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Medicineworld.org: High Blood Pressure Induces Low Fat Metabolism

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High Blood Pressure Induces Low Fat Metabolism

High Blood Pressure Induces Low Fat Metabolism Echocardiograms show that the thickness of left ventricular (LV) walls in the hypertrophied heart (left) are nearly twice that of the normal heart.
"The heart is the single most energy-consuming organ per weight in the body," says Lisa de las Fuentes, M.D.

Under some conditions this energy-hungry organ is prone to defects in its energy metabolism that contribute to heart disease, as per research published in a recent issue of the Journal of Nuclear Cardiology by de las Fuentes and his colleagues at Washington University School of Medicine in St. Louis.

Earlier research led by de las Fuentes' colleague Robert J. Gropler, M.D., showed that heart muscle in people with diabetes is overly dependent on fat for energy. Even though fat is an efficient fuel, burning it for energy creates an uncommonly high demand for oxygen, making the diabetic heart more sensitive to the drops in oxygen levels that occur with coronary artery blockage.

Gropler is director of the Cardiovascular Imaging Laboratory at the Mallinckrodt Institute of Radiology at the School of Medicine and professor of radiology, medicine and biomedical engineering.

Now this group of Washington University scientists has shown that hearts of non-diabetics with muscle thickening due to hypertension have an energy metabolism skewed in the opposite direction - away from the use of fat for energy.

"Whereas Dr. Gropler observed that a high level of fatty acid metabolism could be detrimental, we show that a low level may also be harmful," says de las Fuentes, co-director of the Cardiovascular Imaging and Clinical Research Core Laboratory and assistant professor of medicine. "These findings aren't contradictory. The heart has to be able to choose the energy source, either fats or glucose, most appropriate for its current energy needs and the availability of fuel."

De las Fuentes explains that hearts with muscle thickening, or hypertrophy, get less energy because of their reduced fat metabolism, which leads them to rely more heavily on carbohydrates.

"Carbohydrates produce less energy per molecule than fatty acids," she says. "With hypertrophy, the heart has a higher energy demand because there's more muscle to feed. With less fat metabolism, a greater reliance on carbohydrates may represent a shift to a less-efficient fuel."

The metabolic abnormality can eventually lead to impaired contraction of the heart and to heart failure.

Animal studies by collaborators at Washington University have shown that in mice with thickened heart muscle, genes linked to transporting and breaking down fatty acids are less active than normal - in other words, the heart's fat-burning machinery is malfunctioning.

In this human study, the scientists studied patients who had hypertension that resulted in hypertrophy of the muscle of the left ventricle, the chamber of the heart that pumps blood to the body. The study showed that the greater the muscle mass of the hypertrophic heart, the lower the ability to burn fat. Magnetic resonance scans suggested that hypertrophic heart muscle had subtle abnormalities in contractile function at rest and was less energy efficient.

Normally heart muscle will alter between using fats and carbohydrates as fuel depending on availability. But at times of the day when blood glucose is low - such as when a person hasn't eaten in a while - hypertrophic hearts can't switch to burning fatty acids as normal hearts would, possibly leaving them energy deficient, de las Fuentes explains.

"This is the first time these data have been shown in humans," says senior author Victor G. Dávila-Román, M.D., director of the Cardiovascular Imaging and Clinical Research Core Laboratory and professor of medicine, anesthesiology and radiology. "That is especially significant because high blood pressure (high blood pressure) is a huge public health problem in the United States. Of the 65 million people with hypertension, between 25 and 50 percent of them have some evidence that their heart has been affected by high blood pressure."

Not everyone who has hypertension will develop hypertrophy, and not everyone with hypertrophy has long-term problems, as per de las Fuentes. Some people appear to be protected while others appear to be at increased risk, likely due to genetic factors.

"Because we have this evidence that shows that fatty acid metabolism may play a role in this process, we are looking for variations in the metabolism genes in an ongoing clinical study," de las Fuentes says.

Dávila-Román adds that by looking at the genetics of high blood pressure and hypertensive heart disease, they hope to identify genes that predispose people to both good and bad traits linked to these disorders. Such information promises opportunities for both prevention and therapy of cardiac disease.



Posted by: Daniel    Source




Did you know?
"The heart is the single most energy-consuming organ per weight in the body," says Lisa de las Fuentes, M.D. Under some conditions this energy-hungry organ is prone to defects in its energy metabolism that contribute to heart disease, as per research published in a recent issue of the Journal of Nuclear Cardiology by de las Fuentes and his colleagues at Washington University School of Medicine in St. Louis.

Medicineworld.org: High Blood Pressure Induces Low Fat Metabolism

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