Elevated leptin expression in rat model of traumatic spinal cord injury and femoral fracture

Regulation of Bone by Mechanical Loading, Sex Hormones, and Nerves: Integration of Such Regulatory Complexity and Implications for Bone Loss during Space Flight and Post-Menopausal Osteoporosis

During evolution, the development of bone was critical for many species to thrive and function in the boundary conditions of Earth. Furthermore, bone also became a storehouse for calcium that could be mobilized for reproductive purposes in mammals and other species. The critical nature of bone for both function and reproductive needs during evolution in the context of the boundary conditions of Earth has led to complex regulatory mechanisms that require integration for optimization of this tissue across the lifespan. Three important regulatory variables include mechanical loading, sex hormones, and innervation/neuroregulation. The importance of mechanical loading has been the target of much research as bone appears to subscribe to the "use it or lose it" paradigm. Furthermore, because of the importance of post-menopausal osteoporosis in the risk for fractures and loss of function, this aspect of bone regulation has also focused research on sex differences in bone regulation. The advent of space flight and exposure to microgravity has also led to renewed interest in this unique environment, which could not have been anticipated by evolution, to expose new insights into bone regulation. Finally, a body of evidence has also emerged indicating that the neuroregulation of bone is also central to maintaining function. However, there is still more that is needed to understand regarding how such variables are integrated across the lifespan to maintain function, particularly in a species that walks upright. This review will attempt to discuss these regulatory elements for bone integrity and propose how further study is needed to delineate the details to better understand how to improve treatments for those at risk for loss of bone integrity, such as in the post-menopausal state or during prolonged space flight.

Bone defects are repaired by enhanced osteogenic activity of the induced membrane: a case report and literature review

Background

The induced membrane technique (IMT) is an effective strategy to repair bone defects and involves a two-stage set of surgical procedures. Although the IM has osteogenic activity, bone grafting is necessary in standard IMT. Bone defects repaired completely by osteogenic activity of the IM alone without bone grafts are rare.

Case presentation

We present a case of infected fractures and bone defects of the ulna and radius treated with IMT. After the first stage using polymethylmethacrylate (PMMA) beads, X-rays showed that new callus developed after 2 to 4 months, and the defects were repaired completely by 5 months. We also present a literature review on spontaneous osteogenesis of the IM in patients.

Conclusions

We present a case of infected ulnar and radial bone defects that healed by 5 months after the first stage of the IMT using a PMMA spacer. This finding suggests that local associated inflammatory reactions and bone tissue might enhance the osteogenic activity of the IM, causing spontaneous healing of bone defects. This appears to be the first such case reported in the literature.

The Role of Lipids, Lipid Metabolism and Ectopic Lipid Accumulation in Axon Growth, Regeneration and Repair after CNS Injury and Disease

Axons in the adult mammalian nervous system can extend over formidable distances, up to one meter or more in humans. During development, axonal and dendritic growth requires continuous addition of new membrane. Of the three major kinds of membrane lipids, phospholipids are the most abundant in all cell membranes, including neurons. Not only immature axons, but also severed axons in the adult require large amounts of lipids for axon regeneration to occur. Lipids also serve as energy storage, signaling molecules and they contribute to tissue physiology, as demonstrated by a variety of metabolic disorders in which harmful amounts of lipids accumulate in various tissues through the body. Detrimental changes in lipid metabolism and excess accumulation of lipids contribute to a lack of axon regeneration, poor neurological outcome and complications after a variety of central nervous system (CNS) trauma including brain and spinal cord injury. Recent evidence indicates that rewiring lipid metabolism can be manipulated for therapeutic gain, as it favors conditions for axon regeneration and CNS repair. Here, we review the role of lipids, lipid metabolism and ectopic lipid accumulation in axon growth, regeneration and CNS repair. In addition, we outline molecular and pharmacological strategies to fine-tune lipid composition and energy metabolism in neurons and non-neuronal cells that can be exploited to improve neurological recovery after CNS trauma and disease.

