MECHANISMS IN ENDOCRINOLOGY: Mechanisms and evaluation of bone fragility in type 1 diabetes mellitus

Bone Fragility in Diabetes and its Management: A Narrative Review

Bone fragility is a serious yet under-recognised complication of diabetes mellitus (DM) that is associated with significant morbidity and mortality. Multiple complex pathophysiological mechanisms mediating bone fragility amongst DM patients have been proposed and identified. Fracture risk in both type 1 diabetes (T1D) and type 2 diabetes (T2D) continues to be understated and underestimated by conventional risk assessment tools, posing an additional challenge to the identification of at-risk patients who may benefit from earlier intervention or preventive strategies. Over the years, an increasing body of evidence has demonstrated the efficacy of osteo-pharmacological agents in managing skeletal fragility in DM. This review seeks to elaborate on the risk of bone fragility in DM, the underlying pathogenesis and skeletal alterations, the approach to fracture risk assessment in DM, management strategies and therapeutic options.

Association of a body shape index with femur bone mineral density among older adults: NHANES 2007-2018

This study investigated the relationship between A body shape index (ABSI) and bone mineral density (BMD) in older Americans and found a negative linear association, which was particularly pronounced in diabetic population. An early focus on ABSI in the elderly population will help in the prevention of osteoporosis.

OBJECTIVE

A body shape index (ABSI) is an abdominal obesity index developed based on epidemiological statistics and high ABSI indicates that waist circumference (WC) is higher than expected for a given height and weight and corresponds to a more central concentration of body volume. The objective of this study was to determine whether there is a linear or nonlinear relationship between ABSI and total femur bone mineral density (BMD) in older Americans and whether the relationship between the ABSI and total femur BMD varies across populations.

METHODS

This cross-sectional study was based on data from the 2007-2018 National Health and Nutrition Examination Survey (NHANES). Weighted multiple linear regression, restricted cubic spline (RCS) curves, subgroup analysis, and interaction tests were used to examine the association between ABSI and total femur BMD.

RESULTS

This study included 2505 older adults. This study found a negative linear correlation between ABSI and total femur BMD (β = -3.2, 95%CI: -5.0, -1.4, p < 0.001). When participants were grouped according to quartiles of ABSI, those in the upper quartile had lower total femur BMD compared to those in the bottom quartile of ABSI. This negative association remained consistent across gender, age, education level, smoking, physical activity and BMI subgroups. However, in the diabetes subgroup, ABSI showed a stronger negative association with total femur BMD.

CONCLUSIONS

The study shows a negative linear association between ABSI and total femur BMD in older Americans, with this negative association being stronger in the diabetic population.

Gut hormone analogues and skeletal health in diabetes and obesity: Evidence from preclinical models

Diabetes mellitus and obesity are rapidly growing worldwide. Aside from metabolic disturbances, these two disorders also affect bone with a higher prevalence of bone fractures. In the last decade, a growing body of evidence suggested that several gut hormones, including ghrelin, gastrin, glucose-dependent insulinotropic polypeptide (GIP), glucagon, and glucagon-like peptide-1 and 2 (GLP-1 and GLP-2, respectively) may affect bone physiology. Several gut hormone analogues have been developed for the treatment of type 2 diabetes and obesity, and could represent a new alternative in the therapeutic arsenal against bone fragility. In the present review, a summary of the physiological roles of these gut hormones and their analogues is presented at the cellular level but also in several preclinical models of bone fragility disorders including type 2 diabetes mellitus, especially on bone mineral density, microarchitecture and bone material properties. The present review also summarizes the impact of GLP-1 receptor agonists approved for the treatment of type 2 diabetes mellitus and the more recent dual or triple analogue on bone physiology and strength.

Genetically determined type 1 diabetes mellitus and risk of osteoporosis

BACKGROUND

Observational evidence suggests that type 1 diabetes mellitus (T1DM) is associated with the risk of osteoporosis (OP). Nevertheless, it is not apparent whether these correlations indicate a causal relationship. To elucidate the causal relationship, a two-sample Mendelian randomization (MR) analysis was performed.

METHODS

T1DM data was obtained from the large genome-wide association study (GWAS), in which 6683 cases and 12,173 controls from 12 European cohorts were involved. Bone mineral density (BMD) samples at four sites were extracted from the GEnetic Factors for OSteoporosis (GEFOS) consortium, including forearm (FA) (n = 8,143), femoral neck (FN) (n = 32,735), lumbar spine (LS) (n = 28,498), and heel (eBMD) (n = 426,824). The former three samples were from mixed populations and the last one was from European. Inverse variance weighting, MR-Egger, and weighted median tests were used to test the causal relationship between T1DM and OP. A series of sensitivity analyses were then conducted to verify the robustness of the results.

RESULTS

Twenty-three independent SNPs were associated with FN-BMD and LS-BMD, twenty-seven were associated with FA-BMD, and thirty-one were associated with eBMD. Inverse variance-weighted estimates indicated a causal effect of T1DM on FN-BMD (odds ratio (OR) =1.033, 95 % confidence interval (CI): 1.012-1.054, p = 0.002) and LS-BMD (OR = 1.032, 95 % CI: 1.005-1.060, p = 0.022) on OP risk. Other MR methods, including weighted median and MR-Egger, calculated consistent trends. While no significant causation was found between T1DM and the other sites (FA-BMD: OR = 1.008, 95 % CI: 0.975-1.043, p = 0.632; eBMD: OR = 0.993, 95 % CI: 0.985-1.001, p = 0.106). No significant heterogeneity (except for eBMD) or horizontal pleiotropy was found for instrumental variables, suggesting these results were reliable and robust.

CONCLUSIONS

This study shows a causal relationship between T1DM and the risk of some sites of OP (FN-BMD, LS-BMD), allowing for continued research to discover the clinical and experimental mechanisms of T1DM and OP. It also contributes to the recommendation if patients with T1DM need targeted care to promote bone health and timely prevention of osteoporosis.

Diagnosing Osteoporosis in Diabetes-A Systematic Review on BMD and Fractures

PURPOSE OF REVIEW

Recently, the American Diabetes Association updated the 2024 guidelines for Standards of Care in Diabetes and recommend that a T-score of - 2.0 in patients with diabetes should be interpreted as equivalent to - 2.5 in people without diabetes. We aimed to evaluate the most recent findings concerning the bone mineral density (BMD)-derived T-score and risk of fractures related to osteoporosis in subjects with diabetes.

RECENT FINDINGS

The dual-energy X-ray absorptiometry (DXA) scan is the golden standard for evaluating BMD. The BMD-derived T-score is central to fracture prediction and signifies both diagnosis and treatment for osteoporosis. However, the increased fracture risk in diabetes is not sufficiently explained by the T-score, complicating the identification and management of fracture risk in these patients. Recent findings agree that subjects with type 2 diabetes (T2D) have a higher T-score and higher fracture risk compared with subjects without diabetes. However, the actual number of studies evaluating the direct association of higher fracture risk at higher T-score levels is scant. Some studies support the adjustment based on the 0.5 BMD T-score difference between subjects with T2D and subjects without diabetes. However, further data from longitudinal studies is warranted to validate if the T-score treatment threshold necessitates modification to prevent fractures in subjects with diabetes.

Use of noninvasive imaging to identify causes of skeletal fragility in adults with diabetes: a review

Diabetes, a disease marked by consistent high blood glucose levels, is associated with various complications such as neuropathy, nephropathy, retinopathy, and cardiovascular disease. Notably, skeletal fragility has emerged as a significant complication in both type 1 (T1D) and type 2 (T2D) diabetic patients. This review examines noninvasive imaging studies that evaluate skeletal outcomes in adults with T1D and T2D, emphasizing distinct skeletal phenotypes linked with each condition and pinpointing gaps in understanding bone health in diabetes. Although traditional DXA-BMD does not fully capture the increased fracture risk in diabetes, recent techniques such as quantitative computed tomography, peripheral quantitative computed tomography, high-resolution quantitative computed tomography, and MRI provide insights into 3D bone density, microstructure, and strength. Notably, existing studies present heterogeneous results possibly due to variations in design, outcome measures, and potential misclassification between T1D and T2D. Thus, the true nature of diabetic skeletal fragility is yet to be fully understood. As T1D and T2D are diverse conditions with heterogeneous subtypes, future research should delve deeper into skeletal fragility by diabetic phenotypes and focus on longitudinal studies in larger, diverse cohorts to elucidate the complex influence of T1D and T2D on bone health and fracture outcomes.

A pilot study: effect of irisin on trabecular bone in a streptozotocin-induced animal model of type 1 diabetic osteopathy utilizing a micro-CT

Background

Osteoporosis is a significant co-morbidity of type 1 diabetes mellitus (DM1) leading to increased fracture risk. Exercise-induced hormone 'irisin' in low dosage has been shown to have a beneficial effect on bone metabolism by increasing osteoblast differentiation and reducing osteoclast maturation, and inhibiting apoptosis and inflammation. We investigated the role of irisin in treating diabetic osteopathy by observing its effect on trabecular bone.

