Serum Levels of Insulin-Like Growth Factor-I Are Positively Associated with Functional Outcome After Hip Fracture in Elderly Women

Insulin-like growth factor-1 promotes osteogenic differentiation and collagen I alpha 2 synthesis via induction of mRNA-binding protein LARP6 expression

This study explored the mechanism underlying the stimulation of collagen synthesis and osteoblastic differentiation by insulin-like growth factor 1 (IGF1) in primary mouse osteoblasts. Primary mouse calvarial osteoblasts were cultured and treated with various doses of IGF1 before transfection with siRNA targeting the collagen type I alpha 2 (Col1a2) or La ribonucleoprotein domain family member 6 (Larp6) genes. Alkaline phosphatase (ALP) activity, osteocalcin staining, alizarin red quantification and the expression level of runt-related transcription factor 2 (RUNX2) were performed to assess the differentiation of pre-osteoblasts. Based on Western blot analysis, IGF1 up-regulated COL1A2 protein expression in the primary osteoblasts in a dose- and time-dependent manner. In addition, Col1a2 interference inhibited the differentiation and mineralization of osteoblasts. IGF1 also stimulated the differentiation of mouse primary osteoblasts and increased LARP6 expression during osteogenic differentiation. RNA-Immunoprecipitation (IP) indicated that LARP6 could bind to Col1a2 mRNA after IGF1 stimulation. However, transfection of Larp6-specific siRNA significantly reduced collagen and ALP secretion, mineralization and inhibited the expression of osteocalcin and RUNX2, indicating that Larp6 interference inhibited the differentiation ability of primary mouse calvarial osteoblasts, and these effects could not be reversed by IGF1. Thus, IGF1 could promote COL1A2 expression and osteoblast differentiation in primary mouse calvarial pre-osteoblasts by increasing LARP6 expression via a posttranscriptional mechanism.

Effect of GH/IGF-1 on Bone Metabolism and Osteoporsosis

Background. Growth hormone (GH) and insulin-like growth factor (IGF-1) are fundamental in skeletal growth during puberty and bone health throughout life. GH increases tissue formation by acting directly and indirectly on target cells; IGF-1 is a critical mediator of bone growth. Clinical studies reporting the use of GH and IGF-1 in osteoporosis and fracture healing are outlined. Methods. A Pubmed search revealed 39 clinical studies reporting the effects of GH and IGF-1 administration on bone metabolism in osteopenic and osteoporotic human subjects and on bone healing in operated patients with normal GH secretion. Eighteen clinical studies considered the effect with GH treatment, fourteen studies reported the clinical effects with IGF-1 administration, and seven related to the GH/IGF-1 effect on bone healing. Results. Both GH and IGF-1 administration significantly increased bone resorption and bone formation in the most studies. GH/IGF-1 administration in patients with hip or tibial fractures resulted in increased bone healing, rapid clinical improvements. Some conflicting results were evidenced. Conclusions. GH and IGF-1 therapy has a significant anabolic effect. GH administration for the treatment of osteoporosis and bone fractures may greatly improve clinical outcome. GH interacts with sex steroids in the anabolic process. GH resistance process is considered.

Parathyroid hormone response to severe vitamin D deficiency is sex associated: an observational study of 571 hip fracture inpatients

OBJECTIVES

To investigate the association between sex and parathyroid hormone response to severe vitamin D deficiency after hip fracture.

DESIGN

Cross-sectional study.

SETTING

Rehabilitation hospital in Italy.

PARTICIPANTS

571 consecutive inpatients with hip fracture and severe vitamin D deficiency (serum 25-hydroxyvitamin D < 12ng/ml), without hypercalcemia or estimated glomerular filtration rate (GFR) < 15ml/min.

MEASUREMENTS

In each patient we assessed PTH (by two-site chemiluminescent enzyme-labelled immunometric assay), 25-hydroxyvitamin D (by immunoenzymatic assay), albumin-adjusted total calcium, phosphate, magnesium, and creatinine 21.3 ± 6.1 (mean ± SD) days after fracture occurrence. Functional level was assessed using the Barthel index. PTH response to vitamin D deficiency was classified as either secondary hyperparathyroidism (serum PTH >75pg/ml) or functional hypoparathyroidism, i.e., inappropriate normal levels of PTH (≤75pg/ml).

RESULTS

Among the 571 patients, 336 (59%) had functional hypoparathyroidism, whereas 235 (41%) had secondary hyperparathyroidism. PTH status was significantly different between sexes (p=0.003): we found functional hypoparathyroidism in 61% of women and 43% of men (secondary hyperparathyroidism in 39% of women and 57% of men). The significance of the between-sex difference was maintained after adjustment for age, estimated GFR, phosphate, albumin-adjusted total calcium, albumin, Barthel index scores, 25-hydroxyvitamin D, and hip fracture type (either cervical or trochanteric). The adjusted odds ratio was 1.85 (95%CI from 1.09 to 3.13; p=0.023).

