Nonenzymatic browning of proteins and the sorbitol pathway

As a result of the operation of the sorbitol pathway fructose levels increase in various tissues in diabetes. In vitro glycation of protein by fructose (fructation) leads to protein bound fluorescence generation at a rate ten times that resulting from glycation by glucose (glucation), possibly by a faster conversion of Amadori groups to fluorophores. Therefore, tissue protein fluorescence might, in part, result from fructation. Evidence is presented for the occurrence of in vivo fructation of skin collagen and soluble lens proteins in diabetic rats. Fructation-induced protein functional alterations might underlie complications of diabetes in tissues where the sorbitol pathway is active.