Update on cystic fibrosis-related bone disease: a special focus on children

Nutritional Care in Children with Cystic Fibrosis

Patients with cystic fibrosis (CF) are prone to malnutrition and growth failure, mostly due to malabsorption caused by the derangement in the chloride transport across epithelial surfaces. Thus, optimal nutritional care and support should be an integral part of the management of the disease, with the aim of ameliorating clinical outcomes and life expectancy. In this report, we analyzed the nutrition support across the different ages, in patients with CF, with a focus on the relationships with growth, nutritional status, disease outcomes and the use of the CF transmembrane conductance regulator (CFTR) modulators. The nutrition support goal in CF care should begin as early as possible after diagnosis and include the achievement of an optimal nutritional status to support the growth stages and puberty development in children, that will further support the maintenance of an optimal nutritional status in adult life. The cornerstone of nutrition in patients with CF is a high calorie, high-fat diet, in conjunction with a better control of malabsorption due to pancreatic enzyme replacement therapy, and attention to the adequate supplementation of fat-soluble vitamins. When the oral caloric intake is not enough for reaching the anthropometric nutritional goals, supplemental enteral feeding should be initiated to improve growth and the nutritional status. In the last decade, the therapeutic possibilities towards CF have grown in a consistent way. The positive effects of CFTR modulators on nutritional status mainly consist in the improvement in weight gain and BMI, both in children and adults, and in an amelioration in terms of the pulmonary function and reduction of exacerbations. Several challenges need to be overcome with the development of new drugs, to transform CF from a fatal disease to a treatable chronic disease with specialized multidisciplinary care.

Treatment of cystic fibrosis related bone disease

The advent of highly effective CFTR modulator therapies has slowed the progression of pulmonary complications in people with cystic fibrosis. There is increased interest in cystic fibrosis bone disease (CFBD) due to the increasing longevity of people with cystic fibrosis. CFBD is a complex and multifactorial disease. CFBD is a result of hypomineralized bone leading to poor strength, structure and quality leading to susceptibility to fractures. The development of CFBD spans different age groups. The management must be tailored to each group with nuance and based on available guidelines while balancing therapeutic benefits to risks of long-term use of bone-active medication. For now, the mainstay of treatment includes bisphosphonates. However, the long-term effects of bisphosphonate treatment in people with CF are not fully understood. We describe newer agents available for osteoporosis treatment. Still, the lack of data behooves trials of monoclonal antibodies treatments such as Denosumab and Romozosumab and anabolic bone therapy such as teriparatide and Abaloparatide. In this review, we also summarize screening and non-pharmacologic treatment of CFBD and describe the various options available for the pharmacotherapy of CFBD. We address the prospect of CFTR modulators on bone health while awaiting long-term trials to describe the effects of these medications on bone health.

Triage for Malnutrition Risk among Pediatric and Adolescent Outpatients with Cystic Fibrosis, Using a Disease-Specific Tool

Malnutrition prevails in considerable proportions of children with Cystic Fibrosis (CF), and is often associated with adverse outcomes. For this, routine screening for malnutrition is pivotal. In the present cross-sectional study, we aimed to assess the risk for malnutrition in pediatric outpatients with CF. A total of 76 outpatients (44 girls, 11.9 ± 3.9 years old, 39.5% adolescents) were recruited and anthropometric, clinical, dietary and respiratory measures were collected. All outpatients were screened for malnutrition risk with a validated disease-specific instrument. Most children exhibited a low risk for malnutrition (78.9%), whereas none of the participants were characterized as having a high malnutrition risk. In the total sample, malnutrition risk was positively associated with age (r = 0.369, p = 0.001), and inversely related to the body mass index (r = −0.684, p < 0.001), height z-score (r = −0.264, p = 0.021), and forced expiratory volume (FEV₁%, r = −0.616, p < 0.001). Those classified as having a low malnutrition risk were younger (p = 0.004), heavier (p < 0.001) and taller (p = 0.009) than their counterparts with a moderate risk. On the other hand, patients in the moderate risk group were more likely pubertal (p = 0.034), with a reduced mid-upper arm fat area (p = 0.011), and worse pulmonary function (p < 0.001). Interestingly, none of the children attaining ideal body weight were classified as having a moderate malnutrition. risk, whereas 37.5% of the patients allocated at the moderate risk group exhibited physiological lung function. In this cohort of outpatients with CF that were predominantly well-nourished and attained physiological lung function, malnutrition risk was identified only in small proportions of the sample. Our data support that patients that are older, pubertal, or have diminished fat mass are at greater risk for malnutrition.

