lipid uptake by macro-phages. Immunoprecipitation and radioactive receptor-ligand binding assays indicated that CML could specifically bind to both CD36 and RAGE. CML had a higher affinity for CD36 than RAGE. ARG82, ASN71, and THR70 were the potential interacting amino acids that CD36 binds to CML Anti-CD36 and anti-RAGE could block the uptake of CML by macrophages. The lipid uptake promotion effect of CML was significantly attenuated after blocking CD36 or RAGE.

CONCLUSION

Our results suggest that the binding of CML with CD36 and RAGE promotes macrophage lipid uptake.

Osteoporosis and cardiovascular disease: a review

BACKGROUND

Osteoporosis and cardiovascular disease are common diseases encountered globally, especially with advancing age. Osteoporosis occurs when there is a loss of bone mineral density leading to increased predisposition to fragility fracture. The conventional perception of osteoporosis is purely as a metabolic bone disease. However, there are mounting reports from recent studies that osteoporosis could be seen as a risk factor for cardiovascular disease just like other traditional risk factors such as hypertension, dyslipidaemia and diabetes. This is a paradigm shift with regards to the outlook of osteoporosis. Osteoporosis and cardiovascular disease have similar risk factors, including diabetes, smoking, excess alcohol, sedentary lifestyle, ageing and dyslipidaemia. This may partly explain the link between osteoporosis and cardiovascular disease. In addition, both osteoporosis and atherosclerosis, which underlies most cardiovascular disease, are both characterized by low grade chronic inflammation. Moreover, the processes involved in the calcification of atheroma are similar to what is seen in bone remodeling. Both processes also involve similar regulators such as osteoprotegerin and related proteins such as osteonectin, osteopontin and type 1 collagen are found in bone matrix and atheromatous plaques.

CONCLUSION

There is emerging evidence that individuals with osteoporosis are also at an increased risk of coronary artery disease and stroke even after controlling for other factors. The traditional risk factors for cardiovascular disease also predispose people to developing osteoporosis, suggesting that the same mechanism may be causing the two. Moreover, a number of anti-osteoporotic drugs have also been largely linked with cardiovascular disease. This calls for a change in the view of osteoporosis as a metabolic disease but as a cardio-metabolic disorder thereby emphasizing the need for intensified preventive strategies for the disease.

The Effects of Switching from Dipeptidyl Peptidase-4 Inhibitors to Glucagon-Like Peptide-1 Receptor Agonists on Bone Mineral Density in Diabetic Patients

PURPOSE

Diabetes increases the risk of fragility fractures. As a result, when choosing a diabetes treatment, whether the drug affects bone density should be taken into account. The goal of this study was to determine how switching from dipeptidyl peptidase-4 inhibitors (DPP-4i) to glucagon-like peptide-1 receptor agonists (GLP-1RA) influenced bone mineral density (BMD) in diabetic patients.

PATIENTS AND METHODS

In this retrospective cohort study, diabetic patients with osteoporosis or osteopenia who used DPP-4i but not anti-osteoporosis medications were divided into two groups: those who switched to GLP-1RA (n = 132) and those who did not (control group, n = 133). We compared changes in glycemic control and BMD with and without conversion from DPP-4i to GLP-1RA.

RESULTS

Prior to switching, there was no difference between the groups in terms of age, gender, glycosylated hemoglobin (HbA1c), or BMD. HbA1c was 8.7% in the participants (mean age 62.7 years, 17.4% female). Despite the fact that there was no difference in femoral neck BMD, the GLP-1RA group had a greater decrease in lumbar spine BMD (-0.028 g/cm² versus -0.019 g/cm², p = 0.041) than the control group. Furthermore, HbA1c levels in the GLP-1RA-treated group were considerably lower than in the control group (7.5% versus 8.0%, p = 0.027).

CONCLUSION

While switching to GLP-1RA improves glycemic control, it appears to have a less favorable effect on bone density than continuing DPP-4i. More research is needed, however, to determine whether diabetic patients with low bone density should be switched from DPP-4i to GLP-1RA.

