Abstract 3673: Metabolism Of Advanced Glycation End Products (AGEs) By The Polyol Pathway Enzyme - Aldose Reductase Decreases AGE Accumulation In Diabetes
Diabetes is a major risk factor for cardiovascular disease. Diabetes induces endothelial dysfunction and nephropathy, and accelerates atherogenesis. Metabolic changes in diabetes include activation of the polyol pathway and protein kinase C and the accumulation of advanced glycation end products (AGEs). The relationships between these pathways are; however, unclear. Increased formation and accumulation of AGEs, in particular, has been linked to the stimulation of inflammatory pathways and the development of secondary diabetic complications. Herein, we report that aldose reductase (AR) metabolizes AGE precursors in the heart and in endothelial cells. Human umbilical vein endothelial cells (HUVEC) cultured in high (25 mM) glucose were found to accumulate intracellular AGEs resulting in increased glycation of the heat shock protein (HSP27). In vitro several aldo-keto reductases catalyzed the reduction of AGE precursors although highest catalytic efficiency was observed with AR. Methylglyoxal (MG)-treated HUVEC or hearts perfused with MG generated a reduced product which was identified as acetol by GC/MS analysis. Acetol formation and the generation of AGEs in HUVEC were prevented by treatment with AR inhibitors sorbinil (48±3%; P<0.05) and tolrestat (50±3%; P<0.05). Reduction of MG to acetol was diminished in hearts from AR-null mice (74±8%; P<0.05) and increased in mice overexpressing AR (360±40%; P<0.05) as compared to wild-type (WT) mice. Immunohistochemical analysis showed increased accumulation of AGEs in the hearts and kidney of streptozotocin-treated AR-null mice than similarly-treated WT mice. Western blot analysis showed that AGE formation was increased by 180±20% (P<0.05) in the heart and 270± 50% in the plasma (P<0.05) of diabetic AR-null mice as compared to diabetic WT mice. MALDI/MS analysis identified several MG-modified proteins in diabetic AR-null mouse heart which included myocilin, 3-hydroxisobutyrate phosphate, proline-serine-threonine phosphate interacting protein. Collectively, these results suggest that AR metabolizes AGE precursors and prevents AGE accumulation in diabetic tissues. These findings provide a new protective role of polyol pathway in preventing cardiovascular complications of diabetes.