High-phosphorus diet stimulates receptor activator of nuclear factor-kappaB ligand mRNA expression by increasing parathyroid hormone secretion in rats.
The purpose of the present study was to clarify the manner by which the supplementation of high-P diet induces bone loss. Eighteen 4-week-old male Wistar-strain rats were assigned randomly to three groups and fed diets containing three P levels (0.3, 0.9, and 1.5 %) for 21 d. A lower serum Ca concentration was observed in the rats fed on the 1.5 % P diet than in the other two groups. Serum P and parathyroid hormone concentrations and urinary excretion of C-terminal telopeptide of type I collagen were elevated with increasing dietary P levels. Serum osteocalcin concentration was increased in the rats fed on the 1.5 % P diet than in the other two groups. Bone formation rate of the lumbar vertebra was significantly increased in the two high-P groups than in the 0.3 % P group. Osteoclast number was significantly increased with increasing dietary P levels. Bone mineral content and bone mineral density of the femur and lumbar vertebra and ultimate compression load of the lumbar vertebra were decreased with increasing dietary P levels. Additionally, ultimate bending load of the femur was decreased in the rats fed on the 1.5 % P diet than in the other two groups. Receptor activator of NF-kappaB ligand (RANKL) mRNA expression in the femur was significantly higher with increasing dietary P levels. These results suggest that secondary hyperparathyroidism due to a high-P diet leads to bone loss via an increase in bone turnover. Furthermore, an increase in osteoclast number was caused by increased RANKL mRNA expression.
Katsumata
Shin-Ichi
S
Department of Nutritional Science, Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan. kazu@nodai.ac.jp
Masuyama
Ritsuko
R
Uehara
Mariko
M
Suzuki
Kazuharu
K
D000818:Animals; D015519:Bone Density; D001862:Bone Resorption / Q000503:physiopathology; D002118:Calcium / Q000097:blood; D002352:Carrier Proteins / Q000032:analysis*; D002478:Cells, Cultured; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis*; D010281:Parathyroid Hormone / Q000097:blood*; D016226:Phosphorus, Dietary / Q000008:administration & dosage* / Q000097:blood; D053245:RANK Ligand; D012333:RNA, Messenger / Q000032:analysis*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D044168:Receptor, Parathyroid Hormone, Type 1
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D010281:Parathyroid Hormone; D016226:Phosphorus, Dietary; D053245:RANK Ligand; D012333:RNA, Messenger; D044168:Receptor, Parathyroid Hormone, Type 1; D002118:Calcium