EAST LANSING, Mich. -- Scientists know that a number of factors can affect the body's immune system: poor diet, certain steroids, chronic stress. Now researchers at Michigan State University have discovered that an appetite-controlling hormone also affects the immune system, while natural versions of certain steroids do not.
Both studies are reported in this week's online edition of the Proceedings of the National Academy of Sciences.
"These two studies, while not directly related, show that the neuroendocrine system plays a big role in both the immune system and obesity," said Pamela Fraker, MSU professor of biochemistry and molecular biology and lead scientist for both projects. "MSU is one of the few places studying the relationship between metabolism, the immune system and the neuroendocrine system."
A new role for leptin
One MSU research team discovered that leptin, a hormone produced by fat cells, supports white blood cell production in the body, enhancing immune function. This is the first time leptin's effect on the immune system has been demonstrated.
Scientists have long known that leptin helps control how much a person eats as well as how quickly the body burns energy.
"Many investigators have been trying to unlock the key to obesity for years," said Fraker. "The more fat a person has, the more leptin there is in the bloodstream. In obese people, it seems that the body becomes leptin-resistant -- the signals get jammed. So giving obese people leptin doesn't help them lose weight."
The MSU scientists were examining ob/ob mice (genetically programmed to have non-functional leptin) and db/db mice (genetically programmed to have non-functional leptin receptors), giving them supplemental leptin to study its effects. While causing the mice to eat less, the big surprise was leptin's effect on the immune system. The mice that were given leptin had double the number of B cells, a type of white
|Contact: Pam Fraker|
Michigan State University