How to manage osteoporosis before the age of 50

This narrative review discusses several aspects of the management of osteoporosis in patients under 50 years of age. Peak bone mass is genetically determined but can also be affected by lifestyle factors. Puberty constitutes a vulnerable period. Idiopathic osteoporosis is a rare, heterogeneous condition in young adults due in part to decreased osteoblast function and deficient bone acquisition. There are no evidence-based treatment recommendations. Drugs use can be proposed to elderly patients at very high risk. Diagnosis and management of osteoporosis in the young can be challenging, in particular in the absence of a manifest secondary cause. Young adults with low bone mineral density (BMD) do not necessarily have osteoporosis and it is important to avoid unnecessary treatment. A determination of BMD is recommended for premenopausal women who have had a fragility fracture or who have secondary causes of osteoporosis: secondary causes of excessive bone loss need to be excluded and treatment should be targeted. Adequate calcium, vitamin D, and a healthy lifestyle should be recommended. In the absence of fractures, conservative management is generally sufficient, but in rare cases, such as chemotherapy-induced osteoporosis, antiresorptive medication can be used. Osteoporosis in young men is most often of secondary origin and hypogonadism is a major cause; testosterone replacement therapy will improve BMD in these patients. Diabetes is characterized by major alterations in bone quality, implying that medical therapy should be started sooner than for other causes of osteoporosis. Primary hyperparathyroidism, hyperthyroidism, Cushing's syndrome and growth hormone deficiency or excess affect cortical bone more often than trabecular bone.

CFTR-deficient pigs display alterations of bone microarchitecture and composition at birth

BACKGROUND

The lack of cystic fibrosis transmembrane conductance regulator (CFTR) function causes cystic fibrosis (CF), predisposing to severe lung disease, reduced growth and osteopenia. Both reduced bone content and strength are increasingly recognized in infants with CF before the onset of significant lung disease, suggesting a developmental origin and a possible role in bone disease pathogenesis. The role of CFTR in bone metabolism is unclear and studies on humans are not feasible. Deletion of CFTR in pigs (CFTR ^-/- pigs) displays at birth severe malformations similar to humans in the intestine, respiratory tract, pancreas, liver, and male reproductive tract.

METHODS

We compared bone parameters of CFTR ^-/- male and female pigs with those of their wild-type (WT) littermates at birth. Morphological and microstructural properties of femoral cortical and trabecular bone were evaluated using micro-computed tomography (μCT), and their chemical compositions were examined using Raman microspectroscopy.

RESULTS

The integrity of the CFTR ^-/- bone was altered due to changes in its microstructure and chemical composition in both sexes. Low cortical thickness and high cortical porosity were found in CFTR ^-/- pigs compared to sex-matched WT littermates. Moreover, an increased chemical composition heterogeneity associated with higher carbonate/phosphate ratio and higher mineral crystallinity was found in CFTR ^-/- trabecular bone, but not in CFTR ^-/- cortical bone.

CONCLUSIONS

The loss of CFTR directly alters the bone composition and metabolism of newborn pigs. Based on these findings, we speculate that bone defects in patients with CF could be a primary, rather than a secondary consequence of inflammation and infection.

Markers of bone turnover are reduced in patients with CF related diabetes; the role of glucose

BACKGROUND

Cystic fibrosis(CF) related diabetes(CFRD) and osteoporosis are prevalent in adult patients with CF. We aimed to evaluate if CFRD and markers of glucose metabolism and inflammation are associated with bone turnover in CF.

METHODS

Cross sectional study at the adult section at the Copenhagen CF Center from January-October 2017. Fasting blood samples, including bone turnover markers(BTMs) and cytokines, Dual-x-ray absorptiometry scan and oral glucose tolerance test were performed. Lung-transplanted participants and patients in antiosteoporotic treatment were excluded from analyses.

RESULTS

102 patients were included of whom 19 had a prior CFRD diagnosis. CFRD patients had lower procollagen type 1 N-terminal propeptide(P1NP) and C-Terminal cross-linked Telopeptide(CTX) levels compared to CF patients without diabetes (median[IQR]) 49.5 μg/l [29.6,57.1] vs 56.9 μg/l [38.2,74.3], p = .03 and 0.2 μg/l [0.1,0.3] vs 0.4 μg/l [0.3,0.6], p < .01, respectively. Fasting plasma glucose(FPG) was negatively associated with the bone formation markers P1NP and osteocalcin and bone resorption marker CTX. In multivariate linear regression FPG remained a significant predictor of P1NP -1.07 [-1.09;-0.01] and CTX -1.13 [-1.21;-1.06]. Bone mineral density Z-score was not different between patients with and without CFRD but FPG was negatively associated with hip and femoral neck Z-score. There was no consistent association between inflammatory cytokines and BTMs.

CONCLUSIONS

Bone turnover markers are reduced in CF patients with CFRD and negatively associated with glucose levels. Extra attention towards frequent hyperglycemia in CF patients should be taken when evaluating decreased BMD. Glycemia may be a future target for improving outcome in CFBD.

