Glycation


Glycation is the covalent attachment of a sugar to a protein or lipid. Typical sugars that participate in glycation are glucose, fructose, or their derivatives. Glycation is a biomarker for diabetes and is implicated in some diseases and in aging. Glycation end products are believed to play a causative role in the vascular complications of diabetes mellitus.
In contrast with glycation, glycosylation is the enzyme-mediated ATP-dependent attachment of sugars to protein or lipid. 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 the absorbed simple sugars: glucose, fructose, and galactose. It appears that fructose has approximately ten times the glycation activity of glucose, the primary body fuel. Glycation can occur through Amadori reactions, Schiff base reactions, and Maillard reactions; which lead to advanced glycation end products.

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 product are implicated in many age-related chronic diseases. Glycation cardiovascular diseases, Alzheimer's disease,
Long-lived cells, long-lasting proteins, and DNA can sustain substantial glycation over time. Damage by glycation results in stiffening of the collagen in the blood vessel walls, leading to high blood pressure, especially in diabetes. Glycations also cause weakening of the collagen in the blood vessel walls, which may lead to micro- or macro-aneurysm; this may cause strokes if in the brain.

Additional reading