Spatiotemporal characterization of microdamage accumulation and its targeted remodeling mechanisms in diabetic fatigued bone

Chromium Picolinate Regulates Bone Metabolism and Prevents Bone Loss in Diabetic Rats

Diabetic osteoporosis (DOP) is an abnormal metabolic disease caused by long-term hyperglycemia. In this study, a model rat of streptozotocin (STZ)-induced diabetes was established, and chromium picolinate (5 mg·kg-1) was given; the changes in blood glucose and body weight were detected before and after administration; and bone mineral density (BMD), bone morphology, bone turnover markers, inflammatory cytokines, and oxidative stress indicators were observed in each group. We found that after chromium picolinate (CP) intervention for 8 weeks, the blood glucose level was decreased; the BMD, the bone histomorphology parameters, and the pathological structure were improved; the expression of bone resorption-related proteins was downregulated; and the expression of bone formation-related proteins was upregulated. Meanwhile, serum antioxidant activity was increased, and inflammatory cytokine levels were decreased. In conclusion, CP could alleviate DOP by anti-oxidation, inhibition of bone turnover, anti-inflammation, and regulation of the OPG/RANKL/RANK signaling pathway. Therefore, CP has important application values for further development as a functional food or active medicine in DOP treatment.

Early protection against bone stress injuries by mobilization of endogenous targeted bone remodeling

Bone stress injuries are common overuse injuries, especially in soldiers, athletes, and performers. In contrast to various post-injury treatments, early protection against bone stress injuries can provide greater benefit. This study explored the early protection strategies against bone stress injuries by mobilization of endogenous targeted bone remodeling. The effects of various pharmaceutical/biophysical approaches, individual or combinational, were investigated by giving intervention before fatigue loading. We optimized the dosage and administration parameters and found that early intervention with pulsed electromagnetic field and parathyroid hormone (i.e., PEMF+PTH) resulted in the most pronounced protective effects among all the approaches against the bone stress injuries. In addition, the mechanisms by which the strategy mobilizes targeted bone remodeling and enhances the self-repair capacity of bone were systematically investigated. This study proposes strategies to reduce the incidence of bone stress injuries in high-risk populations (e.g., soldiers and athletes), particularly for those before sudden increased physical training.

Osteocyte apoptosis and cellular micropetrosis signify skeletal aging in type 1 diabetes

Bone fragility is a profound complication of type 1 diabetes mellitus (T1DM), increasing patient morbidity. Within the mineralized bone matrix, osteocytes build a mechanosensitive network that orchestrates bone remodeling; thus, osteocyte viability is crucial for maintaining bone homeostasis. In human cortical bone specimens from individuals with T1DM, we found signs of accelerated osteocyte apoptosis and local mineralization of osteocyte lacunae (micropetrosis) compared with samples from age-matched controls. Such morphological changes were seen in the relatively young osteonal bone matrix on the periosteal side, and micropetrosis coincided with microdamage accumulation, implying that T1DM drives local skeletal aging and thereby impairs the biomechanical competence of the bone tissue. The consequent dysfunction of the osteocyte network hampers bone remodeling and decreases bone repair mechanisms, potentially contributing to the enhanced fracture risk seen in individuals with T1DM. STATEMENT OF SIGNIFICANCE: Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease that causes hyperglycemia. Increased bone fragility is one of the complications associated with T1DM. Our latest study on T1DM-affected human cortical bone identified the viability of osteocytes, the primary bone cells, as a potentially critical factor in T1DM-bone disease. We linked T1DM with increased osteocyte apoptosis and local accumulation of mineralized lacunar spaces and microdamage. Such structural changes in bone tissue suggest that T1DM speeds up the adverse effects of aging, leading to the premature death of osteocytes and potentially contributing to diabetes-related bone fragility.

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.

Improved fatigue properties, bone microstructure and blood glucose in type 2 diabetic rats with verapamil treatment

BACKGROUND

Type 2 diabetes mellitus is a global epidemic disease, which leads to a severe complication named increased bone fracture risk. This study aimed to explore if verapamil treatment could improve bone quality of type 2 diabetes mellitus.

METHODS

Rat models of control, diabetes and verapamil treatment with 4/12/24/48 mg/kg/d were established, respectively. Blood glucose was monitored during 12-week treatment, and bilateral tibiae were collected. Microstructural images of bilateral metaphyseal cancellous bone and high-resolution images of cortical bone of left tibial shafts were obtained by micro-computed tomography. Fatigue properties of bone were evaluated via cyclic compressive tests of right tibial shafts.

FINDINGS

Verapamil treatment had no significant effect on blood glucose, but blood glucose tended to decline with the increase of verapamil-treated time and dose. Compared with controls, osteocyte lacunar and canal porosities in diabetes and verapamil-treated groups were significantly decreased (P < 0.05), trabecular separation and degree of anisotropy were significantly increased (P < 0.05), while trabecular tissue mineral density, trabecular bone volume fraction and trabecular number in verapamil-treated (48 mg/kg/d) group were significantly higher than those in diabetes (P < 0.05). Compared with diabetes, initial compressive elastic moduli in verapamil-treated (12/24/48 mg/kg/d) groups were significantly increased (P < 0.05), while secant modulus degradations in verapamil-treated (24/48 mg/kg/d) groups were significantly decreased (P < 0.05).

