Carboxymethyl)lysine Levels Research Articles

Vitamin D reduces deposition of advanced glycation end-products in the aortic wall and systemic oxidative stress in diabetic rats

AimsVitamin D may have an important role in reducing the risk of cardiovascular disease. Advanced glycation end-products (AGEs) such as Nε-(carboxymethyl)lysine (CML), have been implicated in diabetic vascular complications via oxidative stress-mediated pathways. We investigated the potential protective effect of vitamin D on CML accumulation in the diabetic aortic wall. To test the effects of vitamin D on systemic oxidative stress we also assessed liver oxidative stress index (OSI) and serum total antioxidant capacity (TAC). MethodsMale Wistar rats were assigned to three groups: control, untreated diabetes, and diabetes+cholecalciferol. Diabetes was induced by streptozotocin, followed by oral administration of cholecalciferol (500IU/kg) for 10 weeks in the treatment group. Aortic CML accumulation was determined by ELISA and immunohistochemical assays. OSI was assessed by measuring TAC and the level of total peroxides in the liver and serum using colorimetric assays. ResultsUntreated diabetes was associated with significantly elevated CML levels in the aortic wall (19.5±3.3 vs 10.2±4.7ng/mL), increased liver OSI (6.8±1.9 vs 3.1±0.7), and reduced serum TAC (0.4±0.1 vs 0.8±0.3mmol Trolox/L), in comparison with the control group. Cholecalciferol significantly blocked the accumulation of CML in the aortic wall (10.4±8.4 vs 19.5±3.3ng/mL), decreased liver OSI (4.2±1.4 vs 6.8±1.9), and improved serum TAC (1.0±0.2 vs 0.4±0.1mmol Trolox/L), compared with the untreated diabetic group. ConclusionsStreptozotocin-diabetes resulted in increased deposition of AGEs and increased oxidative stress in the serum and liver. Vitamin D supplementation may provide significant protection against oxidative stress-mediated vascular complications in diabetes.

Advanced glycation end products in infant formulas do not contribute to insulin resistance associated with their consumption.

IntroductionInfant formula-feeding is associated with reduced insulin sensitivity. In rodents and healthy humans, advanced glycation end product (AGE)-rich diets exert diabetogenic effects. In comparison with human breast-milk, infant formulas contain high amounts of AGEs. We assessed the role of AGEs in infant-formula-consumption-associated insulin resistance.MethodsTotal plasma levels of Nε-(carboxymethyl)lysine (CML), AGEs-associated fluorescence (λex = 370 nm/λem = 445 nm), soluble adhesion molecules, markers of micro- binflammation (hsCRP), oxidative stress (malondialdehyde, 8-isoprostanes) and leptinemia were determined, and correlated with insulin sensitivity in a cross-sectional study in 166 healthy term infants aged 3-to-14 months, subdivided according to feeding regimen (breast-milk- vs. infant formula-fed) and age (3-to-6-month-olds, 7-to-10-month-olds, and 11-to-14-month-old infants). Effects of the consumption of low- vs. high-CML-containing formulas were assessed. 36 infants aged 5.8±0.3 months were followed-up 7.5±0.3 months later.ResultsCross-sectional study: 3-to-6-month-olds and 7-to-10-month-old formula-fed infants presented higher total plasma CML levels and AGEs-associated fluorescence (p<0.01, both), while only the 3-to-6-month-olds displayed lower insulin sensitivity (p<0.01) than their breast-milk-fed counterparts. 3-to-6-month-olds fed low-CML-containing formulas presented lower total plasma CML levels (p<0.01), but similar insulin sensitivity compared to those on high-CML-containing formulas. Markers of oxidative stress and inflammation, levels of leptin and adhesion molecules did not differ significantly between the groups. Follow-up study: at initial investigation, the breast-milk-consuming infants displayed lower total plasma CML levels (p<0.01) and AGEs-associated fluorescence (p<0.05), but higher insulin sensitivity (p<0.05) than the formulas-consuming infants. At follow-up, the groups did not differ significantly in either determined parameter.ConclusionsIn healthy term infants, high dietary load with CML does not play a pathophysiological role in the induction of infant formula-associated insulin resistance. Whether a high load of AGEs in early childhood affects postnatal programming remains to be elucidated.

