OBJECTIVETo explore the effect of Modified Sijunzi Decoction (MSD) on the bone metabolism of prednisone intervened adriamycin-induced nephropathy rats.

METHODSThe adriamycin-induced nephropathy rat model was prepared. Totally 50 SD rats were randomly divide into five groups, i.e., the model group, the hormone group, the Chinese medicine (CM) group, the CM + hormone group, and the normal control group. The 24-h urine samples were collected on the 7th, 21st, and 35th day after modeling. The 24-h urine protein was measured by biuret colorimetry. Serum levels of osteoprotegerin (OPG), receptor activator of nuclear factor-kappaB ligand (RANKL), osteocalcin (BGP), and tartrate-resistant acid phosphatase (TRACP) were determined by ELISA. Expressions of OPG and RANKL in the tibia tissue were detected using real-time quantitative PCR and Western blot.

RESULTS(1) Compared with the normal control group, the 24-h urine protein increased in each group on the 7th, 21st, and 35th day (P < 0.05, P < 0.01). Compared with the model group, the 24-h urinary protein decreased in the hormone group and the CM + hormone group (P < 0.05, P < 0.01). The decrement was more obvious along with the treatment time went by (P < 0.05, P < 0.01). There was statistical difference in the reduction of urine protein on the 35th day between the CM group and the model group (P < 0.05). (2) Compared with the 21st-day of the same group, the serum levels of TRACP and RANKL increased (P < 0.05, P < 0.01). Compared with the model group, the serum levels of the TRACP and RANKL increased (P < 0.05, P < 0.01), OPG and BGP decreased (P < 0.05, P < 0.01) in the hormone group. Compared with the CM group at the same period, serum OPG level decreased and the RANKL level increased in the hormone group and the CM + hormone group (P < 0.05, P < 0.01). Besides, the serum level of TRACP increased and BGP decreased (P < 0.05, P < 0.01). Compared with the hormone group at the same period, OPG and BGP increased (P < 0.05, P < 0.01), RANKL decreased (P < 0.01) in the CM + hormone group. On the 35th day TRACP decreased (P < 0.01). (3) Compared with the normal group, mRNA expressions of OPG and RANKL on the 21st day increased (P < 0.05, P < 0.01), mRNA expressions of OPG and RANKL on the 35th day decreased in the model group (P < 0.01). Compared with the CM group at the same period, OPG mRNA expression decreased (P < 0.01) and RANKL mRNA expression increased in the hormone group (P < 0.05). OPG mRNA expression decreased in the CM +hormone group (P < 0.05). (4) Compared with the hormone group on the 21st day, the OPG level decreased and the RANKL protein increased (both P < 0.05). RANKL decreased in the CM + hormone group (P < 0.05). Compared with the model group at the same period, OPG decreased and RANKL increased in the hormone group (P < 0.01). Compared with the CM group at the same period, OPG decreased (P < 0.01), RANKL increased (P < 0.01) in the hormone group and the CM + hormone group. Compared with the hormone group at the same period, OPG increased and RANKL decreased in the CM + hormone group (both P < 0.01).

CONCLUSIONSPrednisone could induce osteoporosis through the OPG/RANKL/RANK pathway. MSZ could slow down the formation of prednisone-induced osteoporosis through promoting osteoblast differentiation, and inhibiting osteoclastogenesis.