Electroactive Biomaterials for Facilitating Bone Defect Repair under Pathological Conditions

Bone degeneration associated with various diseases is increasing due to rapid aging, sedentary lifestyles, and unhealthy diets. Living bone tissue has bioelectric properties critical to bone remodeling, and bone degeneration under various pathological conditions results in significant changes to these bioelectric properties. There is growing interest in utilizing biomimetic electroactive biomaterials that recapitulate the natural electrophysiological microenvironment of healthy bone tissue to promote bone repair. This review first summarizes the etiology of degenerative bone conditions associated with various diseases such as type II diabetes, osteoporosis, periodontitis, osteoarthritis, rheumatoid arthritis, osteomyelitis, and metastatic osteolysis. Next, the diverse array of natural and synthetic electroactive biomaterials with therapeutic potential are discussed. Putative mechanistic pathways by which electroactive biomaterials can mitigate bone degeneration are critically examined, including the enhancement of osteogenesis and angiogenesis, suppression of inflammation and osteoclastogenesis, as well as their anti-bacterial effects. Finally, the limited research on utilization of electroactive biomaterials in the treatment of bone degeneration associated with the aforementioned diseases are examined. Previous studies have mostly focused on using electroactive biomaterials to treat bone traumatic injuries. It is hoped that this review will encourage more research efforts on the use of electroactive biomaterials for treating degenerative bone conditions.

Diabetes Mellitus is Associated with Poor Bone Microarchitecture in Older Adults Residing in Long-Term Care Facilities

OBJECTIVES

Both diabetes mellitus (DM) and osteoporosis are very common in older adults who reside in long-term care (LTC) facilities. Nevertheless, few studies have examined the relationship between diabetes and bone quality in this population. The purpose of this study is to determine if bone mineral density (BMD) or trabecular bone score (TBS) is a better measure of bone quality and skeletal health, in LTC residents with and without a history of DM. Methodology. In this longitudinal cohort study, we examined baseline BMD (lumbar spine, total hip, and femoral neck), TBS, DM, and functional status in 511 LTC residents who were enrolled in two ongoing randomized placebo-controlled osteoporosis clinical trials.

RESULTS

On average, participants were older than 80 years and majority were prefrail or frail. Women with DM had greater lumbar spine BMD (1.106 vs 1.017, adjusted difference ± standard error = 0.084 ± 0.023 g/cm², p = 0.0003) and femoral neck BMD (0.695 vs 0.651, 0.027 ± 0.013 g/cm², p = 0.0463), but lesser lumbar spine TBS (1.211 vs 1.266, -0.036 ± 0.016, p = 0.0299) compared to women without DM. Total hip BMD was also higher based on descriptive statistics (0.780 vs 0.734, p = 0.6255) in diabetic women, although the difference was not statistically significant. Men had similar but attenuated findings.

CONCLUSIONS

Among LTC residents, those with DM have greater BMD but lower bone quality measured by TBS. TBS should be considered in assessing older patients with DM. However, further studies are required to confirm the findings with respect to fractures.

DXA-derived advanced hip analysis and the trabecular bone score in end-stage kidney disease secondary to type 1 diabetes

OBJECTIVE

Patients with end-stage kidney disease (ESKD) caused by type 1 diabetes mellitus (T1DM) have a heightened fracture risk. Bone mineral density (BMD) may predict fracture less accurately in ESKD than in patients with chronic kidney disease (CKD) stages 1-3b or the general population. Alternate, readily available imaging modalities are needed to improve ESKD fracture risk assessment. This study aimed to assess dual-energy X-ray absorptiometry (DXA)-derived BMD, the trabecular bone score (TBS) and advanced hip analysis parameters in patients with ESKD due to T1DM and to compare their results with those of patients with ESKD from other causes.

METHODS

We compared the DXA-derived TBS, hip cortical thickness (CT) and femoral neck (FN) buckling ratio (BR), an index of FN stability, of patients with T1DM and ESKD undergoing simultaneous pancreas kidney transplantation, patients with ESKD from other causes receiving kidney transplants and population reference ranges.

