Pharmacodynamics of menatetrenone and effects on bone metabolism in continuous ambulatory peritoneal dialysis patients

Vitamin K status in chronic kidney disease

The purpose of this review is to summarize the research to date on vitamin K status in chronic kidney disease (CKD). This review includes a summary of the data available on vitamin K status in patients across the spectrum of CKD as well as the link between vitamin K deficiency in CKD and bone dynamics, including mineralization and demineralization, as well as ectopic mineralization. It also describes two current clinical trials that are underway evaluating vitamin K treatment in CKD patients. These data may inform future clinical practice in this population.

Vitamin K, bone fractures, and vascular calcifications in chronic kidney disease: an important but poorly studied relationship

Vitamin K denotes a group of lipophilic vitamins determining post-translational modification of proteins. There are 2 main forms of vitamin K: vitamin K1 (phylloquinone, found in vegetables); vitamin K2 (menaquinone, produced by bacteria in the intestine and in fermented foods). Vitamin K stores are limited in humans, but it can be recycled. Vitamin K1 is principally transported to the liver, regulating the production of coagulation factors. Vitamin K2, instead, is also transported to extra-hepatic tissues, such as bone and arteries, regulating the activity of matrix Gla-protein (MGP) and osteocalcin [bone Gla-protein (BGP)]. In patients with chronic kidney disease (CKD), cardiovascular mortality is the first cause of death. Some pathogenetic mechanisms of vascular calcification (such as hyperparathyroidism, hyperphosphatemia, hypercalcemia, role of vitamin D) have been widely investigated, but the potential role of vitamin K is still uncertain. Vitamin K could play a key role, as it transforms glutamic acid residues into γ-carboxyglutamic acid, through a carboxylation process, makings both MGP (cMGP) and BGP (cBGP) biologically active. cMGP inhibits vascular calcifications (VC), while cBGP has an important role for a proper mineralization process. Uncarboxylated MGP and BGP (ucMGP and ucBGP) concentrations are indirect markers of vitamin K2 deficiency. The purpose of this review is to analyze the current literature to understand the relationship between vitamin K2 status, fragility fractures and VC in CKD patients. This analysis could be of help in planning investigations of Vitamin K status and its possible supplementation in CKD patients to avert fragility fractures and VC.

Vitamin K2 inhibits the growth and invasiveness of hepatocellular carcinoma cells via protein kinase A activation

Hepatocellular carcinoma (HCC) is a common human malignancy. Its high mortality rate is mainly a result of high intrahepatic recurrence and portal venous invasion (PVI). We previously reported that the development of PVI is related to levels of des-gamma-carboxy prothrombin (DCP), a serum protein that increases at a notably higher rate in patients with HCC. Because DCP is produced by a vitamin K shortage, we examined the biological effects of extrinsic supplementation of vitamin K(2) in HCC cells in vitro and in vivo. Consequently, vitamin K(2) inhibits the growth and invasion of HCC cells through the activation of protein kinase A, which modulates the activities of several transcriptional factors and inhibits the small GTPase Rho, independent of suppression of DCP. In addition, administration of vitamin K(2) to nude mice inoculated with liver tumor cells reduced both tumor growth and body weight loss. In conclusion, similar to an acyclic retinoid--which was previously reported to prevent the recurrence of HCC--vitamin K(2), another lipid-soluble vitamin, may be a promising therapeutic means for the management of HCC.