Methods

DM1 was induced by intraperitoneal injection of streptozotocin 60 mg/kg body weight. Irisin in low dosage (5 µg twice a week for 6 weeks I/P) was injected into half of the control and 4-week diabetic male Wistar rats. Animals were sacrificed six months after induction of diabetes. The trabecular bone in the femoral head and neck was analyzed using a micro-CT technique. Bone turnover markers were measured using ELISA, Western blot, and RT-PCR techniques.

Results

It was found that DM1 deteriorates the trabecular bone microstructure by increasing trabecular separation (Tb-Sp) and decreasing trabecular thickness (Tb-Th), bone volume fraction (BV/TV), and bone mineral density (BMD). Irisin treatment positively affects bone quality by increasing trabecular number p < 0.05 and improves the BMD, Tb-Sp, and BV/TV by 21-28%. The deterioration in bone microarchitecture is mainly attributed to decreased bone formation observed as low osteocalcin and high sclerostin levels in diabetic bone samples p < 0.001. The irisin treatment significantly suppressed the serum and bone sclerostin levels p < 0.001, increased the serum CTX1 levels p < 0.05, and also showed non-significant improvement in osteocalcin levels.

Conclusions

This is the first pilot study to our knowledge that shows that a low dose of irisin marginally improves the trabecular bone in DM1 and is an effective peptide in reducing sclerostin levels.

Causal relationship between type 2 diabetes mellitus and bone mineral density: a Mendelian randomization study in an East Asian population

It remains unclear whether the relationship between type 2 diabetes mellitus (T2DM) and bone mineral density (BMD) reflects causality in East Asian populations. Herein, a Mendelian randomization study conducted in East Asian population enhances the current clinical cognition that T2DM is not associated with reduction in BMD.

PURPOSE

A Mendelian randomization (MR) approach was utilized to investigate the relationship between type 2 diabetes mellitus (T2DM) and bone mineral density (BMD) in East Asian populations.

METHODS

Genome-wide association study summary data from BioBank Japan were used to identify genetic variants strongly related to T2DM risk (36,614 cases and 155,150 controls) and osteoporosis (7788 cases and 204,665 controls). Heel BMD GWAS data of 1260 East Asian people from ieu open gwas project was considered as a second outcome. Inverse variance-weighted (IVW) analysis was mainly applied; MR-Egger and the weighted median were also used to obtain robust estimates. A series of sensitivity analyses including Cochran's Q test, MR-Egger regression, and leave-one-out analysis were used to detect pleiotropy or heterogeneity.

RESULTS

In the main analysis, IVW estimates indicated that T2DM significantly associated with the risk of osteoporosis (odds ratio = 0.92, 95% CI: 0.86-0.99, p = 0.016) and with higher BMD (OR: 1.25, 95% CI: 1.06-1.46, p = 6.49 × 10-3). Results of comprehensive sensitivity analysis were consistent with the main causality estimate. Horizontal pleiotropy and heterogeneity were absent in our MR study.

CONCLUSIONS

T2DM is not associated with reduction in BMD in terms of genetic polymorphism in East Asian populations.

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.

Hyperglycemic microenvironment compromises the homeostasis of communication between the bone-brain axis by the epigenetic repression of the osteocalcin receptor, Gpr158 in the hippocampus

Diabetes mellitus (DM) is a chronic metabolic disease, mainly characterized by increased blood glucose and insulin dysfunction. In response to the persistent systemic hyperglycemic state, numerous metabolic and physiological complications have already been well characterized. However, its relationship to bone fragility, cognitive deficits and increased risk of dementia still needs to be better understood. The impact of chronic hyperglycemia on bone physiology and architecture was assessed in a model of chronic hyperglycemia induced by a single intraperitoneal administration of streptozotocin (STZ; 55 mg/kg) in Wistar rats. In addition, the bone-to-brain communication was investigated by analyzing the gene expression and methylation status of genes that encode the main osteokines released by the bone [Fgf23 (fibroblast growth factor 23), Bglap (bone gamma-carboxyglutamate protein) and Lcn2 (lipocalin 2) and their receptors in both, the bone and the brain [Fgfr1 (fibroblast growth factor receptor 1), Gpr6A (G-protein coupled receptor family C group 6 member A), Gpr158 (G protein-coupled receptor 158) and Slc22a17 (Solute carrier family 22 member 17)]. It was observed that chronic hyperglycemia negatively impacted on bone biology and compromised the balance of the bone-brain endocrine axis. Ultrastructural disorganization was accompanied by global DNA hypomethylation and changes in gene expression of DNA-modifying enzymes that were accompanied by changes in the methylation status of the osteokine promoter region Bglap and Lcn2 (lipocalin 2) in the femur. Additionally, the chronic hyperglycemic state was accompanied by modulation of gene expression of the osteokines Fgf23 (fibroblast growth factor 23), Bglap (bone gamma-carboxyglutamate protein) and Lcn2 (lipocalin 2) in the different brain regions. However, transcriptional regulation mediated by DNA methylation was observed only for the osteokine receptors, Fgfr1(fibroblast growth factor receptor 1) in the striatum and Gpr158 (G protein-coupled receptor 158) in the hippocampus. This is a pioneer study demonstrating that the chronic hyperglycemic state compromises the crosstalk between bone tissue and the brain, mainly affecting the hippocampus, through transcriptional silencing of the Bglap receptor by hypermethylation of Gpr158 gene.

Association of bone mineral density with prediabetes risk among African-American and European-American adult offspring of parents with type 2 diabetes

Introduction

Type 2 diabetes mellitus (T2DM) is associated with alterations in bone mineral density (BMD), but association between prediabetes and BMD is unclear.

Methods

We analyzed BMD among the initially normoglycemic participants in the Pathobiology of Prediabetes in a Biracial Cohort (POP-ABC) study in relation to incident prediabetes during 5 years of follow-up.

Results and Discussion

A total of 343 participants (193 Black, 150 White) underwent DEXA during Year 1 of POP-ABC and were followed quarterly for 5 years. The mean age was 44.2 ± 10.6 years; BMI was 30.2 ± 7.23 kg/m2. At baseline, the mean BMD was 1.176 ± 0.135 g/cm2 (1.230 ± 0.124 g/cm2 in men vs. 1.154 ± 0.134 g/cm2 in women, P<0.0001; 1.203 ± 0.114 g/cm2 in Black vs. 1.146 ± 0.150 g/cm2 in White participants, P=0.0003). During 5 years of follow-up, 101 participants developed prediabetes and 10 subjects developed T2DM (progressors); 232 were nonprogressors. Progressors to prediabetes had numerically higher baseline BMD and experienced lower 1-year decline in BMD (P<0.0001) compared with nonprogressors. From Kaplan-Meier analysis, the time to 50% prediabetes survival was 2.15 y among participants in the lowest quartile of baseline BMD, longer than those in higher quartiles (1.31 - 1.41 y). Values for BMD correlated inversely with age and adiponectin levels, and positively with BMI. In logistic regression analysis, BMD z score significantly predicted incident prediabetes: more negative BMD z scores were associated with decreased incident prediabetes (odds ratio 0.598 [95% confidence interval 0.407 - 0.877], P=0.0085), after controlling for age, BMI, change in BMI, ethnicity, blood glucose and adiponectin.

Conclusions

Among initially normoglycemic individuals, higher baseline BMD was associated with higher risk of incident prediabetes during 5 years of follow-up.

[Diagnosis and management of patients with diabetes and co-existing osteoporosis (Update 2023) : Common guideline of the Austrian Society for Bone and Mineral Research and the Austrian Diabetes Society]

Fragility fractures are increasingly recognized as a complication of both type 1 and type 2 diabetes, with fracture risk that increases with disease duration and poor glycemic control. The identification and management of fracture risk in these patients remains challenging. This manuscript explores the clinical characteristics of bone fragility in adults with diabetes and highlights recent studies that have evaluated areal bone mineral density (BMD), bone microstructure and material properties, biochemical markers, and fracture prediction algorithms (FRAX) in these patients. It further reviews the impact of diabetes drugs on bone tissue as well as the efficacy of osteoporosis treatments in this population. An algorithm for the identification and management of diabetic patients at increased fracture risk is proposed.

Perceptions of fracture and fall risk and of the benefits and barriers to exercise in adults with diabetes

The increased risk of fractures and falls is under-appreciated by adults living with diabetes and by their healthcare providers. Strategies to overcome perceived exercise barriers and exercise programs optimized for bone health should be implemented.

PURPOSE

The purpose of the study was to assess the perceptions of fracture and fall risk, and the perceived benefits of and barriers to exercise in adults ≥ 50 years old living with type 1 (T1D) and type 2 diabetes (T2D).

METHODS

Participants were recruited through social media and from medical clinics and invited to complete a self-administered online survey, comprising 38 close-ended questions and 4 open-ended questions.

RESULTS

A total of 446 participants completed the survey: 38% T1D, 59% T2D, and 3% with unreported diabetes type. Most participants did not believe that having diabetes increased their risk of fractures (81%) nor falls (68%), and more than 90% reported having not been informed about diabetes-related fracture risk by their physicians. Among exercise types, participation in moderate aerobic exercise was most common (54%), while only 31%, 32%, and 37% of participants engaged in strenuous aerobic, resistance, and balance/flexibility exercise, respectively. The most prevalent barrier to exercise for both T1D and T2D was a lack of motivation, reported by 54% of participants. Lack of time and fear of hypoglycemia were common exercise barriers reported by participants with T1D. Most participants owned a smart phone (69%), tablet (60%), or computer (56%), and 46% expressed an interest in partaking in virtually delivered exercise programs.

