Relation between insulin-like growth factor-I concentrations, osteoarthritis, bone density, and fractures in the general population: the Chingford study

The association between IGF-1 levels and four types of osteoarthritis: a bidirectional and two-step mendelian randomization study

Background

Insulin-like Growth Factor-1 (IGF-1) plays a crucial role in the growth and metabolic functions of various tissues and cells in the body. Recently, there has been increased attention to the association between IGF-1 and osteoarthritis (OA). However, there is controversy in current research regarding the correlation between IGF-1 levels and OA. Furthermore, the specific manner in which Body Mass Index (BMI), a key risk factor for OA, mediates the impact of IGF-1 levels on OA remains unclear.

Object

This study aimed to investigate the bidirectional causal link between IGF-1 levels and OA in four body regions, and to explore how BMI influences the impact of IGF-1 on these types of OA.

Method

Two-sample Mendelian Randomization (MR) and its combined forms were utilized to investigate the bidirectional relationship between IGF-1 levels and four types of OA, as well as the mediating role of BMI in the impact of IGF-1 levels on OA. Data from various Genome-Wide Association Studies (GWAS) and multiple analytical methods, including inverse variance weighted, MR-Egger regression, and weighted median were utilized. Sensitivity analyses, such as MR-Egger intercept, Cochran Q test, leave-one-out, and MR-PRESSO, were conducted to ensure the robustness of the results.

Results

Higher IGF-1 levels are correlated with an increased risk for knee (OR, 1.07; 95% CI, 1.01-1.03; p = 1.49e-01; q = 9.86e-03), hip (OR, 1.13; 95% CI, 1.06-1.20; p = 7.61e-05; q = 7.44e-05), and hand OA (OR, 1.09; 95% CI, 1.01-1.17; p = 1.88e-02; q = 1.15e-02), but not spine OA but not spine OA (OR, 1.05; 95% CI, 0.99-1.10; p = 9.20e-02; q = 5.52e-02). Different types of OA do not affect IGF-1 levels. BMI mediates the increase in OA risk associated with higher IGF-1, including indirect spine OA risk through BMI.

Conclusion

The study elucidates the bidirectional causality between IGF-1 levels and OA in various body parts, highlighting BMI's mediating role in the impact of IGF-1 levels on OA. This provides valuable insights for OA prevention, diagnosis, and treatment strategies. Future research will expand our study to include a broader spectrum of ethnicities and explore the underlying mechanisms involved.

Controversial causal association between IGF family members and osteoporosis: a Mendelian randomization study between UK and FinnGen biobanks

Objectives

Osteoporosis, a prevalent skeletal disorder characterized by reduced bone strength, is closely linked to the IGF system, crucial for skeletal metabolism. However, the precise nature of this relationship remains elusive. In this study, we employed Mendelian randomization (MR) to unravel the associations between genetically predicted serum IGF system member levels and osteoporosis.

Methods

A two-sample MR approach was employed to investigate these causal associations based on two individual datasets. Predictions of 14 serum levels of IGF system members were made using 11,036,163 relevant Single Nucleotide Polymorphisms (SNPs) within a cohort of 4,301 individuals of European descent. Genetic association estimates for osteoporosis were derived from two publicly available GWAS consortia: the Finnish consortium from the FinnGen biobank, comprising 212,778 individuals of Finnish descent (3,203 cases and 209,575 controls), and the UK consortium from the UK Biobank, including 337,159 individuals of European descent (5,266 cases and 331,893 controls).

Results

According to the UK dataset, IGF-1 levels were associated with a reduced risk of osteoporosis, as indicated by the weighted median method (Odds Ratio [OR] = 0.998, 95% CI = 0.997-1.000, P = 0.032). Additionally, higher levels of IGFBP-3 were linked to a decreased risk of osteoporosis using the Inverse-Variance Weighted (IVW) method (OR = 0.999, 95% CI = 0.998-1.000, P = 0.019), and CTGF levels exhibited a negative association with osteoporosis, as determined by the weighted median method (OR = 0.998, 95% CI = 0.996-0.999, P = 0.004). In the FinnGen dataset, IGF-1 and IGFBP-3 were not identified to be associated with osteoporosis. While, IGF-LR1 levels displayed a negative association with osteoporosis, according to the MR-Egger method (OR = 0.886, 95% CI = 0.795-0.987, P = 0.036), while CYR61 was linked to an increased risk of osteoporosis based on both the weighted median and IVW methods (OR = 1.154, 95% CI = 1.009-1.319, P = 0.037, and OR = 1.115, 95% CI = 1.022-1.215, P = 0.014, respectively).

Conclusion

This study provides compelling evidence that certain IGF family members play a role in the pathogenesis of osteoporosis between different datasets, indicating population specific causal effects between IGF family and osteoporosis. Although the results from both datasets demonstrated that IGF family involved in the pathogenesis of osteoporosis, but the responding key molecules might be various among different population. Subsequent research is warranted to evaluate the potential of these biomarkers as targets for osteoporosis prevention and treatment in specific population.

Effects and action mechanisms of individual cytokines contained in PRP on osteoarthritis

Osteoarthritis (OA) is defined as a degenerative joint disease that can affect all tissues of the joint, including the articular cartilage, subchondral bone, ligaments capsule, and synovial membrane. The conventional nonoperative treatments are ineffective for cartilage repair and induce only symptomatic relief. Platelet-rich plasma (PRP) is a platelet concentrate derived from autologous whole blood with a high concentration of platelets, which can exert anti-inflammatory and regenerative effects by releasing multiple growth factors and cytokines. Recent studies have shown that PRP exhibits clinical benefits in patients with OA. However, high operational and equipment requirements greatly limit the application of PRP to OA treatment. Past studies have indicated that high-concentration PRP growth factors and cytokines may be applied as a commercial replacement for PRP. We reviewed the relevant articles to summarize the feasibility and mechanisms of PRP-based growth factors in OA. The available evidence suggests that transforming growth factor-α and β, platelet-derived growth factors, epidermal growth factor, insulin-like growth factor-1, and connective tissue growth factors might benefit OA, while vascular endothelial growth factor, tumor necrosis factor-α, angiopoietin-1, and stromal cell derived factor-1α might induce negative effects on OA. The effects of fibroblast growth factor, hepatocyte growth factor, platelet factor 4, and keratinocyte growth factor on OA remain uncertain. Thus, it can be concluded that not all cytokines released by PRP are beneficial, although the therapeutic action of PRP has a valuable potential to improve.

Association of Endogenous Hormones and Bone Mineral Density in Postmenopausal Women

Aim

The aim of this study was to examine the association between endogenous hormones and bone mineral density (BMD) in postmenopausal women.

Materials and Methods

This was a cross-sectional study of 798 postmenopausal women aged 47-85 years. Data were collected on age, age at menopause, years since menopause, smoking status, body mass index, adiposity, BMD, physical activity, and Vitamin D supplementation. Measured hormonal parameters were: follicle-stimulating hormone (FSH), estradiol, testosterone, dehydroepiandrosterone sulfate, ∆4-androstenedione, cortisol, insulin-like growth factor-1, 25-hydroxyvitamin D, and parathormone (PTH) levels. BMD was measured at the lumbar spine, femoral neck, and total hip using dual-energy X-ray absorptiometry. A directed acyclic graph was used to select potential confounding variables.

Results

Multivariable analysis showed significant associations between cortisol and femoral neck BMD (β: -0.02, 95% confidence interval [CI]: -0.03--0.00), and PTH with femoral neck BMD (β: -0.01, 95% CI: -0.02--0.01) and total hip BMD (β: -0.01, 95% CI: -0.01--0.00). Hormonal factors more likely associated with a higher risk of low BMD (osteopenia or osteoporosis) were FSH (odds ratio [OR]: 1.02, 95% CI: 1.01-1.03) and PTH (OR: 1.02, 95% CI: 1.01-1.04).

Conclusions

Higher cortisol and PTH levels were inversely associated with BMD. Postmenopausal women with higher FSH or PTH levels were likely to have low BMD.

Shared genetic susceptibility between trigger finger and carpal tunnel syndrome: a genome-wide association study

Background

Trigger finger and carpal tunnel syndrome are the two most common non-traumatic connective tissue disorders of the hand. Both of these conditions frequently co-occur, often in patients with rheumatoid arthritis. However, this phenotypic association is poorly understood. Hypothesising that the co-occurrence of trigger finger and carpal tunnel syndrome might be explained by shared germline predisposition, we aimed to identify a specific genetic locus associated with both diseases.

