Plasma Carboxymethyl)lysine Research Articles

Phloroglucinol ameliorated methylglyoxal induced harmful effects in rats.

Glycation is among the underlying mechanisms attributed to ageing and associated morbidities. There is no drug available to combat this deleterious phenomenon. The present study aimed to explore phloroglucinol (PHL) for its anti-glycation potential at preclinical level. The rats were treated with methylglyoxal (MGO, 17.25 mg/kg, i.p. for 14 days) to induce glvcative stress. The treatment groups received additional administration of test drug (PHL; 0.25mg/kg, 0.5mg/kg, and 1mg/kg) or standard aminoguanidine (AG, 50 mg/kg) or saline (control, 5ml/kg). During 14 days, the weight and food intake was noted. Afterwards, the cognitive function was evaluated using Morris Water Maze (MWM) while hepatic and renal functions were assessed through liver function test (bilirubin, alkaline phosphatase, SGPT, and SGOT) and creatinine respectively, using chemical analyzer. The carboxymethyllysine (CML) levels were quantified in the blood using ELISA technique. Histopathological study was performed on the brain, liver, and kidney using H&E staining. Additionally, the qPCR was used to quantify the expression of TNF-α, RAGE and BACE-1 (brain), RAGE, TNF-α, and glyoxalase-I (liver) and RAGE, TNF-α, and VEGF (kidney), while glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as a reference housekeeping gene. The data regarding weight and food intake did not reveal significant alterations. In MWM, the MGO treatment caused significant increase in the time to reach target quadrant, while decrease in the time spent in target quadrant and number of crossings through platform position. All these effects were inhibited by both AG and PHL. The navigation maps also exhibit that the retention of spatial memory. Additionally, the MGO-induced alteration in hepatic and renal function indicators was ameliorated by both AG and PHL treatments. The plasma CML levels were found to be elevated following MGO treatment, while the concomitant administration of AG and PHL has resisted this raise. Histopathological assessment revealed no specific pathology in liver kidney and brain tissues. The qPCR data revealed enhanced expression of all genes, especially TNF-α and BACE, which were found to be reduced following both AG and PHL treatments. PHL prevented the brain, hepatic, and renal impairments caused by MGO induced glycative stress. Hence, the PHL, a clinically used anti-spasmodic drug, presents itself as a potential candidate to be repurposed as anti-glycation drug.

Therapeutic role of hesperidin in collagen-induced rheumatoid arthritis through antiglycation and antioxidant activities.

Rheumatoid arthritis (RA), a chronic inflammatory disease, and its exact aetiology is not defined clearly. The free radicals produced in large amount in RA are associated with alteration in molecular structure resulting in glycation of proteins. As a result of glycation, advanced glycation end products (AGEs) produced. In this study, collagen type II suspension was injected into Wistar rats to make RA model of rats. Simultaneously, hesperidin 50 mg kg-1 body weight was orally administrated to the rats for 21 days. X-rays of the rat hind paws were analyzed and found to be significantly effective against bone loss after treatment with hesperindin. Nε -(carboxymethyl)lysine (CML) and pentosidine (PTD) concentrations in collagen-induced RA plasma were determined as 565.29 ± 30.15 and 37.23 ± 1.02 ng ml-1 , respectively, while CML and PTD in IgG were 6.63 ± 0.44 ng mg-1 IgG and 425.33 ± 37.26 ng g-1 IgG, respectively. After treatment with hesperidin, the elevated levels of CML in plasma and in IgG were significantly (p < 0.001) lowered to 450.95 ± 15.05 mg ml-1 and 5.23 ± 0.27 ng mg-1 IgG, respectively. Similarly, concentrations of PTD in plasma andIgG of rats treated with hesperidin were 28.46 ± 1.20 ng ml-1 and 359.35 ± 31.11 ng g-1 IgG, respectively. Thus, after treatment with drug, plasma CML and IgG PTD levels were restored as 93% and 16%, respectively, through free radical scavenging activity of hesperidin resulting in alleviation of RA disease by decreasing the AGEs concentrations. Therefore, use of hesperidin may be useful to alleviate severity of RA disease.

Ezetimibe attenuates experimental diabetes and renal pathologies via targeting the advanced glycation, oxidative stress and AGE-RAGE signalling in rats

The current in-vivo study was premeditated to uncover the protective role of ezetimibe (EZ) against advanced glycation endproducts (AGEs)-related pathologies in experimental diabetes. Our results showed that EZ markedly improved the altered biochemical markers of diabetes mellitus (DM) (FBG, HbA1c, insulin, microalbumin, and creatinine) and cardiovascular disease (in-vivo lipid/lipoprotein level and hepatic HMG-CoA reductase activity) along with diminished plasma carboxymethyl-lysine (CML) and renal fluorescent AGEs level. Gene expression study revealed that EZ significantly down-regulated the renal AGEs-receptor (RAGE), nuclear factor-κB (NFκB-2), transforming growth factor-β (TGF-β1), and matrix metalloproteinase-2 (MMP-2) mRNA expression, however, the neuropilin-1 (NRP-1) mRNA expression was up-regulated. In addition, EZ also maintained the redox status via decreasing the lipid peroxidation and protein-bound carbonyl content (CC) and increasing the activity of high-density lipoprotein (HDL)-associated-paraoxonase-1 (PON-1) and renal antioxidant enzymes as well as also protected renal histopathological features. We conclude that EZ exhibits antidiabetic and reno-protective properties in diabetic rats.

