Introduction: Recent studies have shown that salt can play an important role in undermining regulatory mechanisms of the innate and adaptive immune systems. Hi dietary salt intake leads to induction of Th17 cells (main culprits for enhanced bone loss) leading to various immune disorders. Based on these findings we hypothesized to study the effect of high dietary salt intake on bone health.
Materials & methods: 8-10 weeks old male mice (under standard SPF conditions) in three groups were fed diets with Normal (0.8% NaCl), Lo salt (0.4% NaCl) and Hi salt (4% NaCl) concentrations. After 45 days mice were sacrificed and analyzed for various parameters to access the role of high dietary salt intake on bone health by using various cutting-edge technologies such as SEM, AFM, μCT, FTIR, FACS, ELISA etc.
Results: It was found that hi dietary salt intake leads to enhanced bone loss as confirmed by SEM, AFM and μCT analysis of bone samples. Further studies revealed that hi salt intake enhances the population of Th17 cells and decreases that of Treg cells in both primary and secondary lymphoid tissues. During serum cytokine analysis, it was found that hi salt intake has significantly decreased anti-osteoclastogenic cytokines (IL-10, IFN-γ) and enhanced osteoclastogenic cytokines (IL-6, IL-17, TNF-α), whereas low salt intake completely reverses these observed effects.
Discussions: Bone loss is usually associated with increase in the expression of Th17 cells and suppression of Treg cells. Hi salt intake increases the expression of various proinflammatory cytokines viz. IL-6, IL-17 and TNF-α that enhance bone loss through RANKL expression and simultaneously decreases the expression of different anti-inflammatory cytokines e.g. IL-10 and IFN-γ. Also, hi dietary salt intake significantly inhibited not only trabecular but also cortical bone content of mice.
Conclusion: Our results for the first time report the effect of high dietary salt intake on bone loss via modulating the balance of Treg and Th17 cells. These results once again highlight the importance of environment in the form of high salt intake on immune system ultimately leading to increased risk of various inflammatory diseases such as osteoporosis.
Acknowledgement: UGC-FRPS, Govt. of India for financial support and Dept. of Zoology, DHGVV, Sagar for infrastructural facilities.
|