Changes in urinary excretion of helical peptide during therapy for osteoporosis in older adults.

Abstract

Bone is a dynamic tissue that is constantly undergoing remodeling or turnover, a requirement for maintenance of bone health. Our group and others have shown the usefulness of biochemical markers of bone turnover, specifically those that reflect bone resorption, in the evaluation of metabolic bone disease and the determination of response to treatment in the clinical as well as research setting (1)(2)(3). Measurement of the degradation products of bone reflect the rate of bone turnover (2). Type 1 collagen, a triple helical molecule composed of two α1 chains and one α2 chain with cross-linking at the N- and C-telopeptides, comprises 90% of the organic matrix of bone (3). Degradation products of this molecule have been the most useful markers of bone resorption. During resorption of bone, type 1 collagen is cleaved by proteinases in both the helical and telopeptide regions. Initially markers were based on measurement of breakdown products of the cross-linked telopeptide region. Recently, a peptide consisting of residues 620–633 derived from the helical region of the α1 chain of type 1 collagen was isolated from the urine of patients with Paget disease of bone, and a competitive enzyme immunoassay for this peptide was developed (4)(5). We compared the changes in this new marker with changes in existing urinary markers, including N-telopeptide collagen cross-links (NTx), C-telopeptide collagen cross-links (CTx), and free deoxypyridinoline (DPD), from three different intervention studies in older men and women with osteoporosis. We studied participants in three separate osteoporosis studies, each approved by the Institutional Review Board. Informed consent was obtained from each volunteer. Exclusion criteria were diseases known to affect bone metabolism; use of estrogen, androgens, corticosteroids, heparin, anticonvulsants, vitamin D (other than multivitamin), or calcitonin currently or in the past year; past or present use of bisphosphonates …