High phosphate intake induces bone loss in nephrectomized thalassemic mice

Area of Science:

• Bone Biology
• Nephrology
• Hematology

Background:

• Patients with beta-thalassemia or chronic kidney disease (CKD) often experience severe osteoporosis.
• The specific mechanisms linking CKD, high phosphate intake, and bone turnover in beta-thalassemia remain unclear.

Purpose of the Study:

• To investigate the impact of renal insufficiency on high phosphate-induced bone metabolism changes in beta-thalassemia mice.
• To characterize the effects of 5/6th nephrectomy and high phosphate intake on bone turnover in hemizygous beta-globin knockout (BKO) mice.

Main Methods:

• Hemizygous BKO mice and wild-type (WT) littermates underwent 5/6th nephrectomy.
• Post-nephrectomy, mice received either regular water or phosphate-buffered saline (PBS) in drinking water.
• Bone metabolism was assessed via histomorphometry, serum analysis (urea nitrogen, calcium, FGF23, erythropoietin, PTH), and gene expression analysis.

Main Results:

• Nephrectomy in WT mice increased bone turnover and bone loss; BKO mice showed anemia and osteopenia initially.
• In nephrectomized BKO mice, PBS induced hyperphosphatemia, hypercalcemia, and osteopenia in both cancellous and cortical bone.
• Reduced bone formation, decreased osteoblast and osteoclast numbers, and altered gene expression were observed. Serum FGF23, erythropoietin, and PTH levels were elevated in response to hyperphosphatemia.

Conclusions:

• Renal insufficiency combined with high phosphate intake exacerbates bone loss in beta-thalassemia mice.
• Elevated FGF23, erythropoietin, and PTH likely mediate bone loss in thalassemic mice with CKD and phosphate retention.
• These findings highlight potential therapeutic targets for managing bone disease in beta-thalassemia patients with CKD.