Tens of millions of people from the Indian subcontinent are destined to suffer heart disease because of a single genetic mutation, a study published yesterday said.
The wayward gene, found almost exclusively among the more than 1.5 billion people in or from South Asia, is almost guaranteed to lead to heart trouble, usually later in life, the researchers reported.
Four percent of the region’s population — some 60 million people — carry the mutation, the study concluded.
Scientists have long suspected that India, Pakistan, Sri Lanka and probably Bangladesh carry an outsized share of the global burden of health disease.
One recent study predicts that by the end of this year India alone will account for 60 percent of the world’s heart-related problems, which can have both lifestyle and genetic origins.
The new research by an international team of 25 scientists and doctors from four countries provides a partial answer as to why this is so: An unexpectedly common defect in a gene, MYBPC3, provides the blueprint for a certain kind of heart protein.
“The mutation leads to the formation of an abnormal protein,” said the study’s main architect, Kumarasamy Thangaraj of the Centre for Cellular and Molecular Biology in Hyderabad, India. “Young people can degrade the abnormal protein and remain healthy, but as they get older it builds up and eventually results in the symptoms that we see.”
These include severe hypertension, an inflammation and weakening of the heart called cardiomyopathy, and death because of sudden cardiac arrest.
Thangaraj and colleagues first discovered the mutation — the deletion of 25 bits of genetic code — five years ago in two Indian families. But its significance only came to light with the new research.
In two separate clinical tests, researchers checked for the presence of the variant in 800 heart patients and 699 healthy individuals across India. The link between the symptoms and the genetic defect “were almost off the scale,” leaving no doubt that the mutation played a key role in causing heart disease.
Further tests in different parts of the country of 28 unrelated families carrying the mutation showed that more than 90 percent of the oldest members in each family had heart problems.
While virtually absent among peoples from other parts of the world, the deadly genetic variant is equally spread across most of India’s regions, its social castes, and its language and religious groups.
In a follow-up sampling of more than 2,000 individuals from 26 countries across five continents, the mutation showed up in Pakistan and Sri Lanka, with some presence in Malaysia and Indonesia, but nowhere else.
The researchers said the findings should lead to better screening to identify those at risk, and may ultimately pave the way for the development of new treatments.