Leptin Mediated Pathways Stabilize Posttraumatic Insulin and Osteocalcin Patterns after Long Bone Fracture and Concomitant Traumatic Brain Injury and Thus Influence Fracture Healing in a Combined Murine Trauma Model

Recent studies on insulin, leptin, osteocalcin (OCN), and bone remodeling have evoked interest in the interdependence of bone formation and energy household. Accordingly, this study attempts to investigate trauma specific hormone changes in a murine trauma model and its influence on fracture healing. Thereunto 120 female wild type (WT) and leptin-deficient mice underwent either long bone fracture (Fx), traumatic brain injury (TBI), combined trauma (Combined), or neither of it and therefore served as controls (C). Blood samples were taken weekly after trauma and analyzed for insulin and OCN concentrations. Here, WT-mice with Fx and, moreover, with combined trauma showed a greater change in posttraumatic insulin and OCN levels than mice with TBI alone. In the case of leptin-deficiency, insulin changes were still increased after bony lesion, but the posttraumatic OCN was no longer trauma specific. Four weeks after trauma, hormone levels recovered to normal/basal line level in both mouse strains. Thus, WT- and leptin-deficient mice show a trauma specific hyperinsulinaemic stress reaction leading to a reduction in OCN synthesis and release. In WT-mice, this causes a disinhibition and acceleration of fracture healing after combined trauma. In leptin-deficiency, posttraumatic OCN changes are no longer specific and fracture healing is impaired regardless of the preceding trauma.

Review of Secondary Causes of Osteoporotic Fractures Due to Diabetes and Spinal Cord Injury

PURPOSE OF REVIEW

The aim of this review is to gain a better understanding of osteoporotic fractures and the different mechanisms that are driven in the scenarios of bone disuse due to spinal cord injury and osteometabolic disorders due to diabetes.

RECENT FINDINGS

Despite major advances in understanding the pathogenesis, prevention, and treatment of osteoporosis, the high incidence of impaired fracture healing remains an important complication of bone loss, leading to marked impairment of the health of an individual and economic burden to the medical system. This review underlines several pathways leading to bone loss and increased risk for fractures. Specifically, we addressed the different mechanisms leading to bone loss after a spinal cord injury and diabetes. Finally, it also encompasses the changes responsible for impaired bone repair in these scenarios, which may be of great interest for future studies on therapeutic approaches to treat osteoporosis and osteoporotic fractures.

Gene expression changes are associated with severe bone loss and deficient fracture callus formation in rats with complete spinal cord injury

STUDY DESIGN

Animal study.

OBJECTIVES

To investigate the effects of SCI on bone quality and callus formation.

SETTING

University and hospital-based research center, Ribeirão Preto Medical School, Brazil.

METHODS

Rats sustaining a complete SCI for 10 days received a fracture at the femoral diaphysis and were followed-up for 14 days. Bone callus and contralateral nonfractured tibia were assessed by DXA, µCT, ELISA, histomorphometry, immunohistochemistry, biomechanical test, and gene expression.

RESULTS

SCI downregulated osteoblastic-related gene expression in the nonfractured tibias, associated with a twofold increase in osteoclasts and overexpression of RANK/RANKL, which resulted in lower bone mass, impaired microarchitecture, and weaker bones. On day 14 postfracture, we revealed early and increased trabecular formation in the callus of SCI rats, despite a marked 75% decrease in OPG-positive cells, and 41% decrease in density. Furthermore, these calluses showed higher porosity and thinner newly formed trabeculae, leading to lower strength and angle failure.

CONCLUSIONS

SCI-induced bone loss resulted from increased bone resorption and decreased bone formation. We also evidenced accelerated bone healing in the SCI rats, which may be attributed to the predominant intramembranous ossification. However, the newly formed bone was thinner, less dense, and more porous than those in the non-SCI rats. As a result, these calluses are weaker and tolerate lesser torsion deformation than the controls, which may result in recurrent fractures and characterizes a remarkable feature that may severely impair life quality.

Upregulation of suppressor of cytokine signaling 3 ameliorates spinal degenerative disease in adolescents by mediating leptin and tumor necrosis factor-α levels

Spinal degenerative changes may occur following the rapid growth observed in adolescents, causing a reduced quality of life. The suppressor of cytokine signaling (SOCS) is involved in various degenerative diseases. The current study recruited adolescents with spinal degenerative disease (SDD) to identify the effect of SOCS-3 on leptin and tumor necrosis factor-α (TNF-α) levels in this disorder. From January 2010 to January 2016, 120 adolescents (aged 14 to 25) were enrolled in the current study, with 68 diagnosed with SDD and the remaining 52 treated as controls. Nucleus pulposus cells (NPCs) were extracted and cultured in vitro. TNF-α levels in NPCs were determined using flow cytometry. Degenerative NPCs were then transfected with pCR3.1-SOCS-3 and ELISA was performed to determined TNF-α and leptin levels. RT-qPCR was performed to measure the mRNA level of SOCS-3 and leptin in NPCs and western blotting was utilized to detect the protein level of leptin and the extent of leptin receptor phosphorylation. The results revealed that TNF-α levels in degenerative NPCs were higher than those in normal NPCs. The overexpression of SOCS-3 reduced levels of TNF-α and leptin in degenerative NPCs. In addition, the upregulation of leptin increased SOCS-3 levels in a concentration-dependent manner. Furthermore, the expression of the leptin receptor and phosphorylated leptin receptor gradually decreased with increasing leptin concentrations and the level of phosphorylated leptin receptor negatively correlated with SOCS-3 expression. The inductive effect of leptin on the level of SOCS-3 and the inhibitory effect of SOCS-3 on the activity of leptin were identified. The current study demonstrated that SOCS-3 reduces leptin and TNF-α levels in degenerative NPCs from adolescents, indicating its potential role in the development of novel SDD therapies.

