Glycemic Control and Insulin Treatment Alter Fracture Risk in Older Men With Type 2 Diabetes Mellitus

Role of LRP5/6/GSK-3β/β-catenin in the differences in exenatide- and insulin-promoted T2D osteogenesis and osteomodulation

BACKGROUND AND PURPOSE

Insulin and exenatide are two hypoglycaemic agents that exhibit different osteogenic effects. This study compared the differences between exenatide and insulin in osseointegration in a rat model of Type 2 diabetes (T2D) and explored the mechanisms promoting osteogenesis in this model of T2D.

EXPERIMENTAL APPROACH

In vivo, micro-CT was used to detect differences in the peri-implant bone microstructure in vivo. Histology, dual-fluorescent labelling, immunofluorescence and immunohistochemistry were used to detect differences in tissue, cell and protein expression around the implants. In vitro, RT-PCR and western blotting were used to measure the expression of osteogenesis- and Wnt signalling-related genes and proteins in bone marrow mesenchymal stromal cells (BMSCs) from rats with T2D (TBMSCs) after PBS, insulin and exenatide treatment. RT-PCR was used to detect the expression of Wnt bypass cascade reactions under Wnt inactivation.

KEY RESULTS

Micro-CT and section staining showed exenatide extensively promoted peri-implant osseointegration. Both in vivo and in vitro experiments showed exenatide substantially increased the expression of osteogenesis-related and activated the LRP5/6/GSK-3β/β-catenin-related Wnt pathway. Furthermore, exenatide suppressed expression of Bmpr1a to inhibit lipogenesis and promoted expression of Btrc to suppress inflammation.

CONCLUSION AND IMPLICATIONS

Compared to insulin, exenatide significantly improved osteogenesis in T2D rats and TBMSCs. In addition to its dependence on LRP5/6/GSK-3β/β-catenin signalling for osteogenic differentiation, exenatide-mediated osteomodulation also involves inhibition of inflammation and adipogenesis by BMPR1A and β-TrCP, respectively.

The paradox of bone mineral density and fracture risk in type 2 diabetes

Fracture risk in type 2 diabetes (T2D) patients is paradoxically increased despite no decrease in areal bone mineral density (BMD). This phenomenon, known as the "diabetic bone paradox", has been attributed to various factors including alterations in bone microarchitecture and composition, hyperinsulinemia and hyperglycemia, advanced glycation end products (AGEs), and comorbidities associated with T2D. Zhao et al. recently investigated the relationship between T2D and fracture risk using both genetic and phenotypic datasets. Their findings suggest that genetically predicted T2D is associated with higher BMD and lower fracture risk, indicating that the bone paradox is not observed when confounding factors are controlled using Mendelian randomization (MR) analysis. However, in prospective phenotypic analysis, T2D remained associated with higher BMD and higher fracture risk, even after adjusting for confounding factors. Stratified analysis revealed that the bone paradox may disappear when T2D-related risk factors are eliminated. The study also highlighted the role of obesity in the relationship between T2D and fracture risk, with BMI mediating a significant portion of the protective effect. Overall, managing T2D-related risk factors may be crucial in preventing fracture risk in T2D patients.

Metformin-mediated effects on mesenchymal stem cells and mechanisms: proliferation, differentiation and aging

Mesenchymal stem cells (MSCs) are a type of pluripotent adult stem cell with strong self-renewal and multi-differentiation abilities. Their excellent biological traits, minimal immunogenicity, and abundant availability have made them the perfect seed cells for treating a wide range of diseases. After more than 60 years of clinical practice, metformin is currently one of the most commonly used hypoglycaemic drugs for type 2 diabetes in clinical practice. In addition, metformin has shown great potential in the treatment of various systemic diseases except for type 2 diabetes in recent years, and the mechanisms are involved with antioxidant stress, anti-inflammatory, and induced autophagy, etc. This article reviews the effects and the underlying mechanisms of metformin on the biological properties, including proliferation, multi-differentiation, and aging, of MSCs in vitro and in vivo with the aim of providing theoretical support for in-depth scientific research and clinical applications in MSCs-mediated disease treatment.

Bone metabolism in diabetes: a clinician's guide to understanding the bone-glucose interplay

Skeletal fragility is an increasingly recognised, but poorly understood, complication of both type 1 and type 2 diabetes. Fracture risk varies according to skeletal site and diabetes-related characteristics. Post-fracture outcomes, including mortality risk, are worse in those with diabetes, placing these people at significant risk. Each fracture therefore represents a sentinel event that warrants targeted management. However, diabetes is a very heterogeneous condition with complex interactions between multiple co-existing, and highly correlated, factors that preclude a clear assessment of the independent clinical markers and pathophysiological drivers for diabetic osteopathy. Additionally, fracture risk calculators and routinely used clinical bone measurements generally underestimate fracture risk in people with diabetes. In the absence of dedicated prospective studies including detailed bone and metabolic characteristics, optimal management centres around selecting treatments that minimise skeletal and metabolic harm. This review summarises the clinical landscape of diabetic osteopathy and outlines the interplay between metabolic and skeletal health. The underlying pathophysiology of skeletal fragility in diabetes and a rationale for considering a diabetes-based paradigm in assessing and managing diabetic bone disease will be discussed.

Interplay between diabetes mellitus and periodontal/pulpal-periapical diseases

This longevity of life expectancy has indirectly led to an increase in the number of chronic diseases such as periodontitis, apical periodontitis (AP), and diabetes mellitus (DM) in the aging society, thus affecting people's quality of life. There is an interaction between periodontitis/AP and DM with a two-way relationship. Although type 1 and 2 diabetes (T1DM, T2DM) have different etiologies, glycemic control may affect the infection, inflammation and tissue healing of periodontitis and AP. Non-surgical periodontal treatment may influence the glycemic control as shown by decrease of HbA1c level in T2DM patient. However, the effect of periodontal treatment on glycemic control in T1DM and root canal treatment/apical surgery on T1DM and T2DM patients awaits investigation. DM may affect the periodontal and periapical tissues possibly via altered oral microbiota, impairment of neutrophils' activity and host immune responses and cytokine production, induction of oxidative stress etc. While periodontitis associated systemic inflammation and hyperlipidemia is suggested to contribute to the control of T2DM, more intricate studies are necessary to clarify the detailed mechanisms. The interactions between DM (T1DM and T2DM) and periodontitis and AP are therefore reviewed to provide a basis for the treatment of subsequent patients with pulpal/periodontal disease and diabetes. A two-pronged approach of medical and dental treatment is needed for the management of these patients, with emphasis on blood glucose control and improving oral hygiene and periodontal maintenance care, to ensure the best treatment outcome.