Metabolic transit of Nε-carboxymethyl-lysine after consumption of AGEs from bread crust

Our aim was to investigate carboxymethyl-lysine (CML) intake and excretion after feeding rats with diets containing advanced glycation end-products (AGEs) from bread crust (BC) or its soluble or insoluble fractions, and to identify the factors responsible for the effects observed. CML in serum and different tissues was measured to detect possible accumulations. For 88 days, weanling rats were fed with either a control diet or one containing BC, or its soluble low molecular weight (LMW), soluble high molecular weight (HMW) or insoluble fractions. In the last week of the assay, faeces and urine were collected daily and stored as a 1 week pool. After sacrifice, blood was drawn to obtain serum and some organs were removed. CML analysis was performed by HPLC/MS/MS in diets, faeces, urines, serum and tissues. Faecal excretion of CML was strongly influenced by dietary CML levels and represents the major route of excretion (i.e. 33.2%). However, the urinary elimination of CML was probably limited or saturated, especially when more complex compounds were present in the diet. BC consumption increased CML in the cardiac tissue (170 ± 18 vs. 97 ± 3 μmol per mol lysine for BC and control groups), which correlated with the CML intake. The levels of this AGE in bone were unaffected by the dietary treatment, but in tail tendons CML was greatly increased in the animals that consumed the BC diet (102 ± 13 vs. 51 ± 8 μmol per mol lysine for BC and control groups, P = 0.006), which was associated with the intake of soluble LMW compounds present in BC. Despite the CML accumulation detected in different tissues, serum levels of protein-bound CML were unchanged, indicating the importance of measuring the free CML in this fluid as a real index of dietary CML.

The Accumulation of the Glycoxidation Product N&lt;sup&gt;&lt;i&gt;ε&lt;/i&gt;&lt;/sup&gt;-carboxymethyllysine in Cardiac Tissues with Age, Diabetes Mellitus and Coronary Heart Disease

Heart disease is one of the most important causes of death in developed countries. N(ε)-carboxymethyllysine (CML) is a major advanced glycation end product formed by combined reactions of non-enzymatic glycation and oxidation (glycoxidation), and it represents a general marker of oxidative stress. CML has been suggested to be involved in the pathogenesis of heart disease. Plasma CML is elevated in aging, atherosclerosis and/or diabetes. In this study, we measured cardiac CML levels to elucidate its role in the pathogenesis of heart disease. Cardiac tissues were collected from 105 patients (55.6 ± 17.0 years old: age range, 1-78 years) undergoing cardiac surgery. The diseases comprised coronary heart disease (CHD), CHD associated with diabetes mellitus (DM), valvular heart disease and congenital heart disease. The concentration of CML in cardiac tissues of each group was 4.31 ± 0.66, 5.29 ± 0.59, 2.74 ± 1.05 and 1.75 ± 1.16 μg/g, respectively. ELISA was used for measuring cardiac and plasma CML concentrations. Multiple linear regression analysis showed a significant positive correlation of CML concentrations with age (r = 0.803, p < 0.001), DM (r = 0.567, p < 0.001) and CHD (r = 0.523 p < 0.001). R(2) was 0.872 (p < 0.001); the three independent variables could explain 87.2% variation of CML concentrations. Cardiac CML concentrations exhibited a significant positive correlation with plasma CML (r = 0.983, p < 0.001). Our data indicate that cardiac CML concentrations increase with age, DM and/or CHD, and exhibit a positive correlation with plasma CML concentrations.

Diastolic Dysfunction of Aging Is Independent of Myocardial Structure but Associated with Plasma Advanced Glycation End-Product Levels