The effect of Kappaphycus alvarezii fraction on plasma glucose, Advanced Glycation End-products formation, and renal RAGE gene expression

BackgroundKappaphycus alvarezii (Doty) Doty ex P.C.Silva is a red algae with antioxidant and antiglycation activities. Algae still have not been widely used for treating diabetes, especially to prevent complications. The purpose of this study was to examine the effect of active fractions from Kappaphycus alvarezii on plasma glucose level, glycation process and renal RAGE gene expression. MethodsThis study used bioassay-guided fractionation, consisting of three stages: extraction, partition, and fractionation. These processes were monitored with Thin Layer Chromatography and the BSA-Glucose method to select the best extract with antiglycation activity (calculated as the percentage of inhibition and IC50). The selected active fraction from four fractions was further used for in vivo study, which was conducted with hyperglycemic Wistar male rats. Plasma glucose level was measured using GOD-PAP methods, while plasma glycated albumin (GA) and Nε- (carboxymethyl) lysine (CML) levels were measured using ELISA. Renal RAGE gene expression was analyzed using qPCR. ResultsFraction II was selected as the active fraction of Kappaphycus alvarezii showing antiglycation activity with the highest percentage of inhibition and the lowest IC50. This fraction significantly reduced plasma GA and CML levels, but it did not significantly reduce plasma glucose level. Furthermore, renal RAGE gene expression was lower in the diabetic rat group treated with this active fraction compared to the untreated group. ConclusionsThis study successfully identified an active fraction of Kappaphycus alvarezii with antiglycation activity to reduce plasma GA and CML levels as well as renal RAGE gene expression. Therefore, this fraction could be developed as a potential candidate for treating diabetes.

Dietary and Plasma Carboxymethyl Lysine and Tumor Necrosis Factor-α as Mediators of Body Mass Index and Waist Circumference among Women in Indonesia.

Dietary and plasma carboxymethyl lysine (dCML, pCML) and plasma tumor necrosis factor-α (pTNF-α) may be associated with obesity in affluent society. However, evidence in women from low-middle income countries with predominantly traditional diets is lacking. We investigated the mediator effects of dCML, pCML and pTNF-α on body mass index (BMI) and waist circumference (WC) among Indonesian women. A cross-sectional study was conducted among 235 non-diabetic, non-anemic and non-smoking women aged 19–50 years from selected mountainous and coastal areas of West Sumatra and West Java. Dietary CML, pCML, pTNF-α were obtained from 2 × 24-h recalls, ultra-performance liquid chromatography-tandem mass spectrometry and enzyme-linked immunosorbent assay, respectively. Between-group differences were analyzed by the Chi-square or Mann-Whitney test and mediator effects by Structural Equation Modeling. The medians and interquartile-ranges of dCML, pCML and pTNF-α were 2.2 (1.7–3.0) mg/day, 22.2 (17.2–28.2) ng/mL and 0.68 (0.52–1.00) IU/mL, respectively, and significantly higher in the WC ≥ 80 cm than in the WC < 80 cm group, but not in BMI ≥ 25 kg/m2 compared to BMI < 25 kg/m2 group. Plasma CML and pTNF-α were positively and directly related to WC (β = 0.21 [95% CI: 0.09, 0.33] and β = 0.23 [95% CI: 0.11, 0.35], respectively). Dietary CML that correlated with dry-heat processing and cereals as the highest contributions was positively related to WC (β = 0.33 [95% CI: 0.12, 0.83]). Ethnicity, level of education, intake of fat, and intake of energy contributed to dCML, pCML and pTNF-α, and subsequently affected WC, while only ethnicity contributed to BMI through dCML, pCML and pTNF-α (β = 0.07 [95% CI: 0.01, 0.14]). A positive direct effect of dCML on pCML and of pCML and pTNF-α on WC was seen among Indonesian women. Dietary CML seems to have several paths that indirectly influence the increases in WC if compared to BMI. Thus, intake of CML-rich foods should be reduced, or the foods consumed in moderate amounts to avoid the risk of central obesity in this population.