A Factor-Free Hydrogel with ROS Scavenging and Responsive Degradation for Enhanced Diabetic Bone Healing

In view of the increased levels of reactive oxygen species (ROS) that disturb the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), the repair of diabetic bone defects remains a great challenge. Herein, a factor-free hydrogel is reported with ROS scavenging and responsive degradation properties for enhanced diabetic bone healing. These hydrogels contain ROS-cleavable thioketal (TK) linkers and ultraviolet (UV)-responsive norbornene (NB) groups conjugated with 8-arm PEG macromers, which are formed via UV crosslinking-mediated gelation. Upon reacting with high levels of ROS in the bone defect microenvironment, ROS-cleavable TK linkers are destroyed, allowing the responsive degradation of hydrogels, which promotes the migration of BMSCs. Moreover, ROS levels are reduced through hydrogel-mediated ROS scavenging to reverse BMSC differentiation from adipogenic to osteogenic phenotype. As such, a favorable microenvironment is created after simultaneous ROS scavenging and hydrogel degradation, leading to the effective repair of bone defects in diabetic mouse models, even without the addition of growth factors. Thus, this study presents a responsive hydrogel platform that regulates ROS scavenging and stromal degradation in bone engineering.

Bone Health in Patients With Type 2 Diabetes

The association between type 2 diabetes mellitus (T2DM) and skeletal fragility is complex, with effects on bone at the cellular, molecular, and biomechanical levels. As a result, people with T2DM, compared to those without, are at increased risk of fracture, despite often having preserved bone mineral density (BMD) on dual-energy x-ray absorptiometry (DXA). Maladaptive skeletal loading and changes in bone architecture (particularly cortical porosity and low cortical volumes, the hallmark of diabetic osteopathy) are not apparent on routine DXA. Alternative imaging modalities, including quantitative computed tomography and trabecular bone score, allow for noninvasive visualization of cortical and trabecular compartments and may be useful in identifying those at risk for fractures. Current fracture risk calculators underestimate fracture risk in T2DM, partly due to their reliance on BMD. As a result, individuals with T2DM, who are at high risk of fracture, may be overlooked for commencement of osteoporosis therapy. Rather, management of skeletal health in T2DM should include consideration of treatment initiation at lower BMD thresholds, the use of adjusted fracture risk calculators, and consideration of metabolic and nonskeletal risk factors. Antidiabetic medications have differing effects on the skeleton and treatment choice should consider the bone impacts in those at risk for fracture. T2DM poses a unique challenge when it comes to assessing bone health and fracture risk. This article discusses the clinical burden and presentation of skeletal disease in T2DM. Two clinical cases are presented to illustrate a clinical approach in assessing and managing fracture risk in these patients.

Association of cardiovascular disease prevalence with BMD and fracture in men with T2DM

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) are predisposed to cardiovascular disease (CVD). Bone mineral density (BMD) is linked to CVD, but most studies focused on women. Our analysis aims to explore the association of BMD and fracture with the prevalence of CVD in men with T2DM.

METHODS

In this retrospective cross-sectional study, 856 men with T2DM were enrolled. BMDs at the lumbar spine (L2-4), femoral neck (FN), and total hip (TH) were measured by dual-energy X-ray absorptiometry (DXA). The CVD outcome was determined as the sum of the following conditions: congestive heart failure, coronary heart disease, angina pectoris, myocardial infarction, the requirement for coronary artery revascularization, and stroke. The relationship between BMDs and CVD was investigated by restricted cubic spline curves and logistic regression models.

RESULTS

A total of 163 (19.0%) patients developed CVD. The restricted cubic spline curve revealed a linear and negative association between FN-BMD, TH-BMD, and CVD. After full adjustments for confounding covariates, the odds ratios were 1.34 (95% confidence interval [CI] [1.11-1.61], p < .05), 1.3 (95% CI [1.05-1.60], p < .05), and 1.26 (95% CI [1.02-1.55], p < .05) for each 1-SD decrease in BMDs of L2-4, FN and TH, respectively. T-scores of < -1 for BMD of L2-4 and FN were independently associated with CVD (p < .05). Subgroup analyses further supported our findings.

CONCLUSIONS

The prevalence of CVD was inversely correlated with BMD levels in men with T2DM, particularly at the FN. We hypothesized that monitoring FN-BMD and early intervention would help reduce CVD risk in men with T2DM, especially those with hypertension.

Obesity and Skeletal Fragility

Skeletal fracture has recently emerged as a complication of obesity. Given the normal or better than normal bone mineral density (BMD), the skeletal fragility of these patients appears to be a problem of bone quality rather than quantity. Type 2 diabetes mellitus (T2DM), the incidence of which increases with increasing body mass index, is also associated with an increased risk for fractures despite a normal or high BMD. With the additional bone pathology from diabetes itself, patients with both obesity and T2DM could have a worse skeletal profile. Clinically, however, there are no available methods for identifying those who are at higher risk for fractures or preventing fractures in this subgroup of patients. Weight loss, which is the cornerstone in the management of obesity (with or without T2DM), is also associated with an increased risk of bone loss. This review of the literature will focus on the skeletal manifestations associated with obesity, its interrelationship with the bone defects associated with T2DM, and the available approach to the bone health of patients suffering from obesity.

A simple fragility fracture risk score for type 2 diabetes patients: a derivation, validation, comparison, and risk stratification study

OBJECTIVES

The aims of this study were to develop and validate 2 simple scores for stratification of the risks of (1) any fragility (AF) and (2) major osteoporotic fracture (MOF) in type 2 diabetes (T2D) patients; we also compared the performance of these scores with that of the Fracture Risk Assessment Tool (FRAX) and its adjustments.

DESIGN AND METHODS

In this longitudinal cohort study, 1855 patients with T2D were enrolled from January 2015 to August 2019. Cox proportional hazard regression was used to model the 5-year risk of AF and MOF. These scores were internally validated using a bootstrap resampling method of 1000.

RESULTS

During a median follow-up of 5 years, 119 (6.42%) cases of AF and 92 (4.96%) cases of MOFs were identified. Both the concordance index (C-index) and calibration plots indicated improved identification performance using the newly established scores. Furthermore, these scores also showed improved outcomes regarding the decision curve analysis (DCA) and area under the curve (AUC) compared to the widely used FRAX and its derivatives. More importantly, these scores successfully separated T2D patients into risk groups according to significant differences in fracture incidence.

CONCLUSIONS

These novel scores enable simple and reliable fracture risk stratification in T2D patients. Future work is needed to validate these findings in external cohort(s).

The complex pathophysiology of bone fragility in obesity and type 2 diabetes mellitus: therapeutic targets to promote osteogenesis

Fractures associated with Type2 diabetes (T2DM) are major public health concerns in an increasingly obese and aging population. Patients with obesity or T2DM have normal or better than normal bone mineral density but at an increased risk for fractures. Hence it is crucial to understand the pathophysiology and mechanism of how T2DM and obesity result in altered bone physiology leading to increased fracture risk. Although enhanced osteoclast mediated bone resorption has been reported for these patients, the most notable observation among patients with T2DM is the reduction in bone formation from mostly dysfunction in osteoblast differentiation and survival. Studies have shown that obesity and T2DM are associated with increased adipogenesis which is most likely at the expense of reduced osteogenesis and myogenesis considering that adipocytes, osteoblasts, and myoblasts originate from the same progenitor cells. Furthermore, emerging data point to an inter-relationship between bone and metabolic homeostasis suggesting that these physiologic processes could be under the control of common regulatory pathways. Thus, this review aims to explore the complex mechanisms involved in lineage differentiation and their effect on bone pathophysiology in patients with obesity and T2DM along with an examination of potential novel pharmacological targets or a re-evaluation of existing drugs to improve bone homeostasis.

