Mitochondrial fatty acid beta-oxidation and carnitine shuttle system (FAO/Carnitine Shuttle)

The mitochondrial fatty acid beta-oxidation (FAO) and carnitine shuttle system is a critical metabolic pathway responsible for the breakdown of long-chain fatty acids to generate acetyl-CoA, NADH, and FADH2 for ATP production [1, 5]. This process begins with the carnitine shuttle, where carnitine palmitoyltransferase 1 (CPT1) converts acyl-CoA to acylcarnitine for transport across the mitochondrial membrane [2]. Once inside, the beta-oxidation cycle sequentially removes two-carbon units from the fatty acid chain through four enzymatic steps: oxidation, hydration, oxidation, and thiolysis [1, 3]. This pathway is a major energy source for the heart and skeletal muscle but is often dysregulated in metabolic diseases, cardiovascular disorders, and cancer [3, 4]. Pharmacological modulation of this system, particularly through CPT1 inhibitors like etomoxir or thiolase inhibitors like trimetazidine, is used to treat angina and heart failure by shifting metabolism toward glucose oxidation, which is more oxygen-efficient [3]. However, systemic inhibition can lead to side effects such as hepatic steatosis or hypoglycemia due to the essential role of FAO in fasting energy homeostasis [1, 5].

Other names

Fatty acid oxidation pathwayMitochondrial beta-oxidationCarnitine cycleFAO pathwayFatty acid degradation

Inhibition of fatty acid transport into the mitochondria (via CPT1) or inhibition of enzymatic steps (via 3-KAT) to shift cellular energy production from fatty acids to glucose oxidation [3].