In vivo Labeling of Bone Microdamage in an Animal Model of Type 1 Diabetes Mellitus

Gender-Specific Risk Factors for Asymmetric Bone Density in Adult Degenerative Lumbar Scoliosis: A Retrospective Cohort Analysis

BACKGROUND This study aimed to evaluate the performance of Hounsfield Unit (HU) value on the vertebral bone mineral density associated with adult degenerative lumbar scoliosis (ADLS) and to compare the HU and coronal height changes of the lumbar spine on the concave and convex sides. The secondary aim was to investigate the risk factors for increased asymmetric ratio of HU (ARH) by concave-to-convex. MATERIAL AND METHODS A total of 74 patients aged ≥50 years were retrospectively reviewed. The height and the HU values of the region of interest were measured and compared. Multiple linear regression and gender-stratified analyses were performed to explore risk factors. Restricted cubic spline (RCS) was used to visually assess the dose-effect relationship between the Cobb angle and ARH. RESULTS The heights on the concave sides were significantly lower while HU values were significantly higher than that of the convex side. Cobb angle (95% CI: 0.001 to 0.009, P=0.034) was positively correlated with the increased ARH, while apex orientation to the right (95% CI: -0.152 to -0.013, P=0.022) was negatively associated. Gender-stratified analyses showed age and apex vertebrae location are 2 additional risk factors in male patients but not in female patients. Cobb angle was identified by RCS as a risk factor both in males and females and the inflection points were 15 and 17.5, respectively. CONCLUSIONS HU values on the concave side are significantly higher than on the convex side, showing the asymmetrical bone mass distribution of ADLS patients. Several gender-related risk factors for increased ARH have been identified.

Advanced glycation and glycoxidation end products in bone

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

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.

Effect of non-enzymatic glycation on collagen nanoscale mechanisms in diabetic and age-related bone fragility

Age and diabetes have long been known to induce an oxidative reaction between glucose and collagen, leading to the accumulation of advanced glycation end-products (AGEs) cross-links in collagenous tissues. More recently, AGEs content has been related to loss of bone quality, independent of bone mass, and increased fracture risk with aging and diabetes. Loss of bone quality is mostly attributed to changes in material properties, structural organization, or cellular remodeling. Though all these factors play a role in bone fragility disease, some common recurring patterns can be found between diabetic and age-related bone fragility. The main pattern we will discuss in this viewpoint is the increase of fibrillar collagen stiffness and loss of collagen-induced plasticity with AGE accumulation. This study focused on recent related experimental studies and discusses the correlation between fluorescent AGEs content at the molecular and fibrillar scales, collagen deformation mechanisms at the nanoscale, and resistance to bone fracture at the macroscale.

A new ex vivo model of the bone tissue response to the hyperglycemic environment - The embryonic chicken femur organotypic culture in high glucose conditions

Diabetes mellitus (DM) embrace a group of chronic metabolic conditions with a high morbidity, causing deleterious effects in different tissues and organs, including bone. Hyperglycemia seems to be one of the most contributing etiological factors of bone-related alterations, altering metabolic functionality and inducing morphological adaptations. Despite the established models for the assessment of bone functionality in hyperglycemic conditions, in vitro studies present a limited representativeness given the imperfect cell-cell and cell-matrix interactions, and restricted three-dimensional spatial arrangement; while in vivo studies raise ethical issues and offer limited mechanistic characterization, given the modulatory influence of many systemic factors and/or regulatory systems. Accordingly, the aim of this study is to establish and characterize an innovative ex vivo model of the bone tissue response to hyperglycemia, reaching hand of the organotypic culture of embryonic chicken femurs in high glucose conditions, showcasing the integrative responsiveness of the model regarding hyperglycemia-induced alterations. A thorough assessment of the cellular and tissue functionality was further conducted. Results show that, in high glucose conditions, femurs presented an increased cell proliferation and enhanced collagen production, despite the altered protein synthesis, substantiated by the increased carbonyl content. Gene expression analysis evidenced that high glucose levels induced the expression of pro-inflammatory and early osteogenic markers, further impairing the expression of late osteogenic markers. Furthermore, the tissue morphological organization and matrix mineralization were significantly altered by high glucose levels, as evidenced by histological, histochemical and microtomographic evaluations. Attained data is coherent with acknowledged hyperglycemia-induced bone tissue alterations, validating the models' effectiveness, and evidencing its integrative responsiveness regarding cell proliferation, gene and protein expression, and tissue morpho-functional organization. The assessed ex vivo model conjoins the capability to access both cellular and tissue outcomes in the absence of a systemic modulatory influence, outreaching the functionality of current experimental in vitro and in vivo models of the diabetic bone condition.