POSITIVE ASSOCIATION BETWEEN SERUM VITAMIN K LEVEL AND BONE MINERAL DENSITY

Introduction: Vitamin K is well known for its role in the synthesis of many blood coagulation factors. Also, vitamin K-dependent proteins are very important for bone and vascular health. Vitamin K is known to influence bone metabolism by facilitating the synthesis of osteocalcin because is required for the γ-carboxylation of specific glutamic acid residues, wich in turn, allows a firm binding of calcium ions. The bone mineral density decreases drastically after menopause. Recent studies have been shown that vitamin k influences bone mineral density in osteoporotic people and also actually reduce fracture rates. Many factors influence the individual risk of osteoporosis: genetic predisposition, age, sex, race, general health, exercise, smoking, alcohol abuse, hormone therapy and nutritional factors. In fact, current research is emphasizing the role of nutrition in the development of this disease and has been focused on calcium, magnesium, vitamin D roles and macronutrients such as proteins. In the present study, we investigated the relationship between vitamin K1 and K2 levels and bone mineral density in post-menopausal women. Materials and methods: Serum levels of vitamins K1 and K2, osteocalcin and other markers of bone metabolism were measured in 100 post-menopausal women (19 with reduced bone mineral density and 52 with normal bone density). Vitamin K1 and K2 levels were measured by HPLC method. The vitamins in plasma were analyzed by reversed-HPLC with UV detection at 250 nm. The mobile phase was methanol and ethanol (85:15,v/v) with 0.1 % triethylamine. Results: The mean concentration (± SE)of vitamin K1 in the normal bone density group was 0.60±0.03 ng/ml, in the reduced bone density group was 0.36±0.02 ng/ml. The mean concentration (± SE)of vitamin K2 in the normal one was 1.0±0.04 ng/ml, in the reduced one was 0.72±0.02 ng/ml. Post-menopausal women with reduced bone mineral density showed lower levels of vitamins K1 and K2 than those with normal bone mineral density. Conclusions: The present findings suggested that vitamin K level is related to post-menopausal bone mineral loss. An extension of this theory is that Vitamin B6 is an essential cofactor for the ornithine decarboxylase, which regulates osteoblast glucose-6-phosphate dehydrogenase activity and thus NADPH concentrations: this is essential for the vitamin K cycle, where its epoxide form is converted to the naphtoquinone form, required for γ-carboxylation of osteocalcin. Thus, probably, the vitamin B6 status could modulate the effects of vitamin K on bone metabolism. References:Vermeer C., et al. (2004) Eur J nutr 43: 325-335. 260 biochimica