Association Between Indoxyl Sulfate and Skeletal Resistance in Hemodialysis Patients

Skeletal resistance to parathyroid hormone (PTH) in uremia is known, although the mechanism of resistance is not fully elucidated. To clarify the roles of indoxyl sulfate, which is a uremic toxin, in skeletal resistance, we examined the relationship between indoxyl sulfate and biochemical markers of bone turnover in hemodialysis patients. We obtained blood samples from 47 hemodialysis patients and measured serum indoxyl sulfate, intact PTH, oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG), and various biochemical markers. The serum concentrations of alkaline phosphatase (ALP) and bone-specific alkaline phosphatase (BAP) were used as bone formation markers, and the concentration of tartrate-resistant acid phosphatase 5b (TRACP-5b) was used as a bone resorption marker. Serum indoxyl sulfate levels were much higher in hemodialysis patients than healthy subjects. Multiple regression analysis shows that indoxyl sulfate correlated negatively with ALP (beta = -1.897, P = 0.042) and BAP (beta = -0.310, P = 0.029), independent of intact PTH; however, indoxyl sulfate did not correlate with TRACP-5b or 8-OHdG. These findings suggest that indoxyl sulfate may relate skeletal resistance to PTH in uremia.