BackgroundHeart failure is associated with abnormalities of myocardial structure, and plasma levels of the advanced glycation end-product (AGE) Nε-(carboxymethyl)lysine (CML) correlate with the severity and prognosis of heart failure. Aging is associated with diastolic dysfunction and increased risk of heart failure, and we investigated the hypothesis that diastolic dysfunction of aging humans is associated with altered myocardial structure and plasma AGE levels.MethodsWe performed histological analysis of non-ischemic left ventricular myocardial biopsies and measured plasma levels of the AGEs CML and low molecular weight fluorophores (LMWFs) in 26 men undergoing coronary artery bypass graft surgery who had transthoracic echocardiography before surgery. None had previous cardiac surgery, myocardial infarction, atrial fibrillation, or heart failure.ResultsThe patients were aged 43–78 years and increasing age was associated with echocardiographic indices of diastolic dysfunction, with higher mitral Doppler flow velocity A wave (r = 0.50, P = 0.02), lower mitral E/A wave ratio (r = 0.64, P = 0.001), longer mitral valve deceleration time (r = 0.42, P = 0.03) and lower early diastolic peak velocity of the mitral septal annulus, e’ (r = 0.55, P = 0.008). However, neither mitral E/A ratio nor mitral septal e’ was correlated with myocardial total, interstitial or perivascular fibrosis (picrosirius red), immunostaining for collagens I and III, CML, and receptor for AGEs (RAGE), cardiomyocyte width, capillary length density, diffusion radius or arteriolar dimensions. Plasma AGE levels were not associated with age. However, plasma CML levels were associated with E/A ratio (r = 0.44, P = 0.04) and e’ (r = 0.51, P = 0.02) and LMWF levels were associated with E/A ratio (r = 0.49, P = 0.02). Moreover, the mitral E/A ratio remained correlated with plasma LMWF levels in all patients (P = 0.04) and the mitral septal e’ remained correlated with plasma CML levels in non-diabetic patients (P = 0.007) when age was a covariate.ConclusionsDiastolic dysfunction of aging was independent of myocardial structure but was associated with plasma AGE levels.

Digestibility of extruded proteins and metabolic transit of N ε -carboxymethyllysine in rats

Milk proteins are frequently used as supplements in fortified foods. However, processing produces chemical changes which likely affect the nutritional advantage. This study was intended to explore the possible difference in digestibility between extruded and non-extruded caseins and how the dietary N (ε) -carboxymethyllysine (CML) is metabolised. Normal rats were randomized into either an extruded protein diet (EP) or the same with unextruded proteins (UEP), for two periods of 2 weeks at 7 to 9 and 11 to 13 weeks of age. However, no difference in protein digestibility was detected between the two diets, either in young or in adult animals, despite a 9.4-fold higher level of CML and an 8.5-fold higher level of lysinoalanine in the EP than in the UEP. No diet-related changes were observed in plasma CML, either protein bound or free. Amounts of 38 and 48 % of the orally absorbed CML were excreted in urine and faeces, respectively, in UEP-fed rats. Lower rates of excretion were found in the EP-fed rats (23 and 37 %, respectively). A second animal study using a single oral dose of free CML (400 μg/rat) was set up to measure the systemic concentration of CML every hour from 0 to 4 h. It revealed that protein-bound CML was not affected by the oral dose of CML, and the highest free CML level found in the circulation was 600 ng/mL. Extruded proteins, therefore, appear to be well digested, and CML rapidly eliminated. Since its elimination is, however, incomplete, the question of its biodistribution and metabolism remains open.

Role of endogenous secretory RAGE (esRAGE) in defending against plaque formation induced by oxidative stress in type 2 diabetic patients

ObjectivesThis study was conducted to examine the relationship between endogenous secretory receptors for advanced glycation end products (esRAGE) and oxidative stress in type 2 diabetic patients (T2DM) with/without advanced macro-angiopathy. MethodsSixty-one T2DM were assessed for glycemic control, lipid profile, AGEs, carboxymethyl-lysine (CML), soluble receptor for advanced glycation end products (sRAGE), esRAGE and vitamin E levels, and underwent echo-color-Doppler of the abdominal aorta and aorto-iliac tree, carotid and lower limb arteries to check for evidence of plaques. ResultsAGEs and CML levels were significantly higher in T2DM with plaques than in those without (P = 0.0156 and P = 0.007, respectively) despite a comparable metabolic control and history of disease. EsRAGE and vitamin E levels were lower in T2DM with than in those without plaques (P < 0.0001), while no differences were observed as regards sRAGE levels. Considering all T2DM, univariate regression analysis showed a positive correlation between esRAGE and vitamin E (r = 0.456, P < 0.001), and a negative correlation between esRAGE and AGEs (r = −0.284, P < 0.05). After dividing patients by the presence/absence of plaques, esRAGE only correlated directly with vitamin E (r = 0.563, P < 0.01) and CML (r = 0.479, P < 0.05) in patients without plaques. ConclusionsThis is the first study to establish a relationship between esRAGE and oxidative stress and/or antioxidant power, suggesting that esRAGE upregulation might be part of the cell's antioxidative defenses against plaque forming as a result of oxidative stress in the T2DM phenotype (cases with a more efficient esRAGE production being better protected).