Relationship between Physical Activity and Fatigue in Adults with Cystic Fibrosis

Purpose: We examined the relationship between the amount of physical activity and level of fatigue in adults with cystic fibrosis (CF). Method: Participants were recruited from the Toronto Adult Cystic Fibrosis Centre at St. Michael's Hospital. Participants completed the Habitual Activity Estimation Scale, the Multidimensional Fatigue Inventory, and the Depression subscale of the Hospital Anxiety and Depression Scale, in that order. Descriptive statistics and linear and multiple regressions were computed. Results: Over a 6-month period, 51 individuals were approached, and 22 (10 men, 12 women) participated in this study. The participants' median age was 33, and forced expiratory volume in 1 second (FEV₁) was 64% predicted. When holding both FEV₁ and depression constant, a significant negative correlation was found between total active hours per weekday and general fatigue (β=-0.735, p=0.03); there was a negative trend between total active hours per weekday and physical fatigue (β=-0.579, p=0.09). Conclusions: This study is the first to demonstrate that among adults with CF, a higher level of physical activity is associated with a lower level of general and physical fatigue when controlling for lung function and level of depression. Physical activity may be used as a means of mitigating the levels of general and physical fatigue in people with CF.

Effect of high dose vitamin D3 therapy on serum vitamin D3 levels in vitamin D insufficient adults with cystic fibrosis

BACKGROUND

The effect of a high dose oral cholecalciferol repletion strategy in Vitamin D insufficient adults with CF is still unknown. Therefore, we assessed the effectiveness of our current approach, giving oral vitamin D3 supplementation at a dose of 10,000 IU from Monday to Friday for a total of 50,000 IU D3 weekly in vitamin D insufficient adult with CF.

METHODS

We performed a retrospective chart review of all 59 adult CF patients between the ages of 17 and 64 years routinely followed at the CF Adult Program of Winnipeg Health Sciences Centre. Through consultation with the endocrinologist, our clinic vitamin D repletion protocol for treating CF adult patients who have serum 25-hydroxyvitamin D (25-OHD) < 30 ng/ml (<75 nmol/L) was to prescribe vitamin D3 10,000 IU orally from Monday to Friday (or the weekly equivalent of 50,000 IU) for 12 weeks in addition to their regular CF vitamin that supplied from 800 to 2000 IU vitamin D3 daily. Cholecalciferol was conveniently administered orally as either one capsule (oil-based) 10,000 IU or one tablet (powder-based) 10,000 IU. All patients were instructed to obtain follow-up serum 25-OHD levels post completion of treatment.

RESULTS

Of the 59 adult patients at our CF Clinic, 35 patients (59%) had below optimal serum 25-OHD levels. Of the 35 patients identified, 10 patients with insufficient serum 25-OHD levels between 10 and 30 ng/ml (25-75 nmol/L) fulfilled the inclusion criteria. A significant increase in serum 25-OHD levels was observed (P < 0.01) from mean value of 21.6 ± 5.9 ng/ml (54.1 ± 14.8 nmol/L) at baseline to 31.7 ± 9.1 ng/ml (79.3 ± 22.8 nmol/L) ≥ 2 months post intervention. The current treatment approach was successful in treating Vitamin D insufficiency in 70% of the patients with low 25-OHD levels.

CONCLUSION

The results of this study demonstrate that a large number of adults attending Winnipeg Health Sciences Centre CF Clinic have serum 25-OHD levels below 30 ng/ml (75 nmol/L). This supports the need for dedicated and individualized approach to manage this condition. High dose therapy of vitamin D3, although a more aggressive treatment approach, may result in achieving optimal levels of serum 25-OHD in adults with CF.

Children and adolescents with cystic fibrosis display moderate bone microarchitecture abnormalities: data from high-resolution peripheral quantitative computed tomography

We investigated whether bone microstructure assessed by high-resolution peripheral quantitative tomography (HR-pQCT) could be altered in children and teenagers with cystic fibrosis (CF). In comparison to their healthy counterparts, bone microstructure was mildly affected at the tibial level only.

INTRODUCTION

Cystic fibrosis-related bone disease (CFBD) may alter bone health, ultimately predisposing patients to bone fractures. Our aim was to assess bone microstructure using high-resolution peripheral quantitative tomography (HR-pQCT) in a cohort of children and teenagers with CF in comparison to age-, puberty-, and gender-matched healthy volunteers (HVs).

METHODS

In this single-center, prospective, cross-sectional study, we evaluated the HR-pQCT bone parameters of CF patients and compared them to those of the healthy volunteers.

RESULTS

At a median age of 15.4 [range, 10.5-17.9] years, 37 CF patients (21 boys) with 91% [range, 46-138%] median forced expiratory volume in 1 s were included. At the ultradistal tibia, CF patients had a smaller bone cross-sectional area (579 [range, 399-1087] mm²) than HVs (655 [range, 445-981] mm²) (p = 0.027), related to a decreased trabecular area, without any significant differences for height. No other differences were found (trabecular number, separation, thickness, or distribution) at the radial or tibial levels. Bone structure was different in patients receiving ursodeoxycholic acid and those bearing two F508del mutations.

CONCLUSION

In our cohort of children and teenagers with good nutritional and lung function status, bone microstructure evaluated with HR-pQCT was not severely affected. Minimal microstructure abnormalities observed at the tibial level may be related to the cystic fibrosis transmembrane conductance regulator defect alone; the long-term consequences of such impairment will require further evaluation.

