Principles of disorders of energy production from long-chain fatty acids (fatty acid oxidation)
Metabolism and metabolic disorder
The term metabolism comprises all the processes which are necessary for the development of the body (e.g. for growth), for the preservation of bodily functions and for energy production. To fulfil these tasks, the nourishment consumed with food or the reserves built-up in the body are processed in many carefully coordinated stages (chemical reactions). These stages are enabled by enzymes and transporters (these are proteins produced in the body). Every stage in the metabolism needs its own enzyme. If a particular enzyme does not work properly in the body, the corresponding metabolic stage may also not be carried out properly, and this creates a metabolic disorder. Since there are many different metabolic stages, there are also many different metabolic disorders. The metabolism of fatty acids serves to supply energy for the body and its organs.
What are nutrients and why are they important?
A nutrient is something that makes us thrive and grow. The main components of nutrition (macronutrients) are protein, fat and carbohydrates. They mainly provide energy to the body and we need them in large quantities. However, vitamins, minerals and trace elements (micronutrients) are also essential nutrition to our body. Other essential food components are water and fibre.
Fats and fatty acids
The most important function of fat is the supply of energy. Fat has the highest energy density and supplies more than double the calories (energy) of carbohydrates. The body creates fat deposits for fasting periods. But fat is also used as thermal insulation. It is further required as a transporter for fat-soluble vitamins. Foods rich in fat are tastier because many flavourings are fat-soluble. The body can draw fat from two different sources; from food and from fat stored in the body. Fats consist of glycerine and various fatty acids which are separated from one another during digestion in the intestine. Fats are also called triglycerides due to their structure i.e. one glycerine molecule bonds to three fatty acids. The type of fatty acids they contain determine the property of a fat (e.g. liquid or solid) and its functions in the body e.g. immune.
How is fat metabolised and used in the body?
Fat is absorbed as food and used by the body for energy production. The body can also break down its own fat reserves to generate energy. Specific fat elements, so-called essential fatty acids, must be absorbed regularly as food, as they are essential for the development of all cells and for the control of the body’s vital processes. Fat absorbed as food normally consists of long-chain fatty acids. These fatty acids can be imaged as chains which are broken down with the aid of enzymes so that they can be available for energy production. Energy production from the breakdown of fatty acids is very important for muscles, and especially for the heart muscle. Enzymes are formed within the body and facilitate metabolic functions. Many different enzymes are involved in the breakdown of fatty acids. Each of these enzymes facilitates an exact breakdown stage and has a very specific function in it.
What happens with a disorder of energy production from long-chain fatty acids?
If energy production from long-chain fatty acids does not work, two problems arise:
- The body does not have the energy from the breakdown of fatty acids
- The fatty acids which have not been broken down accumulate in the body
- Problem 1: If the body can’t gain enough energy from stored carbohydrates, energy must be sourced from fat breakdown. Shortly after a meal, the body has enough carbohydrates in the liver and muscles. If these are depleted, the fat reserves must be used for energy production. However, in case of a fatty acid oxidation disorder, the fat reserves cannot be used sufficiently. For this reason, long periods of fasting or an increased energy demand from the body, could result in energy deficiency. This energy deficiency can lead to serious hypoglycaemias (dangerously low concentrations of blood sugar). In hypoglycaemia, the brain is particularly at risk. A reduction in muscle fibres is also a risk if there is a lack sufficient energy, which could lead to muscle pain and weakness but also to problems with the heart muscle longer term.
- Problem 2: Long-chain fatty acids are partially bonded with the carrier substance carnitine and excreted in the urine. But they can also accumulate and harm the body, particularly the heart. It can lead to cardiac arrhythmias or disorders of the heart’s pumping function. Furthermore, there is less carrier substance carnitine is then available to the body.
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