|Seaborn, Carol - U OF WISC - MENOMONIE|
Submitted to: Journal of Trace Elements in Experimental Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2002
Publication Date: September 1, 2002
Citation: Seaborn, C.D., Nielsen, F.H. 2002. Silicon deprivation and arginine and cysteine supplementation affect bone collagen and bone and plasma trace mineral concentrations in rats. Journal of Trace Elements in Experimental Medicine. 15(3):113-122. Interpretive Summary: Low dietary silicon (Si) decreases the collagen concentration in bone and alters bone mineral composition in an apparent detrimental manner; the basis for these effects have not been established. Arginine has been established as an essential amino acid for the formation of collagen upon which bone mineralization occurs. Several bone remodeling proteins are rich hin the amino acid cysteine. To ascertain whether Si effects on bone occur through pathways involving arginine and/or cysteine, an experiment was performed with rats that were fed a diet inadequate and adequate in Si and supplemented with relatively high amounts of arginine or cystine. Si deficiency decreased a component of collagen, hydroxyproline, in bone (femur); this effect was not altered by the supplementation of either arginine or cystine. However, an interaction between cystine and Si affected bone mineral composition. In vertebra the major bone mineral elements calcium and phosphorus were increased by high dietary cystine whe Si was inadequate, but cystine had no effect when Si was adequate. High dietary cystine decreased the concentrations of two minerals involved in the formation of the organic matrix of bone, copper and manganese, in vertebra when dietary Si was inadequate, but increased the concentrations when dietary Si was adequate. Vertebra findings were used as examples because the interaction between Si and cystine more markedly affected the mineral concentrations of vertebra than tibia. The findings indicate that Si deficiency has more impact on trabecular-rich bone (vertebra) than cortical-rich bone (tibia), and this impact can be affected by cystine intake. Si apparently is nutritionally important for bone health; it may help protect against developing osteoporosis.
Technical Abstract: We performed a study to ascertain whether supplemental arginine (Arg) and cystine (Cys) would affect bone collagen and mineral composition changes in animals deprived of silicon (Si). Male weanling Sprague-Dawley rats were randomly assigned to treatment groups of twelve in a 2 x 2 factorially arranged experiment. The rats were fed for nine weeks a basal diet containing per g 2 ug Si, 1.7 mg Cys, 4.7 mg methionine and 7.8 mg Arg. Th independent treatment variables, per g fresh diet, were supplemental Si at 0 and 35 ug and Cys or Arg at 0 and 12 mg. Silicon deprivation decreased the concentration of hydroxyproline in femur. In animals deprived of Si, Cys supplementation compared to Arg supplementation depressed hematocrit, liver iron concentration and tibia copper concentration and increased tibia manganese concentration. On the other hand, in animals fed adequate Si, supplemental Cys compared to supplemental Arg increased hematocrit and liver iron concentration and tibia copper concentration and decreased tibi manganese concentration. In vertebra, dietary Si influenced the effect of Cys on mineral composition. Vertebra calcium and phosphorus were markedly increased by supplemental Cys compared to supplemental Arg when dietary Si was inadequate, but had no effect on these concentrations when dietary Si was adequate. Supplemental Cys compared to supplemental Arg increased vertebral concentrations of manganese and copper when dietary Si was adequate, but decreased these concentrations when dietary Si was inadequate. These findings suggest that Si nutriture has more impact on trabecular-rich bone than in cortical-rich bone. Moreover, high dietary Cys apparently enhances changes induced by Si deprivation in trabecular-rich bone.