Tetraplegic subjects have hyperleptinaemia with marked circadian variation

The specificities, influencing factors, and medical implications of bone circadian rhythms

Physiological processes within the human body are regulated in approximately 24-h cycles known as circadian rhythms, serving to adapt to environmental changes. Bone rhythms play pivotal roles in bone development, metabolism, mineralization, and remodeling processes. Bone rhythms exhibit cell specificity, and different cells in bone display various expressions of clock genes. Multiple environmental factors, including light, feeding, exercise, and temperature, affect bone diurnal rhythms through the sympathetic nervous system and various hormones. Disruptions in bone diurnal rhythms contribute to the onset of skeletal disorders such as osteoporosis, osteoarthritis and skeletal hypoplasia. Conversely, these bone diseases can be effectively treated when aimed at the circadian clock in bone cells, including the rhythmic expressions of clock genes and drug targets. In this review, we describe the unique circadian rhythms in physiological activities of various bone cells. Then we summarize the factors synchronizing the diurnal rhythms of bone with the underlying mechanisms. Based on the review, we aim to build an overall understanding of the diurnal rhythms in bone and summarize the new preventive and therapeutic strategies for bone disorders.

Endocrinological and inflammatory markers in individuals with spinal cord injury: A systematic review and meta-analysis

Spinal cord injury (SCI) can lead to dramatic physiological changes which can be a factor in developing secondary health conditions and might be reflected in biomarker changes in this elevated risk group. We focused specifically on the endocrine and inflammation profile differences between SCI and able-bodied individuals (ABI). Our aim was to determine the differences in inflammatory markers and endocrine profiles between SCI and ABI. We systematically searched 4 electronic databases for relevant studies. Human observational (cross-sectional, cohort, case-control) studies that compared biomarkers of interest between SCI and ABI population were included. Weighted mean difference between SCI and ABI was calculated using random-effects models. Heterogeneity was computed using I² statistic and chi-squared test. Study quality was evaluated through the Newcastle-Ottawa Scale. The search strategy yielded a total of 2,603 studies from which 256 articles were selected for full-text assessment. Sixty-two studies were included in the meta-analysis. SCI individuals had higher levels of pro-inflammatory C-reactive protein and IL-6 than ABI. Creatinine and 25-hydroxyvitamin D₃ levels were lower in SCI than ABI. Total testosterone levels and IGF-1 were also found to be lower, while cortisol and leptin levels were higher in SCI when compared to ABI. Accordingly, meta-regression, subgroup analysis, and leave-one-out analysis were performed, however, they were only able to partially explain the high levels of heterogeneity. Individuals with SCI show higher levels of inflammatory markers and present significant endocrinological changes when compared to ABI. Moreover, higher incidence of obesity, diabetes, osteoporosis, and hypogonadism in SCI individuals, together with decreased creatinine levels reflect some of the readily measurable aspects of the phenotype changes in the SCI group. These findings need to be considered in anticipating medically related complications and personalizing SCI medical care.

Surgical management of lower limb fractures in patients with spinal cord injury less associated with complications than non-operative management: A retrospective series of cases

OBJECTIVES

To evaluate the difference in terms of overall complications between surgical and non-surgical management of lower limb fractures in patients with chronic spinal cord injury (SCI).

DESIGN

A 13-year retrospective study including patients with chronic spinal cord lesion admitted for sublesional lower limb fractures.

SETTING

University hospital SCI reference departments (Rehabilitation department and orthopedic department).

PARTICIPANTS

Forty patients with SCI were included, 24 men and 16 women. Fifty-six distinct fracture occurrences were responsible for a total of 59 lower limb fractures. We compared the number of overall complications between surgical and non-surgical management of fractures.

RESULTS

Non-surgical management was realized for 19 fractures and surgery for 40. Characteristics of operated and non-operated patients at the time of each fracture occurrence did not differ concerning age (P = 0.430), sex (P = 0.890), lesion levels (P = 0.410) and AIS classification (P = 0.790). Data analysis highlighted 20 complications directly due to the fracture site for 16 distinct fractures. Seven medical complications were found in 5 distinct fracture events. Only 10 (25.0%) of 40 surgical managements had at least one medical or post-surgical complication, whereas 12 (63.2%) of 19 non-operative managements had at least one complication. Therefore, the overall rate of complications was significantly higher after non-surgical treatment (P = 0.044).