CONCLUSIONS

Adults living with diabetes have limited awareness of increased fall and fracture risk. These risks are insufficiently highlighted by health care providers; strategies to overcome perceived exercise barriers and exercise programs optimized for bone health should be implemented.

Skeletal manifestations in a streptozotocin-induced C57BL/6 model of Type 1 diabetes

Diabetes Mellitus is a metabolic disease which profoundly affects many organ systems in the body, including the skeleton. As is often the case with biology, there are inherent differences between the sexes when considering skeletal development and disease progression and outcome. Therefore, the aim of this study was to develop a protocol to reliably induce diabetes in both sexes of the C57BL/6 mouse utilizing streptozotocin (STZ) and to characterize the resulting bone phenotype. We hypothesized that destruction of the β-cells in the pancreatic islet by STZ would result in a diabetic state with downstream skeletal manifestations. Beginning at 8 weeks of age, mice were injected for 5 consecutive days with STZ (65 mg/kg males, 90 mg/kg females) dissolved in a citrate buffer. The diabetic state of the mice was monitored for 5 weeks to ensure persistent hyperglycemia and mice were euthanized at 15 weeks of age. Diabetes was confirmed through blood glucose monitoring, glucose and insulin tolerance testing, HbA1c measurement, and histological staining of the pancreas. The resulting bone phenotype was characterized using microcomputed tomography to assess bone structure, and whole bone mechanical testing to assess bone functional integrity. Mice from both sexes experienced loss of β-cell mass and increased glycation of hemoglobin, as well as reduced trabecular thickness and trabecular tissues mineral density (TMD), and reduced cortical thickness and cortical bone area fraction. In female mice the change area fraction was driven by a reduction in overall bone size while in male mice, the change was driven by increased marrow area. Males also experienced reduced cortical TMD. Mechanical bending tests of the tibiae showed significant results in females with a reduction in yield force and ultimate force driving lower work to yield and total work and a roughly 40 % reduction of stiffness. When tissue level parameters were estimated using beam theory, there was a significant reduction in yield and ultimate stresses as well as elastic modulus. The previously reported mechanistic similarity in the action of STZ on murine animals, as well as the ease of STZ administration via IP injection make this model is a strong candidate for future exploration of osteoporotic bone disease, Diabetes Mellitus, and the link between estrogen and glucose sensitivity.

Musculoskeletal complications in patients with diabetes mellitus

Musculoskeletal conditions are common in patients with diabetes. Several musculoskeletal disorders are viewed as chronic complications of diabetes because epidemiological studies have revealed high correlations between such complications and diabetes, but the pathophysiological links with diabetes remains unclear. Genetic predispositions, shared risk factors, microvascular impairments, progressive accumulation of advanced glycation end-products, and diabetic neuropathy may underlie the development of musculoskeletal disorders. Musculoskeletal complications of diabetics have received less attention than life-threatening microvascular or macrovascular complications. Here, we review several diabetic musculoskeletal complications with a focus on the clinical importance of early recognition and management, which would improve quality of life and physical function.

The interplay between diabetes mellitus and menopause: clinical implications

The menopausal transition is an impactful period in women's lives, when the risk of cardiovascular disease is accelerated. Similarly, diabetes mellitus profoundly impacts cardiovascular risk. However, the interplay between menopause and diabetes mellitus has not been adequately studied. The menopausal transition is accompanied by metabolic changes that predispose to diabetes mellitus, particularly type 2 diabetes mellitus (T2DM), as menopause results in increased risk of upper body adipose tissue accumulation and increased incidence of insulin resistance. Equally, diabetes mellitus can affect ovarian ageing, potentially causing women with type 1 diabetes mellitus and early-onset T2DM to experience menopause earlier than women without diabetes mellitus. Earlier age at menopause has been associated with a higher risk of T2DM later in life. Menopausal hormone therapy can reduce the risk of T2DM and improve glycaemic control in women with pre-existing diabetes mellitus; however, there is not enough evidence to support the administration of menopausal hormone therapy for diabetes mellitus prevention or control. This Review critically appraises studies published within the past few years on the interaction between diabetes mellitus and menopause and addresses all clinically relevant issues, such as the effect of menopause on the development of T2DM, and the management of both menopause and diabetes mellitus.

Fracture prediction tools in diabetes

PURPOSE OF REVIEW

Type 1 (T1D) and 2 diabetes (T2D) are associated with increased risk of fracture independent of bone mineral density (BMD). Fracture risk prediction tools can identify individuals at highest risk, and therefore, most likely to benefit from antifracture therapy. This review summarizes recent advances in fracture prediction tools as applied to individuals with diabetes.

RECENT FINDINGS

The Fracture Risk Assessment (FRAX) tool, Garvan Fracture Risk Calculator (FRC), and QFracture tool are validated tools for fracture risk prediction. FRAX is most widely used internationally, and considers T1D (but not T2D) under secondary osteoporosis disorders. FRAX underestimates fracture risk in both T1D and T2D. Trabecular bone score and other adjustments for T2D-associated risk improve FRAX-based estimations. Similar adjustments for T1D are not identified. Garvan FRC does not incorporate diabetes as an input but does includes falls. Garvan FRC slightly underestimates osteoporotic fracture risk in women with diabetes. QFracture incorporates both T1D and T2D and falls as input variables, but has not been directly validated in individuals with diabetes.

SUMMARY

Further research is needed to validate and compare available fracture prediction tools and their performance in individuals with diabetes.

Bone Microarchitecture and Strength in Long-Standing Type 1 Diabetes

Type 1 diabetes (T1DM) is associated with an increased fracture risk, specifically at nonvertebral sites. The influence of glycemic control and microvascular disease on skeletal health in long-standing T1DM remains largely unknown. We aimed to assess areal (aBMD) and volumetric bone mineral density (vBMD), bone microarchitecture, bone turnover, and estimated bone strength in patients with long-standing T1DM, defined as disease duration ≥25 years. We recruited 59 patients with T1DM (disease duration 37.7 ± 9.0 years; age 59.9 ± 9.9 years.; body mass index [BMI] 25.5 ± 3.7 kg/m² ; 5-year median glycated hemoglobin [HbA1c] 7.1% [IQR 6.82-7.40]) and 77 nondiabetic controls. Dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HRpQCT) at the ultradistal radius and tibia, and biochemical markers of bone turnover were assessed. Group comparisons were performed after adjustment for age, gender, and BMI. Patients with T1DM had lower aBMD at the hip (p < 0.001), distal radius (p = 0.01), lumbar spine (p = 0.04), and femoral neck (p = 0.05) as compared to controls. Cross-linked C-telopeptide (CTX), a marker of bone resorption, was significantly lower in T1DM (p = 0.005). At the distal radius there were no significant differences in vBMD and bone microarchitecture between both groups. In contrast, patients with T1DM had lower cortical thickness (estimate [95% confidence interval]: -0.14 [-0.24, -0.05], p < 0.01) and lower cortical vBMD (-28.66 [-54.38, -2.93], p = 0.03) at the ultradistal tibia. Bone strength and bone stiffness at the tibia, determined by homogenized finite element modeling, were significantly reduced in T1DM compared to controls. Both the altered cortical microarchitecture and decreased bone strength and stiffness were dependent on the presence of diabetic peripheral neuropathy. In addition to a reduced aBMD and decreased bone resorption, long-standing, well-controlled T1DM is associated with a cortical bone deficit at the ultradistal tibia with reduced bone strength and stiffness. Diabetic neuropathy was found to be a determinant of cortical bone structure and bone strength at the tibia, potentially contributing to the increased nonvertebral fracture risk. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Relation between the insulin lowering rate and changes in bone mineral density: Analysis among subtypes of type 1 diabetes mellitus

AIMS/INTRODUCTION

Bone mineral density (BMD) in patients with type 1 diabetes mellitus (T1DM) is reduced due to impaired insulin secretion. However, it is unclear whether the rate of BMD reduction is affected by T1DM subtypes. This study aimed to clarify the difference in BMD across T1DM subtypes: slowly progressive (SP), acute-onset (AO), and fulminant (F).

METHODS

This was a retrospective, single-center, cross-sectional study conducted on 98 adult T1DM patients. The main outcome included the BMD Z-score (BMD-Z) measured at the lumbar spine (LS) and femoral neck (FN).

RESULTS

The LS BMD-Z was lower in the AO than in the SP (p =0.03). No differences were observed when compared to the F. The FN BMD-Z tended to be higher in the SP than in the AO and F. Multiple regression analyses showed that the LS BMD-Z was associated with subtypes (AO vs. SP) (p =0.01), but not subtypes (F vs. SP), adjusted for sex, duration, retinopathy, and C-peptide immunoreactivity (CPR). When patients were divided into disease duration tertiles, in the first and second tertiles, the CPR levels were lower in the AO or F than in the SP. In contrast, LS and FN BMD-Z differed between the AO and SP only in the second tertiles (both p <0.01), with a similar tendency between the F and SP.

CONCLUSIONS

Among T1DM subtypes, BMD has time-dependent changes, which reveals that BMD decline follows impaired insulin secretion. These results provide novel insights into the association between the low insulin exposure duration and BMD.

