02849nas a2200181 4500008004100000245011200041210006900153260000800222520215600230100001602386700002002402700002902422700001402451700002102465700002502486700002502511856013102536 2019 eng d00aGlycation of glucose sensitive lysine residues K36, K438 and K549 of albumin is associated with prediabetes0 aGlycation of glucose sensitive lysine residues K36 K438 and K549 cAUG3 a

Prediabetes is a risk factor for the development of diabetes. Early diagnosis of prediabetes may prevent the onset and progression of diabetes and its associated complications. Therefore, this study aimed at the identification of novel markers for efficient prediction of prediabetes. In this pursuit, we have evaluated the ability of glycated peptides of albumin in predicting prediabetes. Glycated peptides of in vitro glycated albumin were characterized by data dependent acquisition and parallel reaction monitoring using LC-HRMS. Amongst 14 glycated peptides characterized in vitro, four peptides, particularly, FK(CML)DLGEENFK, K(AML)VPQVSTPTLVEVSR, K(CML)VPQVSTPTLVEVSR, and K(AML)QTALVELVK, corresponding to 3 glucose sensitive lysine residues K36, K438, and K549, respectively showed significantly higher abundance in prediabetes than control. Additionally, the abundance of three of these peptides, namely K(AML)QTALVELVK, K(CML)VPQVSTPTLVEVSR and FK(CML)DLGEENFK was >1.8-fold in prediabetes, which was significantly higher than the differences observed for FBG, PPG, and HbA1c. Further, the four glycated peptides showed a significant correlation with FBG, PPG, HbA1c, triglycerides, VLDL, and HDL. This study supports that glycated peptides of glucose sensitive lysine residues K36, K438 and K549 of albumin could be potentially useful markers for prediction of prediabetes. SIGNIFICANCE: Undiagnosed prediabetes may lead to diabetes and associated complications. This study reports targeted quantification of four glycated peptides particulary FK(CML)DLGEENFK, K(AML)VPQVSTPTLVEVSR, K(CML)VPQVSTPTLVEVSR, and K(AML)QTALVELVK, corresponding to 3 glucose sensitive lysine residues K36, K438 and K549 respectively by parallel reaction monitoring in healthy and prediabetic subjects. These peptides showed significantly higher abundance in prediabetes than healthy subjects, and showed significant correlation with various clinical parameters including FBG, PPG, HbA1c, and altered lipid profile. Therefore, together these four peptides constitute a panel of markers that can be useful for prediction of prediabetes.

1 aRathore, R.1 aSonwane, B., P.1 aJagadeeshaprasad, M., G.1 aKahar, S.1 aSanthakumari, B.1 aUnnikrishnan, A., G.1 aKulkarni, Mahesh, J. uhttp://library.ncl.res.in/content/glycation-glucose-sensitive-lysine-residues-k36-k438-and-k549-albumin-associated-prediabetes02147nas a2200193 4500008004100000245010200041210006900143260000900212300001200221490000700233520143900240100002701679700002301706700002401729700002501753700002701778700002501805856012301830 2020 eng d00aDevelopment of multiple reaction monitoring assay for quantification of carnosine in human plasma0 aDevelopment of multiple reaction monitoring assay for quantifica cJAN  a763-7690 v103 a

Carnosine, a histidine containing dipeptide, exerts beneficial effects by scavenging reactive carbonyl compounds (RCCs) that are implicated in pathogenesis of diabetes. However, the reduced carnosine levels may aggravate the severity of diabetes. The precise quantification of carnosine levels may serve as an indicator of pathophysiological state of diabetes. Therefore, we have developed a highly sensitive targeted multiple reaction monitoring (MRM) method for quantification of carnosine in human plasma samples. Various mass spectrometry parameters such as ionization of precursor, fragment abundance and stability, collision energy, tube lens offset voltage were optimized to develop a sensitive and robust assay. Using the optimized MRM assay, the lower limit of detection (LOD) and limit of quantification (LOQ) for carnosine were found to be 0.4 nM and 1.0 nM respectively. Standard curves were constructed ranging from 1.0 nM to 15.0 mu M and the levels of carnosine in mice and human plasma were determined. Further, the MRM assay was extended to study carnosine hydrolyzing activity of human carnosinases, the serum carnosinase (CN1) and the cytosolic carnosinase (CN2). CN1 showed three folds higher activity than CN2. The MRM assay developed in this study is highly sensitive and can be used for basal plasma carnosine quantification, which can be developed as a novel marker for scavenging of RCCs in diabetes.

1 aPandya, Vaibhav, Kumar1 aSonwane, Babasaheb1 aRathore, Rajeshwari1 aUnnikrishnan, A., G.1 aKumaran, Sangaralingam1 aKulkarni, Mahesh, J. uhttp://library.ncl.res.in/content/development-multiple-reaction-monitoring-assay-quantification-carnosine-human-plasma