Comparison of Plasma and Urine Biomarker Performance in Acute Kidney Injury.

BACKGROUND: New renal biomarkers measured in urine promise to increase specificity for risk stratification and early diagnosis of acute kidney injury (AKI) but concomitantly may be altered by urine concentration effects and chronic renal insufficiency. This study therefore directly compared the performance of AKI biomarkers in urine and plasma. METHODS: This single-center, prospective cohort study included 110 unselected adults undergoing cardiac surgery with cardiopulmonary bypass between 2009 and 2010. Plasma and/or urine concentrations of creatinine, cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), liver fatty acid-binding protein (L-FABP), kidney injury molecule 1 (KIM1), and albumin as well as 15 additional biomarkers in plasma and urine were measured during the perioperative period. The primary outcome was AKI defined by AKIN serum creatinine criteria within 72 hours after surgery. RESULTS: Biomarkers in plasma showed markedly better discriminative performance for preoperative risk stratification and early postoperative (within 24h after surgery) detection of AKI than urine biomarkers. Discriminative power of urine biomarkers improved when concentrations were normalized to urinary creatinine, but urine biomarkers had still lower AUC values than plasma biomarkers. Best diagnostic performance 4h after surgery had plasma NGAL (AUC 0.83), cystatin C (0.76), MIG (0.74), and L-FAPB (0.73). Combinations of multiple biomarkers did not improve their diagnostic power. Preoperative clinical scoring systems (EuroSCORE and Cleveland Clinic Foundation Score) predicted the risk for AKI (AUC 0.76 and 0.71) and were not inferior to biomarkers. Preexisting chronic kidney disease limited the diagnostic performance of both plasma and urine biomarkers. CONCLUSIONS: In our cohort plasma biomarkers had higher discriminative power for risk stratification and early diagnosis of AKI than urine biomarkers. For preoperative risk stratification of AKI clinical models showed similar discriminative performance to biomarkers. The discriminative performance of both plasma and urine biomarkers was reduced by preexisting chronic kidney disease.

Immunochemical crossreactivity of antibodies specific for "advanced glycation endproducts" with "advanced lipoxidation endproducts".

Antibodies against advanced glycation endproducts (AGEs) are used for their immunohistological localization in tissues, for example in Alzheimer's disease (AD) or diabetes. Many monoclonal and polyclonal antibodies have been used, and their specificity is unknown in most cases. Increased radical production, leading to the formation of lipid-derived reactive carbonyl species, such as malondialdehyde (MDA), acrolein, and glyoxal, is a characteristic aspect of age-related diseases like Alzheimer's disease or diabetic polyneuropathy. These reactive carbonyl species are able to modify proteins, resulting in AGE related structures, termed "advanced lipoxidation products" (ALEs). In this study, the monoclonal carboxymethyllysine-specific antibody 4G9 and the polyclonal AGE-antibody K2189 were tested for their immunoreactivity towards these carbonyl-derived protein modifications. To investigate which carbonyl-modified amino acid side chains are specifically recognized by these antibodies, peptide membranes were incubated with glyoxal, MDA and acrolein. As model proteins, microtubuli associated protein tau (MAP-tau), beta-amyloid, human serum albumin and chicken egg albumin were incubated likewise. It was found that both antibodies detected reaction products of these carbonyl compounds on lysine- and arginine residues and for the protein modification, it was found that some epitopes might not be detected. In conclusion, AGE-antibodies might not only detect sugar-derived AGEs but also structures derived from lipid peroxidation products (serving as markers of oxidative stress).

Age- and stage-dependent accumulation of advanced glycation end products in intracellular deposits in normal and Alzheimer's disease brains.

In this immunohistochemical study, the age- and stage-dependent accumulation of advanced glycation end-products (AGEs) in Alzheimer's disease (AD) and their relation to the formation of neurofibrillary tangles and neuronal cell death was investigated. For this purpose, the distribution of AGEs in neurons and glia was analyzed in the auditory association area of superior temporal gyrus (Brodmann area 22) of young and old non-demented controls and compared with early- and late-stage AD. A possible co-localization of AGEs with typical hallmarks of AD, such as hyperphosphorylated tau (as a marker for disturbed kinase/phosphatase activity), nNOS (as a marker for nitroxidative stress) and caspase-3 (as a marker of apoptotic cell death), was also investigated. Our results show that the percentage of AGE-positive neurons (and astroglia) increase both with age and, in AD patients, with the progression of the disease (Braak stages). Interestingly, nearly all if those neurons which show diffuse cytosolic AGE immunoreactivity also contain hyperphosphoryated tau, suggesting a link between AGE accumulation and the formation of early neurofibrillary tangles. Many, but not all, neurons show a co-localization of AGEs with other markers of neurodegeneration, such as nNOS and caspase-3.

Advanced glycation end-products in patients with chronic alcohol misuse.

