Effects of Moderate Zinc Deficiency and Phytase Supplementation on Musculoskeletal Integrity in Exercising Rats

Abstract

It is not clear how the adaptations to chronic exercise may be affected by a phytase (P) supplemented low zinc (Zn) diet. Phytic acid (PA) is known to form insoluble complexes with nutritionally essential minerals; including Zn. Phytases are enzymes that aid the removal of essential minerals from PA, thus increasing their bioavailability. PURPOSE: To determine the effects of a low Zn diet and supplemental P on bone and muscle in voluntary 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 nine weeks, (n=10 per group). In vivo peripheral quantitative computed tomography scans were performed at 10 and 50% of the total tibia length. Cortical content (CCNT) (mg), cortical area (CA) (mm2) and polar strength strain index (SSIp) (mm3) were investigated at the 10 and 50% regions of interest (ROI). Muscle area (MA) (mm2) was additionally investigated at the 50% ROI. A one-way ANOVA and Tukey post-hoc were used to analyze the data. RESULTS: At the 10% ROI, ZnAd exhibited increased CCNT and greater SSIp as compared to ZnLo and ZnLo+P. At the 50% ROI, ZnAd exhibited increased CCNT, CA and greater SSIp as compared to ZnLo and increased MA as compared to ZnLo and ZnLo+P. Additionally at the 50% ROI, ZnLo+P exhibited increased CCNT and MA as compared to ZnLo.TableCONCLUSION: P-supplementation increased mid-shaft CCNT and MA in a moderately Zn deficient sample but did not match the superior indices of bone strength and lean mass that were observed by consuming a 30ppm Zn diet.