The presence of cathepsin Z messenger RNA in peripheral blood mononuclear cells of people with osteopenia, osteoporosis, and women with osteoporosis and older than 50 years could be used as a biomarker to help diagnose osteoporosis, according to a recent study published in.
of the Institute of Ageing and Chronic Disease at the University of Liverpool, England, and colleagues studied the expression of cathepsin Z messenger RNA (mRNA) in peripheral blood mononuclear cells (PBMCs) of 88 participants (71 women, 17 men). The participants were grouped according to their bone mineral density and T score, where a T score of −1.0 or higher was considered nonosteoporotic, a score between −1.0 and −2.5 was classified as osteopenia, and −2.5 or less was classified as osteoporosis.
Overall, there were 48 participants with osteopenia (38 women, 10 men; 55% of total participants; average age, 65 years), 23 participants with osteoporosis (19 women, 4 men; 26%; 69 years), and 17 participants in the nonosteoporotic control group (14 women, 3 men; 19%; 56 years), with 88% of the total number of participants aged 50 years and older (82% women, 18% men).
The researchers found significantly higher differential expression of cathepsin Z mRNA in PBMCs when comparing the nonosteoporotic control group and participants with osteopenia (95% confidence interval, −0.32 to −0.053; P = .0067), the control group with participants with osteoporosis (95% CI, −0.543 to −0.24; P less than .0001), and participants with osteopenia and those with osteoporosis (95% CI, −0.325 to −0.084; P = .0011).
That association also was seen in women with osteoporosis who were older than 50 years (P = .0016) and did not change when participants were excluded for receiving treatment for osteoporosis, the authors wrote.
There also was an inverse association between cathepsin Z mRNA levels and bone mineral density (P = .0149) as well as inversely associated with lumbar spine L2-L4 and femoral neck T-scores (P = .0002 and P = .0139, respectively) and fragility fracture (P = .0018) in participants with osteopenia, osteoporosis, and women with osteoporosis older than 50 years.
Patients with chronic inflammatory disease sometimes have “osteoporosis-like conditions,” the authors noted. “However, there was no significant difference in cathepsin Z mRNA levels between osteopenia and osteoporosis patients who were also suffering from chronic inflammatory disorders and those [who] were not,” either when all osteopenia and osteoporosis participants were included (P = .774), or when only women participants with osteopenia or osteoporosis and older than 50 years were included (P = .666).
“The observation that [participants] with osteopenia also showed a significant increase in cathepsin Z mRNA, compared [with] nonosteoporotic controls, strongly suggests that, if replicated in a larger study, the cathepsin Z mRNA in patients’ PBMC preparations could form the basis of a test for osteoporosis, which could aid in the detection of osteoporosis before a critical and expensive fragility fracture occurs,” the authors wrote.
The authors reported no relevant conflicts of interest.
SOURCE: Dera AA et al. Sci Rep. 2019 Jul 5. .