Dietary glycotoxins correlate with circulating advanced glycation end product levels in renal failure patients

Backqround: Levels of advanced glycation end products (AGEs), well-known proinflammatory compounds, are markedly elevated in patients with renal failure, raising the speculation that they have a role as cardiovascular risk factors in this population. Although elevated AGE levels in patients with renal failure have been attributed to impaired renal clearance and increased endogenous AGE formation, recent data suggest an important role for diet as a source of AGEs. Methods: To determine the relationship between dietary AGE content and serum AGE levels, a cross-sectional study was performed in our long-term dialysis patients. Dietary AGE intake was estimated by means of dietary records and questionnaires, and sera were obtained for measurement of 2 well-characterized AGEs, carboxymethyl-lysine (CML) and methylglyoxal (MG) derivatives. Results: The study population included 189 patients; 139 hemodialysis and 50 peritoneal dialysis patients. Serum CML level correlated significantly with dietary AGE intake, based on either 3-day food records (r = 0.5; P = 0.003) or dietary questionnaires (r = 0.22; P = 0.03). Although no correlation was observed with nutrient intake (protein, fat, saturated fat, or carbohydrate), both serum CML and MG levels correlated with blood urea nitrogen (r = 0.2; P = 0.03 and r = 0.2; P = 0.02, respectively) and serum albumin levels (r = 0.16; P = 0.04 and r = 0.18; P = 0.02, respectively). Conclusion: Data indicate that dietary AGE content, independently of other diet constituents, is an important contributor to excess serum AGE levels in patients with renal failure. Moreover, the lack of correlation between serum AGE levels and dietary protein, fat, and carbohydrate intake indicates that a reduction in dietary AGE content can be obtained safely without compromising the content of obligatory nutrients.