Glycation damage causes stiffness of the collagen in blood vessel walls, which leads to elevated blood pressure, especially in diabetics. Glycations can damage the collagen in blood vessel walls, which can lead to micro- or macro-aneurysms and, if in the brain, strokes. They can also affect the function of other organs such as the kidneys, eyes, and nerves. Glycation is the chemical reaction between sugar and proteins, fats, or DNA. As this process occurs within cells, it has an impact on cell function and viability. High levels of glucose in the blood cause more frequent exposure of tissues to this effect, so advanced glycation end products (AGEs) accumulate over time. AGEs are responsible for many of the complications associated with diabetes mellitus. There are three main types of glycation damage: cross-linkage, oxidation, and chain breaking. Cross-linkage occurs when two strands of a protein fiber become connected by a bridge formed by the addition of a sugar molecule. This change in structure makes it harder for the protein to function properly. For example, glycated collagen becomes less flexible and less able to support stress loads. It may even rupture, allowing blood to leak into surrounding tissue. Oxidative damage involves the formation of free radicals - molecules that contain oxygen atoms attached to carbon atoms. These radicals can be destructive because they can enter cells and attack vital components of the cell, including DNA.