CONCLUSIONS

Data shows that PTH response to vitamin D deficiency was sex-associated following a fracture of the hip. The higher prevalence of secondary hyperparathyroidism may play a role in the known prognostic disadvantage found in hip-fracture men.

Systemically delivered insulin-like growth factor-I enhances mesenchymal stem cell-dependent fracture healing

In this study, we examined the effectiveness of systemic subcutaneous delivery of recombinant Insulin-like growth factor (IGF)-I concurrently with primary cultured bone marrow-derived mesenchymal stem cell (MSC) transplant on fracture repair. We found that the fracture callus volume increased in mice with a stabilized tibia fracture that received IGF-I+MSC when compared with that in either untreated or MSC alone treated mice. In evaluating the callus tissue components, we found that the soft and new bone tissue volumes were significantly increased in IGF-I+MSC recipients. Histological and in-situ hybridization analyses confirmed a characteristic increase of newly forming bone in IGF-I+MSC recipients and that healing progressed mostly through endochondral ossification. The increase in soft and new bone tissue volumes correlated with increased force and toughness as determined by biomechanical testing. In conclusion, MSC transplant concurrent with systemic delivery of IGF-I improves fracture repair suggesting that IGF-I+MSC could be a novel therapeutic approach in patients who have inadequate fracture repair.

Mesenchymal stem cells expressing insulin-like growth factor-I (MSCIGF) promote fracture healing and restore new bone formation in Irs1 knockout mice: analyses of MSCIGF autocrine and paracrine regenerative effects

Failures of fracture repair (nonunions) occur in 10% of all fractures. The use of mesenchymal stem cells (MSC) in tissue regeneration appears to be rationale, safe, and feasible. The contributions of MSC to the reparative process can occur through autocrine and paracrine effects. The primary objective of this study is to find a novel mean, by transplanting primary cultures of bone marrow-derived MSCs expressing insulin-like growth factor-I (MSC(IGF)), to promote these seed-and-soil actions of MSC to fully implement their regenerative abilities in fracture repair and nonunions. MSC(IGF) or traceable MSC(IGF)-Lac-Z were transplanted into wild-type or insulin-receptor-substrate knockout (Irs1(-/-)) mice with a stabilized tibia fracture. Healing was assessed using biomechanical testing, microcomputed tomography (μCT), and histological analyses. We found that systemically transplanted MSC(IGF) through autocrine and paracrine actions improved the fracture mechanical strength and increased new bone content while accelerating mineralization. We determined that IGF-I adapted the response of transplanted MSC(IGF) to promote their differentiation into osteoblasts. In vitro and in vivo studies showed that IGF-I-induced osteoglastogenesis in MSCs was dependent of an intact IRS1-PI3K signaling. Furthermore, using Irs1(-/-) mice as a nonunion fracture model through altered IGF signaling, we demonstrated that the autocrine effect of IGF-I on MSC restored the fracture new bone formation and promoted the occurrence of a well-organized callus that bridged the gap. A callus that was basically absent in Irs1(-/-) left untransplanted or transplanted with MSCs. We provided evidence of effects and mechanisms for transplanted MSC(IGF) in fracture repair and potentially to treat nonunions.

Proximal femoral fractures in the elderly: how are we measuring outcome?

INTRODUCTION

Patients with proximal femoral fractures present a difficult problem to health care systems in view of their complex presentations and co-morbidities. Traditionally, the focus of outcome measurement for this patient group has been on mortality and surgical implant success. Increasing recognition of the need to diversify outcome measurements has led to the creation and use of a number of outcome scales. We sought to examine how these scales are being used in the current literature.

METHODS

Abstracts to over 4000 papers related to proximal femoral fracture research were screened to identify commonly used scales in the five main categories of general quality of life measures (QoL), Activities of Daily Living scales (ADL), mobility and physical performance scales, disease-specific scales and hip-specific scales. The 14 identified scales were then searched for directly, and papers analysed for scale usage, timing and interpretation.

RESULTS

ADL scales were the most commonly used group, followed by QoL measures, which are validated for elderly patients. Scale timing and use varied widely between studies. A large number of scales were found in addition to the 14 identified scales. None of the 14 identified scales were validated for the proximal femoral fracture population.

DISCUSSION

A good scale must be appropriate in content, method and clinical utility. Its method of application must be reliable, responsive, and validated for the population in question. Outcome scale usage was difficult to assess in proximal femoral fracture research due to difficulties in isolating the relevant research, and in differences in scale timing and interpretation. Scale prevalence was skewed by use by specific research groups.

