From the Journals

Cathepsin Z identified as a potential biomarker for osteoporosis



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 Scientific Reports.

Dong L. Barraclough, PhD, 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. doi: 10.1038/s41598-019-46068-0.

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