Histomorphometric evaluation of the influence of the diabetic metabolic state on bone defect healing depending on the defect size in spontaneously diabetic BB/OK rats

Visualization of bone formation in sheep's middle ear by using fluorochrome sequential labelling (FSL)

One factor for the lacking integration of the middle ear stapes footplate prosthesis or the missing healing of stapes footplate fractures could be the known osteogenic inactivity. In contrast, it was recently demonstrated that titanium prostheses with an applied collagen matrix and immobilised growth factors stimulate osteoblastic activation and differentiation on the stapes footplate. Regarding those findings, the aim of this study was to evaluate the potential of bone regeneration including bone remodeling in the middle ear. Ten one-year-old female merino sheep underwent a middle ear surgery without implantation of middle ear prostheses or any other component for activating bone formation. Post-operatively, four fluorochromes (tetracycline, alizarin complexion, calcein green and xylenol orange) were administered by subcutaneous injection at different time points after surgery (1 day: tetracycline, 7 days: alizarin, 14 days: calcein, 28 days: xylenol). After 12 weeks, the temporal bones including the lateral skull base were extracted and histologically analyzed. Fluorescence microscopy analysis of the entire stapes with the oval niche, but in particular stapes footplate and the Crura stapedis revealed evidence of new bone formation. Calcein was detected in all and xylenol in 60% of the animals. In contrast, tetracycline and alizarin could only be verified in two animals. The authors were able to demonstrate the osseoregenerative potential of the middle ear, in particular of the stapes footplate, using fluorescence sequence labelling.

Recent progress in bone-repair strategies in diabetic conditions

Bone regeneration following trauma, tumor resection, infection, or congenital disease is challenging. Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia. It can result in complications affecting multiple systems including the musculoskeletal system. The increased number of diabetes-related fractures poses a great challenge to clinical specialties, particularly orthopedics and dentistry. Various pathological factors underlying DM may directly impair the process of bone regeneration, leading to delayed or even non-union of fractures. This review summarizes the mechanisms by which DM hampers bone regeneration, including immune abnormalities, inflammation, reactive oxygen species (ROS) accumulation, vascular system damage, insulin/insulin-like growth factor (IGF) deficiency, hyperglycemia, and the production of advanced glycation end products (AGEs). Based on published data, it also summarizes bone repair strategies in diabetic conditions, which include immune regulation, inhibition of inflammation, reduction of oxidative stress, promotion of angiogenesis, restoration of stem cell mobilization, and promotion of osteogenic differentiation, in addition to the challenges and future prospects of such approaches.

The effect of experimental diabetes and membrane occlusiveness on guided bone regeneration: A proof of principle study

OBJECTIVES

To evaluate the effect of membrane occlusiveness and experimental diabetes on early and late healing following guided bone regeneration.

MATERIAL AND METHODS

A total of 30 Wistar rats were randomly allocated to three groups: healthy (H), uncontrolled diabetic (UD) and controlled diabetic (CD). A critical size calvarial defect (CSD) was created at the mid-portion of one parietal bone, and it was treated with a double layer of e-PTFE membrane presenting 0.5 mm perforations. The animals were killed at 7 and 30 days of healing, and qualitative and quantitative histological evaluations were performed. Data were compared with the ones previously obtained from other 30 animals (10H, 10UD, 10 CD), where two CSDs were randomly treated with a double-layer e-PTFE occlusive membrane or left empty.

RESULTS

Following application of cell occlusive or cell permeable membranes, significant regeneration can be observed. However, at 30 days in the H group occlusive compared to cell permeable membranes promoted enhanced bone regeneration (83.9 ± 7.3% vs. 52.5 ± 8.6%), while no significant differences were observed within the CD and UD groups. UD led to reduced regeneration compared to H when an occlusive barrier was applied, whereas comparable outcomes to H and CD were observed when placing perforated membranes.

CONCLUSION

The application of cell permeable membranes may have masked the potentially adverse effect of experimental UD on bone regeneration.

CLINICAL RELEVANCE

Membrane porosity might contribute to modulate the bone regenerative response in UD conditions. Future studies are needed to establish the degree of porosity associated with the best regenerative outcomes as well as the underlying molecular mechanisms.

