A new form of “ultrabad” cholesterol that increases the risk of heart disease has been identified.
The fatty material is stickier than normal “bad” cholesterol, making it more likely to attach to artery walls.
It is especially common in people with the most common form of type 2 diabetes and the elderly.
Harmful cholesterol, or low-density lipoprotein (LDL), helps create the fatty plaque deposits in arteries that can lead to heart attacks and strokes.
The new type of cholesterol, called MGmin-LDL, has sugary molecules that are smaller and denser than those of normal LDL.
Its altered shape exposes regions that readily stick to artery walls, providing a starting point for the build-up of plaques.
As the deposits grow they narrow arteries and reduce blood flow. Eventually they can rupture, triggering a blood clot that causes a heart attack or stroke.
The discovery, made by scientists at the University of Warwick, may explain why the widely prescribed diabetes drug metformin appears to reduce heart attack risk.
Metformin is known to lower blood sugar levels, and may block the transformation of “normal” LDL into stickier MGmin-LDL.
The research is reported in the journal Diabetes.
Study leader Naila Rabbani said: “We’re excited to see our research leading to a greater understanding of this type of cholesterol, which seems to help cause heart disease in diabetics and elderly people.
“Type 2 diabetes is a big issue – of the 2.6 million diabetics in the UK, around 90 per cent have type 2. It’s also particularly common in lower income groups and South Asian communities.
“The next challenge is to tackle this more dangerous type of cholesterol with treatments that could help neutralise its harmful effects on patients’ arteries.”
Dr Rabbani’s team reproduced the way MGmin-LDL is created by isolating and modifying normal LDL cholesterol in the laboratory.
They showed how LDL was transformed by the addition of extra sugar groups.
Shannon Amoils, research adviser at the British Heart Foundation, which funded the study, said: “We’ve known for a long time that people with diabetes are at greater risk of heart attack and stroke.
“There is still more work to be done to untangle why this is the case, but this study is an important step in the right direction.
“This study shows how the make-up and the shape of a type of LDL cholesterol found in diabetics could make it more harmful than other types of LDL.
“The findings provide one possible explanation for the increased risk of coronary heart disease in people with diabetes.
“Understanding exactly how ‘ultrabad’ LDL damages arteries is crucial, as this knowledge could help develop new anti-cholesterol treatments for patients.”