Effects of acute elevation of circulating fatty acids on cardiac lipid accumulation in healthy lean young men.

To test whether the myocardium is storing more lipids when free fatty acid concentration is elevated, subjects cycled for two hours in the fasted state, which is well known to lead to an increase in free fatty acid concentrations. When subjects stay fasted during recovery, free fatty acid concentration stay high. However, when glucose drinks are administered before and during the test day, the elevation of free fatty acids is completely blunted. In the two conditions (high vs low levels of free fatty acids), cardiac lipid content and cardiac function is determined.

Lipids are taken up by the heart when availability is high. High plasma concentrations of free fatty acids lead to increased lipid storage in the heart.

Cardiac lipid content is measured at the beginning of the test day, after cycling and after 3 hours of recovery. Cardiac function and energy status is only determined after recovery.

Subjects cycled for 2 hours at 50% of the predetermined maximal work load in the fasted state and stay fasted during a three hour recovery period. This procedure is known to increase free fatty acid concentration. Before and after exercise and after recovery, cardiac lipid content is determined by Magnetic Resonance Spectroscopy. Cardiac function and energy status is determined at the end of the test day, after recovery. During the test day, blood samples are taken at multiple time points and fat- and carbohydrate oxidation is determined by indirect calorimetry. The same procedure is repeated with glucose supplementation to blunt the increase in free fatty acids. The two treatments (with/without glucose) were randomized.