The Impact of Diabetes on Osteoporosis Management and Secondary Fracture Risk After Primary Fragility Fractures: A Propensity Score-Matched Cohort Study

INTRODUCTION

Rates of osteoporosis evaluation and management after primary fragility fractures have remained low in recent years. The extent to which this treatment gap affects patients with diabetes is unclear. This study aimed to compare the risk of secondary fractures and rates of osteoporosis diagnosis and management after sentinel fractures in patients with and without diabetes.

METHODS

A propensity score-matched cohort study was conducted using the PearlDiver database. Patients aged 50 years and older with primary fragility fractures of the hip, wrist, spine, pelvis, humerus, and other locations were identified. Rates of secondary fractures, dual radiograph absorptiometry (DXA) scans, charted osteoporosis diagnoses (International Classification of Diseases, Ninth and Tenth Revisions), and osteoporosis pharmacotherapy within 2 years were compared for patients with and without diabetes using multivariable logistic regression.

RESULTS

Matching yielded 27,052 patients in each cohort. Index humerus fractures were more common in the diabetic cohort (15.0% versus 11.6%, P < 0.001), whereas wrist fractures were more prevalent among the nondiabetic cohort (15.2% versus 19.3%, P < 0.001). Incidence of secondary fractures at 2 years was higher for diabetic patients than nondiabetic patients (5.2% versus 4.7%; odds ratio [OR] 1.08; 95% confidence interval [CI], 0.99 to 1.17). Diabetic patients were significantly less likely to receive a DXA scan (13.2% versus 13.5%; OR 0.93; 95% CI, 0.88 to 0.98), be diagnosed with osteoporosis (9.3% versus 11.9%; OR 0.77; 95% CI, 0.73 to 0.82), or start pharmacotherapy (8.1% versus 8.7; OR 0.93; 95% CI, 0.87 to 0.99).

CONCLUSION

Despite diabetes being a well-established risk factor for fragility fractures, diabetic patients were significantly less likely to receive DXA scan evaluation, be formally diagnosed with osteoporosis, or be treated with osteoporosis pharmacotherapy after a sentinel fragility fracture. Incidence of secondary fractures within 2 years was also higher among diabetic patients.

Diabetic Bone Disease and Diabetic Myopathy: Manifestations of the Impaired Muscle-Bone Unit in Type 1 Diabetes

Type 1 diabetes is associated with complications affecting muscle and bone, with diabetic bone disease and diabetic myopathy becoming increasingly reported in the past few decades. This review is aimed at succinctly reviewing the literature on the current knowledge regarding these increasingly identified and possibly interconnected complications on the musculoskeletal system. Furthermore, this review summarizes several nonmechanical factors that could be mediating the development and progression of premature musculoskeletal decline in this population and discusses preventative measures to reduce the burden of diabetes on the musculoskeletal system.

The Association Between Diabetes Mellitus and Osteoarthritis: Does Diabetes Mellitus Play a Role in the Severity of Pain in Osteoarthritis?

Osteoarthritis (OA) is one of the most prevalent degenerative joint diseases, which results in the inevitable destruction of joints leading to pain and joint immobility. Some studies have reported a potential link between diabetes mellitus (DM) and the worsening symptoms and severity of OA. Based on our literature review, the microcellular environment of patients with DM showed accelerated joint destruction and increased inflammation in every anatomical aspect of the joint including the bones, tendons, ligaments, cartilage, and synovium. Additionally, the biomechanical and biochemical properties of these tissues were more severely impacted in patients with DM and OA compared to those without DM, suggesting that DM plays an important role in the pathogenesis of OA. Specifically, we found that advanced glycation end products (AGEs) are the key to inducing the acceleration of joint destruction; however, their role in the pathogenesis has yet to be fully mapped out. In this narrative review, we aim to explore the role that DM plays in the acceleration of OA leading to increased reports of joint pain in those with both diseases. We believe this topic of discussion to be important due to the increased prevalence of both diseases over the last several decades, potentially leading to an increased medical burden on both patients and the community at large.

The Comparative Study on the Status of Bone Metabolism and Thyroid Function in Diabetic Patients with or without Ketosis or Ketoacidosis

PURPOSE

This study aims to identify changes in bone turnover markers and thyroid function in diabetic ketosis (DK) and diabetic ketoacidosis (DKA).

MATERIALS AND METHODS

We compared data from the Department of Endocrinology at Shanghai Pudong Hospital from 2018 to 2020 on the pancreatic status and previous glucose control, bone transformation, calcium homeostasis, and thyroid function in groups with diabetes (DM alone, n=602), DK (n=232), and DKA (n=60). Similar comparisons were made in recurrent DK (A) (n=17) and single DK (A) (n=272).

RESULTS

The fasting C-peptide level decreased significantly, but hemoglobin A1c (HbA1c) levels were higher in DK or DKA (p<0.05). Blood calcium and 25-hydroxyvitamin D3 (25-OH-VitD3) levels were significantly lower in DKA (p<0.05), but parathyroid hormone (PTH) levels remained constant across all three groups. The N-terminal middle molecular fragment of osteocalcin (N-MID) and β-C terminal cross-linking telopeptide of type 1 collagen (β-CTX) showed significant inverse alterations in DKA, regardless of gender or age (p<0.05). Otherwise, DKA significantly inhibited thyroid function (p<0.05). Furthermore, Spearman correlation analyses revealed a relationship between N-MID and HbA1c in DM alone (r=-0.27, p<0.01), while total triiodothyronine (TT3, r=0.62, p<0.01) or free T3 (FT3, r=0.61, p<0.01) in DK, and DKA (TT3, r=0.45, p<0.01; FT3, r=0.43, p<0.01). Multilinear regression analyses revealed that β-CTX (β=0.564), HbA1c (β=-0.196), TT3 (β=0.183), and 25-OH-VitD3 (β=-0.120) were the only independent determinants of N-MID in DM, whereas FT3 (β=0.491), β-CTX (β=0.315) in DK, and FT3 (β=0.420), β-CTX (β=0.367), TG (β=-0.278) in DKA. Only 25-OH-VitD3 was found to be significantly lower in recurrent DK (A) than in single onset DK (A) (p<0.05), and β-CTX (β=0.745) was found to be significantly independently associated with N-MID.

CONCLUSION

Our preliminary findings show a dramatic change in bone turnover markers in DM patients with DK and DKA, and this change may be related to thyroid function.

Multimorbidity Among Adult Outpatients With Type 1 Diabetes in Germany

AIM

The aim of this cross-sectional retrospective study was to estimate the prevalence of different physical and psychiatric disorders as well as multimorbidity in outpatients with type 1 diabetes (T1D) in Germany.

METHODS

A total of 6967 adult patients with T1D from 958 general or diabetologist practices in Germany between January 2015 and December 2019 from the Disease Analyzer database (IQVIA) were included. The main outcome of the study was the prevalence of different diabetes-related and nondiabetes-related disorders within 12 months prior to the last outpatient visit. Multivariate logistic regression models were fitted with multimorbidity differently defined as >2, >3, >4, and >5 different disorders as a dependent variable and age, sex, glycated hemoglobin (HbA1c) values, and insulin pump therapy as impact variables.

RESULTS

Mean age (standard deviation [SD]) was 45.3 (16.7) years; 42.9% were women, the mean HbA1c was 7.9% (SD: 1.4%). The most frequent disorder was arterial hypertension (31.2%), followed by dyslipidemia (26.4%), dorsalgia (20.4%), diabetic neuropathy (17.3%), and depression (14.6%). The proportion of thyroid gland disorders, retinopathy, urethritis, iron deficiency anemia, and psychiatric disorders was higher in women than in men. Hypertension and mental and behavioral disorders due to the use of tobacco were higher in men. On average, each patient was diagnosed with 3.1 different disorders. Age had the strongest association with multimorbidity, followed by HbA1c value and female sex.

CONCLUSION

In summary, patients with T1D are often multimorbid, and the multimorbidity is associated with higher gender, female sex, and high HbA1c values. Understanding all of these factors can help practitioners create a risk profile for every patient.

Bone Density, Geometry, and Mass by Peripheral Quantitative Computed Tomography and Bone Turnover Markers in Children with Diabetes Mellitus Type 1

BACKGROUND

The type 1 diabetes mellitus (T1DM) is a chronic systemic autoimmune-mediated disease characterised by the insulin deficiency and hyperglycaemia. Its deleterious effect on bones concerns not only bone mass, density, and fracture risk but also may involve the linear growth of long bones. Studies on the lower leg in children with T1DM by pQCT have generated conflicting results, and most of the studies published so far focused only on a selected features of the bone. An additional information about growth, modelling, and remodelling processes can be gathered by the bone turnover marker measurement. The objective of the study was to evaluate bone mineral density, mass, and geometry using peripheral quantitative computed tomography as well as bone turnover markers in the patients with type 1 diabetes mellitus. Material and Methods. Bone mineral density, mass, and geometry on the lower leg using peripheral quantitative computed tomography and serum osteocalcin (OC) and carboxyterminal cross-linked telopeptide of type 1 collagen (CTx) were measured in 35 adolescents with T1DM (15 girls) aged 12.3-17.9 yrs. The results were compared to age- and sex-adjusted reference values for healthy controls.

