Circadian clock impacts heart's response to fatty acids

By Ruth SoRelle, M.P.H.

The heart's ability to make use of or metabolize fatty acids varies with the time of day, indicating that circadian clocks play a significant role in how individual heart cells called cardiomyocytes respond, said a Baylor College of Medicine researcher, whose study appears in a recent issue of the Journal of Biological Chemistry.

"If cardiomyocytes don't store fatty acids or adequately oxidize them, the fatty acids become toxic and can interfere with the ability of the heart to contract and pump blood," said Martin Young, D.Phil., assistant professor of pediatrics at BCM and the USDA/ARS Children's Nutrition Research Center at BCM and Texas Children's Hospital. Such findings could have implications in the understanding and ultimate treatment of the weakening of the heart that is associated with obesity, type 2 diabetes and shift work.

Fatty acids

Fatty acids are the basic building blocks of all fats in the body. They are found in dietary fats and are used for energy and development of tissues in the body.

"We did the study in two ways," said Young, "We took cardiomyocytes and put them into a culture medium and challenged them with fatty acids. Even in isolation, these cells changed in the way they responded to the fatty acids depending on the time of day."

In animal studies, they found that fasting animals increased the release of fatty acids from stored fat into the blood.

"When we do that, we see marked circadian rhythms," said Young. In fact, the way in which the heart produced enzymes needed to make use of the released fatty acids varied with the time of day.

Impaired 'clocks'

In animals bred to have impaired cellular "clocks" only in the heart, the response to the fatty acids was significantly diminished, he said.

Such studies are important because they produce critical information about how the heart cells deal with fatty acids, either using them completely for energy or storing them as triglycerides.

Researchers from BCM; Case Western Reserve University, Cleveland, Ohio; Albert Einstein College of Medicine, Bronx, New York; and Texas A & M University, College Station, Texas, took part in this study.

Funding for this work came from the American Heart Association Texas Affiliate and the National Heart, Lung and Blood Institute.

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