Increased production of TNF-alpha may play a role in osteoporosis in cystic fibrosis patients

Relationship between insulin-like growth factor I, dehydroepiandrosterone sulfate and proresorptive cytokines and bone density in cystic fibrosis

INTRODUCTION

Patients with cystic fibrosis (CF) are known to be at risk for early osteoporosis, and the mechanisms that mediate bone loss are still being delineated. The aim of the present investigation was to investigate if a correlation exists in these patients between skeletal measurements by dual-energy x-ray absorptiometry (DXA) and two anabolic factors, dehydroepiandrosterone (DHEA) and insulin-like growth factor I (IGF-I), and proresorptive factors such as the cytokines interleukin-1beta, tumor necrosis factor alpha, and interleukin-6.

METHODS

We studied 32 outpatients (18 females; mean age: 26.2+/-7.9 years) at a tertiary care medical center. The subjects had venous samples obtained, underwent anthropometric and bone mineral density (BMD) measurements, and completed a health survey. Serum IGF-I concentrations were below the age-adjusted mean in 78% of the participants, and DHEA sulfate (DHEAS) concentrations were low in 72%. Serum concentrations of all cytokines were on the low side of normal; nonetheless, there was a modest inverse correlation between IL-1beta and BMD at all sites.

RESULTS

In univariate analyses, IGF-I and DHEAS were significant correlates of BMD or bone mineral content. In final multivariate models controlling for anthropometric and other variables of relevance to bone density, only IGF-I was identified as a significant independent skeletal predictor. While alterations in DHEAS, IGF-I, and specific cytokines may contribute to skeletal deficits in patients with CF, of these factors a low IGF-I concentration appears to be most strongly correlated with BMD.

CONCLUSIONS

These findings may have therapeutic implications for enhancing bone density in these patients.

Musculoskeletal manifestations in cystic fibrosis

Although bone and joint manifestations are common in children with cystic fibrosis (CF), they have received little attention in adults. As compared to healthy individuals, bone mineral density is low, even with calcium intakes greater than 1500 mg/d. Nevertheless, calcium and phosphate levels in blood and urine are often normal, and vitamin D levels vary. Short stature with a low body mass index and central hypogonadism are the rule in these patients. Fractures and kyphosis are often reported. CF arthropathy occurs in 2-8.5% of patients. Arthritis develops, and there may be skin eruptions. Non-steroidal antiinflammatory drug therapy is effective. Hypertrophic osteoarthropathy associated with respiratory failure is present in 2-7% of patients. Rheumatoid arthritis, spondyloarthropathies, sarcoidosis, and amyloidosis have been reported in association with CF. Knee pain due to patellofemoral syndrome, quinolone-induced arthropathy, and mechanical back pain have been described. Rheumatoid factor titers are higher than in healthy controls, particularly in patients with episodic arthritis. No data are available on antiperinuclear factor or antikeratin antibody titers. Tests for antinuclear antibody are usually negative. Circulating immune complex levels and antibodies to heat shock proteins may be elevated. Antineutrophil cytoplasmic antibody of the bactericidal/permeability-increasing protein (BPI) or azurocidin (AZ) type has been reported, often in high titers (up to 40%).

Normal bone mineral density in cystic fibrosis

BACKGROUND

Osteoporosis has been reported as a complication of cystic fibrosis (CF).

AIMS

To measure bone mineral density (BMD) in non-acutely ill adults and bone mineral content (BMC) in children with CF.

METHODS

We analysed data from 28 adults and 13 children with CF. Corticosteroid use was minimal for the year prior to study in both groups. Dual x ray absorptiometry was used to measure total body and regional bone mineral density in adults. In children, whole body BMC was measured. Lean tissue mass (LTM) was also measured in all subjects. There were two control groups: A (matched for LTM and height, in addition to age and gender); and B (matched for age and gender only).

