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Why walking, jogging and swimming are good for diabetic hearts

Kathleen Blanchard's picture
Researchers uncover why exercise is so good for type 2 diabetic hearts

Type 2 diabetes is a known risk factor for heart failure, especially for those who have difficulty controlling their blood sugar. A new study sheds light on how aerobic exercise like walking, jogging and swimming can counteract the effect of too much glucose to help keep the heart healthy.

Fatty acids released during exercise improve heart function

The study, published in the journal Diabetes, looked at the effect of exercise in a mouse model of type 2 diabetes and energy exchange inside the heart cells; comparing what happens during exercise to normal hearts.

Johns Hopkins scientist who conducted the study found that fatty acids released during exercise counteracts the negative effect of high glucose and improves the pumping ability of diabetic hearts.

Miguel Aon, Ph.D., assistant professor of medicine at the Johns Hopkins University School of Medicine and a senior author of the study article said in a press release, "It has been commonly assumed that fatty acids were detrimental to heart muscle function, but our study showed the opposite to be true in the diabetic heart."

For their investigation, the researchers ‘fed’ diabetic and normal mouse heart cells glucose and then stimulated the heart with a drug that makes the heart beat faster.

As suspected, the diabetic hearts couldn’t keep up with the high glucose load, but the normal hearts could.

Next the researchers added high levels of fatty acids to the diabetic and normal hearts.

We found that the function of the normal heart did not change, but to our surprise, the diabetic hearts improved to the level of the normal hearts," says Nazareno Paolocci, M.D., Ph.D., assistant professor of medicine at the Johns Hopkins University School of Medicine and co-author of the study.

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Fatty acids appear to improve energy exchange in the heart, helping the heart resist the negative effects of free radicals that can kill cells in high amounts.

Exercise is known to be good for type 2 diabetics because it helps mobilize stored fatty acids that accumulate inside of cells, Brisk walking, jogging and other aerobic activity helps lower the risk of diabetes.

The study also showed why people with type 2 diabetes are more prone to developing heart failure.

"Over time, if the heart muscle is not receiving enough energy, the mechanical and electrical functions required to produce a normal heartbeat become impaired, which leads to cardiomyopathy," says Aon.

"In our study, we were able to show a cause-and-effect relationship between dysfunction of the mitochondria -- the energy-producing components of cells -- and the heart's mechanical and electrical functions, which helps to explain why people with type 2 diabetes develop cardiomyopathy," he says.

The scientists also found that when they added the antioxidant glutathione to the diabetic mouse heart cells they were able to improve mechanical function of the heart. Exposing the cells to fatty acids also naturally raised glutathione levels, which could be a new treatment for type 2 diabetes.

The researchers hope that understanding why aerobic exercise is especially beneficial for diabetic hearts could lead to ways to prevent heart failure, especially for diabetics who have trouble keeping their glucose levels under control.

Johns Hopkins News
July 17, 2012

Image credit: Morguefile