Methods

In this genome-wide association study (GWAS), we identified 2908 patients with trigger finger and 436579 controls from the UK Biobank prospective cohort. We conducted a case-control GWAS for trigger finger, followed by co-localisation analyses with carpal tunnel syndrome summary statistics. To identify putative causal variants and establish their biological relevance, we did fine-mapping analyses and expression quantitative trait loci (eQTL) analyses, using fibroblasts from healthy donors (n=79) and tenosynovium samples from patients with carpal tunnel syndrome (n=77). We conducted a Cox regression for time to trigger finger and carpal tunnel syndrome diagnosis against plasma IGF-1 concentrations in the UK Biobank cohort.

Findings

Phenome-wide analyses confirmed a marked association between carpal tunnel syndrome and trigger finger in the participants from UK Biobank (odds ratio [OR] 11·97, 95% CI 11·1-13·0; p<1 × 10^-300). GWAS for trigger finger identified five independent loci, including one locus, DIRC3, that was co-localised with carpal tunnel syndrome and could be fine-mapped to rs62175241 (0·76, 0·68-0·84; p=5·03 × 10^-13). eQTL analyses found a fibroblast-specific association between the protective T allele of rs62175241 and increased DIRC3 and IGFBP5 expression. Increased plasma IGF-1 concentrations were associated with both carpal tunnel syndrome and trigger finger in participants from UK Biobank (hazard ratio >1·04, p<0·02).

Interpretation

In this GWAS, the DIRC3 locus on chromosome 2 was significantly associated with both carpal tunnel syndrome and trigger finger, possibly explaining their co-occurrence. The disease-protective allele of rs62175241 was associated with increased expression of long non-coding RNA DIRC3 and its transcriptional target, IGBP5, an antagonist of IGF-1 signalling. These findings suggest a model in which IGF-1 is a driver of both carpal tunnel syndrome and trigger finger, and in which the DIRC3-IGFBP5 axis directly antagonises fibroblastic IGF-1 signalling.

Funding

Wellcome Trust, National Institute for Health Research, Medical Research Council.

Induction of somatopause in adult mice compromises bone morphology and exacerbates bone loss during aging

Somatopause refers to the gradual declines in growth hormone (GH) and insulin‐like growth factor‐1 throughout aging. To define how induced somatopause affects skeletal integrity, we used an inducible GH receptor knockout (iGHRKO) mouse model. Somatopause, induced globally at 6 months of age, resulted in significantly more slender bones in both male and female iGHRKO mice. In males, induced somatopause was associated with progressive expansion of the marrow cavity leading to significant thinning of the cortices, which compromised bone strength. We report progressive declines in osteocyte lacunar number, and increases in lacunar volume, in iGHRKO males, and reductions in lacunar number accompanied by ~20% loss of overall canalicular connectivity in iGHRKO females by 30 months of age. Induced somatopause did not affect mineral/matrix ratio assessed by Raman microspectroscopy. We found significant increases in bone marrow adiposity and high levels of sclerostin, a negative regulator of bone formation in iGHRKO mice. Surprisingly, however, despite compromised bone morphology, osteocyte senescence was reduced in the iGHRKO mice. In this study, we avoided the confounded effects of constitutive deficiency in the GH/IGF‐1 axis on the skeleton during growth, and specifically dissected its effects on the aging skeleton. We show here, for the first time, that induced somatopause compromises bone morphology and the bone marrow environment.

Mendelian randomization provides evidence for a causal effect of higher serum IGF-1 concentration on risk of hip and knee osteoarthritis

Objectives

How insulin-like growth factor-1 (IGF-1) is related to OA is not well understood. We determined relationships between IGF-1 and hospital-diagnosed hand, hip and knee OA in UK Biobank, using Mendelian randomization (MR) to determine causality.

Methods

Serum IGF-1 was assessed by chemiluminescent immunoassay. OA was determined using Hospital Episode Statistics. One-sample MR (1SMR) was performed using two-stage least-squares regression, with an unweighted IGF-1 genetic risk score as an instrument. Multivariable MR included BMI as an additional exposure (instrumented by BMI genetic risk score). MR analyses were adjusted for sex, genotyping chip and principal components. We then performed two-sample MR (2SMR) using summary statistics from Cohorts for Heart and Aging Research in Genetic Epidemiology (CHARGE) (IGF-1, N = 30 884) and the recent genome-wide association study meta-analysis (N = 455 221) of UK Biobank and Arthritis Research UK OA Genetics (arcOGEN).

Results

A total of 332 092 adults in UK Biobank had complete data. Their mean (s.d.) age was 56.5 (8.0) years and 54% were female. IGF-1 was observationally related to a reduced odds of hand OA [odds ratio per doubling = 0.87 (95% CI 0.82, 0.93)], and an increased odds of hip OA [1.04 (1.01, 1.07)], but was unrelated to knee OA [0.99 (0.96, 1.01)]. Using 1SMR, we found strong evidence for an increased risk of hip [odds ratio per s.d. increase = 1.57 (1.21, 2.01)] and knee [1.30 (1.07, 1.58)] OA with increasing IGF-1 concentration. By contrast, we found no evidence for a causal effect of IGF-1 concentration on hand OA [0.98 (0.57, 1.70)]. Results were consistent when estimated using 2SMR and in multivariable MR analyses accounting for BMI.

Conclusion

We have found evidence that increased serum IGF-1 is causally related to higher risk of hip and knee OA.

Insulin-like Growth Factor-1, Bone Mineral Density, and Fracture: A Mendelian Randomization Study

CONTEXT

The associations of circulating insulin-like growth factor-1 (IGF-1) levels with bone mineral density and fracture risk are inconclusive in observational studies.

OBJECTIVE

We conducted a mendelian randomization study to assess the associations of serum IGF-1 levels with estimated bone mineral density (eBMD) and fracture.

METHODS

Genetic instruments for IGF-1 were selected at the genome-wide significance level (P < 5 × 10-8) from a genome-wide association study including 358 072 individuals of European ancestry. Summary-level data for eBMD (426 824 individuals) and fracture (53 184 fracture cases and 373 611 noncases) were obtained from the UK Biobank study. Univariable and multivariable mendelian randomization analyses methods were used to estimate the associations of IGF-1 with eBMD and fracture. The main outcome measure included the change of eBMD and odds ratio of fracture per genetically predicted 1-SD increase of serum IGF-1 levels.

RESULTS

For 1-SD increase in IGF-1, the change of eBMD levels was 0.04 g/cm2 (95% CI, 0.01-0.07; P = .011) and the odds ratio of fracture was 0.94 (95% CI, 0.91-0.98; P = .003). The associations persisted with similar magnitude after adjustment for height. The association was consistent for fracture but not for eBMD after excluding genetic instruments that might directly influence these outcomes. The association between IGF-1 and fracture was somewhat attenuated after adjustment for eBMD (odds ratio 0.96; 95% CI, 0.92-0.99; P = .012).

CONCLUSION

The present study supports a role for IGF-1 in preventing fracture, possibly and partly mediated by greater bone mineral density.

Energy Metabolism and Ketogenic Diets: What about the Skeletal Health? A Narrative Review and a Prospective Vision for Planning Clinical Trials on this Issue

The existence of a common mesenchymal cell progenitor shared by bone, skeletal muscle, and adipocytes cell progenitors, makes the role of the skeleton in energy metabolism no longer surprising. Thus, bone fragility could also be seen as a consequence of a “poor” quality in nutrition. Ketogenic diet was originally proven to be effective in epilepsy, and long-term follow-up studies on epileptic children undergoing a ketogenic diet reported an increased incidence of bone fractures and decreased bone mineral density. However, the causes of such negative impacts on bone health have to be better defined. In these subjects, the concomitant use of antiepileptic drugs and the reduced mobilization may partly explain the negative effects on bone health, but little is known about the effects of diet itself, and/or generic alterations in vitamin D and/or impaired growth factor production. Despite these remarks, clinical studies were adequately designed to investigate bone health are scarce and bone health related aspects are not included among the various metabolic pathologies positively influenced by ketogenic diets. Here, we provide not only a narrative review on this issue, but also practical advice to design and implement clinical studies on ketogenic nutritional regimens and bone health outcomes. Perspectives on ketogenic regimens, microbiota, microRNAs, and bone health are also included.

