Selenium-Containing Protein from Selenium-Enriched Spirulina platensis Relieves Osteoporosis by Inhibiting Inflammatory Response, Osteoblast Inactivation, and Osteoclastogenesis

Osteoporosis (OP) is a systemic bone disease with loss of bone mass and destruction of the microscopic structure. Many antiosteoporosis drugs have been used for OP therapy, but the therapeutic efficiency remains limited. Therefore, there is an urgent need to develop new drugs for antiosteoporosis treatment. Selenium (Se) is one kind of essential trace element for humans and displays pivotal roles in maintaining bone homeostasis. However, the modulation roles of Se are greatly affected by its chemical forms. Herein, Se containing protein derived from Se-enriched Spirulina platensis (Se-SP) were extracted and used for the treatment of OP in an ovariectomized mice model. The results showed that Se-SP showed enhanced potential in promoting excretion of calcium and alkaline phosphatase (ALP) expression than that of SP in MC3T3-E1 cells. Micro-CT revealed that Se-SP administration in vivo effectively alleviated bone loss as indicated by the upregulated BV, Tb.Th, Bv/TV, Tb.N, and BMD as well as the decreased Tb.Sp. Se-SP in vivo also significantly suppressed inflammatory response through restricting the expression of proinflammatory cytokines expression and upregulating the secretion of anti-inflammatory cytokines. Additionally, Se-SP effectively inhibited ovariectomy-induced osteoblast inactivation and osteoclastogenesis by upregulating BMP2, RUNX2, COL-I, OCN and OPG pression and downregulating RANKL expression. Together, these findings suggested that Se-SP was a new form of Se in therapy of human OP.