Do Systemic Factors Influence the Fate of Nonunions to Become Atrophic? A Retrospective Analysis of 162 Cases

INTRODUCTION

Nonunions are a challenge for orthopedic surgeons. In hypertrophic nonunions, improvement of mechanical stability usually is the satisfactory treatment, whereas in atrophic nonunions improvement of the biological environment is most important. However, scientific evidence revealed that "avital" nonunions are not avascular and fibrous tissue contains cells with osteogenic potential. To find out if systemic factors suppress this intrinsic potential in atrophic nonunions, this study compares characteristics of hypertrophic with atrophic nonunion patients.

METHODS

We analyzed medical records of 162 surgically treated patients suffering from aseptic long bone nonunions. Atrophic and hypertrophic nonunions were distinguished by absence or presence of callus and calcification in the fracture gap. Mechanical implant loosening and patient characteristics such as age, gender, and body mass index were assessed. Fracture classification according to AO/OTA, open and closed fractures, and osteosynthesis were recorded. In addition, comorbidities and allergies between both groups were compared.

RESULTS

A higher number of hypertrophic nonunion patients were male with often allergies. Hypertrophic nonunion occurred more often after intramedullary nailing compared to atrophic nonunions. Atrophic nonunion patients being nonallergic were significantly older than nonallergic patients suffering from hypertrophic nonunions. In both atrophic and hypertrophic nonunion patients, age was lower in patients with accompanying injuries compared with age of patients with isolated fractures.

CONCLUSION

Systemic factors influence development of nonunion types. In nonallergic patients, atrophic nonunions occur more often in the elderly. This manuscript is a first step to identify different factors which might influence the nature of nonunion. To enable nonunion treatment which is tailored to individual patient characteristics, further prospective studies with more sophisticated research methods are necessary.

Systemic leptin administration alters callus VEGF levels and enhances bone fracture healing in wildtype and ob/ob mice

INTRODUCTION

Leptin's role in bone formation has been reported, however, its mechanism of affecting bone metabolism is remaining unclear. In this study, we aimed to test whether leptin has a positive effect on fracture healing through the possible mechanism of increasing vascular endothelial growth factor (VEGF) expression in callus tissue.

METHODS

Standardized femur fractures were created in leptin-deficient ob/ob and wildtype C57BL/6J mice, and recombinant mouse leptin or its vehicle (physiological saline) was administered intraperitoneally during the study. Body weight, radiological, histologic and immunoblotting analyses were performed at different stages of fracture healing.

KEY FINDINGS

The results showed that leptin treatment led to lower rate of body weight change in both mice genotypes. Radiological and histological analyses showed that the experimental groups had better fracture healing at 14, 21 and 28 days compared to the control groups. Leptin-treated groups had significantly higher VEGF expression in callus compared with the control groups at 2 and 3 weeks post-fracture except normal mice at 2 weeks, and leptin-deficient mice had higher VEGF levels in calluses than normal mice at the same timepoint.

CONCLUSION

Low-dose systemically-administered leptin has a positive effect on promoting fracture healing during the latter stages in a clinically-relevant mouse bone fracture model, and increase callus VEGF levels.

Immunological and morphological analysis of heterotopic ossification differs to healthy controls

Background

Formation of lamellar bone in non-osseus tissue is a pathological process called heterotopic ossification. It is the aim of this study to analyse the morphology and immunological status of patients with heterotopic ossification compared to individual healthy persons.

Methods

Human bone marrow and blood samples were obtained from 6 systemically healthy individuals and 4 patients during resection of heterotopic ossification from bone at hip arthroplasty. Bone was fragmented and treated with purified collagenase. Immunofluorescence surface staining was performed and analyzed with flow cytometry. Microcomputed tomography scanning was done performed at a resolution of 11 and 35 μm isometric voxel size respectively using a two different cone beam X-computer tomography systems and a microfocus X-ray tube. Subsequently the volume data was morphometrically analysed.