CONCLUSION

Lower extremity fractures due to osteoporosis in patients with SCI are responsible for local and general complications. When possible, surgery may be the best management to propose because of fewer overall complications.

Abnormal adipokine levels and leptin-induced changes in gene expression profiles in multiple myeloma

BACKGROUND

Studies have revealed an association between overweight/obesity and multiple myeloma. However, the factors linking a dysregulated energy metabolism to this disease have not been identified. Adipose tissue produces and secretes the adipokines leptin, adiponectin and resistin, involved in metabolism and cell growth.

METHODS

We measured the plasma concentrations of these three adipokines in newly diagnosed multiple myeloma as well as in patients with relapse. We further explored the importance of leptin in multiple myeloma by performing gene expression profiling in two myeloma cell lines.

RESULTS

At diagnosis, leptin was increased (P < 0.05) in both female and male patients compared with controls. Adiponectin was reduced (P < 0.05) among male patients, whereas no significant changes in resistin were noted among any patients. In patients with relapse and treated with thalidomide, no particular adipokine pattern was revealed. Leptin induced the expression of several genes important for cell signaling, growth and viability.

CONCLUSIONS

The plasma concentrations of leptin and adiponectin, but not resistin, were abnormal in newly diagnosed multiple myeloma. Adipose tissue may modify the growth and metabolism of myeloma cells through adipokine-mediated effects.

Changes of substance P-immunoreactive nerve fiber innervation density in the sublesional bones in young growing rats at an early stage after spinal cord injury

Spinal cord injury (SCI) causes osteoporosis (OP), and the neuropeptide substance P (SP) may play important roles in the pathogenesis of OP after SCI. Our study confirmed SCI-induced sublesional bone loss in young rats at an early stage is associated with a significant increase of SP-immunoreactive nerve fiber innervation density.

INTRODUCTION

Spinal cord injury (SCI) causes osteoporosis (OP), and neuropeptides may play important roles in the pathogenesis of OP after SCI. However, few data exist concerning the relationship between neural factors and OP following SCI.

METHODS

One hundred and eight SCI and hindlimb cast immobilization (HCI) rats were studied for skeletal innervation of substance P (SP) and neurofilament 200 (NF200) with immunocytochemistry. Bone and serum SP levels were also assessed using enzyme immunoassay.

RESULTS

Developing bone loss was successfully induced by SCI at 3 wks and by HCI at 6 wks. We observed a significant increase of SP-immunoreactive (IR) nerve fibers and decrease of NF200-IR nerve fibers in the tibiae of SCI rats compared with HCI and control (CON) rats at all time points. SP in the proximal tibiae in SCI rats was significantly higher than that in HCI and CON rats at all time points, but no difference was found in the serum.

CONCLUSION

SCI-induced sublesional bone loss in young rats at an early stage is associated with a significant increase of nerve fiber innervation density of SP-IR and decrease of NF200-IR. We speculated that neural factors may play an important role in pathogenesis of OP after SCI.

Effects of spinal cord injury on osteoblastogenesis, osteoclastogenesis and gene expression profiling in osteoblasts in young rats

INTRODUCTION

Spinal cord injury (SCI) causes a significant amount of bone loss in the sublesional area in animals and humans, and this type of bone loss is different from other forms of osteoporosis such as disuse osteoporosis and postmenopausal osteoporosis. However, no data is available on the cellular and molecular changes of osteoblastogenesis and osteoclastogenesis during SCI-induced bone loss.

METHODS

SCI and SHAM rats were used in this study to investigate osteoblastogenesis and osteoclastogenesis in bone-marrow culture. We also measured bone mass and bone histomorphometry, as well as the expression of alkaline phosphatase (ALP), core binding factor alpha1 (Cbfa-1), osterix, receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) in osteoblast-like cells in bone-marrow culture obtained from SCI and SHAM rats.

