Research team discovers hunger-inducing hormone in obese individuals

A research team that includes a University of Western Ontario researcher has discovered that being obese can lead to further obesity.

Kaiping Yang, a professor in The Schulich School of Medicine & Dentistry’s Departments of Obstetrics & Gynaecology and Physiology and Pharmacology says that the discovery that abdominal fat tissue can reproduce a hormone that stimulates fat cell production may lead to changes in the way we think about and treat abdominal obesity.

Yang and fellow researchers at the Lawson Health Research Institute have identified that the hormone Neuropeptide Y (NPY) is reproduced by abdominal fat tissue. It was previously thought that this hormone was only produced by the brain. The traditional view is that one of the main reasons why overweight people eat more food is because their brains produce the hormone NPY in excessive amounts. NPY is the most potent appetite stimulating hormone known, sending signals to the individual that they are constantly hungry. However Yang has provided evidence that in obese rat models NPY is also produced locally by abdominal fat.

"Being overweight, regardless of where the fat is located, is unhealthy. However, because of its anatomical location and its byproducts, abdominal fat or the apple-shape is known to be the most dangerous. People predisposed to the apple shape are at an elevated risk for heart disease, Type 2 diabetes, hypertension and some cancers.The researchers will next be investigating whether NPY produced by fat is released into the body’s circulatory system. "We want to know if NPY could potentially be transported in the blood to the brain where it in turn has an impact on the brain to stimulate feelings of hunger," says Yang.

If the researchers find that NPY is in fact transported in the blood circulation then it may be possible to develop a simple blood test to detect increased levels of NPY.

According to Dr. Yang, "If you can detect NPY early and identify those at risk for abdominal obesity we can then target therapy to turn off NPY…It is much easier to use drugs to target fat than target the end diseases of fat. By then the diseases are more serious and have already begun to do damage to the body’s organs."

There is very little known about the incidence of abdominal obesity in Canada or elsewhere, but it is likely more prevalent then general obesity. The fact that some people may be born with a greater tendency to gain weight and will have to work harder to lose this weight may be an "unfortunate product of our biology," says Yang.

(Source: University of Western Ontario: April 2008)