Effect of aging and dietary restriction on matrix Gla protein and other components of rat tracheal cartilage

Age-related changes in connective tissues can alter their functions of elasticity, compressibility and support. Matrix Gla protein (MGP) is a vitamin K-dependent connective tissue component of unknown function. We have purified bovine MGP, and developed a specific radioimmunoassay for it. Since it is found in highest concentration in cartilage, we have developed quantitative extraction methods for MGP, and examined the age-related changes of MGP relative to other components found in the cartilage matrix. The ratio of hydroxyproline to MGP increases with age, while the ratio of glycosaminoglycan to MGP is constant. No effect is seen for MGP in the dietary restricted rat with prolonged lifespan, while both hydroxyproline and glycosaminoglycan contents of tracheal cartilage are significantly increased by dietary restriction (p < or = .05). These data show that MGP and glycosaminoglycan concentration are relatively constant in rats from 6 to 30 months of age, while hydroxyproline concentration increases with age.