High Serum Insulin-Like Growth Factor-Binding Protein 1 (IGFBP-1) is Associated with High Fracture Risk Independent of Insulin-Like Growth Factor 1 (IGF-I)

A Multifunctional Therapeutic Strategy Using P7C3 as A Countermeasure Against Bone Loss and Fragility in An Ovariectomized Rat Model of Postmenopausal Osteoporosis

By 2060, an estimated one in four Americans will be elderly. Consequently, the prevalence of osteoporosis and fragility fractures will also increase. Presently, no available intervention definitively prevents or manages osteoporosis. This study explores whether Pool 7 Compound 3 (P7C3) reduces progressive bone loss and fragility following the onset of ovariectomy (OVX)-induced osteoporosis. Results confirm OVX-induced weakened, osteoporotic bone together with a significant gain in adipogenic body weight. Treatment with P7C3 significantly reduced osteoclastic activity, bone marrow adiposity, whole-body weight gain, and preserved bone area, architecture, and mechanical strength. Analyses reveal significantly upregulated platelet derived growth factor-BB and leukemia inhibitory factor, with downregulation of interleukin-1 R6, and receptor activator of nuclear factor kappa-B (RANK). Together, proteomic data suggest the targeting of several key regulators of inflammation, bone, and adipose turnover, via transforming growth factor-beta/SMAD, and Wingless-related integration site/be-catenin signaling pathways. To the best of the knowledge, this is first evidence of an intervention that drives against bone loss via RANK. Metatranscriptomic analyses of the gut microbiota show P7C3 increased Porphyromonadaceae bacterium, Candidatus Melainabacteria, and Ruminococcaceae bacterium abundance, potentially contributing to the favorable inflammatory, and adipo-osteogenic metabolic regulation observed. The results reveal an undiscovered, and multifunctional therapeutic strategy to prevent the pathological progression of OVX-induced bone loss.

Association of TNF-α, IGF-1, and IGFBP-1 levels with the severity of osteopenia in mice with nonalcoholic fatty liver disease

BACKGROUNDS

Nonalcoholic fatty liver disease (NAFLD) exhibits a close association with osteoporosis. This work aims to assess the potential effects of NAFLD on the progression of osteopenia in animal models.

METHODS

Forty-eight C57BL/6 female mice were randomly divided to wild-type (WT) group and high-fat diet (HFD) group. The corresponding detections were performed after sacrifice at 16, 24 and 32 weeks, respectively.

RESULTS

At 16 weeks, an remarkable increase in body weight and lipid aggregation in the hepatocytes of HFD group was observed compared to the WT group, while the bone structure parameters showed no significant difference. At 24 weeks, the levels of TNF-α and IL-6 in NAFLD mice were significantly increased, while the level of osteoprotegerin mRNA in bone tissue was decreased, and the level of receptor activator of nuclear factor Kappa-B ligand mRNA was increased. Meanwhile, the function of osteoclasts was increased, and the bone microstructure parameters showed significant changes. At 32 weeks, in the HFD mice, the mRNA levels of insulin-like growth factor-1 (IGF-1), runt-related transcription factor 2, and osterix mRNA were reduced, while the insulin-like growth factor binding protein-1 (IGFBP-1) level was increased. Simultaneously, the osteoblast function was decreased, and the differences of bone structure parameters were more significant, showing obvious osteoporosis.

CONCLUSIONS

The bone loss in HFD mice is pronounced as NAFLD progresses, and the changes of the TNF-α, IL-6, IGF-1, and IGFBP-1 levels may play critical roles at the different stages of NAFLD in HFD.

Association between self-rated health and the risk of hip fracture and mortality in a cohort of older women during a 10-year follow-up

Fragility fracture of the hip is associated with reduced functional status and mortality. Poor self-rated health (SRH) might be such an indicator. Our aim was to study if SRH was associated with hip fractures and all-cause mortality within the next 10 years in community-dwelling older women. A population-based sample of 350 women aged between 69 and 79 years (median 72.4) assessed their SRH by answering the question "How would you rate your health right now" by putting a mark on a visual-analogue scale (0-100 mm). Information on hip fracture and mortality over the next 10 years was retrieved from health care registers. The association between SRH and hip fracture and all-cause mortality was tested with a Cox proportional hazards regression model. SRH was divided into low, intermediate, and high (reference) assessed SRH. During the study, 40 hip fractures and 72 deaths occurred. The median value of SRH was 62 mm (IQR 50-81 mm). The age-adjusted hazard ratio (HR) for hip fracture was significantly higher in the group with low and intermediate SRH; HR: 3.17 (95% CI 1.25-8.01), and HR: 2.75 (95% CI 1.08-7.04), compared with high SRH. Adding bone mineral density (at the femoral neck) gave even greater risk. We did not find the hypothesized association between SRH and mortality. In our study, SRH indicated a higher risk of future hip fracture in older women. SRH might be a marker that could add information about the risk of hip fracture independently of bone mineral density.