Factors associated with fragility fractures in type 2 diabetes: An analysis of the randomised controlled Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study

AIMS

Fracture risk is elevated in some type 2 diabetes patients. Bone fragility may be associated with more clinically severe type 2 diabetes, although prospective studies are lacking. It is unknown which diabetes-related characteristics are independently associated with fracture risk. In this post-hoc analysis of fracture data from the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) trial (ISRCTN#64783481), we hypothesised that diabetic microvascular complications are associated with bone fragility.

MATERIALS AND METHODS

The FIELD trial randomly assigned 9795 type 2 diabetes participants (aged 50-75 years) to receive oral co-micronised fenofibrate 200 mg (n = 4895) or placebo (n = 4900) daily for a median of 5 years. We used Cox proportional hazards models to identify baseline sex-specific diabetes-related parameters independently associated with incident fractures.

RESULTS

Over 49,470 person-years, 137/6138 men experienced 141 fractures and 143/3657 women experienced 145 fractures; incidence rates for the first fracture of 4∙4 (95% CI 3∙8-5∙2) and 7∙7 per 1000 person-years (95% CI 6∙5-9∙1), respectively. Fenofibrate had no effect on fracture outcomes. In men, baseline macrovascular disease (HR 1∙52, 95% CI 1∙05-2∙21, p = 0∙03), insulin use (HR 1∙62, HR 1∙03-2∙55, p = 0∙03), and HDL-cholesterol (HR 2∙20, 95% CI 1∙11-4∙36, p = 0∙02) were independently associated with fracture. In women, independent risk factors included baseline peripheral neuropathy (HR 2∙04, 95% CI 1∙16-3∙59, p = 0∙01) and insulin use (HR 1∙55, 95% CI 1∙02-2∙33, p = 0∙04).

CONCLUSIONS

Insulin use and sex-specific complications (in men, macrovascular disease; in women, neuropathy) are independently associated with fragility fractures in adults with type 2 diabetes.

The use of metformin, sulfonylurea compounds and insulin and the risk of hip fractures in diabetic patients: a systematic review and meta-analysis of observational studies

BACKGROUND

Hip fracture is a major health problem that occurs more often in the elderly, especially in diabetic patients. Some studies have been conducted regarding the effect of anti- diabetic drugs on fractures. But so far, no meta-analysis study has been conducted to investigate the effect of diabetic drugs on hip fractures. Therefore, this study investigated the relationship between anti-diabetic drugs (Metformin, Sulfonylurea, and insulin) with hip fractures.

METHODS

In this systematic review and meta analysis study, PubMed, Scopus, Google Scholar, and Web of Science databases were searched with specific keywords to find relevant studies. Two researchers included related studies after screening based on the title and full text. Cochran's Q and I2 tests were used to assess heterogeneity between studies. Publication bias between studies was evaluated for each drug using Egger's test. A 95% confidence interval was used for effect size significance. Overall, 49 studies, including 6,631,297 participants, were reviewed.

RESULTS

The results showed that metformin significantly reduced the risk of hip fracture (HR: 0.833, 95% CI: 0.759, 0.914, P:0.001). Consumption of sulfonylurea compounds was significantly associated with an increased risk of hip fracture. (HR: 1.175, 95% CI:1.068,1.293, P:0.001), The risk of hip fracture in patients receiving insulin was significantly higher than in diabetic patients who did not receive insulin. (HR:1.366, 95% CI:1.226,1.522, P:0.001).

CONCLUSION

The results of this study showed that taking metformin reduces the risk of hip fracture, and insulin and Sulfonylurea increase the risk of hip fracture.

A Novel Anti-Osteoporosis Mechanism of VK2: Interfering with Ferroptosis via AMPK/SIRT1 Pathway in Type 2 Diabetic Osteoporosis

Type 2 diabetic osteoporosis (T2DOP) is a chronic bone metabolic disease. Compared with traditional menopausal osteoporosis, the long-term high glucose (HG) microenvironment increases patients' risk of fracture and osteonecrosis. We were accumulating evidence that implicated ferroptosis as a pivotal mechanism of glucolipotoxicity-mediated death of osteocytes and osteoblast, a novel form of programmed cell death resulting from uncontrolled lipid peroxidation depending on iron. Vitamin K2 (VK2), a fat-soluble vitamin, is clinically applied to prevent osteoporosis and improve coagulation. This study aimed to clarify the role and mechanism of VK2 in HG-mediated ferroptosis. We established the mouse T2DOP model by intraperitoneal injection of streptozotocin solution and a high-fat and high-sugar diet. We also cultured bone marrow mesenchymal stem cells (BMSCs) in HG to simulate the diabetic environment in vitro. Based on our data, VK2 inhibited HG-mediated bone loss and ferroptosis, the latter manifested by decreased levels of mitochondrial reactive oxygen species, lipid peroxidation, and malondialdehyde and increased glutathione in vitro. In addition, VK2 treatment was capable of restoring bone mass and strengthening the expression of SIRT1, GPX4, and osteogenic markers in the distal femurs. As for further mechanism exploration, we found that VK2 could activate AMPK/SIRT1 signaling, and knockdown of SIRT1 by siRNA prevented the VK2-mediated positive effect in HG-cultured BMSCs. Summarily, VK2 could ameliorate T2DOP through the activation of the AMPK/SIRT1 signaling pathway to inhibit ferroptosis.

Contributors to impaired bone health in type 2 diabetes

Type 2 diabetes (T2D) is associated with numerous complications, including increased risk of fragility fractures, despite seemingly protective factors [e.g., normal bone mineral density and increased body mass index(BMI)]. However, fracture risk in T2D is underestimated by current fracture risk calculators. Importantly, post-fracture mortality is worse in T2D following any fracture, highlighting the importance of identifying high-risk patients that may benefit from targeted management. Several diabetes-related factors are associated with increased fracture risk, including exogenous insulin therapy, vascular complications, and poor glycaemic control, although detailed comprehensive studies to identify the independent contributions of these factors are lacking. The underlying pathophysiological mechanisms are complex and multifactorial, with different factors contributing during the course of T2D disease. These include obesity, hyperinsulinaemia, hyperglycaemia, accumulation of advanced glycation end products, and vascular supply affecting bone-cell function and survival and bone-matrix composition. This review summarises the current understanding of the contributors to impaired bone health in T2D, and proposes an updated approach to managing these patients.

A narrative review of diabetic bone disease: Characteristics, pathogenesis, and treatment

Recently, the increasing prevalence of diabetes mellitus has made it a major chronic illness which poses a substantial threat to human health. The prevalence of osteoporosis among patients with diabetes mellitus has grown considerably. Diabetic bone disease is a secondary osteoporosis induced by diabetes mellitus. Patients with diabetic bone disease exhibit variable degrees of bone loss, low bone mineral density, bone microarchitecture degradation, and increased bone fragility with continued diabetes mellitus, increasing their risk of fracture and impairing their ability to heal after fractures. At present, there is extensive research interest in diabetic bone disease and many significant outcomes have been reported. However, there are no comprehensive review is reported. This review elaborates on diabetic bone disease in the aspects of characteristics, pathogenesis, and treatment.