The improvement of oxidative stress by two proprietary herbal medicines in type 2 diabetes

ObjectiveTo evaluate the impact to oxidative stress, atherosclerosis and macrovascular disease by two proprietary herbal medicines including Ginkgo Leaf Tablets and Liuwei Dihuang Pills in type 2 diabetes. MethodsThe recruited 140 type 2 diabetes were randomly divided into the treatment group and control group which were both received basic diabetic management including anti-hyperglycemia, anti-hypertension, life style adjustment and health education etc. Additionally, the treatment group was given both Ginkgo Leaf Tablets and Liuwei Dihuang Pills while the control group was given placebos of Ginkgo Leaf Tablets and Liuwei Dihuang Pills. The relative clinical indexes about macrovascular events occurrence, atherosclerosis degree(IMT levels), oxidative stress in vivo(plasma carboxymethyl lysine(CML) and 8-isoprostane(8-IsoP) levels), plasma glucose, plasma lipid, blood pressure, other drugs usage situations and so on of two groups before and after consecutive 36-month treatment were accurately collected and statistically analyzed. ResultsThere were no significant differences of cardiovascular disease, cerebrovascular disease, IMT levels, plasma CML and 8-IsoP levels between the two groups before treatment. After 36-month treatment, the plasma CML and 8-IsoP levels of treatment group were both significantly lower than control group (CML: 312.4 ± 90.4 ng/ml versus 463.5 ± 97.2 ng/ml, P < 0.0001; 8-IsoP: 23.7 ± 9.5 pg/ml versus 62.6 ± 16.1 pg/ml, P < 0.0001) although this improvement was not shared with IMT and macrovascular events. ConclusionGinkgo Leaf Tablets and Liuwei Dihuang Pills are beneficial to oxidative stress which plays important role in diabetic atherosclerosis and macrovascular complications. The preventive and therapeutic values of herbal medicines will be proved in further diabetic complication researches.

Effects of a Low Advanced Glycation End Products Diet on Insulin Levels: The Feasibility of a Crossover Comparison Test

BackgroundAdvanced glycation end products (AGEs) are associated with diabetes mellitus. Digested food-derived AGEs have been implicated in the pathogenesis of AGE-related disorders, and restricting diet-derived AGEs improves insulin resistance in animal models. The AGE content in foods changes according to cooking method, and it is higher in baked or oven-fried foods than in those prepared by steaming or simmering. Here, we examined the feasibility of crossover comparison tests for determining how different cooking methods (normal diet vs. low-AGE diet) affect insulin levels in non-diabetic Japanese subjects.MethodsFive adult men and women (age, 41 ± 7 years; body mass index (BMI), 21.7 ± 2.6 kg/m2) were enrolled. The following dietary regimen was used: days 1 - 3, control meal; day 4, test meal (normal diet vs. low-AGE diet); day 5, washout day; and day 6, test meal. On days 4 and 6, blood samples were collected before and at 2, 4, and 6 h after meals.ResultsBlood levels of N-(carboxymethyl) lysine (CML) increased with dietary intake, but the increase was similar for the normal diet and low-AGE diet groups. Mean plasma glucose, insulin, triglycerides (TG), and CML did not differ significantly between the two groups. The area under the curve (AUC) for insulin levels was lower in the low-AGE diet group (d = 0.8). The sample size calculated from the effect size of the insulin AUC change was 22.ConclusionsTwenty-two subjects may be needed to investigate the changes in clinical parameters attributable to cooking method in non-diabetic Japanese subjects.

Dietary intake of advanced glycation endproducts is associated with higher levels of advanced glycation endproducts in plasma and urine: The CODAM study

Advanced glycation endproducts (AGEs) are formed by the reaction between reducing sugars and proteins. AGEs in the body have been associated with several age-related diseases. High-heat treated and most processed foods are rich in AGEs. The aim of our study was to investigate whether dietary AGEs, are associated with plasma and urinary AGE levels. In 450 participants of the Cohort on Diabetes and Atherosclerosis Maastricht study (CODAM study) we measured plasma and urine concentrations of the AGEs Nε-(carboxymethyl)lysine (CML), Nε-(1-carboxyethyl)lysine (CEL) and Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) using UPLC-MS/MS. We also estimated dietary intake of CML, CEL and MG-H1 with the use of a dietary AGE database and a food frequency questionnaire (FFQ). We used linear regression to investigate the association between standardized dietary AGE intake and standardized plasma or urinary AGE levels, after adjustment for age, sex, glucose metabolism status, waist circumference, kidney function, energy- and macro-nutrient intake, smoking status, physical activity, alcohol intake, LDL-cholesterol and markers of oxidative stress. We found that higher intake of dietary CML, CEL and MG-H1 was associated with significantly higher levels of free plasma and urinary CML, CEL and MG-H1 (βCML=0.253 (95% CI 0.086; 0.415), βCEL=0.194 (95% CI 0.040; 0.339), βMG-H1=0.223 (95% CI 0.069; 0.373) for plasma and βCML=0.223 (95% CI 0.049; 0.393), βCEL=0.180 (95% CI 0.019; 0.332), βMG-H1=0.196 (95% CI 0.037; 0.349) for urine, respectively). In addition, we observed non-significant associations of dietary AGEs with their corresponding protein bound plasma AGEs. We demonstrate that higher intake of dietary AGEs is associated with higher levels of AGEs in plasma and urine. Our findings may have important implications for those who ingest a diet rich in AGEs.

