Diabetes, Heart and Exercise
- October 2007
Thomas L. Broderick, PhD

Several clinical studies have shown that diabetic patients are more prone to develop heart diseases such as angina pectoris, heart attack, and heart failure.

The severity of these diseases is also increased in the diabetic patient. For instance, once a heart attack occurs, the diabetic patient has an increased hospital stay and more complications than a non-diabetic patient.

Studies have linked these complications to atherosclerosis or narrowing of the coronary arteries and to progressive nerve and blood vessel disease. Recent research into the causes has revealed that disturbances in energy production in the heart may be another culprit. Typically, in a healthy heart, energy for contraction comes from the breakdown of both carbohydrates (as sugars) and fats. In fact, under normal conditions, sugar provides about 30 percent of the energy with the remaining70 percent coming from the breakdown of fats.

This is accomplished with normal insulin levels in the blood along with healthy active muscles.

In poorly controlled diabetic patients and in several experimental animal models, the breakdown of sugar by the heart for energy can be extremely low. When this occurs, the heart rapidly adapts by using more fats. Essentially, the normal pattern of energy metabolism of the heart can be shifted by the diabetic state and, in some cases, the heart can rely almost entirely on fats for a source of energy.

This change in the energy pattern is considered to be another contributing cause to the development of poor heart function and heart failure in diabetes. Evidence for the role of altered energy production in diabetes is supported by the use of novel pharmacological agents known as metabolic modulators.

These drugs, which are still at various stages in clinical trials, have the ability to change the energy pattern such that more sugars and less fat are used by the heart. Heart function with these metabolic modulators is usually improved.