Osteoporosis, one of the most prevalent chronic ageing-related
bone diseases, often goes undetected until the first fragility fracture occurs, causing patient suffering and cost to health/social care services.
Osteoporosis arises from imbalanced activity of osteoclasts and osteoblasts. Since these cell lineages produce the
protease,
cathepsin Z, the aim of this study was to investigate whether altered
cathepsin Z mRNA levels are associated with
osteoporosis in clinical samples.
Cathepsin Z mRNA in human peripheral blood mononuclear cells was significantly differentially-expressed among non-osteoporotic controls,
osteopenia and
osteoporosis patients (p < 0.0001) and in female
osteoporosis patients over the age of 50 years (P = 0.0016).
Cathepsin Z mRNA level strongly correlated with
low bone mineral density (BMD) (g/cm2), lumbar spine L2-L4 and femoral neck (T-scores) (P = 0.0149, 0.0002 and 0.0139, respectively). Importantly,
cathepsin Z mRNA was significantly associated with fragility fracture in
osteoporosis patients (P = 0.0018). The levels of
cathepsin Z mRNA were not significantly higher in patients with chronic inflammatory disorders in these two groups compared to those without (P = 0.774 and 0.666, respectively). ROC analysis showed that
cathepsin Z mRNA has strong diagnostic value for
osteoporosis and
osteoporotic fracture. The results show for the first time that
cathepsin Z could be a future diagnostic
biomarker for
osteoporosis including female
osteoporosis patients over the age of 50 years.