Results

The monocytes, stem cells, stroma cells and granulocytes progenitor cells were strongly reduced in the heterotopic ossification patient. Additionally a significant reduction of stromal stem cells cells and CD34 positive stem cells was observed. The frequency of NK-cells, B cells and T cells were not altered in the patients with heterotopic ossification compared to a healthy person. Micromorphometric parameters showed a lower content of mineralized bone tissue compared to normal bone. Mean trabecular thickness showed a high standard deviation, indicating a high variation in trabecular thickness, anisotropy and reducing bone strength.

Conclusions

This work shows altered immunological distribution that is accompanied by a low decrease in bone volume fraction and tissue mineral density in the heterotopic ossification sample compared to normal bone. Compared to healthy subjects, this might reflect an immunological participation in the development of this entity.

Level-Specific Differences in Systemic Expression of Pro- and Anti-Inflammatory Cytokines and Chemokines after Spinal Cord Injury

While over half of all spinal cord injuries (SCIs) occur in the cervical region, the majority of preclinical studies have focused on models of thoracic injury. However, these two levels are anatomically distinct—with the cervical region possessing a greater vascular supply, grey-white matter ratio and sympathetic outflow relative to the thoracic region. As such, there exists a significant knowledge gap in the secondary pathology at these levels following SCI. In this study, we characterized the systemic plasma markers of inflammation over time (1, 3, 7, 14, 56 days post-SCI) after moderate-severe, clip-compression cervical and thoracic SCI in a rat model. Using high-throughput ELISA panels, we observed a clear level-specific difference in plasma levels of VEGF, leptin, IP10, IL18, GCSF, and fractalkine. Overall, cervical SCI had reduced expression of both pro- and anti-inflammatory proteins relative to thoracic SCI, likely due to sympathetic dysregulation associated with higher level SCIs. However, contrary to the literature, we did not observe level-dependent splenic atrophy with our incomplete SCI model. This is the first study to compare the systemic plasma-level changes following cervical and thoracic SCI using level-matched and time-matched controls. The results of this study provide the first evidence in support of level-targeted intervention and also challenge the phenomenon of high SCI-induced splenic atrophy in incomplete SCI models.

Ankylosing Neurogenic Myositis Ossificans of the Hip: A Case Series and Review of Literature

Purpose

Neurogenic myositis ossificans (NMO) in patients with traumatic spinal cord or brain injuries can cause severe joint ankylosis or compromise neurovascularture. The purpose of this study was to evaluate the clinical and radiological outcomes of and review considerations relevant to surgical resection of NMO of the hip joint.

Materials and Methods

Six patients (9 hips) underwent periarticular NMO resection between 2015 and 2017. The medical records of these patients were retrospectively reviewed. Preoperative computed tomography including angiography was performed to determine osteoma location and size. Improvement in hip motion allowing sitting was considered the sole indicator of a successful surgery. The anterior approach was used in all patients. The ranges of motion (ROM) before and after surgery were compared.

Results

The mean time from accident to surgery was 3.6 years. Average ROM improved from 24.3°(flexion and extension) to 98.5°(flexion and extension) after surgery, and improvement was maintained at the last follow-up. No commom complications (e.g., deep infection, severe hematoma, deep vein thrombosis) occurred in any patient. Improvement in ROM in one hip in which surgical resection was performed 10 years after the accident was not satisfactory owing to the pathologic changes in the joint.

Conclusion

Surgical excision of periarticular NMO of the hip joint can yield satisfactory results, provided that appropriate preoperative evaluation is performed. Early surgical intervention yields satisfactory results and may prevent the development of intra-articular pathology.

The temporal expression of adipokines during spinal fusion

BACKGROUND CONTEXT

Adipokines are secreted by white adipose tissue and have been associated with fracture healing. Our goal was to report the temporal expression of adipokines during spinal fusion in an established rabbit model.

PURPOSE

Our goal was to report the temporal expression of adipokines during spinal fusion in an established rabbit model.

STUDY DESIGN

The study design included a laboratory animal model.

METHODS

New Zealand white rabbits were assigned to either sham surgery (n=2), unilateral posterior spinal fusion (n=14), or bilateral posterior spinal fusion (n=14). Rabbits were euthanized 1-6 and 10 weeks out from surgery. Fusion was evaluated by radiographs, manual palpation, and histology. Reverse transcription-polymerase chain reaction on the bone fusion mass catalogued the gene expression of leptin, adiponectin, resistin, and vascular endothelial growth factor (VEGF) at each time point. Results were normalized to the internal control gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (2^ΔCt), and control bone sites (2^ΔΔCt). Quantitative data were analyzed by two-factor analysis of variance (p<.05).