The effects of n-3 long-chain polyunsaturated fatty acid supplementation on AGEs and sRAGE in type 2 diabetes mellitus.

In diabetes mellitus, chronic hyperglycemia leads to formation of advanced glycation end products (AGEs). Binding of AGEs to receptors of AGE (RAGE) causes deleterious effects. In populations with a high consumption of n-3 long-chain polyunsaturated fatty acids, a lower prevalence of diabetes mellitus has been reported. We aimed to investigate the effects of n-3 fatty acid (EPA and DHA) supplementation on the levels of AGEs (carboxymethyl lysine (CML) and pentosidine), sRAGE, and nuclear factor kappa B (NF-kB) in type 2 diabetes mellitus (T2DM). T2DM patients (n = 38) treated with oral hypoglycemic agents, without insulin were supplemented with n-3 fatty acids (1.2g/day) for 2months. Plasma CML, pentosidine, sRAGE, and NF-kB levels were measured by ELISA both before and after the supplementation. n-3 fatty acid supplementation significantly reduced fasting glucose (p < 0.01), glycated hemoglobin (HbA1c) (p < 0.05), and pentosidine (p < 0.05) levels. The supplementation induced percentage changes in pentosidine and HbA1c and in pentosidine and creatinine were observed to be correlated (r = 0.349, p < 0.05) and (r = 0.377, p < 0.05), respectively. Waist circumference and systolic and diastolic pressures were significantly decreased due to n-3 supplementation (p < 0.001, p < 0.01, p < 0.01), respectively. Our results show that supplementation with n-3 fatty acid has beneficial effects on waist circumference; systolic and diastolic blood pressures; and the levels of glucose, HbA1c, and pentosidine in T2DM patients. However, the supplementation failed to decrease these parameters to the reference ranges for healthy subjects. In addition, the supplementation did not appear to induce any significant differences in CML, sRAGE, or NF-kB.

Advanced Glycation End Product (AGE) Accumulation in the Skin is Associated with Depression: The Maastricht Study.

Depression is a highly prevalent disease with a high morbidity and mortality risk. Its pathophysiology is not entirely clear. However, type 2 diabetes is an important risk factor for depression. One mechanism that may explain this association may include the formation of advanced glycation end products (AGEs). We therefore investigated the association of AGEs with depressive symptoms and depressive disorder. In addition, we examined whether the potential association was present for somatic and/or cognitive symptoms of depression. Cross-sectional data were used from the Maastricht Study (N = 862, mean age 59.8 ± 8.5 years, 55% men). AGE accumulation was measured with skin autofluorescence (SAF) by use of the AGE Reader. Plasma levels of protein-bound pentosidine were measured with high-performance liquid chromatography and fluorescence detection. Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) were measured with ultraperformance liquid chromatography and tandem mass spectrometry. Depressive symptoms and depressive disorder were assessed by the nine-item Patient Health Questionnaire and the Mini-International Neuropsychiatric Interview. Higher SAF was associated with depressive symptoms (β = 0.42, 95% CI 0.12-0.73, P = .007) and depressive disorder (OR = 1.42, 95% CI 1.04-1.95, P = .028) after adjustment for age, sex, type 2 diabetes, smoking, BMI, and kidney function. Plasma pentosidine, CML, and CEL were not independently associated with depressive symptoms and depressive disorder. This study shows that AGE accumulation in the skin is independently associated with higher levels of depressive symptoms and depressive disorder. This association is present for both somatic and cognitive symptoms of depression. This might suggest that AGEs are involved in the development of depression.

The Receptor for Advanced Glycation End Products (Rage) and Its Ligands in Plasma and Infrainguinal Bypass Vein

The aim was to investigate whether RAGE and its ligands are associated with infrainguinal bypass outcome in patients with and without diabetes. This was a prospective observational cohort. Patients (n = 68) with (n = 38) and without (n = 30) diabetes undergoing infrainguinal vein bypass for peripheral arterial disease were followed for 3 years. Endosecretory RAGE (esRAGE), S100A12, advanced glycation end products, and carboxymethyl-lysine (CML) were determined in plasma using ELISA. The influence of plasma levels on the main outcome (amputation free survival) was evaluated using Cox proportional hazard analysis. Plasma esRAGE, CML, and S100A12 in healthy controls (n = 30) without cardiovascular disease matched for sex and age were compared with patients, using the Mann—Whitney U test. Veins from bypass surgery procedures were stained and S100A12, RAGE, AGE, and CML were determined using immunohistochemistry. Forty-six patients survived with an intact leg during follow up. Seventeen died (median survival time 702 days, IQR 188-899 day), and six had amputations. High plasma S100A12 was associated with reduced amputation free survival (hazard ratio [HR] 2.99; 95% CI 1.24-7.24) when comparing levels above the 75th percentile with levels below. The increased risk was unchanged adjusting for age, sex, and diabetes. Diabetic patients had higher plasma S100A12 (11.75 ng/mL; 95% CI 8.12-15.38 ng/mL) than non-diabetic patients (5.0141 ng/mL; 95% CI 3.62-6.41 ng/mL), whereas plasma CML, esRAGE, and AGE were similar. Plasma CML and S100A12 were higher in patients than in controls (1.25 μg/mL, 95% CI 1.18-1.32 μg/mL vs 0.8925 μg/mL, 95% CI 0.82-0.96 μg/mL; and 8.7 μg/mL, 95% CI 6.52-10.95 μg/mL vs 3.47 μg/mL, 95% CI 2.95-3.99 μg/mL, respectively). The proportion of vein tissue stained for AGE (21%), RAGE (5%), CML (9%) and S100A12 (3%), were similar in patients with and without diabetes. Plasma S100A12 and CML are elevated in peripheral arterial disease and markers of RAGE and its ligands are found in vein used for bypass. This indicates a role for S100A12, CML, and RAGE in peripheral arterial disease complications by activation of the RAGE system.