RESULTS

Of 227 patients with ESKD, 28% had T1DM and 65% were male. Compared with other ESKD patients, patients with T1DM were younger (42 ± 7.7 vs 51 ± 13.8 years), had shorter dialysis duration (24.4 ± 21 vs 42.6 ± 40 months), had higher HbA1c (7.9 ± 1.57% vs 5.4 ± 0.95%) and had lower BMI (25 ± 6 vs 27 ± 5 kg/m2). They had lower spine, hip and UD radius BMD Z-scores (all P ≤ 0.001), TBS (1.33 ± 0.12 vs 1.36 ± 0.12; P = 0.05), CT at the FN (P = 0.03), calcar (P = 0.006) and shaft (P < 0.001) and higher BR (10.1±7.1 vs 7.7±4; P = 0.006). All ESKD parameters were lower than population-based reference ranges (P < 0.001). Adjusting for age, sex, dialysis vintage and weight, prevalent vertebral fractures in patients with T1DM and ESKD were associated with higher BR (odds ratio (OR): 3.27 (95% CI: 1.19-8.92), P = 0.002) and lower FN CT (OR: 3.70 (95% CI: 1.13-12.50)).

CONCLUSION

Patients with ESKD and T1DM have reduced TBS, reduced CT and increased BR compared with other ESKD patients. Prospective study of these parameters is warranted to determine their utility in fracture risk prediction and management.

SIGNIFICANCE STATEMENT

Patients with ESKD and T1DM have an elevated fracture risk due to decreased bone strength. As an adjunct to BMD, evaluating dual-energy X-ray absorptiometry parameters that incorporate structural change may have greater value in patients with ESKD and T1DM than in the general population. In this study, patients with ESKD due to T1DM had lower BMD, lower trabecular bone scores, more severe loss of CT and higher BR than other patients with ESKD and people from the general population. Both lower CT and higher BR were associated with prevalent vertebral fractures in patients with T1DM and ESKD. Changes to these parameters should be evaluated for incident fracture prediction.

Advanced glycation end products and bone - How do we measure them and how do they correlate with bone mineral density and fractures? A systematic review and evaluation of precision of measures

The role of advanced glycation end products (AGEs) in bone fragility especially in diabetic bone disease is increasingly recognized and researched. As skeletal frailty in diabetes does not correlate to bone mineral density (BMD) in the same way as in postmenopausal osteoporosis, BMD may not be a suitable measure of bone quality in persons with diabetes. Abundant research exists upon the effect of AGEs on bone, and though full understanding of the mechanisms of actions does not yet exist, there is little doubt of the clinical relevance. Thus, the measurement of AGEs as well as possible treatment effects on AGEs have become issues of interest. The aim of this report is to summarize results of measurements of AGEs. It consists of a systematic review of the existing literature on AGE measurements in clinical research, an evaluation of the precision of skin autofluorescence (SAF) measurement by AGE Reader® (Diagnoptics), and a short commentary on treatment of osteoporosis in patients with and without diabetes with respects to AGEs. We conclude that various AGE measures correlate well, both fluorescent and non-fluorescent and in different tissues, and that more than one target of measure may be used. However, pentosidine has shown good correlation with both bone measures and fracture risk in existing literature and results on SAF as a surrogate measurement is promising as some corresponding associations with fracture risk and bone measures are reported. As SAF measurements performed with the AGE Reader® display high precision and allow for a totally noninvasive procedure, conducting AGE measurements using this method has great potential and further research of its applicability is encouraged.

Methylglyoxal - an advanced glycation end products (AGEs) precursor - Inhibits differentiation of human MSC-derived osteoblasts in vitro independently of receptor for AGEs (RAGE)

A major precursor of advanced glycation end-products (AGEs) - methylglyoxal (MG) - is a reactive carbonyl metabolite that originates from glycolytic pathways. MG formation and accumulation has been implicated in the pathogenesis of diabetes and age-related chronic musculoskeletal disorders. Human bone marrow-derived stromal cells (BMSCs) are multipotent cells that have the potential to differentiate into cells of mesenchymal origin including osteoblasts, but the role of MG on their differentiation is unclear. We therefore evaluated the effect of MG on proliferation and differentiation of BMSC-derived osteoblasts. Cells were treated with different concentrations of MG (600, 800 and 1000 μM). Cell viability was assessed using a Cell Counting Kit-8 assay. Alkaline phosphatase (ALP) activity and calcium deposition assays were performed to evaluate osteoblast differentiation and mineralization. Gene expression was measured using qRT-PCR, whereas AGE specific receptor (RAGE) and collagen 1 were examined by immunocytochemistry and Western blotting. RAGE knockdown was performed by transducing RAGE specific short hairpin RNAs (shRNAs) using lentivirus. During osteogenic differentiation, MG treatment resulted in reduction of cell viability (27.7 %), ALP activity (45.5 %) and mineralization (82.3 %) compared to untreated cells. MG significantly decreased expression of genes involved in osteogenic differentiation - RUNX2 (2.8 fold), ALPL (3.2 fold), MG detoxification through glyoxalase - GLO1 (3 fold) and collagen metabolism - COL1A1 (4.9 fold), COL1A2 (6.8 fold), LOX (5.4 fold) and PLOD1 (1.7 fold). MG significantly reduced expression of collagen 1 (53.3 %) and RAGE (43.1 %) at protein levels. Co-treatment with a MG scavenger - aminoguanidine - prevented all negative effects of MG. RAGE-specific knockdown during MG treatment did not reverse the effects on cell viability, osteogenic differentiation or collagen metabolism. In conclusion, MG treatment can negatively influence the collagen metabolism and differentiation of BMSCs-derived osteoblasts through a RAGE independent mechanism.

