Elevated Serum Dickkopf-1 Is a Biomarker for Bone Erosion in Patients With Psoriatic Arthritis

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Elevated Serum Dickkopf-1 Is a Biomarker for Bone Erosion in Patients With Psoriatic Arthritis

Psoriatic arthritis (PsA) is a complex autoimmune disease that combines skin psoriasis with joint inflammation—affecting up to 30% of people with psoriasis. For many, its most devastating feature is bone erosion: progressive joint damage that can lead to disability. But until now, doctors have lacked reliable blood markers to predict or track this erosion. A 2021 study from Peking University People’s Hospital offers new hope: elevated levels of a protein called Dickkopf-1 (Dkk-1) may signal a higher risk of bone damage in PsA patients.

What Is Dkk-1—and Why Does It Matter for Bone Health?

To understand Dkk-1’s role, let’s break down bone biology. Our bones are in constant flux: osteoblasts build new bone, while osteoclasts break it down. A pathway called Wnt/β-catenin keeps this balance in check—promoting osteoblasts and limiting osteoclasts. Dkk-1 is a natural brake on this pathway: too much Dkk-1 blocks Wnt/β-catenin, reducing bone-building cells and tipping the scale toward erosion.

In rheumatoid arthritis (RA), high Dkk-1 levels are linked to worse bone damage. But its role in PsA—where patients can have both erosion and abnormal new bone growth—was unclear. That’s where this study stepped in.

The Study: Who, How, and What They Found

Led by Yukchiu Chung, Zhi-Chang Li, and colleagues from the Department of Rheumatology and Immunology at Peking University People’s Hospital, the research included:

  • 69 PsA patients (meeting CASPAR criteria for PsA)
  • 39 rheumatoid arthritis (RA) patients (meeting 1987 ACR criteria)
  • 21 healthy controls

Researchers measured serum Dkk-1 levels using an enzyme-linked immunosorbent assay (ELISA) and analyzed data on:

  • Clinical symptoms (swollen joints, dactylitis, enthesitis)
  • Lab values (inflammatory markers, complement proteins like C3/C4)
  • Radiographic damage (X-rays scored for erosion, sacroiliitis, and axial disease)

Key Results

  1. Dkk-1 Is Elevated in PsA: 68.1% of PsA patients had high Dkk-1 levels—far more than RA patients (46.2%) or healthy people (9.5%). PsA patients’ average Dkk-1 level (9.27 ng/mL) was significantly higher than both RA (7.86 ng/mL) and healthy controls (6.25 ng/mL).
  2. Dkk-1 Links to Worse Symptoms: Patients with elevated Dkk-1 had more swollen joints (4 vs. 1 on average) and lower levels of C3 (a complement protein that helps fight infection).
  3. Dkk-1 Predicts Bone Erosion: The biggest finding? PsA patients with high Dkk-1 were 4.4 times more likely to have bone erosion than those with normal levels. They also had more sacroiliitis (inflammation of the lower back joints) and axial disease (spine involvement)—affecting 57.4% vs. 22.7% of those with normal Dkk-1.
  4. Dkk-1 Correlates With Radiographic Damage: The “Sharp score” (a measure of joint damage) was twice as high in patients with elevated Dkk-1 (9 vs. 3).

Why This Matters for PsA Patients

PsA is often called a “chameleon” disease because it can present in so many ways—from peripheral joint pain to spine inflammation. This study suggests Dkk-1 could help doctors:

  • Identify high-risk patients: Elevated Dkk-1 may flag those more likely to develop bone erosion, enabling earlier intervention.
  • Track disease severity: Dkk-1 levels could complement X-rays to monitor progression, especially in axial PsA (where spine damage is common).
  • Target treatments: Since Dkk-1 blocks bone-building pathways, therapies that lower Dkk-1 (like anti-TNF drugs or Wnt pathway modulators) might slow erosion.

Addressing Conflicting Findings

Some past studies (like one from Fassio et al. in 2017) found lower Dkk-1 levels in PsA. The Peking University team explains this discrepancy by phenotype: 55% of their PsA patients had axial arthritis (spine involvement), which is linked to higher Dkk-1. This suggests Dkk-1 levels vary by PsA subtype—something future research should explore.

Limitations to Keep in Mind

The study has caveats:

  • Small sample size: Only 69 PsA patients, all from one hospital.
  • Retrospective design: Missing long-term data on how Dkk-1 levels change over time.
  • Phenotype differences: Not all PsA patients have axial disease, so results may not apply to everyone.

What’s Next?

This research adds Dkk-1 to the list of promising biomarkers for PsA—joining proteins like MMP-3 (matrix metalloproteinase-3) and RANKL (receptor activator of nuclear factor kappa-B ligand). But larger, multicenter studies are needed to confirm its role and see if it works as a predictive tool.

For patients, the takeaway is hopeful: We’re one step closer to stopping PsA’s most destructive effects before they start.

Yukchiu Chung, Zhi-Chang Li, Xiao-Lin Sun, Yan-Ying Liu, Miao Shao, Yu-Zhou Gan, Yi-Min Li, Yu-Hui Li, Xue-Wu Zhang. Elevated serum Dickkopf-1 is a biomarker for bone erosion in patients with psoriatic arthritis. Chinese Medical Journal 2021;134(21):2583–2588. doi.org/10.1097/CM9.0000000000001612

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