The relationships between long-term intensive control of glycemia and indicators of skin collagen glycation (furosine), glycoxidation (pentosidine and N(epsilon)-[carboxymethyl]-lysine [CML]), and crosslinking (acid and pepsin solubility) were examined in 216 patients with type 1 diabetes from the primary prevention and secondary intervention cohorts of the Diabetes Control and Complications Trial. By comparison with conventional treatment, 5 years of intensive treatment was associated with 30-32% lower furosine, 9% lower pentosidine, 9-13% lower CML, 24% higher acid-soluble collagen, and 50% higher pepsin-soluble collagen. All of these differences were statistically significant in the subjects of the primary prevention cohort (P < 0.006-0.001) and also of the secondary intervention cohort (P < 0.015-0.001) with the exception of CML and acid-soluble collagen. Age- and duration-adjusted collagen variables were significantly associated with the HbA1c value nearest the biopsy and with cumulative prior HbA1c values. Multiple logistic regression analyses with six nonredundant collagen parameters as independent variables and various expressions of retinopathy, nephropathy, and neuropathy outcomes as dependent variables showed that the complications were significantly associated with the full set of collagen variables. Surprisingly, the percentage of total variance (R2) in complications explained by the collagen variables ranged from 19 to 36% with the intensive treatment and from 14 to 51% with conventional treatment. These associations generally remained significant even after adjustment for HbA1c, and, most unexpectedly, in conventionally treated subjects, glycated collagen was the parameter most consistently associated with diabetic complications. Continued monitoring of these subjects may determine whether glycation products in the skin, and especially the early Amadori product (furosine), have the potential to be predictors of the future risk of developing complications, and perhaps be even better predictors than glycated hemoglobin (HbA1c).

Several mechanistic pathways linking hyperglycemia to diabetes complications, including glycation of proteins and formation of advanced glycation end products (AGEs), have been proposed. We investigated the hypothesis that skin collagen glycation and AGEs predict the risk of progression of microvascular disease. We measured glycation products in the skin collagen of 211 Diabetes Control and Complications Trial (DCCT) volunteers in 1992 who continued to be followed in the Epidemiology of Diabetes Interventions and Complications study for 10 years. We determined whether the earlier measurements of glycated collagen and AGE levels correlated with the risk of progression of retinopathy and nephropathy from the end of the DCCT to 10 years later. In multivariate analyses, the combination of furosine (glycated collagen) and carboxymethyllysine (CML) predicted the progression of retinopathy ( 2 ‫؍‬ 59.4, P < 0.0001) and nephropathy ( 2 ‫؍‬ 18.2, P ‫؍‬ 0.0001), even after adjustment for mean HbA 1c (A1C) ( 2 ‫؍‬ 32.7, P < 0.0001 for retinopathy) and ( 2 ‫؍‬ 12.8, P ‫؍‬ 0.0016 for nephropathy). The predictive effect of A1C vanished after adjustment for furosine and CML ( 2 ‫؍‬ 0.0002, P ‫؍‬ 0.987 for retinopathy and 2 ‫؍‬ 0.0002, P ‫؍‬ 0.964 for nephropathy). Furosine explained more of the variation in the 10-year progression of retinopathy and nephropathy than did CML. These results strengthen the role of glycation of proteins and AGE formation in the pathogenesis of retinopathy and nephropathy. Glycation and subsequent AGE formation may explain the risk of these complications associated with prior A1C and provide a rational basis for the phenomenon of "metabolic memory" in the pathogenesis of these diabetes complications. Diabetes 54:3103-3111, 2005 N onenzymatic glycation of proteins and subsequent formation of advanced glycation end products (AGEs) is one of the pathogenetic mechanisms thought to link hyperglycemia to diabetic retinopathy and nephropathy (1,2). Inhibitors of AGE formation (3-8) and breakers of AGE-protein crosslinks (9,10) reduce both microvascular complications in experimental diabetic models. The relationship of longterm intensive control of glycemia and its effect on these complications with indicators of skin collagen glycation (furosine), glycoxidation and AGE formation (pentosidine and carboxymethyllysine [CML]), and cross-linking (acid and pepsin solubility) were previously examined in 215 patients with type 1 diabetes from the Diabetes Control and Complications Trial (DCCT) (11) who underwent a skin biopsy ϳ1 year before the close of the trial. Compared with conventional treatment, intensive treatment was associated with significantly lower levels of furosine, pentosidine, CML, and relative fluorescence and with higher levels of acid-and pepsin-soluble collagen (11). Age-and duration-adjusted collagen variables were significantly associated with the A1C value closest in time to the biopsy and with mean DCCT A1C. Retinopathy, nephropathy, and neuropathy outcomes as dependent variables were sign...

OBJECTIVETo assess complication prevalence and identify protective factors in patients with diabetes duration of ≥50 years. Characterization of a complication-free subgroup in this cohort would suggest that some individuals are protected from diabetes complications and allow identification of endogenous protective factors.RESEARCH DESIGN AND METHODSCross-sectional, observational study of 351 U.S. residents who have survived with type 1 diabetes for ≥50 years (Medalists). Retinopathy, nephropathy, neuropathy, and cardiovascular disease were assessed in relation to HbA1c, lipids, and advanced glycation end products (AGEs). Retrospective chart review provided longitudinal ophthalmic data for a subgroup.RESULTSA high proportion of Medalists remain free from proliferative diabetic retinopathy (PDR) (42.6%), nephropathy (86.9%), neuropathy (39.4%), or cardiovascular disease (51.5%). Current and longitudinal (the past 15 years) glycemic control were unrelated to complications. Subjects with high plasma carboxyethyl-lysine and pentosidine were 7.2-fold more likely to have any complication. Of Medalists without PDR, 96% with no retinopathy progression over the first 17 years of follow-up did not experience retinopathy worsening thereafter.CONCLUSIONSThe Medalist population is likely enriched for protective factors against complications. These factors might prove useful to the general population with diabetes if they can be used to induce protection against long-term complications. Specific AGE combinations were strongly associated with complications, indicating a link between AGE formation or processing with development of diabetic vasculopathy.