Each cell is surrounded by other cells, and by connective fibers, and other materials referred to as the extracellular matrix or ECM. The matrix and surrounding cells form a living space, or niche for the cell. Over time, the connective fibers are seen to slowly and gradually break down and stick together. A major factor in this deterioration is the chemical process of glycation.
Sugar molecules in the blood and in the cells chemically bond to proteins and to DNA. (This bonding is called “glycation”, “the Maillard reaction”, “the browning reaction”, or “nonenzymatic glycosylation”). The process happens gradually, so that glycation accumulates over the years on the longest-lived proteins which do not get recycled very often.
The clearest evidence of this is found in the extracellular collagen and elastin. Over time, in the presence of reactive oxygen species (ROS), glycation promotes covalent crosslinking between adjacent protein strands. Crosslinking reduces the flexibility, elasticity, and functionality of the proteins. Furthermore, the chemical modifications of glycation and crosslinking can initiate harmful inflammatory and autoimmune responses.
Glycation and crosslinking contribute strongly to many progressive diseases of aging, including atherosclerosis, cardiovascular diseases, kidney disease, stiffness of joints and skin, cataracts, impaired wound healing, complications of diabetes, and Alzheimer’s Dementia.
Münch, Gerald; et al (27 February 1997). “Influence of advanced glycation end-products and AGE-inhibitors on nucleation-dependent polymerization of β-amyloid peptide”. Biochimica et Biophysica Acta 1360 (1): 17–29. doi:10.1016/S0925-4439(96)00062-2. PMID 9061036.
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