Unleashing β-catenin with a new anti-Alzheimer drug for bone tissue regeneration

The Wnt/β-catenin signaling pathway is critical for bone differentiation and regeneration. Tideglusib, a selective FDA approved glycogen synthase kinase-3β (GSK-3β) inhibitor, has been shown to promote dentine formation, but its effect on bone has not been examined. Our objective was to study the effect of localized Tideglusib administration on bone repair. Bone healing between Tideglusib treated and control mice was analysed at 7, 14 and 28 days postoperative (PO) with microCT, dynamic histomorphometry and immunohistology. There was a local downregulation of GSK-3β in Tideglusib animals, resulting in a significant increase in the amount of new bone formation with both enhanced cortical bone bridging and medullary bone deposition. The bone formation in the Tideglusib group was characterized by early osteoblast differentiation with down-regulation of GSK-3β at day 7 and 14, and higher accumulation of active β-catenin at day 14. Here, for the first time, we show a positive effect of Tideglusib on bone formation through the inactivation of GSK-3β. Furthermore, the findings suggest that Tideglusib does not interfere with precursor cell recruitment and commitment, contrary to other GSK-3β antagonists such as lithium chloride. Taken together, the results indicate that Tideglusib could be used directly at a fracture site during the initial intraoperative internal fixation without the need for further surgery, injection or drug delivery system. This FDA-approved drug may be useful in the future for the prevention of non-union in patients presenting with a high risk for fracture-healing.

Determination of the optimal diabetes duration for bone regeneration experiments in an alloxan-induced diabetic rabbit calvarial defect model

Purpose

The purpose of this study was to evaluate the optimal diabetes duration for bone regeneration experiments in an alloxan monohydrate (ALX)–induced diabetic rabbit calvarial defect model by evaluating the association between diabetes duration and bone healing capacity.

Methods

Twenty-four New Zealand white rabbits were used. Twenty-two rabbits were injected with 100 mg/kg of ALX to induce experimental diabetes. These rabbits were divided into 4 groups, including a control group and groups with diabetes durations of 1 week (group 1), 2 weeks (group 2), and 4 weeks (group 3). Calvarial defects were created at 1, 2, and 4 weeks after ALX injection and in the control rabbits. Cone-beam computed tomography (CBCT) scanning was performed on the day of surgery and at 2 and 4 weeks after surgery. The rabbits were sacrificed 4 weeks after surgery, followed by histological and immunofluorescence analysis.

Results

The diabetic state of all diabetic rabbits was well-maintained throughout the experiment. Reconstructed 3-dimensional CBCT imaging showed more rapid and prominent bone regeneration in the control group than in the experimental groups. Histological staining showed notable bone regeneration in the control group, in contrast to scarce bone formation in the experimental groups. The appearance and immunoreactivity of receptor activator of nuclear factor-kappa B and osteoprotegerin did not show notable differences among the groups.

Conclusion

ALX administration at 100 mg/kg successfully induced experimental diabetes in rabbits. The effect of diabetes on bone healing was evident when the interval between diabetes induction and the intervention was ≥1 week.

Hydroxyapatite calvaria graft repair in experimental diabetes mellitus in rats

Among the systemic conditions that impact negatively on the planning and execution of surgical procedures, diabetes mellitus (DM) is the primary clinical condition responsible for complications. This study investigated bone formation in critical defects surgically filled with hydroxyapatite (HA) in diabetic rats. A descriptive, randomized sample and blinded analysis were conducted to test bone regeneration in critical bone defects surgically performed in rat calvaria. Twenty adult male Wistar rats were randomly divided into two groups: control, normoglycemic animals (CG); and test, streptozotocin-induced hyperglycemic animals (TG). A circular bone defect was filled with HA and maintained subperiosteally. The clinical parameters evaluated were body weight, water and food intake, fasting blood glucose, and bone alkaline phosphatase. Bone-grafted area samples were submitted for histomorphometric and stereological analysis. The TG showed a significantly higher rate of new bone formation compared with the CG, sacrificed 15 days after surgery (p < 0.0001). However, at the end of the study, there was no significant difference in the amount of bone formed between groups (p = 0.077). In parallel, with the increase in osteoblastic activity observed in the TG by the measurement of systemic bone alkaline phosphatase (p = 0.016), the analysis of polarized microscopy and stereology demonstrated a lower level collagen maturation and mineralization in the TG. Quantitatively, the TG showed significantly better results for bone gain in the first 15 days. Qualitative assessments, however, showed fewer collagen fibers and bone maturation in the TG compared with the CG both at 15 and 45 days. Therefore, the postoperative evaluation of bone grafts with HA in hyperglycemic situations should consider the systemic and local effects of this condition on the quality of bone repair, rather than identifying the filling or stability of the grafted area after the process. We conclude that clinically detectable bone repair in diabetic animal models submitted to hydroxyapatite grafts may be satisfactory in the early stages. However, hyperglycemia compromises the quality of the newly formed bone and the collagen cross-linking involved in this process.