RESULTS

Bone mineral density (BMD) measurement showed serious bone loss in the tibial ephiphyses and metaphyses of SCI rats compared with SHAM rats. In addition, bone histomorphometry analysis of the tibial metaphyses of SCI rats demonstrated that bone microarchitecture in SCI rats deteriorated further than in SHAM rats, and increased eroded surfaces and bone formation rates were observed in SCI rats. The number of osteoclasts that developed from bone marrow of SCI rats at equal density was significantly increased compared with SHAM rats, and the area of the resorption pits formed in the bone marrow culture from SCI rats was significantly greater than SHAM rats, whereas the number of CFU-F and CFU-OB was similar in both groups. RANKL mRNA and protein levels in osteoblast-like cells in culture obtained from SCI rats were significantly higher than those from the SHAM rats, whereas OPG levels decreased slightly. The ratios of RANKL to OPG expression in SCI rats were significantly higher than those in SHAM rats. However, osteogenic gene profiling of Cbfa-1, ALP and osterix in SCI rats remained similar with SHAM rats.

CONCLUSION

These changes favor increased osteoclast activity over osteoblast activity, and may explain, in part, the imbalance in bone formation and resorption following SCI.

Mechanisms of osteoporosis in spinal cord injury

Osteoporosis is a known complication of spinal cord injury (SCI), but its mechanism remains unknown. The pathogenesis of osteoporosis after SCI is generally considered disuse. However, although unloading is an important factor in the pathogenesis of osteoporosis after SCI, neural lesion and hormonal changes also seem to be involved in this process. Innervation and neuropeptides play an important role in normal bone remodelling. SCI results in denervation of the sublesional bones and the neural lesion itself may play a pivotal role in the development of osteoporosis after SCI. Although upper limbs are normally loaded and innervated, bone loss also occurs in the upper extremities in patients with paraplegia, indicating that hormonal changes may be associated with osteoporosis after SCI. SCI-mediated hormonal changes may contribute to osteoporosis after SCI by different mechanisms: (1) increased renal elimination and reduced intestinal absorption of calcium leading to a negative calcium balance; (2) vitamin D deficiency plays a role in the pathogenesis of SCI-induced osteoporosis; (3) SCI antagonizes gonadal function and inhibits the osteoanabolic action of sex steroids; (4) hyperleptinaemia after SCI may contribute to the development of osteoporosis; (5) pituitary suppression of TSH may be another contributory factor to bone loss after SCI; and (6) bone loss after SCI may be caused directly, at least in part, by insulin resistance and IGFs. Thus, oversupply of osteoclasts relative to the requirement for bone resorption and/or undersupply of osteoblasts relative to the requirement for cavity repair results in bone loss after SCI. Mechanisms for the osteoporosis following SCI include a range of systems, and osteoporosis after SCI should not be simply considered as disuse osteoporosis. Unloading, neural lesion and hormonal changes after SCI result in severe bone loss. The aim of this review is to improve understanding with regard to the mechanisms of osteoporosis after SCI. The understanding of the pathogenesis of osteoporosis after SCI can help in the consideration of new treatment strategies. Because bone resorption after SCI is very high, intravenous bisphosphonates and denosumab should be considered for the treatment of osteoporosis after SCI.

Spinal cord injury causes more damage to bone mass, bone structure, biomechanical properties and bone metabolism than sciatic neurectomy in young rats

INTRODUCTION

Although both spinal cord injury (SCI) and sciatic neurectomy (NX) can cause osteopaenia in young rats, the effects of these two injuries on cortical and cancellous bone may differ. The objective of this study was to compare the effects of SCI and NX on bone weight, bone material property, bone mass, bone geometry, trabecular microarchitecture, mechanical strength and bone turnover in young rats.

MATERIALS AND METHODS

Thirty six-week-old male Sprague-Dawley rats were randomised into three groups (10 per group): SCI, bilateral sciatic NX and untreated control (CON). All rats were killed on day 21. Bone mineral density (BMD) was studied using dual-energy X-ray absorptiometry (DXA). At death, the right proximal tibial metaphysis and the fourth lumbar vertebra were examined for bone structural geometric analysis by micro-computed tomography (CT) and then processed for histomorphometry to assess bone cell activity. Serum N-terminal telopeptide of type I collagen (NTX) and osteocalcin (OC) levels were analysed by enzyme-linked immunosorbent assay (ELISA). Biomechanical strength properties of the femur and humerus were measured by three-point bending, and the third lumbar vertebra and the proximal end of tibia were tested by compression.

