Evaluation of microalgae on preventing bone loss in C57BL/6J mice induced by hindlimb suspension

Bone loss caused by microgravity severely damages the health of astronauts; however, no effective countermeasures exist. Microalgae are microscopic algae rich in protein, polysaccharide, and other nutrients, which can provide astronauts with safe food and oxygen supply in the space ecosystem. Recent studies have demonstrated that microalgae can potentially reduce bone loss in primary osteoporosis. Here, a hindlimb suspension (HLS) mouse (C57BL/6J) model was used to investigate the potential effects of five different microalgae in preventing microgravity-induced bone loss. The results showed that long-term administration of 300 mg/kg body weight/day Spirulina platensis (SP) significantly reduced bone loss and increased trabecular number and bone strength. In addition, mice in the HLS group also exhibited disordered gut microbiota with increased Firmicutes/Bacteroidetes, decreased fecal short-chain fatty acids levels, and increased levels of colonic proinflammatory cytokines interleukin-6 and tumor necrosis factor-alpha. To a certain extent, SP reduced these changes and maintained homeostasis of the intestinal environment. These results suggest that SP has a potential enhancing effect on resistance to bone loss in HLS mice.