RESULTS

Both sexes reveal lower than zero Z-scores for lower leg 66% total cortical bone cross-sectional area to muscle cross-sectional area ratio (-0.97 ± 1.02, p = 0.002517 and -0.98 ± 1.40, p = 0.007050, respectively) while tibia 4% trabecular bone density Z-score was lowered in boys (-0.67 ± 1.20, p = 0.02259). In boys in Tanner stage 5 bone mass and dimensions were diminished in comparison to Tanner stages 3 and 4, while in girls, such a phenomenon was not observed. Similarly, bone formation and resorption were decreased in boys but not in girls. Consistently, bone turnover markers correlated positively with bone size, dimensions, and strength in boys only.

CONCLUSIONS

T1DM patients revealed a decreased ratio of cortical bone area/muscle area, reflecting disturbed adaptation of the cortical shaft to the muscle force. When analyzing bone mass and dimensions, boys in Tanner stage 5 diverged from "less-mature" individuals, which may suggest that bone development in these individuals was impaired, affecting all three: mass, size, and strength. Noted in boys, suppressed bone metabolism may result in impairment of bone strength because of inadequate repair of microdamage and accumulation of microfractures.

Effect of gender, diabetes duration, inflammatory cytokines, and vitamin D level on bone mineral density among Thai children and adolescents with type 1 diabetes

INTRODUCTION

Type 1 diabetes mellitus (T1DM) is considered a risk factor for osteoporosis in adults; however, studies in bone mineral density (BMD) in children with T1DM reported conflicting results. The aim of this study was to compare BMD between T1DM youth and healthy controls, and to identify factors that affect BMD in T1DM youth.

METHODS

One hundred T1DM youths and 100 healthy controls (both groups aged 5-20 years) were recruited. BMD of total body, lumbar (L2-4), femoral neck, and total hip were assessed using dual energy X-ray absorptiometry. Blood investigations, including hemoglobin A_1c (HbA_1c), 25-hydroxyvitamin D, and inflammatory cytokines, were performed.

RESULTS

Forty-four boys and 56 girls with T1DM were enrolled [mean age 14.5 ± 2.7 years, median (IQR) duration of T1DM 5.80 (2.97-9.07) years, and mean HbA_{1c entire duration} 9.2 ± 1.4%]. T1DM girls had a lower height Z-score than control girls (p < 0.05), and 25-hydroxyvitamin D level was higher in T1DM youth than in controls (p < 0.001). After adjusting for pubertal status, height Z-score, and 25-hydroxyvitamin D, T1DM youth had a significantly lower lumbar BMD Z-score and femoral neck BMD than controls (p = 0.027 and p = 0.025, respectively). We also found that T1DM boys had a significantly lower lumbar BMD Z-score (p = 0.028), femoral neck BMD (p = 0.004), and total hip BMD (p = 0.016) than control boys. In contrast, these significant differences were not found in T1DM girls. Factors affecting BMD were different between T1DM boys and girls, and among different BMD sites. IL-13 was positively correlated with BMD in the total cohort and among girls. In boys - IL-2 and 25-hydroxyvitamin D were positively associated with BMD, and duration of diabetes was found to negatively affect BMD.

CONCLUSION

Deleterious effect of T1DM on BMD is gender specific. The longer the duration of T1DM, the greater the deficit in BMD found among boys with T1DM.

Effects of Advanced Glycation End Products on Differentiation and Function of Osteoblasts and Osteoclasts

BACKGROUND

Risk of fragility fractures increases in patients with diabetes mellitus, independent of bone mineral density. In the present study, the effects of advanced glycation end products (AGEs) on differentiation and function of osteoblasts and osteoclasts were investigated.

METHODS

AGEs and 25 mM glucose were administered to marrow-derived macrophages and MCT3T3-E1 cells. The effects of AGEs on osteoclast differentiation was investigated using tartrate-resistant acid phosphatase (TRAP) assay. The effects of AGEs on osteoblast differentiation was investigated using alkaline phosphatase (ALP) activity and bone nodule formation assays. Expression of osteoclast-specific and osteoblast-specific genes and effects on cell signaling pathways associated with cell differentiation were analyzed using reverse transcription polymerase chain reaction and western blotting.

RESULTS

AGEs significantly decreased TRAP-positive multinucleated cell formation in receptor activator of nuclear factor-κB ligand-induced marrow-derived macrophages in a dose-dependent manner. AGEs suppressed the expression of osteoclast-specific genes, JNK, p38, AKT, intercellular adhesion molecule 1, and lymphocyte function-associated antigen 1 in marrow-derived macrophages. AGEs decreased ALP activity and showed a tendency to decrease bone nodule formation in MC3T3-E1 cells. AGEs suppressed the expression of osteoblast-specific genes, lysyl hydroxylase and lysyl oxidase in MC3T3-E1 cells.

CONCLUSION

AGEs suppressed differentiation and function of osteoclasts and osteoblasts, and collagen cross-linking activity. It suggests that AGE may induce bone fragility through low bone turnover and deterioration of bone quality.

Association of hip fractures with cardiometabolic-renal risk factors in Southern Chinese patients with type 2 diabetes - the Hong Kong Diabetes Register

INTRODUCTION

Diabetes and bone health are closely related. We examined the incidence and risk factors of hip fractures in Chinese patients with type 2 diabetes (T2D).

MATERIALS AND METHODS

In this prospective cohort, we consecutively enrolled 22,325 adults with T2D above the age of 40 years in the Hong Kong Diabetes Register between 1994 and 2015 with crude hip fracture incidence rate censored in 2017.

RESULTS

At baseline, the mean age of this cohort was 60.9 ± 10.5 years (mean duration of diabetes 6 years, 52.4% male). During a mean ± standard deviation (SD) follow-up period of 8.7 ± 5.2 years with 193,553 person-years, 603 patients were hospitalized due to hip fractures with an incidence (95% confidence interval, CI) of 315.1 (290.4-341.3) per 100,000 person-years. On multivariable analysis with competing death risk adjusted, the independent hazard ratios (95% CI) for hip fractures in T2D were 2.01 (1.61-2.51) for female sex, 1.08 (1.07-1.09) for age, 0.93 (0.90-0.95) for body mass index, 1.52 (1.25-1.85) for albuminuria and 1.12 (1.02-1.23) for low density lipoprotein-cholesterol. In men, the 30-day, 1-year and 5-year post-hip fracture mortality rate (95% CI) were 5.8 (2.4-9.1) %, 29.2 (22.3-35.5) % and 65.9 (57.3-72.8) % respectively. The corresponding rates in women were 3.4 (1.6-5.1) %, 18.6 (14.7-22.4) %, and 46.8 (40.9-52.1) %.

CONCLUSIONS

Southern Chinese patients with T2D have a high risk of hip fracture associated with suboptimal cardiometabolic-renal risk factors and a high post-fracture mortality rate. The effects of improving modifiable risk factors on bone health warrants further evaluation.

Differences in the roles of types 1 and 2 diabetes in the susceptibility to the risk of fracture: a systematic review and meta-analysis

BACKGROUND

Diabetes mellitus (DM) causes excess risk of fracture at varied sites. Whereas, the difference between the roles of types 1 DM (T1DM) and 2 DM (T2DM) diabetes in the risk of fractures remains limited and inconclusive. We, therefore, conducted a meta-analysis to assess the differences for the associations of T1DM and T2DM with the risk of fractures.

METHODS

We systematically searched PubMed, Embase, and the Cochrane library for eligible studies until May 2021. The odds ratios (ORs) with 95% confidence intervals (CIs) were used to calculate the pooled effect estimates for the associations of T1DM and T2DM with the risk of fractures using the random-effects model. An indirect comparison results for the ratio of OR (ROR) with 95% CI were also applied to assess the difference between T1DM and T2DM with the risk of fractures.

RESULTS

Twenty-two cohort studies involving a total of 6,484,851 individuals were selected for meta-analysis. We noted that T1DM was associated with an increased risk of all fractures (OR: 1.72; 95% CI 1.36-2.19; P < 0.001), and fractures at the hip (OR: 4.01; 95% CI 2.90-5.54; P < 0.001), upper arm (OR: 2.20; 95% CI 1.61-3.00; P < 0.001), ankle (OR: 1.97; 95% CI 1.24-3.14; P = 0.004), and vertebrae (OR: 2.18; 95% CI 1.85-2.57; P < 0.001). Moreover, T2DM induced excess risk to all fractures (OR: 1.19; 95% CI 1.09-1.31; P < 0.001), including fractures at the hip (OR: 1.25; 95% CI 1.15-1.35; P < 0.001), upper arm (OR: 1.42; 95% CI 1.20-1.67; P < 0.001), and ankle (OR: 1.15; 95% CI 1.01-1.31; P = 0.029). Furthermore, we noted that T1DM versus T2DM was associated with greater risk to all fractures (ROR: 1.45; 95% CI 1.12-1.87; P = 0.005), including fractures at the hip (ROR: 3.21; 95% CI 2.30-4.48; P < 0.001), upper arm (ROR: 1.55; 95% CI 1.09-2.20; P = 0.015), and ankle (ROR: 1.71; 95% CI 1.06-2.78; P = 0.029).