Effects of GH/IGF axis on bone and cartilage

Growth hormone (GH) and its mediator, the insulin-like growth factor-1 (IGF-1) regulate somatic growth, metabolism and many aspects of aging. As such, actions of GH/IGF have been studied in many tissues and organs over decades. GH and IGF-1 are part of the hypothalamic/pituitary somatotrophic axis that consists of many other regulatory hormones, receptors, binding proteins, and proteases. In humans, GH/IGF actions peak during pubertal growth and regulate skeletal acquisition through stimulation of extracellular matrix production and increases in bone mineral density. During aging the activity of these hormones declines, a state called somatopaguss, which associates with deleterious effects on the musculoskeletal system. In this review, we will focus on GH/IGF-1 action in bone and cartilage. We will cover many studies that have utilized congenital ablation or overexpression of members of this axis, as well as cell-specific gene-targeting approaches used to unravel the nature of the GH/IGF-1 actions in the skeleton in vivo.

Osteosarcopenia in Reproductive-Aged Women with Polycystic Ovary Syndrome: A Multicenter Case-Control Study

CONTEXT

Osteosarcopenia (loss of skeletal muscle and bone mass and/or function usually associated with aging) shares pathophysiological mechanisms with polycystic ovary syndrome (PCOS). However, the relationship between osteosarcopenia and PCOS remains unclear.

OBJECTIVE

We evaluated skeletal muscle index% (SMI% = [appendicular muscle mass/weight (kg)] × 100) and bone mineral density (BMD) in PCOS (hyperandrogenism + oligoamenorrhea), and contrasted these musculoskeletal markers against 3 reproductive phenotypes (i): HA (hyperandrogenism + eumenorrhea) (ii); OA (normoandrogenic + oligoamenorrhea) and (iii), controls (normoandrogenic + eumenorrhea). Endocrine predictors of SMI% and BMD were evaluated across the groups.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter case-control study of 203 women (18-48 years old) in New York State.

RESULTS

PCOS group exhibited reduced SMI% (mean [95% confidence interval (CI)]; 26.2% [25.1,27.3] vs 28.8% [27.7,29.8]), lower-extremity SMI% (57.6% [56.7,60.0] vs 62.5% [60.3,64.6]), and BMD (1.11 [1.08,1.14] vs 1.17 [1.14,1.20] g/cm2) compared to controls. PCOS group also had decreased upper (0.72 [0.70,0.74] vs 0.77 [0.75,0.79] g/cm2) and lower (1.13 [1.10,1.16] vs 1.19 [1.16,1.22] g/cm2) limb BMD compared to HA. Matsuda index was lower in PCOS vs controls and positively associated with SMI% in all groups (all Ps ≤ 0.05). Only controls showed associations between insulin-like growth factor (IGF) 1 and upper (r = 0.84) and lower (r = 0.72) limb BMD (all Ps < 0.01). Unlike in PCOS, IGF-binding protein 2 was associated with SMI% in controls (r = 0.45) and HA (r = 0.67), and with upper limb BMD (r = 0.98) in HA (all Ps < 0.05).

CONCLUSIONS

Women with PCOS exhibit early signs of osteosarcopenia when compared to controls likely attributed to disrupted insulin function. Understanding the degree of musculoskeletal deterioration in PCOS is critical for implementing targeted interventions that prevent and delay osteosarcopenia in this clinical population.

Insulin-like growth factors: actions on the skeleton

The discovery of the growth hormone (GH)-mediated somatic factors (somatomedins), insulin-like growth factor (IGF)-I and -II, has elicited an enormous interest primarily among endocrinologists who study growth and metabolism. The advancement of molecular endocrinology over the past four decades enables investigators to re-examine and refine the established somatomedin hypothesis. Specifically, gene deletions, transgene overexpression or more recently, cell-specific gene-ablations, have enabled investigators to study the effects of the Igf1 and Igf2 genes in temporal and spatial manners. The GH/IGF axis, acting in an endocrine and autocrine/paracrine fashion, is the major axis controlling skeletal growth. Studies in rodents have clearly shown that IGFs regulate bone length of the appendicular skeleton evidenced by changes in chondrocytes of the proliferative and hypertrophic zones of the growth plate. IGFs affect radial bone growth and regulate cortical and trabecular bone properties via their effects on osteoblast, osteocyte and osteoclast function. Interactions of the IGFs with sex steroid hormones and the parathyroid hormone demonstrate the significance and complexity of the IGF axis in the skeleton. Finally, IGFs have been implicated in skeletal aging. Decreases in serum IGFs during aging have been correlated with reductions in bone mineral density and increased fracture risk. This review highlights many of the most relevant studies in the IGF research landscape, focusing in particular on IGFs effects on the skeleton.

Racial Differences in Serum Adipokine and Insulin Levels in a Matched Osteoarthritis Sample: A Pilot Study

BACKGROUND

In an attempt to correlate biomarkers with disease, serum-based biomarkers often are compared between individuals with osteoarthritis (OA) and control subjects. However, variable results have been reported. Some studies have suggested an association between certain adipokines and insulin and OA. We know that there are racial differences in OA prevalence and incidence, and from general population-based studies, those of Asian race consistently demonstrate a unique adipokine/insulin serum concentration profile as compared to Caucasians. Whether similar racial differences exist within OA samples is unknown and may have implications for selecting appropriate controls in comparative studies.

METHODS

Serum levels of adipokines, leptin, and adiponectin, along with insulin, were determined by ELISA in patients scheduled for total hip or knee replacement surgery for OA. Fifteen Asian patients were matched 1 : 1 on age (±2 years), gender, body mass index (±1.5 kg/m(2)), and surgical joint with Caucasian patients. Differences in serum concentrations were tested using paired t-tests.

RESULTS

Serum leptin and insulin levels were significantly higher in Asians compared to Caucasians (p < 0.05). While serum adiponectin levels were lower among Asians, the difference did not reach statistical significance (p = 0.12).

CONCLUSION

Findings from this work suggest that when studying serum biomarker concentrations in OA versus controls, race may be an important factor to consider. Our findings warrant confirmation in larger studies.

Relationship of insulin-like growth factor 1 and bone parameters in 7-15 years old apparently, healthy Indian children

OBJECTIVE

Growth hormone through insulin-like growth factor 1 (IGF-1) plays an important role in both bone growth and mineralization. This cross-sectional study was carried out to evaluate the relationship between serum IGF-1 concentrations and dual energy X-ray (DXA) measured whole body less head bone area (BA), lean body mass (LBM), and bone mineral content (BMC).

METHODS

One hundred and nineteen children (boys = 70, age = 7.3-15.6 years) were studied for their anthropometric parameters by standard methods and bone and body composition by DXA. Their fasting serum IGF-1 concentrations were assessed by enzyme-linked immunosorbent assay and Z-scores were calculated using available reference data. Bone and body composition parameter Z-scores were calculated using ethnic reference data.

RESULTS

Mean age of the boys and girls was similar (11.5 ± 1.8 years). The mean serum IGF-1concentrations and IGF-1 Z-scores were similar (P > 0.1) between boys and girls and were of the order of (302.3 ± 140.0 and - 1.4 ± 1.1, respectively). The LBM for age and BA for age Z-score was greater in children with IGF-1 Z-score > median than children with IGF-1 Z-score < median. The mean BMC for age Z-scores were 0.4 ± 0.9 and - 0.2 ± 0.8 in children with above and below the median of IGF-1 Z-score (P > 0.1).

CONCLUSION

Serum IGF-1 levels were more strongly associated with BA and LBM, suggesting that its effect on bone is greater with respect to periosteal bone acquisition and through its effect on muscle mass.

The relationship between osteoarthritis and osteoporosis

The relationship between osteoarthritis (OA) and osteoporosis (OP), the two most common skeletal disorders related to aging, is controversial. Previous studies suggest that OA is inversely related to OP when studied cross-sectionally and systematically. However, there are differences in the results depending on the parameter used to define OA. The purpose of this review is to analyze and summarize the literature, and derive possible answers to three key questions along with a brief introduction on underlying mechanisms: (1) Is OA correlated to a high bone mineral density (BMD)? (2) Does OA influence the progression of OP or osteoporotic fractures? (3) Does high BMD affect the incidence and progression of OA? A review of the literature suggests that OA is inversely related to OP in general when studied cross-sectionally and systematically. However, when analyzed in individual bones, the BMD of the appendicular skeleton in OA-affected joints may decrease, particularly in the upper extremities. On whether OA influences bone loss or osteoporotic fractures, differences are observed according to the affected joints. The risk for osteoporotic fracture does not seem to decrease despite a high BMD in patients with OA, probably due to postural instability and muscle strength. Low BMD at the lumbar spine is associated with a lower incidence of knee OA although it does not arrest the progression of knee OA.

