Key Trace Elements Zinc and Magnesium Levels Decline After Fracture in a Rat Model
Authors: Lopez Jonathan R. , Ahn David , Fisher Mark , Mendiratta Dhruv , Herzog Isabel , Chee Ruey Horng , Levine Carter , Docuyanan Ariel A. , Dompor Alexis , Moriarty Brian , Daniels Jason M. , Nie Glen , Paglia David , Benevenia Joseph , Lin Sheldon S. , O’Connor James P. 
Published: December 2023

Category: Basic Sciences/Biologics; Basic Sciences/Biologics Introduction/Purpose: Zinc and magnesium are crucial for bone health, and their deficiencies can lead to impaired bone metabolism and repair. Although enhancing their bioavailability has been linked to better fracture healing, their levels during healing have not been studied. We hypothesized that zinc and magnesium levels transiently decrease at the fracture site compared to intact bone. This study is the first to explore temporal trace element levels during the initial stages of fracture healing. The findings will reveal when each element changes its concentration at the fracture site, which is associated with specific functions necessary for appropriate healing. Understanding the connection between trace element concentration and repair processes could lead to more effective treatment or supplementation during fracture healing. Methods: Following induction of a femur fracture in male BB Wistar rats, injured and intact contralateral femurs were harvested at 1- (n=3), 3- (n=4), and 7-days (n=3) after fracture. Fracture segments 10mm in length were resected 5mm from the center of the callus in either direction. Contralateral non-fractured femur segments were resected from the same region within the femoral diaphysis. Samples were analyzed via inductively coupled mass spectrometry using an Agilent ICP-MS 7900 (Agilent Technologies, Santa Clara, CA). Data was converted from ppb to percent weight zinc and magnesium per weight of bone (w/w%). The difference between zinc and magnesium in contralateral intact bone vs. fractured bone was calculated and averaged (∆) for each group. The average % change were also determined. An independent sample two-tailed t-test was performed comparing average w/w% of zinc and magnesium between fracture and contralateral samples. A p-value of < 0.05 was considered significant. Results: After 1-day post-fracture, there was a -29.09 average % change in zinc levels (∆ 6.90x10^-03 ± 5.05x10^-03) (p = 0.033) and a -25.76 average % change in magnesium levels (∆ 1.21x10^-01 ± 7.36x10^-02 w/w%) (p = 0.241) between fractured and non- fractured femurs. After 3-days post-fracture, there was a -22.51 average % change in zinc levels (∆ 5.45x10^-03 ± 3.95x10^-03 w/w%) (p = 0.022) and a -33.07 average % change in magnesium levels (∆ 1.84x10^-01 ± 1.05x10^-01 w/w%) (p = 0.025). After 7- days post-fracture, there was a -9.40 average % change in zinc levels (∆ 1.90x10^-03 ± 3.98x10^-03) (p = 0.377) and a -17.88 average % change in magnesium levels (∆ 9.04x10^-02 ± 1.24x10^-01 w/w%) (p = 0.159) between fractured and non-fractured femurs. Conclusion: Previous research has established the significance of trace elements, namely zinc and magnesium, in the process of fracture healing. Zinc has been shown to improve fracture healing, while magnesium has been found to play a role regulating inflammation during early fracture healing. The findings of this study corroborate our hypothesis that levels of these elements transiently decline following fracture. By evaluating these changes in trace element levels, we can gain a better understanding of their function in the fracture healing process. These observations may offer insight into potential therapeutic approaches utilizing zinc and magnesium for fracture healing in the future.