CONCLUSIONS

This study found that T1DM caused an excess risk to all fractures, including fractures at the hip, upper arm, and ankle than T2DM. Further studies should therefore be conducted to directly compare the differences between T1DM and T2DM with the risk of fractures at various sites.

Bone accrual in children and adolescents with type 1 diabetes: current knowledge and future directions

PURPOSE OF REVIEW

Skeletal fragility is now recognized as a significant complication of type 1 diabetes (T1D). Many patients with T1D develop the disease in childhood and prior to the attainment of peak bone mass and strength. This manuscript will review recent studies investigating the effects of T1D on skeletal development.

RECENT FINDINGS

Mild-to-moderate deficits in bone density, structure, and mineral accrual were reported early in the course of T1D in some but not all studies. Childhood-onset disease was associated with a more severe skeletal phenotype in some adult studies. Lower than expected bone mass for muscle size was been described. Hemoglobin A1c was negatively associated with bone density and structure in several studies, though the mechanism was not clear.

SUMMARY

The use of advanced imaging techniques has shown that the adverse effects of T1D on the developing skeleton extend beyond bone density to include abnormalities in bone size, shape, microarchitecture, and strength. Despite these gains, a uniform understanding of the pathophysiology underlying skeletal fragility in this disorder remains elusive. Longitudinal studies, especially in association with interventions to reduce hyperglycemia or improve muscle strength, are needed to inform bone healthcare in T1D.

Mechanisms of altered bone remodeling in children with type 1 diabetes

Bone loss associated with type 1 diabetes mellitus (T1DM) begins at the onset of the disease, already in childhood, determining a lower bone mass peak and hence a greater risk of osteoporosis and fractures later in life. The mechanisms underlying diabetic bone fragility are not yet completely understood. Hyperglycemia and insulin deficiency can affect the bone cells functions, as well as the bone marrow fat, thus impairing the bone strength, geometry, and microarchitecture. Several factors, like insulin and growth hormone/insulin-like growth factor 1, can control bone marrow mesenchymal stem cell commitment, and the receptor activator of nuclear factor-κB ligand/osteoprotegerin and Wnt-b catenin pathways can impair bone turnover. Some myokines may have a key role in regulating metabolic control and improving bone mass in T1DM subjects. The aim of this review is to provide an overview of the current knowledge of the mechanisms underlying altered bone remodeling in children affected by T1DM.

Role of Insulin in Health and Disease: An Update

Insulin is a polypeptide hormone mainly secreted by β cells in the islets of Langerhans of the pancreas. The hormone potentially coordinates with glucagon to modulate blood glucose levels; insulin acts via an anabolic pathway, while glucagon performs catabolic functions. Insulin regulates glucose levels in the bloodstream and induces glucose storage in the liver, muscles, and adipose tissue, resulting in overall weight gain. The modulation of a wide range of physiological processes by insulin makes its synthesis and levels critical in the onset and progression of several chronic diseases. Although clinical and basic research has made significant progress in understanding the role of insulin in several pathophysiological processes, many aspects of these functions have yet to be elucidated. This review provides an update on insulin secretion and regulation, and its physiological roles and functions in different organs and cells, and implications to overall health. We cast light on recent advances in insulin-signaling targeted therapies, the protective effects of insulin signaling activators against disease, and recommendations and directions for future research.

Critical review of bone health, fracture risk and management of bone fragility in diabetes mellitus

The risk of fracture is increased in both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). However, in contrast to the former, patients with T2DM usually possess higher bone mineral density. Thus, there is a considerable difference in the pathophysiological basis of poor bone health between the two types of diabetes. Impaired bone strength due to poor bone microarchitecture and low bone turnover along with increased risk of fall are among the major factors behind elevated fracture risk. Moreover, some antidiabetic medications further enhance the fragility of the bone. On the other hand, antiosteoporosis medications can affect the glucose homeostasis in these patients. It is also difficult to predict the fracture risk in these patients because conventional tools such as bone mineral density and Fracture Risk Assessment Tool score assessment can underestimate the risk. Evidence-based recommendations for risk evaluation and management of poor bone health in diabetes are sparse in the literature. With the advancement in imaging technology, newer modalities are available to evaluate the bone quality and risk assessment in patients with diabetes. The purpose of this review is to explore the pathophysiology behind poor bone health in diabetic patients. Approach to the fracture risk evaluation in both T1DM and T2DM as well as the pragmatic use and efficacy of the available treatment options have been discussed in depth.

Diabetes and Osteoporosis: Part II, Clinical Management

Diabetes-induced osteoporosis is characterized by an increase in fracture risk. FRAX, the most widely used tool, underestimates the risk of fracture in both type 1 and type 2 diabetes. Specific adjustments to FRAX can help to better identify patients with diabetes at increased risk of fracture and select those at high fracture risk for treatment. Although clinical trial data are limited, the available evidence indicates that the presence of diabetes does not alter antiosteoporotic treatment response in patients with diabetes.

The diabetes-fracture association in women with type 1 and type 2 diabetes is partially mediated by falls: a 15-year longitudinal study

This study evaluated mediators of fracture risk in postmenopausal women with type 1 (T1D) and type 2 diabetes (T2D), over a 15-year follow-up period. This study provides evidence that the increased fracture risk in women with T1D or T2D is partially explained by falls. Furthermore, a shorter reproductive lifespan in women with T1D contributes modestly to fracture risk in this cohort.

PURPOSE

Skeletal fragility is associated with diabetes mellitus, while limited estrogen exposure during the reproductive years also predisposes to lower bone mass and higher fracture risk. We aimed to determine osteoporosis diagnosis, fall and fracture rates in women with type 1 (T1D) and type 2 (T2D) diabetes mellitus, and explore mediators of the diabetes-fracture relationship.

METHODS

Prospective observational data drawn from the Australian Longitudinal Study in Women's Health (ALSWH) from 1996 to 2010. Women were randomly selected from the national health insurance database. Standardized data collection occurred at six survey time points, with main outcome measures being self-reported osteoporosis, incident fracture, falls, and reproductive lifespan. Mediation analyses were performed to elucidate relevant intermediaries in the diabetes-fracture relationship.

RESULTS

Exactly 11,313 women were included at baseline (T1D, n = 107; T2D, n = 333; controls, n = 10,873). A total of 885 new cases of osteoporosis and 1099 incident fractures were reported over 15 years. Women with T1D or T2D reported more falls and fall-related injuries; additionally, women with T1D had a shorter reproductive lifespan. While fracture risk was increased in women with diabetes (T1D: OR 2.28, 95% CI 1.53-3.40; T2D: OR 2.40, 95% CI 1.90-3.03), compared with controls, adjustment for falls attenuated the risk of fracture by 10% and 6% in T1D and T2D, respectively. In women with T1D, reproductive lifespan modestly attenuated fracture risk by 4%.

CONCLUSION

Women with T1D and T2D have an increased risk of fracture, which may be partially explained by increased falls, and to a lesser extent by shorter reproductive lifespan, in T1D.

Association between type 1 diabetes mellitus and reduced bone mineral density in children: a meta-analysis

In this meta-analysis, we analyzed 9 cross-sectional studies for an association between type 1 diabetes mellitus (T1DM) and bone mineral density (BMD) in children. We found that BMD Z-scores were significantly reduced in children with T1DM.

INTRODUCTION

Recent cross-sectional studies have examined how T1DM influences bone health in children and adolescents, but the relationship between T1DM and BMD remains unclear due to conflicting reports.

METHODS

In this meta-analysis, we systematically searched PubMed, Cochrane library, and Web of Science databases (for publications through March 12, 2020), and calculated weight mean difference (WMD) along with 95% confidence intervals (CI) using a random-effects model. Heterogeneity was evaluated using the I² method. The Newcastle-Ottawa Scale was used to assess the quality of the included studies.

RESULTS

Data were analyzed from 9 eligible studies, including a total of 1522 children and adolescents. These data were tested for an association between T1DM and BMD. This analysis found a significant decrease in BMD Z-score in the whole body (pooled WMD, - 0.47, 95% CI, - 0.92 to - 0.02, I² = 80.2%) and lumbar spine (pooled WMD, - 0.41, 95% CI, - 0.69 to - 0.12, I² = 80.3%) in children and adolescents with T1DM, which was consistent in published studies from Asia and South America, but inconsistent in the North America and Europe. Importantly, the differences in BMD Z-scores were independent of age, level of glucose control (HbA1c), and prepubertal stage. Sensitivity analyses did not modify these findings. Funnel plot and the Egger test did not reveal significant publication bias.

CONCLUSION

This meta-analysis suggests that T1DM may play a role in decreasing BMD Z-scores in the whole body and lumbar spine in children.

Diabetes and Osteoporosis: Part I, Epidemiology and Pathophysiology

Both diabetes and osteoporosis are increasingly prevalent diseases, in part owing to aging populations worldwide. Epidemiologic data have shown that other organs may be adversely affected by diabetes, including the skeleton, in what has become known as diabetes-induced osteoporosis, which represents the combined impact of conventional osteoporosis with the additional fracture burden attributed to diabetes. There is an increased risk of fracture in patients with Type 1 and Type 2 diabetes, and some antidiabetic medications also may contribute to increased risk of fracture in diabetes.