Risk of Fracture With Dipeptidyl Peptidase-4 Inhibitors, Glucagon-like Peptide-1 Receptor Agonists, or Sodium-Glucose Cotransporter-2 Inhibitors in Patients With Type 2 Diabetes Mellitus: A Systematic Review and Network Meta-analysis Combining 177 Randomized Controlled Trials With a Median Follow-Up of 26 weeks

Aim: This study aims to investigate the association between the use of dipeptidyl peptidase-4 inhibitors (DPP-4i), glucagon-like peptide-1 receptor agonists (GLP-1 RAs), or sodium-glucose cotransporter-2 inhibitors (SGLT-2i) and the risk of fracture among patients with type 2 diabetes mellitus. Methods: Medline, Embase, Cochrane Library, and Clinical-Trials.gov databases were searched for randomized controlled trials (RCTs). Network meta-analysis was performed for total fracture and a series of secondary outcomes. Results: A total of 177 RCTs (n = 165,081) involving the risk of fracture were identified (a median follow-up of 26 weeks). DPP-4i, GLP-1 RAs, and SGLT-2i did not increase total fracture risk compared with insulin (odds ratio: 0.86, 95% confidence interval: 0.39-1.90; 1.05, 0.54-2.04; 0.88, and 0.39-1.97, respectively), metformin (1.41, 0.48-4.19; 1.72, 0.55-5.38; 1.44, 0.48-4.30), sulfonylureas (0.77, 0.50-1.20; 0.94, 0.55-1.62; 0.79, 0.48-1.31), thiazolidinediones (0.82, 0.27-2.44; 1.00, 0.32-3.10; 0.83, 0.27-2.57), α-glucosidase inhibitor (4.92, 0.23-103.83; 5.99, 0.28-130.37; 5.01, 0.23-107.48), and placebo (1.04, 0.84-1.29; 1.27, 0.88-1.83; 1.06, 0.81-1.39). Conclusions: The use of DPP-4i, GLP-1 RAs, or SGLT-2i is unlikely to increase the risk of fracture among type 2 diabetes mellitus patients.

Unmasking Fracture Risk in Type 2 Diabetes: The Association of Longitudinal Glycemic Hemoglobin Level and Medications

CONTEXT

Fracture risk is underestimated in people with type 2 diabetes (T2D).

OBJECTIVE

To investigate the longitudinal relationship of glycated hemoglobin (HbA1c) and common medications on fracture risk in people with T2D.

METHODS

This retrospective population-based cohort study was conducted using de-identified claims and electronic health record data obtained from the OptumLabs Data Warehouse for the period January 1, 2007, to September 30, 2015. For each individual, the study was conducted within a 2-year HbA1c observation period and a 2-year fracture follow-up period. A cohort of 157 439 individuals with T2D [age ≥ 55 years with mean HbA1c value ≥ 6%] were selected from 4 018 250 US Medicare Advantage/Commercial enrollees with a T2D diagnosis. All fractures and fragility fractures were measured.

RESULTS

With covariates adjusted, poor glycemic control in T2D individuals was associated with an 29% increase of all fracture risk, compared with T2D individuals who had adequate glycemic control (HR: 1.29; 95% CI, 1.22-1.36). Treatment with metformin (HR: 0.88; 95% CI, 0.85-0.92) and DPP4 inhibitors (HR: 0.93; 95% CI, 0.88-0.98) was associated with a reduced all fracture risk, while insulin (HR: 1.26; 95% CI, 1.21-1.32), thiazolidinediones (HR: 1.23; 95% CI, 1.18-1.29), and meglitinides (HR: 1.12; 95% CI, 1.00-1.26) were associated with an increased all fracture risk (All P value < 0.05). Bisphosphonates were associated similarly with increased fracture risk in the T2D and nondiabetic groups.

CONCLUSION

Longitudinal 2-year HbA1c is independently associated with elevated all fracture risk in T2D individuals during a 2-year follow-up period. Metformin and DPP4 inhibitors can be used for management of T2D fracture risk.

Regulation of bone mass in endocrine diseases including diabetes

Hormonal regulation plays a key role in determining bone mass in humans. Both skeletal growth and bone loss in health and disease is critically controlled by endocrine factors and low bone mass is a feature of both excess and deficiency of a broad range of hormones. This article explores the impact of diabetes and thyroid, parathyroid, sex steroid and growth hormone disorders on bone mass and fracture risk. Evidence for current management strategies is provided along with suggested practice points and gaps in knowledge for future research.

Vascular Complications in Individuals with Type 2 Diabetes Mellitus Additionally Increase the Risk of Femoral Neck Fractures Due to Deteriorated Trabecular Microarchitecture

Individuals with diabetes mellitus type 2 (T2DM) have an increased risk of hip fracture, especially if vascular complications are present. However, microstructural origins of increased bone fragility in T2DM are still controversial. DXA measurement of the contralateral hip and three-dimensional microCT analyses of femoral neck trabecular microarchitecture were performed in 32 individuals (26 women and 6 men, 78 ± 7 years). The specimens were divided to two groups: T2DM individuals with hip fracture (DMFx, n = 18) and healthy controls (CTL, n = 14). DMFx group consisted of individuals with vascular complications (DMFx_VD, n = 8) and those without vascular complications (DMFx_NVD, n = 10). T-score was significantly lower in DMFx_VD and DMFx_NVD than in controls (p < 0.001). BV/TV, Tb.N, Tb.Sp, SMI, and FD varied among DMFx_NVD, DMFx_VD, and CTL groups (p = 0.023, p = 0.004, p = 0.008, p = 0.001, p = 0.007, respectively). Specifically, BV/TV of DMFx_VD was significantly lower than that of DMFx_NVD group (p = 0.020); DMFx_NVD group had higher Tb.N and lower Tb.Sp compared with DMFx_VD (p = 0.006, p = 0.012, respectively) and CTL (p = 0.026, p = 0.035, respectively). DMFx group and healthy controls showed similar BV/TV, Tb.Th, Tb.N, Tb.Sp, Conn.D, DA, and FD (p = 0.771, p = 0.503, p = 0.285, p = 0.266, p = 0.208, p = 0.235, p = 0.688, respectively), while SMI was significantly higher in controls (p = 0.005). Two distinct phenotypes of bone fragility were identified in T2DM patients: patients with vascular complications showed impaired trabecular microarchitecture, whereas bone fragility in the group without vascular complications was independent on trabecular microarchitecture pattern. Such heterogeneity among T2DM patients may explain contradicting literature data and may set a basis for further studies to evaluate fracture risk related to T2DM.

Differential risk of fracture attributable to type 2 diabetes mellitus according to skeletal site

BACKGROUND

Impaired bone quality, especially related to accumulation of advanced glycation end-products (AGEs) and higher incidence of falls contribute substantially to a higher risk of fracture associated with type 2 diabetes mellitus (T2DM). These factors may predispose to fractures more at skeletal sites where impaired bone toughness and falls play a larger pathogenic role (such as hip fractures) compared to skeletal sites where they are less important (such as vertebral fractures).

OBJECTIVE

To determine if the associations of T2DM with prevalent and incident vertebral fractures are as strong as they are for hip and other non-vertebral fractures.

