Partial Protection by Dietary Antioxidants Against Ethanol-Induced Osteopenia and Changes in Bone Morphology in Female Mice

Background: Chronic alcohol consumption leads to increased fracture risk and an elevated risk of osteoporosis by decreasing bone accrual through increasing osteoclast activity and decreasing osteoblast activity. We have shown that this mechanism involves the generation of reactive oxygen species (ROS) produced by NADPH oxidases. It was hypothesized that different dietary antioxidants, N-acetyl cysteine (NAC; 1.2 mg/kg/d), and alpha-tocopherol (Vit.E; 60 mg/kg/d) would be able to attenuate the NADPH oxidase-mediated ROS effects on bone due to chronic alcohol intake. Methods: To study the effects of these antioxidants, female mice received a Lieber-DeCarli liquid diet containing ethanol (EtOH) with or without additional antioxidant for 8 weeks. Results: Tibias displayed decreased cortical bone mineral density in both the EtOH and EtOH + antioxidant groups compared to pair-fed (PF) and PF + antioxidant groups (p < 0.05). However, there was significant protection from trabecular bone loss in mice fed either antioxidant (p < 0.05). Microcomputed tomography analysis demonstrated a significant decrease in bone volume (bone volume/tissue volume) and trabecular number (p < 0.05), along with a significant increase in trabecular separation in the EtOH compared to PF (p < 0.05). In contrast, the EtOH + NAC and EtOH + Vit.E did not statistically differ from their respective PF controls. Ex vivo histologic sections of tibias were stained for nitrotyrosine, an indicator of intracellular damage by ROS, and tibias from mice fed EtOH exhibited significantly more staining than PF controls. EtOH treatment significantly increased the number of marrow adipocytes per mm as well as mRNA expression of aP2, an adipocyte marker in bone. Only NAC was able to reduce the number of marrow adipocytes to PF levels. EtOH-fed mice exhibited reduced bone length (p < 0.05) and had a reduced number of proliferating chondrocytes within the growth plate. NAC and Vit.E prevented this (p < 0.05). Conclusions: These data show that alcohol's pathological effects on bone extend beyond decreasing bone mass and suggest a partial protective effect of the dietary antioxidants NAC and Vit. E at these doses with regard to alcohol effects on bone turnover and bone morphology.