Analysis of bone mineral density and turnover in patients with cystic fibrosis: associations between the IGF system and inflammatory cytokines.
BACKGROUND
Cystic fibrosis (CF) patients present an increased risk of osteoporosis, and increased fracture rate. Several factors have been identified as modulators of bone metabolism and bone mineral density (BMD).


OBJECTIVE
To evaluate BMD and serum markers of bone turnover and establish their relationships with serum concentrations of interleukin (IL)-1beta, IL-6, tumour necrosis factor (TNF)-alpha, IGF-I, IGF-II, IGF binding protein (IGFBP)-2, IGFBP-3, and parathyroid hormone (PTH) in young adult CF patients.


METHODS
Seventeen young adult CF patients (4 M, 13 F; mean age: 26.6 +/- 1.1 years) were enrolled in the study and analysed as a whole and as two subgroups according to the Shwachman-Kulczycki score. BMD was assessed at the lumbar spine (L1-L4) by dual energy X-ray absorptiometry (DXA Hologic QDR 2000). Bone turnover was assessed by measuring serum levels of osteocalcin (OC) and serum carboxyterminal propeptide of type I collagen (PICP) as markers of bone formation, and serum cross-linked carboxyterminal telopeptide of type I collagen (ICTP) as a marker of bone resorption. Serum IGFs, IGFBPs, and cytokines were assayed using special commercial kits. Daily calcium intake and weekly physical activity were estimated by questionnaires. Forced expiratory volume in one second was used to assess pulmonary function.


RESULTS
Lumbar BMD was normal, although there was a tendency to be lower in the patients with a lower clinical score. Both OC and PICP were increased, whereas ICTP was normal. Lumbar BMD was positively correlated with pulmonary function. IL-6 and C-reactive protein (markers of inflammation) were inversely correlated with PICP. Serum ICTP levels were correlated with serum IGF-I levels. No significant relationship was detected among lumbar BMD, markers of bone turnover and PTH, IGF-I, IGF-II, IGFBP-2, IGFBP-3, TNF-alpha, IL-1beta, and body mass index Z-score.


CONCLUSIONS
Bone turnover is abnormal in CF patients. Young adult CF patients with satisfying clinical status and nutritional conditions have normal BMD and increased serum OC and PICP levels.
Street
Maria E
ME
Department of Pediatrics, University of Parma, Parma, Italy. mariaelisabeth.street@unipr.it
Spaggiari
Cinzia
C
Ziveri
Maria A
MA
Volta
Cecilia
C
Federico
Giovanni
G
Baroncelli
Giampiero I
GI
Bernasconi
Sergio
S
Saggese
Giuseppe
G
D000328:Adult; D015415:Biomarkers; D015519:Bone Density; D016723:Bone Remodeling; D002118:Calcium / Q000008:administration & dosage / Q000502:physiology; D003550:Cystic Fibrosis / Q000097:blood* / Q000453:epidemiology*; D016207:Cytokines / Q000097:blood*; D004435:Eating / Q000502:physiology; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007335:Insulin-Like Growth Factor II / Q000032:analysis; D008297:Male; D009043:Motor Activity / Q000502:physiology; D010281:Parathyroid Hormone / Q000097:blood; D013002:Somatomedins / Q000032:analysis*; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
D015415:Biomarkers; D016207:Cytokines; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; C470125:PTH protein, human; D010281:Parathyroid Hormone; D013002:Somatomedins; C439524:TNF protein, human; D014409:Tumor Necrosis Factor-alpha; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D002118:Calcium