The role of advanced glycation end-products and their receptor on outcome in heart failure patients with preserved and reduced ejection fraction

Advanced glycation end products (AGEs) are increased in patients with heart failure (HF). We studied the predictive value of plasma AGEs N(ε)-(carboxymethyl)lysine (CML), pentosidine, and the soluble form of its receptor (sRAGE) in a large HF population. In 580 patients hospitalized with HF, plasma AGEs were measured before discharge when patients were clinically stable. Patients were followed for a period of 18 months. Primary end point was a composite of death and HF admissions. CML was determined by liquid chromatography mass spectrometry, pentosidine by high-performance liquid chromatography and sRAGE by sequential sandwich immunoassay. Mean age was 71 ± 11 years, 62% were men, and mean left ventricular ejection fraction was 0.32 ± 0.14. At baseline, mean CML level was 2.16 ± 0.73 μmol/L, median pentosidine was 0.043 (0.030-0.074) μmol/L, and median sRAGE level was 2.92 (1.90-4.59) ng/mL. CML and pentosidine levels were independently related to the composite end-point (HR, 1.20 per SD; 95% CI,1.05-1.37; P = .01 and HR, 1.15 per SD; 95% CI, 1.00-1.31; P = .045, respectively) and HF hospitalization (HR, 1.27 per SD; 95% CI, 1.10-1.48; P = .001 and HR, 1.27 per SD; 95% CI, 1.10-1.47; P = .001, respectively). Furthermore, CML levels were independently related to increased mortality (P = .006). Whereas sRAGE levels were univariately predictive for outcome, in multivariate models sRAGE did not reach statistical significance. In HF patients, both CML and pentosidine predict HF hospitalization and the combined primary end-point (mortality or HF-hospitalization), whereas sRAGE did not predict events. In addition, CML was significantly and independently associated with a higher risk for mortality.

Dynamics of Circulating Ligands and Soluble Receptor for Advanced Glycation End-Product in Liver Transplantation

Background and aim: The ligand-receptor for advanced glycation end products (RAGE) pathway is involved in liver injury and animal testing have highlighted that the RAGE blockade attenuates the extent of the liver injury. A truncated isoform of the RAGE (endogenous secreted RAGE, esRAGE), consisting of the extracellular ligand-binding domain only, is detectable as circulating soluble form (sRAGE) in the blood. These latter, acting as decoy, can contribute to the removal of circulating RAGE- ligands. Objective of this study is understand the hepatic expression of both RAGE isoforms (full-length and truncated), and kinetics of the RAGE-ligands and sRAGE plasma levels in patients undergoing liver transplantation (LT) and compared them with healthy donors. Methods: We prospectively included twenty four adult LT recipients (52.7 ± 9.2 years) of primary whole-size grafts by deceased donors (60.4 ± 17.9 years). On both LT recipients and donors, we measured the transcriptional expression of hepatic tissue RAGE and esRAGE, the plasma levels of the RAGE-ligands - N(epsilon)-carboxymethyllysine (CML) and high-mobility group protein 1 (HMGB-1) - and circulating sRAGE. In LT recipient CML, HMGB-1 and sRAGE plasma levels were measured before LT, after graft reperfusion, 1, 7, 30 and 90 days after LT. Results: In LT recipients the hepatic RAGE and esRAGE mRNA levels were higher than in healthy donors (p< 0.01 and p=0.02 respectively). The tissue full-length RAGE inversely correlated with antithrombin III (β= - 0.58, p = 0.013) and cholinesterase plasma levels (β= -0.717, p= 0.0018) and tended to directly correlate with MELD score (β= 0.422, p= 0.063). Basal plasma levels CML, but not sRAGE and HMGB-1, were higher in LT recipients than in healthy donors (p< 0.05). At follow-up CML levels decreased after graft reperfusion (p = 0.0001) while returned progressively to basal values during the follow-p. Instead, HMGB-1, increased after graft reperfusion (p = 0.0001) and returned suddenly to basal values one day after LT. The basal HMGB-1 correlated directly with MELD score (β= 0.448, p= 0.05). The plasma levels of sRAGE did not change significantly soon after LT while decreased seven days after LT (p = 0.0001) and remained constantly low during follow-up. Conclusions: The high levels of RAGE and esRAGE tissue expression in the end-stage liver failure highlight the involvement of the RAGEligand axis in liver injury. The circulating CML accumulation and the rapid increase of HMGB-1 followed by a dramatic decline of the protective sRAGE could have deleterious consequences on graft survival and long term outcomes in LT recipients.

