New vitamin K trial for kidney disease

You've probably heard of vitamins A, B, C and D - but what about vitamin K? It's found in green leafy veg, vegetable oils and grains and is normally involved in blood clotting and bone health. But that's not all - researchers at the British Heart Foundation have just launched a clinical trial to find out whether this vital vitamin could have a life-saving impact on patients with chronic kidney disease. Kat Arney spoke to the charity's Associate Medical Director, Jeremy Pearson to find out how...

Jeremy - Chronic kidney disease is quite common - something like 1 in 5 of the population over the age of 70, amazingly, have some symptoms of chronic kidney disease.  The major risk factors are high blood pressure and diabetes and the major complication, as far as The British Heart Foundation is concerned, is that these patients have a high excess mortality of cardiovascular disease, so kidney disease causes cardiovascular disease. The way in which it does it is by increasing calcification - stiffening of the arteries.  The reason for using vitamin K in this study is the hope that this will reduce the stiffening of the arteries because what it does is interferes with one of the proteins that causes the stiffening.

Kat - What was idea for the trial?  Where did it all start?

Jeremy - Because there are no good cures for chronic kidney disease - in fact there are no cures at the moment - and most patients will gradually progress towards, ultimately, needing dialysis regularly or even a kidney transplant.  It's therefore a disease with a high burden on the NHS and also a high burden on the patient with poor quality of life and, ultimately, high morbidity.  So there's been quite a search for any kind of drug that might help alleviate or slow down the symptoms and progression of the disease.  The current status is - okay we know what the risk factors are - reduce the risk factors.  So try and lower your blood pressure, that's the first thing and you will be given medication to lower your blood pressure.  Secondly, it's also clear that this is associated with the standard things that you would find for risk factors for heart disease, so the patient will be told to lower the cholesterol levels either by diet or, if not possible by diet, by statin or something like that. All that does though is slow down the process of the kidney damage and it doesn't seem to do very much to the stiffening of the arteries, which is why this particular study is interesting.  The reason why vitamin K  was proposed is actually based on animal studies.  Animal studies have shown that if you can enhance vitamin K you can slow down the rate of calcification in the arteries in animal models,  so there's a good basis for thinking this might work.  The other reason why it seems to be a good idea is because there are low vitamin K levels in patients who have chronic kidney disease and, therefore, boosting them should have a good effect.

Kat - Tell me a bit more about this trial?  Is it a particularly large trial - why is this special?

Jeremy - It's not huge, it's I think going to be very good value for money.  It's going to cost less than £300,000, they're going to do 166 patients, they're going to randomise them into taking supplement of vitamin K or a placebo so they don't know which arm they are in of the trial, and what they're going to do, very simply, is to measure aortic stiffness at the beginning of the trial and at the end of it six months later.

Kat - That's how stiff this main artery in the heart is?

Jeremy - Exactly.  The main artery leading to the heart (the aorta) is what they're really measuring the stiffness in which is the major affected artery, but actually other smaller arteries, including those in the heart are affected, which is why it's dangerous.  Stiffening of the arteries puts more work on the heart, hence the excess cardiovascular risk. 

Kat - Can people not get this from their diet?  Why do we have to supplement ?

Jeremy - You can get vitamin K in the diet but, in fact, most people, particularly middle aged or elderly people, don't get enough in their diet and so supplementation would raise the levels to the levels at which we recommended.

Kat - So we're not going to see people being given vitamin K supplements any time soon and you wouldn't recommend people go out and start taking them?

Jeremy - I don't think we can recommend that at the moment.  It's pretty clear that if, for any reason in a G.P. consultation it turns out that you have low vitamin K levels, your doctor may well suggest vitamin K supplementation just to bring it back to normal levels on the grounds that that would be a good thing for your general health, but I don't think we've yet got to the stage where we're going to recommend this for treatment for chronic kidney disease patients but, hopefully, the results of this trial will be a step in the right direction.  That would be great because vitamin K supplementation is cheap and easy and acceptable to the public.  In patients with chronic kidney disease, their death rate from coronary heart disease or a stroke is somewhere between two and eight times higher than in the general population with the same sort of risk factors like high cholesterol or high blood pressure.

Kat - So I guess there's quite a good basis to try and bring that down?

Jeremy - Yes, that's why there's a real urgency to try and do something about this disease which, until now, we haven't had any very successful treatments for.