Sun Mar 26, 1:15 PM ET
PARIS (AFP) - Researchers say they have created cloned piglets that are rich in omega-3 fatty acids, the oil that is prized as being beneficial to the heart.
Omega-3 is mostly found in fish, but this supply is threatened by overtrawling and clouded by worries about mercury pollution, which accumulates in fish livers.
A team led by Yifan Dai of the University of Pittsburgh's School of Medicine transferred into foetal pig cells a gene called fat-1 that had been identified in a well-studied lab animal, a tiny worm known as Caenorhabditis elegans.
Fat-1 converts the abundant but less desirable omega-6 fatty acids into the coveted omega-3.
The nucleus of pig eggs was then removed and substituted with the nucleus from these engineered cells, following the now-classic method of animal cloning that began with Dolly the Sheep in 1996.
The research's prime aim is to gain a better understanding of cardiac function, where hog and human are strikingly similar, the team reports on Sunday in the specialist journal Nature Biotechnology.
"We would use these animals as a model to see what happens to heart health if we increase the omega-3 levels in the body. It could allow us to see how that helps cardiovascular function," said co-author Randy Prather, a specialist of the University of Missouri at Columbia.
Given that the animals are experimental -- not to say extraordinarily expensive -- no one knows what their meat tastes like, whether it is safe to eat and whether the piglets will retain high levels of omega-3 when they reach adulthood.
If, eventually, the transgenic hogs go to market, there could be double benefits, argued Prather.
"First, the pigs could have better cardiovascular function and therefore live longer, which would limit livestock loss for farmers. Second, they could be healthier animals for human consumption."
Genetic manipulation of animals and plants for agricultural purposes is fiercely opposed by environmentalists as being potentially dangerous to health and the ecology.
Their concerns are shared by many experts, who urge extensive testing to obey the so-called precautionary principle when introducing novel technology.
Animal cloning, with the present technology, also results in many failures, as shown in Dolly's premature demise in 2003.
The endeavour to create the world's first omega-3 pig entailed the creation of 1,633 cloned embryos, which were implanted into 14 sows.
Only 12 pregnancies resulted, of which five came to term, delivering just 10 live piglets and two dead ones.
Of the 10 survivors, only six had the fat-1 gene -- and three (including two with fat-1) had a heart defect and had to be killed at the age of three weeks.
The demand for omega-3 has surged in recent years because of their deemed benefits in cardiovascular disease, rheumatoid arthritis and diabetes.
But a review of the evidence, published on Saturday in the British Medical Journal (BMJ), casts doubt on this.
It looked at 89 studies into omega-3, and said there was concern that people who have angina might suffer a higher risk of a fatal heart attack by taking supplements of the oil.
In 2002, Prather's team created pigs designed to produce organs that were more suitable for transplantation into humans.
Pig organs are coated with sugar molecules that trigger acute rejection by the human immune system. The modified piglets lacked one of the two copies of the sugar-making gene, thus marking an important experimental step towards so-called xenotransplantation.