Hormone replacement therapy and physical function in healthy older men. Time to talk hormones?

Improving physical function and mobility in a continuously expanding elderly population emerges as a high priority of medicine today. Muscle mass, strength/power, and maximal exercise capacity are major determinants of physical function, and all decline with aging. This contributes to the incidence of frailty and disability observed in older men. Furthermore, it facilitates the accumulation of body fat and development of insulin resistance. Muscle adaptation to exercise is strongly influenced by anabolic endocrine hormones and local load-sensitive autocrine/paracrine growth factors. GH, IGF-I, and testosterone (T) are directly involved in muscle adaptation to exercise because they promote muscle protein synthesis, whereas T and locally expressed IGF-I have been reported to activate muscle stem cells. Although exercise programs improve physical function, in the long-term most older men fail to comply. The GH/IGF-I axis and T levels decline markedly with aging, whereas accumulating evidence supports their indispensable role in maintaining physical function integrity. Several studies have reported that the administration of T improves lean body mass and maximal voluntary strength in healthy older men. On the other hand, most studies have shown that administration of GH alone failed to improve muscle strength despite amelioration of the detrimental somatic changes of aging. Both GH and T are anabolic agents that promote muscle protein synthesis and hypertrophy but work through separate mechanisms, and the combined administration of GH and T, albeit in only a few studies, has resulted in greater efficacy than either hormone alone. Although it is clear that this combined approach is effective, this review concludes that further studies are needed to assess the long-term efficacy and safety of combined hormone replacement therapy in older men before the medical rationale of prescribing hormone replacement therapy for combating the sarcopenia of aging can be established.

Obesity and symptomatic osteoarthritis of the knee

Given the growing prevalence of obesity around the world and its association with osteoarthritis of the knee, orthopaedic surgeons need to be familiar with the management of the obese patient with degenerative knee pain. The precise mechanism by which obesity leads to osteoarthritis remains unknown, but is likely to be due to a combination of mechanical, humoral and genetic factors. Weight loss has clear medical benefits for the obese patient and seems to be a logical way of relieving joint pain associated with degenerative arthritis. There are a variety of ways in which this may be done including diet and exercise, and treatment with drugs and bariatric surgery. Whether substantial weight loss can delay or even reverse the symptoms associated with osteoarthritis remains to be seen. Surgery for osteoarthritis in the obese patient can be technically more challenging and carries a risk of additional complications. Substantial weight loss before undertaking total knee replacement is advisable. More prospective studies that evaluate the effect of significant weight loss on the evolution of symptomatic osteoarthritis of the knee are needed so that orthopaedic surgeons can treat this patient group appropriately.

Relationship between insulin-like growth factor-1 and radiographic disease in patients with primary osteoarthritis: a systematic review

OBJECTIVE

To evaluate the association between radiographic osteoarthritis (OA) and either serum insulin-like growth factor-1 (IGF-1) levels or IGF-1 gene polymorphisms in patients with primary OA.

METHODS

We conducted a systematic review of reported associations between circulating IGF-1 and/or IGF-1 gene polymorphisms and radiographic OA. Studies were eligible when: (1) investigating serum IGF-1 and/or IGF-1 gene polymorphisms in relation to prevalent or incident radiographic OA; (2) written in English; (3) full-text article or abstract; (4) patients had primary OA in knee, hip, hand or spine; (5) longitudinal, case-control or cross-sectional design. Quality assessment was done using a standardized criteria set. Best-evidence synthesis was performed based on guidelines on systematic review from the Cochrane Collaboration Back Review Group, using five evidence levels: strong, moderate, limited, conflicting and no evidence.

RESULTS

We included 11 studies with more than 3000 primary OA cases. Data on the relationship between serum IGF-1 and radiographic OA were inconsistent. Adjustment for body mass index (BMI) was often omitted. Of four high-quality studies, three studies reported no association, one study found significantly higher IGF-1 levels in OA patients compared to controls. Patients with IGF-1 gene promoter polymorphisms and a genetic variation at the IGF-1R locus had an increased OA prevalence compared to controls.

CONCLUSIONS

Observational data showed no association between serum IGF-1 and occurrence of radiographic OA (moderate level of evidence), and a positive relationship between IGF-1 gene polymorphisms and radiographic OA (moderate level of evidence); however the confounding effect of BMI was insufficiently addressed. Future well-designed prospective studies should further elaborate the role of the complex GH/IGF-1 system in primary OA.

Effect of low-intensity aerobic exercise on insulin-like growth factor-I and insulin-like growth factor-binding proteins in healthy men

Increased concentrations of circulating insulin-like growth factor-I (IGF-I) or IGF-I relative to IGF-binding proteins (IGFBPs) are associated with increased risk of developing several forms of cancer. Conversely, exercise is linked with reduced risk. This study aims to investigate the effect of a low-intensity exercise program on circulating levels of IGF-I, IGFBP-1, and IGFBP-3, in previously sedentary males. Fourteen healthy men participated in cycle ergometer training at lactate threshold intensity for 60 min/day, 5 days/week for 6 weeks. After aerobic training, insulin sensitivity improved by 20%, while fasting insulin levels decreased by 13%. Simultaneously, low-intensity aerobic training decreased the circulating levels of IGF-I by 9%, while IGFBP-1 levels increased by 16%. An interesting finding was that higher pretraining level of IGF-I was associated with greater decline in IGF-I with training. Insulin-sensitizing low-intensity aerobic exercise is thus considered to be an effective method for downregulating IGF-I and upregulating IGFBP-1 levels.

Relationship among insulinlike growth factor I concentrations, bone mineral density, and biochemical markers of bone turnover in postmenopausal women: a population-based study

OBJECTIVE

: To assess the association among serum insulinlike growth factor I (IGF-I) concentrations, bone mineral density (BMD), and biochemical markers of bone turnover in a large group of postmenopausal women from the general population.

DESIGN

: As an extension of a larger epidemiological study, the Iranian Multicentral Osteoporosis Study, a total of 406 healthy postmenopausal women (age, 59.0 +/- 7.6 years) were randomly selected from 13 clusters in Bushehr Port. IGF-I, serum CrossLaps, degradation products of C-terminal telopeptides of type I collagen, and osteocalcin were measured by highly specific enzyme-linked immunosorbent assay. BMD was determined for the lumbar spine (L2-4) and proximal femur using dual-energy x-ray absorptiometry.

RESULTS

: The mean (+/- SD) serum IGF-I concentration for all postmenopausal women was 183.35 +/- 65.60 ng/mL. In age-adjusted analyses, there was no correlation between IGF-I and BMD at the lumbar spine and femoral neck. Compared with women in the lowest quartile of IGF-I, women in the highest quartile had a significantly greater means of osteocalcin (P = 0.04) and alkaline phosphatase (P = 0.01). Analysis by quartiles of IGF-I did not reveal an association with serum CrossLaps.

CONCLUSIONS

: Circulating IGF-I is associated with biochemical markers of bone formation, but there is no relationship among IGF-I, degradation products of C-terminal telopeptides of type I collagen, and BMD in postmenopausal women. Clearly more work will be needed before serum IGF-I can be used in clinical practice as a risk predictor for postmenopause-associated loss of bone mass.

The insulin-like growth factor-I gene and osteoporosis: a critical appraisal

Osteoporosis, a disorder of skeletal fragility, is common in the elderly, and its prevalence is increasing as more individuals with low bone mineral density (BMD), the strongest predictor of fracture risk, are detected. Previous basic and clinical studies imply there is a significant role for insulin-like growth factor-I (IGF-I) in determining BMD. Recently, polymorphisms upstream of the P1 promoter region of the human IGF-I gene have been found to be associated with serum levels of IGF-I, BMD and fracture risk in various ethnic groups. Multiple quantitative trait loci (QTLs) have been identified that underlie serum IGF-I in a mouse intercross between two inbred strains. The most promising QTL on mouse chromosome 6 has provided clues for unraveling the molecular mechanisms that regulate osteoblast differentiation. Genomic engineering resulting in IGF-I deficient mice, and mice with targeted over-expression of IGF-I reinforce the essential role of IGF-I in bone development at both the embryonic and postnatal stages. Thus, it is apparent that significant new insights into the role of the IGF-I gene in bone remodeling occur through several distinct mechanisms: (1) the skeletal IGF regulatory system; (2) the systemic growth hormone/IGF-I axis; (3) parathyroid hormone signaling; (4) sex steroids; and (5) the OPG/RANKL/RANK cytokine system. Molecular dissection of the IGF regulatory system and its signaling pathway in bone may reveal novel therapeutic targets for the treatment of osteoporosis.