RESULTS

Manual palpation scores, radiograph scores, and histologic findings showed progression of boney fusion over time (p<.0003). The frequency of fusion by palpation after 4 weeks was 68.75%. Leptin expression in decortication and bone graft sites peaked at 5 weeks after the fusion procedure (p=.0143), adiponectin expression was greatest 1 week after surgery (p<.001), VEGF expression peaked at 4 weeks just after initial increases in leptin expression (p<.001), and resistin decreased precipitously 1 week after the fusion procedure (p<.001).

CONCLUSIONS

Leptin expression is likely associated with the maturation phase of bone fusion. Adiponectin and resistin may play a role early on during the fusion process. Our results suggest that leptin expression may be upstream of VEGF expression during spinal fusion, and both appear to play an important role in bone spinal fusion.

Relationship between heterotopic ossification and traumatic brain injury: Why severe traumatic brain injury increases the risk of heterotopic ossification

Heterotopic ossification (HO) is a pathological phenomenon in which ectopic lamellar bone forms in soft tissues. HO involves many predisposing factors, including congenital and postnatal factors. Postnatal HO is usually induced by fracture, burn, neurological damage (brain injury and spinal cord injury) and joint replacement. Recent studies have found that patients who suffered from bone fracture combined with severe traumatic brain injury (S-TBI) are at a significantly increased risk for HO occurrence. Thus, considerable research focused on the influence of S-TBI on fracture healing and bone formation, as well as on the changes in various osteogenic factors with S-TBI occurrence. Brain damage promotes bone formation, but the exact mechanisms underlying bone formation and HO after S-TBI remain to be clarified. Hence, this article summarises the findings of previous studies on the relationship between S-TBI and HO and discusses the probable causes and mechanisms of HO caused by S-TBI. The translational potential of this article: A better understanding of the probable causes of traumatic brain injury-induced HO can provide new perspectives and ideas in preventing HO and may support to design more targeted therapies to reduce HO or enhance the bone formation.

Mechanical Stress by Spasticity Accelerates Fracture Healing After Spinal Cord Injury

Accelerated fracture healing in patients with spinal cord injuries (SCI) is often encountered in clinical practice. However, there is no distinct evidence in the accelerated fracture healing, and the mechanisms of accelerated fracture healing in SCI are poorly understood. We aimed to determine whether SCI accelerated fracture healing in morphology and strength, to characterize the healing process with SCI, and to clarify the factors responsible for accelerated fracture healing. In total, 39 male Wistar rats were randomly divided into healthy control without intervention, SCI only, fracture with SCI, botulinum toxin (BTX) A-treated fracture with SCI, and propranolol-treated fracture with SCI groups. These rats were assessed with computed microtomography, histological, histomorphological, immunohistological, and biomechanical analyses. Both computed microtomography and histological analyses revealed the acceleration of a bony union in animals with SCI. The strength of the healed fractures after SCI recovered to the same level as that of intact bones after SCI, while the healed bones were weaker than the intact bones. Immunohistology revealed that SCI fracture healing was characterized by formation of callus with predominant intramembranous ossification and promoting endochondral ossification. The accelerated fracture healing after SCI was attenuated by BTX injection, but did not change by propranolol. We demonstrated that SCI accelerate fracture healing in both morphology and strength. The accelerated fracture healing with SCI may be due to predominant intramembranous ossification and promoting endochondral ossification. In addition, our results also suggest that muscle contraction by spasticity accelerates fracture healing after SCI.

Leptin Influences Healing in the Sprague Dawley Rat Fracture Model

Background

Leptin plays a crucial role in bone metabolism, and its level is related to bone callus formation in the fracture repair process. The objective of this study was to evaluate the effect of recombinant leptin on the healing process of femoral fractures in rats.

Material/Methods

Forty-eight male Sprague Dawley (SD) rats with an average body weight of 389 g (range: 376–398 g) and an average age of 10 weeks were included in this animal research, and all rats were randomly divided into two major groups. Then standardized femur fracture models were implemented in all SD rats. Rats in the control group were treated with only 0.5 mL of physiological saline, and rats in the experimental group were treated with recombinant leptin 5 μg/kg/d along with the same 0.5 mL of physiological saline for 42 days intraperitoneally. At the same time, each major group was evenly divided into three parallel subgroups for each parallel bone evaluation separately at the second, fourth, and sixth weeks. Each subgroup included eight rats.

