Undercarboxylated osteocalcin and bone mass in 8-12 year old children with cystic fibrosis.
Young adults with cystic fibrosis (CF) frequently develop bone disease. One suggested aetiological factor is suboptimal vitamin K status with impaired carboxylation of osteocalcin and abnormal bone formation.


METHODS
We measured bone mineralization and turnover in thirty-two 8-12 year old CF patients (14 boys) using Dual Energy X-ray absorptiometry (whole body (WB) and lumbar spine (LS)), 25-OH Vitamin D, PTH and markers of bone formation (plasma osteocalcin, N-terminal pro-peptide of type 1 collagen (P1NP)), plus an indirect measure of vitamin K status, undercarboxylated osteocalcin (uc-OC).


RESULTS
LS bone mineral density (BMD) standard deviation (SD) scores were < -1.0 in 20% of subjects. Size-adjusted LS and WB bone mass was normal. Compared to reference data, % uc-OC was high and P1NP low. LS bone mass was predicted by % uc-OC but not other markers (0.4% decrease in size-adjusted LSBMC (p=0.05); 0.04 SD decrease in LSBMAD (p=0.04) per 1% increase in uc-OC).


CONCLUSIONS
Markers suggestive of sub-optimal vitamin K status and low bone formation were present despite normal size-adjusted bone mass. The association between LSBMC and % uc-OC is consistent with the hypothesis that sub-optimal vitamin K status is a risk factor for CF bone disease. This should ideally be investigated in an intervention trial.
Fewtrell
M S
MS
MRC Childhood Nutrition Research Centre, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK. Electronic address: m.fewtrell@ich.ucl.ac.uk.
Benden
C
C
Portex Respiratory Medicine Unit, Great Ormond Street Hospital for Children National Health Service Trust, London WC1N 1EH, UK.
Williams
J E
JE
MRC Childhood Nutrition Research Centre, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.
Chomtho
S
S
MRC Childhood Nutrition Research Centre, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.
Ginty
F
F
Portex Respiratory Medicine Unit, Great Ormond Street Hospital for Children National Health Service Trust, London WC1N 1EH, UK.
Nigdikar
S V
SV
MRC Human Nutrition Research, Elsie Widdowson Laboratory, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK.
Jaffe
A
A
Portex Respiratory Medicine Unit, Great Ormond Street Hospital for Children National Health Service Trust, London WC1N 1EH, UK.
D015652:25-Hydroxyvitamin D 2 / Q000097:blood; D015502:Absorptiometry, Photon; D015519:Bone Density; D016723:Bone Remodeling / Q000502:physiology; D002648:Child; D015331:Cohort Studies; D003550:Cystic Fibrosis / Q000150:complications*; D005260:Female; D006801:Humans; D008297:Male; D015675:Osteocalcin / Q000097:blood* / Q000737:chemistry; D010024:Osteoporosis / Q000209:etiology*; D010281:Parathyroid Hormone / Q000097:blood; D014813:Vitamin K Deficiency / Q000150:complications*
D010281:Parathyroid Hormone; D015675:Osteocalcin; D015652:25-Hydroxyvitamin D 2