Fat Infiltrates Heart Before Diabetes Onset

Heart tissue gets fatty in people with impaired glucose tolerance long before they show signs of diabetes or heart disease, according to a recent report.

A group of investigators from University of Texas Southwestern Medical Center, Dallas VA Medical Center, and the Institute for Exercise and Environmental Medicine at Presbyterian Hospital in Dallas employed magnetic resonance spectroscopy to measure myocardial triglyceride content in 134 participants.

The subjects were chosen to represent the progressive stages in the natural history of type 2 diabetes: Those who were lean and had normal blood glucose levels; those who were overweight or obese who still had normal blood glucose levels; those who had impaired glucose tolerance; and those with full-blown type 2 diabetes.

Software allowed investigators to determine levels of triglycerides in cardiac muscle cells versus adipocytes. They also measured triglycerides in the liver and subcutaneous and visceral fat. Left ventricular function was measured by cardiac magnetic resonance imaging.

The group found that levels of triglycerides in the cardiac muscle were 2.3 times higher in people with impaired glucose tolerance, compared with lean, normoglycemic people. Triglyceride levels were 2.1 times higher in people with type 2 diabetes, the researchers found. No differences were noted in any group in terms of left ventricular function.

“Impaired glucose tolerance is accompanied by cardiac steatosis, which precedes the onset of type 2 diabetes and left ventricular systolic dysfunction,” the researchers conclude. “Thus, lipid overstorage in human cardiac myocytes is an early manifestation in the pathogenesis of type 2 diabetes mellitus and is evident in the absence of heart failure.”