Results

The total radiological evaluation results showed that the healing progress of femoral fracture in the experimental group was superior to that in the control group from the fourth week. At the sixth week, experimental group rats began to present significantly better femoral fracture healing progress than that of the control group rats. Results of biomechanics show the ultimate load (N) and deflection ultimate load (mm) of the experimental group rats was significantly increased compared with that of the control group rats from the fourth week.

Conclusions

Our results suggest that leptin may have a positive effect on SD rat femur fracture healing.

Effect of leptin combined with CoCl2 on healing in Sprague Dawley Rat fracture model

To evaluate the effect of leptin combined with CoCl₂ on rat femur fracture healing. 48 male Sprague Dawley rats were randomly divided into two main groups. Then standardized femur fractures were created to all rats. Control group rats were treated with 0.5 mL physiological saline, and experimental group rats were treated with 5 μg/Kg.d leptin and 15 mg/Kg.d CoCl₂ along with 0.5 mL physiological saline for 42 days intraperitoneally. Each main group was divided into three subgroups for each evaluation at second, fourth and sixth weeks, each subgroup included eight rats. The radiological evaluation showed that the fracture healing progress of experimental group was superior to control group from second week. At fourth week, experimental group had better fracture healing progress than control group significantly. Results of biomechanics show the ultimate load (N) and deflection ultimate load (mm) of experimental group was significantly increased than that in control group from fourth week. The present result demonstrated that leptin combined with CoCl₂ significantly increased the mRNA expression levels of HIF1A, Vegfa, Runx2, Bmp2, Bglap and Alpl. It suggested that leptin combined with CoCl₂ have a positive effect on rat femur fracture healing by activating the HIF1A pathway.

Effects of leptin on femoral fracture in rats

In this study, our objective was to evaluate effects of leptin on fracture healing in rats. Seventy two male Sprague-Dawley (SD) rats were randomized into 3 groups. Standardized femoral fractures were created in all the rats. Group A was treated with 1 mL normal saline (NS), group B with 0.3 μg/kg leptin in 1 mL NS, and group C with 0.5 μg/kg leptin in 1 mL NS for 2 weeks intraperitoneally. Each group was divided into three subgroups including 8 rats for evaluation at 2, 4 and 8 weeks. Radiological evaluation showed that callus formation of group B and C was all significantly higher than group A at 8 weeks (P=0.04 and P=0.013, respectively). There was no statistically significant difference in fracture healing between group B and group C at 8 weeks (P=0.197). Histological evaluation revealed fracture healing of group B and C was better than group A at 4 weeks (P=0.01 and P=0.002, respectively) and 8 weeks (P=0.008 and P=0.003, respectively). Micro-computed tomography (Micro-CT) analysis demonstrated that greater amounts of bony callus and evidence of bone fusion were observed in group B and C at 4 weeks (P=0.02 and P=0.04, respectively) and 8 weeks (P=0.005 and P=0.001, respectively) compared to group A. Group C also had better fracture healing than group B at 8 weeks (P=0.01). In conclusion, leptin has a positive effect on rat femoral fracture healing.

Serum leptin, bone mineral density and the healing of long bone fractures in men with spinal cord injury

Previously reported fracture rates in patients with spinal cord injury range from 1% to 20%. However, the exact role of spinal cord injury in bone metabolism has not yet been clarified. In order to investigate the effects of serum leptin and bone mineral density on the healing of long bone fractures in men with spinal cord injury, 15 male SCI patients and 15 matched controls were involved in our study. The outcome indicated that at 4 and 8 weeks after bone fracture, callus production in patients with spinal cord injury was lower than that in controls. Besides, bone mineral density was significantly reduced at 2, 4 and 8 weeks. In addition, it was found that at each time point, patients with spinal cord injury had significantly higher serum leptin levels than controls and no association was found between serum leptin level and bone mineral density of lumbar vertebrae. Moreover, bone mineral density was positively correlated with bone formation in both of the groups. These findings suggest that in early phases i.e. week 4 and 8, fracture healing was impaired in patients with spinal cord injury and that various factors participated in the complicated healing process, such as hormonal and mechanical factors.