The effects of supplemental melatonin administration on the healing of bone defects in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) causes an increased production of free radicals that can impair bone healing. Melatonin is a hormone secreted mainly by the pineal gland, which participates in the neutralization process of free radicals.

Peri-implant defect regeneration in the diabetic pig: A preclinical study

OBJECTIVES

The study aims to establish a peri-implant dehiscence-type bone defect in a diabetic animal model of human bone repair and to quantify the influence of diabetes on peri-implant bone regeneration.

MATERIAL AND METHODS

Experimental diabetes was induced in three domestic pigs by streptozotocin. Three animals served as healthy controls. After 12 months four standardized peri-implant dehiscence bone defects were surgically created in the ramus mandibulae. The animals were sacrificed after 90 days. Samples were histologically analyzed to quantify new bone height (NBH), bone-to-implant-contact (BIC), area of newly formed bone (NFB), bone-density (BD), and bone mineralization (BM) in the prepared defect (-D) and in a local control region (-L).

RESULTS

After 90 days, diabetic animals revealed a significantly lower BIC (p = 0.037) and BD (p = 0.041) in the defect area (-D). NBH and BM-D differences within the groups were not significant (p > 0.05). Significant more NFB was measured in the healthy control group (p = 0.046). In the region of local bone BIC-L was significant less in the diabetic group (p = 0.028). In the local control region BD-L and BM-L was lower in the diabetic group compared to the healthy control animals (p > 0.05).

CONCLUSION

Histological evidence indicates impaired peri-implant defect regeneration in a diabetic animal model.

Calcitonin and vitamin D3 have high therapeutic potential for improving diabetic mandibular growth

The goal of this study was to assess the effect of the intermittent combination of an antiresorptive agent (calcitonin) and an anabolic agent (vitamin D₃) on treating the detrimental effects of Type 1 diabetes mellitus (DM) on mandibular bone formation and growth. Forty 3-week-old male Wistar rats were divided into four groups: the control group (normal rats), the control C+D group (normal rats injected with calcitonin and vitamin D₃), the diabetic C+D group (diabetic rats injected with calcitonin and vitamin D₃) and the diabetic group (uncontrolled diabetic rats). An experimental DM condition was induced in the male Wistar rats in the diabetic and diabetic C+D groups using a single dose of 60 mg·kg⁻¹ body weight of streptozotocin. Calcitonin and vitamin D₃ were simultaneously injected in the rats of the control C+D and diabetic C+D groups. All rats were killed after 4 weeks, and the right mandibles were evaluated by micro-computed tomography and histomorphometric analysis. Diabetic rats showed a significant deterioration in bone quality and bone formation (diabetic group). By contrast, with the injection of calcitonin and vitamin D₃, both bone parameters and bone formation significantly improved (diabetic C+D group) (P < 0.05). These findings suggest that these two hormones might potentially improve various bone properties.

Effect of targeted delivery of bone morphogenetic protein-2 on bone formation in type 1 diabetes

PURPOSE

Bone formation and healing are diminished in experimental type 1 diabetes. The present study investigated whether controlled local release of recombinant human bone morphogenetic protein 2 (rhBMP-2) stimulates bone defect healing in diabetes as a consequence of its anabolic effects on bone.

MATERIALS AND METHODS

Bilateral experimental circular bone defects were created in the temporal bones of 64 BALB/cByJ mice. Defects were treated with acellular collagen sponge plus 0.4 or 1.8 μg of rhBMP-2 per defect, and untreated defects served as controls. The healing of the defects over a 14-day period in diabetic and nondiabetic mice was analyzed histomorphometrically.

RESULTS

Diabetes inhibited bone formation in both untreated and BMP-treated bone defects. Controlled local release of rhBMP-2 significantly stimulated bone formation in diabetic animals, bringing it nearly to normal levels, and enhanced bone regeneration in normal animals.

CONCLUSION

Recombinant human BMP-2 may be beneficial in treating deficient intramembranous bone formation in diabetes.

