Glycation is the result of a sugar-reducing molecule, such as fructose or glucose, bonding to a protein or lipid molecule without the controlling action of an enzyme. It may occur either inside (endogenous) or outside (exogenous) the body. Enzyme-controlled addition of carbohydrates is termed glycosylation; this process is less haphazard than glycation. Much of early laboratory research work on fructose glycations used inaccurate assay techniques that drastically understated its importance in glycation formation (Ahmed & Furth 1992). Fructose is a simple sugar (monosaccharide) found in many foods and one of the three most important blood sugars along with glucose and galactose. ... Glucose (Glc), a monosaccharide, is one of the most important carbohydrates. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Figure 1: Structure of a Lipid. ... In general, a molecule is the smallest particle of a pure chemical substance that still retains its composition and chemical properties. ... Ribbon diagram of the catalytically perfect enzyme TIM. An enzyme is a protein that catalyzes, or speeds up, a chemical reaction. ... Glycosylation is the process or result of addition of saccharides to proteins and lipids. ...

Exogenous

Exogenous glycations are typically formed when sugars are cooked with proteins or fats at temperatures over 120°C (~248°F). These compounds are absorbed by the body during digestion with about 35% efficiency. Browning reactions (usually Maillard type reactions)are evidence of pre-formed glycations. Indeed, sugar is often added to products such as french fries and baked goods to enhance browning. Glycation may also contribute to the formation of acrylamide (Stadler et al 2002), a potential carcinogen, during cooking. For other meanings of the word chip see CHIPS (disambiguation) French fries, chips, or pommes frites are potatoes that have been cut and deep-fried (i. ... The chemical compound acrylamide (acrylic amide) has the chemical formula C3H5NO and structure Its systematic name is 2-propenamide. ... In pathology, a carcinogen is any substance or agent that promotes cancer. ...

Endogenous

Endogenous glycations occur mainly in the bloodstream to a small proportion of the absorbed simple sugars: glucose, fructose and galactose. The balance of the sugar molecules is used for metabolic processes. It appears that fructose and galactose have approximately ten times the glycation activity of glucose, the primary body fuel (McPherson et al 1988). Glycation is the first step in the evolution of these molecules through a complex series of very slow reactions in the body known as Amadori reactions, Schiff base reactions, and Maillard reactions; all lead to advanced glycation endproducts (AGEs). Some AGEs are benign, but others are more reactive than the sugars they are derived from, and are implicated in many age-related chronic diseases such as: type II diabetes mellitus (beta cell damage), cardiovascular diseases (the endothelium and collagen are damaged), Alzheimer's disease (amyloid proteins are side products of the reactions progressing to AGEs), cancer (acrylamide and other side products are released), peripheral neuropathy (the myelin is attacked), and other sensory losses such as deafness (due to demyelination) and blindness (mostly due to microvascular damage in the retina). This range of diseases is the result of the very basic level at which glycations interfere with molecular and cellular functioning throughout the body and the release of highly-oxidizing side products such as hydrogen peroxide. Glucose (Glc), a monosaccharide, is one of the most important carbohydrates. ... Fructose is a simple sugar (monosaccharide) found in many foods and one of the three most important blood sugars along with glucose and galactose. ... Galactose (also called brain sugar) is a type of sugar found in dairy products, in sugar beets and other gums and mucilages. ... The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Diabetes mellitus is a medical disorder characterized by varying or persistent hyperglycemia (elevated blood sugar levels), especially after eating. ... Cardiovascular disease refers to the class of diseases that involve the heart and/or blood vessels (arteries and veins). ... When normal cells are damaged beyond repair, they are eliminated by apoptosis. ... Peripheral neuropathy is the medical term for damage to nerves of the peripheral nervous system, which may be caused either by diseases of the nerve or from the side-effects of systemic illness. ... This article is about hearing impairment in the patholocial sense. ... Blindness can be defined physiologically as the condition of lacking visual perception. ... Hydrogen peroxide (H2O2) is a clear liquid, slightly more viscous than water, that has strong oxidizing properties and is therefore a powerful bleaching agent that has found use as a disinfectant, as an oxidizer, and in rocketry (particularly in high concentrations as high-test peroxide (HTP)) as a monopropellant, and...

Glycated substances are eliminated from the body slowly, since the renal clearance factor is only about 30%. This implies that the half-life of a glycation within the body is about double the average cell life. Red blood cells are the shortest-lived cells in the body (120 days), so, the half life is about 240 days. This fact is used in monitoring blood sugar control in diabetes by monitoring the glycated hemoglobin level. As a consequence, long-lived cells (such as nerves, brain cells) and long-lasting proteins (such as DNA, eye crystalline, and collagen) may accumulate substantial damage over time. Metabolically-active cells such as the glomeruli in the kidneys, retina cells in the eyes, and beta cells (insulin-producing) in the pancreas are also at high risk of damage. The epithelial cells of the blood vessels are damaged directly by glycations, which are implicated in atherosclerosis, for example. Atherosclerotic plaque tends to accumulate at areas of high blood flow (such as the entrance to the coronary arteries) due to the increased presentation of sugar molecules, glycations and glycation end-products at these points. Damage by glycation results in stiffening of the collagen in the blood vessel walls, leading to high blood pressure. Glycations also cause weakening of the collagen in the blood vessel walls, which may lead to micro- or macro-aneurisms; this may cause strokes if in the brain. This article is about the disease that features high blood sugar. ... Kidneys viewed from behind with spine removed The kidneys are bean-shaped excretory organs in vertebrates. ... Italic text Human eye cross-sectional view. ... Beta cells are a type of cell in the pancreas in areas called the islets of Langerhans. ...

References

• Ahmed N, Furth AJ. Failure of common glycation assays to detect glycation by fructose. Clin Chem 1992;38:1301-3 PMID 1623595.
• McPherson JD, Shilton BH, Walton DJ. Role of fructose in glycation and cross-linking of proteins. Biochemistry 1988;27:1901-7. PMID 3132203.
• Stadler RH, Blank I, Varga N, Robert F, Hau J, Guy PA, Robert MC, Riediker S. Acrylamide from Maillard reaction products. Nature 2002;419:449-50. PMID 12368845.

Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ...

See also

• Alagebrium