Why a Gene Mutation Makes Mice Obese Mutation stops hormone signals getting to brain By Mark Russell, Newser Staff Posted Mar 19, 2012 8:27 AM CDT 0 comments Comments White mice at an animal laboratory of a medical school on February 16, 2008 in Chongqing Municipality, China. (Getty Images) (Newser) – Scientists have discovered why an obesity-linked genetic mutation causes mice to overeat, leading to hopes the discovery could ultimately produce to new ways to fight fat, reports the BBC. After eating, hormones like leptin and insulin are supposed to let the brain know that we're full, and can stop eating. But this mutation prevented mice from getting the message; they ate as much as 80% more food than normal. And now researchers know why. "If there is a problem with the BDNF gene, neurons can't talk to each other, and the leptin and insulin signals are ineffective, and appetite is not modified," said one of the scientists. The hope now is that finding drugs that affect the BDNF gene "may open up novel strategies to help the brain control body weight." But don't get too excited: One genetics and obesity expert not associated with the study notes that this specific mutation is rarely seen in humans.