Effects of TNF Inhibitors on Parathyroid Hormone and Wnt Signaling Antagonists in Rheumatoid Arthritis

Area of Science:

• Rheumatology
• Endocrinology
• Bone Metabolism

Background:

• Rheumatoid arthritis (RA) significantly impacts bone health, leading to systemic and local bone damage.
• While Tumor Necrosis Factor α inhibitors (TNFi) are effective for RA inflammation, their effects on bone metabolism pathways, specifically parathyroid hormone (PTH) and Wnt signaling, remain unclear.
• The Wnt/βcatenin pathway and PTH are crucial in RA pathogenesis and bone damage.

Purpose of the Study:

• To investigate the short-term effects of TNFi therapy on key bone metabolism factors in RA patients.
• To examine changes in serum levels of Wnt pathway inhibitors (Dkk1, Sclerostin), PTH, vitamin D, and bone turnover markers following TNFi initiation.

Main Methods:

• A cohort of 54 RA patients initiating TNFi therapy after conventional drug failure was studied.
• Serum levels of Dkk1, Sclerostin, PTH, vitamin D, and bone turnover markers were measured at baseline and after 6 months of TNFi treatment.
• Statistical analysis was performed to assess changes and correlations between measured parameters.

Main Results:

• A significant increase in serum PTH levels (+32%) and a decrease in Dkk1 serum levels were observed after 6 months of TNFi therapy (p=0.002 and p=0.05, respectively).
• PTH changes positively correlated with changes in C-terminal telopeptide of type I collagen and Dkk1 levels.
• No significant changes were found in Sclerostin serum levels.

Conclusions:

• Short-term TNFi treatment in RA patients leads to increased PTH and decreased Dkk1 serum levels.
• The observed increase in PTH may contribute to bone resorption and counteract potential benefits of Dkk1 modulation.
• These findings offer new insights into the metabolic effects of TNFi on bone, suggesting potential strategies for preventing bone erosion and osteoporosis in RA.