RESULTS

BMD in the sublesional areas of SCI rats was significantly lower than that of NX rats (proximal tibia, 0.176+/-0.018 g/cm(2) vs. 0.224+/-0.015 g/cm(2), P<0.001). Bone volume (BV/TV), trabecular number (Tb.N) and thickness (Tb.Th) in the tibial second spongiosa of SCI rats were significantly less than those in NX rats (BV/TV: 7.15+/-1.18% vs. 12.32+/-1.83%, P<0.001; Tb.N: 1.23+/-0.22 vs. 2.38+/-0.45, P<0.001; Tb.Th: 33.73+/-5.15 microm vs. 42.80+/-7.44 microm, P<0.01) and trabecular separation (Tb.Sp: 1,053.37+/-164.24 microm vs. 748.32+/-129.36 microm, P<0.01) was significantly greater than in NX rats. Furthermore, poorer trabecular connectivity was found in SCI rats than in NX rats (number of nodes, N.Nd/TV: 1.04+/-0.09 vs. 3.29+/-0.53; number of terminus, N.Tm/TV: 28.53+/-3.17 vs. 21.64+/-2.31, P<0.01). The bone formation rate of the tibial second spongiosa in SCI rats was significantly higher than in NX rats (2.06+/-0.13 vs. 1.53+/-0.09, P<0.001) and, also, the eroded surface in SCI rats was significantly higher than in NX rats (13.42+/-1.24 vs. 10.36+/-1.07, P<0.001). In addition, biomechanical tests showed that SCI rats had poorer biomechanical properties of the femur, proximal tibia and fourth lumbar vertebra than in NX rats. There were significantly higher levels of OC in SCI rats compared with NX rats (30.19+/-1.17 vs. 21.15+/-1.76, P<0.001). Also, serum NTX levels were significantly higher than in NX rats (51.60+/-2.61 vs. 33.85+/-1.93, P<0.001).

CONCLUSION

SCI caused more damage to bone mass, bone structure, biomechanical properties and bone metabolism than NX in young rats. This suggests that different mechanisms may underlie osteopaenia following SCI and NX.

Differences in circadian variations of tissue factor pathway inhibitor type 1 between able-bodied and spinal cord injured

INTRODUCTION

Tissue factor pathway inhibitor type 1 (TFPI) is the physiological inhibitor of the tissue factor pathway of coagulation. TFPI is produced by endothelial cells, and most intravascular TFPI is composed of full-length TFPI associated with the endothelium. Circulating TFPI is mainly truncated and lipoprotein-associated, but a small fraction circulates in a free full-length form. Although hormonal state influences the plasma variation of TFPI between individuals, other factors like temporal variation may be important. Hence, in the current study we aimed at exploring the intra-individual variation with focus on the possible circadian variations of TFPI.

MATERIALS AND METHODS

TFPI free and total antigen from 8 able-bodied and 6 tetraplegic men were measured at 12 time points during a 24 h period.

RESULTS

TFPI free antigen in the able-bodied exhibited circadian variation with the highest levels (approximately 20% above mean) from 12:00 to 18:00 h and the lowest levels (approximately 15% below mean) at 09:00 and 02:00 h. In contrast, TFPI free antigen in the tetraplegic group showed no circadian variation. TFPI total antigen exhibited circadian variation in neither group, but mean TFPI total antigen was lower in the tetraplegic group compared with the able-bodied (80 versus 110 ng/mL, respectively). Notably, even if TFPI total antigen in both groups did not vary according to any specific circadian rhythm, the intra-individual variation was higher than the assay variation.

CONCLUSION

TFPI free antigen exhibited circadian variations in able-bodied, but not in tetraplegic subjects and the able-bodied had higher levels of TFPI total antigen than the tetraplegic group.