Insulin improves osteogenesis of titanium implants under diabetic conditions by inhibiting reactive oxygen species overproduction via the PI3K-Akt pathway

Clinical evidence indicates that insulin therapy improves implant survival rates in diabetic patients; however, the mechanisms responsible for this effect are unknown. Here, we test if insulin exerts anti-oxidative effects, thereby improving diabetes-associated impaired osteoblast behavior on titanium implants. To test this hypothesis, we cultured primary rabbit osteoblasts in the presence of titanium implants and studied the impact of treatment with normal serum (NS), diabetic serum (DS), DS + insulin, DS + tempol (a superoxide dismutase mimetic), DS + insulin + tempol, and DS + insulin + wortmannin. We analyzed cell function, apoptosis, and reactive oxygen species (ROS) production in osteoblasts following the various treatments. Treatment with DS induced osteoblast dysfunction, evidenced by impaired cell attachment and morphology, decreased cell proliferation and ALP activity, and decreased expression of osteogenesis-related genes. We also observed a significant increase in apoptosis. Importantly, treatment with DS resulted in increased production of ROS in osteoblasts. In contrast, treatment with insulin inhibited ROS production, alleviated cell dysfunction, and decreased apoptosis of osteoblasts on the implants. Scavenging ROS with tempol also attenuated cell dysfunction. Compared to insulin treatment alone, the combination of insulin and tempol failed to further improve osteoblast functional recovery. Moreover, the anti-oxidative and pro-osteogenic effects afforded by insulin were almost completely abolished by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin. These results demonstrate, for the first time, that insulin treatment alleviates the impaired osteogenesis of titanium implants under diabetic conditions by inhibiting ROS overproduction via a PI3K/Akt-dependent mechanism. Both the anti-oxidative and metabolic properties of insulin should make it a viable therapeutic option to combat diabetic implant failure.

Efficacy of Ankaferd Blood Stopper on bone healing in diabetic rats: a stereological and histopathological study

We evaluated the effects of Ankaferd Blood Stopper (ABS) and routine antibiotic prophylaxis (AP) on early healing of bone defects in diabetic rats. We used 48 rats in the study. Diabetes was induced in 24 rats using streptozotocin; the remaining 24 healthy untreated rats served as controls. Twelve of the diabetic rats and 12 of the healthy rats were treated with AP for 3 days before surgery. Bilateral bone defects were created in the mandible of all animals. ABS was applied to the defects on the left sides of the mandibles, while nothing was applied to the right sides. Animals were sacrificed on days 7 and 14 after operation and examined for histopathology and by stereology. The volume of newly formed bone was significantly less in the diabetic rats on both days 7 and 14. Local administration of ABS significantly increased the mean volume of newly formed bone in both diabetic and nondiabetic rats at days 7 and 14. No significant difference in new bone formation was found between AP and ABS treatment in diabetic rats. Both AP and local administration of ABS have beneficial effects on bone healing in diabetic animals.

Aqueous-ozone irrigation of bone monocortical wounds in hyperglycemic rats

PURPOSE

To analyze the effects of aqueous ozone irrigation over bone healing in hyperglycemia-induced rats.

METHODS

Forty-eight male Wistar rats were allocated into Group H (hyperglycemic) or Group N (control). Monocortical bone wound were performed on femurs' anterolateral face. Wounds were treated with a trans-operatory single irrigation of 100ml of aqueous ozone [0.004mg/ml] whereas control groups received 100ml of pure water (Milli-Q®). Histomorphological and histomorphometrical analyses were accomplished after seven, 14 and 21 days. Kruskal-Wallis and Mann-Whitney statistical tests were applied for bone neoformation quantification and assessment.

RESULTS

Aqueous ozone wounds irrigated revealed diffuse hemorrhage and increased neoformed of blood vessels number. There was no statistical significant difference in bone trabeculae neoformation. After seven and 14 days, the number of osteoclasts was higher in aqueous ozone groups than in those treated with pure water.

CONCLUSION

Independently of blood glucose levels, aqueous ozone allowed an increase in blood vessels neoformation and osteoclast migration, without affect bone trabeculae neoformation.

Bone healing and the effect of implant surface topography on osteoconduction in hyperglycemia

Dental implant failures that occur clinically for unknown reasons could be related to undiagnosed hyperglycemia. The exact mechanisms that underlie such failures are not known, but there is a general consensus that bone growth is compromised in hyperglycemia. Nevertheless, contradictory findings exist related to peri-implant bone healing in hyperglycemia. We hypothesized that hyperglycemia delays early bone healing by impeding osteoconduction, and that the compromised implant integration due to hyperglycemia could be abrogated by using nanotopographically complex implants. Thus we undertook two parallel experiments, an osteotomy model and a bone in-growth chamber model. The osteotomy model tracked temporal bone healing in the femora of euglycemic and hyperglycemic rats using micro computed tomography (microCT) analysis and histology. The bone in-growth chamber model used implant surfaces of either micro- or nanotopographical complexity and measured bone-implant contact (BIC) using backscattered electron imaging in both metabolic groups. Quantitative microCT analyses on bone volume, trabeculae number and trabeculae connectivity density provided clear evidence that bone healing, both reparative trabecular bone formation and remodeling, was delayed in hyperglycemia, and the reparative bone volume changed with time between metabolic groups. Furthermore, fluorochrome labeling showed evidently less mineralized bone in hyperglycemic than euglycemic animals. An increased probability of osteoconduction was seen on nano-compared with microtopographically complex surfaces, independent of metabolic group. The nanotopographically complex surfaces in hyperglycemia outperformed microtopographically complex surfaces in euglycemic animals. In conclusion, the compromised implant integration in hyperglycemia is abrogated by the addition of nanotopographical features to an underlying microtopographically complex implant surface.

