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Chewing the Fat

Chewing the Fat
Undeniable organ

January 2006

by Will Sansom

Letís talk about fat.

Our society hates fat. We are constantly seeking to lose weight, fit into that new swimsuit and look better in the mirror. TV puts endless images of the perfect body in front of us. The perfect body never seems to look quite like ours.

But fat itself is not our enemy. In fact, for our bodies to purr like the engine of a sports car, we need a certain percentage of it. Like motor oil, if we have too much or too little fat, nasty problems occur.

Sixty percent of the U.S. population is obese or overweight, according to national health information surveys. In addition, diseases such as type 2 diabetes, heart problems, high blood pressure, stroke, cancer, sleep disorders and depression are increasing at an alarming rate. Obesity has been shown to exacerbate each condition.

Research is showing us that we should be mindful of our fat. "Fat once was thought to be a simple storage organ and not much attention was given to it," says Lily Q. Dong, Ph.D., assistant professor of cellular and structural biology at the Health Science Center. "Now, with a huge proportion of the population having weight issues, understanding fat is seen as the key to solving problems. The bottom line is we have to take care of fat tissue carefully. We have to deal with it as an endocrine organ."

Endocrine organs generate and regulate hormones, which perform a variety of functions in our bodies. You name it, hormones do it. One of the better-known hormones is insulin, the one that is secreted from the pancreas and regulates blood sugar. Insulin action and fat are inextricably linked because hormones secreted from fat have a major impact on the many different tissues that insulin affects - muscle, the liver and the brain, to list a few, Dr. Dong says.

Fat is composed of adipocyte and non-adipocyte cells. Many hormones and proteins are secreted from both types of cells and can behave both malevolently and benevolently. Adiponectin, one of the beneficial hormones, helps insulin to control our blood sugar and has anti-diabetic functions. "The discovery of adiponectin was a quantum leap in the science of fat," Dr. Dong says. "Every single hormone from fat tissue is increased in amount in obesity except adiponectin, so we know it is special," she says. "This potentially therapeutic hormone was discovered only 10 years ago."

She says it has become "an urgent project" to know how this good hormone helps our bodies. Scientists are asking how adiponectin works as an insulin sensitizer. Dr. Dongís lab recently made a finding about APPL1, a protein present in muscle and other insulin target tissues. The researchers pointed out that APPL1 is a link connecting the networks controlled by adiponectin and insulin in cells. The labís work could lead scientists to understand how adiponectin works in cells and provide valuable information for the potential therapeutic application of it. A paper on this work is soon to be published in one of the leading scientific journals.

Dr. Dongís laboratory is supported by a five-year, $1.27 million grant from the National Institute for Diabetes and Digestive and Kidney Diseases, and a five-year, $900,000 grant from the American Diabetes Association. The latter is a highly competitive Career Development Award.

Dr. Dongís husband, Feng Liu, Ph.D., professor of pharmacology at the Health Science Center, says the work is the first to show a mechanism by which adiponectin signaling is transmitted to cells. Like Dr. Dong, he is interested in how insulin and adiponectin talk to each other. "No hormone is an island to itself," Dr. Liu notes.

"I would like the public to be conscious of the risks of obesity," Dr. Dong says. "Watch your diet and stay healthy. Excessive body fat results in a decrease in the amount of beneficial hormones, like adiponectin, and in sugar and lipid dysregulation, leading to metabolic diseases such as diabetes. Ten percent of our health dollars are going to this single disease (diabetes). Thatís larger than any single cancer."

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