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

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

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

Background

This study aimed to explore whether S-Equol delays diabetes-induced osteoporosis and the molecular mechanisms underlying its therapeutic effects.

Materials and methods

Thirty-five male Sprague–Dawley rats were randomized into five groups. The diabetic osteoporosis (DOP) group and three S-Equol treatment groups were intraperitoneally injected with streptozotocin (STZ) to develop a DOP model. After the 12-week intervention, bone transformation indicators were detected using an enzyme-linked immunosorbent assay kit; bone mineral density (BMD) and bone microstructure were obtained using dual-energy X-ray absorptiometry and microCT; morphological changes in the bone tissue were investigated using HE staining; bone morphogenetic proteins were detected using immunohistochemical staining. ROS17/2.8 cells were cultured in vitro, and Cell Counting Kit-8 was used to test the protective effects of S-Equol in osteoblastic cells in a high-fat and high-glucose environment. Furthermore, the expression of osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL), estrogen receptor β(ERβ), phosphorylated Akt (pAKT)/protein kinase B (AKT), and osteocalcin (OC) in bone tissue and ROS17/2.8 cells was assessed using reverse transcription polymerase chain reaction (RT-PCR) and western blotting. To determine whether ERβ and phosphatidylinositol 3’ -kinase (PI3K)/AKT signaling pathways are involved in the process, LY294002 (PI3K signaling pathway inhibitor) and small interfering RNA targeting ERβ mRNA (si-ERβ) were used to verify the function of the ERβ-mediated PI3K/AKT pathway in this process.

Results

After the 12-week intervention, S-Equol enhanced BMD, improved bone microarchitecture in DOP rats (P < 0.05), and improved markers of bone metabolism (P < 0.05). In vitro, 10^–6 mmol/L S-Equol was selected to significantly protect osteoblasts from high- and high-glucose environments (P < 0.05). Gene expression of OPG, ERβ, pAKT/AKT, and OC was upregulated compared to the DOP group, and RANKL was downregulated compared to the DOP group (P < 0.05) both in bone tissue and osteoblastic cells. The promotion of OPG and pAKT/AKT is mediated by LY294002 and siERβ.

Conclusion

S-Equol binds to ERβ to regulate OPG/RANKL via the PI3K/AKT pathway and improve DOP. Our results demonstrate the potential role of S-Equol in the treatment of DOP by targeting ERβ. Thus, S-Equol may have the potential to be an adjuvant drug for treating DOP.

Advanced Glycation End Products, Bone Health, and Diabetes Mellitus

Advanced glycation end products (AGEs), the compounds resulting from the non-enzymatic glycosylation between reducing sugars and proteins, are derived from food or produced de novo. Over time, more and more endogenous and exogenous AGEs accumulate in various organs such as the liver, kidneys, muscle, and bone, threatening human health. Among these organs, bone is most widely reported. AGEs accumulating in bone reduce bone strength by participating in bone structure formation and breaking bone homeostasis by binding their receptors to alter the proliferation, differentiation, and apoptosis of cells involved in bone remodeling. In this review, we summarize the research about the effects of AGEs on bone health and highlight their associations with bone health in diabetes patients to provide some clues toward the discovery of new treatment and prevention strategies for bone-related diseases caused by AGEs.