CONCLUSION

There is no single unifying scale in widespread use for proximal femoral fracture patients. We would recommend the validation of commonly used scales for this population, and would advise the use of scales from more than one category to assess outcome.

Falls, osteoporosis, and hip fractures

Osteoporosis and falls are distinct conditions that share the potential clinical endpoint of fracture. This article explores the associations between osteoporosis and falls by examining the epidemiology, risk factors, risk prevention, and treatments. It outlines the evidence on falls prevention, osteoporosis diagnosis, and fracture risk assessment. It includes several studies that challenge the common view on the use of fall prevention tools, dual energy X-ray absorptiometry testing, and postfracture bisphosphonate treatment. By understanding the evidence, it becomes clearer how to target populations at risk, interpret screening methods, and promote disease prevention and treatment.

Caloric restriction: from soup to nuts

Caloric restriction (CR), reduced protein, methionine, or tryptophan diets; and reduced insulin and/or IGFI intracellular signaling can extend mean and/or maximum lifespan and delay deleterious age-related physiological changes in animals. Mice and flies can shift readily between the control and CR physiological states, even at older ages. Many health benefits are induced by even brief periods of CR in flies, rodents, monkeys, and humans. In humans and nonhuman primates, CR produces most of the physiologic, hematologic, hormonal, and biochemical changes it produces in other animals. In primates, CR provides protection from type 2 diabetes, cardiovascular and cerebral vascular diseases, immunological decline, malignancy, hepatotoxicity, liver fibrosis and failure, sarcopenia, inflammation, and DNA damage. It also enhances muscle mitochondrial biogenesis, affords neuroprotection; and extends mean and maximum lifespan. CR rapidly induces antineoplastic effects in mice. Most claims of lifespan extension in rodents by drugs or nutrients are confounded by CR effects. Transcription factors and co-activators involved in the regulation of mitochondrial biogenesis and energy metabolism, including SirT1, PGC-1alpha, AMPK and TOR may be involved in the lifespan effects of CR. Paradoxically, low body weight in middle aged and elderly humans is associated with increased mortality. Thus, enhancement of human longevity may require pharmaceutical interventions.

The relationship between initial trunk control or postural balance and inpatient rehabilitation outcome after stroke: a prospective comparative study

Objective: To compare the predictive validity of trunk control in sitting position assessed by Trunk Impairment Scale and balance in lying, sitting and standing posture assessed by Postural Assessment Scale for Stroke patients on functional outcome in stroke survivors.

Design: Prospective observational study.

Setting: A single rehabilitation hospital in Italy.

Subjects: Sixty of 68 consecutive subjects admitted to a rehabilitation hospital after stroke.

Main measures: We performed Trunk Impairment Scale and Postural Assessment Scale for Stroke patients at admission to inpatient rehabilitation. Outcome measures at discharge were Functional Independence Measure score and destination (classified as either home or institution).

Results: After adjustment for 14 potential confounders, including Functional Independence Measure score at admission to rehabilitation, both Trunk Impairment Scale and Postural Assessment Scale for Stroke patients scores were significantly associated with the Functional Independence Measure score at discharge (P = 0.010 and P =0.04, respectively), change in the Functional Independence Measure score during rehabilitation (P = 0.003 and P<0.001, respectively), Functional Independence Measure effectiveness (P = 0.024 and P =0.017, respectively) and destination at discharge (P = 0.040 and P =0.032, respectively). The panel of prognostic variables predicted 64—65% of the variance in the final Functional Independence Measure score, 30—35% of the variance in the change of the Functional Independence Measure score during rehabilitation, and 45—46% of the variance in the Functional Independence Measure effectiveness depending on the inclusion of either Trunk Impairment Scale or Postural Assessment Scale for Stroke patients score among the predictors.

Predictors of functional improvement among patients with hip fracture at a rehabilitation ward

To determine possible predictors of FIM scores in patients with hip fracture at discharge a prospective cohort study of 117 patients with either DHS or hip arthroplasty admitted to a rehabilitation service was done. They were classified into four subgroups of underweight (BMI < 18.5), normal (18.5 < BMI < 24.9), overweight (25 < BMI < 29.9) and obese (30 < BMI < 35). Functional evaluations using FIM score as well as sitting, standing, walking days and length of stay for each patient were assessed by a highly skilled therapist at rehabilitation admission; discharge and a post discharge follow up. Recovery was significant in terms of motor subscale. No significant correlation was evident between hospitalization and discharge time with respect to cognitive subscale. The study showed only the age and FIM score at hospitalization to be the independent predictors of total FIM score at discharge. Elevated BMI has not adverse effect on FIM gains in patients with hip fractures. Simple surgery methods such as DHS revealed earlier recovery time than complicated procedures.