Anti-oxidative, anti-glycative and anti-apoptotic effects of oleanolic acid in brain of mice treated by d-galactose

Anti-oxidative, anti-glycative and anti-apoptotic effects of oleanolic acid in brain from d-galactose treated mice were examined. Oleanolic acid at 0.05%, 0.1% and 0.2% was supplied to mice for 10wk. d-Galactose treatment increased reactive oxygen species and protein carbonyl levels (P<0.05), and reduced activity and protein production of glutathione peroxide, superoxide dismutase and catalase in mice brain (P<0.05). Oleanolic acid intake dose-dependently lowered reactive oxygen species and protein carbonyl levels (P<0.05), and retained activity and expression of these enzymes (P<0.05). Brain levels of carboxymethyllysine, pentosidine and methylglyoxal were significantly increased in d-galactose treated mice (P<0.05). Oleanolic acid intake significantly decreased the level of these parameters (P<0.05). d-Galactose treatments enhanced brain activity and protein expression of aldose reducatse (AR); and declined glyoxalase I (GLI) activity and expression (P<0.05). Oleanolic acid intake dose-dependently diminished AR activity and expression (P<0.05), only at 0.2% retained GLI activity and expression (P<0.05). d-Galactose treatment up-regulated the activity, mRNA expression and protein production of nuclear factor-κB (NF-κB) p65, Bax and cleaved caspase-3 (P<0.05), as well as suppressed Bcl-2 production (P<0.05). Oleanolic acid intake at 0.1% and 0.2% suppressed NF-κB p65, Bax and cleaved caspase-3 production, and retained Bcl-2 expression (P<0.05). These findings support that oleanolic acid may be a potent neuro-protective agent against aging.

The Associations of Advanced Glycation End Products and Its Soluble Receptor with Pancreatic Cancer Risk: A Case–Control Study within the Prospective EPIC Cohort

Advanced glycation end products (AGE) and their receptors (RAGE) have been implicated in cancer development through their proinflammatory capabilities. However, prospective data on their association with cancer of specific sites, including pancreatic cancer, are limited. Prediagnostic blood levels of the AGE product Nε-(carboxymethyl)lysine (CML) and the endogenous secreted receptor for AGE (esRAGE) were measured using ELISA in 454 patients with exocrine pancreatic cancer and individually matched controls within the European Prospective Investigation into Cancer and Nutrition (EPIC). Pancreatic cancer risk was estimated by calculating ORs with corresponding 95% confidence intervals (CI). Elevated CML levels tended to be associated with a reduction in pancreatic cancer risk [OR = 0.57 (95% CI, 0.32-1.01) comparing highest with lowest quintile), whereas no association was observed for esRAGE (OR = 0.98; 95% CI, 0.62-1.54). Adjustments for body mass index and smoking attenuated the inverse associations of CML with pancreatic cancer risk (OR = 0.78; 95% CI, 0.41-1.49). There was an inverse association between esRAGE and risk of pancreatic cancer for cases that were diagnosed within the first 2 years of follow-up [OR = 0.46 (95% CI, 0.22-0.96) for a doubling in concentration], whereas there was no association among those with a longer follow-up (OR = 1.11; 95% CI, 0.88-1.39; P(interaction) = 0.002). Our results do not provide evidence for an association of higher CML or lower esRAGE levels with risk of pancreatic cancer. The role of AGE/RAGE in pancreatic cancer would benefit from further investigations.

Reduced microvascular density in non-ischemic myocardium of patients with recent non-ST-segment-elevation myocardial infarction

