High dietary iron and 137Cs radiation exposure induce oxidative stress and reduce bone mass

Abstract

Astronauts are exposed to increased iron (Fe) stores and risk radiation exposure during spaceflight. We hypothesized that a high Fe diet and radiation exposure would independently increase markers of oxidative stress and result in loss of bone mass. Male rats (3‐mo‐old, n=32) were randomized to receive an adequate (45 mg Fe/kg) or high (650 mg Fe/kg) Fe diet for 4 wks and either 3 Gy (8 fractions, 0.375 Gy each) of 137Cs radiation (γ RAD) or sham exposure starting on d 14. Ex vivo pQCT quantified volumetric bone mineral density (vBMD); bone mechanical strength (ultimate load, UL) was assessed by 3‐pt bending (midshaft tibia) and compression of the femoral neck. Serum Fe and catalase increased only with the combined treatment, whereas serum glutathione peroxidase decreased in all groups. γRAD and high Fe diet lowered proximal tibial (PT) cancellous vBMD (by −15% and − 12%, respectively); high Fe diet produced a small decrease in femoral neck (FN) total vBMD (−4%, p=0.07). Cortical vBMD at midshaft tibia was lower after high Fe diet, but not after γRAD. Higher serum Fe levels at 4 wks were associated with lower PT cancellous vBMD (r = −0.61); higher serum catalase was associated with lower vBMD at the 3 different bone sites (r = − 0.52). No significant differences in UL at mid‐shaft tibia or FN were detected. Oxidative stress is increased by fractionated γRAD and iron overload and is associated with a negative impact on bone mass.Grant Funding Source : NASA Human Research Program and NSBRI via NASA NCC9‐588