14 March 2007

The Skinny On Bad Fat

by Kate Melville

The role that inflammation plays in diabetes, heart disease and other disorders is a hot topic in medical research these days. The recent finding that poor oral health contributes to cardiovascular risk underscores the complex interplay of our bodily systems. Now, researchers from the Washington University School of Medicine in St. Louis (WU) have obtained the first evidence of a potential mechanistic link between abdominal fat and systemic inflammation.

But it's not just any old belly fat that causes inflammation. This became apparent back in 2004, when WU researchers found that removing abdominal fat with liposuction did not provide the metabolic benefits normally associated with similar amounts of fat loss induced by dieting or exercising. "Despite removing large amounts of subcutaneous fat from beneath the skin - about 20 percent of a person's total body fat mass - there were no beneficial medical effects," said Samuel Klein, the senior investigator in both studies.

To investigate further, the new study focused on visceral fat - the fat that surrounds the organs in the gut. Unlike subcutaneous fat, visceral fat is not easy to remove surgically because it is surrounded by the intestines and other internal organs. However, analyzing the blood that ran through the visceral fat, the researchers found that it was rich with an important inflammatory molecule called interleukin-6 (IL-6). "[The] blood had levels of IL-6 that were 50 percent higher than blood from the periphery," said co-researcher Luigi Fontana.

The high levels of IL-6 correlated with concentrations of an inflammatory substance called C-reactive protein (CRP) in the body. High CRP levels are related to inflammation, and chronic inflammation is associated with insulin resistance, hypertension, type 2 diabetes and atherosclerosis, among other things. "These data support the notion that visceral fat produces inflammatory cytokines that contribute to insulin resistance and cardiovascular disease," said Klein.

Fontana added that the findings help explain how visceral fat can lead to inflammation, insulin resistance and other metabolic problems. And by contributing to inflammation, visceral fat cells in the abdomen may be doing even more than that. "Many years ago, atherosclerosis was thought to be related to lipids and to the excessive deposit of cholesterol in the arteries," he explained. "Nowadays, it's clear that atherosclerosis is an inflammatory disease. There also is evidence that inflammation plays a role in cancer, and there is even evidence that it plays a role in aging."

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Source: Washington University School of Medicine