Role of the Growth Hormone/Insulin-like Growth Factor-1 Paracrine Axis in Rheumatic Diseases

OBJECTIVES

Hypothalamic-pituitary axis abnormalities have been associated with systemic disturbances in several rheumatic diseases. Longitudinal analysis of erythrocyte, serum, urinary and synovial fluid growth hormone (GH), insulin-like growth factor-1 (IGF-1), and somatostatin levels could provide important surrogate measures of disease activity in rheumatic diseases.

METHODS

The authors reviewed the population and longitudinal studies literature on GH, IGF-1, and somatostatin levels in rheumatic disorders using the PubMed and Medlines databases from the National Library of Medicine. In addition to the literature search, primary data were analyzed for basal somatostatin levels in patients with hand, knee, and spine osteoarthritis (OA) as well as primary and secondary hip OA.

RESULTS

A review of the literature supports the view that hypothalamic-pituitary axis dysfunction accompanies clinical symptoms in many rheumatic diseases. In studies from our laboratory, serum GH levels were elevated in patients with OA, rheumatoid arthritis (RA), fibromyalgia, and diffuse idiopathic skeletal hyperostosis but not in patients with gout, pseudogout, or systemic lupus erythematosus. In OA and RA, synovial fluid GH levels exceeded serum GH levels. However, the literature remains controversial regarding the significance of changes in IGF-1 levels in rheumatic disorders. Many studies support an inverse relationship between age and IGF-1. Elevated serum GH levels in various rheumatic diseases were not coupled to changes in serum IGF-1 in diffuse idiopathic skeletal hyperostosis, RA, and fibromyalgia. In particular, serum IGF-1 levels in OA were shown to be lower or no different compared with age-matched normal subjects. Further, in OA, impaired articular chondrocyte response to IGF-1 was attributed, in part, to low synovial fluid IGF-1 that further compromised IGF-1 chondrocyte responses as a result of increased levels of synovial fluid IGF-1 binding proteins. Of note, serum somatostatin levels and "specific" somatostatin receptor levels were often lower in RA and systemic lupus erythematosus, but basal serum somatostatin levels were generally not altered in OA.

CONCLUSIONS

The results of these analyses support the view that some rheumatic diseases such as OA and diffuse idiopathic skeletal hyperostosis, heretofore considered to be purely focal and degenerative, could be reclassified as systemic metabolic disturbances. We propose that serum GH, IGF-1, and somatostatin levels be monitored on a longitudinal basis during the course of medical therapy of rheumatic diseases to determine the extent to which changes in clinical symptoms (exemplified by reduced pain and inflammation and improved range of joint motion) are accompanied by changes in the basal concentration of these hypothalamic/pituitary-related hormones.

Associations between Plasma Insulin-Like Growth Factor Proteins and C-Peptide and Quality of Life in Patients with Metastatic Colorectal Cancer

OBJECTIVE

Predictors of quality of life (QOL) in patients with metastatic colorectal cancer are lacking. The insulin-like growth factor (IGF) family of proteins is associated with QOL in noncancer populations. We sought to study whether these proteins are associated with QOL in patients with colorectal cancer.

METHOD

We used a cohort of 526 patients with metastatic colorectal cancer treated with combination chemotherapy. Plasma samples of IGF-I, IGF-II, IGF binding protein-3, and C-peptide were collected before initiation of chemotherapy. QOL was measured by the uniscale instrument and the Symptom Distress Scale at baseline and throughout treatment.

RESULTS

Baseline plasma levels of IGF-I and IGF-II before initiation of chemotherapy were significantly associated with several important baseline QOL measures in patients with metastatic colorectal cancer. Patients with lower levels of IGF-I reported increased distress with regard to appearance, appetite, cough, and nausea intensity after adjustment for potential confounders. Similarly, decreased levels of IGF-II were predictive of worse quality related to appearance, appetite, fatigue, nausea frequency and intensity, pain frequency, and composite Symptom Distress Scale score. IGF binding protein-3 and C-peptide were not predictive of baseline QOL. Baseline biomarkers were not associated with subsequent changes in QOL during treatment. Higher body mass index was significantly associated with superior baseline QOL in several areas; nonetheless, the association of IGF-I and IGF-II with baseline QOL measures remained significant even after controlling for baseline body mass index.

CONCLUSION

Baseline plasma IGF-I and IGF-II are significantly associated with symptom distress. Whether this association is simply reflective of patient nutritional status and/or disease burden or represents an independent biological effect of IGFs on QOL remains uncertain. Nonetheless, these data suggest that molecular biomarkers may be useful predictors of QOL in cancer patients.

Statins and Osteoporosis: A Clinical Review

Osteoporosis is a leading public health threat affecting approximately 44 million people in the United States. Most of the therapies for this disease work to prevent further bone loss, improve bone mineral density, and reduce the risk of fractures. These agents, however, have not been proved to increase bone formation significantly. Therefore, the ideal agent would not only improve bone strength by decreasing bone breakdown, but also promote bone formation in the ultimate quest to prevent fractures. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have become an area of research in the battle against osteoporosis. Two mechanisms for beneficial effects of statins on bones have been proposed, and although in vitro, in vivo, and animal studies have shown positive effects on bone mineralization and reductions in bone resorption, clinical data on surrogate markers and fracture rates are conflicting. The inherent problems with observational studies also must be addressed. Until that time, the use of statins in the prevention of fractures or the treatment of osteoporosis requires further study.

Bone metabolism in relation to alterations in systemic growth hormone

Growth hormone (GH) has a major role in the maintenance of bone mass in adults by regulating bone remodeling through a complex interaction of circulating GH, insulin-like growth factors (IGFs), IGF binding protein (IGFBPs), and locally produced IGFs and IGFBPs, acting in an autocrine and paracrine way. In vitro data has greatly increased our understanding of GH and IGFs effects and regulation in bone cells under controlled conditions, and especially the molecular pathways involved. However, the GH-and type I IGF-receptor are present in many tissues and various systemic factors may potentially regulate local expression of IGFs and IGFBPs in the intact organism. The use of genetically altered mice has changed this and had a major impact on defining the role of IGFs in skeletal homeostasis, and especially the role of systemic IGF-I in the development and maintenance of the adult skeleton. The focus of this review is to describe recent work on the effect of GH/IGF on remodeling in the adult skeleton emphasizing on data obtained in patient populations (i.e. acromegaly, GH deficiency, postmenopausal osteoporosis) and experimental models (i.e. animals with genetically altered expression of different GH and IGF family members) characterized by different systemic levels of these proteins. The role of IGF-I as a coupling agent between resorption and bone formation through effects on osteoprotegerin (OPG) and receptor activator of NFkappaB ligand (RANKL) are also discussed.

Osteoarthritis in the carpometacarpal joint of the thumb. Prevalence and associations with disability and mortality

BACKGROUND

This study was designed to investigate the prevalence of osteoarthritis in the carpometacarpal joint of the thumb in adults thirty years of age or older in Finland.

METHODS

Between 1978 and 1980, a representative population sample of 8000 Finns thirty years of age or older were invited to have a comprehensive health examination; 90% accepted. Hand radiographs were made of 3595 subjects. Since the examination, the subjects have been followed systematically to assess work disability and mortality by reviewing registers covering the whole population.

RESULTS

The age-adjusted prevalence of thumb carpometacarpal osteoarthritis of Kellgren grade 2, 3, or 4 was 7% for men and 15% for women. After adjustment for age, sex, and other alleged risk factors, body mass index was found to be directly proportional to the prevalence of thumb carpometacarpal osteoarthritis in both sexes. The adjusted odds ratio was 1.29 (95% confidence interval, 1.15 to 1.43) per 5-kg/m(2) increment in body mass index. No significant association was found between the physical workload history and thumb carpometacarpal osteoarthritis. Restricted mobility of the thumb and local tenderness and swelling were frequently found in conjunction with radiographic evidence of thumb carpometacarpal osteoarthritis. Advanced (grade-3 or 4) thumb carpometacarpal osteoarthritis predicted the total mortality rate in men (adjusted relative risk, 1.32; 95% confidence interval, 1.03 to 1.69). Radiographic signs of thumb carpometacarpal osteoarthritis did not predict work disability.

