New MRI Technique Reveals Fat Accumulation in Hearts of Pre-diabetics

A simple imaging technique reveals fat buildup in the hearts of pre-diabetic people long before symptoms of heart disease or diabetes appear.

The modality identifies fat accumulation in cells of the beating heart in a way no other clinical method can, according to the researchers who developed the method, and may provide a way to screen patients for early signs of heart disease in diabetes.

"Hearts beat; people breathe; and magnetic resonance imaging [MRI] is very sensitive to motion, so we had to find a way to electronically ‘freeze' the image of the heart,” said Dr. Lidia Szczepaniak, assistant professor of internal medicine at the University of Texas (UT) Southwestern Medical Center (Dallas, USA) and senior author of a study appearing in the September 4, 2007, issue of the journal Circulation.

Dr. Szczepaniak and her colleagues developed a technique that captures the signal from a beating heart as a person lies in an ordinary magnet used for MRI scanning. The researchers knew that fat builds up in the hearts of people with heart failure or non-insulin-dependent diabetes (type II) from earlier studies involving patients undergoing heart transplants, but they did not know if this fatty buildup occurred before or after the diabetic conditions developed.

In the new study, the UT Southwestern researchers used a conventional magnetic resonance imaging (MRI) system, but added the newly developed computer software to convert the signals from a moving heart into a single image. They looked at lean and obese individuals with normal blood sugar; obese people beginning to show abnormal sugar metabolism, and obese people with full-blown type II diabetes.

Their most significant finding, according to Dr. Dr. Szczepaniak, was that fat accumulation in the heart develops before the onset of diabetes. They also discovered that the amount of fat in the heart of individuals with abnormal sugar metabolism was considerably higher than in those with normal blood sugar, whether obese or lean. The amount of fat in the heart was unrelated to the amount of fat in the bloodstream or liver, indicating that measuring any of those factors could not predict accumulation of fat in the heart. Fat in the heart did correspond to the amount of fat in the stomach region, however.

The researchers recruited some participants from the Dallas Heart Study--a multi-ethnic, population-based study of more than 6,000 patients in Dallas County designed to examine cardiovascular disease. Some researchers, including those at UT Southwestern, believe that as an individual becomes overweight, fat builds up in normal fat cells, but eventually fat cells cannot store fat any more. Ultimately, the excess of fat kills other cells--a theory backed up by a recent study by Dr. Unger in laboratory mice.


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University of Texas Southwestern Medical Center