Vitamin K help for diabetes?

Researchers writing in the journal Cells studied the effect bone cells have in energy regulation, and found that osteocalcin plays a key role in regulating insulin activity.

There are two main forms of vitamin K: phylloquinone, also known as phytonadione, (vitamin K1) which is found in green leafy vegetables such as lettuce, broccoli and spinach, and makes up about 90 per cent of the vitamin K in a typical Western diet; and menaquinones (vitamin K2), which make up about 10 per cent of Western vitamin K consumption and can be synthesised in the gut by microflora.

The study points to another potential avenue for vitamin K - a vitamin which is less known than vitamins A to E - and could help diversify its health benefits, which have previously been linked to cardiovascular health and bone health.

Previous animal studies have thrown up interesting results at high dose supplementation of vitamin K and its effect on arterial calcification.

Both K1 and K2 have been shown to play a role in bone health, influencing the secondary modification of osteocalcin, a protein needed to bind calcium to the bone matrix.

Some large human studies have tested the bone health benefits of calcium alone, calcium plus vitamin D and calcium plus vitamin D plus vitamin K. The latter has been reported to show the best effect on osteoporosis.

In this animal study, researchers from America, Canada and Britain identified the genes that operate primarily in the bone cells that are linked to glucose metabolism.

By "knocking out" these genes in mice so that they could not function, the animals lacking a functional osteocalcin gene gained fat, showing that osteocalcin helps regulate the cells that produce insulin in the pancreas and release it into the bloodstream.

These osteocalcin deficient mice also became glucose intolerant.

Both conditions are considered "pre-diabetic."

Osteocalcin was also shown to signal fat cells to release a hormone called adiponectin that increases insulin sensitivity.

" We show here that mice lacking the protein tyrosine phosphatase OST-PTP are hypoglycemic and are protected from obesity and glucose intolerance because of an increase in b-cell proliferation, insulin secretion, and insulin sensitivity.

In contrast, mice lacking the osteoblast-secreted molecule osteocalcin display decreased b-cell proliferation, glucose intolerance, and insulin resistance," the researchers wrote.

They added: "Ex vivo, osteocalcin can stimulate CyclinD1 and Insulin expression in b-cells and Adiponectin, an insulin-sensitizing adipokine, in adipocytes; in vivo osteocalcin can improve glucose tolerance.

"By revealing that the skeleton exerts an endocrine regulation of sugar homeostasis this study expands the biological importance of this organ and our understanding of energy metabolism."

American based firm PL Thomas, which markets a vitamin supplement for K2 as menaquinone-7 under the tradename MenaQ7 in alliance with Natto Pharma, Norway, welcomed the study which it says could help reinforce further potential health benefits of the vitamin.

A spokesperson said: " Obviously this is a very early observation and these results would need to be confirmed in humans.

The authors and experts in the field find the link very interesting, particularly if it yields new therapeutic benefits for diabetes.

"The vitamin K market is rapidly expanding as the benefits beyond coagulation become better known… it is only in the last year or so that industry has recognized vitamin K's role in activating osteocalcin for bone health and activating another k-dependent protein called matrix GLA protein (MGP) for cardiovascular health."

Source: Cells Published on-line, doi:10.1016/j.cell.2007.05.047. "

Endocrine Regulation of Energy Metabolism by the Skeleton " Authors: Na Kyung Lee, Hideaki Sowa, Eiichi Hinoi, Mathieu Ferron, Jong Deok Ahn, Cyrille Confavreux, Romain Dacquin, Patrick Mee, Marc McKee, Dae Young Jung, Zhiyou Zhang, Jason Kim, Franck Mauvais-Jarvis, Patricia Ducy, and Gerard Karsenty