By Lee Bowman
Scripps Howard News Service
March 28, 2005
The research, published in the April issue of the American Journal of Physiology-Endocrinology and Metabolism, is based on a new theory in medicine that treats fat as an "organ" that produces proteins and hormones that affect metabolism and health.
"It is well known that obesity affects nearly one-third of adults in the United States and is closely-linked with heart disease," said Tongjian You, an instructor in geriatric medicine at Wake Forest University Baptist Medical Center and lead author of the study.
"While we don't fully understand the link, our study suggests that inflammatory proteins produced by fat itself plays a role," You added. Until recently, most research had suggested that being fat was a heart risk factor because it made the heart work harder or was associated with higher cholesterol levels.
But over the past several years, fat and related chemicals have been getting a second look as contributors to artery damage.
Barbara Nicklas, an associate professor of internal medicine at Wake Forest and senior researcher on the study, said the proteins offer new targets in the battle against heart disease. "It's possible that modifying the inflammatory proteins through medication could also lower the risk of heart disease," she said. "Our goal is to learn more about how these proteins are produced and how levels can be changed."
Nicklas and colleagues already have begun a study that will test whether diet and exercise affect levels of the protein. Other research has already shown that weight loss and increased physical activity can reduce inflammation, but hasn't confirmed that this happens because production of the inflammatory proteins by fat tissue is reduced.
The Wake Forest team studied two proteins that promote inflammation and a protein that promotes blood clots. They are involved in the buildup of fatty deposits in the linings of blood vessels.
The team also looked at two other fat-related proteins: leptin, which regulates energy metabolism, and adiponectin, which has anti-inflammatory effects.
The study involved 20 post-menopausal women aged 50 to 70 years old who were overweight or obese, with waists measuring more than 35 inches. Women in this age group are at increased risk for metabolic syndrome, a cluster of symptoms that increases the risk for heart disease - abdominal obesity, high blood pressure, high blood sugar, high triglycerides and low levels of "good" cholesterol.
To measure production of the proteins, the scientists took small samples of fat from the skin around the abdomen and tested levels of messenger RNA, which carried the genetic code instructions for creating the proteins.
Among the 15 women without diabetes, higher levels of two proteins that induce inflammation were associated with a reduced ability to respond to insulin and to use glucose. But higher levels of the "good" protein adiponectin were linked to an increased ability to use glucose.
Eight women who were diagnosed with metabolic syndrome and had several risk factors for heart disease had levels of adiponectin that were 32 percent lower than the 12 women who did not have the syndrome.
"This suggests that low production of adiponectin in subcutaneous fat is linked with an elevated risk of heart disease," You said.
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