Wear of hip prostheses increases serum IGFBP-1 levels in patients with aseptic loosening

The biological mechanisms involved in aseptic loosening include inflammation-associated and bone resorption-associated processes. Coordinated cellular actions result in biochemical imbalances with devastating consequences for the joint. Given that this condition is not known for showing systemic signs, we investigated whether circulating levels of inflammation-related proteins are altered in patients with aseptic loosening. Our study included 37 patients who underwent revision surgery due to hip osteolysis and aseptic loosening and 31 patients who underwent primary total hip arthroplasty. Using antibody arrays, we evaluated the serum levels of 320 proteins in four patients from each group. The results showed differences in insulin-like growth factor-binding protein 1 (IGFBP-1) concentrations, which we then quantified using enzyme-linked immunosorbent assay tests in all study patients. The results confirmed that serum IGFBP-1 concentrations were higher in the revision surgery patients than in the hip arthroplasty patients. In vitro studies showed that exposure of human osteoblasts to titanium particles induced an IGFBP-1 release that further increased when exposure to particles was performed in media conditioned by human M1 macrophages. These findings suggest that elevated serum IGFBP-1 levels in patients with aseptic loosening can arise from increased local IGFBP-1 production in the inflammatory environment of the periprosthetic bed.

Age-related bone loss is associated with FGF21 but not IGFBP1 in healthy adults

What is the central question of this study? Fibroblast growth factor 21 (FGF21) plays important therapeutic roles in metabolic diseases but is associated with bone loss, through insulin-like growth factor binding protein 1 (IGFBP1), in animals. However, the effect of the FGF21-IGFBP1 axis on age-related bone loss has not been explored in humans. What is the main finding and its importance? Using 'genetically linked' parent and child family pairs, we show that the FGF21 concentration, but not the IGFBP1 concentration, is higher in older than in younger adults. Our results suggest that age-associated decline in bone mineral density is associated with FGF21 and increased bone turnover but not likely to involve IGFBP1 in healthy humans. ABSTRACT: Bone fragility increases with age. The fibroblast growth factor 21 (FGF21)-insulin-like growth factor binding protein 1 (IGFBP1) axis regulates bone loss in animals. However, the role of FGF21 in mediating age-associated bone fragility in humans remains unknown. The purpose of this study was to explore the FGF21-regulatory axis in bone turnover and the age-related decline in bone mineral density (BMD). Twenty 'genetically linked' family (parent and child) pairs were recruited. Younger adults were 22-39 years old and older adults 60-71 years old. The BMD and serum concentrations of FGF21, IGFBP1, receptor activator of nuclear factor-κB ligand (RANKL), tartrate-resistant acid phosphatase 5b (TRAP5b) and bone-specific alkaline phosphatase (BAP) were measured. Older adults had 10-18% lower BMD at the hip and spine (P < 0.008) and a twofold higher FGF21 concentration (P < 0.001). The IGFBP1 concentration was similar in younger and older adults (P = 0.961). The RANKL concentration was 44% lower (P = 0.006), whereas TRAP5b and BAP concentrations were 36 and 31% higher (P = 0.01 and P = 0.004), respectively, in older adults than in younger adults. Adjusting for sex did not affect these results. The FGF21 concentration was negatively correlated with BMD at the spine (r = -0.460, P = 0.003), but not with the IGFBP1 concentration (r = -0.144, P = 0.374). The IGFBP1 concentration was not correlated with BMD at the hip or spine (all P > 0.05). In humans, FGF21 might be involved in the age-associated decline in BMD, especially at the spine, through increased bone turnover. IGFBP1 is unlikely to be the downstream effector of FGF21 in driving the age-associated decline in BMD and in RANKL-associated osteoclast differentiation.

Role of IGF1 and EFN-EPH signaling in skeletal metabolism

Insulin-like growth factor 1(IGF1) and ephrin ligand (EFN)-receptor (EPH) signaling are both crucial for bone cell function and skeletal development and maintenance. IGF1 signaling is the major mediator of growth hormone-induced bone growth, but a host of different signals and factors regulate IGF1 signaling at the systemic and local levels. Disruption of the Igf1 gene results in reduced peak bone mass in both experimental animal models and humans. Additionally, EFN-EPH signaling is a complex system which, particularly through cell-cell interactions, contributes to the development and differentiation of many bone cell types. Recent evidence has demonstrated several ways in which the IGF1 and EFN-EPH signaling pathways interact with and depend upon each other to regulate bone cell function. While much remains to be elucidated, the interaction between these two signaling pathways opens a vast array of new opportunities for investigation into the mechanisms of and potential therapies for skeletal conditions such as osteoporosis and fracture repair.