METHODS

Amongst 80,238 individuals in the Manitoba Bone Density Program database (mean [SD] age 64.4 [11.1] years, 89.8% female, 8676 with diagnosed T2DM) with a baseline BMD test (1996-2016), we estimated hazard ratios (HRs) for incident clinical fracture at different skeletal sites in those with compared to those without T2DM using Cox proportional hazards models over a mean (SD) 9.0 (5.0) year follow-up period. We also estimated odds ratios for prevalent vertebral fracture on VFA images amongst 9594 individuals (mean [SD] 76 [6.8] years, 1185 with T2DM diagnosis at time of DXA-VFA) and for prior clinical fractures at different skeletal sites using logistic regression models.

RESULTS

After multivariable adjustment, T2DM was associated with incident hip (HR 1.63, 95% CI 1.44 to 1.85) and proximal humerus fractures (HR 1.59, 95% CI 1.39 to 1.83), but was not associated with incident forearm fracture (HR 1.00, 95% CI 0.86 to 1.17) and only weakly with incident clinical vertebral fracture (HR 1.16, 95% CI 1.01 to 1.33). Similarly, T2DM was associated with prior hip (OR 1.78, 95% CI 1.21 to 2.61) and prior proximal humerus fracture (OR 1.31, 95% CI 1.02 to 1.68) but not with prior forearm (OR 0.89, 95% CI 0.74 to 1.06) or prevalent vertebral fracture on VFA images (OR 0.91, 95% CI 0.77 to 1.08).

CONCLUSION

T2DM is a stronger risk factor for hip and proximal humerus fractures than for vertebral and wrist fractures. Further research is warranted to determine if the known differences in falls and/or bone quality between T2DM and age-related osteoporosis account for these differential associations.

The pathophysiology of osteoporosis in obesity and type 2 diabetes in aging women and men: The mechanisms and roles of increased bone marrow adiposity

Osteoporosis is defined as a systemic skeletal disease characterized by decreased bone mass and micro-architectural deterioration leading to increased fracture risk. Osteoporosis incidence increases with age in both post-menopausal women and aging men. Among other important contributing factors to bone fragility observed in osteoporosis, that also affect the elderly population, are metabolic disturbances observed in obesity and Type 2 Diabetes (T2D). These metabolic complications are associated with impaired bone homeostasis and a higher fracture risk. Expansion of the Bone Marrow Adipose Tissue (BMAT), at the expense of decreased bone formation, is thought to be one of the key pathogenic mechanisms underlying osteoporosis and bone fragility in obesity and T2D. Our review provides a summary of mechanisms behind increased Bone Marrow Adiposity (BMA) during aging and highlights the pre-clinical and clinical studies connecting obesity and T2D, to BMA and bone fragility in aging osteoporotic women and men.

Effect of Newer Long-Acting Insulins on Hypoglycemia and Fracture Risk Among People with Diabetes: A Systematic Review

PURPOSE OF REVIEW

To investigate the effect of newer long-acting insulins on the risk of hypoglycemic episodes and fractures in people with diabetes.

RECENT FINDINGS

Hypoglycemic episodes are the critical limiting factor in glycemic management due to a deteriorating effect on quality of life. Hypoglycemia may in severe cases lead to unconsciousness and thus fractures. Newer long-acting insulins may result in more stable blood glucose levels, less hypoglycemic episodes, and reduced risk of fractures. Use of insulin increases risk of hypoglycemic episodes, and hypoglycemic episodes increase risk of fractures plausible due to falls. Newer ultra-long-acting insulins reduce risk of hypoglycemic episodes compared to older alternatives, and they are thus promising for reducing fracture risk. However, more studies are needed to determine whether these new insulins reduce risk of fractures.

Post-hip fracture rehabilitation outcomes of diabetic and non-diabetic elderly patients

BACKGROUND

Although patients with diabetes mellitus (DM) are at higher risk of hip fracture, data regarding the effect of DM on rehabilitation outcomes are limited.

METHODS

A retrospective single-centre study was conducted comparing elderly diabetic and non-diabetic patients with recent hip fracture, admitted to geriatric rehabilitation, 2014-2019. The functional independence measure (FIM) was used to assess physical and cognitive function. Delta-FIM was calculated by subtracting admission FIM from discharge FIM. One-year mortality, hospitalizations and fractures were assessed.

RESULTS

Six-hundred-thirty elderly patients, post-hip fracture were included, mean age 83 ± 7 years, 70.5% (444) women. Among them, 193 (30.6%) had type 2 DM, HbA1c 6.6 ± 1.25%. They were younger (81.4 vs. 84.3 years, p < .01) and had more co-morbidities including hypertension, chronic kidney disease, ischaemic heart disease and cerebrovascular disease. Baseline cognitive and motor scores were similar between groups. Delta motor-FIM was similar between diabetics and non-diabetics (15.56 ± 8.95 and 14.78 ± 8.79, respectively, p = .35). Multivariate regression analysis showed motor-FIM improvement was associated with higher BMI, male sex, and younger age, but not with DM. Cognitive FIM did not change significantly during rehabilitation in either group. Similar rates of patients were discharged to nursing care facilities. There was no difference in 1-year hospitalization or fracture rates. One-year, all-cause mortality was higher among diabetic patients (10.9 vs. 6.6%, respectively, p = .07). After adjusting for covariates, DM was associated with higher mortality risk (odds ratio = 2.78, 95% CI [1.28, 6.04], p = .01).

CONCLUSIONS

Patients with well-controlled DM have similar post-hip fracture rehabilitation potential compared with non-diabetics, despite more co-morbidities. These results support resource allocation for post-hip fracture rehabilitation among patients with DM. The higher 1-year all-cause mortality in patients with DM reinforces the need for close follow-up and control of co-morbidities in this population.

Diabetes is associated with a lower minimum moment of inertia among older women: An analysis of 3D reconstructions of clinical CT scans

Hip fractures are a significant burden on the aging population, often resulting in reduced mobility, loss of independence, and elevated risk of mortality. While fracture risk is generally inversely related to bone mineral density (BMD), people with diabetes suffer a higher fracture rate despite having a higher BMD. To better understand the connection between diabetes and fracture risk, we developed a method to measure the minimum moment of inertia (mMOI; a geometric factor associated with fracture risk) from clinical CT scans of the pelvis. Since hip fractures are more prevalent in women, we focused on females in this study. We hypothesized that females with diabetes would have a lower mMOI along the femoral neck than those without diabetes, indicative of a higher fracture risk. Three-dimensional models of each hip were created from clinical CT scans of 40 older women (27 with diabetes: 10 fracture/17 non-fractured; 13 without diabetes: non-fractured controls). The mMOI of each hip (n = 80) was reported as the average from three trials. People with diabetes had an 18% lower mMOI as compared to those without diabetes after adjusting for age and BMI (p = 0.02). No differences in the mMOIs between the fractured and contralateral hips in the diabetic group were observed (p = 0.78). Similarly, no differences were observed between the fractured and non-fractured hips of people with diabetes (p = 0.29) when accounting for age and BMI. This suggests structural differences in the hips of individuals with diabetes (measured by the mMOI) may be associated with their elevated fracture risk.

