Scientists have identified a chain of chemical reactions that begins with one gene and prompts the body to absorb fat.
Finding a drug that interferes with this gene could allow people to decrease the amount of fat their bodies take in from the food they eat.
"In [the] early history of mammals and man, this was a crucial molecule because one had to absorb as much fat as possible and store it because food was very scarce," said study researcher Bert O'Malley, of Baylor College of Medicine in Houston.
"Nowadays, when you can buy food on every corner, and fast food everywhere … this pathway, which is very efficient, is working against us, because it really leads to increased fat absorption and storage," he said.
The study appears in the January issue of the journal Cell Metabolism.
The pathway kicks in when a cell has depleted its energy supply. Low energy levels activate a gene called SRC-2, the researchers found. This gene, in turn, activates other genes that trigger bile production in the liver.
Bile then moves into the intestines, where it emulsifies fat into particles tiny enough to move through the wall of the intestine and into the bloodstream, O'Malley said.
The fat, rich in calories, can then be turned into energy for the body's cells. The process occurs daily, whenever energy runs low.
When O'Malley and his colleagues deleted the SRC-2 gene from mice, they found the mice were unable to absorb fat properly. They ate just as much food as normal mice, but were thinner. The fat seemed to pass through them — they had higher levels of triglycerides, a type of fat, in their feces, and lower levels of triglycerides in their blood than mice with a normal SRC-2 gene.
The researchers also found that adding bile to the intestine restored the ability of these mice to take up fat — further evidence that this mechanism was at work in the slimmed-down mice.
O'Malley and his colleagues are now investigating ways to inhibit this pathway.
"There is a hope that now we know this molecule exists and works like this, that we could find some way or some drug to dampen the activity of SRC-2," O'Malley said.
While the studies were conducted in mice, there is reason to believe the same pathway is at work in people, O'Malley said. The researchers have studied human liver cells and found the pathway seems to work the same way. In addition, scientists know other components of the pathway function similarly in people — bile is secreted by the liver to prompt fat absorption in the intestine.
In the future, the researchers may try to identify people with mutations in the SRC-2 gene to see if they are less able to absorb fat, O'Malley said.
Pass it on: Scientists have discovered a chain of events occurring inside cells that control the amount of fat the body takes up.
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