Factors associated with nonunion, delayed union, and malunion in foot and ankle surgery in diabetic patients

The incidence of bone healing complications in diabetic patients is believed to be high after foot and ankle surgery. Although the association of hyperglycemia with bone healing complications has been well documented, little clinical information is available to show which diabetes-related comorbidities directly affect bone healing. Our goal was to better understand the risk factors associated with poor bone healing in the diabetic population through an exploratory, observational, retrospective, cohort study. To this end, 165 diabetic patients who had undergone arthrodesis, osteotomy, or fracture reduction were enrolled in the study to assess the risk factors associated with nonunion, delayed union, and malunion after elective and nonelective foot and/or ankle surgery. Bivariate analyses showed that a history of foot ulcer, peripheral neuropathy, and surgery duration were statistically significantly associated with bone healing complications. After adjusting for other covariates, only peripheral neuropathy, surgery duration, and hemoglobin A1c levels >7% were significantly associated statistically with bone healing complications. Of the risk factors we considered, peripheral neuropathy had the strongest association with bone healing complications.

Patterns of diabetic periodontal wound repair: a study using micro-computed tomography and immunohistochemistry

BACKGROUND

Diabetes is known to impair wound healing and deteriorate the periodontal condition. There is limited information about the patterns and events associated with periodontal wound repair. In this study, we evaluate the dynamics of periodontal wound repair using micro-computed tomography (microCT) and immunohistochemistry.

METHODS

Thirty-six male rats were used, and diabetes was induced by streptozotocin. The maxillary first molars were extracted, and a tooth-associated osseous defect was created in the extraction area. Animals were sacrificed after 7, 14, and 21 days. Volumetry and distribution of bone trabeculae were evaluated by microCT imaging. The patterns of healing and collagen alignment were evaluated by histology. Advanced glycation end-product (AGE) deposition and expression of the receptor for AGEs (RAGE), tartrate-resistant acid phosphatase, and proliferating cell nuclear antigen were evaluated by histochemical and immunohistochemical staining.

RESULTS

Diabetic animals demonstrated a significantly reduced bone volume and trabecular number as well as thinner trabeculae and more trabecular separation in osseous defects. The early stage was characterized by significantly reduced cellular proliferation and prolonged active inflammation without evident bone resorption, whereas delayed recovery of collagen realignment, matrix deposition, and bone turnover was noted in later stages. Although AGEs and RAGE were present during healing in diabetes and controls, a stronger and more persistent level of expression was observed in the group with diabetes

CONCLUSIONS

Diabetes significantly delayed osseous defect healing by augmenting inflammation, impairing proliferation, and delaying bone resorption. The AGE-RAGE axis can be activated under metabolic disturbance and inflammation.

The effect of diabetes mellitus on osseous healing

Diabetes mellitus and, in particular, type 1 diabetes has been associated with impaired osseous wound healing properties. The scope of the present review is to discuss the clinical evidence supporting a higher rate of complications during fracture healing in diabetic patients and the histological evidence indicating impaired potential for intramembranous and endochondral ossification in the presence of uncontrolled experimental diabetes. The article further provides a synthesis of our current understanding of the plausible molecular mechanisms underlying the diabetic bone healing pathophysiology and of the role of insulin treatment in promoting osseous healing in the diabetic status.

Diabetes causes the accelerated loss of cartilage during fracture repair which is reversed by insulin treatment

Fracture healing in diabetic individuals and in animal models of diabetes is impaired. To investigate mechanisms by which diabetes may affect fracture healing we focused on the transition from cartilage to bone, a midpoint in the fracture healing process. Femoral fractures were induced in mice rendered diabetic by multiple low dose streptozotocin treatment and compared to matching normoglycemic mice. One group of diabetic animals was treated with slow release insulin to maintain normal serum glucose levels. The results indicate that there was relatively little difference in the initial formation of the fracture callus on day 10. However, on day 16 the diabetic group had significantly smaller callus, greater loss of cartilage and enhanced osteoclastogenesis that was normalized by treatment with insulin when assessed by histomorphometric analysis. Chondrocyte apoptosis was significantly higher in diabetic mice and this increase was blocked by insulin. These changes were accompanied by diabetes-increased mRNA levels of RANKL, TNF-alpha, and ADAMTS-4 and -5 measured by real-time PCR, which was reversed by insulin treatment. On days 16 and 22 bone formation within the callus of diabetic mice was significantly less than the normoglycemic and brought to normal levels by insulin treatment. These results suggest that a significant effect of diabetes on fracture healing is increased chondrocyte apoptosis and osteoclastogenesis that accelerates the loss of cartilage and reduces the anlage for endochondral bone formation during fracture repair. That insulin reverses these effects demonstrates that they are directly related to the diabetic condition.