Medical management of children with type 1 diabetes on low-carbohydrate or ketogenic diets

OBJECTIVES

Low-carbohydrate and ketogenic diets are becoming increasingly popular choices for people with type 1 diabetes (T1D) aiming to achieve optimal glycemic control. A carbohydrate-restricted diet in children has been associated with negative health effects including poor linear growth and inadequate bone mineralization. Guidelines for monitoring children and adolescents choosing to follow a carbohydrate-restricted diet do not exist. We aimed to create a clinical protocol outlining how to clinically and biochemically follow patients choosing a carbohydrate-restricted diet with the goal of medical safety.

METHODS

An interdisciplinary committee was formed and reviewed current consensus guidelines for pediatric patients on carbohydrate-restricted diets for epilepsy and metabolic disorders. A literature search was done to determine management strategies for children with T1D on a low-carbohydrate or ketogenic diet. Key health parameters that require monitoring were identified: growth, glycemic control, bone health, cardiometabolic health, and nutritional status. These health outcomes were used to develop a protocol for monitoring children on carbohydrate-restricted diets.

RESULTS

A one-page protocol for medical providers and educational materials for families interested in following a low-carbohydrate or ketogenic diet were developed and successfully implemented into clinical care.

CONCLUSION

Implementing a protocol for children on carbohydrate-restricted diets in clinic allows medical providers to ensure medical safety while being open to discussing a family's dietary preferences. Following children in the protocol over time will lead to informed clinical guidelines for patients with T1D who choose to follow a carbohydrate-restricted diet.

Association Between Parental Type 1 and Type 2 Diabetes Diagnosis and Major Osteoporotic Fracture Risk in Adult Offspring: A Population-Based Cohort Study

OBJECTIVES

Previous research suggests an intergenerational influence of diabetes on bone health. We examined the association between parental diabetes and major osteoporotic fracture (MOF) risk in offspring.

METHODS

This population-based cohort study used de-identified administrative health data from Manitoba, Canada, which capture population-level records of hospitalizations, physician visits and drug dispensations. The cohort included individuals 40⁺ years with at least 1 parent identified in the data between 1997 and 2015. The exposure was parental diagnosis of diabetes since 1970; the outcome was offspring incident MOF diagnosis of the hip, forearm, spine or humerus. Both measures were identified from hospital and physician visit records using validated case definitions. Multivariable Cox proportional hazards regression models tested the association of parental diabetes and offspring MOF risk.

RESULTS

The cohort included 279,085 offspring; 48.5% were females and 86.8% were ≤44 years of age. Both parents were identified for 89.4% of the cohort; 36.7% had a parental diabetes diagnosis. During a median follow up of 12.0 (interquartile range, 6.0 to 18.0) years, 8,762 offspring had a MOF diagnosis. After adjusting for fracture risk factors, parental diabetes diagnosis was not associated with MOF risk, whether diagnosed in fathers (adjusted hazard ratio [aHR], 1.02; 95% confidence interval [CI], 0.97 to 1.08), mothers (aHR, 1.02; 95% CI, 0.97 to 1.07) or both parents (aHR, 1.01; 95% CI, 0.93 to 1.11). The results remained consistent in a stratified analysis by offspring sex, secondary analysis based on MOF site and sensitivity analyses.

CONCLUSIONS

The results indicate parental diabetes is not associated with offspring MOF risk.

Prevalence of bone fracture and its association with severe hypoglycemia in Japanese patients with type 1 diabetes

INTRODUCTION

Type 1 diabetes (T1D) is associated with higher fracture risk. However, few studies have investigated the relationship between severe hypoglycemia and fracture risk in patients with T1D, and the results are controversial. Besides, none has investigated the risk factors for fracture in Asian patients with T1D. The aim of the present study was to investigate the prevalence of bone fracture and its relationship between severe hypoglycemia and other risk factors in Japanese patients with T1D.

RESEARCH DESIGN AND METHODS

The single-center cross-sectional study enrolled 388 Japanese patients with T1D (mean age, 45.2 years; women, 60.4%; mean duration of diabetes, 16.6 years) between October 2019 and April 2020. The occurrence and circumstances of any fracture after the diagnosis of T1D were identified using a self-administered questionnaire. The main outcomes were any anatomic site of fracture and fall-related fracture. Severe hypoglycemia was defined as an episode of hypoglycemia that required the assistance of others to achieve recovery.

RESULTS

A total of 92 fractures occurred in 64 patients, and 59 fractures (64%) were fall-related. Only one participant experienced fracture within the 10 years following their diagnosis of diabetes. In logistic regression analysis, the multivariate-adjusted ORs (95% CIs) of a history of severe hypoglycemia were 2.11 (1.11 to 4.09) for any fracture and 1.91 (0.93 to 4.02) for fall-related fracture. Fourteen of 18 participants with multiple episodes of any type of fracture had a history of severe hypoglycemia (p<0.001 vs no fracture).

CONCLUSIONS

We have shown that a history of severe hypoglycemia is significantly associated with a higher risk of bone fracture in Japanese patients with T1D.

Association of Triglyceride-Glucose Index with Bone Mineral Density in Non-diabetic Koreans: KNHANES 2008-2011

The association of insulin resistance (IR), as indicated by the homeostasis model assessment of insulin resistance, with bone metabolism is yet to be clarified. We aimed to investigate the relationship of IR with bone mass by using the triglyceride-glucose (TyG) index as an alternative marker of IR. Data of 4810 non-diabetes individuals (2552 men aged ≥ 50 years and 2258 postmenopausal women) from the Korean National Health and Nutritional Examination Survey IV and V were analyzed. Bone mineral density (BMD) at the lumbar spine, femoral neck, total hip, and whole body were measured using dual-energy X-ray absorptiometry. After adjusting for confounding factors, there were inverse relationships of TyG index with femoral neck, total hip, and whole body BMD in men (β =  - 0.085, P < 0.001 at femoral neck; β =  - 0.046, P = 0.037 at total hip; β =  - 0.098, P < 0.001 at whole body). However, in women, femoral neck and whole body BMD were negatively associated with the TyG index (β =  - 0.071, P = 0.008 at femoral neck and β =  - 0.065, P = 0.005 at whole body). The highest TyG index tertile exhibited reduced femoral neck BMD in both sexes (P = 0.003 in men and P = 0.013 in women) and reduced whole body BMD in men (P < 0.001) after adjusting for confounders. When the study subjects were divided into BMI (body mass index) < 23 kg/m² and ≥ 23 kg/m² groups, the TyG index was significantly associated with femoral neck BMD only in the women with BMI < 23 kg/m² (P = 0.009). We observed a significant association between the highest TyG index tertile and low bone mass at the femoral neck in women with BMI < 23 kg/m² (P = 0.003) that was not observed in women with BMI ≥ 23 kg/m² and men. In conclusion, IR evaluated using the TyG index was inversely associated with femoral neck BMD in non-diabetic men aged ≥ 50 years and postmenopausal women. The negative influence of IR on femoral neck BMD was robust in the women with BMI < 23 kg/m². This indicates a differential effect of IR on BMD according to skeletal site, sex, and BMI.

Fracture risk assessment (FRAX) without BMD and risk of major osteoporotic fractures in adults with type 1 diabetes

OBJECTIVE

To evaluate the association between Fracture Risk Assessment Tool (FRAX) without bone mineral density (BMD) and risk for major osteoporotic fractures (MOF) in type 1 diabetes.

METHODS

Subjects with type 1 diabetes and without diabetes from the 'Coronary Artery Calcification in Type 1 Diabetes' study were included. Risk for MOF was calculated using FRAX-based clinical risk factors and without BMD at visit 3 (2006-2008). Incident fractures were defined as fractures that occurred between visit 3 and visit 4 (2013-2017). Survival models were used to study the predictability of new MOF by diabetes status.

RESULTS

346 type 1 diabetes (mean age 43.3 ± 9, BMI 26.4 ± 5, diabetes duration 29.4 ± 8.6 years, A1c 7.8 ± 1.1) and 411 controls (mean age 46.9 ± 9 years, BMI 26.3 ± 5 kg/m², A1c 5.5 ± 0.4) were analyzed in this study. In unadjusted survival analysis, the FRAX score without BMD was significantly associated with MOF (HR 1.08, 95% CI: 1.04-1.13, p < 0.0001), and remained significantly associated after adjustment for age and sex (HR 1.09, 95% CI: 1.04-1.15, p = 0.0007) and type 1 diabetes (HR 1.08, 95% CI: 1.04-1.12, p = 0.0002). In the fully adjusted model (adjusted for age, sex and type 1 diabetes), the FRAX score without BMD was the only variable significantly associated with risk of MOF (HR 1.08, 95% CI: 1.02-1.14, p = 0.006).

CONCLUSION

Clinical use of FRAX without BMD is useful tool in identifying adults with type 1 diabetes at higher risk for MOF risk and may help clinicians to guide therapeutic decision-making in this high fracture risk population.

Bone turnover and metabolite responses to exercise in people with and without long-duration type 1 diabetes: a case-control study

INTRODUCTION

Exercise acutely alters markers of bone resorption and formation. As risk of fracture is increased in patients with type 1 diabetes, understanding if exercise-induced bone turnover is affected within this population is prudent. We assessed bone turnover responses to acute exercise in individuals with long-duration type 1 diabetes and matched controls.