Brazilian guidelines for the diagnosis and treatment of cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive genetic disorder characterized by dysfunction of the CFTR gene. It is a multisystem disease that most often affects White individuals. In recent decades, various advances in the diagnosis and treatment of CF have drastically changed the scenario, resulting in a significant increase in survival and quality of life. In Brazil, the current neonatal screening program for CF has broad coverage, and most of the Brazilian states have referral centers for the follow-up of individuals with the disease. Previously, CF was limited to the pediatric age group. However, an increase in the number of adult CF patients has been observed, because of the greater number of individuals being diagnosed with atypical forms (with milder phenotypic expression) and because of the increase in life expectancy provided by the new treatments. However, there is still great heterogeneity among the different regions of Brazil in terms of the access of CF patients to diagnostic and therapeutic methods. The objective of these guidelines was to aggregate the main scientific evidence to guide the management of these patients. A group of 18 CF specialists devised 82 relevant clinical questions, divided into five categories: characteristics of a referral center; diagnosis; treatment of respiratory disease; gastrointestinal and nutritional treatment; and other aspects. Various professionals working in the area of CF in Brazil were invited to answer the questions devised by the coordinators. We used the PubMed database to search the available literature based on keywords, in order to find the best answers to these questions.

A retrospective analysis of longitudinal changes in bone mineral content in cystic fibrosis

BACKGROUND

We aimed to describe the longitudinal changes in bone mineral content and influencing factors, in children with cystic fibrosis (CF).

METHODS

One hundred children (50 females) had dual X-ray absorptiometry (DXA) performed. Of these, 48 and 24 children had two to three scans, respectively over 10 years of follow-up. DXA data were expressed as lumbar spine bone mineral content standard deviation score (LSBMCSDS) adjusted for age, gender, ethnicity and bone area. Markers of disease, anthropometry and bone biochemistry were collected retrospectively.

RESULTS

Baseline LSBMCSDS was >0.5 SDS in 13% children, between -0.5; 0.5 SDS, in 50% and ≤-0.5 in the remainder. Seventy-eight percent of the children who had baseline LSBMCSDS >-0.5, and 35% of the children with poor baseline (LSBMCSDS<-0.5), showed decreasing values in subsequent assessments. However, mean LS BMC SDS did not show a significant decline in subsequent assessments (-0.51; -0.64; -0.56; p=0.178). Lower forced expiratory volume in 1 s percent (FEV1%) low body mass index standard deviation scores (BMI SDS) and vitamin D were associated with reduction in BMC.

CONCLUSIONS

Bone mineral content as assessed by DXA is sub-optimal and decreases with time in most children with CF and this study has highlighted parameters that can be addressed to improve bone health.

Overexpression of RANKL in osteoblasts: a possible mechanism of susceptibility to bone disease in cystic fibrosis

Bone fragility and loss are a significant cause of morbidity in patients with cystic fibrosis (CF), and the lack of effective therapeutic options means that treatment is more often palliative rather than curative. A deeper understanding of the pathogenesis of CF-related bone disease (CFBD) is necessary to develop new therapies. Defective CF transmembrane conductance regulator (CFTR) protein and chronic inflammation in bone are important components of the CFBD development. The receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) drive the regulation of bone turnover. To investigate their roles in CFBD, we evaluated the involvement of defective CFTR in their production level in CF primary human osteoblasts with and without inflammatory stimulation, in the presence or not of pharmacological correctors of the CFTR. No major difference in cell ultrastructure was noted between cultured CF and non-CF osteoblasts, but a delayed bone matrix mineralization was observed in CF osteoblasts. Strikingly, resting CF osteoblasts exhibited strong production of RANKL protein, which was highly localized at the cell membrane and was enhanced in TNF (TNF-α) or IL-17-stimulated conditions. Under TNF stimulation, a defective response in OPG production was observed in CF osteoblasts in contrast to the elevated OPG production of non-CF osteoblasts, leading to an elevated RANKL-to-OPG protein ratio in CF osteoblasts. Pharmacological inhibition of CFTR chloride channel conductance in non-CF osteoblasts replicated both the decreased OPG production and the enhanced RANKL-to-OPG ratio. Interestingly, using CFTR correctors such as C18, we significantly reduced the production of RANKL by CF osteoblasts, in both resting and TNF-stimulated conditions. In conclusion, the overexpression of RANKL and high membranous RANKL localization in osteoblasts are related to defective CFTR, and may worsen bone resorption, leading to bone loss in patients with CF. Targeting osteoblasts with CFTR correctors may represent an effective strategy to treat CFBD. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

[Insights into cystic fibrosis-related bone disease]

With the increasing life expectancy of patients with cystic fibrosis (CF), prevalence of late complications such as CF-related bone disease (CFBD) has increased. It was initially described in 24% of the adult population with CF and has also been reported in the pediatric population. CFBD is multifactorial and progresses in different steps. Both decreased bone formation and increased bone resorption (in different amounts) are observed. CFBD is likely primitive (directly related to the CFTR defect itself), but is also worsened by acquired secondary factors such as lung infections, chronic inflammation, denutrition, vitamin deficiency, and decreased physical activity. CFBD may be clinically apparent (i.e., mainly vertebral and costal fractures), or clinically asymptomatic (therefore corresponding to abnormalities in bone density and architecture). CFBD management mainly aims to prevent the occurrence of fractures. Prevention and regular monitoring of bone disease as early as 8 years of age is of the utmost importance, as is the control of possible secondary deleterious CFBD factors. New radiological tools, such as high-resolution peripheral quantitative computed tomography, allow an accurate evaluation of cortical and trabecular bone micro-architecture in addition to compartmental density; as such, they will likely improve the assessment of the bone fracture threat in CF patients in the near future.

