Other meanings of Lipid peroxidation
Biochemistry
Lipid peroxidation is the oxidative degradation of lipids by free radicals and reactive oxygen species. It is especially consequential in polyunsaturated fatty acids, whose carbon–carbon double bonds make them vulnerable to chain reactions that alter membranes, generate reactive aldehydes, and damage proteins and nucleic acids.
Lipid peroxidation begins when a reactive species removes a hydrogen atom from a susceptible lipid, producing a lipid radical. Molecular oxygen rapidly combines with that radical to form a lipid peroxyl radical, which can abstract hydrogen from a neighboring lipid and continue the chain reaction.1 The process is favored in polyunsaturated fatty acids because their bis-allylic hydrogen atoms are relatively easy to remove. Iron and other transition metals can promote radical formation, while antioxidants such as vitamin E can interrupt propagation by donating hydrogen atoms to peroxyl radicals. Termination occurs when radicals combine or are neutralized, although the resulting lipid hydroperoxides may still decompose into highly reactive secondary products.
Lipid peroxidation changes membrane structure and produces electrophilic molecules that can modify cellular proteins. Primary products include lipid hydroperoxides; their breakdown yields aldehydes such as 4-hydroxynonenal and malondialdehyde, which can form covalent adducts with cysteine, histidine, and lysine residues.1 At moderate levels, these products can act as signaling mediators and influence inflammation, stress responses, and gene expression. At higher levels, membrane permeability, organelle function, ion gradients, and mitochondrial activity may be disrupted. Oxidized phospholipids also participate in immune recognition and vascular biology, but their effects depend strongly on molecular structure, concentration, cellular location, and the capacity of repair and detoxification systems.
Lipid peroxidation is difficult to quantify with a single universal test because its products are chemically diverse and unstable. Researchers measure conjugated dienes, lipid hydroperoxides, malondialdehyde, 4-hydroxynonenal adducts, or specific oxidized phospholipids; mass spectrometry generally provides greater molecular specificity than colorimetric assays.1 Cellular protection combines prevention, interception, and repair. Glutathione peroxidase 4 reduces phospholipid hydroperoxides, while vitamin E and related antioxidants limit radical propagation. Enzymes that maintain glutathione and NADPH support this defense. Interpretation requires care: sample handling, oxygen exposure, storage, and extraction can create oxidation after collection, and a measured aldehyde may reflect only one branch of a much larger reaction network.
Lipid peroxidation is also a defining biochemical feature of ferroptosis, an iron-dependent regulated cell-death pathway distinct from apoptosis and necrosis.2 In this setting, the decisive damage involves oxidation of particular membrane phospholipids rather than simply a high bulk concentration of oxidized fat. Cellular susceptibility depends on the availability of polyunsaturated phospholipids, iron handling, antioxidant capacity, and enzymes that remodel membrane composition.3 Oxidized lipids can travel between cells in lipoproteins or extracellular vesicles, extending effects beyond the site where radicals formed. The process is relevant to food rancidity as well as biology, and it has been investigated in atherosclerosis, neurodegeneration, ischemia–reperfusion injury, inflammation, and cancer. These links are biologically plausible but do not make lipid peroxidation a single diagnostic marker for any one disease.
The extent and biological meaning of lipid peroxidation depend on the lipid species, oxidant source, reaction location, and analytical method; no single assay captures the entire process.
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