Glycation refers to the reaction of amino groups, for example in proteins, with reducing sugars. Intermediately formed Amadori products can be degraded by oxidation (Maillard reactions) leading to a heterogeneous class of advanced glycation end-products (AGEs), especially during exposure to heat. AGEs are considered to be toxic in vivo due to their pronounced local and systemic inflammatory effects. At high temperatures, these reactions have been mostly investigated at the amino acid level. Here, we studied the formation of arginine-related AGEs in peptides under conditions simulating household cooking at physiological d-glucose concentrations. High quantities of AGE-modified peptides were produced within 15 min, especially glyoxal-derived products. The intermediately formed dihydroxy-imidazolidine yielded glyoxal- (Glarg) and methylglyoxal-derived hydro-imidazolinones (MG-H), with Glarg being further degraded to carboxymethyl-l-arginine (CMA). Carboxyethyl-l-arginine was not detected. The formation rates and yields were strongly increased in the presence of physiologically relevant concentrations of Fe(II)-ions and ascorbate. A nearby histidine residue increased the content of AGEs, whereas glutamic acid significantly reduced the CMA levels.

The presented approach enables the sensitive and robust quantification of prospective T2D biomarkers promising for clinical diagnostics.

FFA levels are elevated in newly diagnosed and long-term controlled T2DM patients, providing high diagnostic accuracy of 87% and 91%, respectively, which improved further when combined with the glycation degree of lysine-141 in haptoglobin. Additionally, FFA showed higher mean fold-changes than HbA1c or FPG in subjects developing T2DM, indicating higher sensitivity towards the progression of the disease.

BackgroundRecent epidemiological studies indicate that only 30–50% of undiagnosed type 2 diabetes mellitus (T2DM) patients are identified using glycated hemoglobin (HbA1c) and elevated fasting plasma glucose (FPG) levels. Thus, novel biomarkers for early diagnosis and prognosis are urgently needed for providing early and personalized treatment.MethodsHere, we studied the glycation degrees of 27 glycation sites representing nine plasma proteins in 48 newly diagnosed male T2DM patients and 48 non-diabetic men matched for age (range 35–65 years). Samples were digested with trypsin and enriched for glycated peptides using boronic acid affinity chromatography. Quantification relied on mass spectrometry (multiple reaction monitoring) using isotope-labelled peptides as internal standard.ResultsThe combination of glycated lysine-141 of haptoglobin (HP K141) and HbA1c provided a sensitivity of 94%, a specificity of 98%, and an accuracy of 96% to identify T2DM. A set of 15 features considering three glycation sites in human serum albumin, HP K141, and 11 routine laboratory measures of T2DM, metabolic syndrome, obesity, inflammation, and insulin resistance provided a sensitivity of 98%, a specificity of 100%, and an accuracy of 99% for newly diagnosed T2DM patients.ConclusionsOur studies demonstrated the great potential of glycation sites in plasma proteins providing an additional diagnostic tool for T2DM and elucidating that the combination of these sites with HbA1c and FPG could improve the diagnosis of T2DM.Electronic supplementary materialThe online version of this article (doi:10.1186/s12014-017-9145-1) contains supplementary material, which is available to authorized users.

A set of fluorophenoxyanilides, designed to be simplified analogues of previously reported ω-conotoxin GVIA mimetics, were prepared and tested for N-type calcium channel inhibition in a SH-SY5Y neuroblastoma FLIPR assay. N-type or Cav2.2 channel is a validated target for the treatment of refractory chronic pain. Despite being significantly less complex than the originally designed mimetics, up to a seven-fold improvement in activity was observed.

This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.

Current screening tests for type 2 diabetes mellitus (T2DM) identify less than 50% of undiagnosed T2DM patients and provide no information about how the disease will develop in prediabetic patients. Here, twenty-nine protein glycation sites were quantified after tryptic digestion of plasma samples at the peptide level using tandem mass spectrometry and isotope-labelled peptides as internal standard. The glycation degrees were determined in three groups, i.e., 48 patients with a duration of T2DM exceeding ten years, 48 non-diabetic individuals matched for gender, BMI, and age, and 20 prediabetic men. In long-term controlled diabetic patients, 27 glycated peptides were detected at significantly higher levels, providing moderate diagnostic accuracies (ACCs) from 61 to 79%, allowing a subgrouping of patients in three distinct clusters. Moreover, a feature set of one glycated peptides and six established clinical parameters provided an ACC of 95%. The same number of clusters was identified in prediabetic males (ACC of 95%) using a set of eight glycation sites (mostly from serum albumin). All patients present in one cluster showed progression of prediabetic state or advanced towards diabetes in the following five years. Overall, the studied glycation sites appear to be promising biomarkers for subgrouping prediabetic patients to estimate their risk for the development of T2DM.

Thymochinon wurde durch Wasserdampfdestillation aus gelbem Schwarzkümmelöl gewonnen und durch Säulenchromatographie gereinigt. Alle analytischen Spektren sind vollständig entweder im Hauptteil oder in der supporting information wiedergegeben. Die NMR‐ sowie die Massenspektren werden eingehend interpretiert und mit theoretischen Berechnungen der 13C‐chemischen Verschiebungen verglichen. Das Projekt stellt eine Fortsetzung des Buches “Classics in Spectroscopy” von S. Berger und D. Sicker (Wiley‐VCH 2009) dar.