Yifan Dai of the University of Pittsburgh and his colleagues first transferred the roundworm gene--fat-1--to pig fetal cells. Randy Prather of the University of Missouri and his collaborators then cloned those cells and transferred them into 14 pig mothers. Twelve pigs were subsequently born and six of them tested positive for the gene and its ability to synthesize omega-3 fatty acids.
Numerous studies have shown that omega-3 fatty acids protect against heart disease. But meat from cows, pigs and other mammals typically has higher levels of omega-6 fatty acids, thanks to a feedlot diet of grains rich in the fat and an inability to transform it into its healthier version. For example, typical pork meat contains roughly 15 percent omega-6 fatty acids and only 1 percent omega-3; in contrast, omega-3s made up 8 percent of the engineered pigs' total muscle fat.
The six piglets appeared normal at birth though three subsequently had to be killed because of heart defects. These defects appear to be a result of the cloning process rather than the introduced gene, considering that team member Jing Kang of Harvard University has been able to breed and raise multiple generations of the mice without any such defects. And another litter of eight piglets cloned from one of the pigs that perished proved healthier and nearly as omega-3 rich, the researchers revealed in the paper presenting their findings, published online yesterday in Nature Biotechnology.
The research opens the possibility of a new model organism for human heart health and the distant prospect of incorporating such a gene into humans. "Pigs and humans have similar physiology," Prather explains. "We could use these animals as a model to see what happens to heart health if we increase the omega-3 levels in the body." It also provides a potential alternate food source for omega-3 fatty acids other than dwindling--and mercury-tainted--fish stocks.