RESEARCH DESIGN AND METHODS

Participants with type 1 diabetes (n=15; age: 38.7±13.3; glycosylated hemoglobin: 60.5±6.7 mmol/mol; diabetes duration: 19.3±11.4 years) and age-matched, fitness-matched, and body mass index-matched controls (n=15) completed 45 min of incline walking (60% peak oxygen uptake). Blood samples were collected at baseline and immediately, 30 min, and 60 min postexercise. Markers of bone resorption (β-C-terminal cross-linked telopeptide of type 1 collagen, β-CTx) and formation (procollagen type-1 amino-terminal propeptide, P1NP), parathyroid hormone (PTH), phosphate, and calcium (albumin-adjusted and ionized) were measured. Data (mean±SD) were analyzed by a mixed-model analysis of variance.

RESULTS

Baseline concentrations of P1NP and β-CTx were comparable between participants with type 1 diabetes and controls. P1NP did not change with exercise (p=0.20) but β-CTx decreased (p<0.001) in both groups, but less so in participants with type 1 diabetes compared with controls (-9.2±3.7%; p=0.02). PTH and phosphate increased immediately postexercise in both groups; only PTH was raised at 30 min postexercise (p<0.001), with no between-group differences (p>0.39). Participants with type 1 diabetes had reduced albumin and ionized calcium at all sample points (p<0.01).

CONCLUSIONS

Following exercise, participants with type 1 diabetes displayed similar time-course changes in markers of bone formation and associated metabolites, but an attenuated suppression in bone resorption. The reduced albumin and ionized calcium may have implications for future bone health. Further investigation of the interactions between type 1 diabetes, differing modalities and intensities of exercise, and bone health is warranted.

Impact of Type 1 Diabetes Mellitus on Skeletal Integrity and Strength in Adolescents as Assessed by HRpQCT

Adults with type 1 diabetes mellitus (T1DM) are at risk of premature osteoporosis and fractures. The onset of T1DM typically starts during childhood and adolescence. Thus, the effects of DM on the skeleton may be established during this period. Studies in children with T1DM primarily use DXA with conflicting results. We present the first study in adolescents assessing the impact of T1DM on skeletal microstructure and strength using HRpQCT. We recruited 22 patients aged 12 to 16 years with T1DM who were matched by age, gender, and pubertal stage with healthy controls. Paired t tests were applied to assess differences in cortical and trabecular microarchitecture measurements from HRpQCT, and skeletal strength from HRpQCT-derived microfinite element analysis. Subtotal body, lumbar, and pelvic parameters were assessed using DXA. There was no significant difference in subtotal body, lumbar spine, and pelvic BMD between T1DM and control pairs. However, tibial trabecular thickness was lower (-0.005 mm; 95% CI, -0.01 to -0.001; p = 0.029) and trabecular loading was lower at the distal radius (ratio of the load taken by the trabecular bone in relation to the total load at the distal end (Tb.F/TF) distal: -6.2; 95% CI, -12.4 to -0.03; p = 0.049), and distal and proximal tibia (Tb.F/TF distal: -5.2, 95% CI, -9.2 to -1.2; p = 0.013; and Tb.F/TF proximal: -5.0, 95% CI, -9.8 to -0.1; p = 0.047) in T1DM patients. A subanalysis of radial data of participants with duration of T1DM of at least 2 years and their matched controls demonstrated a reduced trabecular bone number (-0.15, 95% CI, -0.26 to -0.04; p = 0.012), increased trabecular separation (0.041 mm, 95% CI, 0.009-0.072; p = 0.015), an increased trabecular inhomogeneity (0.018, 95% CI, 0.003-0.034; p = 0.021). Regression models demonstrated a reduction in tibial stiffness (-0.877 kN/mm; p = 0.03) and tibial failure load (-0.044 kN; p = 0.03) with higher HbA1C. Thus, in adolescents with T1DM, detrimental changes are seen in tibial and radial microarchitecture and tibial and radial strength before changes in DXA occur and may result from poor diabetic control. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Osteoporosis in Premenopausal Women: A Clinical Narrative Review by the ECTS and the IOF

CONTEXT

Consensus regarding diagnosis and management of osteoporosis in premenopausal women (PW) is still lacking due to few studies carried out in this population.

DESIGN

The European Calcified Tissue Society and the International Osteoporosis Foundation convened a working group to produce an updated review of literature published after 2017 on this topic.

RESULTS

Fragility fractures in PW are rare and mostly due to secondary osteoporosis (ie, in presence of an underlying disease such as hormonal, inflammatory, or digestive disorders). In absence of another disorder, low bone mineral density (BMD) together with fragility fractures qualifies as idiopathic osteoporosis. In contrast, low BMD alone does not necessarily represent osteoporosis in absence of bone microarchitectural abnormalities. BMD increases in PW with osteoporosis when the underlying disease is treated. For example, in celiac disease, an increase of 9% in radius trabecular volumetric density was achieved after 1 year of gluten-free diet, while anti-tumor necrosis factor alpha improved BMD in PW with inflammatory bowel diseases. In amenorrhea, including anorexia nervosa, appropriately delivered estrogen replacement therapy can also improve BMD. Alternatively, antiresorptive or anabolic therapy has been shown to improve BMD in a variety of conditions, the range of improvement (3%-16%) depending on skeletal site and the nature of the secondary cause. No studies were powered to demonstrate fracture reduction. The effects of bisphosphonates in childbearing women have been scantly studied and caution is needed.

CONCLUSION

The majority of PW with osteoporosis have an underlying disease. Specific therapy of these diseases, as well as antiresorptive and anabolic drugs, improve BMD, but without evidence of fracture reduction.

Lower estimated bone strength and impaired bone microarchitecture in children with type 1 diabetes

INTRODUCTION

Patients with type 1 diabetes has an increased risk of fracture. We wished to evaluate estimated bone strength in children and adolescents with type 1 diabetes and assess peripheral bone geometry, volumetric bone mineral density (vBMD) and microarchitecture.

RESEARCH DESIGN AND METHODS

In a cross-sectional study, high-resolution peripheral quantitative CT (HR-pQCT) was performed of the radius and tibia in 84 children with type 1 diabetes and 55 healthy sibling controls. Estimated bone strength was assessed using a microfinite element analysis solver. Multivariate regression analyses were performed adjusting for age, sex, height and body mass index.

RESULTS

The median age was 13.0 years in the diabetes group vs 11.5 years in healthy sibling controls. The median (range) diabetes duration was 4.2 (0.4-15.9) years; median (range) latest year Hb1Ac was 7.8 (5.9-11.8) % (61.8 (41-106) mmol/mol). In adjusted analyses, patients with type 1 diabetes had reduced estimated bone strength in both radius, β -390.6 (-621.2 to -159.9) N, p=0.001, and tibia, β -891.9 (-1321 to -462.9) N, p<0.001. In the radius and tibia, children with type 1 diabetes had reduced cortical area, trabecular vBMD, trabecular number and trabecular bone volume fraction and increased trabecular inhomogeneity, adjusted p<0.05 for all. Latest year HbA1c was negatively correlated with bone microarchitecture (radius and tibia), trabecular vBMD and estimated bone strength (tibia).

CONCLUSION

Children with type 1 diabetes had reduced estimated bone strength. This reduced bone strength could partly be explained by reduced trabecular bone mineral density, adverse microarchitecture and reduced cortical area. We also found increasing latest year HbA1c to be associated with several adverse changes in bone parameters. HR-pQCT holds potential to identify early adverse bone changes and to explain the increased fracture risk in young patients with type 1 diabetes.

Blockade of the colony-stimulating factor-1 receptor reverses bone loss in osteoporosis mouse models

BACKGROUND

Mice lacking either colony-stimulating factor-1 (CSF-1) or its receptor, CSF-1R, display osteopetrosis. Accordingly, genetic deletion or pharmacological blockade of CSF-1 prevents the bone loss associated with estrogen deficiency. However, the role of CSF-1R in osteoporosis models of type-1 diabetes (T1D) and ovariectomy (OVX) has not been examined. Thus, we evaluated whether CSF-1R blockade would relieve the bone loss in a model of primary osteoporosis (female mice with OVX) and a model of secondary osteoporosis (female with T1D) using micro-computed tomography.

METHODS

Female ICR mice at 10 weeks underwent OVX or received five daily administrations of streptozotocin (ip, 50 mg/kg) to induce T1D. Four weeks after OVX and 14 weeks after first injection of streptozotocin, mice received an anti-CSF-1R (2G2) antibody (10 mg/kg, ip; once/week for 6 weeks) or vehicle. At the last day of antibody administration, mice were sacrificed and femur and tibia were harvested for micro-computed tomography analysis.

RESULTS

Mice with OVX had a significant loss of trabecular bone at the distal femoral and proximal tibial metaphysis. Chronic treatment with anti-CSF-1R significantly reversed the trabecular bone loss at these anatomical sites. Streptozotocin-induced T1D resulted in significant loss of trabecular bone at the femoral neck and cortical bone at the femoral mid-diaphysis. Chronic treatment with anti-CSF-1R antibody significantly reversed the bone loss observed in mice with T1D.

CONCLUSION

Our results demonstrate that blockade of CSF-1R signaling reverses bone loss in two different mouse models of osteoporosis.