Tuesday, December 2, 2008
What Are AGEs?
AGEs are the end-products of glycation reactions, in which a sugar molecule bonds to either a protein or lipid molecule without an enzyme to control the reaction. A similar reaction, known as glycosylation, uses an enzyme to control the reaction, targeting specific receptor sites on cells. Glycation, on the other hand, “is a haphazard process that impairs the functioning of biomolecules”.
Where Do AGEs Come From?
Advanced Glycation End products can come from two sources: the food we eat and internal production in the body. Let’s look at each of them.
AGE Formation In Food
When proteins are cooked with sugars in the absense of water, AGEs are formed. Water, however, prevents these sugars from binding to the protein molecules. Now, I know what you’re thinking when you hear the word “protein”: flesh. I was too, until I got to reading. However, grains, vegetables, fruits, and such all have protein in them as well, with browning being an indication of AGEs:
According to these new findings, brown foods, such as brown cookies, brown bread crust, brown basted meats and brown beans, and even brown coffee beans may increase nerve damage, particularly in diabetics who are unusually susceptible to nerve damage.
These are the very reactions that give certain foods their flavors after cooking. Food-borne AGEs are absorbed with about 30% efficiency when ingested.
AGE Formation In The Body
Once you’ve eaten, the body can still glycate the simple sugars in your food. A small proportion of the sugar in your bloodstream is glycated, while the rest goes to running your metabolic machinery. Consider what happens in the bloodstream of a diabetic with chronically elevated blood sugar. There are many opportunities for this circulating sugar to be glycated, which helps explain why diabetics have such high incidences of the issues discussed in the next section.
Fructose and galactose undergo glycation at about 10 times the rate as does glucose. Considering the dramatic increase in sugar consumption over the past several decades, and the subsequent increase in fructose consumption (recall that most sweeteners are approximately 50% fructose), is there any question why we’re seeing rising rates of heart disease, arthritis, and other inflammatory “diseases of aging”?
What Do AGEs Do In The Body?
The body is able to handle AGEs, though very slowly. The half-life of AGEs is about double that of the average cell life, meaning that damage can persist for quite some time, especially in long-lived cells like nerve and brain cells, eye and collagen proteins, and DNA. Not good!
Here’s a run-down of a few effects of AGEs:
…and are implicated in many age-related chronic diseases such as: type II diabetes mellitus (beta cell damage), cardiovascular diseases (the endothelium, fibrinogen, 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).
….
The endothelial 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.
