|Newman Jr, Samuel|
Submitted to: Journal of Nutritional Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2009
Publication Date: 4/10/2010
Publication URL: http://handle.nal.usda.gov/10113/40857
Citation: Hadley, K.B., Newman Jr, S.M., Hunt, J.R. 2010. Dietary Zinc Reduces Osteoclast Resorption Activities and Increases Markers of Osteoblast Differentiation, Matrix Maturation, and Mineralization in the Long Bones of Growing Rats. Journal of Nutritional Biochemistry. 21(4):297-303. Interpretive Summary: The nutritional influence of zinc on biochemical indicators of bone remodeling was investigated in growing rats. Thirty male weanling rats were randomly assigned to consume experimental diets containing deficient to adequate zinc for 24 d. The results of the study indicate that zinc requirements for bone development may be greater than previously determined. Trabecular bone increased, enzymes associated with bone accretion increased, and enzymes associated with bone resorption decreased as dietary zinc was increased beyond levels previously associated with maximum bone zinc concentrations. This research emphasizes that micronutrients such as zinc are essential for modulating the balance between bone formation and resorption.
Technical Abstract: The nutritional influence of zinc (Zn) on markers of bone extracellular matrix (ECM) resorption and mineralization was investigated in growing rats. Thirty male weanling rats were randomly assigned to consume AIN-93G based diets containing 2.5, 5, 7.5, 15, or 30 µg Zn/g diet for 24 d. Femur Zn increased substantially as Zn increased from 5 to 15 µg/g diet, and modestly between 15 and 30 µg/g (p<0.05). By morphological assessment, trabecular bone increased steadily as dietary Zn increased to 30 µg/g. Relative expression of Mt-I was elevated at 15 µg Zn/g dietand Zip2 expression tended to decrease with increasing dietary Zn. Zinc deficiency significantly increased femur osteoclastic resorption potential, indicated by matrix metalloproteinases (MMP-2, and MMP-9), and carbonic anhydrase-2 (CAII) activities. In contrast to indicators of ECM resorption, femur tartrate resistant acid (TRAP) and alkaline phosphatase (ALP) activities increased four-fold as dietary Zn increased from 2.5 to 30 µg Zn/g. Likewise, 15 or 30 µg Zn/g diet resulted in maximum relative expression of osteocalcin (OC), without influencing expression of Cbfa1, collagen type-1 alpha-1, or NFATc1. In conclusion, increased trabecular bone with additional Zn suggests that previous requirement estimates of 15 µg Zn/g diet may not meet nutritional needs for optimal bone development. Overall, the up-regulation of ECM modeling indexes (ALP, TRAP, OC) and concomitant decrease in resorption activities (CAII, MMP-2, and MMP-9) as dietary Zn increased from 2.5 to 30µg/g provide evidence of one or more physiological roles for Zn in modulating the balance between bone formation and resorption.