The tryptic peptides of hemoglobin for diagnosis of type 2 diabetes mellitus using label-free and standard-free LC-ESI-DMRM

Assessment of liver enzymes as diagnostic biomarkers in type 2 diabetes mellitus: a cross-sectional study in Zakho, Iraq

BACKGROUND

This study aimed to identify the prevalence and factors associated with abnormal liver enzyme profiles in individuals with type 2 diabetes (T2D) in Zakho, to assess the association between demographic characteristics, clinical parameters, kidney function tests, lipid profiles, glucose levels, and T2D, and to identify resident risk factors.

RESEARCH DESIGN AND METHODS

A cross-sectional analysis of T2D patients admitted to Zakho General Hospital was conducted utilizing hospital records. The primary endpoint of interest was attaining HbA1C levels ≥ 6.5%. Analytical methodologies encompassed linear and multivariate logistic regression analyses, with due consideration of the association between diverse parameters and glycemic alterations. Further, the predictive value of biomarkers was evaluated through Receiver Operating Characteristic (ROC) curves and Area Under the Curve (AUC) analyses, complemented by Spearman correlation analysis to explore relationships among laboratory parameters.

RESULTS

The study found that 89.4% of participants had HbA1C levels above 6.5%, with a preference for T2D among older individuals (mean age: 52.93-49.89 respectively) and females. Age, glucose levels, and liver enzymes positively correlated with HbA1C.

CONCLUSIONS

The study emphasizes the diagnostic importance of liver enzymes in individuals with type 2 diabetes, suggesting that these biomarkers could be valuable indicators of disease severity and progression.

Tutorial review for peptide assays: An ounce of pre-analytics is worth a pound of cure

The recent increase in peptidomimetic-based medications and the growing interest in peptide hormones has brought new attention to the quantification of peptides for diagnostic purposes. Indeed, the circulating concentrations of peptide hormones in the blood provide a snapshot of the state of the body and could eventually lead to detecting a particular health condition. Although extremely useful, the quantification of such molecules, preferably by liquid chromatography coupled to mass spectrometry, might be quite tricky. First, peptides are subjected to hydrolysis, oxidation, and other post-translational modifications, and, most importantly, they are substrates of specific and nonspecific proteases in biological matrixes. All these events might continue after sampling, changing the peptide hormone concentrations. Second, because they include positively and negatively charged groups and hydrophilic and hydrophobic residues, they interact with their environment; these interactions might lead to a local change in the measured concentrations. A phenomenon such as nonspecific adsorption to lab glassware or materials has often a tremendous effect on the concentration and needs to be controlled with particular care. Finally, the circulating levels of peptides might be low (pico- or femtomolar range), increasing the impact of the aforementioned effects and inducing the need for highly sensitive instruments and well-optimized methods. Thus, despite the extreme diversity of these peptides and their matrixes, there is a common challenge for all the assays: the need to keep concentrations unchanged from sampling to analysis. While significant efforts are often placed on optimizing the analysis, few studies consider in depth the impact of pre-analytical steps on the results. By working through practical examples, this solution-oriented tutorial review addresses typical pre-analytical challenges encountered during the development of a peptide assay from the standpoint of a clinical laboratory. We provide tips and tricks to avoid pitfalls as well as strategies to guide all new developments. Our ultimate goal is to increase pre-analytical awareness to ensure that newly developed peptide assays produce robust and accurate results.

Discovery and validation of glucose-sensitive peptide biomarkers from human serum albumin to diagnose type 2 diabetes mellitus

Glycated albumin (GA), which represents the global glycation level of albumin, has emerged as a biomarker for diagnosing prediabetes and diabetes. In our previous study, we developed a peptide-based strategy and found three putative peptide biomarkers from the tryptic peptides of GA to diagnose type 2 diabetes mellitus (T2DM). However, the trypsin cleavage sites at the carboxyl side of lysine (K) and arginine (R) are consistent with the nonenzymatic glycation modification site residues, which considerably increases the number of missed cleavage sites and half-cleaved peptides. To solve this problem, the endoproteinase Glu-C was used to digest GA from human serum to screen putative peptides to diagnose T2DM. In the discovery phase, we found eighteen and fifteen glucose-sensitive peptides from purified albumin and human serum incubated with ¹³C glucose in vitro, respectively. In the validation phase, eight glucose-sensitive peptides were screened and validated in 72 clinical samples (28 healthy controls and 44 patients with diabetes) using label-free LC-ESI-MRM. Three putative sensitive peptides (VAHRFKDLGEE, FKPLVEEPQNLIKQNCE and NQDSISSKLKE) from albumin exhibited good specificity and sensitivity based on receiver operating characteristic analysis. In summary, three peptides were found as promising biomarkers for the diagnosis and assessment of T2DM based on mass spectrometry.

Modified Graphite Pencil Electrode Based on Graphene Oxide-Modified Fe3O4 for Ferrocene-Mediated Electrochemical Detection of Hemoglobin

This study describes the synthesis of graphene oxide-modified magnetite (rGO/Fe₃O₄) and its use as an electrochemical sensor for the quantitative detection of hemoglobin (Hb). rGO is characterized by a 2θ peak at 10.03° in its X-ray diffraction, 1353 and 1586 cm^-1 vibrations in Raman spectroscopy, while scanning electron microscopy coupled with energy-dispersive spectroscopy of rGO and rGO/Fe₃O₄ revealed the presence of microplate structures in both materials and high presence of iron in rGO/Fe₃O₄ with 50 wt %. The modified graphite pencil electrode, GPE/rGO/Fe₃O₄, is characterized using cyclic voltammetry. Higher electrochemical surface area is obtained when the GPE is modified with rGO/Fe₃O₄. Linear scan voltammetry is used to quantify Hb at the surface of the sensor using ferrocene (FC) as an electrochemical amplifier. Linear response for Hb is obtained in the 0.1-1.8 μM range with a regression coefficient of 0.995, a lower limit of detection of 0.090 μM, and a limit of quantitation of 0.28 μM. The sensor was free from interferents and successfully used to sense Hb in human urine. Due to the above-stated qualities, the GPE/rGO/Fe₃O₄ electrode could be a potential competitive sensor for trace quantities of Hb in physiological media.