Impact of tacrolimus on bone metabolism after kidney transplantation

Bone disease is a common clinical problem after kidney transplantation. To date, studies investigating the effects of tacrolimus (TAC) on bone metabolism in vivo or vitro yielded conflicting data. This study was carried out to discuss the relationship between TAC blood concentrations and bone metabolism status in kidney transplant recipients. 72 kidney recipients whose time since transplantation more than 5 months (5-51 months) were divided into two groups by the TAC blood concentrations, high TAC group (TAC≥6 ng/mL) and low TAC group(TAC<6 ng/mL), respectively. Bone mineral density (BMD) of lumbar vertebrae L1-L4 and neck of the femur and allied biochemical markers (TRAP-5b, B-ALP, 25-(OH)D, PTH, beta-CrossLaps, N-MID Osteocalcin, Ca, PO4) were measured simultaneously. Our results showed that 27.78% of our patients had bone loss and the loss rates were statistical different between the high TAC group and low TAC group in kidney recipients (45.5% vs 20.0%, P=0.026). Correlation analysis showed that TAC concentrations were positively correlated with tartrate-resistant acid phosphatase-5b (TRAP-5b) in male recipients (r=0.287, P<0.05). In conclusion, kidney transplant recipients with high TAC blood concentrations are at risk of bone loss, and TAC may cause bone disorders involved in accelerated bone resorption.