Possible effects of one week vitamin K (menaquinone-4) tablets intake on glucose tolerance in healthy young male volunteers with different descarboxy prothrombin levels

Effect of Vitamin K Supplementation on Insulin Resistance in Older Men and Women

“…However in a recent observational study, the inverse association between vitamin K intake and insulin resistance was observed in men and women (3). In a previous metabolic study, only young men were studied (2), and there are no other studies with which to make a comparison. Although adjustment of BMI in the statistical model did not change our finding in women, one potential explanation for this lack of protective effect of vitamin K on insulin resistance in women is the role of adipose tissue in modulating the response to vitamin K supplementation.…”

“…In an observational study, higher dietary and supplemental vitamin K intakes were associated with greater insulin sensitivity and better glycemic status in a community-based cohort of men and women (3). In a small metabolic study of young men (n ϭ 12), short-term (1-week) vitamin K supplementation improved the insulin response after an oral glucose challenge (2). Although these studies support a potential novel role for vitamin K in insulin resistance, the available human data are limited.…”

“…imited evidence from human and animal studies suggests that vitamin K may be inversely associated with insulin resistance (1)(2)(3)(4). In an observational study, higher dietary and supplemental vitamin K intakes were associated with greater insulin sensitivity and better glycemic status in a community-based cohort of men and women (3).…”

A possible role of osteocalcin in the regulation of insulin secretion: human in vivo evidence?

“…According to their findings, the uncarboxylated OC regulated glucose homeostasis in Ptprv K/K mice, whilst only uncarboxylated OC induced the expression of insulin, b-cell proliferation and expression of adiponectin in adipocytes, in co-culture assays (Lee et al 2007), albeit in different concentrations (Ferron et al 2008). These results seem to contradict the aforementioned human in vivo findings of Sakamoto et al (2000), although it should be mentioned that Vestri et al (2008, unpublished data) studying the role of OC in human metabolism found that levels of uncarboxylated OC tended to be loweralbeit not significantly -in normoglycemic insulin resistant as well as untreated type 2 diabetes mellitus (T2DM) patients compared with normoglycemic insulin sensitive patients, concluding that OC is independently related to insulin sensitivity and fasting glucose and these interactions are primarily due to the uncarboxylated form of OC.…”

“…Sakamoto et al (1999) in an attempt to elucidate the role of vitamin K in the pancreas, administered vitamin K to young male volunteers and noticed that the group with low vitamin K intake displayed lower levels of insulin and lower insulinogenic index (incremental immunoreactive insulin over incremental plasma glucose, 0-30 min after 75 g oral glucose loading, indicating the early phase insulin secretion). Subsequently, the same research team (Sakamoto et al 2000) administered menaquinone-4 (90 mg/day for 1 week) in young male volunteers and examined the insulin and glucose levels during 75 g oral glucose loading before and after the administration of vitamin K. Interestingly, the subjects who had higher serum descarboxyprothrombin levels -i.e., lower vitamin K -exhibited the largest decrease in insulin secretion, suggesting that vitamin K may play an important role in the acute insulin response in glucose tolerance.…”