The Preliminary Study On The Casein Phosphopeptides Which Ameliorate Bone Loss In Simulated Space Environment

Purpose:Outer space is a complex environment with various phenomena that negatively affect bone metabolism, including microgravity and highly energized ionizing radiation. Although the research on the bone loss had been last for decades, the influence of radiation on the bone has just begun. What’s more, the combine effects of the radiation and microgravity on the bone loss has a conflict results. Casein phosphopeptides (CPPs) are a food additive that can store calcium to facilitate bone formation, but whether CPPs work well in low-calcium diet is still unclear. This research is based on the simulation of microgravity and radiation which we want to find the relationship of the two factors that caused the bone loss and the improvement of the CPPs to the bone at the same time.Methods:In the present study, we used10groups of male Wistar rats. Five of the groups were set as the model group:1).The control;2).4Gy X-ray;3).2Gy Carbon ion;4).Hind limb suspension after4Gy X-ray radiation and5).Hind limb suspension after OGy radiation. The other five groups were set as the treatment group with the addition of CPPs. We tested the serum cytokines and trabecular parameters as leading indicators of bone metabolism.Results:Hindlimb suspension, X-ray radiation and Carbon ion radiation caused a significant increase in bone loss, which was reduced by CPPs by56.6%(P＜0.001),30.7%(P＜0.001) and37.7%(P＜0.001), respectively when compared to the Control group. At the same time, after the CPPs were added, the bone loss was improved by51.8%(P＜0.001, HLS+CPPs versus HLS) and16.5%(P＜0.001, Carbon+CPPs versus Carbon)。Combined treatment with hindlimb suspension and X-rays exerted interaction on bone mass, with a reduction of64.8%(P=0.003). Also the bone improved by56.5%(P=0.01, HLS+X-ray+CPPs versus HLS+X-ray) when CPPs were added. The bone loss caused by X-rays or carbon-ion radiation differed significantly, with the carbon ion irradiated rats showing worse bone loss (10.1%, P=0.045). However, another interesting phenomena was that when compared to the Control, the Control+CPPs group showed a significant bone resorption (-23.9%, P＜0.05) which had never been reported in other researches. Conclusions:This research used the methods of hind limb suspension and radiation to simulate space environment and want to ensure the effects of the simulation on the base-ground. At the same time, it is also the first time to test whether the CPPs could improve the bone formation in a low-calcium diet. The results showed that the model groups could induce the bone loss; the interaction between the HLS and X-ray groups is significant. What’s more, these findings also demonstrated that CPPs could protect astronauts in the space environment, even under low-calcium diet.