AIMS: The aim of our study was to determine serum levels of advanced glycation end-products (AGE) in patients with chronic alcohol misuse and to examine their relationship to markers of nutrition and inflammation. METHODS: The study group consisted of 23 heavy alcohol drinkers treated for chronic alcohol misuse and 22 healthy controls. Studied parameters included AGE (fluorescence, CML - carboxymethyllysine and pentosidine), lipids, glucose, albumin, leptin, prealbumin, C-reactive protein (CRP) and pregnancy-associated plasma protein A (PAPP-A). RESULTS: AGE fluorescence was significantly higher in chronic alcoholic patients than in healthy subjects (4.3 +/- 0.7 x 10(3) vs 3.7 +/- 0.5 x 10(3) AU/g protein, P < 0.005), while CML was only slightly but not significantly elevated (569.1 +/- 106.6 vs 545.5 +/- 85.8 microg/l) and pentosidine levels did not differ (105.4 +/- 29 vs 102.2 +/- 23 nmol/l). In alcoholics, AGE correlate significantly negatively with leptin (r = -0.46, P < 0.05) and pentosidine with prealbumin (r = -0.43, P < 0.05), otherwise there was no relationship between AGE and other biochemical parameters (glucose, cholesterol, albumin, CRP, PAPP-A). CONCLUSION: Our findings suggest a more complex relationship among advanced glycation, oxidative stress and metabolism of ethanol and their link to nutrition and nutrition-associated parameters. AGE as a result of oxidative stress might be similarly linked to increased cardiovascular risk of heavy alcohol drinkers, as are malnutrition and inflammation; however, further studies are needed to confirm this hypothesis.

Improvement in quality of diabetes control and concentrations of AGE-products in patients with type 1 and insulin-treated type 2 diabetes mellitus studied over a period of 10 years (JEVIN).

Advanced glycation end (AGE)-products, a complex and heterogeneous group of compounds, have been implicated in diabetes-related long-term complications. Up to the present, only few data exist about serum levels of the AGE-proteins N- epsilon -carboxymethyllysine (CML) and pentosidine in selection-free populations of patients with type 1 and insulin-treated type 2 diabetes mellitus. In the present 10-year, population-based trial of patients with insulin-treated diabetes mellitus, serum CML and pentosidine levels were examined in correlation to the patients' quality of diabetes control and the prevalence of diabetes-related long-term complications. Jena's St. Vincent Trial (JEVIN) was started in 1989/1990. At this time, a centralised diabetes care system existed. After the baseline examination of 190 patients (83% of the target population) with insulin-treated diabetes mellitus, follow-up examinations were performed in 1994/1995 and 1999/2000. In 1994/1995, the CML concentration in patients with type 1/type 2 diabetes mellitus was 1096.47+/-405.50/1136.43+/-405.24 ng/ml. In 1999/2000, it was significantly lower (727.49+/-342.91 ng/ml, P=.033/743.76+/-312.47 ng/ml, P<.0001). The same tendency showed the AGE-protein pentosidine (type 1: 1994/1995 203.18+/-118.88 vs. 1999/2000 156.59+/-104.84 pmol/ml [P=.029], type 2: 1994/1995 189.72+/-67.66 vs. 1999/2000 151.54+/-127.73 pmol/ml [P=.020]). Parallel to the decrease in the mean concentration of the AGE-products CML and pentosidine mean HbA1c improved and the prevalence of diabetic long-term complications (retino-, neuro-, and nephropathy) remained comparable 1999/2000-1989/1990. Comparing the data of 1999/2000 with those from 1994/1995, there was not only a substantial improvement in patients' quality of diabetes control but also a decrease in the concentration of AGE-products. In patients with diabetes mellitus, the AGE-products seem to be mainly influenced by the quality of diabetes control. However, the most important parameter reflecting the risk for development and progression of diabetes-related long-term complications seems not to be the AGE-products, but patients' HbA1c.

Advanced glycation end products and receptor for advanced glycation end products in AA amyloidosis.

Advanced glycation end products (AGEs) may be involved in either amyloidogenesis or complications related to amyloid. We hypothesized that AGEs may influence the pathogenesis of AA amyloidosis, and investigated the spatial and temporal relationship between AGEs, carboxy methyl lysine (CML), the AGE receptor (RAGE), and AA amyloid in humans and mice. Specimens from patients with AL and ATTR amyloidosis served as a control. Using immunohistochemistry, AGEs, CML, and RAGE were found within amyloid deposits, more commonly in AA amyloid than in AL amyloid and not in ATTR amyloid. Western blotting showed that multiple proteins (between 12 and >60 kd) are modified, but not the AA amyloid fibril protein itself. In the murine model of AA amyloidosis, we found a marked interindividual variability with respect to local and systemic CML levels, as well as to splenic RAGE transcription. Serum levels of CML correlated with the duration of the inflammatory response but not with amounts of splenic RAGE mRNA. Other as yet unidentified variables, especially of the heterogeneous group of AGEs, probably modulate transcription of RAGE and influence amyloidogenesis. CML serum levels, in turn, may prove useful in predicting patients at risk.