Changes in bone turnover markers and bone modulators during abatacept treatment

Area of Science:

• Rheumatology
• Bone Metabolism
• Immunology

Background:

• Rheumatoid arthritis (RA) is associated with bone loss not solely explained by inflammation.
• The effects of RA treatments on bone metabolism and their capacity to prevent bone loss require further investigation.

Purpose of the Study:

• To assess abatacept's influence on serum markers and regulators of bone turnover in RA patients.
• To evaluate changes in bone mineral density (BMD), bone health parameters, and erosions.
• To explore correlations between bone metabolism markers and clinical outcomes.

Main Methods:

• Prospective observational study of 33 active seropositive RA patients failing prior biologic therapy, initiating abatacept.
• Regular monitoring of serum bone turnover markers (CTX, P1nP, B-ALP), bone modulators (Dkk-1, sclerostin, vitamin D, PTH, OPG, RANKL), BMD, and radiographic scores (mSvdH, BHI, MCI) over 12 months.
• Assessment of disease activity and glucocorticoid use.

Main Results:

• Significant increases in bone formation markers (B-ALP, P1nP) observed at 6 and 12 months.
• Transient increase in parathyroid hormone (PTH) at 6 months, but not sustained at 12 months.
• Significant decrease in bone health index (BHI) and metacarpal index (MCI) over 12 months; transient BMD decrease at the femoral neck at 6 months.
• Correlation found between P1nP changes and mSvdH score changes at 12 months.

Conclusions:

• Abatacept treatment in RA patients is linked to increased bone formation markers.
• Transient bone loss observed may be associated with a temporary rise in PTH levels.
• Further studies are warranted to elucidate the complex relationship between abatacept, bone metabolism, and bone health in RA.