Sweet remedy

A protein, a by-product of natural insulin production, reduces heart complications in diabetics.  Reports on the outcome of a new study :-

Doctors have known for a long time that diabetes is one of the major risk factors for heart disease. If uncontrolled sugar levels persist for long, the blood vessels can become leaky. Such a condition allows cholesterol to seep in. And when cholesterol builds up inside the arterial blood vessels, they thicken from inside, reducing and eventually blocking the blood flow, leading to atherosclerosis.

Thanks to sustained campaigning over the years, most people now know that diabetes is also bad for the heart.

However, what many people do not know is that an inadvertent fallout of certain treatment methods can be detrimental to the heart’s functioning. A case in point is insulin therapy. One of the last resorts in diabetes management, the hormone insulin is administered either through a subcutaneous injection or by using a self-controlling pump attached to the body.

But this externally supplied insulin, for reasons not yet known, causes some cells in the blood vessels to grow more than they should, leading to a narrowing of their passageway to the heart.

A consequence of this, as some studies have shown, is that diabetics on insulin who have undergone bypass surgery are likely to have their newly grafted veins blocked earlier than non-diabetic heart patients.

But now a team of vascular biologists at the University of Leeds in the UK has found that a small protein, which was long thought to have been a useless by-product of natural insulin production in the pancreas, can ameliorate this undesirable side effect of insulin treatment.

Led by Karen Porter of the Leeds Institute of Genetics, Health and Therapeutics (Light), the researchers found that C-peptide, a natural by-product of insulin production, has a role to play in nature’s scheme of things and hence is not as “useless” as it is made out to be.

When C-peptide was given along with insulin, as happens in normal people who are not diabetic, the excessive growth and movement of cells was completely stopped, they report in the latest issue of the journal Diabetologia. “We found that administering insulin with C-peptide — which is released naturally in partnership with insulin in healthy people — appears to protect blood vessels from this damage,” says Porter.

Though insulin has been in use as medication since the 1930s, research till very recently failed to ascribe any role to C-peptide, insulin’s natural “partner”.

As a result, it was never incorporated in externally supplied insulin. In the 1970s though, some scientists briefly wondered if diabetics might be suffering from a lack of C-peptide. Subsequent studies, however, didn’t help much as they failed to ascertain any beneficial effect.

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For instance, a study in 1993 by Julio Santiago of the Washington University who injected diabetic patients with low levels of the protein — just enough to match normal levels — saw no effect.

“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 these 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 an overdrive, 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,” explains Porter.

“The study shows us a new path, wherein thickening of arteries — which is sometimes induced by insulin itself — could be decreased by giving C-peptide. This has huge relevance for the treatment of heart disease in patients with diabetes,” says Anoop Misra, head of internal medicine at New Delhi’s Fortis Hospital.

However, Nihal Thomas, an endocrinologist at the Christian Medical College, Vellore, says the idea that an additional peptide may augment the action of insulin is not entirely new. Previous studies with peptides such as IGF1 (insulin-like growth factor-1) and GLP-1 (glucagon-like peptide- type 1) have shown similar benefits.

Moreover, the mechanism works at a cellular level in laboratory studies. “It needs to be established over a period of time through extensive human clinical trials to assess its clinical viability,” he adds.

But if the trials were to become successful in the next few years, a large number of diabetics all over the world will benefit from it.

It will be especially welcome in India, which is home to more than 40 million Type 2 diabetic patients.

This more common form of diabetes, associated with obesity and a sedentary lifestyle, results in the pancreas overworking and eventually failing. These patients will require insulin therapy over time. For instance, some 5 per cent of Indian diabetics are on insulin. Those suffering from Type 1 diabetes need insulin therapy at a much earlier stage.

“The number of people affected by diabetes each year indicates the problem is here to stay. Patients can generally learn to manage and live with their diabetes but heart disease is a complication that kills,” says Porter.

As has been shown by the Light researchers, a combination of insulin and C-peptide may provide a more effective treatment than insulin alone in controlling some of the cardiovascular complications associated with diabetes.

Source:
The Telegraph ( Kolkata, India)

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