Diabetes, Non-Enzymatic Glycation, and Aging

Abstract

First described in the context of diabetes, advanced glycation end products (AGEs) are formed through a type of non-enzymatic reaction called glycation. Protein glycation and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic complications like retinopathy, nephropathy, neuropathy, cardiomyopathy along with some other diseases such as rheumatoid arthritis, osteoporosis, and, recently, skin aging. Glycation of proteins interferes with their normal functions by disrupting molecular conformation, altering enzymatic activity, and interfering with receptor functioning. AGEs form intra- and extracellular cross linking not only with proteins, but with some other endogenous key molecules including lipids and nucleic acids to contribute in the development of diabetic complications. Recent studies suggest that AGEs interact with plasma membrane localized receptors for AGEs (RAGE) to alter intracellular signaling, gene expression, release of pro-inflammatory molecules and free radicals. Characteristic findings of aging skin, including decreased resistance to mechanical stress, impaired wound healing, and distorted dermal vasculature, can be in part attributable to glycation. Multiple factors mediate cutaneous senescence, and these factors are generally characterized as endogenous (e.g., telomere shortening) or exogenous (e.g., ultraviolet radiation exposure). Interestingly, AGEs exert their pathophysiological effects from both endogenous and exogenous routes. The former entails the consumption of sugar in the diet, which then covalently binds an electron from a donor molecule to form an AGE. The latter process mostly refers to the formation of AGEs through cooking. Results of several studies in animal models and humans show that the restriction of dietary AGEs has positive effects on wound healing, insulin resistance and cardiovascular diseases. Recently, the effect of restriction in AGEs intake has been reported to increase the lifespan in animal models. Recent studies have revealed that certain methods of food preparation (i.e. grilling, frying, and roasting) produce much higher levels of AGEs than water-based cooking methods such as boiling and steaming. Moreover, several dietary compounds have emerged as promising candidates for the inhibition of glycation-mediated aging. In this chapter, we summarize the evidence supporting the critical role of glycation in skin aging and highlight preliminary studies on dietary strategies that may be able to combat this process.