What are AGEs, and how do they relate to collagen in skin?

AGEs (advanced glycation end products) are compounds formed when sugars attach to proteins or lipids without the involvement of an enzyme. In skin, they accumulate in the collagen and elastin of the dermis, because those proteins turn over slowly and are exposed to sugars for years (Gkogkolou & Böhm 2012).

How do AGEs form?

The reaction is called glycation. It is the same chemistry as the browning of food when it is heated. Glycation is a slow chemical process that happens normally in the body. It is not a condition.

The steps of the reaction

A carbonyl group on a sugar reacts with an amino group on a protein, forming an unstable early product (a Schiff base). This rearranges into a more stable product (an Amadori product) and eventually becomes an AGE.

What decides how much builds up?

Two main things: how much sugar is available, and how long the protein stays in place before it is replaced.

How do AGEs relate to collagen in skin?

Why does collagen accumulate AGEs?

Type I and type IV collagen have a slow turnover of about 10 years (Gkogkolou & Böhm 2012). These proteins stay in the tissue long enough to accumulate AGEs. Fast-turnover proteins do not accumulate them in the same way.

What has research reported?

Reviews describe AGEs forming cross-links between adjacent collagen fibres, which changes the mechanical properties of the fibres. AGEs can also bind to a cell-surface receptor known as RAGE. These findings come from laboratory work and observational studies.

How are AGEs in skin measured?

Research uses skin autofluorescence, a way of estimating AGE accumulation in tissue without puncturing or cutting the skin.

Where do AGEs come from?

Formed by the body

The body forms AGEs as part of normal metabolism.

From food

Some foods already contain AGEs. The amount depends on how the food is prepared, including cooking time and temperature. Fried food generally contains far more AGEs than boiled or steamed food (Gkogkolou & Böhm 2012).

Smoking and sunlight

Research reports that smoking accelerates AGE formation and increases their deposition in several tissues, including skin, and that sun-exposed skin shows more AGE deposition.

How does cooking method affect AGEs in food?

This section is about the amount of AGEs that form in food during cooking. There is no conclusion yet on how changing cooking methods affects skin.

Moist heat and dry heat

In measurements of AGEs in food, poached or steamed chicken had less than a quarter of the AGEs of roasted or broiled chicken (Uribarri et al. 2010).

Acidic marinades before cooking

In the same study, beef marinated for 1 hour in lemon juice or vinegar before cooking formed less than half the amount of AGEs during cooking as unmarinated beef (Uribarri et al. 2010).