Masatsuna Tasaka

Background/Objectives: Methylglyoxal-derived hydroimidazolone-1 (MG-H1), an advanced glycation end product, has implications in the pathogenesis of diabetic kidney disease (DKD). Although liquid chromatography-mass spectrometry is the current gold standard for quantifying MG-H1, its overall complexity limits its utility. We developed an ELISA to measure MG-H1 using a specific monoclonal antibody. Methods: Competitive ELISA was used to quantify total, high-molecular-weight (HMW), and low-molecular-weight (LMW) MG-H1 in serum. The assay's specificity was validated against structurally related compounds. Spike-and-recovery experiments were conducted to assess accuracy and precision. Serum samples from healthy controls, diabetic patients without kidney disease, and patients with DKD were analyzed (n = 10, 23, and 19, respectively). MG-H1's correlation with renal biomarkers and diagnostic performance was assessed using receiver operating characteristic analyses. Results: The ELISA exhibited preferential reactivity toward MG-H1 compared with structurally related compounds. Spike-and-recovery experiments resulted in recovery rates ranging 108-119%. MG-H1 levels were increased in patients with DKD, although the magnitude of the changes varied among the MG-H1 forms. All MG-H1 forms correlated positively with serum creatinine and blood urea nitrogen, and negatively with estimated glomerular filtration rate. No significant correlations were observed with glycoalbumin, and only a modest association was observed between LMW MG-H1 and HbA1c. Exploratory ROC analyses suggested that all MG-H1 forms could discriminate DKD from DM, with total and HMW MG-H1 showing performance comparable to that of conventional renal function markers. Conclusions: This competitive ELISA enables high-throughput quantification of MG-H1 in serum and demonstrates analytical feasibility; further multicenter validation is required before clinical implementation.

BACKGROUND: The accumulation of quinolinic acid (QUIN) in cerebrospinal fluid and serum may be used as a biomarker for various neuropsychiatric and inflammatory diseases. In this study, we developed a highly sensitive method to measure QUIN. METHODS: A reverse-phase high-performance liquid chromatography (HPLC) with fluorescence detection was established based on the enzymatic conversion of QUIN to nicotinic acid mononucleotide by recombinant quinolinic acid phosphoribosyltransferase, followed by the formation of fluorescent (BODIPY)-labeled deamido-NAD by recombinant nicotinic acid mononucleotide adenyltransferase. RESULTS: BODIPY-deamido-NAD was isocratically eluted within 6 minutes using reverse-phase chromatography and its chromatographic peak was resolved. The calibration range, precision, and analytical recovery of the QUIN assay are suitable for the analysis of biological fluids. Compared with published quantitation limits for QUIN measurement by HPLC, this method is at least 30-fold more sensitive and has a lower limit of detection of 5.0 nmol/L. The sensitivity was comparable to that previously reported for gas chromatography/mass spectrometry (GC/MS) and the quantitation results of QUIN from samples of cerebrospinal fluid correlated well with that of the GC/MS method. CONCLUSIONS: We established a novel method to quantify QUIN in biological samples. Due to its high sensitivity and the fact that it does not rely on MS instrumentation, this method has the potential for widespread adoption in research laboratories.