CONCLUSIONS

and

CLINICAL RELEVANCE

Obesity is a strong determinant of thumb carpometacarpal osteoarthritis in both sexes. The effect of thumb carpometacarpal osteoarthritis on disability and mortality in the general population is modest. Because of the rarity of ensuing disability, carpometacarpal osteoarthritis of the thumb is likely to be underdiagnosed in clinical practice.

Insulin-like growth factor I gene promoter polymorphism, collagen type II alpha1 (COL2A1) gene, and the prevalence of radiographic osteoarthritis: the Rotterdam Study

OBJECTIVE

To examine the role of an IGF-I gene promoter polymorphism in the prevalence of radiographic osteoarthritis (ROA), and study its interaction with the COL2A1 gene.

METHODS

Individuals genotyped for IGF-I (n = 1546) and COL2A1 gene polymorphisms (n = 808) were selected from a random sample (n = 1583) derived from the Rotterdam study. The presence of ROA was defined as a Kellgren score of 2 or more in at least one of four joints (knee, hip, hand, and spine). Genotype specific odds ratios (OR) were adjusted for age, sex, body mass index, and bone mineral density using logistic regression. Interaction with the COL2A1 genotype was tested.

RESULTS

Overall, no association was found between the IGF-I polymorphism and ROA. In subjects aged 65 years or younger (n = 971), the prevalence of ROA increased with the absence of the 192 base pair (bp) allele (p for trend = 0.03). Compared with homozygotes for the 192 bp allele, the prevalence of ROA was 1.4 times higher in heterozygotes (95% confidence interval, 1.0 to 1.8) and 1.9 times higher in non-carriers (1.1 to 3.3). There was evidence of interaction between the IGF-I and COL2A1 genes. Individuals with the risk genotype of both genes had an increased prevalence of ROA (OR 3.4 (1.1 to 10.7)). No effect was observed in subjects older than 65 years.

CONCLUSIONS

SUBJECTS

with genetically determined low IGF-I expression (non-carriers of the 192 bp allele) may be at increased risk of ROA before the age of 65 years. Furthermore, an interaction between the IGF-I and COL2A1 genes is suggested.

Osteoarthritis and osteoporosis: clinical and research evidence of inverse relationship

The etiology of osteoporosis (OP) and osteoarthritis (OA) is multifactorial: both constitutional and environmental factors, ranging from genetic susceptibility, endocrine and metabolic status, to mechanical and traumatic injury, are thought to be involved. When interpreting research data, one must bear in mind that pathophysiologic factors, especially in disorders associated with aging, must be regarded as either primary or secondary. Therefore, findings in end-stage pathology are not necessarily the evidence or explanation of the primary cause or event in the diseased tissue. Both aspects of research are important for potentially curative or preventive measures. These considerations, in the case of our topic--the inverse relationship of OP and OA--are of particular importance. Although the inverse relationship between two frequent diseases associated with aging, OA and OP, has been observed and studied for more than 30 years, the topic remains controversial for some and stimulating for many. The anthropometric differences of patients suffering from OA compared with OP are well established. OA cases have stronger body build and are more obese. There is overwhelming evidence that OA cases have increased BMD or BMC at all sites. This increased BMD is related to high peak bone mass, as shown in mother-daughter and twin studies. With aging, the bone loss in OA is lower, except when measured near an affected joint (hand, hip, knee). The lower degree of bone loss with aging is explained by lower bone turnover as measured by bone resorption-formation parameters. OA cases not only have higher apparent and real bone density, but also wider geometrical measures of the skeleton, diameters of long bones and trabeculae, both contributing positively to better strength and fewer fragility fractures. Not only is bone quantity in OA different but also bone quality, compared with controls and OP cases, with increased content of growth factors such as IGF and TGFbeta, factors required for bone repair. Furthermore, in vitro studies of osteoblasts recruited from OA bone have different differentiation patterns and phenotypes. These general bone characteristics of OA bone may explain the inverse relationship OA-OP and why OA cases have fewer fragility fractures. The role of bone, in particular subchondral bone, in the pathophysiology, initiation and progression of OA is not fully elucidated and is still controversial. In 1970, it was hypothesized that an increased number of microfractures lead to an increase in subchondral bone stiffness, which impairs its ability to act as a shock absorber, so that cartilage suffers more. Although subchondral bone is slightly hypomineralized because of local increased turnover, the increase in trabecular number and volume compensates for this, resulting in a stiffer structure. There is also some experimental evidence that osteoblasts themselves release factors such as metalloproteinases directly or indirectly from the matrix, which predispose cartilage to deterioration. Instead, the osteoblast regenerative capacity of bone in OP is compromised compared with OA, as suggested by early cell adhesion differences. The proposition that drugs which suppress bone turnover in OP, such as bisphosphonates, may be beneficial for OA is speculative. Although bone turnover in the subchondral region of established OA is increased, the general bone turnover is reduced. Further reduction of bone turnover, however, may lead to overmineralized (aged) osteons and loss of bone quality, resulting in increased fragility.

Osteoarthritis of finger joints in Finns aged 30 or over: prevalence, determinants, and association with mortality

BACKGROUND

Prevalence and risk factors of osteoarthritis (OA) in finger joints have been amply explored in previous studies. However, no study has focused on finger joint OA as a predictor of mortality.

OBJECTIVE

To investigate finger joint OA for its associations with alleged risk factors and with life expectancy in an extensive health survey.

METHODS

From 1978 to 1980 a representative population sample of 8000 Finns aged 30 years or over was invited to participate in a comprehensive health examination; 90% accepted. Hand radiographs were taken from 3595 subjects. By the end of 1994, 897 of these had died.

RESULTS

The prevalence of OA of Kellgren's grade 2 to 4 in any finger joint and in at least two symmetrical pairs of distal interphalangeal joints (DIPs) was 44.8% and 16.0%, respectively. Age and body mass index were significant determinants for OA both in any finger joint and in symmetrical DIP OA. The history of physical workload in women showed a positive association with OA in any finger joint. Smoking in men seemed to protect against symmetrical DIP OA. As adjusted for the determinants above, symmetrical DIP OA predicted mortality in women (relative risk (RR), 1.23; 95% confidence interval (95% CI) 1.01 to 1.51), but not in men (RR 0.89; 95% CI 0.68 to 1.16). In men, however, OA in any finger joint significantly predicted cardiovascular deaths (RR 1.42; 95% CI 1.05 to 1.92).

CONCLUSION

OA in any finger joint and symmetrical DIP OA have different risk factor profiles and predict mortality in different patterns between men and women.

IGF-I in a normal population: relation to psychosocial factors

OBJECTIVE

IGF-I has important actions on cell division, apoptosis, differentiation and metabolism, as well as on cell proliferation in vascular smooth muscle. Deficiency of GH, an important regulator of IGF-I, is associated with reduced well-being. IGF-I levels have been related to cognitive function in older individuals. The aim of the present study was to investigate the IGF-I concentrations in a normal population of men and women aged 20-74 years and to determine the influence of a variety of behavioural and psychosocial factors as well as metabolic factors on these concentrations.

DESIGN

Cross-sectional study.

PATIENTS

The study group consisted of 408 randomly selected people who had answered a questionnaire concerning health care utilization and quality of life that was administered to a random sample of 4200 people over age 17 from the northwestern region of greater Stockholm in 1995. Thirty-four men and 34 women were randomly selected from the age group 20-24 and from each 10-year age group between the ages of 25-75 years. Seventy-one per cent of the 408 people invited to come in for an examination agreed to attend, making a total sample size of 288 people.

MEASUREMENTS

A medical examination was performed and blood drawn in the morning after subjects had been fasting overnight. Before the examination, they were asked to fill out a questionnaire concerning lifestyle and psychosocial factors.

RESULTS

The distribution of IGF-I was positively skewed, but using logarithmically transformed IGF-I, a more symmetrical distribution was obtained. A linear inverse correlation was found between logarithmically transformed IGF-I levels and age which explained more than 40% of the variation in men and women. Linear correlation analysis between IGF-I and different parameters of health and disease, lifestyle and psychosocial factors, resulted in several significant correlations most of which disappeared after controlling for age. In the younger age group (20-44) there were positive correlations between IGF-I and psychosocial factors representing quality of life and psychological well-being. In the middle age group (45-59) higher IGF-I levels were related to better physical health, higher education and higher concentrations of lipoprotein Lp(a). In the older age group (over 59 years) higher levels of low-density lipoprotein-cholesterol (LDL-C) and lower levels of SHBG were associated with higher IGF-I levels.

