Research explains why piglets shudder to keep warm18 August 2006
SWEDEN - Researchers at Uppsala University, Sweden, have uncovered a genetic reason why newborn piglets are less tolerant to cold than other newborn mammals, reports the NPA. It turns out that the gene that codes for the protein UCP1 was inactivated some 20 million years ago in the evolutionary line that pigs belong to.
Brown fat plays an important role in newborn mammals, including our own children, since this tissue helps the newborn to maintain its body temperature by burning fat, which converts into heat. The protein UCP1 (Uncoupling Protein 1) has a key role in this energy conversion, which takes place in the cell mitochondria.
Piglets are sensitive to cold and shudder in order to maintain their body heat. No brown fat or UCP1 protein has previously been found in domesticated pigs. In a new study, Frida Berg and her colleagues have been able to show that the UCP1 gene was shut down about 20 million years ago in an ancestor of the wild boar. These scientists have found four different mutations, each of which would be sufficient to knock out the function of the protein.
“This ancestor of pigs thereby lost the ability to use brown fat to maintain body temperature after birth. A reasonable explanation for this is that brown fat was not essential during a period in the evolution of pigs, when it lived in a warm climate,” says Leif Andersson, who directs the research team.
The ancestor of the domesticated pig, the wild boar, is the only pig that lives in cold climates. All other species, such as the wart hog, live in tropical or subtropical climates. The wild boar has compensated for the loss of brown fat by a series of adaptations for survival in a cold climate.
The findings show that an important biological function can be lost if it is not vital to life during a period in the evolutionary history of a species, and that if the living conditions once again change, compensatory mechanisms can be developed. The lack of UCP1 and brown fat in the pig resembles the inability of humans to produce vitamin C, a feature we lost during our evolutionary history.
For more information on the research see: dx.doi.org/10.1371/journal.pgen.0020129