Type 2 diabetes has minimal effect on osseointegration of titanium implants in Psammomys obesus

OBJECTIVES

Dental implants are routinely used with high success rates in generally healthy individuals. In contrast, their use in patients with uncontrolled diabetes mellitus (DM) remains controversial as altered bone healing around implants has been reported. The majority of reports addressing the issue of osseointegration of implants in animals were performed in beta-cell cytotoxic-induced Type I diabetes. In this study, we assessed the osseointegration of implants in Gerbil Psammomys obesus, a model of nutritionally induced Type 2 DM.

MATERIALS AND METHODS

Titanium implants were inserted into the tibial medullary space of 140 male diabetic and control animals. One, 2, 4, and 8 weeks after implantation the tibias were removed for histomorphometric evaluation, which included trabecular bone volumes (TBV) and osseointegration.

RESULTS

Two weeks following implantation, diabetic animals had slightly less mature bone when compared with control animals. This distinction was not present 4 weeks after implantation. Interestingly, no correlation was found between ossetointegration or TBV and glucose and insulin levels. Furthermore, no difference in osseointegration and TBV values was seen between the groups. The heterogeneity of serum glucose and insulin levels in this model and the possible role of insulin in bone metabolism are discussed.

CONCLUSIONS

No significant difference in osseointegration and TBV was seen between diabetic and control P. obesus, a model of nutritionally induced Type 2 DM.

Influences of diabetes (db/db), obese (ob/ob) and dystrophic (dy/dy) genotype mutations on hind limb bone maturation: a morphometric, radiological and cytochemical indices analysis

The influences of single-gene missense mutations expressing diabetes (db/db), obese (ob/ob) or dystrophia (dy/dy) dysregulated metabolic syndromes on hind limb bone maturation and cytodevelopment in C57BL/KsJ mice were evaluated by radiological, macro- and cytomorphometric analysis of the resulting variances in os coxae, femur and tibia osteodevelopment indices relative to control parameters between 8 and 16 weeks of age. Associated with obesity and hyperglycaemic/hyperinsulinaemic states, both db/db and ob/ob mutants demonstrated significant suppression of hind limb maturation (length) and cytodensity indices relative to control growth parameters. By contrast, skeletal growth suppression induced by dy/dy mutation expression was associated with lean body mass and normoglycaemic/hypoinsulinaemic systemic endometabolic indices. In both db/db and ob/ob mutation syndromes, osteovascular, -interstitial and -cytolipidaemia were prominent cytochemical aberrations of the osteopaenic states relative to the dyslipidaemia/fibrodysplasia characteristic of dy/dy osteomaturation. Between 8 and 16 weeks of age, both ob/ob and db/db groups demonstrated extensive cortical interstitial (laminal) osteolipidaemia and suppressed cytodensities compared to control indices. These data demonstrate that the abnormal hyperglycaemic/hyperinsulinaemic endometabolic states associated with the expression of db/db and ob/ob genomutations promote extensive lipidaemia-induced osteopaenia, compromising hind limb osteomaturation and cytodensity indices, as compared to the hyperfibritic osteopaenia characteristic of dy/dy mutation syndromes. Recognized therapeutic modulation of the hypercytolipidaemic component of diabetes-obesity syndromes may prove to be effective towards amelioration of the deleterious influences of these expressed hyperglycaemic, dysregulated lipometabolic conditions on osteomaturation and cytodevelopment.