CONCLUSION

In a randomly selected (nondisease) population, IGF-I concentrations show a consistent decrease with age in both men and women, accompanied by different association patterns relevant to disease risk. Levels are related to psychosocial parameters in the younger age group and metabolic impairment associated with increased cardiovascular risk in the older age groups. We speculate on the relative roles of age and cohort differences in rearing conditions in determining these differences.

Gender differences in regional body composition and somatotrophic influences of IGF-I and leptin

This study evaluated the arm, trunk, and leg for fat mass, lean soft tissue mass, and bone mineral content (BMC) assessed via dual-energy X-ray absorptiometry in a group of age-matched (approximately 29 yr) men (n = 57) and women (n = 63) and determined their relationship to insulin-like growth factor I (IGF-I) and leptin. After analysis of covariance adjustment to control for differences in body mass between genders, the differences that persisted (P < or = 0.05) were for lean soft tissue mass of the arm (men: 7.1 kg vs. women: 6.4 kg) and fat mass of the leg (men: 5.3 kg vs. women: 6.8 kg). Men and women had similar (P > or = 0.05) values for fat mass of the arms and trunk and lean soft tissue mass of the legs and trunk. Serum IGF-I and insulin-like growth factor binding protein-3 correlated (P < or = 0.05) with all measures of BMC (r values ranged from 0.31 to 0.39) and some measures of lean soft tissue mass for women (r = 0.30) but not men. Leptin correlated (P < or = 0.05) similarly for measures of fat mass for both genders (r values ranging from 0.74 to 0.85) and for lean soft tissue mass of the trunk (r = 0.40) and total body (r = 0.32) for men and for the arms in women (r = 0.56). These data demonstrate that 1) the main phenotypic gender differences in body composition are that men have more of their muscle mass in their arms and women have more of their fat mass in their legs and 2) gender differences exist in the relationship between somatotrophic hormones and lean soft tissue mass.

Low serum concentrations of insulin-like growth factor I are associated with femoral bone loss in a population-based sample of postmenopausal women

OBJECTIVE

Cross-sectional studies suggest that the decline in insulin-like growth factor-I (IGF-1) levels with age may contribute to age-associated bone loss. However, prospective data on the relation between circulating IGF-I and bone loss in old age have not yet been reported.

DESIGN

A longitudinal study (follow-up time 3.3 years) of the change of bone mineral density (BMD) at the lumbar spine and femoral neck in relation to serum IGF-I.

PATIENTS

A population-based sample of 173 elderly men and 107 postmenopausal women without medical conditions or medication known to significantly affect BMD or serum IGF-I levels.

MEASUREMENTS

BMD at the lumbar spine and femoral neck at baseline and after a mean follow-up-time of 3.3 years, serum-IGF-I, insulin-like growth factor binding protein 3 (IGFBP-3), sex hormone-binding globulin (SHBG) and biologically available testosterone (BAT).

RESULTS

In women, there was a graded negative relationship between quartiles of serum IGF-I and bone loss at the proximal femur (P = 0.04), which persisted after adjustment for potential covariables of bone loss and serum IGF-I. In subgroup analysis the association between serum IGF-I and change in BMD was only apparent in women more than 10 years past menopause (r = + 0,38, P = 0.01). No association between serum IGF-I levels and changes in BMD was observed in men. IGF-I levels were not associated with changes in spinal BMD.

CONCLUSIONS

Our data suggest that low circulating levels of IGF-I in elderly women are associated with greater femoral bone loss, and support previous findings of gender differences in the relation between serum IGF-I and BMD in older age.

An update on the science and therapy of obesity and its relationship to osteoarthritis

Obesity and osteoarthritis are two commonly encountered clinical problems that can lead to significant physical and emotional disability. This report examines the association between obesity and osteoarthritis, and discusses potential mechanisms by which obesity influences osteoarthritis. Special attention is devoted to reviewing the molecular and genetic mechanisms that underlie the development of clinical obesity. Improved understanding of obesity will hopefully lead to improved treatment and subsequent amelioration of this important risk factor for osteoarthritis.

Circulating levels of insulin-like growth factors and their binding proteins in patients with chronic liver disease: lack of correlation with bone mineral density

BACKGROUND/AIMS

Insulin-like growth factor-I (IGF-I) levels are low in patients with chronic liver disease (CLD) and have been found to correlate with measurements of bone mineral density (BMD) in men with viral cirrhosis. The aim of this study was to investigate the relationship between circulating IGF-I levels and BMD in patients with CLD of other causes.

METHODS

Fifty-eight patients with CLD were included. Age- and sex-matched normal individuals served as controls. Serum levels of IGF-I and IGF-II and their binding proteins (IGFBP-1-3) were measured by radioimmunoassay. BMD was measured by dual energy X-ray absorptiometry.

RESULTS

IGF-I levels were 57+/-33 and 136+/-48 ng/ml; p<0.0001 in patients and controls, respectively. IGF-II and IGFBP-3 levels were lower (p<0.0001) and IGFBP-1 and IGFBP-2 levels were higher in patients compared with controls (p<0.0005 and p<0.0001, respectively). All growth factors, except for IGFBP-2, correlated with parameters of liver function. In a multiple regression analysis, adjusting for age, no correlation was found between IGF-I, IGF-II, IGFBP-1-3 and BMD in either patients or controls.

CONCLUSION

Patients with CLD have low levels of IGF-I, IGF-II and IGFBP-3 that correlate with liver function. No relationship was found between low levels of growth factors and BMD.

Influence of insulin-like growth factor-1 and leptin on bone mass in healthy postmenopausal women

This study examines the influence of circulating insulin-like growth factor-1 (IGF-1) and serum leptin on bone mass as well as modulation of bone mass during skeletal development. Moreover, an inverse relationship between IGF-1 and leptin is reported. To evaluate the effects of serum IGF-1 and serum leptin on bone mass in healthy postmenopausal women, and the possible role of IGF-1 in leptin production, we studied a population of 123 women, aged 39-82 years. Bone mineral density (BMD) was determined by whole-body dual-energy X ray absorptiometry, which also enables measurement of body composition. Bone metabolism was assessed by measuring serum total alkaline phosphatase (TAP) and urinary hydroxyproline/creatinine (HP/Cr) excretion. IGF-1 correlated significantly with age (r = -0.28, p < 0.01) and years since menopause (r = -0.24, p < 0.01). A negative correlation was also found with weight and body mass index (r = -0.15, p < 0.05 and r = -0.19, p < 0.05, respectively). Leptin values were strongly correlated with weight (r = 0.7, p < 0.01), BMI (r = 0.7, p < 0.01), fat mass (r = 0.77, p < 0.01), and lean mass (r = 0.39, p < 0.01); a significant correlation was found with total body BMD (r = 0.29, p < 0.01), TAP (r = 0.15, p < 0.05), and HP/Cr (r = 0.18, p < 0.05). After adjustment for BMI, the significance of these relationships disappeared, demonstrating the lack of effect of serum leptin on BMD and bone turnover independent of body weight. On the other hand, the relationship between BMD and fat mass remained statistically significant after adjusting for serum leptin (r = 0.15, p < 0.05). Controlling for BMI eliminated the significant inverse correlation between IGF-1 and leptin; significant differences in leptin levels were found among women in the lower and higher quartile of IGF-1, suggesting that leptin production may be inhibited only at high values of serum IGF-1. We conclude that serum IGF-1 and serum leptin have no direct effect on bone mass and bone turnover.

Lumbar osteoarthritis, bone mineral density, and quantitative ultrasound

Low bone mass is a major risk factor for osteoporotic fractures. Thus, bone density evaluation, performed by Dual Energy X-ray Absorptiometry (DXA) is important for diagnosis and monitoring treatment of osteoporosis. The accuracy of DXA, particularly at the lumbar spine, can be affected by several factors such as degenerative diseases. To evaluate the effects of vertebral osteophytosis on densitometric measurements, we examined 198 women, aged 32-81 years, who had undergone lateral X-ray of the lumbar spine. We classified patients according to different grades of osteophytosis, and evaluated bone density at the lumbar spine and the proximal femur by DXA. We also performed quantitative ultrasound at the heel (QUS). Patients with severe osteophytosis were significantly older (p < 0.0005), and values were adjusted for this parameter. We observed a significant increase in lumbar bone density with worsening osteophytosis (p < 0.02). On the contrary, no significant differences were found at the femur and QUS. According to bone density at the femoral neck, we subdivided patients into two groups: osteoporotic (group A) and non-osteoporotic (group B). Both groups showed increasingly high bone density at the spine with worsening osteophytosis (A: p < 0.01; B: p < 0.02). No differences were found in all the other evaluations. In conclusion, lumbar spine measurement is dramatically influenced by osteophytosis, particularly in the elderly. Consequently, other strategies should be performed such as evaluation of the hip and also measurement of the heel by ultrasound, which could be an interesting approach in these cases.