The Receptor for Advanced Glycation End Products (Rage) and Its Ligands in Plasma and Infrainguinal Bypass Vein

The aim was to investigate whether RAGE and its ligands are associated with infrainguinal bypass outcome in patients with and without diabetes. This was a prospective observational cohort. Patients (n = 68) with (n = 38) and without (n = 30) diabetes undergoing infrainguinal vein bypass for peripheral arterial disease were followed for 3 years. Endosecretory RAGE (esRAGE), S100A12, advanced glycation end products, and carboxymethyl-lysine (CML) were determined in plasma using ELISA. The influence of plasma levels on the main outcome (amputation free survival) was evaluated using Cox proportional hazard analysis. Plasma esRAGE, CML, and S100A12 in healthy controls (n = 30) without cardiovascular disease matched for sex and age were compared with patients, using the Mann-Whitney U test. Veins from bypass surgery procedures were stained and S100A12, RAGE, AGE, and CML were determined using immunohistochemistry. Forty-six patients survived with an intact leg during follow up. Seventeen died (median survival time 702 days, IQR 188-899 day), and six had amputations. High plasma S100A12 was associated with reduced amputation free survival (hazard ratio [HR] 2.99; 95% CI 1.24-7.24) when comparing levels above the 75th percentile with levels below. The increased risk was unchanged adjusting for age, sex, and diabetes. Diabetic patients had higher plasma S100A12 (11.75 ng/mL; 95% CI 8.12-15.38 ng/mL) than non-diabetic patients (5.0141 ng/mL; 95% CI 3.62-6.41 ng/mL), whereas plasma CML, esRAGE, and AGE were similar. Plasma CML and S100A12 were higher in patients than in controls (1.25 μg/mL, 95% CI 1.18-1.32 μg/mL vs. 0.8925 μg/mL, 95% CI 0.82-0.96 μg/mL; and 8.7 μg/mL, 95% CI 6.52-10.95 μg/mL vs. 3.47 μg/mL, 95% CI 2.95-3.99 μg/mL, respectively). The proportion of vein tissue stained for AGE (21%), RAGE (5%), CML (9%) and S100A12 (3%), were similar in patients with and without diabetes. Plasma S100A12 and CML are elevated in peripheral arterial disease and markers of RAGE and its ligands are found in vein used for bypass. This indicates a role for S100A12, CML, and RAGE in peripheral arterial disease complications by activation of the RAGE system.

Plasma Levels of Pentosidine, Carboxymethyl-Lysine, Soluble Receptor for Advanced Glycation End Products, and Metabolic Syndrome: The Metformin Effect.

Metabolic syndrome (MetS) is considered one of the most important public health problems. Several and controversial studies showed that the role of advanced glycation end products (AGEs) and their receptor in the development of metabolic syndrome and therapeutic pathways is still unsolved. We have investigated whether plasma pentosidine, carboxymethyl-lysine (CML), and soluble receptor for advanced glycation end products (sRAGE) levels were increased in patients with MetS and the effect of metformin in plasma levels of pentosidine, CML, and sRAGE. 80 control subjects and 86 patients were included in this study. Pentosidine, CML, and sRAGE were measured in plasma by enzyme-linked immunosorbent assay (ELISA). Plasma pentosidine, CML, and sRAGE levels were significantly increased in patients compared to control subjects (P < 0.001, P < 0.001, and P = 0.014, resp.). Plasma levels of pentosidine were significantly decreased in patients who received metformin compared to untreated patients (P = 0.01). However, there was no significant difference between patients treated with metformin and untreated patients in plasma CML levels. Plasma levels of sRAGE were significantly increased in patients who received metformin and ACE inhibitors (P < 0.001 and P = 0.002, resp.). However, in a multiple stepwise regression analysis, pentosidine, sRAGE, and drugs treatments were not independently associated. Patients with metabolic syndrome showed increased levels of AGEs such as pentosidine and CML. Metformin treatment showed a decreased level of pentosidine but not of CML. Therapeutic pathways of AGEs development should be taken into account and further experimental and in vitro studies merit for advanced research.

