In and ex Vivo Mitochondrial Function of the Heart

"31P-MRS measurement of the heart: Phosphorous magnetic resonance spectroscopy (31P-MRS) will be used for the determination of the energy status of the heart in vivo. The localization of phosphorus energy metabolites in the heart will be performed by one-dimensional spectroscopic imaging, resulting in spectra from slices through the heart of 1 cm thickness. The peaks of PCr and ATP will be fitted in order to calculate the ATP/PCr ratio.~The measurement of cardiac function is a standardised protocol. In the 4 chamber view setting a T1 mapping sequence will be performed for the detection of fibrosis. Hereafter patients will receive contrast for T2 mapping and late enhancement studies for determining extracellular volume and ischemia."

Mitochondrial respiration rates are ex vivo measured in tissue homogenates under exposure of different substrates, stimulating different complexes of the electron transport chain of the mitochondria.

To determine blood glucose metabolism and renal function.

This device uses air displacement plethysmography for determining percent fat and fat-free mass in adults and children. The 5-minute test consists of measuring the subject's mass (weight) using a very accurate electronic scale, and volume, which is determined by sitting inside the BOD POD chamber. From these two measurements, the subject's body composition is calculated.

As basal energy metabolism might be related to cardiac metabolism and mitochondrial function, and basal metabolic rate shows inter-individual variance, it is an important subject characteristic of the patients. Resting substrate oxidation rates are measured with indirect calorimetry for 30 minutes. A ventilated hood is connected to indirect calorimetry equipment, which measures concentrations of oxygen consumption and CO2 production. From these parameters, the respiratory quotient (RQ), as well as energy expenditure and substrate metabolism will be computed. During this measurement, every 10 minutes (so 4 times) one tube of blood (10ml) will be drawn for the analysis of lipid and glucose metabolites.