RESULTS

There was no difference in whole body or regional BMD density between adult CF patients and control A subjects. Both whole body and regional BMD were significantly lower in adult CF patients than in control B subjects. Total body BMD was correlated with body mass index, LTM, and percent fat in both CF and control subjects. There was no significant correlation between total body BMD or regional BMD and either NIH clinical status scores, or pulmonary function tests in adults. There was no difference in total body BMC between CF children and control A subjects. Total body BMC was significantly lower in CF children than in control B subjects. There was no correlation between pulmonary function results and BMC in children.

CONCLUSION

Osteopenia and osteoporosis in CF may be caused more by malnutrition and chronic use of intravenous or oral corticosteroids than by a CF related inherent defect in BMD. Appropriate "normal" data should be selected when determining whether or not osteoporosis is present in a CF patient.

Bone mineral density in lung-transplant recipients before and after graft: prevention of lumbar spine post-transplantation-accelerated bone loss by pamidronate

BACKGROUND

Lung-transplant recipients are at risk of osteoporosis. They may have low bone mass even before posttransplantation immunosuppressive therapy. We studied bone mineral density (BMD) before and after lung transplantation and compared the efficacy of antiresorptive therapies to calcium and vitamin D supplementation.

METHODS

Areal BMD was assessed in 42 patients awaiting lung transplantation and measured again after surgery at 6 (n = 29), and at 12 months (n = 20). Nineteen patients received antiresorptive therapy (30 mg pamidronate IV every 3 months (n = 14), or hormonal replacement therapy (n = 5)), and 10 patients received only calcium and vitamin D supplements.

RESULTS

Mean age- and gender-adjusted lumbar spine (LS) and femoral neck (FN) BMD was significantly decreased prior to transplantation (- 0.6 +/- 0.2, p< 0.01, and - 1.5 +/- 0.2 standard deviation, p < 0.001, respectively). At that time, 29% were osteoporotic (T-score < - 2.5 below the peak bone mass), while 55% were below - 1.0 T-score. Antiresorptive therapy decreased the rate of LS bone loss during the first 6 months and led to a significant increase of BMD at 1 year, with LS changes of + 0.2 +/- 0.1 vs - 0.4 +/- 0.1 Z-score in the calcium-vitamin D group (p< 0.002), and + 0.2 +/- 0.1 vs - 0.04 +/- 0.1 for FN (NS). One out of 20 patients experienced clinically evident fractures during antiresorptive therapy, and 3 out of 12 in the calcium-vitamin D group.

CONCLUSION

A significant proportion of patients awaiting lung transplantation was osteoporotic or osteopenic. Antiresorptive therapy (pamidronate or hormone-replacement therapy (HRT)) prevented accelerated LS bone loss after graft.

Inflammation in cystic fibrosis and its management

Pulmonary complications are by far the most serious complications in cystic fibrosis (CF). In response to endobronchial bacterial infections, the long-term consequences of chronically activated polymorphonuclear leukocytes (neutrophils) are thought to cause loss of lung function and premature death. Effective anti-inflammatory therapy implies that we understand the complex networks of the immune response with its myriads of mediators on effector cells. We have many steps to go in this context, but science has already shed some light on inflammatory mechanisms in CF airways, and anti-inflammatory treatment strategies have been applied clinically with some success. The aim of this chapter is to review our present knowledge, and we will focus on early inflammation, bacterial persistence mechanisms, neutrophil activation, cytokines and nitric oxide together with anti-inflammatory treatment strategies in CF patients.

Osteoporosis: a new challenge in cystic fibrosis

The increased life expectancy of patients with cystic fibrosis (CF) may lead to medical complications such as osteoporosis. Based on data collected through a MEDLINE search (1985-May 1999) and review of references for additional relevant articles, nutrition status, weight, and disease severity are factors most highly correlated with osteopenia. Links also were noted with calcium and vitamin D intake, hypogonadism, chronic inflammation, and age, but findings in these areas are not consistent from one report to the next. Increased fracture rates and kyphosis are consequences of osteoporosis. Simple measures such as compliance with recommended nutrition guidelines and restrictions in corticosteroid therapy could be considered first-line management options. Further studies must be conducted to clarify factors involved in the etiology of osteoporosis in patients with CF and to identify the best treatment and prevention methods.