Targeting Advanced Glycation End Products in Cardiac Surgery: The Unexplored Alternative.

Dear Editor, In the previous issue of “Research in Cardiovascular Medicine”, our group presented a review of pharmacologic approaches against advanced glycation end products (AGEs) in diabetic cardiovascular disease (1). Over the last years, clinicians' viewpoint about diabetes moved from “glycaemia” to “glycaemia, glycated haemoglobin and glycation pathway”, and the recognized pivotal role of AGEs in genesis and progression of cardiovascular disease led to the development of new anti-AGEs compounds, with alagebrium, statins and thiazolidinediones being the most promising. These pharmacological studies were always performed in cardiology settings, but evidence-based medicine states that diabetic patients are more likely to have long-term benefits with surgical than percutaneous procedures (2). So, what is the state-of-the-art about AGEs awareness and anti-AGEs treatment in cardiac surgery? AGEs levels and its pathways are closely related to post-operative outcomes and length of hospital stay. In fact, higher pre-operative plasma soluble receptor for AGEs (sRAGE) values are associated with prolonged duration of care (3), and higher carboxy-methyl-lysine (CML) values correlate with prolonged ventilation time after cardiac surgery (4). Also, sRAGE are a sensitive and early marker of post-operative lung distress, and this represents the most attractive field of investigation in both paediatric and adult procedures (5-7). sRAGE level was also reported to be lower in patients scheduled for surgical aortic valve replacement compared to healthy subjects, and its role in the pathogenesis of aortic valve stenosis is being currently investigated (8). As for diastolic dysfunction, plasma CML values are associated with mitral E/A ratio in patients undergoing coronary artery bypass graft surgery (9). The prognostic implication of AGEs appears also in orthotopic heart transplantation, as AGEs deposition in diabetic patients was related to acute rejection episodes (10). However, despite its potential interest, there is no unanimous consensus in the literature regarding the optimal technique for AGEs measurements. Plasma essays, skin autofluorescence and immunochemical methods have been differently reported throughout the literature and this complicates the possibility of a clear comparisons among the clinical studies (11). In the next years, the standardization of AGEs measurement would improve the actual understanding of the mechanisms underlying AGEs biological pathways and the effects of anti-AGEs treatments. As far as pharmacologic approaches against AGEs are concerned, despite the flourishing production of literature in the field of cardiology on this topic, there are no current or terminated clinical trials investigating anti-AGEs role in cardiac surgery. This may be because newer drugs, such as alagebrium and aminoguanidine, are associated with side effects that seem to outnumber the potential benefits in AGEs modification. On the other hand, statins and thiazolidinediones are well-known drugs exerting significant anti-AGEs effect, but targeted clinical trials are still lacking. Thus the under-use of anti-AGEs compounds may be due to the under-comprehension of their potential benefits, which can be evaluated only during a long-term time span. In fact, notwithstanding the general lack of clinical trial on anti-AGEs treatments, the available studies only focus on short-term follow up which might elucidate side effects of anti-AGEs compounds, but cannot reveal their actual long-term benefits in the progression of diabetic cardiovascular disease. Alexis Carrel, French surgeon, Nobel laureate in 1912, wrote that “A few observation and much reasoning lead to error; many observations and a little reasoning to truth”. Studies on anti-AGEs compounds showed benefits in arterial compliance, ventricular stiffening and slowed progression of diabetic vascular disease. Spurred by the wave of optimism regarding the potential of anti-AGEs compounds, it seems to be right moment to introduce anti-AGEs drugs also into cardiac surgery study protocols, using newer safe compounds such as alagebrium and assessing the modification in the glycation pathway caused by known compounds such as statins and thiazolidinediones. As mentioned above, some investigators introduced interesting associations between AGEs and cardiac outcomes in cardiac surgery, but more structured approach are needed in this context. Also, considering the role of AGEs as marker of disease progression in the complex scenario of diabetes, measurement of AGEs levels should become part of the routine evaluation of the diabetic patient, not only to monitor blood glucose effects, but also to predict potential cardiac complications and provide prompt treatment. We hope that our considerations might shed light on this shaded topic in cardiac surgery and foster the scientific debate on this argument.

Protein-Bound Plasma Nε-(Carboxymethyl)lysine Is Inversely Associated With Central Obesity and Inflammation and Significantly Explain a Part of the Central Obesity-Related Increase in Inflammation: The Hoorn and CODAM Studies.

