Serum cathepsin K as a marker of bone metabolism in postmenopausal women treated with alendronate.
BACKGROUND
Cathepsin K is a member of the cysteine protease family that cleaves both helical and telopeptide regions of collagen I, the major type of collagen in bone. Measurement of circulating levels of cathepsin K may be useful to assay the number or function of osteoclasts.


OBJECTIVE
The aim of the study was to evaluate the role of serum cathepsin K as a biochemical marker of bone metabolism in patients with postmenopausal osteoporosis before and after treatment with alendronate.


METHODS
The study was a case-control and prospective study with postmenopausal osteoporotic women including a total number of 86 subjects. Serum cathepsin K was determined in 46 women with postmenopausal osteoporosis before and after 3, 6 and 12 months of treatment with alendronate. Basal serum cathepsin K levels were also compared between premenopausal healthy women (n=20), postmenopausal women without osteoporosis (n=20) and osteoporotic women. In addition, serum carboxyterminal cross-linked telopeptide of type I collagen (CTX), osteocalcin (OC) and bone-specific alkaline phosphatase (bALP) were measured.


METHODS
Changes in cathepsin K serum levels after alendronate treatment.


RESULTS
Serum cathepsin K levels were higher in postmenopausal women with osteoporosis (9.4+/-11pmol/L) compared with healthy postmenopausal women (6.8+/-8.1pmol/L; p<0.01) and premenopausal women (6.3+/-5.0pmol/L, p<0.01). Serum cathepsin K decreases gradually after alendronate treatment (17% at 3 months, 22% at 6 months and 41% at 12 months, p<0.01). In contrast, the treatment resulted in early and sustained reductions in serum CTX.


CONCLUSIONS
We conclude that serum cathepsin K seems to provide additional information on bone metabolism in postmenopausal women treated with alendronate.
Muñoz-Torres
Manuel
M
Bone Metabolic Unit, Endocrinology Division, University Hospital San Cecilio, Granada, Spain. mmt@ssash.com
Reyes-García
Rebeca
R
Mezquita-Raya
Pedro
P
Fernández-García
Diego
D
Alonso
Guillermo
G
Luna
Juan de Dios
Jde D
Ruiz-Requena
María Estrella
ME
Escobar-Jiménez
Fernando
F
D000328:Adult; D000368:Aged; D019386:Alendronate / Q000627:therapeutic use*; D015415:Biomarkers / Q000097:blood; D050071:Bone Density Conservation Agents / Q000627:therapeutic use*; D001842:Bone and Bones / Q000378:metabolism*; D016022:Case-Control Studies; D056657:Cathepsin K / Q000097:blood*; D024042:Collagen Type I / Q000097:blood; D005260:Female; D006801:Humans; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000097:blood* / Q000378:metabolism; D017698:Postmenopause / Q000097:blood; D017697:Premenopause / Q000097:blood; D012016:Reference Values; D055815:Young Adult
D015415:Biomarkers; D050071:Bone Density Conservation Agents; D024042:Collagen Type I; D056657:Cathepsin K; D019386:Alendronate