BackgroundMyocardial microvascular dysfunction has been implicated in the pathogenesis of myocardial infarction (MI). We tested the hypothesis that patients with MI have lower microvasculature density in myocardium remote from the site of infarction than patients with similar extent of coronary artery disease (CAD) without MI and examined the relationship between myocardial capillary length density and plasma levels of angiogenesis-related biomarkers. MethodsWe analyzed biopsies from non-ischemic left ventricular (LV) myocardium and measured plasma levels of angiogenesis-related biomarkers in patients undergoing coronary artery bypass graft surgery, 57 without previous MI (no-MI) and 27 with recent non-ST-segment-elevation MI (NSTEMI). Comparison was made with biopsies from 31 aortic stenosis (AS) patients and 6 patients with “normal” LV without CAD. ResultsMyocardial microvascular density of NSTEMI patients was approximately half the density of no-MI patients, and similar to AS patients. Whereas the reduced microvascular density of AS patients was accounted for by their cardiomyocyte hypertrophy, this was not the case for NSTEMI patients, who had higher diffusion radius/cardiomyocyte width ratio than no-MI, “normal” LV, and AS patients. NSTEMI patients had lower plasma levels of carboxymethyl lysine and low molecular weight fluorophores, higher vascular endothelial growth factor (VEGF) receptor-1/VEGF-A ratio, and higher endostatin and hepatocyte growth factor levels than no-MI patients. ConclusionsRecent MI was associated with reduced microvasculature density in myocardium remote from the site of infarction and alteration in plasma levels of angiogenesis-related biomarkers.

Peripheral RAGE (Receptor for Advanced Glycation Endproducts)-ligands in normal pregnancy and preeclampsia: novel markers of inflammatory response

Inflammatory response in preeclampsia (PE) is a key feature in its pathophysiology. Advanced Glycation Endproducts (AGEs), receptors for AGEs (RAGE), and RAGE ligands are involved in systemic inflammation in various pathological conditions. In this study, we measured serum RAGE ligands in normal pregnancy controls and PE patients. Levels of Carboxymethyl Lysine (CML), HMGB1 and S100A12/EN-RAGE were measured in thirty-three normal pregnant women 3 times at 10-12 (1st measurement), 28 (2nd measurement), and 36 (3rd measurement) weeks during gestation for paired analysis. We also measured those in serum samples from 17 severe PE patients at admission using ELISA. Early onset (EO, <32 weeks) and late onset (LO, ≥32 weeks) PE patients were compared with the 2nd and 3rd measurements of normal controls, respectively. CML and HMGB1 did not change during normal pregnancy. However, S100A12/EN-RAGE decreased from the 1st to 2nd measurement (P<0.0001). Across all PE patients, serum CML was unaltered, while HMGB1 significantly increased compared to 2nd (P=0.0002) and 3rd (P<0.0001) measurement as well as individually compared to both EO (P=0.018) and LO groups (P=0.0001). S100A12 in all PE patients increased over 2nd (P=0.0015) and 3rd (P=0.0002) measurements, although only LO was significantly increased compared to the 3rd measurement (P=0.0005). Our data suggest that patterns of serum RAGE ligand concentration indicate different inflammatory pathways in normal pregnancy, EO-PE, and LO-PE.

Circulating selenium and carboxymethyl-lysine, an advanced glycation endproduct, are independent predictors of anemia in older community-dwelling adults

ObjectiveTo assess whether selenium and carboxymethyl-lysine (CML), two biomarkers of oxidative stress, are independent predictors of anemia in older community-dwelling adults. MethodsPlasma levels of selenium, CML, folate, vitamin B12, and testosterone and markers of iron status and inflammation were measured at baseline in 1036 adults at least 65 y old in the Invecchiare in Chianti Study, a population-based cohort study of aging in Tuscany, Italy, and examined in relation to prevalent anemia and incident anemia over 6 y of follow-up. ResultsAt enrollment, 11.6% of participants were anemic. Of 472 participants who were non-anemic at enrollment, 72 (15.3%) developed anemia within 6 y of follow-up. At enrollment, plasma CML in the highest quartile (>425 ng/mL) and plasma selenium in the lowest quartile (<66.6 μg/L) predicted incident anemia (hazard ratio 1.67, 95% confidence interval 1.07–2.59, P = 0.02; hazard ratio 1.55, 95% confidence interval 1.01–2.38, P = 0.05, respectively) in a multivariate Cox proportional hazards model that adjusted for age, education, body mass index, cognition, inflammation, red blood cell distribution width, ferritin, vitamin B12, testosterone, and chronic diseases. ConclusionElevated plasma CML and low plasma selenium are long-term independent predictors of anemia in older community-dwelling adults. These findings support the idea that oxidative stress contributes to the development of anemia.

