Elevated Levels of Peripheral Kynurenine Decrease Bone Strength in Rats with Chronic Kidney Disease.

Area of Science:

• Nephrology and Bone Metabolism
• Biochemistry and Molecular Biology

Background:

• Chronic kidney disease (CKD) is associated with early mineral and bone complications.
• Previous studies indicated a link between central kynurenine turnover and bone strength in CKD rats.

Purpose of the Study:

• To investigate the association between peripheral kynurenine pathway metabolites and bone strength in a rat model of CKD.
• To explore the role of the aryl hydrocarbon receptor (AhR) pathway in CKD-induced bone alterations.

Main Methods:

• Subtotal 5/6 nephrectomy (5/6 Nx) or sham operation in rats.
• Measurement of serum creatinine, urea nitrogen, parathyroid hormone, and kynurenine metabolites.
• Analysis of aryl hydrocarbon receptor (AhR) gene expression in bone tissue.
• Assessment of osteoclast number and resorptive activity.
• Evaluation of bone biomechanical, geometrical, and microarchitectural parameters.

Main Results:

• Nephrectomized rats exhibited elevated serum creatinine, urea nitrogen, parathyroid hormone, kynurenine, and 3-hydroxykynurenine.
• Increased aryl hydrocarbon receptor (AhR) gene expression and osteoclast number were observed in nephrectomized rats.
• Peripheral kynurenine levels correlated negatively with bone biomechanical, geometrical, and bone mineral density parameters.

Conclusions:

• Elevated peripheral kynurenine levels in CKD contribute to pathological bone structure changes through the AhR pathway.
• These findings highlight potential therapeutic strategies for preventing and treating osteoporosis in CKD patients.