Roles of leptin in bone metabolism and bone diseases

Adipose tissue has been more accepted as an active contributor to whole body homeostasis, rather than just a fat depot, since leptin, a 16 kDa protein, was discovered as the product of the obese gene in 1994. With more and more studies conducted on this hormone, it has been shown that there is a close relationship between adipose tissue and bone, which have important effects on each other. Bone is the source of many hormones, such as osteocalcin, that can affect energy metabolism and then the anabolism or catabolism of fat tissue. In contrast, the adipose tissue synthesizes and releases a series of adipokines, which are involved in bone metabolism through direct or indirect effects on bone formation and resorption. Interestingly, leptin, one of the most important cytokines derived from fat tissue, seems to account for the largest part of effects on bone, through direct or indirect involvement in bone remodeling and by playing a significant role in many bone diseases, such as osteoporosis, osteoarthritis, rheumatic arthritis, bone tumors and even fractures. In this review, we will discuss the progress in leptin research, particularly focusing on the roles of leptin in bone diseases.

Frequency of Dietary Recalls, Nutritional Assessment, and Body Composition Assessment in Men With Chronic Spinal Cord Injury

OBJECTIVES

To assess different frequencies of dietary recalls while evaluating caloric intake and the percentage of macronutrients in men with spinal cord injury (SCI) and to examine the relations between caloric intake or percentage of macronutrients and assessment of whole and regional body composition using dual-energy x-ray absorptiometry.

DESIGN

Cross-sectional and longitudinal.

SETTING

Laboratory and hospital.

PARTICIPANTS

Men with chronic (>1 y postinjury) motor complete SCI (N=16).

INTERVENTIONS

Participants were asked to turn in a 5-day dietary recall on a weekly basis for 4 weeks. The averages of 5-, 3-, and 1-day dietary recalls for caloric intake and percentage of macronutrients (carbohydrates, fat, protein) were calculated. Body composition was evaluated using whole-body dual-energy x-ray absorptiometry. After overnight fast, basal metabolic rate (BMR) was evaluated using indirect calorimetry and total energy expenditure (TEE) was estimated.

MAIN OUTCOME MEASURES

Caloric intake, percentage of macronutrients, BMR, and body composition.

RESULTS

Caloric intake and percentage of macronutrients were not different after using 5-, 3-, and 1-day dietary recalls (P>.05). Caloric intake was significantly lower than TEE (P<.05). The percentage of fat accounted for 29% to 34% of the whole and regional body fat mass (P=.037 and P=.022). The percentage of carbohydrates was positively related to the percentage of whole-body lean mass (r=.54; P=.037) and negatively related to the percentage of fat mass.

CONCLUSIONS

The frequency of dietary recalls does not vary while evaluating caloric intake and macronutrients. Total caloric intake was significantly lower than the measured BMR and TEE. Percentages of dietary fat and carbohydrates are related to changes in body composition after SCI.

The effects of spinal cord injury on bone healing in patients with femoral fractures

BACKGROUND

Orthopedic literature states that fractures of long bones, when associated with traumatic brain injuries, frequently heal with excessive callus and faster than normal. Few studies, however, have reported these phenomena being induced by spinal cord injury (SCI). Our objective is to compare the extent of callus and the rate of healing of long-bone fractures in patients with or without SCI. Subgroup comparisons were performed among the patients with SCI in terms of different levels of SCI.

METHODS

The final mean volume of callus formation and the rate of union of nailed fractures of the femur were determined radiologically in 22 femoral fracture patients with SCI (seven cervical, six thoracic, and nine lumbar spine injury) and compared with those in a group of 22 patients with similar types of fractures but without SCI.

RESULTS

The final mean callus volume in the fracture/SCI group was significantly higher than the fracture-only group (P < 0.001). The fractures in the fracture/SCI group united in an average time of 22.86 weeks compared with 25.04 weeks in the fracture-only group (P < 0.05). We observed 84.6% (11 of 13) of patients with cervical and thoracic SCI patients with accelerated fracture healing (cervical 6 of 7, thoracic 5 of 6), but only 44.4% (4 of 9) of patients with lumbar SCI appeared to show this phenomenon (P < 0.05).

CONCLUSIONS

These results confirm that SCI may be associated with accelerated fracture healing and enhanced callus formation. Furthermore, our study revealed a trend toward enhanced osteogenesis in cervical or thoracic SCI compared with lumbar SCI.

The temporal role of leptin within fracture healing and the effect of local application of recombinant leptin on fracture healing

OBJECTIVE

We hypothesized that leptin is expressed in a specific time sequence during fracture healing, and its deficiency leads to impaired healing.