Physiotherapy for cystic fibrosis in Australia and New Zealand: A clinical practice guideline

Physiotherapy management is a key element of care for people with cystic fibrosis (CF) throughout the lifespan. Although considerable evidence exists to support physiotherapy management of CF, there is documented variation in practice. The aim of this guideline is to optimize the physiotherapy management of people with CF in Australia and New Zealand. A systematic review of the literature in key areas of physiotherapy practice for CF was undertaken. Recommendations were formulated based on National Health and Medical Research Council (Australia) guidelines and considered the quality, quantity and level of the evidence; the consistency of the body of evidence; the likely clinical impact; and applicability to physiotherapy practice in Australia and New Zealand. A total of 30 recommendations were made for airway clearance therapy, inhalation therapy, exercise assessment and training, musculoskeletal management, management of urinary incontinence, managing the newly diagnosed patient with CF, delivery of non-invasive ventilation, and physiotherapy management before and after lung transplantation. These recommendations can be used to underpin the provision of evidence-based physiotherapy care to people with CF in Australia and New Zealand.

Bone disease in cystic fibrosis: new pathogenic insights opening novel therapies

Mutations within the gene encoding for the chloride ion channel cystic fibrosis transmembrane conductance regulator (CFTR) results in cystic fibrosis (CF), the most common lethal autosomal recessive genetic disease that causes a number of long-term health problems, as the bone disease. Osteoporosis and increased vertebral fracture risk associated with CF disease are becoming more important as the life expectancy of patients continues to improve. The etiology of low bone density is multifactorial, most probably a combination of inadequate peak bone mass during puberty and increased bone losses in adults. Body mass index, male sex, advanced pulmonary disease, malnutrition and chronic therapies are established additional risk factors for CF-related bone disease (CFBD). Consistently, recent evidence has confirmed that CFTR plays a major role in the osteoprotegerin (OPG) and COX-2 metabolite prostaglandin E2 (PGE2) production, two key regulators in the bone formation and regeneration. Several others mechanisms were also recognized from animal and cell models contributing to malfunctions of osteoblast (cell that form bone) and indirectly of bone-resorpting osteoclasts. Understanding such mechanisms is crucial for the development of therapies in CFBD. Innovative therapeutic approaches using CFTR modulators such as C18 have recently shown in vitro capacity to enhance PGE2 production and normalized the RANKL-to-OPG ratio in human osteoblasts bearing the mutation F508del-CFTR and therefore potential clinical utility in CFBD. This review focuses on the recently identified pathogenic mechanisms leading to CFBD and potential future therapies for treating CFBD.

Vitamin D represses rhinovirus replication in cystic fibrosis cells by inducing LL-37

Vitamin D has immunomodulatory properties in the defence against pathogens. Its insufficiency is a widespread feature of cystic fibrosis (CF) patients, which are repeatedly suffering from rhinovirus (RV)-induced pulmonary exacerbations.To investigate whether vitamin D has antiviral activity, primary bronchial epithelial cells from CF children were pre-treated with vitamin D and infected with RV16. Antiviral and anti-inflammatory activity of vitamin D was assessed. RV and LL-37 levels were measured in bronchoalveolar lavage (BAL) of CF children infected with RV.Vitamin D reduced RV16 load in a dose-dependent manner in CF cells (10(-7 )M, p<0.01). The antiviral response mediated by interferons remained unchanged by vitamin D in CF cells. Vitamin D did not exert anti-inflammatory properties in RV-infected CF cells. Vitamin D increased the expression of the antimicrobial peptide LL-37 up to 17.4-fold (p<0.05). Addition of exogenous LL-37 decreased viral replication by 4.4-fold in CF cells (p<0.05). An inverse correlation between viral load and LL-37 levels in CF BAL (r=-0.48, p<0.05) was observed.RV replication in primary CF bronchial cells was reduced by vitamin D through the induction of LL-37. Clinical studies are needed to determine the importance of an adequate control of vitamin D for prevention of virus-induced pulmonary CF exacerbations.

Evaluation of factors related to bone disease in Polish children and adolescents with cystic fibrosis

PURPOSE

The aim of the study was to evaluate factors related to bone formation and resorption in Polish children and adolescents with cystic fibrosis and to examine the effect of nutritional status, biochemical parameters and clinical status on bone mineral density.

