Fig. 1.

Glucose and Fatty Acids are the Major Carbon Sources in Endothelial Cells. (A) Under normal, aerobic conditions, pyruvate is converted into Acetyl-CoA, which can enter the TCA cycle, generating byproducts that can participate in oxidative phosphorylation, generating a net of 32 ATP molecules. (B) Fatty acid metabolism uses the carnitine palmitoyl transferase (CTP) system. The CPT system allows FA to be transported into the mitochondrial matrix and undergo FAO. First, a FA is conjugated to a molecule of CoA by the enzyme fatty acyl-CoA synthetase. Subsequently, the CoA is replaced with a molecule of carnitine and brought into the intermembrane space via the enzyme CPT1A. The fatty-acyl-carnitine is then transported to the mitochondrial matrix via carnitine acylcarnitine translocase. Once the fatty-acyl-carnitine is in the mitochondrial matrix, CPT2 converts the fatty-acyl-carnitine back into fatty acyl-CoA, where it can then undergo fatty acid oxidation. Both carnitine and acetyl-carnitine can be transported back into the cytosol by carnitine acylcarnitine translocase. CrAT is a mitochondrial matrix enzyme that catalyzes acetyl-CoA conversion to acetyl-carnitine.

Abbreviations: ATP: adenosine triphosphate, NADH: nicotinamide adenine dinucleotide, FADH₂: flavin adenine dinucleotide, TCA: Tricarboxylic Acid Cycle, CPT: carnitine palmitoyl transferase, FA: Fatty Acids, FAO: fatty acid oxidation, CoA: coenzyme A, CrAT: Carnitine acetyltransferase.