(P30-004-25) Combinatorial Effects of Zinc Status and Aging on Bone in Male Mice

Objectives: A significant portion of older men are at risk for marginal zinc deficiency, osteoporosis, and increased risk for fractures. Dietary zinc is essential for optimal bone growth, but less is known regarding the combined impact of aging and dietary zinc status on skeletal health. The goal of this study was to evaluate the effect of age (young and old) and Zn status on bone mass and on cancellous bone microarchitecture in a mouse model.

Methods: Two experiments were conducted. To study the effects of marginal zinc deficiency, young (2-month-old) and old (24-month-old) C57BL/6 male mice were fed either a marginal Zn deficient (MZD, 6 mg Zn/kg diet) or a Zn adequate diet (ZA, 30 mg Zn/kg diet) for 6 weeks (n=8-10 mice/treatment group). To study the effects of zinc supplementation, young (2-month-old) and old (24-month-old) male mice were fed a Zn adequate or a zinc supplemented (ZS, 300 mg Zn/kg diet) diet for 6 weeks (n=8-10 mice/treatment group). Tibias were collected and evaluated using dual energy x-ray absorptiometry (whole tibia) and microcomputed tomography (proximal tibia metaphysis).

Results: In both experiments, cancellous bone volume fraction, connectivity density, and trabecular number were lower, while trabecular thickness and spacing were higher in old mice (ZA young vs ZA old). Neither 6 weeks of marginal zinc deficiency nor 6 weeks of zinc supplementation had any effect on the cancellous bone parameters measured in either age group (same age ZA vs MZD or same age ZA vs ZS). In addition, neither age nor zinc status affected total tibia bone mineral density.

Conclusions: In summary, aging had profound effects on cancellous bone microarchitecture in proximal tibia in male mice, with cancellous bone volume decreasing due to a reduction in trabecular number. In contrast, short-term exposure to nutritionally relevant zinc supplementation, or marginal zinc deficiency, had little impact on bone microarchitecture in young or old mice.

Funding Sources: National Institute of Food and Agriculture- Multi-state, Oregon Agricultural Experiment Station.