Discovery could cut heart risk for diabetics

A team of vascular biologists at Leeds University have discovered that a naturally occurring substance known as C-peptide protects blood vessels from the harmful effects of insulin – a finding that could revolutionise the way patients are treated.

Lead researcher Karen Porter, of the Leeds Institute of Genetics, Health and Therapeutics, said: "The hormone insulin is given to diabetes patients to control blood sugar levels but over time it can cause the vessels that supply blood to the heart to become blocked.

"As a consequence people with diabetes are more prone to heart attacks and even if they undergo a heart bypass operation the new veins grafted into the heart are more likely to become blocked, leading to further damage.

"We found that administering insulin with C-peptide – which is released naturally in partnership with insulin in healthy people – appears to protect blood vessels against this damage."

The researchers found insulin on its own causes some cells in blood vessels to grow more than they should, which would lead to narrowing of the passageway used by the blood to get to the heart.

When C-peptide was given along with insulin, as happens in normal people who release both together, the excessive growth and movement of cells was completely stopped.

"It used to be thought that the C-peptide had no function and therefore it was not incorporated in man-made replacement insulin, but our work indicates this is not the case," said Dr Porter.

"Patients with diabetes are known to have higher cardiovascular risk and some will require coronary artery bypass grafting, using a vein from the leg.

"Patients donated leg veins, left over after their operations, for research and we found that insulin on its own caused the cells lining these veins to go into 'over-drive', with increased growth and movement that we know contribute to blockages.

"We were really surprised as to how powerful C-peptide was – it completely took away this insulin effect."

Around 2.5 million people in the UK have Type 2 diabetes. The more common form of the disease, associated with obesity and a sedentary lifestyle, results in the pancreas overworking and eventually failing. These patients will require insulin therapy over time.

In those diagnosed with Type 1 diabetes, insulin therapy is needed at a much earlier stage.

Dr Porter added: "The number of people affected by diabetes each year indicates this is a problem that is not going away. Patients can generally learn to manage and live with their diabetes but heart disease is a complication of diabetes that kills.

"Our work suggests that a combination of insulin and its partner C-peptide may provide a more effective treatment than insulin alone in controlling some of the cardiovascular complications associated with diabetes."

The study is published today in Diabetologia, the journal of the European Association for the Study of Diabetes.

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