Adipose tissue inflammation contributes to the development of complications, such as insulin resistance and type 2 diabetes mellitus. We previously reported that plasma levels of N(ε)-(carboxymethyl)lysine (CML) were decreased in obese subjects resulting from CML accumulation in adipose tissue and that this CML accumulation plays an important role in adipose tissue inflammation. The objective of this study is to investigate associations between obesity (body mass index, waist circumference, and trunk fat mass), plasma CML (as an inversely correlated marker of CML accumulation in adipose tissue), and low-grade inflammation (LGI) in a large sample of individuals whose weight status ranged from normal to morbid obesity. We studied 1270 individuals of the Cohort on Diabetes and Atherosclerosis Maastricht Study and Hoorn Study, in whom protein-bound CML levels were measured by UPLC-Tandem MS (ultra performance liquid chromatography-tandem mass spectrometry), and 6 inflammatory markers were measured with multiarrays. These inflammatory markers were compiled into an LGI score. Multiple linear regression, adjusted for covariates, showed that (1) waist circumference was inversely associated with protein-bound CML plasma levels (standardized regression coefficient [β]=-0.357 [95% confidence interval: -0.414; -0.301]); (2) protein-bound CML was inversely associated with LGI score (β=-0.073 [-0.130;-0.015]); and (3) the association between waist circumference and LGI (β=0.262 [0.203;0.321]) was attenuated after adjustment for protein-bound CML plasma levels and other potential mediators (to β=0.202 [0.138;0.266]), with CML explaining the greatest portion of the attenuation (≈12%). Further analysis with dual-energy X-ray absorptiometry measures of body composition confirmed a strong inverse association of fat mass preferentially accumulated in the trunk with protein-bound CML plasma levels, significantly explaining ≈21% of the trunk fat-LGI association. Obesity, in particular central obesity, is characterized by greater levels of LGI but by lower levels of circulating CML; the latter significantly explaining a portion of the positive association between central obesity and inflammation.

Impact of Oxidative Stress Biomarkers and Carboxymethyllysine (an Advanced Glycation End Product) on Prostate Cancer: A Prospective Study

ObjectiveBiomarkers of oxidative stress and advanced glycation end products (AGE) have been linked to the development of prostate cancer, but evidence from human studies is scarce or controversial. MethodsWe conducted a prospective nested case-control study among 48 men (24 prostate cancer cases and 24 controls) aged 48 to 76 years at baseline. The participants of our study were a part of the Fernald Community Cohort. Prostate cancer cases and controls were matched individually on age (± 3 years) with a 1:1 ratio. Biomarkers included urine F2-isoprostanes (markers of lipid oxidation), plasma fluorescent oxidation products (markers of global oxidation), and carboxymethyllysine (CML) (a major end-stage AGE). ResultsAt baseline, cases had similar age, body mass index, proportion of family history of prostate cancer, history of benign prostatic hyperplasia, history of hypertension, history of diabetes, number of smokers, and plasma glucose levels compared with controls. Levels of plasma CML were significantly higher in cases than in controls (182 vs. 152 μg/mL, P < .05). In the conditional logistic regression model, an increase in CML equivalent to 1 standard deviation was associated with an increased risk of incident prostate cancer (relative risk, 1.79; 95% confidence interval, 1.00-3.21) and accounted for approximately 8% variance of prostate cancer liability. Urine F2-isoprostanes and plasma fluorescent oxidation products were not associated with prostate cancer incidence. ConclusionsHigher levels of plasma CML were associated with increased risk of prostate cancer. This suggests a potential new pathway for prostate cancer prediction and treatment.

Assessment of the concentrations of various advanced glycation end-products in beverages and foods that are commonly consumed in Japan.

Dietary consumption has recently been identified as a major environmental source of pro-inflammatory advanced glycation end-products (AGEs) in humans. It is disputed whether dietary AGEs represent a risk to human health. Nε-(carboxymethyl)lysine (CML), a representative AGE compound found in food, has been suggested to make a significant contribution to circulating CML levels. However, recent studies have found that the dietary intake of AGEs is not associated with plasma CML concentrations. We have shown that the serum levels of glyceraldehyde-derived AGEs (Glycer-AGEs), but not hemoglobin A1c, glucose-derived AGEs (Glu-AGEs), or CML, could be used as biomarkers for predicting the progression of atherosclerosis and future cardiovascular events. We also detected the production/accumulation of Glycer-AGEs in normal rats administered Glu-AGE-rich beverages. Therefore, we assessed the concentrations of various AGEs in a total of 1,650 beverages and foods that are commonly consumed in Japan. The concentrations of four kinds of AGEs (Glu-AGEs, fructose-derived AGEs (Fru-AGEs), CML, and Glycer-AGEs) were measured with competitive enzyme-linked immunosorbent assays involving immunoaffinity-purified specific antibodies. The results of the latter assays indicated that Glu-AGEs and Fru-AGEs (especially Glu-AGEs), but not CML or Glycer-AGEs, are present at appreciable levels in beverages and foods that are commonly consumed by Japanese. Glu-AGEs, Fru-AGEs, CML, and Glycer-AGEs exhibited concentrations of ≥85%, 2–12%, <3%, and trace amounts in the examined beverages and ≥82%, 5–15%, <3%, and trace amounts in the tested foods, respectively. The results of the present study indicate that some lactic acid bacteria beverages, carbonated drinks, sugar-sweetened fruit drinks, sports drinks, mixed fruit juices, confectionery (snacks), dried fruits, cakes, cereals, and prepared foods contain markedly higher Glu-AGE levels than other classes of beverages and foods. We provide useful data on the concentrations of various AGEs, especially Glu-AGEs, in commonly consumed beverages and foods.

