Elevated glucose levels have been identified as culprits and/or risk factors for the progression of microvascular and macrovascular complications in Type 1 diabetes. Our studies on the biochemical nature and clinical significance of advanced glycation endproducts (AGEs) determined near DCCT closeout demonstrated that skin collagen AGEs are robust long-term predictors of microvascular and subclinical cardiovascular complications 16 years after the end of DCCT. This predicting effect is, independent of HbA1c, age, diabetes duration, and other risk factors. However, the determination of specific AGEs in skin is not feasible at the bench level, except for intrinsic ski fluorescence. Therefore, how to translate these exciting findings to a more feasible alternative approach becomes a pressing task. Taking advantage of the PAR announcement, we propose to investigate a pragmatic and clinically relevant hypothesis that determination of serum and urine protein markers of carbonyl (AGEs), oxidative and nitrosative stress ("metabolic stress markers"), individually or a set, at baseline or longitudinally, will allow us to predict which individuals with Type 1 diabetes in the DCCT/EDIC trial are at long-term increased risk of developing micro- and macrovascular vascular complications (primary endpoints). To achieve this goal, a team consisting of biochemists and a clinical diabetologist investigator from the DCCT/EDIC Research Group at Case Western Reserve University and statisticians at theDCCT Data Coordinating at the Biostatistics Center of the George Washington University has been assembled. Data will be generated using a powerful liquid chromatography mass spectrometry method with isotope dilution that accurately determines 9 markers, i.e. 2 glycation products (fructose-lysine and glucose pane), 2 glycoxidation products (carboxymethyl-lyinse (CML) and carboxyethyl-lysine (CEL), 2 oxoaldehyde products (glyoxal and methylglyoxal hydroimidazolones), 2 products of metal catalyzed oxidation (allysine and 2-amino adipic acid) and one oxidation product (methionine sulfoxide). Pentosidine and the nitrosylation product 3-nitrotyrosine will be determined by fluorescence HPLC. Statistical models will be tested to determine how these serum and urine markers relate to skin AGEs, contribute to long-term risk of complications, and whether adjustment for known risk factors attenuates the predicting power of these markers. A successful outcome of this research may lead to the implementation of a "metabolic stress panel" as adjunct to HbA1c for the evaluation of metabolic risk factors for diabetic complications in the clinical setting.
Despite progress with understanding how diabetic complications develop, it is still very difficult to predict who is at risk. While high blood sugar levels themselves are risk factors, it is not clear why some individuals do and others don't develop complications. Vice-versa, some individuals with relatively mild elevations of blood sugar develop fulminant complications. This proposal seeks to identify the secondary blood and urine metabolic factors and chemicals responsible for damaging tissues in Type 1 diabetes and the progression of blindness, kidney insufficiency, nerve damage and cardiovascular complications, independently of high blood sugar.