Oral statins and increased bone-mineral density in postmenopausal women

Experimental evidence suggests that the cholesterol-lowering drugs statins increase bone formation. We report a significant increase of bone-mineral density associated with taking statins in postmenopausal women.

Low circulating insulin-like growth factor I in coeliac disease and its relation to bone mineral density

BACKGROUND

Patients with coeliac disease have low bone mineral density (BMD), but the underlying mechanisms are unclear. Our aim was to study circulating insulin-like growth factor I (IGF-I) and its possible relationship to BMD in adults with untreated coeliac disease and after 1 year on a gluten-free diet.

METHODS

In 29 consecutive adult coeliac patients fasting IGF-I and BMD (n = 28) were examined before and 1 year after starting a gluten-free diet. Intact parathyroid hormone (PTH) was measured (n = 20) before the gluten-free diet was started.

RESULTS

Untreated coeliac patients had lower IGF-I values than controls matched for age and sex, and their BMD was low. A relationship was observed between BMD and IGF-I but not independent of age and body mass index. During the 1st year on a gluten-free diet BMD increased (P < 0.001), as did the circulating IGF-I levels in 21 of the 29 patients (P = 0.078). In the subgroup of 14 patients with normal initial PTH the increase in IGF-I correlated positively with the increase in BMD (femoral trochanter, r = 0.62, P < 0.05, and lumbar spine, r = 0.70, P < 0.02).

CONCLUSIONS

BMD and circulating IGF-I levels are low in adults with untreated coeliac disease. In patients with normal initial PTH level there is an association between the change in BMD and circulating IGF-I, although this parallel increase may not be causally connected.

Low IGF-I levels in hip fracture patients. A comparison of 20 coxarthrotic and 23 hip fracture patients

We measured total body bone density and body composition with dual energy x-ray absorptiometry in 43 elderly patients, 23 with hip fracture and 20 with coxarthrosis, after surgery and after 6 months. Insulin-like growth factor-1 (IGF-I), a polypeptide known to affect bone metabolism, and two of its binding proteins (IGFBP-1, IGFBP-3) were measured preoperatively and after 6 months. Normal serum IGF-I levels are dependent on adequate nutrition and normal secretion of growth hormone (GH). We found consistently lower levels of IGF-I and IGFBP-3 and a tendency to higher levels of IGFBP-1 in the patients with hip fractures, who also had a lower total body mass, lower fat mass and bone mineral density than the coxarthrosis group, indicating a more catabolic state in the patients with hip fracture, even 6 months after the trauma.

Association between insulin-like growth factor I and bone mineral density in older women and men: the Framingham Heart Study

Few studies of the GH axis and bone have focused specifically on elderly people. The objective of this study was to determine the association between insulin-like growth factor I (IGF-I) and bone mineral density (BMD) in 425 women and 257 men aged 72-94 who participated in the Framingham Osteoporosis Study component of the Framingham Heart Study in 1992-1993. Serum IGF-I level was determined by RIA. BMD at three femoral sites and the lumbar spine was determined by dual x-ray absorptiometry, and at the radius by single-photon absorptiometry. IGF-I level was positively associated with BMD at all five sites (Ward's area, femoral neck, trochanter, radius, and lumbar spine) in women after adjustment for weight loss and other factors (P < or = 0.01) and protein intake in a subset of participants (0.006 < P < 0.07). A threshold effect of higher BMD was evident at each of the 3 femoral sites and the spine (P < 0.03) but not at the radius for women in the highest quintile of IGF-I (> or = 179 g/liter) vs. those in the lowest four quintiles. IGF-I was not significantly associated with BMD in men. These results indicate that higher IGF-I levels are associated with greater BMD in very old women, and suggest that future clinical trials employing GH may have a role in the development of treatments for older women with osteoporosis.

Insulin-like growth factor-I and bone mineral density

To assess the relationship between insulin-like growth factor-I (IGF-I) and bone mineral density (BMD) 201 healthy postmenopausal women (age 41-68 years) within 10 years of menopause were studied. In all subjects, BMD at the lumbar spine and left hip were measured using dual-energy X-ray absorptiometry and blood samples were obtained. In all subjects, serum IGF-I and parathyroid hormone (PTH) were measured. In a subgroup of these subjects serum concentrations of IGF-binding protein-3 (IGFBP-3), osteocalcin (OC), bone-specific alkaline phosphatase (BALP), tartrate-resistant acid phosphatase (TRAP), and carboxyterminal propeptide of type I procollagen (PICP) were also measured. Serum IGF-I correlated significantly with age (r = -0.159, p = 0.0241), serum OC (r = 0.226, p = 0.0131), BALP (r = 0.259, p < 0.0001), and TRAP (r = 0.261, p < 0.0015), but not with PICP, PTH, or BMD at any site. Although there was a strong correlation between IGF-I and IGFBP-3 (r = 0.559, p < 0.0001), there was no correlation between IGFBP-3 and any of the markers of bone turnover (OC, BALP, TRAP, or PICP) nor with PTH or BMD at any site. We conclude that IGF-I and markers of bone turnover are related, but there is no relationship between IGF-I and BMD.

Concentration of insulin-like growth factor (IGF)-I and -II in iliac crest bone matrix from pre- and postmenopausal women: relationship to age, menopause, bone turnover, bone volume, and circulating IGFs

Insulin-like growth factor-I (IGF-I) and -II are important local regulators of bone metabolism, but their role as determinants of human bone mass is still unclear. In the present study, we analyzed the concentration of IGF-I and -II in the bone matrix of 533 human biopsies from the iliac crest that were obtained during surgery for early breast cancer. There was an inverse association of bone matrix IGF-I concentration with age that was unaffected by menopause. Bone matrix IGF-I was positively associated with histomorphometric and biochemical parameters of bone formation and bone resorption and with cancellous bone volume. Based on the estimates of the linear regression analysis, women with a bone matrix IGF-I concentration 2 SD above the mean had a 20% higher bone volume than women with a bone matrix IGF-I concentration 2 SD below the mean. In contrast, serum IGF-I was neither correlated with bone turnover nor with bone volume and was only weakly associated with bone matrix IGF-I when adjusted for the serum concentration of IGF binding protein-3. Bone matrix IGF-II was positively associated with the osteoblast surface, but in contrast to IGF-I, tended to be positively associated with age and was unrelated to cancellous bone volume. In summary, our study suggests the following. 1) The concentration of IGF-I in cancellous bone undergoes age-related decreases that are similar to those of circulating IGF-I. 2) Menopause has no effect on this age-related decline. 3) Physiological differences in bone matrix IGF-I are associated with differences in iliac crest cancellous bone volume. 4) Bone matrix IGF-I is a better predictor of cancellous bone volume than circulating IGF-I. 5) The role of IGF-II in human bone tissue is clearly distinct from that of IGF-I.

What is the relationship between osteoarthritis and osteoporosis?

Several epidemiological studies have shown a lower incidence and prevalence of hip fractures in people with osteoarthritis (OA) and vice versa which has led to numerous studies examining the association between OA and osteoporosis more generally. There is felt to be an inverse relationship between these two diseases and the evidence for and against this association is discussed. The evidence for an association with osteoporosis is stronger for large joint OA than hand OA or primary generalized OA. A number of possible mechanisms for this association are discussed such as genetic factors, common risk factors, role of subchondral bone in cartilage damage and growth factors. The incidence and prevalence of one disease in the presence of the other is discussed. Despite the inverse relationship seen in some studies, there is currently no evidence that treatment of one disease can have a detrimental effect on the other.

Understanding the relationship between body weight and osteoarthritis

Overweight people are at high risk of developing knee osteoarthritis (OA) and may also be at increased risk of hand and hip OA. Furthermore, being overweight accelerates disease progression in knee OA. While the increased joint stress accompanying obesity may explain the strong linkage between obesity and knee OA risk, it does not necessarily explain why obese people have a high risk of disease in the hand nor why obese women are at higher comparative risk of knee disease than obese men. Unfortunately, studies of metabolic factors linked to obesity have not provided an explanation for these findings. There are a paucity of data on weight loss as a treatment for OA, but preliminary information suggests it is especially effective in knee disease and that even small amounts of weight reduction may have favourable effects.