The influence of disease and age on human cardiac stem cells

Recent studies have found that cardiac stem cells (CSCs) are present in the adult heart. CSCs play an important role in maintaining the balance of the number of myocardial cells. The purpose of this study was to examine characteristics of human CSCs and their correlation with clinical characteristics of patients. We collected heart auricles of 105 patients (age range, 1-78 years; mean, 55.6 ± 17.0 years) undergoing cardiac surgery to obtain CSCs. We assayed the percentage of c-kit positive (c-kit(+)) CSCs with flow cytometry. Plasma N(ɛ)-(carboxymethyl)lysine (CML) concentrations were measured by enzyme-linked immunosorbent assay. The percentage of c-kit(+) CSCs was 4.96 ± 3.12% (0.98-17.17%), and this was significantly negatively correlated with age, the presence of diabetes mellitus (DM) and coronary heart disease (CHD) (r values were -0.797 [P < 0.01], -0.500 [P < 0.01] and -0.250 [P = 0.011], respectively). The percentage of c-kit(+) CSCs was significantly negatively correlated with CML concentrations (r = -0.859, P < 0.01). The percentage of c-kit(+) CSCs decreases with ageing and is further decreased in patients with DM and/or CHD. Furthermore, plasma CML concentrations may have potential as an indicator of the number of c-kit(+) CSCs.

Effect of dietary advanced glycation end products on postprandial appetite, inflammation, and endothelial activation in healthy overweight individuals

Advanced glycation end products (AGEs) formed in food during high-heat cooking may induce overeating and inflammation. We investigated whether AGE contents in a single meal affect postprandial appetite and markers of inflammation, endothelial activation, and oxidative stress. In total, 19 healthy overweight individuals completed a crossover meal test with two meals of identical ingredients prepared by roasting (H-AGE) or steaming (L-AGE), respectively. Postprandial blood samples were analysed for N(ε)-carboxymethyl-lysine (CML), appetite-regulating gut hormones, glucose, insulin, triacylglycerol, and markers of inflammation and endothelial activation. Subjective appetite ratings and subsequent food intake were also assessed, and urine was analysed for CML, methylglyoxal-derived hydroimidazolone (MG-H1), and F2-isoprostanes. CML content of the H- and L-AGE meals was 5.0 and 2.8 mg, respectively. Plasma CML and urinary CML and MG-H1 tended to be higher after the H-AGE meal. There was no change in subsequent food intake, appetite sensations, or appetite hormone responses between meals, except for the overall ghrelin response, which was higher after the H-AGE meal compared with the L-AGE meal (p = 0.016). There was an increased glycaemic response to the H-AGE meal (p = 0.027) compared with the L-AGE meal. Inflammatory and endothelial activation markers did not differ between meals, but there was an overall effect on endothelial activation (p = 0.021) and on the oxidative marker, F2-isoprostanes, in urine (p = 0.013). The present study did not show any pronounced effects of AGEs on appetite and markers of inflammation, but did indicate that AGEs may affect postprandial ghrelin, oxidative stress, and glucose responses.

Plasma advanced glycation end-products and skin autofluorescence are increased in COPD

Chronic obstructive pulmonary disease (COPD) is associated with systemic inflammation and oxidative stress. These conditions may lead to the formation of advanced glycation end-products (AGEs). In this study we investigated in 88 COPD patients and 55 control subjects (80% ex-smokers) the association of the plasma protein-bound AGEs N(ε)-(carboxymethyl)lysine (CML), pentosidine, N(ε)-(carboxyethyl)lysine (CEL), and AGE accumulation in skin by skin autofluorescence (AFR), with lung function. Mean ± sd plasma CML was decreased (COPD 61.6 ± 15.6 nmol · mmol(-1) lysine, never-smokers 80.7 ± 19.8 nmol · mmol(-1) lysine and ex-smokers 82.9 ± 19.3 nmol · mmol(-1) lysine) and CEL (COPD 39.1 ± 10.9 nmol · mmol(-1) lysine, never-smokers 30.4 ± 5.0 nmol · mmol(-1) lysine and ex-smokers 27.7 ± 6.4 nmol · mmol(-1) lysine) and AFR (COPD 3.33 ± 0.67 arbitrary units (AU), never-smokers 2.24 ± 0.45 AU and ex-smokers 2.31 ± 0.47 AU) were increased in COPD patients compared to controls. Disease state was inversely associated with CML, and linearly associated with CEL and AFR. Performing regression analyses in the total group, CEL and AFR showed a negative association and CML a positive association with lung function, even after correction for potential confounders. In conclusion, CEL and AFR were negatively and CML was positively associated with disease state. In the total group only the AGEs showed an association with forced expiratory volume in 1 s. Our data suggest that AGEs are involved in the pathophysiology of COPD, although their exact role remains to be determined.