Abstract 158: Aldo-Keto Reductase Catalyzed Reductive Metabolism Of The Precursors Of Advanced Glycosylation End Products (ages) Prevents Age Formation
Formation of advanced glycosylation end products (AGEs) has been suggested to be one of the major biochemical pathways underlying the development of the cardiovascular complications of diabetes. Although AGEs are known to be derived from AGE precursors such as methylglyoxal and deoxyglucosone, the processes that regulate their metabolism and detoxification remain incompletely understood. In this study we examined the role of enzymatic reduction in the metabolism and toxicity of AGE precursors. Measurement of the steady-state kinetic parameters with several recombinant aldoketo reductase proteins showed that the catalytic efficiency for the reduction of methylglyoxal (MG) was highest with aldose reductase (AR; kcat /Km=1.698min-1μM−1) followed by aldehyde reductase (kcat/Km=0.55min-1μM−1), fibroblast growth factor induced-protein 1 (kcat/Km=0.098 min-1μM−1), 17β hydoxy steroid dehydrogenase (kcat/Km=0.08 min-1 μM−1 ), small intestinal AR (kcat/Km=0.012 min-1μM−1) and mouse vas deferens protein (kcat/Km=0.006 min-1μM−1). AR also catalyzed the reduction of deoxyglucosone (Km=112 ± 1 μM; kcat 38.91 min−1). Perfusion of the hearts isolated from C57BL/6 mice with methylgyoxal (2.5 μM) for 30 minutes reduced 3 ± 1 % MG to acetol as determined by GC/MS using 13C-methylglyoxal and 13C-acetol as standards. Perfusion of hearts isolated from cardiospecifc AR transgenic mice with MG increased the acetol formation by 48 ± 5 % (P<0.05). Incubation of human umbilical venous endothelial cells (HUVECs) in culture with MG for 24 h in the presence of AR inhibitors - sorbinil (50 μM) and tolerstat (25 μM) prevented the acetol formation by 90–95%. Incubation of HUVECs in high glucose (25 mM) in 0.4 % serum for 7-days resulted in AGE formation which was increased (2-fold) by sorbinil or tolrestat treatment. These data suggest that in cardiac myocytes and endothelial cells reduction via AR is a significant fate of AGE precursors and that AR-catalyzed reduction prevents AGE formation by metabolizing AGE precursors. Metabolic pathways of AGE precursors could be new therapeutic targets for preventing diabetic complications.