Chronic Hyperglycemia Modulates Rat Osteoporotic Cortical Bone Microarchitecture into Less Fragile Structures

The Effect of Ceratonia siliqua Supplement on Bone Mineral Density in Ovariectomy-induced Osteoporosis in Rats

AIM

This study aimed to investigate the effect of Ceratonia siliqua on bone mineral density (BMD) as a non-pharmaceutical alternative treatment for postmenopausal osteoporosis.

MATERIALS AND METHODS

Thirty mature female Wistar rats were randomly separated into three groups of 10: Control, ovariectomized (OVX), and ovariectomized-plus-C. siliqua (OVX+CS). Total and proximal BMD were measured by dual-energy X-ray absorptiometry (DEXA) in all groups before ovariectomy, and at 3 and 6 months postoperatively. At the end of the study, the femurs were subjected to a three-point bending test.

RESULTS

DEXA revealed no statistically significant difference in absolute values or percentage changes for total tibial BMD between OVX+CS and OVX groups throughout the study. In the proximal tibia, both absolute values and BMD percentage changes from baseline were higher in the OVX+CS group compared to the OVX group after 3 and 6 months of C. siliqua administration. Three-point bending test revealed a significantly higher thickness index in the OVX+CS group compared to the OVX group and a higher cross-sectional area index compared to the control group.

CONCLUSION

Long-term administration of C. siliqua may be considered a non-pharmaceutical alternative treatment for postmenopausal osteoporosis. Further research is required to properly investigate the effects, and suitable treatment dose and schedule.

Glucose Metabolism in Osteoblasts in Healthy and Pathophysiological Conditions

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

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.

Negligible Effect of Estrogen Deficiency on Development of Skeletal Changes Induced by Type 1 Diabetes in Experimental Rat Models

Although postmenopausal osteoporosis often occurs concurrently with diabetes, little is known about interactions between estrogen deficiency and hyperglycemia in the skeletal system. In the present study, the effects of estrogen deficiency on the development of biochemical, microstructural, and mechanical changes induced by streptozotocin-induced diabetes mellitus (DM) in the rat skeletal system were investigated. The experiments were carried out on nonovariectomized (NOVX) and ovariectomized (OVX) control and diabetic mature female Wistar rats. Serum levels of bone turnover markers (CTX-I and osteocalcin) and 23 cytokines, bone mass and mineralization, histomorphometric parameters, and mechanical properties of cancellous and compact bone were determined. The results were subjected to two-way ANOVA and principal component analysis (PCA). Estrogen deficiency induced osteoporotic changes, with increased bone resorption and formation, and worsening of microstructure (femoral metaphyseal BV/TV decreased by 13.0%) and mechanical properties of cancellous bone (the maximum load in the proximal tibial metaphysis decreased by 34.2%). DM in both the NOVX and OVX rats decreased bone mass, increased bone resorption and decreased bone formation, and worsened cancellous bone microarchitecture (for example, the femoral metaphyseal BV/TV decreased by 17.3% and 18.1%, respectively, in relation to the NOVX controls) and strength (the maximum load in the proximal tibial metaphysis decreased by 35.4% and 48.1%, respectively, in relation to the NOVX controls). Only in the diabetic rats, profound increases in some cytokine levels were noted. In conclusion, the changes induced by DM in female rats were only slightly intensified by estrogen deficiency. Despite similar effects on bone microstructure and strength, the influence of DM on the skeletal system was based on more profound systemic homeostasis changes than those induced by estrogen deficiency.

Hyperglycemia compromises Rat Cortical Bone by Increasing Osteocyte Lacunar Density and Decreasing Vascular Canal Volume

Uncontrolled diabetes is associated with increased risk of bony fractures. However, the mechanisms have yet to be understood. Using high-resolution synchrotron micro-CT, we calculated the changes in the microstructure of femoral cortices of streptozotocin-induced hyperglycemic (STZ) Wistar Albino rats and tested the mechanical properties of the mineralized matrix by nanoindentation. Total lacunar volume of femoral cortices increased in STZ group due to a 9% increase in lacunar density. However, total vascular canal volume decreased in STZ group due to a remarkable decrease in vascular canal diameter (7 ± 0.3 vs. 8.5 ± 0.4 µm). Osteocytic territorial matrix volume was less in the STZ group (14,908 ± 689 µm³) compared with healthy controls (16,367 ± 391 µm³). In conclusion, hyperglycemia increased cellularity and lacunar density, decreased osteocyte territorial matrix, and reduced vascular girth, in addition to decreasing matrix mechanical properties in the STZ group when compared with euglycemic controls.

