The potential benefits and mechanisms of protein nutritional intervention on bone health improvement

The discovery of the RANKL/RANK/OPG system in the mid 1990s for the regulation of bone resorption has led to major advances in our understanding of how bone modeling and remodeling are regulated. It had been known for many years before this discovery that osteoblastic stromal cells regulated osteoclast formation, but it had not been anticipated that they would do this through expression of members of the TNF superfamily: receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG), or that these cytokines and signaling through receptor activator of NF-kappaB (RANK) would have extensive functions beyond regulation of bone remodeling. RANKL/RANK signaling regulates osteoclast formation, activation and survival in normal bone modeling and remodeling and in a variety of pathologic conditions characterized by increased bone turnover. OPG protects bone from excessive resorption by binding to RANKL and preventing it from binding to RANK. Thus, the relative concentration of RANKL and OPG in bone is a major determinant of bone mass and strength. Here, we review our current understanding of the role of the RANKL/RANK/OPG system in bone modeling and remodeling. Show more

Key Clinical Points Postmenopausal Osteoporosis Fractures and osteoporosis are common, particularly among older women, and hip fractures can be devastating. Treatment is generally recommended in postmenopausal women who have a bone mineral density T score of -2.5 or less, a history of spine or hip fracture, or a Fracture Risk Assessment Tool (FRAX) score indicating increased fracture risk. Bisphosphonates (generic) and denosumab reduce the risk of hip, nonvertebral, and vertebral fractures; bisphosphonates are commonly used as first-line treatment in women who do not have contraindications. Teriparatide reduces the risk of nonvertebral and vertebral fractures. Osteonecrosis of the jaw and atypical femur fractures have been reported with treatment but are rare. The benefit-to-risk ratio for osteoporosis treatment is strongly positive for most women with osteoporosis. Because benefits are retained after discontinuation of alendronate or zoledronic acid, drug holidays after 5 years of alendronate therapy or 3 years of zoledronic acid therapy may be considered for patients at lower risk for fracture. Show more