Method for the analysis of n-glycans attached to immunoglobulin g from human blood plasma and its use

A method for calculating a Glycan Age Index (GAI) of an individual, comprising the following steps:

• (i) determining relative abundances of derivatized or underivatized released glycans attached to immunoglobulin G (IgG) or their corresponding IgG N-glycopeptides in a blood plasma sample from the individual using a method selected from the group consisting of ultra-performance liquid chromatography, MALDI-TOF mass spectrometry, liquid chromatography-mass spectrometry and capillary electrophoresis, wherein the glycans are F(6)A2B (GP6), F(6)A2G2 (GP14), and F(6)A2BG2 (GP15) having the following chemical structures:
• wherein:
• F(6)A2B (GP6):
• R1=GlcNAc;
• R2, R3, R4=H
• F(6)A2G2 (GP14):
• R1=H;
• R2, R3=Gal;
• R4=H
• F(6)A2BG2 (GP15):
• R1=GlcNAc;
• R2, R3=Gal;
• R4=H
• and
• GlcNAc=N-acetylglucosamine
• Fuc=fucose
• Man=mannose
• NeuAc=N-acetylneuraminic acid
• Gal=galactose
• wherein the mentioned IgG N-glycans are obtained by digesting the IgG with N-glycanase F, wherein the corresponding IgG N-glycopeptides are obtained by digesting the IgG with trypsin, wherein the relative abundance of each glycan or its corresponding IgG N-glycopeptide is obtained by normalization performed by dividing surface underneath the signal of the glycan or its corresponding IgG N-glycopeptides with total surface of all signals of glycans or corresponding IgG N-glycopeptides in the sample, wherein values <GP6>, <GP14>, and <GP15> represent the relative abundances of the glycans F(6)A2B (GP6) or its corresponding IgG N-glycopeptides, F(6)A2G2 (GP14) or its corresponding IgG N-glycopeptides, and F(6)A2BG2 (GP15) or its corresponding IgG N-glycopeptides for the individual, respectively;
• and
• (ii) calculating the Glycan Age Index (GAI), wherein the GAI is expressed in years and determined according to the following formulas in relation to the individual's sex:
• GAI(F)=75.4+135.3·<GP6>−63.3·<GP6>2−1.1·<GP14>+3.7·<GP15> for Female Sex;
• GAI(M)=80.2+79.6·<GP6>−25.1·<GP6>2−2.6·<GP14>+6.7·<GP15> for male sex (M).