Effects of Moderate Zinc Deficiency and Phytase Supplementation on Lumbar Vertebrae in Exercising Rats

Dietary zinc (Zn) is important for bone remodeling. Phytase (P) increases the bioavailability of Zn and other micronutrients. How modeling adaptations of the lumbar spine may be affected by a P supplemented low Zn diet has not been investigated. PURPOSE Determine the effects of a low Zn diet and supplemental P on the 4th lumbar vertebra (L‐4) in exercising rats. METHODS 30 Male Sprague‐Dawley rats were housed in cages fitted with voluntary running wheels and fed either a 5ppm Zn (ZnLo), 5ppm Zn + 1,500 FTU/kg P (ZnLo+P) or a 30ppm Zn (ZnAd) diet for 9 wks, (n=10 per group). In vivo peripheral quantitative computed tomography scans were performed at 40, 50 and 60% of the total L‐4 length. Cortical content (CNT) (mg), area (A) (mm 2 ) and bone mineral density (BMD) (mg/cm 3 ) were measured. Plasma concentrations (PC) (µg/ml) of Zn were determined. A one‐way ANOVA was used to compare the data. RESULTS ZnLo+P exhibited increased CNT (11.6 ± 1.5 vs. 9.9 ± 0.7, p=0.006), A (12.0 ± 1.4 vs. 10.5 ± 0.7, p=0.007) and BMD (959.5 ± 15.9 vs. 938.8 ± 7.9 p=0.012) compared to ZnLo and increased BMD (959.5 ± 15.9 vs. 942.5 ± 18.9, p=0.043) compared to ZnAd. ZnAd exhibited increased PC of Zn (1.2 ± 0.2 vs. 0.8 ± 0.1 and 0.5 ± 0.2, p<0.001) compared to ZnLo+P and ZnLo respectively. ZnLo+P exhibited increased PC of Zn (0.8 ± 0.1 vs. 0.5 ± 0.2, p=0.01) compared to ZnLo. CONCLUSION P supplementation increased PC of Zn and increased mid‐vertebral cortical CNT, A and BMD in a ZnLo fed sample. The greatest L‐4 cortical modeling was observed in rats fed a ZnLo+P diet. The study was funded by the U.S. Army MRMC