Lipid peroxidation

Lipid peroxidation is a biochemical process that involves the oxidative degradation of lipids. It is a crucial mechanism in cell biology as it can lead to cell damage and is implicated in a variety of diseases.

Overview

Lipid peroxidation is a process in which free radicals steal electrons from the lipids in cell membranes, resulting in cell damage. This process proceeds by a free radical chain reaction mechanism. It most often affects polyunsaturated fatty acids, because they contain multiple double bonds, in between which lie methylene bridges (-CH2-) that possess especially reactive hydrogens.

Mechanism

The process of lipid peroxidation begins with a hydrogen atom being taken away from a carbon atom in the lipid molecule by a reactive species, such as a free radical. This results in the formation of a fatty acid radical. If oxygen is present, it will interact with the fatty acid radical to form a peroxyl-fatty acid radical. The peroxyl-fatty acid radical can then react with a second fatty acid molecule to generate a different fatty acid radical and a lipid peroxide, or a cyclic peroxide if it had reacted with itself. This new fatty acid radical can then react with another molecule of oxygen creating a new peroxyl-fatty acid radical. This cycle continues, resulting in an amplification of the oxidative damage.

Biological implications

Lipid peroxidation can lead to the formation of malondialdehyde (MDA), which is a reactive aldehyde and is one of the many reactive electrophile species that cause toxic stress in cells and forms covalent protein adducts referred to as advanced lipoxidation end-products (ALE), in addition to its role as a signaling molecule. Other aldehydes such as 4-hydroxynonenal (4-HNE) are also produced. These aldehydes can form covalent adducts with many biological molecules, including proteins, lipids, and DNA.

Role in disease

Lipid peroxidation has been implicated in a number of diseases and health conditions, including atherosclerosis, Parkinson's disease, Alzheimer's disease, and cancer. It is also involved in aging and is thought to play a role in the development of complications in diabetes.

Measurement

Several methods are available for measuring lipid peroxidation, including the thiobarbituric acid reactive substances (TBARS) assay, which measures the concentration of malondialdehyde, a product of lipid peroxidation.

Prevention and treatment

Antioxidants, such as vitamin E and vitamin C, can help prevent lipid peroxidation by neutralizing free radicals. In addition, certain dietary interventions and lifestyle changes, such as a diet rich in fruits and vegetables and regular exercise, can also help reduce the risk of lipid peroxidation.

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Lipid peroxidation

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  Diagram of radical formation from linoleic acid

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  Illustration of free radical toxicity

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  Photograph of sunflower seeds