Decreased plasma sRAGE levels in COPD: influence of oxygen therapy

Chronic obstructive pulmonary disease (COPD) is associated with systemic inflammation and oxidative stress. N(ε) -(carboxymethyl) lysine (CML), an advanced glycation end product (AGE) and the soluble decoy receptor, sRAGE, are exciting new molecules linked to oxidative stress and inflammation. Here the levels of plasma sRAGE and CML were determined and their variation in relation to lung function, external long-term oxygen therapy (LTOT) and plasma levels of inflammatory molecules in COPD evaluated. Plasma sRAGE and CML levels were measured by ELISA in 146 patients with stable COPD and 81 healthy subjects, subgrouped from a larger case-control study and matched for age, gender and pack-years smoked. Decreased levels of plasma sRAGE and no significant difference in levels of plasma CML were found in patients with COPD in comparison with controls. In the total group, plasma sRAGE was positively associated with FEV(1) and forced vital capacity and negatively with pack-years smoked. In patients receiving LTOT, levels of plasma sRAGE were lower compared with those without LTOT. Only in controls, a weak correlation was found between plasma sRAGE and CML. sRAGE did not correlate with measured inflammatory markers, whereas CML was negatively correlated with fibrinogen. Plasma sRAGE levels are lower in patients with COPD compared with healthy control subjects, and even lower levels in patients receiving LTOT. Because sRAGE correlated with lung function only in the whole group, sRAGE can be considered a marker of COPD, but not of disease severity. A lack of clear association between sRAGE, CML and systemic inflammation is furthermore evident.

Olmesartan Medoxomil Is Associated with Decreased Plasma AGEs, Pentosidine, and N-(Epsilon)-Carboxymethyl-Lysine Levels in Hemodialysis Patients

Background. Advanced glycation end products (AGEs) are associated with comorbidity and death among patients on hemodialysis (HD). Angiotensin II type 1 receptor blockers (ARBs) can decrease the formation of AGEs in vitro. This study examines the ability of various ARBs to decrease plasma AGE levels in hypertensive patients on HD. Methods. This preliminary randomized prospective study included 24 hypertensive patients on HD who were treated with candesartan (8 mg/day). The patients were randomly assigned to an olmesartan (20 mg/day, n = 12) or a telmisartan (40 mg/day, n = 12) group and followed up 24 weeks. Blood pressure was monitored before each HD session, and plasma pentosidine, N-(epsilon)-carboxymethyl-lysine (CML), serum malondialdehyde-low-density lipoprotein (LDL), high-sensitive CRP, and serum total free radical (TFR) were measured at baseline, and at 4, 12, and 24 weeks. Results. Olmesartan was significantly associated with decreased systolic blood pressure compared with telmisartan. After 24 weeks of treatment, plasma pentosidine and CML levels were significantly decreased and serum TFR levels tended to be decreased in the olmesartan group, but remained unchanged in the telmisartan group. Conclusions. These results suggest that olmesartan can help to decrease plasma AGE levels in patients on HD.

PS6 - 31. Plasma levels of Nε-(carboxymethyl)lysine are lower in impaired glucose metabolism and type 2 diabetes, and this is partly explained by central obesity: The Hoorn and CODAM studies

Increased formation of advanced glycation endproducts (AGEs) constitutes a potential mechanism by which hyperglycaemia and its immediate biochemical sequelae induce micro- and macrovascular complications in diabetes. In type 1 diabetes, circulating levels of AGEs, including the major AGE Ne-(carboxymethyl)lysine (CML), have been shown to be increased and associated with the development of cardiovascular disease (CVD). In contrast, the exact role of circulating CML in type 2 diabetes (T2DM) remains unclear, because remarkably, so far no consistent data on levels of plasma CML have been described in individuals with vs. without T2DM.

Two Fluorescent Wavelengths, 440ex/520emnm and 370ex/440emnm, Reflect Advanced Glycation and Oxidation End Products in Human Skin Without Diabetes