Low glycaemic state increases risk of frailty and functional decline in older people with type 2 diabetes mellitus - Evidence from a systematic review

AIMS

To explore risk of frailty and functional decline associated with low glycaemia in older people with type 2 diabetes.

METHODS

Systematic review.

RESULTS

11 studies included. Six studies investigated risk of frailty or physical decline with hypoglycaemia. Hypoglycaemia increased risk of incident frailty (HR 1.60, 95% CI 1.14 to 2.42) in one study and risk of fractures in four studies (2.24, 1.56 to 3.21, 1.24, 1.13 to 1.37, 1.94, 1.67 to 2.24 and 1.71, 1.35 to 2.16 respectively). In sixth study, hypoglycaemia associated with dependency (P < 0.001). Five studies explored association of low blood glucose/HbA1c with frailty. One study showed that mean blood glucose decreased with increasing frailty (p = 0.003). Two studies reported that HbA1c inversely correlated with clinical frailty scale (r = -0.31, p < 0.01) and HbA1c < 6.9% increased risk of frailty (HR, 1.41 95% CI 1.12 to 1.78) respectively. Last two studies showed that HbA1c < 6.5% associated with risk of any fracture (HR 1.08, 95% CI 1.06 to 1.11) and HbA1c < 6.0% associated with increased risk of care need (3.45, 1.02 to 11.6) respectively.

CONCLUSIONS

Low glycaemia increases risk of frailty and functional decline in older people with type 2 diabetes. Management should minimise incidence of low glycaemia in these patients.

Influence of glycemic control and hypoglycemia on the risk of fracture in patients with diabetes mellitus: a systematic review and meta-analysis of observational studies

Individuals with diabetes mellitus (DM) have an increased risk of fracture. Glycemic control is crucial to the management of DM, but there are concerns pertaining to hypoglycemia development in the course of glycemic control target achievement. The extent to which glycemic control may affect the risk of fracture remains less defined. Hypoglycemia-induced falls have been suggested to contribute to an elevated risk of fracture in DM patients. In this meta-analysis of observational studies, we aimed to investigate the relative contribution of glycemic control, as measured by glycated hemoglobin (HbA1c), and hypoglycemia to the risk of fracture in DM. The PubMed and Web of Science databases were searched for relevant studies. A random-effects model was used to generate summary relative risks (RRs) and 95% confidence intervals (CIs). Both increased HbA1c levels (RR _{per 1% increase} 1.08, 95% CI 1.03, 1.14; n_studies = 10) and hypoglycemia (RR 1.52, 95% CI 1.23, 1.88; n_studies = 8) were associated with an increased risk of fracture. The association between HbA1c levels and the risk of fracture was somewhat nonlinear, with a noticeably increased risk observed at an HbA1c level ≥ 8%. The positive associations of HbA1c levels and hypoglycemia with the risk of fracture did not reach statistical significance in the studies that adjusted for insulin use, hypoglycemia, or falls for the former and in those that adjusted for falls for the latter. In summary, both increased HbA1c levels and hypoglycemia may increase the risk of fracture in patients with DM. The positive association between HbA1c levels and the risk of fracture appears to be, in part, explained by hypoglycemia-induced falls, possibly due to insulin use. The avoidance of hypoglycemia in the course of achieving good glycemic control through the careful selection of glucose-lowering medications may contribute to fracture prevention by reducing the risk of falls related to treatment-induced hypoglycemia.

Management of bone fragility in type 2 diabetes: Perspective from an interdisciplinary expert panel

AIM

Bone fragility is increasingly recognized as a relevant complication of type 2 diabetes (T2D) and diabetic patients with fragility fractures have higher mortality rates than non diabetic individuals or diabetic patients without fractures. However, current diagnostic approaches for fracture risk stratification, such as bone mineral density measurement or the use of risk assessment algorithms, largely underestimate fracture risk in T2D patients. A multidisciplinary expert panel was established in order to in order to formulate clinical consensus recommendations on bone health assessment and management of fracture risk in patients with T2D.

DATA SYNTHESIS

The following key questions were addressed: a) which are the risk factors for bone fragility in T2D?, b) which diagnostic procedures can be currently used to stratify fracture risk in T2D patients?, c) which are the effects of antidiabetic treatments on bone?, and d) how to prevent and treat bone fragility in T2D patients? Based on the available data members of this panel suggest that the stratification of fracture risk in patients with diabetes should firstly rely on the presence of a previous fragility fracture and on the individual risk profile, with the inclusion of T2D-specific risk factors (namely T2D duration above 10 yrs, presence of chronic T2D complications, use of insulin or thiazolidinediones and persistent HbA1c levels above 8% for at least 1 year). Two independent diagnostic approaches were then suggested in the presence or the absence of a prevalent fragility fracture, respectively.

CONCLUSIONS

Clinical trials in T2D patients at risk for fragility fractures are needed to determine the efficacy and safety of available antiresorptive and anabolic agents in this specific setting.

Risk Factors for Incident Fracture in Older Adults With Type 2 Diabetes: The Framingham Heart Study

OBJECTIVE

To identify risk factors for fracture in type 2 diabetes.

RESEARCH DESIGN AND METHODS

This prospective study included members of the Framingham Original and Offspring Cohorts. Type 2 diabetes was defined as fasting plasma glucose >125 mg/dL or use of type 2 diabetes therapy. We used repeated-measures Cox proportional hazards regression to calculate hazard ratios (HRs) and 95% CIs for associations between potential predictors and incidence of fragility fracture.

RESULTS

Participants included 793 individuals with type 2 diabetes. Mean ± SD age was 70 ± 10 years; 45% were women. A total of 106 incident fractures occurred over 1,437 observation follow-up intervals. Fracture incidence increased with age (adjusted HRs 1.00, 1.44 [95% CI 0.65, 3.16], and 2.40 [1.14, 5.04] for <60, 60-70, and >70 years, respectively; P _trend = 0.02), female sex (2.23 [1.26, 3.95]), HbA_1c (1.00, 2.10 [1.17, 3.75], and 1.29 [0.69, 2.41] for 4.45-6.46% [25-47 mmol/mol], 6.50-7.49% [48-58 mmol/mol], and 7.50-13.86% [58-128 mmol/mol]; P _trend =0.03), falls in past year (1.00, 1.87 [0.82, 4.28], and 3.29 [1.34, 8.09] for no falls, one fall, and two or more falls; P _trend =0.03), fracture history (2.05 [1.34, 3.12]), and lower grip strength (0.82 [0.69, 0.99] per 5-kg increase). Femoral neck bone mineral density, BMI, smoking, physical function, chronic diseases, medications, and physical function were not associated with fracture incidence.

CONCLUSIONS

Prior falls, fractures, low grip strength, and elevated HbA_1c are risk factors for fractures in older adults with type 2 diabetes. Evaluation of these factors may improve opportunities for early intervention and reduce fractures in this high-risk group.

