US scientists have discovered how fat is stored in the body's cells - promising new treatments for obesity.
They have uncovered the two genes which control the packaging of fat inside a layer of phospholipids and proteins to form liquid droplets.
The process is thought to be crucial for enabling cells to use fat as an energy source, but if too much fat is stored obesity results.
The work appears in Proceedings of the National Academy of Sciences.
"Now that we've identified the genes and the proteins they code for, it should be possible to develop drugs that can regulate their expression or activity"
The researchers, from the Albert Einstein College of Medicine, Yeshiva University, carried out a series of experiments to confirm the role of the genes - dubbed FIT1 and FIT2 - in fat storage.
In one they inserted extra copies of the genes into human cells. While this had no impact on fat synthesis, the number of lipid droplets created in the cells soared by up to six-fold.
In a second experiment, the researchers knocked out FIT2 in mouse fat cells. This led to a drastic reduction in droplets.
Whole animal experiment
Finally, to test the effects on a whole animal, the Yeshiva team injected zebrafish eggs with a segment of DNA designed to interfere wth FIT2 expression.
The resulting larvae were fed on a high-fat diet for six hours to try to induce lipid droplet formation.
But an examination of their livers and intestines revealed a near-absence of droplets.
"This is a very interesting study, which adds weight to the notion that a large part of our risk of becoming obese is genetic"
Lead researcher Dr David Silver said: "These lines of evidence supported our conclusion that FIT genes are necessary for the accumulation of lipid droplets in cells.
"Now that we've identified the genes and the proteins they code for, it should be possible to develop drugs that can regulate their expression or activity.
"Such drugs could prove extremely valuable, not only for treating the main result of excess lipid droplet accumulation - obesity -but for alleviating the serious disorders that arise from obesity including type 2 diabetes and heart disease."
Dr Ian Campbell, medical director of the charity Weight Concern, said: "This is a very interesting study, which adds weight to the notion that a large part of our risk of becoming obese is genetic."
"Obesity is clearly not all the individuals fault. Improving our understanding of how fat is accumulated within the body will help the development of future drug therapies.
"However it's unlikely that any future drug therapies will do away with an individual's need to reduce their energy intake by avoiding high fat foods, and becoming more active."
Douglas Smallwood, of the charity Diabetes UK, said obesity was a major cause of type 2 diabetes.
"The discovery of genes that influence the development of obesity could help us understand why some people gain weight more than others.
"These findings could open up a wealth of new avenues to understand and treat obesity and obesity-related conditions such as type 2 diabetes."
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