Beta oxidation is the process of breaking down fatty acids into acetyl CoA, which will be further processed to produce energy in the form of ATP.
The process of the breakdown / degradation of fatty acids in eukaryotics occurs in the mitochondria, so the fatty acids in the cytoplasm must be brought to the mitochondria first in order to take place beta oxidation. The fatty acids found in the cytoplasm must be activated first as an acyl-CoA fat before entering the mitochondria. Fatty-CoA acyl cannot simply penetrate the mitochondrial membrane, the molecule must be carried by a carrier (carrier) called carnitine. Fatty acyl-CoA binds to carnitine to form carnitine fatty acyl and penetrates the mitochondrial membrane.
β-oxidation of fatty acids (fatty acid β-oxidation, FAO) is a multistep process in which fatty acids are broken down by various tissues to produce energy. Fatty acids enter the cell mainly through the transport or transporter of fatty acids on the cell surface.
Catabolism of fatty acids consists of:
- Activation and transport of fatty acids
- Oxidation of beta carbon to the carbonyl group.
- Splitting of two carbon segments produces acetyl-CoA.
- The oxidation of acetyl-CoA to CO2 in the tricarboxylate cycle.
- Electrons transfer from electron carriers to the electron transport chain in oxidative phosphorylation.
Clinical Aspects of Some Fatty Acid Beta-Oxidation Disorders
In this group, diseases are manifested by the metabolic inability to oxidize fatty acids due to absence or enzymatic dysfunction, and in other cases by secondary depletion of carnitine.
- Carnitine palmitoyl transferase type II (CPT II) deficiency
- CPT II affects males more than females and is more apparent in people with diabetes or nutritional deficiency. Fasting can trigger symptoms, the most important of which are myalgia, fatigue and reddish-brown urine.
- It usually becomes apparent in adults, but a more severe form affects children.
- Treatment includes a diet restricted in protein and fat and rich in carbohydrates, adequate hydration, avoiding fasting and keeping the child warm.
- Carnitine supplementation can be effective.
- Multiple acyl-CoA dehydrogenase deficiency
- Deficiency of multiple acyl-CoA dehydrogenase also known as Glutaric Acidemia Type II (GA II) manifests itself in three forms, the neonatal form being quite severe and often fatal within a few weeks.
- Symptoms of neonatal GA II in children with congenital abnormalities can include severe hypoglycemia, metabolic acidosis, hypotonia, hepatomegaly and often a “sweaty feet” odor.
- When congenital anomalies are absent, symptoms can be milder and untreated children can survive for a longer period.
- The treatment includes a diet rich in carbohydrates, restricted to proteins and fats, with frequent meals. Riboflavin and carnitine supplementation can be helpful.
- Long-chain 3-hydroxy-acyl-CoA dehydrogenase deficiency (LCHAD)
- Typical symptoms of LCHAD are hypoglycemia, lethargy, weight deficit and developmental delay, often accompanied by hypotonia and cardiomyopathy. Some episodes of Sudden Infant Death Syndrome (SIDS) are possibly caused by LCHAD.
- Early diagnosis and treatment can prevent life-threatening episodes. Fasting should be avoided and in addition, a diet rich in carbohydrates should be instituted.
- Medium chain acyl-CoA dehydrogenase deficiency (MCAD)
- MCAD is characterized by recurrent episodes of metabolic acidosis, and by hypoglycemia, lethargy and coma. Symptoms typically begin in the infant or young children.
- MCAD occurs mainly among white descendants from northern Europe.
- Initial episodes are often triggered by fasting and can lead to death in 20 to 25 percent of cases.
- Approximately 25% of deaths attributed to Sudden Infant Death Syndrome (SIDS) are probably the result of MCAD.
- Avoiding fasting is imperative. The administration of glucose IV is necessary when there is food intolerance. High intake of medium and long chain fatty acids should be avoided. Carnitine supplements are recommended for these children.
- Short-chain acyl-CoA dehydrogenase deficiency (SCAD)
- The initial symptoms of SCAD are weight deficit and hypoglycemia. In the long run, there is a delay in development.
- Like other fatty acid oxidation disorders, fasting can precipitate a crisis and should be avoided.
- The diet must be controlled and carnitine supplements must be administered.