Bone Homeostasis and Gut Microbial-Dependent Signaling Pathways

Although research on the osteal signaling pathway has progressed, understanding of gut microbial-dependent signaling pathways for metabolic and immune bone homeostasis remains elusive. In recent years, the study of gut microbiota has shed light on our understanding of bone homeostasis. Here, we review microbiota-mediated gut-bone crosstalk via bone morphogenetic protein/SMADs, Wnt and OPG/receptor activator of nuclear factor-kappa B ligand signaling pathways in direct (translocation) and indirect (metabolite) manners. The mechanisms underlying gut microbiota involvement in these signaling pathways are relevant in immune responses, secretion of hormones, fate of osteoblasts and osteoclasts and absorption of calcium. Collectively, we propose a signaling network for maintaining a dynamic homeostasis between the skeletal system and the gut ecosystem. Additionally, the role of gut microbial improvement by dietary intervention in osteal signaling pathways has also been elucidated. This review provides unique resources from the gut microbial perspective for the discovery of new strategies for further improving treatment of bone diseases by increasing the abundance of targeted gut microbiota.

Bone fragility in patients with diabetes mellitus: A consensus statement from the working group of the Italian Diabetes Society (SID), Italian Society of Endocrinology (SIE), Italian Society of Gerontology and Geriatrics (SIGG), Italian Society of Orthopaedics and Traumatology (SIOT)

Bone fragility is one of the possible complications of diabetes, either type 1 (T1D) or type 2 (T2D). Bone fragility can affect patients of different age and with different disease severity depending on type of diabetes, disease duration and the presence of other complications. Fracture risk assessment should be started at different stages in the natural history of the disease depending on the type of diabetes and other risk factors. The risk of fracture in T1D is higher than in T2D, imposing a much earlier screening and therapeutic intervention that should also take into account a patient's life expectancy, diabetes complications etc. The therapeutic armamentarium for T2D has been enriched with drugs that may influence bone metabolism, and clinicians should be aware of these effects. Considering the complexity of diabetes and osteoporosis and the range of variables that influence treatment choices in a given individual, the Working Group on bone fragility in patients with diabetes mellitus has identified and issued recommendations based on the variables that should guide screening of bone fragility and management of diabetes and bone fragility: (A)ge, (B)MD, (C)omplications, (D)uration of disease, & (F)ractures (ABCD&F). Consideration of these parameters may help clinicians identify the best time for screening, the appropriate glycaemic target and anti-osteoporosis drug for patients with diabetes at risk of or with bone fragility.

Risk of non-vertebral fractures in men with type 2 diabetes: A systematic review and meta-analysis of cohort studies

PURPOSE

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder. Research regarding the risk of non-vertebral fractures in men, especially in elderly men with T2DM, has not been a priority. T2DM is not a known independent risk factor for low-energy fractures in patients. We aimed to explore the relationship between men (especially older men) with T2DM and the risk of non-vertebral fractures and the reasons for the sex differences.

METHODS

The PubMed, MEDLINE, and Cochrane Library databases were searched for articles on T2DM and fracture risk. A meta-analysis, including heterogeneity testing, publication bias analysis, and subgroup analysis of the included studies, was performed using STATA software.

RESULTS

Sixteen studies involving 1,758,225 participants, 59,909 non-vertebral fracture events, and 6430 vertebral fracture events were included in this research. The adjusted relative risk of T2DM and non-vertebral fracture in men was 1.20 (95% confidence interval [CI] 1.09-1.31), implying that men with T2DM have a slightly increased risk of non-vertebral fracture.

CONCLUSION

Male patients with T2DM have a slightly increased risk of non-vertebral fractures. Due to the differences in bone strength, sex steroid hormone levels, bone quality and muscle strength and balance, men with type 2 diabetes have a lower risk of non-vertebral fractures than women.

Glucose Metabolism in Osteoblasts in Healthy and Pathophysiological Conditions

Bone tissue in vertebrates is essential to performing movements, to protecting internal organs and to regulating calcium homeostasis. Moreover, bone has also been suggested to contribute to whole-body physiology as an endocrine organ, affecting male fertility; brain development and cognition; and glucose metabolism. A main determinant of bone quality is the constant remodeling carried out by osteoblasts and osteoclasts, a process consuming vast amounts of energy. In turn, clinical conditions associated with impaired glucose metabolism, including type I and type II diabetes and anorexia nervosa, are associated with impaired bone turnover. As osteoblasts are required for collagen synthesis and matrix mineralization, they represent one of the most important targets for pharmacological augmentation of bone mass. To fulfill their function, osteoblasts primarily utilize glucose through aerobic glycolysis, a process which is regulated by various molecular switches and generates adenosine triphosphate rapidly. In this regard, researchers have been investigating the complex processes of energy utilization in osteoblasts in recent years, not only to improve bone turnover in metabolic disease, but also to identify novel treatment options for primary bone diseases. This review focuses on the metabolism of glucose in osteoblasts in physiological and pathophysiological conditions.

Targeting reactive oxygen species in stem cells for bone therapy

Reactive oxygen species (ROS) have emerged as key players in regulating the fate and function of stem cells from both non-hematopoietic and hematopoietic lineages in bone marrow, and thus affect the osteoblastogenesis-osteoclastogenesis balance and bone homeostasis. Accumulating evidence has linked ROS and associated oxidative stress with the progression of bone disorders, and ROS-based therapeutic strategies have appeared to achieve favorable outcomes in bone. We review current knowledge of the multifactorial roles and mechanisms of ROS as a target in bone pathology. In addition, we discuss emerging ROS-based therapeutic strategies that show potential for bone therapy. Finally, we highlight the opportunities and challenges facing ROS-targeted stem cell therapeutics for improving bone health.

Hemoglobin A1c Threshold for Reduction in Bone Turnover in Men With Type 2 Diabetes Mellitus

BACKGROUND

Emerging data suggest that type 2 diabetes mellitus (T2D) is associated with an increased risk for fractures despite relatively normal or increased bone mineral density (BMD). Although the mechanism for bone fragility in T2D patients is multifactorial, whether glycemic control is important in generating this impairment in bone metabolism remains unclear. The purpose of our study is to identify a hemoglobin A1c (A1c) threshold level by which reduction in bone turnover begins in men with T2D.

METHOD

A cross-sectional analysis of baseline data was obtained from 217 men, ages 35-65, regardless of the presence or absence of hypogonadism or T2D, who participated in 2 clinical trials. The following data were obtained: A1c by HPLC, testosterone and estradiol by LC/MS, bone turnover markers Osteocalcin [OC], C-terminal telopeptide [CTx], and sclerostin by ELISA, and BMD by DXA. Patients were grouped into 4 categories based of A1c (group I: <6%, group II: 6.0-6.4%, group III: 6.5-6.9%, and group IV: ≥7%). Threshold models were fit to the data using nonlinear regression and group comparisons among the different A1c categories performed by ANOVA.

RESULTS

Threshold model and nonlinear regression showed an A1c cut-off of 7.0, among all choices of A1cs, yields the least sum of squared errors. A comparison of bone turnover markers revealed relatively lower OC (p = 0.002) and CTx (p = 0.0002) in group IV (A1c ≥7%), compared to the other groups. An analysis of men with T2D (n = 94) showed relatively lower OC (p=0.001) and CTx (p=0.002) in those with A1c ≥7% compared to those with <7%, respectively. The significance between groups persisted even after adjusting for medications and duration of diabetes.