Effects on the bones of vanadyl acetylacetonate by oral administration: a comparison study in diabetic rats

Oral delivery, rather than parenteral administration, would be beneficial for treating diabetic mellitus owing to the need for a long-term regimen. The objectives of this study were to evaluate oral delivery tolerance and the effects on the bone of accumulated vanadium following the long-term administration of vanadyl acetylacetonate (VAC). Normal and diabetic rats were intragastrically administered VAC at a dose of 3 mg vanadium/kg body weight once daily for 35 consecutive days. VAC did not cause any obvious signs of diarrhea, any changes in kidney or liver, or deaths in any group. The phosphate levels in the bone were slightly increased, and the calcium levels in the bone were not obviously changed as compared with those of the rat group not receiving VAC. After administration of VAC, the decreased ultimate strength, trabecular thickness, mineral apposition rate, and plasma osteocalcin in diabetic rats were either improved or normalized, but reduced bone mineral density (BMD) in diabetic rats was not improved. None of the parameters evaluated in normal rats were altered. The results indicate that the oral VAC is tolerated and benefits the diabetic osteopathy of rats, but seems not to influence the bone of normal rats. They also suggest that VAC improves diabetes-related bone disorders, primarily by improving the diabetic state.

Effects of streptozotocin-induced diabetes mellitus on some bone turnover markers in the vertebrae of ovary-intact and ovariectomized adult rats

Diabetes mellitus and estrogen deficit are known causes of osteopenia in animal models as well as in humans. In the present work, the combined effect of ovariectomy and diabetes was investigated. Diabetes was induced in ovary-intact and ovariectomized female Wistar rats with a single injection (50 mg/kg body weight, i.p.) of streptozotocin. The rats were administered insulin (I) daily or 17-β estradiol (E2) on alternate days for a period of 35 days and sacrificed. Serum calcium (Ca2+), phosphorus (P), alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP), vertebral ALP, collagen, and glycosaminoglycans were estimated. The levels of serum Ca2+and P increased in diabetic rats, but decreased after I or E2treatments. Serum ALP and TRAP activity increased in the ovary-intact and ovariectomized diabetic rats. Vertebral ALP activity increased in ovariectomized diabetic rats, but decreased in diabetic rats, which were treated with I or E2. In the vertebrae, TRAP activity was elevated as a result of diabetes, but this was prevented by insulin or estradiol. Diabetes induced a decrease in total collagen in the vertebrae, while I or E2treatment induced an increase. The levels of chondroitin sulphate and heparan sulphate decreased significantly in the vertebrae of both ovary-intact and ovariectomized diabetic rats, while hyaluronic acid increased. In conclusion, diabetes and ovariectomy each seem to affect the process of matrix formation and mineralization in the bone, and this is aggravated by the combination of diabetes and ovariectomy. The effects of I and E2were similar, and both hormones reversed the changes brought about by diabetes.

Influences of obese (ob/ob) and diabetes (db/db) genotype mutations on lumber vertebral radiological and morphometric indices: skeletal deformation associated with dysregulated systemic glucometabolism

Background

Both diabetes and obesity syndromes are recognized to promote lumbar vertebral instability, premature osteodegeneration, exacerbate progressive osteoporosis and increase the propensity towards vertebral degeneration, instability and deformation in humans.

Methods

The influences of single-gene missense mutations, expressing either diabetes (db/db) or obese (ob/ob) metabolic syndromes on vertebral maturation and development in C57BL/KsJ mice were evaluated by radiological and macro-morphometric analysis of the resulting variances in osteodevelopment indices relative to control parameters between 8 and 16 weeks of age (syndrome onset @ 4 weeks), and the influences of low-dose 17-B-estradiol therapy on vertebral growth expression evaluated.

Results

Associated with the indicative genotypic obesity and hyper-glycemic/-insulinemic states, both db/db and ob/ob mutants demonstrated a significant (P ≤ 0.05) elongation of total lumbar vertebrae column (VC) regional length, and individual lumbar vertebrae (LV1-5) lengths, relative to control VC and LV parameters. In contrast, LV1-5 width indices were suppressed in db/db and ob/ob mutants relative to control LV growth rates. Between 8 and 16 weeks of age, the suppressed LV1-5 width indices were sustained in both genotype mutant groups relative to control osteomaturation rates. The severity of LV1-5 width osteosuppression correlated with the severe systemic hyperglycemic and hypertriglyceridemic conditions sustained in ob/ob and db/db mutants. Low-dose 17-B-estradiol therapy (E2-HRx: 1.0 ug/ 0.1 ml oil s.c/3.5 days), initiated at 4 weeks of age (i.e., initial onset phase of db/db and ob/ob expressions) re-established control LV 1–5 width indices without influencing VC or LV lengths in db/db groups.