Advanced glycation end products (AGEs) and oxidation products (OPs) play an important role in diabetes complications, aging, and damage from sun exposure. Measurement of skin autofluorescence (SAF) has been promoted as a noninvasive technique to measure skin AGEs, but the actual products quantified are uncertain. We have compared specific SAF measurements with analytically determined AGEs and oxidative biomarkers in skin collagen and determined if these measurements can be correlated with chronological aging and actinic exposure. SAF at four excitation (ex)/emission (em) intensities was measured on the upper inner arm ("sun protected") and dorsal forearm ("sun exposed") in 40 subjects without diabetes 20-60 years old. Skin collagen from the same sites was analyzed by liquid chromatography-tandem mass spectrometry for three AGEs-pentosidine, carboxymethyllysine (CML), and carboxyethyllysine (CEL)-and the OP methionine sulfoxide (MetSO). There was poor correlation of AGE-associated fluorescence spectra with AGEs and OP in collagen, with only pentosidine correlating with fluorescence at 370(ex)/440(em) nm. A little-studied SAF (440(ex)/520(em) nm), possibly reflecting elastin cross-links, correlated with all AGEs and OPs. Levels of CML, pentosidine, and MetSO, but not SAF, were significantly higher in sun-exposed skin. These AGEs and OPs, as well as SAF at 370(ex)/440(em) nm and 440(ex)/520(em) nm, increased with chronological aging. SAF measurements at 370(ex)/440(em) nm and 335(ex)/385(em) nm, except for pentosidine, which correlated with fluorescence at 370(ex)/440(em), correlate poorly with glycated and oxidatively modified protein in human skin and do not reflect actinic modification. A new fluorescence measurement (440(ex)/520(em) nm) appears to reflect AGEs and OPs in skin.

Study of the urinary and faecal excretion of N ε-carboxymethyllysine in young human volunteers

The dietary habits of the adolescent population with a high intake of snack and fast foods mean that they consume a high rate of which in turn leads to the development of different degenerative disorders. There are few studies available on MRP absorption and metabolism. We investigated the effects of a MRP-high and a MRP-low diet on carboxymethyllysine (CML) intake and excretion in 11-14 years adolescent males. In a 2-period crossover trial, 20 healthy subjects were randomly assigned to two groups. The first group consumed the MRP-low diet for 2 weeks, observed a 40-day washout period, and then consumed the MRP-high diet for 2 weeks. The second group received the diets in the reverse order. Subjects collected urine and faeces on the last 3 days of each dietary period. The consumption of the MRP-high diet led to a higher CML input (P < 0.05) (11.28 vs. 5.36 mg/day CML for MRP-high and -low diet, respectively). In parallel, the faecal excretion was also greater (P < 0.05) (3.52 vs. 1.23 mg/day CML, respectively) and proportional to the dietary intake. The urinary elimination of CML was not increased significantly when the MRP-high diet was consumed compared to consumption of the MRP-low diet, and was not proportional to the dietary exposure of CML. In conclusion it was shown that CML absorption and faecal excretion were highly influenced by dietary CML levels. Since the compound has long-term effects on health, an excessive intake deserves attention, especially in a population nutritionally at risk as adolescents.

Endogenous formation of Nε-(carboxymethyl)lysine is increased in fatty livers and induces inflammatory markers in an in vitro model of hepatic steatosis

Increased lipid peroxidation and inflammation are major factors in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). A lipoxidation product that could play a role in the induction of hepatic inflammation is N(ε)-(carboxymethyl)lysine (CML). The aim of the present study was to investigate the relationship between steatosis and CML and to study the role of CML in hepatic inflammation. We included 74 obese individuals, which were categorized into 3 groups according to the grade of hepatic steatosis. CML accumulation in liver biopsies was assessed by immunohistochemistry and plasma CML levels were measured by mass spectrometry. Plasma CML levels were also determined in the hepatic artery, portal, and hepatic vein of 22 individuals, and CML fluxes across the liver were calculated. Hepatocyte cell lines were used to study CML formation during intracellular lipid accumulation and the effect of CML on pro-inflammatory cytokine expression. Gene expression levels of the inflammatory markers were determined in liver biopsies of the obese individuals. CML accumulation was significantly associated with the grade of hepatic steatosis, the grade of hepatic inflammation, and gene expression levels of inflammatory markers PAI-1, IL-8, and CRP. Analysis of CML fluxes showed no release/uptake of CML by the liver. Lipid accumulation in hepatocytes, induced by incubation with fatty acids, was associated with increased CML formation and expression of the receptor for advanced glycation endproducts (RAGE), PAI-1, IL-8, IL-6, and CRP. Pyridoxamine and aminoguanidine inhibited the endogenous CML formation and the increased RAGE, PAI-1, IL-8, IL-6, and CRP expression. Incubation of hepatocytes with CML-albumin increased the expression of RAGE, PAI-1, and IL-6, which was inhibited by an antibody against RAGE. Accumulation of CML and a CML-upregulated RAGE-dependent inflammatory response in steatotic livers may play an important role in hepatic steatosis and in the pathogenesis of NAFLD.