Diabetes News:

Study: Gene Associated With Type 2 Diabetes Identified

Diabetic or obese patients in the advanced stages of heart failure have higher levels of fat embedded in their hearts, according to a study reported in the in the November issue of the Federation of American Societies for Experimental Biology Journal.

Study co-author Heinrich Taegtmeyer, MD, of the University of Texas Medical School at Houston said the findings show that fat buildup does not stop in blood vessel, but is actually worse in heart muscle cells.

The researchers examined 27 failing hearts that were removed during transplants and compared them to eight donor hearts unsuitable for transplant. Eight or 30 percent of the failing hearts showed high levels of triglycerides. Levels of triglycerides in failing hearts were four times the level in obese or diabetic patients as they were in non-failing hearts.

The research team associated this buildup of triglycerides in the heart muscle, called lipotoxicity, with dysfunctional expression of genes related to the heart's metabolism of fatty acids, its contractile function, and an inflammatory protein known to contribute to insulin resistance.

Lipotoxic hearts store some triglycerides in the muscle tissue rather than metabolizing them. A normal heart derives two-thirds of its energy requirement by metabolizing fatty acids, which are carried in triglycerides, said study co-author Saumya Sharma, M.D., a cardiology fellow and researcher in Taegtmeyer's lab.

Obese people had much higher levels of triglycerides in their failing hearts, theorized the researchers, because their fat cells, which capture and store excess triglycerides, fill up. Since people have a set number of fat cells, once they are full, excess fat lodges in muscle tissue, where it wreaks molecular havoc, the researchers noted.

"The heart is a muscle, too, and it's not spared from this onslaught of fat," Taegtmeyer explained. "The heart is designed to contract, but if lipids (fat) displace its contractile proteins, that results in impaired heart function."

The researchers are testing this hypothesis among obese patients who have elected to have obesity surgery in which their stomach size is reduced.

Source: Diabetes Week staff, November 6, 2004