Direct evaluation of glycated and glyco-oxidized globins by matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) has been applied to achieve a qualitative and quantitative evaluation of gl ycated globins on a wide number of healthy and diabetic subjects. The metho d allowed us to establish that both alpha- and beta-globins are glycated an d that, in addition to simply glycated products, other species are detected . Investigations by different sample treatments and by analysis of the glyc ated beta-globin fraction obtained by preparative chromatography indicated that these species correspond to glyco-oxidized globins, Consequently MALDI -MS can be validly employed to evaluate not only the glycation level, but a lso the degree of oxidative stress. The percentages of glycated and glycoox idized species were calculated from the related MALDI spectra by the measur ement of the related peak areas, without any other treatment of data. A lin ear relationship between HbA(1c) values and the total percentage of glycate d and glyco-oxidized globins has been found, and its slope (<1) has been ra tionalized by the uncorrected evaluation of glycated globins content in the standard samples employed for HbA(1c), measurements. Copyright (C) 1999 Jo hn Wiley & Sons, Ltd.