Conclusion

These data demonstrate that the abnormal systemic endometabolic states associated with the expression of db/db and ob/ob genomutation syndromes suppress LV 1–5 width osteomaturation rates, but enhanced development related VC and LV length expression, relative to control indices in a progressive manner similar to recognized human metabolic syndrome conditions. Therapeutic E2 modulation of the hyperglycemic component of diabetes-obesity syndrome protected the regional LV from the mutation-induced osteopenic width-growth suppression. These data suggest that these genotype mutation models may prove valuable for the evaluation of therapeutic methodologies suitable for the treatment of human diabetes- or obesity-influenced, LV degeneration-linked human conditions, which demonstrate amelioration from conventional replacement therapies following diagnosis of systemic syndrome-induced LV osteomaturation-associated deformations.

Is insulin an anabolic agent in bone? Dissecting the diabetic bone for clues

Diabetic osteoporosis is increasingly recognized as a significant comorbidity of type 1 diabetes mellitus. In contrast, type 2 diabetes mellitus is more commonly associated with modest increases in bone mineral density for age. Despite this dichotomy, clinical, in vivo, and in vitro data uniformly support the concept that new bone formation as well as bone microarchitectural integrity are altered in the diabetic state, leading to an increased risk for fragility fracture and inadequate bone regeneration following injury. In this review, we examine the contribution that insulin, as a potential anabolic agent in bone, may make to the pathophysiology of diabetic bone disease. Specifically, we have assimilated human and animal data examining the effects of endogenous insulin production, exogenous insulin administration, insulin sensitivity, and insulin signaling on bone. In so doing, we present evidence that insulin, acting as an anabolic agent in bone, can preserve and increase bone density and bone strength, presumably through direct and/or indirect effects on bone formation.

Polychrome labeling of bone with seven different fluorochromes: enhancing fluorochrome discrimination by spectral image analysis

Bone formation and remodeling in vivo can be assessed by polychrome labeling using calcium-binding fluorescent dyes. The number of fluorochromes, however, limits this technique due to the fact that with increasing number, fluorescent spectra inevitably overlap, which makes discrimination more difficult. In order to enhance discrimination, we performed spectral image analysis. Non-critical size defects of the femur of male Wistar rats served as a model for bone formation. Eight different fluorochromes (calcein blue, xylenol orange, calcein, alizarine complexone, doxycycline, rolitetracycline, hematoporphyrin, and BAPTA) were administered sequentially subcutaneously every third day starting at day 4 after surgery. Following, bone specimen were embedded in methylmethacrylate and analyzed by spectral image acquisition using a Sagnac type interferometer (ASI, Israel). Seven of the eight applied fluorochromes could be resolved using spectral image examination. With BAPTA, we present a new fluorochrome suitable for bone labeling. Due to the superior sensitivity of the spectral image acquisition, the thickness of the bone sections could be reduced so that 5 mum thick sections could be analyzed. Spectral decomposition and subsequent linear unmixing allows depiction of each individual fluorochrome without interference of any other, enabling a reliable and superior morphometric analysis of labeled regions.

Is there an autoimmune process in bone? Gene expression studies in diabetic and nondiabetic BB rats as well as BB rat-related and -unrelated rat strains

It is well known that type 1 diabetes is associated with a decrease in bone mass and delayed healing of fractures in human and in animal models of type 1 diabetes. Using well- and poorly compensated diabetic BB/O(ttawa) K(arlsburg) rats spontaneously developing insulin-dependent type 1 diabetes, it was recently shown that, in contrast to all other tissues studied, bone is most influenced by metabolic state and seems to be regulated in a manner different from other organs. Therefore, we studied the expression of additional genes (Bmp-1, Bmp-4, Vegf, Bglap, Il-1b, Infg, Tnfa, Calca, Sp1, Yy1) in bone of nondiabetic BB rats compared with newly diagnosed and well- and poorly compensated diabetic rats as well as two nondiabetes-prone congenic BB.SHR rats, BB rat-related (WOKW) and -unrelated rat strains (F344). Six males of each group were euthanized, the tibial bone was removed, and total RNA was extracted, transcribed in complementary DNA, and used for real-time PCR. In a comparison of nondiabetic with diabetic groups, the relative gene expression was reduced by >80% in newly diagnosed and in well-compensated diabetic BB/OK rats. The gene expression in poorly compensated rats increased significantly in 7 of 10 genes and was comparable with those of nondiabetic BB/OK rats. In a comparison of gene expression between diabetes-prone BB/OK and nondiabetes-prone BB.1K, BB.4S, WOKW, and F344 rats, there were no significant differences between newly diagnosed and well-compensated BB/OK diabetic rats and nondiabetic BB.1K, BB.4S, WOKW, and F344 rats. On the basis of these findings, we concluded that spontaneous diabetes influences bone gene expression in BB/OK rats, which may be attributed to the genetically determined autoimmune process not only affecting pancreatic beta-cells but also bone formation and resorption.