Specific detections of the early process of the glycation reaction by fructose and glucose in diabetic rat lens

Abstract

The glycation reaction by fructose, as well as that by glucose, in control and diabetic rat lens was analyzed by using antibodies which specifically recognize adducts of lysine with fructose and with glucose. Levels of fructose adducts in diabetic rat lens were 2.5 times that of the control, and correlated with sorbitol levels. This was mainly due to enhanced glycation of L Land Q Q-crystallins by fructose under diabetic conditions. These data suggest that glycation by fructose may also play a role in cataract formation under conditions of diabetes and aging.z 1998 Federation of European Biochemical Societies.

Induction of 8-Hydroxydeoxyguanosine Formation in DNA by Fructose and Glucose in the Presence of Copper

“…The serum fructose concentration in healthy humans has been estimated to be about 10 µM, and was reported to increase 1.5-20 times in patients with diabetes [16][17][18]. As shown Fig.…”

“…In diabetes, the polyol pathway is accelerated [16][17][18]. The first enzyme in the pathway, aldose reductase, reduces glucose to sorbitol, which is then converted to fructose by sorbitol dehydrogenase.…”

“…In general, elevated glucose levels in diabetic states are thought to be a major source of oxidative stress in the body, via its autoxidation and glycation. However, in some tissues such as the lens, kidney and peripheral nerve, a polyol metabolizing pathway, in which glucose is converted into sorbitol via aldose reductase and then sorbitol is converted into fructose by sorbitol dehydrogenase, is active [16][17][18]. The concentration of fructose in the lens becomes equivalent to the glucose concentration in severe cases of diabetes [16].…”

“…Kidney 8-OHdG levels in diabetic rats have been reported to be increased and reduced by insulin treatment [15], implying the involvement of hyperglycemia in the formation of 8-OHdG. Under diabetic conditions, blood glucose levels increase 2 times (10 mM) or more compared to the control level (approximately 5 mM), and an excess of glucose in the blood was partially converted into fructose by an activated polyol pathway, leading to increased levels of the latter sugar [16][17][18]. On the other hand, under diabetic situations, increases in cellular store sites of iron or copper, or increased release of them from the store sites have been reported in several studies [19][20][21].…”

Role of fructose concentration on cataractogenesis in senile diabetic and non-diabetic patients

“…However, fructose participates in glycation (fructation) and AGE formation about ten times faster than glucose. The greater reactivity of fructose is because a higher proportion exists in the acyclic form, and because the fructose-derived equivalent to the Amadori product (referred to as Heyns product) is more reactive than the glucose-derived Amadori product [2]. Furthermore, fructation forms twice as much 3-deoxyglucosones as glucation, and can even form 3-deoxyglucosones directly under physiological conditions [3].…”