MATERIALS AND METHODS

The study group consisted of 100 children and adolescents with cystic fibrosis with a mean age 13.4 years old. Anthropometric measurements, included body height, body mass and body mass index (BMI); bone mineral densitometry and biochemical testing were performed. Bone mineral density was measured using a dual-energy X-ray absorption densitometer. Biochemical tests included serum calcium, phosphorus, parathyroid hormone and vitamin D concentrations, as well as 24-h urine calcium and phosphorus excretion. Pulmonary function was evaluated using FEV1%, and clinical status was estimated using the Shwachman-Kulczycki score.

RESULTS

Standardized body height, body mass and BMI were significantly lower than in the reference population. Mean serum vitamin D concentration was decreased. Pulmonary disease was generally mild, with a mean FEV1% of 81%. Multivariate linear regression revealed that the only factors that had a significant effect on bone marrow density were BMI and FEV1%. There were no significant correlations between bone mineral density and the results of any of the biochemical tests performed.

CONCLUSIONS

Nutritional status and bone mineral density were significantly decreased in children and adolescents with cystic fibrosis. In spite of abnormalities in biochemical testing, the factors that were found to have the strongest effect on bone mineral density were standardized BMI and clinical status.

Dietary intake and nutritional status of micronutrients in adults with cystic fibrosis in relation to current recommendations

An increased prevalence of cystic fibrosis (CF) related complications such as impaired bone health and diabetes has accompanied increased survival of patients with CF. This review was conducted to determine the extent to which adults with CF are meeting current nutrition recommendations for micronutrients in association with CF-related complications management. Although dietary intake and nutritional status in CF has improved significantly in recent decades, micronutrient status seems to have diverged. While vitamin A and E intakes appear adequate, frequent vitamin D and K deficiency/insufficiency and compromised bone health in CF, occurs despite supplementation. Although deficiency of water-soluble vitamins and minerals is uncommon, ongoing surveillance will enhance overall health outcomes, particularly in cases of CF-related liver disease and deteriorated lung function and bone health. Salt and fluid status in CF may also need attention due to diminished thirst sensation and voluntary rehydration. Further investigation in micronutrient status optimisation in CF will inform the development of more effective and targeted nutrition therapies to enable integration of more refined recommendations for micronutrient intakes in CF based on individual needs and disease progression.

Quantitative bone ultrasound at the distal radius in adults with cystic fibrosis

It is of clinical importance to identify bone disease related to cystic fibrosis (CF) early in its course to allow therapeutic interventions that optimize bone health. To test the technical (precision) and clinical (percentage of abnormal results, correlation with clinical parameters) performance of a commercial quantitative ultrasound apparatus for radial measurements, speed of sound (SOS) was measured at the distal third of the left radius with the Omnisense 7000p apparatus (Sunlight Medical, Tel-Aviv, Israel) in a group of young adult CF patients with regular follow-up at the Brussels and Ghent University Hospital. Sixty-three (37 males) CF patients at a median (range) age of 23.5 y (18.1-39.9) were included. SOS, SOS z-score and SOS t-score were respectively 4017 ± 97 m/s, -0.31 ± 0.74 and -0.60 ± 0.78 in males and 4086 ± 97 m/s, -0.19 ± 0.75 and -0.51 ± 0.95 in females. Mean SOS t-score was significantly lower compared with the manufacturer's reference data for males (p < 0.0001) and females (p = 0.01). SOS z- and t-scores correlated with weight z-score and body mass index z-score in females. No significant correlation was found between SOS and forced expiratory volume in 1 s (%). Neither diabetes mellitus nor liver disease was found to influence SOS. Radial quantitative ultrasound has a precision of 0.55%. The SOS is in the low normal range in 14% of CF patients and is influenced by weight in female patients, but not by the severity of the lung disease.

Bone mineral density, pulmonary function, chronological age, and age at diagnosis in children and adolescents with cystic fibrosis

OBJECTIVE

To assess bone mineral density in patients with cystic fibrosis (CF), and to correlate it with possible intervening variables.

METHODS

Children and adolescents diagnosed with CF, aged 6 to 18 years, followed at the outpatient clinic were included in the study. First, demographic data were collected and, subsequently, patients underwent a spirometric test. All patients answered the Cystic Fibrosis Quality of Life Questionnaire (CFQ) and underwent the six-minute walk test (6MWT) and bone densitometry (DXA).

RESULTS

A total of 25 CF patients were included, of which 56% were males. The mean age was 12.3±3.4 years; mean height was 149.2±14.4 cm; and mean weight was 44.4±13.9 kg. Most results on pulmonary function and bone mineral density (BMD) were within normal limits. The mean forced expiratory volume in one second (FEV) was 92.5±23.6 (% of predicted), mean forced vital capacity (FVC) was 104.4±21.3 (% of predicted), and1 mean BMD z-score was 0.1±1.0. BMD was moderately correlated with FEV (r = 0.43, p = 0.03) and FVC (r = 0.57, p = 0.003). Regarding chronological age and age at diagnosis, a moderate and inverse correlation was also found (r = -0.55, p = 0.004; r = -0.57, p = 0.003, respectively). However, no significant correlations were found with the data from CFQ, 6MWT, and body mass index.