CONCLUSION

An analysis across our entire study population showed a breakpoint A1c level of 7% or greater is associated with lower bone turnover. Also in men with T2D, an A1c ≥7% is associated with low bone turnover.

Glucose-Lowering Drugs and Fracture Risk-a Systematic Review

PURPOSE OF REVIEW

Diabetes mellitus (DM) is associated with increased fracture risk. The aim of this systematic review was to examine the effects of different classes of glucose-lowering drugs on fracture risk in patients with type 2 DM. The heterogeneity of the included studies did not allow formal statistical analyses.

RECENT FINDINGS

Sixty studies were included in the review. Metformin, dipeptidylpeptidase-IV inhibitors, glucagon-like peptide-1 receptor agonists, and sodium-glucose cotransporter 2-inhibitors do not appear to increase fracture risk. Results for insulin and sulphonylureas were more disparate, although there may be an increased fracture risk related to hypoglycemia and falls with these treatments. Glitazones were consistently associated with increased fracture risk in women, although the evidence was sparser in men. New glucose-lowering drugs are continuously being developed and better understanding of these is leading to changes in prescription patterns. Our findings warrant continued research on the effects of glucose-lowering drugs on fracture risk, elucidating the class-specific effects of these drugs.

The risk of hip and non-vertebral fractures in type 1 and type 2 diabetes: A systematic review and meta-analysis update

BACKGROUND

Diabetes is associated with increased fracture risk but we do not know what affects this risk. We investigated the risk of hip and non-vertebral fractures in diabetes and whether this risk was affected by age, gender, body mass index, diabetes type and duration, insulin use and diabetic complications.

METHODS

We selected a previously published review to be updated. MEDLINE, Embase and Cochrane databases were searched up to March 2020. We included observational studies with age and gender-adjusted risk of fractures in adults with diabetes compared to adults without diabetes. We extracted data from published reports that we summarised using random effects model.

FINDINGS

From the 3140 records identified, 49 were included, 42 in the hip fracture analysis, reporting data from 17,571,738 participants with 319,652 fractures and 17 in the non-vertebral fracture review, reporting data from 2,978,487 participants with 181,228 fractures. We found an increase in the risk of fracture in diabetes both for hip (RR 4.93, 3.06-7.95, in type 1 diabetes and RR1.33, 1.19-1.49, in type 2 diabetes) and for non-vertebral fractures (RR 1.92, 0.92-3.99, in type 1 and RR 1.19, 1,11-1.28 in type 2). At the hip, the risk was higher in the younger population in both type 1 and type 2 diabetes. In those with type 2 diabetes, longer diabetes duration and insulin use was associated with an increased risk. We did not investigate the effect of bone density, falls, anti-diabetic drugs and hypoglycemia.

CONCLUSION

Diabetes is associated with an increase in both hip and non-vertebral fracture risk.

Challenges and Strategies for Inpatient Diabetes Management in Older Adults

Adults older than 65 years of age are the fastest growing segment of the U.S. population. Aging is also one of the most important risk factors for diabetes, and about one-third of all individuals with diabetes are in this age-group. Older people with diabetes are more likely to have comorbidities such as hypertension, ischemic heart disease, chronic kidney disease, and cognitive impairment, which lead to higher rates of hospital admissions compared with individuals without diabetes. Professional organizations have recommended patient-centric individualized glycemic reduction approaches, with an emphasis on potential harms of intensive glycemic control and overtreatment in older adults. Insulin therapy remains a mainstay of diabetes management in the inpatient setting regardless of patients' age; however, there is uncertainty about optimal glycemic targets during the hospital stay. Increasing evidence supports selective use of dipeptidyl peptidase-4 inhibitors, alone or in combination with low-dose basal insulin, in older noncritically ill patients with mild to moderate hyperglycemia. This article reviews the prevalence, diagnosis, and monitoring of, and the available treatment strategies for, diabetes among elderly patients in the inpatient setting.

High Glucose Downregulates Connexin 43 Expression and Its Gap Junction and Hemichannel Function in Osteocyte-like MLO-Y4 Cells Through Activation of the p38MAPK/ERK Signal Pathway

PURPOSE

Osteocyte network structure correlates with bone material quality. This network is profoundly altered in diabetic mice; however, the underlying mechanisms are unknown. The gap junction protein connexin 43 (Cx43) is necessary for normal osteocyte function and osteocyte network formation. Here, we evaluated Cx43 expression in patients with diabetes, the effect of high glucose on Cx43 expression, and the function of Cx43 gap junctions and hemichannels in osteocyte-like MLO-Y4 (MLO-Y4) cells.

PATIENTS AND METHODS

Human cortical bone samples were obtained from patients with or without type II diabetes mellitus (T2DM) who underwent arthroplasty surgery to treat osteoporosis-induced femoral neck fracture.

Cx43 expression was quantified in human cortical bone samples from both groups of patients and MLO-Y4 cells. The functions of Cx43 gap junctions and hemichannels in MLO-Y4 cells were evaluated using dye transfer and dye uptake assays, respectively. Furthermore, we evaluated levels of membrane Cx43 (mCx43), the functional form, and p38MAPK/ERK1/2 signaling, which is involved in mCx43 internalization, to characterize the mechanism of decreased Cx43 expression and gap junctions and hemichannels function.

RESULTS

Osteocyte Cx43 expression was decreased in femoral neck cortical bone samples of patients with T2DM patients compared with the non-diabetic control group. In addition, Cx43 expression was decreased in MLO-Y4 cells treated with high glucose. The functions of Cx43 gap junctions and hemichannels were inhibited in MLO-Y4 cells treated with high glucose. mCx43 expression was decreased in response to activation of p38-MAPK/ERK signaling. Inhibition of the p38-MAPK/ERK pathway partially reversed the decreases in Cx43 hemichannels and gap-junctions function.

CONCLUSION

High glucose dampened Cx43 gap junction and hemichannel function in MLO-Y4 cells by activating the p38MAPK/ERK pathway leading to subsequent mCx43 internalization.

Insulin Signaling in Bone Marrow Adipocytes

PURPOSE OF REVIEW

The goal of this review is to discuss the role of insulin signaling in bone marrow adipocyte formation, metabolic function, and its contribution to cellular senescence in relation to metabolic bone diseases.

RECENT FINDINGS

Insulin signaling is an evolutionally conserved signaling pathway that plays a critical role in the regulation of metabolism and longevity. Bone is an insulin-responsive organ that plays a role in whole body energy metabolism. Metabolic disturbances associated with obesity and type 2 diabetes increase a risk of fragility fractures along with increased bone marrow adiposity. In obesity, there is impaired insulin signaling in peripheral tissues leading to insulin resistance. However, insulin signaling is maintained in bone marrow microenvironment leading to hypermetabolic state of bone marrow stromal (skeletal) stem cells associated with accelerated senescence and accumulation of bone marrow adipocytes in obesity. This review summarizes current findings on insulin signaling in bone marrow adipocytes and bone marrow stromal (skeletal) stem cells and its importance for bone and fat metabolism. Moreover, it points out to the existence of differences between bone marrow and peripheral fat metabolism which may be relevant for developing therapeutic strategies for treatment of metabolic bone diseases.

Impact of Diabetes Mellitus on Bone Health

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