A team of scientists from the University of Wisconsin-Madison reports that a gene in the liver, called SCD-1, is what causes mice to gain weight on a diet laden with carbohydrates. The gene encodes the enzyme SCD whose job is to synthesize fatty acids.
The current study builds on previous work, in which mice were created that lacked SCD-1 everywhere in the body, including the liver, muscle, brain, pancreas, and adipose tissue. No matter how much they ate, the mice didn’t gain weight on either a high-fat or a high-carbohydrate diet.
“But it was very difficult to tell which tissue was responsible for the effect,” says team leader, James Ntambi, Ph.D., professor of biochemistry and nutritional sciences.
To tease this out, the investigators subsequently bred mice that lacked SCD-1 in the liver only and placed them on either a high-fat diet or a high-carbohydrate, low-fat one.
To their surprise, the mice on the high-fat diet gained weight just as quickly as control mice. In contrast, the mutant mice stayed thin when they feasted on food heavy in starch and sucrose. They were also protected from the condition known as fatty liver.
“It looks to us that if you don’t have enough oleic acid, which the SCD enzyme makes, then the carbohydrate does not proceed through normal glucose metabolism,” says Dr. Ntambi. As further evidence of this, when the scientists supplemented the mouse diets with oleic acid, normal metabolism was restored.
The study is published in the December issue of Cell Metabolism.