CONCLUSION

Most patients had BMD within normal limits and presented a positive correlation with pulmonary function, as well as a negative correlation with chronological age and age at diagnosis.

The impact of dysglycaemia on bone mineral accrual in young people with cystic fibrosis

OBJECTIVE

The effect of dysglycaemia on bone mineral density (BMD) has not been studied in young people with CF. We examined factors associated with BMD in a tertiary paediatric CF clinic.

DESIGN

Retrospective, clinic-based study at The Children's Hospital at Westmead, Sydney.

PATIENTS

Young people with CF aged ≤ 18 years.

MEASUREMENTS

Bone mineral density was measured by dual-energy X-ray absorptiometry; main outcome measures were total body (TB), lumbar spine (LS) and femoral neck (FN) BMD and bone mineral content (BMC), and LS volumetric BMD (vBMD), reported as z scores for height. Dysglycaemia, based on oral glucose tolerance test, was defined as CF-related diabetes (CFRD) or impaired glucose tolerance (IGT).

RESULTS

Overall, 14 of 81 (17%) had CFRD, 6 (7%) IGT and 61 (76%) normal glucose tolerance (NGT). Mean age was 14.9 ± 2.4 years and mean height z score -0.68 ± 1.39. Osteopenic (z score ≤-2) TB, LS or FN BMD was present in 30 of 81 (37%), BMC in 42 (52%) and vBMD in 10 (5%). Across the three groups, there were differences in LS vBMD (CFRD, -0.67 ± 0.76; IGT, -0.52 ± 0.76; NGT, -0.05 ± 1.39; P = 0.04), LS BMD (P < 0.01), LS BMC (P = 0.01) and TB BMD (P = 0.01). In multivariate linear regression, LS BMC was associated with dysglycaemia (β = 0.56; 95% CI, 0.00-1.13; P = 0.05) and approached significance for FEV(1) (β = 0.01; 95% CI, 0.00-0.02; P = 0.06).

CONCLUSIONS

Dysglycaemia is associated with reduced bone mass accrual in youth with CF, in addition to recognized factors such as abnormal lung function, poor nutritional status and disease severity. Bone health assessment is essential in youth with CF.

Osteoporosis in young adults: pathophysiology, diagnosis, and management

Postmenopausal osteoporosis is mainly caused by increased bone remodeling resulting from estrogen deficiency. Indications for treatment are based on low areal bone mineral density (aBMD, T-score  ≤ -2.5), typical fragility fractures (spine or hip), and more recently, an elevated 10-year fracture probability (by FRAX®). In contrast, there is no clear definition of osteoporosis nor intervention thresholds in younger individuals. Low aBMD in a young adult may reflect a physiologically low peak bone mass, such as in lean but otherwise healthy persons, whereas fractures commonly occur with high-impact trauma, i.e., without bone fragility. Furthermore, low aBMD associated with vitamin D deficiency may be highly prevalent in some regions of the world. Nevertheless, true osteoporosis in the young can occur, which we define as a T-score below -2.5 at spine or hip in association with a chronic disease known to affect bone metabolism. In the absence of secondary causes, the presence of fragility fractures, such as in vertebrae, may point towards genetic or idiopathic osteoporosis. In turn, treatment of the underlying condition may improve bone mass as well. In rare cases, a bone-specific treatment may be indicated, although evidence is scarce for a true benefit on fracture risk. The International Osteoporosis Foundation (IOF) convened a working group to review pathophysiology, diagnosis, and management of osteoporosis in the young, excluding children and adolescents, and provide a screening strategy including laboratory exams for a systematic approach of this condition.

Quantitative Ultrasound in Spanish Children and Young Adults With Cystic Fibrosis

We studied the relationship between bone density and cystic fibrosis in Spanish children and young adults. We measured the phalangeal bone amplitude-dependent speed of sound (Ad-SoS) in 35 patients with cystic fibrosis and in 30 healthy controls matched for gender, age, and body mass index (BMI). Participants were subjects with normal levels of 25(OH) Vitamin D. We found no difference in Ad-SoS between patients and controls. The only difference between the groups was that the patients had a significantly higher daily caloric intake than the controls ( p < .05) as a result of the patient group's greater intake of fats ( p < .05). There was a positive correlation between Ad-SoS and weight ( p < .0001), but after adjusting for potential confounding factors such as age, the correlation was lost. The percentage of ideal weight did not differ between the two groups. We conclude that well-nourished CF patients had similar Ad-SoS to controls.

Vitamin D bioavailability in cystic fibrosis: a cause for concern?

Despite the inclusion of extra vitamin D in their regimen of fat-soluble vitamin supplementation, cystic fibrosis patients remain chronically depleted of vitamin D. The persistence of suboptimal vitamin D status is often blamed on the maldigestion and malabsorption of fat. However, the mitigated success of recent clinical trials with high-dose vitamin D supplementation suggests that vitamin D bioavailability might be impaired in these patients. Given the growing understanding of the importance of this vitamin in the regulation of multiple biological functions beyond skeletal health, the present review analyzes the current literature by addressing each step of vitamin D metabolism and action in the context of this life-limiting pathology. In addition, it highlights the importance of vitamin D in relation to organs and or conditions affected by cystic fibrosis.