INTERPRETATION

Verapamil could improve bone microstructure and fatigue properties in type 2 diabetic rats; and high-dose verapamil presented a significant effect on improving bone quality. These findings provided a new possibility for preventing the high bone fracture risk of type 2 diabetes mellitus in clinics.

Bone fragility in diabetes: novel concepts and clinical implications

Increased fracture risk represents an emerging and severe complication of diabetes. The resulting prolonged immobility and hospitalisations can lead to substantial morbidity and mortality. In type 1 diabetes, bone mass and bone strength are reduced, resulting in up to a five-times greater risk of fractures throughout life. In type 2 diabetes, fracture risk is increased despite a normal bone mass. Conventional dual-energy x-ray absorptiometry might underestimate fracture risk, but can be improved by applying specific adjustments. Bone fragility in diabetes can result from cellular abnormalities, matrix interactions, immune and vascular changes, and musculoskeletal maladaptation to chronic hyperglycaemia. This Review summarises how the bone microenvironment responds to type 1 and type 2 diabetes, and the mechanisms underlying fragility fractures. We describe the value of novel imaging technologies and the clinical utility of biomarkers, and discuss current and future therapeutic approaches that protect bone health in people with diabetes.

Fracture risk assessment in diabetes mellitus

Growing evidence suggests that diabetes mellitus is associated with an increased risk of fracture. Bone intrinsic factors (such as accumulation of glycation end products, low bone turnover, and bone microstructural changes) and extrinsic factors (such as hypoglycemia caused by treatment, diabetes peripheral neuropathy, muscle weakness, visual impairment, and some hypoglycemic agents affecting bone metabolism) probably contribute to damage of bone strength and the increased risk of fragility fracture. Traditionally, bone mineral density (BMD) measured by dual x-ray absorptiometry (DXA) is considered to be the gold standard for assessing osteoporosis. However, it cannot fully capture the changes in bone strength and often underestimates the risk of fracture in diabetes. The fracture risk assessment tool is easy to operate, giving it a certain edge in assessing fracture risk in diabetes. However, some parameters need to be regulated or replaced to improve the sensitivity of the tool. Trabecular bone score, a noninvasive tool, indirectly evaluates bone microstructure by analyzing the texture sparsity of trabecular bone, which is based on the pixel gray level of DXA. Trabecular bone score combined with BMD can effectively improve the prediction ability of fracture risk. Quantitative computed tomography is another noninvasive examination of bone microstructure. High-resolution peripheral quantitative computed tomography can measure volume bone mineral density. Quantitative computed tomography combined with microstructure finite element analysis can evaluate the mechanical properties of bones. Considering the invasive nature, the use of microindentation and histomorphometry is limited in clinical settings. Some studies found that the changes in bone turnover markers in diabetes might be associated with fracture risk, but further studies are needed to confirm this. This review focused on summarizing the current development of these assessment tools in diabetes so as to provide references for clinical practice. Moreover, these tools can reduce the occurrence of fragility fractures in diabetes through early detection and intervention.

A Potential Participant in Type 2 Diabetes Bone Fragility: TIMP-1 at Sites of Osteocyte Lacunar-Canalicular System

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of bone fracture, but the bone mineral density (BMD) is typically normal or higher in such patients. Because the fracture risk is independent of reduced BMD, bone fragility in T2DM may be partially due to poor bone quality. The mechanisms triggering bone quality abnormalities in T2DM are complex, and include the accumulation of advanced glycation end-products, the increased inflammation, and low bone turnover. Matrix metalloproteinases (MMPs) in bone can hydrolyze the bone matrix. Tissue inhibitors of MMPs (TIMPs) can inhibit the activity of MMPs. Both MMPs and TIMPs participate in mediating bone quality. Among all types of TIMPs, TIMP-1 is mostly reportedly increased in the serum of T2DM patients. Because osteocytes can express TIMP-1, and osteocyte pericellular matrix influences bone quality partially regulated by perilacunar/canalicular remodeling, we hypothesized that TIMP-1 at sites of osteocyte lacunar-canalicular system is involved in T2DM bone fragility.

Osteocytes and Diabetes: Altered Function of Diabetic Osteocytes

PURPOSE OF REVIEW

Diabetes mellitus is a prevalent chronic disease affecting millions of people in the world. Bone fragility is a complication found in diabetic patients. Although osteoblasts and osteoclasts are directly affected by diabetes, herein we focus on how the diabetic state-based on hyperglycemia and accumulation of advanced glycation end products among other features-impairs osteocyte functions exerting deleterious effects on bone.

RECENT FINDINGS

In the last years, several studies described that diabetic conditions cause morphological modifications on lacunar-canalicular system, alterations on osteocyte mechanoreceptors and intracellular pathways and on osteocyte communication with other cells through the secretion of proteins such as sclerostin or RANKL. This article gives an overview of events occurring in diabetic osteocytes. In particular, mechanical responses seem to be seriously affected in these conditions, suggesting that mechanical sensibility could be a target for future research in the field.