Birol Ay et al. use high-resolution synchrotron radiation micro-CT to calculate the changes in the microstructure of femoral cortices in STZ-induced hyperglycemic rats. They show that hyperglycemia increases lacunar density due to a reduction in osteocytic territorial matrix volume but decreases total vascular canal volume due to a decrease in canal diameter.

Exploring the potential of tocotrienol from Bixa orellana as a single agent targeting metabolic syndrome and bone loss

Metabolic syndrome (MetS) is associated with osteoporosis due to the underlying inflammatory and hormonal changes. Annatto tocotrienol has been shown to improve medical complications associated with MetS or bone loss in animal studies. This study aimed to investigate the effects of annatto tocotrienol as a single treatment for MetS and osteoporosis in high-carbohydrate high-fat (HCHF) diet-induced MetS animals. Three-month-old male Wistar rats were randomly divided into five groups. The baseline group was euthanized at the onset of the study. The normal group received standard rat chow and tap water. The remaining groups received HCHF diet and treated with three different regimens orally daily: (a) tocopherol-stripped corn oil (the vehicle of tocotrienol), (b) 60 mg/kg annatto tocotrienol, and (c) 100 mg/kg annatto tocotrienol. At the end of the study, measurements of MetS parameters, body compositions, and bone mineral density were performed in animals before sacrifice. Upon euthanasia, blood and femur of the rats were harvested for the evaluations of bone microstructure, biomechanical strength, remodelling activities, hormonal changes, and inflammatory response. Treatment with annatto tocotrienol improved all MetS parameters (except abdominal obesity), trabecular bone microstructure, bone strength, increased osteoclast number, normalized hormonal changes and inflammatory response in the HCHF animals. In conclusion, annatto tocotrienol is a potential agent for managing MetS and osteoporosis concurrently. The beneficial effects of annatto tocotrienol may be attributed to its ability to prevent the hormonal changes and pro-inflammatory state in animals with MetS.

Effects of metabolic syndrome on bone mineral density, histomorphometry and remodelling markers in male rats

This study aimed to evaluate the effects of metabolic syndrome (MetS) induced by high-carbohydrate high-fat (HCHF) diet on bone mineral density (BMD), histomorphometry and remodelling markers in male rats. Twelve male Wistar rats aged 12 weeks old were randomized into two groups. The normal group was given standard rat chow while the HCHF group was given HCHF diet to induce MetS. Abdominal circumference, blood glucose, blood pressure, and lipid profile were measured for the confirmation of MetS. Bone mineral density, histomorphometry and remodelling markers were evaluated for the confirmation of bone loss. The HCHF diet caused central obesity, hyperglycaemia, hypertension, and dyslipidaemia in male rats. No significant difference was observed in whole body bone mineral content and BMD between the normal and HCHF rats (p>0.05). For bone histomorphometric parameters, HCHF diet-fed animals had significantly lower osteoblast surface, osteoid surface, osteoid volume, and significantly higher eroded surface; resulting in a reduction in trabecular bone volume (p<0.05). Feeding on HCHF diet caused a significantly higher CTX-1 level (p<0.05), but did not cause any significant change in osteocalcin level compared to normal rats (p>0.05). In conclusion, HCHF diet-induced MetS causes imbalance in bone remodelling, leading to the deterioration of trabecular bone structure.

Osteoporosis is associated with metabolic syndrome induced by high-carbohydrate high-fat diet in a rat model

This study aimed to investigate the bone quality in rats induced with metabolic syndrome (MetS) using high-carbohydrate high-fat (HCHF) diet. Male Wistar rats (n = 14) were randomized into two groups. The normal group was given standard rat chow. The MetS group was given HCHF diet. Diet regimen was assigned for a period of 20 weeks. Metabolic syndrome parameters were measured monthly until MetS was established. Left tibiae were scanned using micro-computed tomography at week 0, 8, 12, 16, and 20 to analyze the trabecular and cortical bone structure. At the end of the study, rats were euthanized and their bones were harvested for analysis. Metabolic syndrome was established at week 12 in the HCHF rats. Significant deterioration of trabecular bone was observed at week 20 in the HCHF group (p < 0.05). The HCHF diet also decreased cortical and tissue area significantly (p < 0.05), but did not affect cortical thickness and bone calcium content (p > 0.05). Femur length and width in the HCHF group were significantly shorter than the normal group (p < 0.05). The biomechanical strength test showed that the femur of the HCHF rats could endure significantly lower force, but significantly higher displacement and strain compared to the normal rats (p < 0.05). In conclusion, HCHF diet-induced MetS can cause adverse effects on the bone.