Lactose malabsorption is a risk factor for decreased bone mineral density in pancreatic insufficient cystic fibrosis patients

As decreased bone mineral density (BMD) is a common problem in cystic fibrosis (CF) and milk products may have pivotal dietary role affecting BMD, we aimed to assess the potential influence of adult-type hypolactasia (ATH) and lactose malabsorption (LM) on BMD in adolescent and young adult patients. In 95 CF pancreatic-insufficient patients aged 10-25 years (without liver cirrhosis, steatosis and cholestasis, diabetes mellitus, systemic glucocorticoid therapy), lumbar BMD, the nutritional status, pulmonary function, vitamin D3 concentration, calcium intake and single-nucleotide polymorphism upstream of the lactase gene were assessed. In subjects with the -13910 C/C genotype predisposing to ATH, the presence of LM was determined with the use of a hydrogen-methane breath test (BT). BMD and calcium intake were significantly lower in patients with the C/C genotype (P<0.028 and P<0.043, respectively). The abnormal BMD was stated more frequently in patients with the C/C genotype (P<0.042) and with LM (P<0.007). BMD, daily calcium intake and serum vitamin D concentration were significantly lower in LM subjects than in the other patients (P<0.037, P<0.000004 and P<0.0038, respectively). In logistic regression analysis, the relationship between examined parameters and BMD, was found to be statistically significant (P<0.001). However, only standardized body weight and LM were documented to influence BMD (P<0.025 and P<0.044, respectively). In conclusion, LM seems to be an independent risk factor for decreased BMD in CF patients.

A roadmap to the brittle bones of cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disorder which despite advances in medical care continues to be a life-limiting and often fatal disease. With increase in life expectancy of the CF population, bone disease has emerged as a common complication. Unlike the osteoporosis seen in postmenopausal population, bone disease in CF begins at a young age and is associated with significant morbidity due to fractures, kyphosis, increased pain, and decreased lung function. The maintenance of bone health is essential for the CF population during their lives to prevent pain and fractures but also as they approach lung transplantation since severe bone disease can lead to exclusion from lung transplantation. Early recognition, prevention, and treatment are key to maintaining optimal bone health in CF patients and often require a multidisciplinary approach. This article will review the pathophysiology, current clinical practice guidelines, and potential future therapies for treating CF-related bone disease.

Vitamin d deficiency in cystic fibrosis

Cystic Fibrosis is the most common inherited genetic respiratory disorder in the Western World. Hypovitaminosis D is almost universal in CF patients, likely due to a combination of inadequate absorption, impaired metabolism, and lack of sun exposure. Inadequate levels are associated with the high prevalence of bone disease or osteoporosis in CF patients, which is associated with increased morbidity including fractures, kyphosis, and worsening pulmonary status. Treatment goals include regular monitoring 25 hydroxyvitamin D (25OHD) levels with aggressive treatment for those with levels <75 nmol/L (<30 ng/mL). More research is needed to determine optimal supplementation goals and strategies.

Cystic fibrosis transmembrane conductance regulator (CFTR) regulates the production of osteoprotegerin (OPG) and prostaglandin (PG) E2 in human bone

Bone loss is an important clinical issue in patients with cystic fibrosis (CF). Whether the cystic fibrosis transmembrane conductance regulator (CFTR) plays a direct role in bone cell function is yet unknown. In this study, we provide evidence that inhibition of CFTR-Cl(-) channel function results in a significant decrease of osteoprotegerin (OPG) secretion accompanied with a concomitant increase of prostaglandin (PG) E(2) secretion of primary human osteoblast cultures (n=5). Our data therefore suggest that in bone cells of CF patients, the loss of CFTR activity may result in an increased inflammation-driven bone resorption (through both the reduced OPG and increased PGE(2) production), and thus might contribute to the early bone loss reported in young children with CF.

'Old' bones in young bodies: the tale of cystic fibrosis

PURPOSE OF REVIEW

Cystic fibrosis (CF) is the most common genetic disease within the white population and leads to premature respiratory failure. Approximately, 60 000 individuals are currently living with CF in North America and Europe, almost half of whom are adults.

RECENT FINDINGS

Dozens of studies across the globe indicate that CF adults have low bone density and increased rates of fractures. This genesis of the problem appears to be in late childhood to adolescence.

SUMMARY

Prevention and treatment of CF-related bone disease must address the myriad risk factors (decreased absorption of fat-soluble vitamins due to pancreatic insufficiency, altered sex hormone production, chronic lung infection with increased serum levels of proinflammatory, bone-active cytokines, malnutrition and low body weight, physical inactivity and glucocorticoid therapy) for poor bone health. This review will address the pathogenesis, diagnosis and treatment of bone disease in CF. It will also discuss best practice guidelines for optimizing bone health in patients with CF.