Role of IGF-binding proteins in regulating IGF responses to changes in metabolism

The IGF-binding protein family contains six members that share significant structural homology. Their principal function is to regulate the actions of IGF1 and IGF2. These proteins are present in plasma and extracellular fluids and regulate access of both IGF1 and II to the type I IGF receptor. Additionally, they have functions that are independent of their ability to bind IGFs. Each protein is regulated independently of IGF1 and IGF2, and this provides an important mechanism by which other hormones and physiologic variables can regulate IGF actions indirectly. Several members of the family are sensitive to changes in intermediary metabolism. Specifically the presence of obesity/insulin resistance can significantly alter the expression of these proteins. Similarly changes in nutrition or catabolism can alter their synthesis and degradation. Multiple hormones such as glucocorticoids, androgens, estrogen and insulin regulate IGFBP synthesis and bioavailability. In addition to their ability to regulate IGF access to receptors these proteins can bind to distinct cell surface proteins or proteins in extracellular matrix and several cellular functions are influenced by these interactions. IGFBPs can be transported intracellularly and interact with nuclear proteins to alter cellular physiology. In pathophysiologic states, there is significant dysregulation between the changes in IGFBP synthesis and bioavailability and changes in IGF1 and IGF2. These discordant changes can lead to marked alterations in IGF action. Although binding protein physiology and pathophysiology are complex, experimental results have provided an important avenue for understanding how IGF actions are regulated in a variety of physiologic and pathophysiologic conditions.

High insulin-like growth factor-binding protein-1 (IGFBP-1) is associated with low relative muscle mass in older women

OBJECTIVE

Skeletal muscles serve several important roles in maintaining good health. Insulin-like growth factor-1 (IGF-1) is a promoter of protein synthesis in skeletal muscle. Its binding protein, Insulin-like growth factor-binding protein-1 (IGFBP-1) can be one determinant of IGF-1 activity. In the present study we investigate the association between serum IGFBP-1 and muscle mass.

DESIGN

Cross-sectional analysis of 4908 women, between 55 and 85years old, participating in the Swedish Mammography Cohort-Clinical.

METHODS

We defined low relative muscle mass (LRMM) as an appendicular lean mass divided by height squared of less than 5.45 (kg/m²), assessed by dual energy x-ray absorptiometry. IGFBP-1 was measured by radioimmunoassay. Logistic regression was used to calculate odds-ratios of LRMM across quartiles of IGFBP-1.

RESULTS

The odds of LRMM increased across quartiles of IGFBP-1. In the age-adjusted model the odds-ratio (OR) of LRMM was 3.41 (95% CI: 2.55-4.56), comparing the highest to the lowest quartile. This estimate was attenuated in multivariate models (OR: 1.84, 95% CI: 1.34-2.53), mainly due to inclusion of fat mass index.

CONCLUSION

Women with higher IGFBP-1 were more likely to have a low relative muscle mass. High IGFBP-1 may be a marker of a catabolic state.

Uremic Toxicity and Bone in CKD

Patients with chronic kidney disease (CKD), especially those on dialysis treatment, are at high risk of bone fracture. In CKD-mineral and bone disorder (CKD-MBD), secondary hyperparathyroidism in patients with advanced CKD induces bone abnormalities, and skeletal resistance to parathyroid hormone (PTH) starts in the early stages of kidney disease. Uremic toxins such as indoxyl sulfate and p-cresyl sulfate reduce the expression of PTH receptor as well as PTH-induced cyclic adenosine 3',5' monophosphate production in osteoblasts. CKD also impairs bone strength, especially quality. In a rat model, kidney damage reduces the bone-storage modulus and changes the cortical bone chemical composition with or without hyperparathyroidism. The oral charcoal adsorbent AST-120 improves CKD-induced bone abnormalities as blood levels of indoxyl sulfate decrease. Uremic osteoporosis, a new concept of CKD-related bone fragility, is a main cause of CKD-induced bone abnormalities, particularly impaired bone quality. There is limited information about the effect and safety of anti-osteoporotic drugs for patients with CKD, especially those on dialysis, but the use of AST-120 and renin-angiotensin system inhibitors may modulate bone quality and decrease the incidence of fracture. Thus, the management of CKD-MBD plus use of other therapeutic interventions for uremic osteoporosis is necessary to prevent bone fragility in patients with CKD.