Serum galactosyl hydroxylysine as a biochemical marker of bone resorption.
BACKGROUND
Serum-based biochemical markers of bone resorption may provide better clinical information than urinary markers because direct comparison with serum markers of bone formation is possible and because the within-subject variability of serum markers may be lower. We describe a method for the measurement of free beta-1-galactosyl-O-hydroxylysine (Gal-Hyl) in serum.


METHODS
The assay used preliminary ultrafiltration of serum, dansylation, and separation by reversed-phase HPLC with fluorescence detection. Healthy subjects were recruited from population-based studies of bone turnover.


RESULTS
The within-run (n = 15) and between-run (n = 15) CVs were 7% and 14%, respectively, at a mean value of 48 nmol/L. In women and pubertal girls, serum free Gal-Hyl correlated with urine free Gal-Hyl (r = 0.84; P <0.001). Serum Gal-Hyl was higher during puberty and increased after menopause. The fractional renal clearance of free Gal-Hyl relative to that of creatinine was 0.90 (95% confidence interval, 0.82-0.98). Serum free Gal-Hyl decreased by 36% (SE = 4%) in 14 patients with mild Paget disease treated with an oral bisphosphonate, and this decrease was significantly (P <0. 001) greater than that seen for either serum tartrate-resistant acid phosphatase (9%; SE = 4%) or serum C-terminal telopeptide of collagen I (19%; SE = 8%).


CONCLUSIONS
Serum free Gal-Hyl may be useful as a serum marker of bone resorption.
Al-Dehaimi
A W
AW
Address correspondence to this author at: Clinical Sciences Centre, Northern General Hospital, Herries Road, Sheffield S5 7AU, UK. Fax 44-0114-261-8775, USA.
Blumsohn
A
A
Eastell
R
R
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001862:Bone Resorption / Q000097:blood* / Q000652:urine; D002648:Child; D004164:Diphosphonates / Q000627:therapeutic use; D005260:Female; D006801:Humans; D006901:Hydroxylysine / Q000031:analogs & derivatives* / Q000097:blood / Q000652:urine; D008593:Menopause; D008875:Middle Aged; D010001:Osteitis Deformans / Q000188:drug therapy / Q000652:urine; D011627:Puberty
D015415:Biomarkers; D004164:Diphosphonates; D006901:Hydroxylysine; C007817:galactosylhydroxylysine