METHODS

Control (C57BL/6) mice and leptin -/- obese (ob/ob) mice were used. ARM 1:: Fracture callus was harvested at 1, 3, 5, 7, 10, 14, and 21 days (n = 8/time point) after closed middiaphyseal femur fractures were created in 56 C57BL/6 mice, and reverse transcriptase polymerase chain reaction analysis was then performed. Levels of leptin were tracked at each time point listed. ARM 2:: Forty-two C57BL/6 controls and 42 ob/ob mice underwent open stabilized middiaphyseal femur fractures, and tissues were harvested at 14, 21, and 42 days and radiographic, histologic, and quantitative computerized tomography analyses were performed. ARM 3:: Murine recombinant leptin was applied directly at the newly created fracture site in 2 separate groups (10 or 100 μg of leptin) of 42 ob/ob mice. Two-factor analysis of variance and the Student t-test were used for statistical analysis.

RESULTS

The time course of Leptin mRNA expression within a fracture callus was detected. Delay in callus maturation was demonstrated radiographically and histologically in the ob/ob mice. ob/ob fractures had an increase in total callus volume by quantitative computerized tomography (P < 0.05). Application of local leptin at both doses reversed the delay in healing.

CONCLUSIONS

Leptin is expressed in a unique time course during fracture healing and leptin deficiency leads to impaired fracture healing that reverses by local application of leptin.

Neuroendocrine and cardiac metabolic dysfunction and NLRP3 inflammasome activation in adipose tissue and pancreas following chronic spinal cord injury in the mouse

CVD (cardiovascular disease) represents a leading cause of mortality in chronic SCI (spinal cord injury). Several component risk factors are observed in SCI; however, the underlying mechanisms that contribute to these risks have not been defined. Central and peripheral chronic inflammation is associated with metabolic dysfunction and CVD, including adipokine regulation of neuroendocrine and cardiac function and inflammatory processes initiated by the innate immune response. We use female C57 Bl/6 mice to examine neuroendocrine, cardiac, adipose and pancreatic signaling related to inflammation and metabolic dysfunction in response to experimentally induced chronic SCI. Using immuno-histochemical, -precipitation, and -blotting analysis, we show decreased POMC (proopiomelanocortin) and increased NPY (neuropeptide-Y) expression in the hypothalamic ARC (arcuate nucleus) and PVN (paraventricular nucleus), 1-month post-SCI. Long-form leptin receptor (Ob-Rb), JAK2 (Janus kinase)/STAT3 (signal transducer and activator of transcription 3)/p38 and RhoA/ROCK (Rho-associated kinase) signaling is significantly increased in the heart tissue post-SCI, and we observe the formation and activation of the NLRP3 (NOD-like receptor family, pyrin domain containing 3) inflammasome in VAT (visceral adipose tissue) and pancreas post-SCI. These data demonstrate neuroendocrine signaling peptide alterations, associated with central inflammation and metabolic dysfunction post-SCI, and provide evidence for the peripheral activation of signaling mechanisms involved in cardiac, VAT and pancreatic inflammation and metabolic dysfunction post-SCI. Further understanding of biological mechanisms contributing to SCI-related inflammatory processes and metabolic dysfunction associated with CVD pathology may help to direct therapeutic and rehabilitation countermeasures.

Heterotopic ossification after central nervous system trauma: A current review

Neurogenic heterotopic ossification (NHO) is a disorder of aberrant bone formation affecting one in five patients sustaining a spinal cord injury or traumatic brain injury. Ectopic bone forms around joints in characteristic patterns, causing pain and limiting movement especially around the hip and elbow. Clinical sequelae of neurogenic heterotopic ossification include urinary tract infection, pressure injuries, pneumonia and poor hygiene, making early diagnosis and treatment clinically compelling. However, diagnosis remains difficult with more investigation needed. Our pathophysiological understanding stems from mechanisms of basic bone formation enhanced by evidence of systemic influences from circulating humor factors and perhaps neurological ones. This increasing understanding guides our implementation of current prophylaxis and treatment including the use of non-steroidal anti-inflammatory drugs, bisphosphonates, radiation therapy and surgery and, importantly, should direct future, more effective ones.

Novel adipokines and bone metabolism

Osteoporosis is a serious social issue nowadays. Both the high morbidity and its common complication osteoporotic fracture load a heavy burden on the whole society. The adipose tissue is the biggest endocrinology organ that has a different function on the bone. The adipocytes are differentiated from the same cell lineage with osteoblast, and they can secrete multiple adipokines with various functions on bone remolding. Recently, several novel adipokines have been identified and investigated thoroughly. In this paper, we would like to highlight the complicated relation between the bone metabolism and the novel adipokines, and it may provide us with a new target for prediction and treatment of osteoporosis.