Vitamin K₂ therapy for postmenopausal osteoporosis.

Jun Iwamoto

doi:10.3390/nu6051971

Abstract

Vitamin K may play an important role in the prevention of fractures in postmenopausal women with osteoporosis. Menatetrenone is the brand name of a synthetic vitamin K2 that is chemically identical to menaquinone-4. The present review study aimed to clarify the effect of menatetrenone on the skeleton in postmenopausal women with osteoporosis, by reviewing the results of randomized controlled trials (RCTs) in the literature. RCTs that investigated the effect of menatetrenone on bone mineral density (BMD), measured by dual-energy X-ray absorptiometry and fracture incidence in postmenopausal women with osteoporosis, were identified by a PubMed search for literature published in English. Eight studies met the criteria for RCTs. Small RCTs showed that menatetrenone monotherapy decreased serum undercarboxylated osteocalcin (ucOC) concentrations, modestly increased lumbar spine BMD, and reduced the incidence of fractures (mainly vertebral fracture), and that combined alendronate and menatetrenone therapy enhanced the decrease in serum ucOC concentrations and further increased femoral neck BMD. This review of the literature revealed positive evidence for the effects of menatetrenone monotherapy on fracture incidence in postmenopausal women with osteoporosis. Further studies are required to clarify the efficacy of menatetrenone in combination with bisphosphonates against fractures in postmenopausal women with osteoporosis.

Highlights

There are two types of naturally occurring forms of vitamin K, phylloquinone and menaquinones.All forms of vitamin K contain a 2-methyl-1,4-naphthoquinone ring as part of their structure, and individual forms differ in the length and degree of saturation of a variable aliphatic side chain attached at the 3-position (Figure 1)
This evidence was derived from randomized controlled trials (RCTs) with small sample sizes
The present review investigated the effect of an anti-osteoporotic medicine, menatetrenone on the skeleton in postmenopausal women with osteoporosis

Summary

Introduction

There are two types of naturally occurring forms of vitamin K, phylloquinone and menaquinones.All forms of vitamin K contain a 2-methyl-1,4-naphthoquinone ring as part of their structure, and individual forms differ in the length and degree of saturation of a variable aliphatic side chain attached at the 3-position (Figure 1). Vitamin K is known to be a cofactor of γ-carboxylase, which converts three glutamic acid (Glu) residues in osteocalcin (OC) to γ-carboxyglutamic acid (Gla), and is essential for γ-carboxylation of OC [1,2,3,4]. Without this modification, OC becomes undercarboxylated OC (ucOC), which lacks structural integrity and the ability to bind to the mineral hydroxyapatite (Figure 2). Impaired vitamin K nutritional status or warfarin use results in high concentrations of serum ucOC, resulting in an increased risk for fractures. Vitamin K may play an important role in the prevention of fractures in postmenopausal women with osteoporosis

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Conclusion