Friday, January 22, 2010

Vitamin K

Effects of vitamin K on the morphometric and material properties of bone in the tibiae of growing rats.

"Suboptimal vitamin K nutriture is evident during rapid growth. We aimed to determine whether vitamin K(2) (menaquinone-4 [MK-4]) supplementation is beneficial to bone structure and intrinsic bone tissue properties in growing rats. Male Wistar rats (5 weeks old) were assigned to either a control diet or an MK-4-supplemented diet (22 mg d(-1) kg(-1) body weight). After a 9-week feeding period, we determined the serum concentration ratio of undercarboxylated osteocalcin to γ-carboxylated osteocalcin and the urinary deoxypyridinoline level. All rats were then euthanized, and their tibiae were analyzed. Neither body weight nor tibia length differed significantly between the 2 groups. Dietary MK-4 supplementation decreased the ratio of undercarboxylated osteocalcin to γ-carboxylated osteocalcin but did not affect deoxypyridinoline, indicating a positive effect on bone formation but not bone resorption. Trabecular volume fraction and thickness were increased by MK-4. Neither the cortical pore structure nor mineralization was affected by MK-4. On the other hand, MK-4 increased mineral crystallinity, collagen maturity, and hardness in both the anterior and posterior cortices."

Tibia length was 35.6 for the K supplement group and 35.5 for control.

Effects of vitamin K on the morphometric and material properties of bone in the tibiae of growing rats.

 Vitamin K is a liposoluble vitamin. The predominant dietary form, phylloquinone or vitamin K1, is found in plants and green vegetables; whereas menaquinone, or vitamin K2, is endogenously synthesized by intestinal bacteria and includes several subtypes that differ in side chain length. Aside from its established role in blood clotting, several studies now support a critical function of vitamin K in improving bone health. Vitamin K is in fact required for osteocalcin carboxylation that in turn regulates bone mineral accretion; it seems to promote the transition of osteoblasts to osteocytes and also limits the process of osteoclastogenesis. Several observational and interventional studies have examined the relationship between vitamin K and bone metabolism, but findings are conflicting and unclear. This systematic review aims to investigate the impact of vitamin K (plasma levels, dietary intake, and oral supplementation) on bone health with a particular interest in bone remodeling, mineral density and fragility fractures.”
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Effects of the combination of vitamin K and teriparatide on the bone metabolism in ovariectomized rats

 The purpose of the present study was to evaluate the combined effects of vitamin K (VK) and teriparatide (TPTD) on bone mineral density (BMD), mechanical strength and other parameters for bone metabolism using a rat ovariectomized osteoporosis model. Ovariectomized female Sprague‑Dawley rats were administered with VK (an oral dose of 30 mg/kg/day), TPTD (a subcutaneous dose of 30 µg/kg, three times a week) or a combination for 8 weeks. Thereafter, serum levels of γ‑carboxylated osteocalcin (Gla‑OC) were quantitated by ELISA; BMD and mechanical strength were measured by computed tomography and biomechanical testing, respectively at the femoral metaphysis. Additionally, histomorphometry was performed using the toluidine blue‑stained coronal sections of distal femur. The combination of VK and TPTD clearly increased the serum levels of Gla‑OC (a specific marker for bone formation) and osteoblast surface (the number of osteoblasts attaching with the surface of cancellous bone), compared to VK or TPTD alone. In addition, the combination of the two agents improved the BMD and bone strength of the femur in the ovariectomized rats, compared to VK or TPTD alone. Taken together, these findings suggest that the treatment with VK and TPTD may have a therapeutic advantage over VK or TPTD monotherapy for postmenopausal osteoporosis, possibly by enhancing the bone formation through the actions on OC and osteoblasts.”

An insight into the role of vitamins other than D on bone

 Vitamins are essential micronutrients for normal development. Great emphasis has been placed on vitamin D for bone development and maintenance. However, other vitamins also influence bone health. While some of them are more beneficial to bone and increase bone mass by increasing bone formation, calcium deposition and stimulate osteoblastogenesis, higher concentrations of others have deleterious effects causing fragile bones and increasing the risk of fractures. Knowledge about the effects of these vitamins will help in better maintenance of bone. This review focuses on the information available on vitamins A, B, C, E and K on bone health. Existing information supports vitamin C and K to play a role in bone formation and calcification. Vitamin E in low amounts and some of the B vitamins may also be beneficial to bone. There is very limited data supporting the favorable effects of vitamin A”
 RA treatment of growth plate chondrocytes, induced annexins II, V and VI to form Ca2+ channels and influx calcium into the cells. ”

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