Collagen turnover in bone diseases.

Abstract

The primary aim of this review is to highlight recent advances in techniques available for assessing collagen turnover, particularly in relation to the diagnosis and management of bone disorders. As collagen is the major protein constituent of bone, its metabolites form the basis of most of the biochemical markers, but their efficacy needs to be viewed in the context of other non-collagenous markers, for which methodology is also advancing rapidly. New markers of bone metabolism have been developed utilising the age-dependent isomerisation and racemisation of aspartyl residues at the C-terminal end of collagen. These methods allow measurement of the ratio between newly synthesised and mature collagen: this ratio appears to provide a novel indicator of the fracture risk for osteoporosis. Other studies have led to an improved understanding of biological variability, particularly in relation to the effects of feeding. Bone resorption assays have been applied to a wide range of diseases and have been especially useful in monitoring the efficacy of novel therapies. New assays have been developed to facilitate better monitoring of collagen metabolism in bone diseases. A more complete understanding of biological variability, particularly the effects of feeding, have led to improved clinical applicability of these assays in detecting disease and monitoring therapy. Part of the future challenge, however, is to ensure that commercial assay developments keep pace with clinical expectations.