Circulating levels of a protein biomarker predicts the risk of postmenopausal women having a low-trauma fracture independent of their areal bone-mineral density (aBMD) status, classical bone-turnover markers (BTMs) and Fracture Risk Assessment Tool (FRAX) score, new research shows.
The study was published online August 2 in the Journal of Bone and Mineral Research.
Nicolas Bonnet, PhD, and colleagues from Geneva University Hospital, Switzerland, evaluated the potential of circulating K-Postn to predict low-trauma fracture risk in 695 postmenopausal women, aged 65 years at baseline and enrolled in the Geneva Retirees Cohort (GERICO).
After 4.7 years of follow-up, 9.4% of the cohort had experienced either a vertebral or nonvertebral fracture.
“As expected, the fracture group had a lower aBMD and a higher fracture probability at baseline assessed by FRAX,” researchers write.
In addition, baseline K-Postn levels were 36% higher in participants who went on to develop a low-trauma fracture compared with women who did not experience a fracture (P < .001).
The K-Postn biomarker is a fragment of the periostin protein, which is thought to contribute to bone strength through multiple pathways. When periostin is cleaved by the cathepsin K, an enzyme mostly expressed by osteoclasts and osteocytes, it releases the K-Postn fragment.
“Because cathepsin K is an enzyme relatively specific to the bone tissue, the amount of this fragment in the circulation could better reflect bone metabolism” compared with traditional BTMs, the researchers explain.
Consistent with that hypothesis, neither β-carboxyterminal cross-linked telopeptide of type I collagen (CTX), a classical bone turnover marker, nor total periostin were predictive of subsequent low-trauma fracture risk in the GERICO cohort, the authors report.
Baseline Measures of Fracture Risk
| Measure | Fracture (n=66) | No fracture (n=629) | P |
|---|---|---|---|
| Lumber spine BMD (g/c2) | 0.97 | 1.07 | <0.001 |
| Femoral neck BMD | 0.68 | 0.71 | 0.01 |
| Total hip BMD | 0.82 | 0.855 | 0.03 |
| FRAX score | 15.1 | 11.8 | <0.001 |
| K-Postn (ng/mL) | 57.5 | 42.5 | <0.001 |
Increased Fracture Risk
Furthermore, for each standard-deviation increment in circulating K-Postn levels, fracture risk increased by 114%. “This association remained significant after adjustment for femoral neck BMD, FRAX, or CTX,” researchers state.
Researchers also found that the same biochemical fragment could predict future fracture risk in women with and without osteoporosis, as well as in women with osteopenia, as defined by BMD levels.
“This prospective study conducted in a homogeneous cohort of 65-year-old community-dwelling women shows that K-Postn is a predictor of incident low-trauma fractures, independently of BMD, FRAX, and classical BTMs,” investigators conclude.
The authors also note that when K-Postn is added to a predictive model with FRAX with BMD or femoral-neck BMD, the predictive accuracy increases relative to any of the measures used alone.
The authors had no relevant financial relationships.
J Bone Miner Res. Published online August 2, 2017. Article
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