Glycation
Template:Short description Template:Dist
Glycation (non-enzymatic glycosylation) is the covalent attachment of a sugar to a protein, lipid or nucleic acid molecule.<ref name=":0">Template:Citation</ref> Typical sugars that participate in glycation are glucose, fructose, galactose, and their derivatives. Glycation is the non-enzymatic process responsible for many (e.g. micro and macrovascular) complications in diabetes mellitus<ref>Template:Cite journal</ref> and is implicated in other diseases and in aging.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
In contrast with glycation, glycosylation is the enzyme-mediated ATP-dependent attachment of sugars to a protein or lipid.<ref name=":0" /> Glycosylation occurs at defined sites on the target molecule. It is a common form of post-translational modification of proteins and is required for the functioning of the mature protein.
Biochemistry
Glycations occur mainly in the bloodstream to a small proportion of absorbed simple sugars. Fructose has approximately ten times the glycation activity of glucose, the primary body fuel.<ref>Template:Cite journal</ref> Glycation can occur through Amadori reactions, Schiff base reactions, and Maillard reactions; which lead to advanced glycation end products (AGEs).<ref name=":0" />
Biomedical implications
Red blood cells have a consistent lifespan of 120 days and are accessible for measurement of glycated hemoglobin. Measurement of HbA1c—the predominant form of glycated hemoglobin—enables medium-term blood sugar control to be monitored in diabetes.
Some glycation products are implicated in age-related chronic diseases, including cardiovascular diseases (endothelium, fibrinogen, and collagen) and Alzheimer's disease (amyloid proteins are side-products of the reactions progressing to AGEs).<ref>Template:Cite journal</ref><ref>Template:Cite book</ref>
Long-lived cells (such as nerves and brain cells), long-lasting proteins (such as crystallins of the lens and cornea), and DNA can sustain substantial glycation over time. Damage by glycation results in stiffening of the collagen in blood vessel walls, increasing blood pressure, especially in diabetes.<ref>Template:Cite journal</ref> Glycations also cause weakening of the collagen in blood vessel walls,<ref>Template:Cite journal</ref> which may lead to micro- or macro-aneurysm; or strokes if in the brain.
A 2025 study reported that a combination of nicotinamide (a form of vitamin B3), ⍺-lipoic acid (ALA), thiamine (vitamin B1), pyridoxamine (a form of vitamin B6), and piperine reduced glycation damage in cell and mice models accompanied by non-muscle weight loss, apparently due to reduced Ghrelin and AMPK production.<ref>Template:Cite journal</ref>
DNA glycation
The term DNA glycation applies to DNA damage induced by reactive carbonyls (principally methylglyoxal and glyoxal) that are present in cells as by-products of sugar metabolism.<ref name = Richarme2017>Richarme G, Liu C, Mihoub M, Abdallah J, Leger T, Joly N, Liebart JC, Jurkunas UV, Nadal M, Bouloc P, Dairou J, Lamouri A. Guanine glycation repair by DJ-1/Park7 and its bacterial homologs. Science. 2017 Jul 14;357(6347):208-211. doi: 10.1126/science.aag1095. Epub 2017 Jun 8. PMID 28596309</ref> DNA glycation can cause mutation, breaks in DNA and cytotoxicity.<ref name = Richarme2017/> Guanine is the base most susceptible to glycation. Glycated DNA, as a form of damage, appears to be as frequent as oxidative DNA damage. Protein DJ-1 (also known as PARK7), is employed in the repair of glycated DNA bases in humans. DJ-1 Homologs have been identified in bacteria.<ref name = Richarme2017/>
See also
- Advanced glycation end-product
- Alagebrium
- Fructose
- Galactose
- Glucose
- Glycosylation
- Glycated hemoglobin
- List of aging processes