title: Dietary magnesium reduction to 25% of nutrient requirement disrupts bone and mineral metabolism in the rat.
abstract: Low dietary magnesium (Mg) may be a risk factor for osteoporosis. In animals, severe Mg deficiency (0.04% of nutrient requirement [NR]) results in bone loss. We have also found that a more moderate dietary Mg restriction (10% of NR) also resulted in loss of bone. We now report the effect of Mg intake of 25% NR on bone and mineral metabolism in the rat. Serum Mg, Ca, PTH, 1,25(OH)2-vitamin D, alkaline phosphatase, osteocalcin, and pyridinoline were measured at 2, 4, and 6 months in control and Mg-deficient animals. Femurs and tibias were collected for mineral content, micro-computerized tomography, histomorphometry, and immunocytochemical localization. Profound Mg deficiency developed as assessed by marked hypomagnesemia and 27% reduction in bone Mg content. Serum calcium was not significantly different between groups. Mg depletion resulted in a significantly lower serum PTH concentrations. Serum 1,25(OH)2-vitamin D was also significantly lower. No difference was noted in markers of bone turnover. Histomorphometry and micro-computerized tomography demonstrated decreased bone volume and trabecular thickness. No difference was observed for osteoclast or osteoblast number. Inflammatory cytokines may contribute to bone loss. We found that immunocytochemical localization of TNFalpha in osteoclasts was increased 138-150%. This increase in TNFalpha may be due to increased substance P as it was found to be elevated from 179% to 432%. These data demonstrate that Mg intake of 25% NR in the rat causes lower bone mass which may be related to increased release of substance P and TNFalpha.
authors.affiliation: University of Southern California and the Orthopaedic Hospital, 1975 Zonal Avenue, GNH 6602, Los Angeles, CA 90089-9317, USA. rrude60075@aol.com
authors.forename: Robert K
authors.initials: RK
authors.lastname: Rude
authors.forename: Helen E
authors.initials: HE
authors.lastname: Gruber
authors.forename: H James
authors.initials: HJ
authors.lastname: Norton
authors.forename: Livia Y
authors.initials: LY
authors.lastname: Wei
authors.forename: Angelica
authors.initials: A
authors.lastname: Frausto
authors.forename: Jeremy
authors.initials: J
authors.lastname: Kilburn
mesh_terms: D000818:Animals; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000097:blood / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D004032:Diet; D005260:Female; D005269:Femur / Q000378:metabolism; D008274:Magnesium / Q000097:blood / Q000378:metabolism; D008275:Magnesium Deficiency / Q000378:metabolism* / Q000503:physiopathology*; D008903:Minerals / Q000378:metabolism*; D010006:Osteoblasts / Q000378:metabolism; D010010:Osteoclasts / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013977:Tibia / Q000378:metabolism
chemical_list: D016207:Cytokines; D008903:Minerals; D008274:Magnesium; D002118:Calcium