Have researchers found the ‘fattening gene’?

Collaborating German and Japanese scientists have studied mice lacking a gene that plays a central role in energy metabolism. Their findings? The mice maintain their normal weight, despite consuming foods high in fats.

"We established that Sirt7-knockout mice put on significantly less weight than the control group. On the contrary, they maintained their normal weight," says Eva Bober, a scientist at the Max Planck Institute for Heart and Lung Research.

To investigate the molecular processes behind this observation, the scientists studied the gene activities of the liver cells and determined that Sirt7 activates the expression of a large number of genes for lipid metabolism. The liver cells of mice lacking the gene were largely unactivated, so fewer fat depots formed as a result.

Microscope images show the liver tissue of control animals (left) and mice that lack the SIRT7 gene magnified by a factor of 400. Whereas the control animals form large numbers of fat depots when fed a high-fat diet, the SIRT7-knockout mice do not develop fatty liver. [Photo: Max Planck institute]

"We discovered a second mechanism as well," says Bober. "Sirt7 also inhibits the degradation of certain proteins. Because they are then active for longer, these proteins also make a greater contribution to energy storage than is actually intended."